Symposium Organizers
Sridhar Komarneni The Pennsylvania State University
Katsumi Kaneko Chiba University
John C. Parker Cabot Microelectronics Corporation
Paul O'Brien University of Manchester
HH1: Carbon Nanotubes and Polymer and Metals Nanoparticles
Session Chairs
Monday PM, November 26, 2007
Room 302 (Hynes)
9:30 AM - **HH1.1
Regularly Developed Nanopores in the Bundled Double Walled Carbon Nanotubes.
Morinobu Endo 1 , Takuya Hayashi 1 , Yoong Ahm Kim 1 , Hiroyuki Muramatsu 1 , Katsumi Kaneko 2
1 Faculty of Engineering, Shinshu University, Nagano Japan, 2 Department of Chemistry, Chiba Univeristy, Chiba Japan
Show AbstractPorous carbon materials have attracted many attentions because of their versatile applications in catalysis, sensors, electronic devices, gas or liquid separation and storage. Up to now, intensive and extensive studies have been carried out to find out effective routes to produce porous carbons in a controllable way (i.e., template method, polymer blends). However, there was no current synthetic technique for obtaining nanoporous carbons with homogeneous nanopores. Here, we will report very interesting nano-sized, homogeneous pores formed in the bundled double walled carbon nanotubes (DWNTs), which were successfully prepared by the catalytic chemical vapor deposition method and the subsequent oxidative purification process [1]. Specifically, we have found that our tubes consist of two relatively round, small and homogeneous-sized (below 2 nm in the outer shell) concentric tubules. Furthermore, these co-axial tubes are packed in a hexagonal array [2]. When considering their possible pores in the bundled DWNTs: (1) inner nanotube hollow cores; (2) inter-shell space (ca. 0.36 nm); (3) interstitial space located between adjacent tubes; usually nanotubes are packed in a hexagonal array (0.414 nm2), and (4) empty spaces located in between highly entangled long nanotube bundles. Among them, the interstitial spaces created along the tube length directions are proving to be a critical site for storing lithium ions and hydrogen molecules [3, 4]. The amount and also the size of these pores strongly depend on the tube diameter and length, the bundle size, the impurity content, the amount of functional groups, the degree of the physical entanglements. In detail, growth and structural characterization of high-purity and bundled DWNTs will be discussed with a strong emphasis on the formation and function of nanopores created within the bundle. References[1]A. Oberlin and M. Endo et al., J. Crys. Growth, 32, 335-349 (1976).[2]M. Endo et al., Nature, 433, 476 (2005). [3]M. Endo et al., Small 2, 667-676 (2006).[4]M. Endo and K. Kaneko et al., J. Am. Chem. Soc., 128, 12636-12637 (2006).
10:00 AM - HH1.2
Electronic Structural Control of Single Wall Carbon Nanotube With Molecular Tiling.
Suzana Gotovac 1 , Hiroaki Honda 1 , Yoshiyuki Hattori 1 , Cheol-Min Yang 1 , Kunimitsu Takahasi 2 , Hirofumi Kanoh 1 , Katsumi Kaneko 1
1 Chemistry, Graduate School of Science, Chiba University, Chiba Japan, 2 Laser Institute Center, Institute of Research and Innovation, Kashiwa Japan
Show Abstract10:15 AM - HH1.3
Macroporous 3D Architectures of Self-Assembled MWCNTs Surface Decorated with Pt Nanoparticles as Anodes for a Direct Methanol Fuel Cell.
Francisco delMonte 1 , Maria C. Gutierrez 1 , Maria J. Hortiguela 1 , Ricardo Jimenez 1 , J. Manuel Amarilla 1 , Maria L. Ferrer 1
1 Institute of Materials Science, Spanish Research Council, Madrid Spain
Show AbstractMicrochannelled 3D architectures composed of multiwall carbon nanotubes (MWCNTs) surface decorated with Pt nanoparticles and chitosan (CHI) are prepared by ice segregation induce self assembly (ISISA) process. The ISISA process consists on the unidirectional freezing (at -196 degrees C) of the hydrogel nanocomposites. Upon freezing, the ice formation (hexagonal form) causes every solute originally dispersed in the hydrogel to be segregated from the ice phase. After freeze-drying, the resulting hierarchical structures consists on well aligned micrometer-sized pores in the freezing direction corresponding to the empty areas where ice crystals originally resided, being the macrostructure supported by the matter accumulated between adjacent ice crystals. For high MWCNTs contents (89 wt. %), the resulting architectures are highly porous (specific gravity ~0.094) and extremely conductive (2.5 S/cm) thanks to the MWCNT interconnection at the macrostructure. These macroporous 3D architectures offer a high internal reactive surface of easy access through the broad “highways” provided by the microchanelled structure, which make them highly suitable for catalytic purposes. In particular, the Pt/MWCNTs(89)/CHI 3D architectures (prepared from Pt surface decorated MWCNTs) have allowed for a remarkable improvement (e.g., current densities of up to 242 mA/cm2) of the catalytic activity toward the methanol oxidation thanks to efficient fuel and product diffusion.
10:30 AM - HH1.4
Carbon Nanotube-Induced Chemical Etching of SiO2 Layer for Sub-10 nm Lithography and Its Mechanism Study.
Hye Ryung Byon 1 , Hee Cheul Choi 1
1 Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang Korea (the Republic of)
Show AbstractThe near future demands in the fabrication of miniaturized electronic devices require lithographic tools that can resolve sub-10 nm features. Here we introduce an unprecedented hybrid top-down lithography using nanomaterials, by which SiO2 layers are selectively etched at sub-10 nm scale via carbothermal reduction reaction (C(s) + SiO2 (s) ↔ SiO(g) + CO(g) at elevated temperature) between carbon nanotubes and SiO2/Si substrates. In contrast to the bulk carbothermal reduction, we have found that such a reaction between carbon nanotubes and SiO2 occurs only when small amounts of oxygen gas (0.1% of total gas amount) are introduced during the conventional chemical vapor deposition (CVD) process at 900 oC. Since carbothermal reduction occurs along carbon nanotubes, the trajectories of resulting SiO2 nanotrenches clearly mimic those of carbon nanotubes in terms of shape, length and width.1,2 SiO2 nanotrenches of sub-10 nm in width will open a great chance to fabricate various metal or semiconductor nanostructures at the corresponding size regimes, which have been difficult to be formed by traditional lithographic techniques. Among many possible nanostructures, we demonstrate here Cr nanowires having 4 or 8 nm diameter which are formed by a simple metal evaporation through SiO2 nanotrenches (as a mask).1,2
As for the mechanism of nanotrench formation, we have found that Fe nanoparticles (NPs) also play a critical role besides O2 gas. Most of all, no nanotrench was formed when Co catalyst NPs were used instead of Fe NPs although they successfully produced carbon nanotubes on SiO2 susbtrates. We further investigated nanotrenches formed at various reaction times and reaction gas ratios to understand the role of Fe NPs. Through the experiments, we observed three distinctive types of nanotrenches; 1) shallow and short nanotrenches, 2) nanotrenches made by aligned nanoholes, and 3) deep and straight nanotrenches. Depending on the role of Fe NPs, the type of nanotrenches seems to be determined.3
References
1.Byon, H. R.; Choi, H. C.
Nature Nanotechnology 2007,
2, 162.
2.See the extended abstract.
3.Manuscript in preparation, 2007.
11:15 AM - HH1.5
Preparation of Monodisperse Nanoparticles by Membrane Emulsification Using Anodic Porous Alumina.
Takashi Yanagishita 1 2 , Ryoko Fujimura 3 , Kazuyuki Nishio 3 2 , Hideki Masuda 3 2
1 , JST-PRESTO, Saitama Japan, 2 , Kanagawa Academy of Science and Technology, Kanagawa Japan, 3 , Tokyo Metropolitan Univ., Tokyo Japan
Show AbstractMembrane emulsification, in which emulsions are formed by passing liquid through a porous membrane, is one of promising technique for preparing monodisperse emulsion droplets [1]. In addition, the monodisperse solid particles can be obtained by solidifying the droplets. In this process, the size of emulsion droplets can be controlled by changing the size of the holes in the porous membrane. If the porous membrane with holes in the nanometer sizes is applied to the membrane emulsification, the nanometer-sized monodisperse emulsion droplets will be formed. However, there have been no reports on the preparation of monodisperse nanoemulsions because it is not easy to get the porous membrane with uniform-sized holes on the nanometer scales. In the present report, we describe the preparation of monodisperse elumsion droplets by membrane emulsification using ideally ordered anodic porous alumina, and its application to the fabrication of monodisperse nanoparticles by solidifying the doroplets. Anodic porous alumina, which is formed by anodization of Al in an acidic solution, is a promising porous material for the preparation of monodisperse emulsions by membrane emulsification because of its ordered fine structure with cylindrical holes of uniform diameter.[2,3] In the experiment, monodisperse emulsion droplets were prepared by membrane eulsificaiton using highly ordered anodic porous alumina. Monodisperse nanoparticles were also prepared by solidifying the droplets of sodium aluginate aqueous solution. The obtained monodisperse nanoparticles will be applied to several types of functional nanodevices. [1] T. Yanagishita et al., Langmuir, 20, 554 (2004). [2] H. Masuda et al., Science, 268, 1466 (1995). [3] H. Masuda et al., Appl. Phys. Lett., 71, 2770 (1997).
11:30 AM - HH1.6
Synthesis and Characterization of ``Janus" Particles with Au and Pt Faces.
Shengrong Ye 1 , R. Carroll 1
1 , West Virginia University, Morgantown, West Virginia, United States
Show Abstract Micro/nanoscale engines, catalytically driven without external forces, are some of the most interesting challenges facing nanotechnology. Indeed, this type of autonomous, non-Brownian movement has been described recently in electrodeposited dimer (Au/Pt) nanorods which act as catalytic nanomotors under the spontaneous decomposition of hydrogen peroxide in aqueous solution.
1 In this research, spherical individual “Janus” particles
2 (that is, particles having two different materials on opposite faces) were designed and successfully fabricated. These particles are composed of 1 um SiO
2 beads coated with Au and Pt films with thicknesses of ~100-200 nm. Well-packed films of 1 micron silica beads were deposited, on glass and subsequently coated with 5 nm titanium and 100-200 nm of gold. The beads were then adhered to a support, and inverted, followed by evaporation of a thin film of platinum (~100 nm). Finally, the beads were released from their support and re-suspended in solution. We will describe synthesis and characterization of these materials and will elaborate on efforts to study their autonomous motion in H
2O
2 aqueous solution, which is expected to exhibit significantly different trajectories than the previously described nanorods. Such a simple procedure with e-beam evaporation will also allow fabrication of Janus particles with incorporated magnetic cores or magnetic asymmetry, whose orientation of motion can be controlled in an applied magnetic field.
[1] W. F. Paxton, K. C. Kistler, C. C. Olmeda, A. Sen, S. K. S. Angelo, Y. Cao, T. E. Mallouk, P. E. Lammert and V. H. Crespi, J. Am. Chem. Soc. 2004, 126, 13424-13431; T. R. Kline, W. F. Paxton, T. E. Mallouk and A. Sen, Angew. Chem. Int. Ed. 2005, 44, 744-746; S. Fournier-Bidoz, A. C. Arsenault, I. Manners and G. A. Ozin, Chem. Commun. 2005, 441-443.
[2] V. N. Paunov and O. J. Cayre, Adv. Mater. 2004, 16, 788-791.
11:45 AM - HH1.7
Room Temperature Sintering of Ag Nanoparticle Paste and Its Mechanism.
Daisuke Wakuda 1 , Mariko Hatamura 1 , Katsuaki Suganuma 1
1 , The Institute of Scientific and Industrial Research Osaka University Suganuma Lab., Ibaraki, Osaka, Japan
Show AbstractRecently, the sintering temperature descent phenomenon of metallic nanoparticles has attracted a great deal of attention. From a practical point of view, the application of the phenomenon to the wiring of circuits combined with certain kinds of printing methods, such as ink-jet, has been studied. For excellent printability, suitable paste of metallic nanoparticles is required. Nanoparticles must be covered by organic dispersant to avoid aggregation and dispersed in solvent. Heating has always been required after printing metallic nanoparticles paste to remove the organic dispersant and solvent. In the case of the most promising Ag nanoparticle paste, heating beyond 150 οC is required to remove the dispersant. As a result, remaining active metallic nanoparticles can be successfully sintered and metallic circuits of excellent low resistivity can be obtained. However, heating temperature beyond 150 οC is too high both for many organic devices and for organic printed circuit boards, which are generally unstable beyond this temperature.In the current study, the authors developed a novel method that removes the dispersant from Ag nanoparticles without any heating or any specific atmosphere such as vacuum. Ag nanoparticles protected by dodecylamine as the dispersant were formulated into printable paste. First, the stability of Ag nanoparticles was examined. As a result, the Ag nanoparticle paste was found to be very stable for at least 150 days. In order to remove the dodecylamine dispersant, printed line of Ag nanoparticles on a glass substrate were dipped into methanol for 10 s to 7200 s. Microstructural observation revealed that, as dipping time increased, Ag nanoparticles agglomerated to be coarsened, and connection among particles became clearer. From the in-situ electrical resistance measurement, the electrical resistance of Ag nanoparticle printed lines drastically became lower. After 7200 s dipping, the removal of the dispersant became clear by surface analysis and the sintered lines possessed excellent low resistivity, 7.3×10-7Ωm. To understand the sintering mechanism, printed Ag nanoparticles lines on a glass substrate were dipped into various chemicals, such as ethanol and isopropanol. These chemicals were also found to have a capability of room temperature sintering. From electrical resistivity measurement, methanol had the highest potency for room temperature sintering among three chemicals and the next was ethanol. The order of the effect was equal to the order of dodecylamine solubility into the chemicals. Consequently, dodecylamine dispersant can be thought to dissolve into the treatment chemicals and active Ag nanoparticles can then be successfully sintered.Thus, a novel room temperature wiring method for Ag nanoparticles has been successfully developed in air atmosphere. The authors expect that the chemical method for sintering Ag nanoparticle pastes will become one of the standard methods for printed metallic nanoparticles’ wiring.
12:00 PM - HH1.8
Synthesis and Characterization of Ga and Au Nanoparticles/semiconductors Hybrid Systems.
Giuseppe Bianco 3 , Maria Giangregorio 1 , Pae Wu 2 , Maria Losurdo 1 , Tong-Ho Kim 2 , Pio Capezzuto 3 , April Brown 2 , Giovanni Bruno 1
3 Chemistry, University of Bari, Bari Italy, 1 Chemistry, IMIP-CNR, Bari Italy, 2 ECE, Duke University, Durham, North Carolina, United States
Show Abstract12:30 PM - HH1.10
A Multiscale First Principles Model for Predicting Energies of [100] Tilt Boundaries in Al-Pb Nano-alloys.
Y. Purohit 1 , D. Irving 1 , R. Scattergood 1 , D. Brenner 1
1 Materials Science and Engineering, NCSU, Raleigh, North Carolina, United States
Show AbstractIn a recent modeling study [1] that used a modified embedded atom method potential, the dispersion of lead (Pb) impurities to a Σ5 <100> {210} tilt aluminum (Al) grain boundary was predicted that produced a metastable Al nanostructure relative to an ideal dilute solid solution. Motivated by these findings, we have used a multiscale model that combines first principles total energies with a disclination - structural units model to characterize the energies of [100] symmetric Al tilt grain boundaries with different misorientation angles and varying concentrations of substitutional Pb impurities. These first principles results confirm the stability of Pb at grain boundaries compared to an ideal dilute solution as predicted by the empirical potential. Implications of these results for the structure and mechanical properties of Al-Pb nano-alloys will be discussed, in particular the tendency for forming Pb clusters versus dispersion of Pb at grain boundaries and the influence of these structures on plastic deformation mechanisms. This work was supported by the National Science Foundation through the NIRT program.[1] Atomistic Modeling of the Segregation of Lead Impurities to a Grain Boundary in an Aluminum Bi-crystalline Solid. Y. Purohit, S. Jang, D.L. Irving, C.W. Padgett, R.O. Scattergood and D.W. Brenner, Material Science and Engineering A, in press.
12:45 PM - HH1.11
Hybrid Metal-Semiconductor Nanocrystals as Novel Photocatalysts.
Ronny Costi 1 2 , Uri Banin 1 2
1 Department of Physical Chemistry, the Hebrew University of Jerusalem, Jerusalem Israel, 2 The Center for Nanoscience and Nanotechnology, the Hebrew University of Jerusalem, Jerusalem Israel
Show AbstractPhotoinduced charge separation has been studied extensively in different systems due to the potential in using these effects for photocatalysis, photochemical reactions and alternative energy production. Charge separation via light absorbance can be used to transform solar energy to a more available form of energy e.g. chemical energy. The ability to create a well defined nanometric structure with control over the charge separation should allows us the degrees of freedom in designing functional systems with light induced activity. Nanodumbbells (NDBs) are hybrid nanocrystals consisting of a semiconducting CdSe nanorod body with selectively grown gold tips. These metal tipped nano-structures provide a unique model for a metal-semiconductor interface on the nanometer scale. The metal-semiconductor nanometric interface introduces new electronic effects to the nano-structure, such as a light induced charge separation. We have studied light induced charging effects and charge separation using electrostatic force microscopy (EFM). We were able to determine that irradiation of NDBs causes a negative charging effect in single nanocrystals that is attributed to a charge separation between the metal and the semiconductor parts of the nanodumbbells. We have used spectroscopic studies to demonstrate the harnessing of the light-induced charge separation to a chemical reaction of reducing an organic dye. The direct photo-reduction of organic dyes using metal-semiconductor composites has been shown before; however, a high control over the shape and sizes of the composites was not shown until now. Also, we demonstrate a unique property of the metal-semiconductor nanodumbbells in which they retain their photo-induced charged state for long periods of time. This long lived charge separated entity allows us to reroute the trapped charge to a chemical reaction even after the illumination of the sample has ended.
HH2: Multi-energy/Field Processing of Nanomaterials
Session Chairs
Monday PM, November 26, 2007
Room 302 (Hynes)
2:30 PM - **HH2.1
Novel Epitaxial Structures in Nano- and Micro-composites Utilizing Multimode and Single Mode Microwave Processing.
Rustum Roy 1 , Dinesh Agrawal 1 , Jiping Cheng 1
1 Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractMicrowave processing is now recognized for many advantages including dramatic enhancements in reaction kinetics and extremely rapid sintering of metals, semiconductors and ceramics. Recently we have reported on new discoveries utilizing separated E and H fields at 2.45 GHz in a single mode cavity which have produced even more surprising phenomena such as solid state de-crystallization of the most technologically important phases containing unpaired d or f electrons. The present work reports on the utilization of such single mode processing to produce new composite structures of two phases – one with and one without unpaired spins. This results in a series of novel composites of glassy phases embedded in crystalline ones. These are compared with those treated in multimode fields, and conventional heating. Nanocomposites of B4C and SiC using carbon nano tubes as the seed material have been sintered with novel results in kinetics and densification. Other examples range from composites of crystalline Al2O3 and SiO2 with ferrites and doped Si, to two ferroics such as BaTiO 3-x with BaFe12O19 to illustrate the implications of this approach. A range of compositions has been studied to illustrate the phenomenon of solid state epitaxy.
3:00 PM - HH2.2
Diamond Nanowires in UNCD Films: The Transition Insulator-metal.
Raul Arenal 1 2 , Paola Bruno 2 , Dean Miller 2 , Dieter Gruen 2
1 , LEM, CNRS-ONERA, Chatillon France, 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Show Abstract3:15 PM - HH2.3
Highly Crystalline Nanoparticles from Microwave Thermal Plasmas; Experiment and Simulation of Particle Formation and Growth.
Hartmut Wiggers 1 , Klemens Hitzbleck 1 , Andreas Kowalik 1 , Christof Schulz 1
1 Institute for Combustion and Gasdynamics, Universitaet Duisburg-Essen, Duisburg Germany
Show AbstractThe formation of nanoparticles in gas-phase processes is a well established and industrially used technique. Nevertheless, there is a particular interest in new technologies transferring the advantages of flame processes such as high purity, high temperatures, high temperature gradients, and high production rate into new processes for the formation of non-oxidic nanoparticles. To this goal, a microwave supplied plasma in a flow reactor was used for the formation of small, nanosized and monocrystalline particles of silicon and iron by thermal decomposition of silane SiH4 and iron pentacarbonyl Fe(CO)5, respectively. The pressure in the reactor was adjusted between 10 and 200 mbar. The particle size and size-distribution were measured in-situ by means of a particle mass spectrometer (PMS) and ex-situ by X-ray diffraction and surface area analysis. Depending on the reaction conditions, mean particle diameters between 4 and 50 nm were observed. The influence of precursor concentration, flow rate and microwave power on the particle size were investigated. The process enables the formation of non-aggregated, crystalline particles in gram-scale with high purity and “tunable” particle size. Furthermore, the as-produced particles were investigated with respect to their optical and catalytic properties.In the modeling of this process, the microwave energy was treated as a spatially distributed energy source term, which results in an increase in the gas temperature. The particle formation and evolution were simulated using the sectional aerosol model introduced by Hounslow et al. In addition to the particle volume, the sectional model was also extended to the particle surface area. The model takes into account the thermal decomposition of the precursor, nucleation, coagulation, coalescence, convection, and diffusion effects. The simulations show very good agreement with the experiments, although the details of the plasma process were not considered. CFD calculations were carried out with Fluent 6.2.
3:30 PM - HH2.4
Controlling the Particle Size and Size Distribution of Lead Sulfide Nanocrystals using Polymers as Growth Limiters.
Daniel Asunskis 1 , Luke Hanley 1
1 Chemistry, University of Illinois at Chicago (UIC), Chicago, Illinois, United States
Show AbstractLead sulfide (PbS) is a group IV-VI semiconductor with a bulk band gap of 0.41 eV. PbS nanocrystals have size-tunable band gap, from the visible into the near-infrared region, and have potential as photovoltaics, photodiodes, nonlinear optical devices, and other applications. Composite materials of PbS nanocrystals in polymers have been synthesized, where the particles were grown directly in the presence of the polymer. The reaction involves the injection of a sulfur precursor to a degassed solution containing solvent, a lead precursor and a polymer. The polymer is the only species present to act as the size-limiting agent. These synthesized composites have a unique particle/polymer interface, free of surfactant capping groups that can greatly affect the properties of the composite. The use of a polymer to direct the growth of the nanocrystal represents a new pathway for nanocomposite material synthesis. Initial reactions with a hydrocarbon polymer, polyethylene (-CH2-CH2-)n, lead to the synthesis of large nanocrystals, 9±4 nm, which had an assortment of shapes. The large size distribution of the crystals in the composite is also a product of the polymer. The addition of side chains on the hydrocarbon, such as in poly(1-decene) (-CH(C8H17)-CH2-)n, lead to smaller nanocrystals, 5±3 nm, but a significant size distribution was still present. The smaller nanocrystal in the solution, <5 nm, have a spherical shape that begins to distort as the particles reach larger sizes. The use of a benzyl side chain, as in polystyrene (-CH2-CH(C6H5)-)n, gives the polymer different chain-to-chain interactions in the solution. The growth of the polymer in polystyrene lead to small, spherically shaped, 4±2 nm particles with a small size distribution. In all cases the growth of the nanoparticles to final size is quick, under three minutes, and unlike a surfactant-based synthesis the nanocrystals do not continue to grow as the reaction is under continuous heating. Large aggregates of the nanocrystal/polymer composite begin to form in solution and increase in number as the reaction is heated. This factor leads to the use of microwave radiation to facilitate further modification of the nanocrystals in the composite. The use of the microwave radiation has been shown to alter the crystal size and shape in the material and results of its use, as well as a microwave synthesis of the particles without external heating, will be discussed. After the sulfur precursor injection, UV-visible absorption and transmission electron microscopy (TEM) are used to monitor the changes in nanocrystal size as the reaction proceeds. Selected area electron diffraction, SAED, verified the crystallinity of the formed particles. These experiments show how the different polymers in the growth process lead to differences in particle size and size distribution and how microwave radiation can be used to alter the shape or size after the reaction, or facilitate the reaction on its own.
4:15 PM - HH2.5
Nanopatterning with a Handle – Magnetically Directed Strategies to Self-Organized Structures.
R. Lloyd Carroll 1 , Shengrong Ye 1
1 Chemistry, West Virginia University, Morgantown, West Virginia, United States
Show AbstractPattern formation on the nanoscale is a many faceted problem. Conventional lithographic approaches face optical limits that are difficult to overcome without high energy illumination and handling. E-beam lithography is a serial technique, suffering from excellence at only one scale, and difficult to scale up without prohibitively expensive instruments. Probe lithography and dip-pen lithography face the same problems. Self-assembly and organization of nanoscale structures has been proposed as a response to these limitations, but there are significant limits there as well. Self-assembled structures are rarely, arguably never, defect free. Defects in arrays and objects amplify variation to limit the range of self-organized behavior. These limitations combine to make high fidelity, long-range “self”-assembled systems a rarity. Much greater fidelity and control can be achieved by building handles into the system to facilitate driving the self-organizing system towards a low-energy minimum – low defect, long-range (10's to 100's of microns) nanoscale structures that can be used for more complex tasks.In this work, efforts to form such systems using magnetic composite materials and shaped magnetic fields as "handles" will be described. Self-organization of simple rod structures with nanoscale dimensions into oriented arrays using magnetic fields as a driver for a curable magnetic nanocomposite has been achieved and will be described. To achieve high fidelity uniformly patterned structures with arbitrary dimensions, we are exploring the use of nanosphere lithography and near-field phase-shift photolithography to produce complex patterns of magnetic islands. These islands distort applied uniform magnetic fields to direct the magnetic materials to specific locations and with well-defined spacing. Results of these experiments will be described. The application of these materials as a “lost wax” templating method to form microporous membranes with a patterned distribution of uniform pores will be described. Of particular interest is the mechanism of formation of the individual rods, the evolution of their structure under increasing fields, and the formation of long-range arrays of rods through the influence of shaped magnetic fields.
4:30 PM - HH2.6
Spontaneous and Guided Selfassembly of Clay Nanoparticles.
Jon Fossum 1
1 Department of Physics, Norwegian University of Science and Technology - NTNU, Trondheim Norway
Show AbstractIn the general context of self-assembly of nanoparticles, we have studied interconnected complex physical phenomena such as: (i) Spontaneous phase separation and nematic self-assembly in gravity of clay particles suspended in salt water [1,2].(ii) Transitions from biaxial to uniaxial nematics by application of external magnetic field in selfassembled systems of clay nanoparticle systems [3].(iii) Guided self-assembly into chainlike structures of clay nanoparticles suspended in oil subjected to external electrical fields (electrorheological structures of polarized nanoparticles), and then the stability of, such structures, when subjected to external mechanical stresses [4,5].The particles we have been studying in all cases (i) - (iii) are smectite clay platelet particles (fluorohectorite or laponite), and the experimental techniques include synchrotron X-ray scattering, neutron scattering, rheometry. microscopy and magnetic resonance. We have demonstrated that clays may be used as good model systems for studies of selfassembled nanostructured soft and complex matter. Self-assembly and related transitions in clay systems in particular, may have practical relevance for nano-patterning, properties of nanocomposites, and macroscopically anisotropic gels, among many other applications [6].Acknowledgments: Collaborators, postdocs and students at NTNU, UiO, IFE, BNL, LNLS, UFPE, UnB, GIST/PLS, Univ.Paris 7 and other places. This research has been supported by the Research Council of Norway (RCN), through the NANOMAT, SUP and FRINAT Programs. References:[1] J.O. Fossum, E. Gudding, D.d.M. Fonseca, Y. Meheust, E. DiMasi, T. Gog, C. Venkataraman, Observations of orientational ordering in aqueous suspensions of a nano-layered silicate, ENERGY The International Journal 30, 873 (2005) [2] D.d.M. Fonseca, Y. Méheust, J.O. Fossum, K.D. Knudsen, K.J. Måløy, K.P.S. Parmar, Phase behavior of platelet-shaped nanosilicate colloids in saline solutions: A small-angle X-ray scattering study, J. Appl. Cryst. 40, 292 (2007)[3] E.N. de Azevedo, M. Engelsberg, J.O. Fossum, R.E. de Souza, Anisotropic water diffusion in nematic self-assemblies of clay nano-platelets suspended in water, Langmuir 23, 5100 (2007)[4] J.O. Fossum, Y. Meheust, K.P.S. Parmar, K.D. Knudsen, K.J. Måløy, D.d.M. Fonseca, Intercalation-enhanced electric polarization and chain formation of nano-layered particles, Europhys. Lett., 74, 438 (2006), and in the Scientific Highlights 2006 of the European Synchrotron Radiation Facility - ESRF (2007)[5] K.P.S. Parmar, B. Schelderupsen, Y. Meheust, J.O. Fossum, Electrorheological suspensions of laponite in oil: rheometry studies under steady shear, submitted to Langmuir (2007) [6] F. Bergaya, B.K.G. Theng, G. Lagaly, editors, Handbook of Clay Science, Elsevier (2006)
4:45 PM - HH2.7
Effect of gamma-Irradiation Dose on Gold Prism Nanoparticle Formation by Radiolysis.
Tina Nenoff 1 , Kevin Leung 1 , Donald Berry 1 , Knapp James 1
1 , Sandia National Labs, Albuquerque, New Mexico, United States
Show AbstractWe report on the fundamental aspects of the growth of gold-based nanoparticles by solution radiolysis. Radiolysis of pure and mixed gold-metal solutions of Au, Ag, Pd, and Ni at different dose rates is examined. A detailed description will be presented of the experimentation, testing and complimentary modeling efforts (ab initio molecular dynamics). In particular, we will present data on the formation of gold prism nanoparticles versus gold-metal nanoparticles as determined by dose source, dose and dose rate on nanoparticle size, shape and phase integrity (alloy vs. core/shell). The progressive evolution with dose of the UV-visible absorption spectra of radiation-induced metal clusters is discussed and compared with those calculated by theory. The sources of radiolysis include Sandia GIF facility Co-60 source (approximately 75 rad/sec at source) and the pulsed proton irradiation using the external beam end-station on the SNL Tandem Van de Graff accelerator (approximately 4400 rad/sec). Nanoparticle characterization techniques include UV-vis, HRTEM, and analyzed by X-ray microanalysis and diffraction. The progressive evolution with dose of the UV-visible absorption spectra of radiation-induced metal clusters is discussed and compared with those calculated by theory. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
5:00 PM - HH2.8
Radiolytic Preparation of Poly(2-ethylhexyl acrylate-co-acrylic acid) Networks for Magnetic Nanocomposite Formation.
Alia Weaver 1 , Joseph Silverman 1 , Lourdes Salamanca-Riba 1 , Mohamad Al-Sheikhly 1
1 Materials Science & Engineering, University of Maryland, College Park, Maryland, United States
Show Abstract5:15 PM - HH2.9
Photocurrent Polarization Anisotropy of Randomly Oriented Nanowire Networks.
Yanghai Yu 1 , Vladimir Protasenko 2 , Aidong Lan 2 , Masaru Kuno 2 , Prashant Kamat 1 2 3
1 Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, United States, 2 Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States, 3 Radiation Laboratory, University of Notre Dame, Notre Dame, Indiana, United States
Show AbstractDue to one dimensional nature of semiconductor nanowires (NWs), the photo-generated density of electrons and holes strongly depends on the orientation of light polarization with respect to the NWs axis. This effect was already utilized by several groups in single NWs polarization sensitive photodector [CM. Lieber et al. Science 293, 2001: 24]. Similar phenomena has been also observed on DEP aligned CdSe and CdTe NWs [R. Zhou et. al. J. Appl. Phys. 2007, 101, 073704]. In this talk, we present the comprehensive study on our recently unexpected discovery that the arrays of randomly oriented NWs also exhibit the polarization sensitivity. We studied this phenomenon for CdSe and CdTe NWs randomly placed between Au electrodes separated by 30-110 μm wide gaps. Low and high resolution TEM images show that the wires are highly crystalline, thin (5-15 nm diameters), with the lengths exceeding 1 μm. Photocurrent anisotropy (ρ=(Imax-Imin)/(Imax+Imax)) varies with the distances from the electrodes, for example, for CdSe NWs ρ decreases from ~20% near the electrodes to 5-11% in the middle of the gap. In the meantime, the photocurrent maximum is measured in the middle of the gap, which we explain by the existence of hopping barrier between nanowires. In the end, we also explore the photocurrent anisotropy and photocurrent dependence on voltage, excitation wavelength, excitation power intensity and gap width. A simple model is built up and quantitatively explains the photocurrent anisotropy based on the dielectric constant mismatch, and electrons and holes hopping and transfer in the NWs networks. Our experiment demonstrates the possibility of building polarization sensitive devices based on randomly oriented NWs.
5:30 PM - HH2.10
Template Assisted Assembly of Nanofibers.
Ali Ashter 1
1 Department of Plastics Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States
Show Abstract5:45 PM - HH2.11
Mechanical Properties of Electrospun Polymer Nanofiber Network.
Zhenhai Xia 1 , Shing-Chung Wong 1
1 Department of Mechanical Engineering, University of Akron, Akron, Ohio, United States
Show AbstractHH3: Poster Session: Nanophase and Nanocomposite Materials
Session Chairs
Katsumi Kaneko
Sridhar Komarneni
Paul O'Brien
John Parker
Tuesday AM, November 27, 2007
Exhibition Hall D (Hynes)
9:00 PM - HH3.11
High Yield Synthesis of FCC Silver Nanoparticles and its Size Control.
Hiroyuki Nakamura 1 , Toshiyuki Shimizu 1 2 , Masato Uehara 1 , Yoshiko Yamaguchi 1 , Hideaki Maeda 1 2
1 , National Institute of Advanced Industrial Science and Technology (AIST), Tosu, Saga, Japan, 2 Deparment of Molecular and Material Sciences, Kyushu Uni., Kasuga, Fukuoka, Japan
Show AbstractNumerous of nanocrystal preparation methods have been reported, especially in the last two decades. However, there are not many reports that can control their particle size with maintaining a equilibrium yield; particle sizes are controlled by halting the reaction with an appropriate timing in many cases. Naturally in this case, the product yield is much lower for smaller particles, because particle volume is liner to the third power of diameter, and that can cause low yield of smaller size particles and wastes of energy and resources. On the other hand, there are some methods to obtain particle size control and high production yield at the same time, such as nucleation frequency control, and Ostwald ripening. However, nucleation process is still in black box and is often hard to control. Furthermore, Ostwald ripening of nanocrystals with narrow size distribution is usually avoided because the size distribution is usually widened by it. This is because the free energy of particles varies continuously with their size; smaller particles have larger free energy and have larger solubility, and vice versa for larger particles. However, to put it the other way around, if a clear energetic gap exists between the particles that dissolve and those that grow, that kind of ripening might be applicable without broadening the size distribution. Therefore, we utilized the energetic gap between multial twin particles(MTPs) and twin free fcc particles like silver. For example, when silver particle size is larger than critical size, fcc structure is calculated to be stable, although MTPs mainly exist as metastable in many cases. As experiment, the initial particles were prepared by a rapid heating of silver acetate dissolved in octadecene-oleylamine solution. The particle size was 3-4nm and product yield was nearly 100% at that stage. During ripening of the initial particles, we found disappearance of MTPs and selective growth of fcc nanoparticles, and finally it was possible to obtain 12 nm fcc silver NPs with a 13% of coefficient of variation (CV). Furthermore, particle size was able to be controlled from 8 nm to 17 nm by reaction temperature of the initial stage. Because the particle number at the initial stage did not vary much with the reaction temperature, it was suggested that the initial stage conditions affected fcc/MTP ratio, and thus it can control the final size of the fcc particles after ripening. Moreover, addition of MTPs to fcc silver NPs dispersion can control the final silver particle size after ripening following the same mechanism, and fine particle size control of nanoparticles are possible for 12 to 25 nm. Above all the case, the particle size distribution was narrow (CV<20% for all the case) and product yield was almost 100%, showing that the current ripening method can control particle size distribution well from 8 to 25nm.
9:00 PM - HH3.12
Controlled Nanoparticle Synthesis towards Various Properties and Applications.
Dongling Ma 1 3 , Teodor Veres 2 , Liviu Clime 2 , Francois Normandin 2 , Sophie Tan 4 3 , Zygmunt Jakubek 3 , Benoit Simard 3
1 Institut National de la Recherche Scientifique, EMT, Univeristy of Quebec, Varennes, Quebec, Canada, 3 Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario, Canada, 2 Industrial Materials Institute, National Research Council of Canada, Boucherville, Quebec, Canada, 4 Research & Development Center, Johnson & Johnson, Montreal, Quebec, Canada
Show AbstractSuperparamagnetic nanoparticles (NPs) and luminescent NPs have great potential for a wide range of applications and have attracted a great deal of interest. Herein, we present our work on the controlled synthesis of three types of useful NPs, dye-doped silica NPs, superparamagnetic-core/silica-shell NPs, and multifunctional NPs that integrate luminescence and superparamagnetism into a single nano-architecture. Their structure and properties have been thoroughly characterized. Several types of dyes, which have different molecular weights and are capable of forming different bondings with silica networks, have been exploited to form dye-doped silica NPs. The steady-state fluorescence polarization and lifetimes of these NPs are investigated and compared with those of free dye molecules. It is found that these dyes show quite different photophysical responses after being embedded in silica. This finding has been correlated to the effects of spatial hindrance and dye-silica interactions. We further examine the structural stability of the dye-doped silica NPs under “static” and “dynamic” conditions. By “static”, we mean the NPs are stored in a solvent for two weeks; by “dynamic”, we mean they have gone through multiple-step modification procedures. The structural stability is then probed from two aspects, the observable change of particle morphology and the percentage of leaching dye molecules during the evaluation process. Silica shells with a uniform thickness ranging from 10 to over 100 nm have been prepared on superparamagnetic iron oxide NPs. The temperature, frequency and field dependent magnetization behavior of the resulting core-shell NPs has been investigated [1]. Surprisingly, it is found that the mean blocking temperature and the effective anisotropy constant remain similar after the iron oxide NPs are coated with about 12 nm-thick silica shells from ZFC (zero field cooled magnetization) measurements and model fitting. However, the ZFC peak temperature and ZFC/FC (field cooled magnetization) branching point decrease significantly by over 100 K. To understand the above-interesting phenomena, the relative contribution from surface anisotropy and magnetic interparticle interactions to the blocking behavior is evaluated through in-depth study. For the multifunctional NPs, we have developed a new two-step approach to gain a better control over nanostructures than conventional Stöber or reverse microemulsion methods used independently. The novel hybrid NPs demonstrate marked advantages over the uncoated ones. Their magnetic and photophysical properties as well as their applications will be reported herein.References[1]. D. Ma, T. Veres, L. Clime, F. Normandin, J. Guan, D. Kingston, and B. Simard, J. Phys. Chem. C. 2007, 111, 1999-2007.[2]. D. Ma, Z. J. Jakubek, and B. Simard, J. Nanosci. Nanotechnol. 2006, 6, 3677–3684. [3]. D. Ma, J. Guan, F. Normandin, S. Dénommée, G. Enright, T. Veres, and B. Simard, Chem. Mater. 2006, 18, 1920-1927.
9:00 PM - HH3.13
Charge Distribution in Vanadium Oxide Nanotubes and Related Compounds Studied by Magnetic Properties and EPR.
Natasha Chernova 1 , Megan Roppolo 1 , Chris Jacobs 1 , Shailesh Upreti 1 , M. Stanley Whittingham 1
1 Institute for Materials Research, SUNY-Binghamton, Binghamton, New York, United States
Show AbstractVanadium oxide nanotubes (VONTs) are formed by scrolling of layered precursors containing long-chain amines between vanadium oxide layers upon hydrothermal treatment. The exact structure of vanadium oxide layers in VONTs is not known but is believed to be similar to that of BaV7O16. We have shown that upon variation of synthesis conditions such as pH and the amount of water, the morphology can be changed from scrolled nanotubes to nano-urchins, to non-scrolled nano-rods. The nano-urchins may be considered as an intermediate step between the tubes and the rods as the urchins presumably start to grow as fan-like arrangement of laminar precursor particles scrolling later to form radial arrays of nanotubes [1]. The use of ethylenediamine instead of long amines at low pH results in the formation of plate-like crystals of (enH2)V7O16. Powder x-ray diffraction patterns indicate same vanadium layer structure in all the compounds with interlayer distance depending upon the size of intercalated species. Chemical composition of the compounds can be generally expressed as VOx(amine)y.nH2O, where x varies from 2.3 to 2.5, y is usually 0.3-0.4 for mono-amines and half that amount for di-amines, and n is less than 1. The vanadium oxidation state varies from 4.2 to 4.5, while the distribution of V4+ and V5+ ions between three crystallographically different vanadium sites is not known. We have used magnetic properties and EPR spectroscopy to determine vanadium oxidation states and charge distribution in VONTs, nano-urchins, nanorods and (enH2)V7O16 with the aim to establish if the charge of the vanadium oxide layer has an effect on scrolling process and to determine the V4+/V5+ distribution in the compounds. We have found that all compounds contain paramagnetic V4+ ions and strongly magnetically coupled V4+ ions. The magnetic coupling can be described by the antiferromagnetic dimer model with exchange parameter of 650 to 700 K. The percentage of paramagnetic V4+ with respect to total V content is 17±3% in all the compounds, which is consistent with the amount of tetrahedral vanadium sites in BaV7O16 structure. The amount of V4+ ions in dimers increases in nano-urchins, nanorods and (enH2)V7O16 as compared to VONTs, indicating that vanadium reduction tends to delay or even prevent the scrolling of vanadium oxide layers. The red-ox and ion-exchange reactions of the compounds including oxidation in air, substitution of amines with Mn2+, and reaction with butyl lithium are also discussed. This work is supported by the National Science Foundation through grant DMR-0705657.[1] C. O'Dwyer et al., Chem. Mater. 2006, 18, 3016.
9:00 PM - HH3.14
Ceria Monodispersed Nanoparticles Fabricated by KrF Excimer Laser Irradiation and their Deposition Technique.
Masato Watanabe 1 3 , Hitoshi Takamura 1 , Hiroshi Sugai 2 , Naomi Takahashi 1
1 , Tohoku University, Sendai Japan, 3 , MHW Informatics Inc., Sendai Japan, 2 , 3R Corporation, Sendai Japan
Show AbstractCerium dioxide, Ceria, has been known to have diverse applications such as ultraviolet light absorbing material, polishing agent, catalyst and high oxygen conductivity leading to potential for electrolyte or electrode materials in SOFC. We have succeeded in preparation of monodispersed ceria nanoparticles less than 10nm by KrF excimer laser irradiation to cerium nitrate solutions in which dispersing agent such as a carboxylic acid was added. Yellow or brown colored suspensions were obtained after the laser irradiation. Subsequent redispersion of the nanoparticles in an organic solvent such as hexane resulted in transparent ceria colloid solutions. Conventional X-ray diffraction for the dried colloid solution shows wide-width diffraction peaks characteristic of fluorite structure of ceria. From dynamic light scattering, DLS, and the widths of X-ray diffraction peaks, average diameter of the nanoparticles was estimated to be in the range from 10nm to 1-2nm, depending on the source solution conditions. Visible and ultraviolet absorbance spectrum for the colloid solution shows absorbance in ultraviolet region less than ca. 400nm. We also investigated deposition technique for the nanoparticles in order to fabricate ceria nanoparticle monolayer or mutilayer thin films.
9:00 PM - HH3.15
Effect of Parametric Variations on Synthesis of Exotic Boron Carbide Nanowires.
Varun Gupta 1 , Giovanni Fanchini 1 , Steve Miller 1 , Jafar Al-Sharab 1 , Manish Chhowalla 1
1 Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States
Show AbstractSynthesis of one dimensional nano-materials and quasi-one dimensional nanostructures such as nanotubes, nanopipes and nanowires have gained a large impetus recently. Among the family of nanowires, boron carbide nanowires are particularly significant because of their potential use in thermoelectric devices and other electronic applications. In this study, we report a systematic study to synthesize BC nanostructures by varying the B to C ratio, temperature, pressure and presence of silicon. We report the synthesis of nanowires of boron carbide of 100-1000 μm in length and 10 nm to 1 μm in diameter at relatively low temperatures (1000 to 1250°C) through the use of a mixture of boron based eutectics (Ni2B, NiB etc.). In order to confirm the elemental composition, morphology and single crystalline nature of the nanowires, as synthesized structures were analyzed by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and ultrahigh resolution transmission electron microscope (HRTEM). The samples were further characterized by Raman spectroscopy and thermo-gravimetric analysis to estimate the amount of residual carbon and quantify the yield of nanowires. The variation of diameter with catalyst and silicon concentration is also evaluated. In addition, we ventured into the growth parameters necessary for the Si-doping of boron carbide nanowires which results in exotic structures ranging from nanowires and nanobelts to nano-cacti.
9:00 PM - HH3.16
Passivation of Nanophase Zirconium Hydride Via Surface Functionalization.
Albert Epshteyn 1 , Andrew Purdy 1
1 Chemistry Division, Code 6123, Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractAn array of potential surface ligands was examined for producing a well defined air and moisture stable nanophase zirconium hydride (Zr-H) material. The selected ligands included cyclopentadienes, alcohols, silanols, perfluorocarboxylic acids, and phosphonic acids, among others. The ligands were identified based on commercial availability, ease of synthesis and purification, or existence of precedent compounds of the ligand with Zr. Reactivity studies of nanophase Zr-H with these ligands were carried out under varied conditions elucidating the stability and reactivity of the nanophase Zr-H. The resultant product materials have been characterized using elemental analysis, XRD, NMR, SEM, EDAX and TEM to show that the nanophase Zr-H has been functionalized with the ligands. In each of the resultant materials the nanophase Zr-H has been found to have been passivated to varying degrees, as shown by its relative stability to air and moisture under a range of conditions.
9:00 PM - HH3.18
Aluminum Nanoparticle Synthesis by Reduction of Halides with Na/K.
Andrew Purdy 1 , Joel Miller 1 , Katherine Pettigrew 1
1 Chemistry Division, Code 6100, Naval Research Laboratory, Washington, District of Columbia, United States
Show AbstractSolutions or mixtures of aluminum halides AlX3 (X = Cl, Br, I) or organoaluminum halides (RAlX2 or R2AlX; R= i-Bu or Mes, X = Cl, Br) are prepared in heptane, toluene, ether, or pentamethyldiethylenetriamine (PMDETA) and treated with a slight excess of 50:50 (wt.) sodium potassium alloy (Na/K). Upon agitation, the reaction takes place slowly. The reaction appears to be limited by the deposition of insoluble products on the surface of the Na/K since sonication in an ordinary ultraonic cleaner is necessary to bring the reaction to completion in several hours. Aluminum nanoparticles and Na and K halides are formed, and soluble Al compounds, presumably clusters, are also formed in some cases. In an effort to passivate the surface of the Al particles to oxidation or hydrolysis, various agents are added either during the reaction or afterward. The products are characterized by SEM, XRD, NMR, elemental analysis, and TEM, and the stability to water and air is evaluated.
9:00 PM - HH3.19
Retargeting of Adenoviral Gene Delivery via Herceptin-PEG-Adenovirus Conjugates to Breast Cancer Cells.
Yukyung Jung 1 2 , Hyo-Jin Park 1 , Pyung-Hwan Kim 3 2 , Joo-Hyuk Sohn 3 , Joo-Hang Kim 3 2 , Chae-Ok Yun 3 2 , Seungjoo Haam 1 2
1 Chemical Engineering, Yonsei University , Seoul Korea (the Republic of), 2 Graduate Program for Nanomedical Science, Yonsei University , Seoul Korea (the Republic of), 3 Yonsei Cancer Center, College of Medicine, Yonsei University, Seoul Korea (the Republic of)
Show Abstract PEGylation of adenovirus vector (ADV) is an attractive strategy in gene therapy. Many types of PEGylated ADV(PEG-ADV), which diminish protein-protein interactions and prolong circulation time in the blood stream, have been developed. However, PEG-ADV still relies on the transduction on a nonspecific site via a CAR-mediated viral infection mechanism. Hence, PEGylation has resulted in limited binding and internalization of ADV with consequently inefficient gene delivery to objective cells. Moreover, PEG-ADV showed significantly lower expression level than ADV. To resolve this problem, we synthesized the Herceptin-PEG-Adenovirus conjugates for retargeting gene therapy to breast cancer cells. Herceptin® (Trastuzumab, HER), a humanized recombinant anti-HER2/neu MAb, can specifically bind to the membrane region of HER2/neu with a high affinity, inhibiting signal transduction and cell proliferation. HER2/neu (human epidermal growth factor receptor 2) is over-expressed in 25-30% of invasive breast cancers, and its expression is similar in primary tumors and corresponding metastasis. Thus, anti-HER2/neu monoclonal antibody (MAb) is of interest as a potential targeting moiety of viral vector to breast cancer cell. In this study, HER was conjugated to the one terminal group of hetero-bifunctional PEG molecule conjugated on the surface of Adenovirus containing GFP genes to grant HER2/neu over-expressed breast cancer cells specific targeting. Enhancement in specificity and efficacy was comparatively evaluated as the extent of cell-specific GFP transduction using HER2/neu over-expressing MDA-MB-435 cells, medium-expressing MDA-MB-468 cells and HER2/neu deficient U251N cells for retargeting strategies. Morphology, size and conjugation efficiency of prepared HER-PEG-ADV were characterized by Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), Zeta Potential and Fast Performance Liquid Chromatography (FPLC), respectively. Moreover, the site-specific targeting characteristics of prepared HER-PEG-ADV were confirmed by Fluorescence Activated Cell Sorting (FACS). PEGylated ADV significantly reduced innate immune response likewise, as judged from the amount of interleukin 6 released from macrophage cells. Consequently, HER-PEG-ADV conjugate vectors were found to be feasible to overcome the limitation factor associated with immune response and targeting for adenoviral gene delivery. HER-PEG-ADV were capable of enhancing transduction efficiency onto the breast cancer cells via HER2/neu as a targeting moiety and also enveloping of PEG on the surface of ADV reducing the extent of immune response. This study may render target specific gene delivery using adenoviral vectors for many clinical applications. Further study on the synergistic efficacy of therapeutic antibody and gene therapy via HER-PEG-ADV for the breast cancer treatment in vivo level is prospected.
9:00 PM - HH3.2
Topochemical Synthesis and Delamination of Transition MetalConstituting Layered Double Hydroxide.
Renzhi Ma 1 , Kazunori Takada 1 , Nobuo Iyi 1 , Yoshio Bando 1 , Takayoshi Sasaki 1
1 Nanoscale Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Show Abstract9:00 PM - HH3.20
Phase Formation and Stability Boundaries in Nanophase Zirconia.
Masaru Tsuchiya 1 , Shriram Ramanathan 1
1 School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show AbstractAmong the class of fluorite oxides, zirconia is a particularly important material with its tremendous potential for technological applications, including advanced nanoelectronic devices and electrolyte membrane for hydrogen energy conversion devices. The microstructure of zirconia controls many of its important material properties, including oxygen ionic conductivity and mechanical properties. While there have been a surge in interest towards the application of thin film zirconia, little information is available for thin film systems. In this presentation, we report our systematic studies on the size dependence of phase transformations in pure and Y-doped thin film zirconia synthesized by electron-beam evaporation. Pure and 9.5 % Yttria-doped zirconia films of 10 – 400 nm were grown at room temperature on various substrates including Ge, Si, and Silicon Nitride. Samples were annealed both in-situ inside the TEM using a heating holder and also ex-situ and the resulting structures were studied. We found the phase stability in nanoscale thin films is markedly different from that observed in the bulk. In bulk zirconia, monoclinic phase is stable at room temperature, which undergoes monoclinic-to-tetragonal, then tetragonal-to-cubic transformation at 1443K and 2643 K, respectively. However, unlike bulk crystals, high temperature cubic phase can be stabilized at room temperature in the 52 nm thin pure zirconia film. The film underwent a cubic-tetragonal phase transformation when heated from room temperature to about 673 K. The as-grown structure was nanocrystalline with 10-15 nm and grew to 70-80 nm at around 1000 K with no significant abnormal grain growth. This transformation is likely originated from the decrease in oxygen vacancy concentration due to the decrease in grain boundary area where it contains a large amount of oxygen vacancies. We will show our results on phase changes due to the annealing ambient and synthesis, and discuss in detail how oxygen vacancies play a role in phase stability. Interestingly, the microstructure evolution in Yttria doped Zirconia (YDZ) was quite different from that in undoped. The as-grown phase in the YDZ films thicker than 50 nm was cubic polycrystalline with 10-20 nm grains that undergoes nearly instantaneous grain growth around 823 K. It is interesting to note that cubic phase was stable in YDZ films even after the growth. In addition, the film thickness plays an important role to determine the microphase stability in thin films. The ultrathin films, 20 nm or less, can be amorphous up to more than 1000 K. Detailed discussion on the control of microstructure and phase stability in nanophase zirconia will be given in this presentation. The effect of thickness, substrate, and point defect modulation by synthesis and dopant concentration will be discussed with particular emphasis. Where available, the experimental results will be compared to thermodynamic predictions including nano-size effects.
9:00 PM - HH3.21
Electrostatic Self Assembly of Nanoparticles Without Polyelectrolytes: Electrical Bistability and Memory Phenomenon.
Satyajit Sahu 1 , Sudip Batabyal 2 , Amlan Pal 1
1 Solid State Physics, Indian Association for the Cultivation of Science, Kolkata, West Bengal, India, 2 Department of Chemistry, National University of Singapore, Singapore Singapore
Show Abstract9:00 PM - HH3.23
Synthesis of Corundum Nanocrystals.
Georgy Panasyuk 1
1 , Institute of General and Inorganic Chemistry, Moscow Russian Federation
Show Abstract9:00 PM - HH3.24
Electronic Properties of Au Nano-particles Supported on NiO(001) and (111) Substrates.
Tetsuaki Okazawa 1 , Akinobu Iwamoto 2 , Yasumasa Kitsudo 2 , Masanori Kohyama 1 , Yoshiaki Kido 2
1 , Material Science Research Group Research Institute for Ubiquitous Energy Devices National Institute of Advanced Industrial Science and Technology, Ikeda Japan, 2 Physics, Ritsumeikan University, Kusatsu Japan
Show AbstractGold is known as the most inert metal, but it shows high activity as a catalyst for the cluster size smaller than 5 nm. There are a lot of reports on the grow modes and electronic properties of Au nano-clusters on metal oxides. In particular, Au on TiO2 has been investigated mainly by using high-resolution transmission electron microscope (HRTEM) and the first principles calculations. In this paper, we present the growth mode and electronic properties of Au nano-clusters on nonpolar NiO(001) and polar NiO(111) surfaces, which were analyzed in-situ by medium energy ion scattering(MEIS) and photoelectron spectroscopy (PES).The clean NiO(001) surface was prepared by cleavage in the air and annealing at 770K in O2-pressure of 1×10–4 Torr for 40 min. We formed the clean NiO(1111) surface by oxidization a single crystal Ni(111) at room temperature(RT). The oxide surface grown epitaxially takes a precursor state of the octopolar structure terminated with 0.25ML Ni atoms. Au was deposited by molecular beam epitaxy (MBE) on the clean surfaces.Initially two-dimensional (2D) islands with thickness of one Au atomic layer grow epitaxially on NiO(001) and then neighboring 2D-islands link each other to form three-dimensional (3D) islands with the c-axis oriented to the [111] direction. In contrast, Au clusters start to grow in a poly-crystal phase on NiO(111).We observed Au 4f spectra and found no binding energy shift for Au/NiO(001) but significant higher binding energy shifts for Au/NiO(111) indicating an electron charge transfer from Au to NiO(111). The work function of Au/NiO(111) decreases with increase in Au coverage. The reduction of the work function is consistent with the higher binding energy shift of Au 4f resulted from electron charge transfer indicating an interface dipole.
9:00 PM - HH3.25
Atomic Structure of PtRu Nanoparticle Catalysts and Their Methanol Oxidation Activity.
Hiroaki Nitani 1 , Yusuke Honda 1 , Ryo Horioka 1 , Kosuke Ohara 1 , Takuya Kawaguchi 1 , Takashi Nakagawa 2 , Satoshi Seino 1 , Takao Yamamoto 1 , Hideo Daimon 3
1 Graduate School of Engineering, Osaka University, Suita city, Osaka, Japan, 2 Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan, 3 Development & Technology Division, Hitachi Maxell Ltd., Tsukubamirai city, Ibaraki, Japan
Show AbstractDirect methanol fuel cell (DMFC) is one of the most promising next generation’s power sources for mobile electric devices. A key issue for commercialization of DMFC is improvement of methanol oxidation activity in anode catalyst. The anode PtRu catalyst is well known to have a high CO tolerance explained by the bi-functional mechanism. This mechanism postulates that, Ru atoms at surface in close vicinity to Pt atoms work as assistant catalyst. Therefore, we need information on atomic level structure of the PtRu catalyst, and some tuning of the catalyst structure is desired for improvement of the methanol oxidation activity. In this paper, we report on analysis of the atomic level structure of PtRu catalyst by the EXAFS technique, and on a clear correlation found between the atomic structure and the catalytic activity. These results support the bi-functional mechanism.An aqueous solution containing H2PtCl6, RuCl3 and carbon support was irradiated with gamma-rays or by an electron beam to form and stabilize PtRu nanoparticles on the carbon support. Methanol oxidation activity of the PtRu catalyst was measured by the linear sweep voltammetry (LSV) in an aqueous solution containing H2SO4 and methanol. Pt-LIII edge and Ru-K edge EXAFS spectra of the PtRu catalysts were obtained by using synchrotron radiation. Composition, crystallographic structure and morphology of the PtRu catalysts were examined by ICP-AES, XRD and TEM, respectively. The electron beam or the gamma-rays was performed to the same total dose, but does rate of the former electron was far higher than that of the latter. Since Pt ion has a higher standard reduction potential than that of Ru ion, Pt ions are expected to be first reduced resulting in a Pt-rich-core/Ru-rich-shell structure in PtRu catalyst. The XRD patterns indicated a random alloy structure occurs by the electron beam, while a core/shell structure by the gamma rays. These results mean that the high dose rate irradiation could remove the hierarchy of the reduction potential. The LSV measurements showed that PtRu catalyst by the electron beam is more active than by the gamma rays irradiation. These facts are consistent with the bi-functional mechanism which attributes the activity to occurrence of Pt-Ru atomic pair. In order to extract quantitative information on the Pt-Ru atomic pair, we introduced paring factor, PRu=NRu-Pt/(NRu-Pt+NRu-Ru), using coordination numbers evaluated by the EXAFS analysis. The PRu increases with occurrence frequency of the Pt-Ru atomic pairs. It was found that PtRu catalysts synthesized by the electron beam irradiation have relatively higher PRu, and that the higher the pairing factor is, the higher activity was observed.
9:00 PM - HH3.26
Shear and Confinement-induced Formation of Nanostructures from Surfactant-coated Nanowires.
Younjin Min 1 , Mustafa Akbulut 2 , Yuval Golan 3 , Joe Zasadzinski 1 , Jacob Israelachvili 1
1 Chemical Engineering, UCSB, Santa Barbara, California, United States, 2 Chemical Engineering, Princeton University, Princeton, New Jersey, United States, 3 Department of Materials Engineering, and Ilse Kats Center of Nanotechnology, Ben-Gurion University of the Negev, Beer-Sheva Israel
Show AbstractWe studied the effect of curvature on the dynamics of confinement and shear of surfactant-coated ZnS nanowires. Both dynamics of the confinement (normal forces) and shear (lateral forces) were found to be very sensitive to the particles’ curvature: (i) straight wires can better order or align during shearing than curved ones; (ii) none of the wire assemblies caused adhesion of the surfaces; the forces were always purely repulsive, which we denote by ‘steric’; (iii) under compression, curved nanoparticles have a longer-ranged steric repulsion (thicker ‘hard-wall’ layer) than straight nanowires, (iv) the normal compression-decompression or loading-unloading force profiles are mostly reversible for straight wires and irreversible for curved wires; (v) the friction forces across curved and straight wires are similar at low loads or pressures (P < 1 MPa) but larger for the curved wires at high loads (P > 2 MPa). The understanding gained by these studies will shed light into how the nanoparticles order between the two confining and/or shearing surfaces, and consequently, provide an insight in the design of thin-film processing methodologies.
9:00 PM - HH3.27
Electronic and Magnetic Characterization of in vivo Produced vs. in vitro Reconstituted Horse Spleen Ferritin.
Georgia Papaefthymiou 1 2 , Arthur Viescas 1 , Eamonn Devlin 2 , Athanassios Simopoulos 2
1 Physics, Villanova University, Villanova, Pennsylvania, United States, 2 Institute of Materials Science, NCSR Demokritos, Aghia Paraskevi Greece
Show AbstractMagnetic nanophases nucleated within apoferritin nanotemplates under in vivo physiological conditions and in vitro reconstitution were characterized by Mössbauer spectroscopy in freeze-dried form. To obtain reasonable χ2-values the spectra had to be fitted with the superposition of two inequivalent iron sites associated with surface vs. interior iron atoms for both samples. Mössbauer spectra recorded at 80 K indicate that for the in vivo produced ferritin the presence of phosphates within the ferritin biomineral core results in larger quadrupole splittings, both at interior and surface sites, 0.62 and 1.06 mm/s, respectively; as compared to 0.56 and 0.75 mm/s for the reconstituted ferritin. Data collected at lower temperatures give blocking temperatures (TB) of 40 and 55 K for in vivo and in vitro samples, respectively. The TB = 40 K is in accord with published data for in vivo produced horse spleen ferritin, expected to be fully loaded at ~4,500 Fe atoms per protein shell. The higher TB = 55 K observed for the in vitro reconstituted sample, which was loaded to only ~1,500 Fe atoms per protein shell, points to a magnetic anisotropy constant four-fold stronger compared to the in vivo ferritin sample. At 4.2 K, both samples give similar hyperfine field values for the interior (Hhf ~495 kOe) and surface (Hhf ~450 kOe) iron sites. Observed differences in dynamic spin fluctuations, in the temperature range of 4.2 K < T < 80 K, will be discussed in terms of superparamagnetic relaxation processes and collective magnetic excitations. In addition, Mössbauer spectra of in vivo horse spleen ferritin in frozen solution form will be presented in order to assess any structural difference that might be induced in the process of freeze-drying.
9:00 PM - HH3.28
Synthesis and Characterization of Alkaline-Earth Metal Hexaboride One-Dimensional (1D) Nanostructures.
Syed Amin 1 , Shuyou Li 2 , John Roth 3 , Terry Xu 1
1 Department of Mechanical Engineering & Engineering Science, The University of North Carolina at Charlotte, Charlotte, North Carolina, United States, 2 NUANCE Center, Northwestern University, Evanston, Illinois, United States, 3 Research Resource Center, The University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractBoron-based (i.e., boron and metal boride) one-dimensional (1D) nanostructures have recently attracted much attention due to their predicted superior electrical and mechanical properties. Combining with other properties such as low density and high chemical stability, boron-based 1D nanostructures have potential applications in nanoelectronics, in nanocomposites where they may impart stiffness, toughness and strength. In this presentation, we report our recent progress on synthesis and characterization of alkaline-earth metal hexaboride (MB6, M=Sr, Ba) 1D nanostructures. Catalyst-assisted growth of MB6 1D nanostructures was achieved by pyrolysis of diborane (B2H6) over alkaline-earth metal oxide (MO) or alkaline-earth metal carbonate (MCO3) powders at elevated temperature (~890-960 ○C) and low pressure (~165 mTorr). Nickel (Ni), gold (Au) and palladium (Pd) are effective catalytic materials. The as-synthesized MB6 1D nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Results show that the MB6 nanostructures are single crystalline with preferred growth direction along [001]. The SrB6 nanowires are ~30-100 nm in diameter and ~1-10 μm in length. The BaB6 nanostructures have a rectangular cross section (width ~50-200nm) and are ~5-20μm in length. The growth of these nanostructures involved both vapor-liquid-solid and vapor-solid growth mechanisms. The MB6 1D nanostructures will find potential applications in nanocomposites, thermoelectric energy conversion, nanoelectronics and others.
9:00 PM - HH3.29
The Chemistry of Dihalopropanes in Faujasite NaX Zeolite at Room Temperature.
Charles Kanyi 1 , David Doetschman 1
1 Chemistry, Binghamton University, Binghamton, New York, United States
Show AbstractThe room temperature chemistry of dihalopropanes in Faujasite NaX zeolite is largely dependent on the nature of the halogen and the relative positions of the halogens. All the diiodopropanes studied undergo nucleophilic substitution to form framework iodopropoxy. Vicinal dihalides 1,1-dichloropropane and 2,2-dichloropropane react selectively via elimination to form 1-chloropropene (80% trans) and 2-chloropropene, respectively. The presence of the bulky chloro group on the positively charged carbon hinders formation of chloropropoxy. The elimination reaction of 1,2-dichloropropane and 1,2-dibromopropane yields 1-chloropropene and 1-bromopropene, respectively.Unexpected results were obtained with geminal 1,3-dihalopropanes. Whereas no products were obtained in the deuterated chloroform washings, 13C solid-state NMR showed the presence of olefins and or framework species. Upon addition of water, hydrolysis products allyl alcohol and propanol were obtained. The formation of allyl alcohol implies that the initial product was a propene bound to the zeolite framework. The original product is proposed to be formed via both elimination and substitution mechanisms. We interpret this combination as an intermediate between single and two consecutive eliminations. In support of this, two consecutive eliminations were observed with 1,3-dichlorobutane. Keywords: zeolite NaX, nucleophilic substitution, elimination, alkyl dihalides, framework propoxy
9:00 PM - HH3.3
Anodic TiO2 Nanotubes for Composite Materials.
Jan Macak 1 , Robert Hahn 1 , Andrei Ghicov 1 , Cordt Zollfrank 1 , Patrik Schmuki 1
1 Dep. of Materials Science, University of Erlangen, Erlangen, Bavaria, Germany
Show AbstractThe presentation deals with self-organized high aspect ratio TiO2 nanotubes grown by electrochemical anodization By optimizing the local electrochemical conditions, layers consisting of highly ordered TiO2 nanotubes with a length of several 100 micrometers can be grown on Ti surfaces. The diameters that can be obtained range from 20 nm to 300nm (1-4). This strategy to form self-organized structures can be used also for the whole range of other valve metals such as Hf (5), Zr (6), Nb (7), and Ti alloys (8-10). Porous TiO2 is highly functional material that has numerous interesting properties and it is widely used in, photocatalysis and biocompatibility (11, 12). The presentation will show that these TiO2 nanotubes can be used as a template for depositing secondary material into the tubes (13), in parallel to well known porous alumina case (14). The resulting structures can be used directly, e.g. in a solid state solar cell (requires formation of a p-n junction). Alternatively, the nanotubular TiO2 structure can be converted into various titanates upon hydrothermal alkali treatment (15). These issues will be discussed in detail.References:1. V. Zwilling, E. Darque-Ceretti, A. Boutry-Forveille, D. David, M.Y. Perrin, M. Aucouturier, Surf. Interface Anal. 27, 629 (1999).2. J. M. Macak, K. Sirotna and P. Schmuki, Electrochim. Acta, 50, 3679 (2005).3. J. M. Macak, H. Tsuchiya and P. Schmuki, Angew. Chem., 44, 2100 (2005).4. J. M. Macak, H. Tsuchiya, L.V. Taveira, S. Aldabergerova, P. Schmuki, Angew. Chem. 44, 7463 (2005)5. H. Tsuchiya and P. Schmuki, Electrochem. Commun., 7, 49 (2005).6. H. Tsuchiya and P. Schmuki, Electrochem. Commun., 6, 1131 (2004).7. I. Sieber, H. Hildebrand, A. Friedrich and P. Schmuki, Electrochem. Commun., 7, 97 (2005).8. J. M. Macak, H. Tsuchiya, L.V. Taveira, A. Ghicov, P.Schmuki, J. Biomed. Mater. Res., 75A, 928 (2005).9. K. Yasuda, P. Schmuki, Electrochem. Commun. 9, 615 (2007)10. A. Ghicov, S. Aldabergerova, H. Tsuchiya, P. Schmuki, Angew. Chem. 45, 6993 (2006)11. D. F. Ollis, E. Pelizzetti, N. Serpone, Env. Sci. Technol., 25, 1522 (1991)12. S. Nishiguchi, T. Nakamura, M. Kobayashi, H. Kim, F. Miyaji, T. Kokubo, Biomaterials 20, 491 (1999).13. J. M. Macak, B.G. Gong, M. Hueppe, P. Schmuki, Adv. Mater, in press.14. H. Masuda, K. Fukuda, Appl. Phys. Lett., 71, 2770 (1997).15. N.T. Padture, X. Wei, J. Am. Ceram. Soc., 86, 2215 (2003).
9:00 PM - HH3.31
Synthesis of III-V Nanocrystals by Co-reduction Reactions.
Zhaoping Liu 1 , Jiye Fang 1
1 Department of Chemistry, State University of New York at Binghamton, Binghamton, New York, United States
Show AbstractIII-V semiconductor nanocrystlas have attracted increasing interest due to their extensive applications in optoelectronic and spintronic technologies. However, they are hard to synthesize and expensive precursors are often involved. To meet the practical use, there is an urgent need to develop an approach in rapid and scalable production of monodisperse III-V nanocrystals. Herein, we report a convenient solution-phase method to prepare nanocrystalline III-V nanocrystals through co-reduction reactions. Nanometer-sized III-V particles were synthesized in a trioctylphosphine oxide solution under an argon stream by using a standard high-temperature organic solution synthesis device. Halides of groups III and V were chosen as starting materials and superhydride (LiBH(C2H5)3) was employed as reducing agent. By optimizing proper capping ligands, colloidal III-V nanocrystals of several nanometers in sizes could be reproducibly yielded. These nanocrystals have been well-characterized and the growth mechanism of III-V nanocrystals has been explored as well.
9:00 PM - HH3.32
Phase Separation in Annealed AuPt Nanoparticles.
Nadi Braidy 1 , Gianluigi Botton 2 1
1 Materials Science and Engineering, McMaster University, Hamilton, Ontario, Canada, 2 Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario, Canada
Show AbstractThe thermodynamic description of binary nanoparticles (NPs) is expected to be dramatically different from their bulk equivalent as the surface and interface energy contributions become significant with decreasing radius. Apart from size and overall composition, the juxtaposition of the phases within a NP is crucial as it fixes the area and the nature of the interface. In this study, we follow the evolution of AucorePtshell NPs upon annealing at high temperature to determine their lowest stable geometry and state.AucorePtshell NPs were synthesized by sequential precipitation of metal salts1. Chloroauric acid was first reduced with trisodium citrate to form ~16 nm Au NPs. The Au NPs were then coated with a ~3 nm layer of fine Pt clusters upon reduction of chloroplatinic acid with ascorbic acid. A drop of the solution was then left to dry on a Si-supported 50 nm-thick amorphous Si3N4 membrane TEM substrate (SPI supplies) and sealed in a quartz ampoule backfilled with inert gas. The ampoule was annealed at various times and temperatures, quenched into water and then broken to release the specimen for analysis.The phase distribution within individual 20 nm NPs was mapped by recording both, a high-resolution TEM (HREM) micrograph and an energy dispersive X-ray spectroscopy (EDXS) chemical map (in scanning TEM mode). HREM and EDXS were performed with a JEOL2010F field-emission TEM (200 kV) equipped with a Si(Li) X-ray detector (Oxford, INCA). The X-ray map data cube was spatially binned and background subtracted. The counting statistics was sufficiently high to fit Gaussians over the Au and Pt Lα peaks and generate quantitative Au concentration map having a spatial resolution of ~1.2 nm per pixel.Following a one day anneal at 300°C, interdiffusion of Au and Pt was activated albeit the low temperature resulting into a Au-rich core with an Pt-rich shell. However, according to the X-ray map, after only 10 min at 600°C, Au partly diffused to the surface of the NPs while the Pt shell receded. After 180 min at 600°C, the NP counts only a few crystalline domains and is completed segregated in two halves: an Au-rich and an Pt-rich phase. Moreover, when compared to the bulk phase diagram, the Au solubility in the Pt-rich side at 600 and 800°C was found to be twice as high. No such difference was measured on the Au-rich side of the segregated NPs.We can demonstrate via thermodynamic arguments that the segregated configuration within a NP is more stable than a core-shell one by comparing the relative energy contributions of the surfaces and the interface. It was possible to address the observed shift in the solubility of the Pt-rich side of the segregated NPs by recalculating the Au-Pt miscibility gap. This was done by computing a temperature and composition-dependent surface energy determined by the equilibrium of the surface layers with the rest of the NP. 1 G. Schmid et al., Angew Chem Int Ed Engl 30 (1991) 874.
9:00 PM - HH3.33
Light-Assisted Synthesis and Characterization of Nanophase Oxides.
Chia-Lin Chang 1 , Shriram Ramanathan 1
1 , Harvard University, Cambridge, Massachusetts, United States
Show AbstractNanoscale oxides are being actively researched for their relevance to applications in environmental coatings, electronic devices including transistors, microwave devices and ferroelectrics. Synthesis of nanoscale oxides of precisely controlled structures and stoichiometry is therefore important to understand fundamental properties of complex oxide nanostructures. An elegant approach towards synthesis of nanoscale oxides at low temperatures is by oxidation of precursor metal films or oxidation of non-stoichiometric oxides, particularly in presence of radiation such as ultra-violet light.In this paper, we present our recent research results on understanding the fundamental effects of photon irradiation during growth of nanoscale metal-oxides such as Al2O3 films of a few nanometers thickness. The microstructure of oxides is significantly influenced by photon irradiation, particularly in the ultra-violet (UV) regime. Our proposed theoretical model of low temperature metal oxidation involving UV radiation takes into consideration oxygen adsorption and desorption at the oxide/gas interface; ionic currents within the growing oxides enhanced by the UV-induced high-field migration; as well as electronic tunnel current in the metal-oxide-oxygen systems. Compared to the low tunnel electronic current in natural oxidation (without UV light), the tunnel electronic current due to excitation in the UV light enhanced oxidation process is dramatically larger than the thermionic electron current leading to an increased oxide thickness. In addition, the model is utilized to calculate the self-limiting oxide thickness as a function of temperature with and without UV radiation including the effect of oxygen partial pressure. Our numerical calculations show trends consistent with experimental reports (Chang and Ramanathan, Jl. Electrochem. Soc., in press, 2007).Further, electrical properties of UV-processed oxides are considerably superior to native oxides synthesized at room temperature. Using high-resolution electron microscopy, electrochemical impedance spectroscopy (EIS) and non-Rutherford ion scattering techniques, we show the origin of superior properties to be closely correlated to minimal oxygen non-stoichiometry arising from UV exposure. Further, we will present results on direct electrochemical measurements of modulating oxygen point defect chemistry in nanoscale oxides using light. Materials systems that will be discussed include nanophase aluminum oxide and titania. These results provide mechanistic understanding of role of photon irradiation during synthesis of nanoscale oxide ceramics and also unique routes towards affecting point defect chemistry in nanophase materials.
9:00 PM - HH3.34
Preparation and Photocatalytic Properties of TiO2/SiO2 Composite Nanofibers.
Sung Wook Lee 1 , Tae-Ho Lim 1 , Sang Beom Kim 1 , Dong Ho Hyun 1
1 Center for Research and Development, Doobon Inc., Cheongwon-Gun, Chungbuk Korea (the Republic of)
Show AbstractRecently much attention has been concentrated on the nanostructural fibers, because of their potential in nanodevice applications such as nanoscale electronics, chemical sensor and catalyst. In this study, TiO2/SiO2 composite nanofibers were fabricated with titania and silica hybrid sol and evaluated as a nonwoven mat having the photocatalytic behavior. By the electrospinning with sol-gel reaction, several hundend nanometer diameter fibers were obtained in the form of the nonwoven mat. Various electrospinning parameters such as applied voltage, solutin concentration, TCD(tip-to-collector distance), catalyst and solution pH were examined with the hydrid sol. As electrospun TiO2/SiO2 composite nanofibers has much of hydroxyl groups evidenced in FTIR analysis. After calcination of electrospun fibers, most of hydroxyl group were removed as shown in the TGA data. By calcinations, the electrospun fibers became somewhat stiffer but not brittled. Some calcined nanofibers have the interfiber junction point in their morphology. The results of XRD measurement showed the almost amorphous feature of the calcined composite nanofibers. The more detail structural characteristic of the TiO2/SiO2 composite nanofibers would be described with various instrumental analysis.The photocatalytic feasibility of the composite fiber nonwoven mat was evaluated by quantifying the visible light absorption capacity using ultraviolet and visible(UV-Vis)and photoluminescence spectroscopy.
9:00 PM - HH3.36
Synthesis and Structural Study of the Pd and Te Complexes for the Uniform and Well-crystallized Pd20Te7 Alloy Nanoparticles.
Norikazu Konishi 1 , Hideyuki Takahashi 1 , Hironobu Ohono 3 , Kazunari Takahashi 3 , Kiyotaka Asakura 4 , Yuichiro Koike 5 , Wang Jae Chun 4 , Atsushi Muramatsu 2
1 Tohoku Univ., Environmental studies, Sendai Japan, 3 , Mitsubishi Chemical, Kurashiki Japan, 4 Hokkaido Univ., Catalysis Research Center, Sapporo Japan, 5 , KEK, Tsukuba Japan, 2 Tohoku Univ., IMRAM, Sendai Japan
Show AbstractThe nanometer-sized materials have been vigorously investigated, particularly because of its application to industrial use, such as electronic devices. Many attempts to prepare the alloy and metallic nanoparticles by various methods have been reported. However, “uniform” and “well-crystallized” alloy nanoparticles could not be synthesized by these methods. These results suggested that alloy nanoparticles with uniform and well- crystallized structure would be synthesized by controlling the growth mechanism in the liquid phase. Reduction rate of metals in the solution seriously depended on the condition of metal ion and/or metal complex in the solution. Thus, “uniform” alloy nanoparticles can be considered to synthesize from predominantly controlled metal complex in the solution.In this study, taking the idea based on the predicted concentration of metal complexes in an aqueous solution as a function of pH into consideration, PdTe alloy nanoparticles was tried to synthesize. The concentration of Pd complexes in an aqueous solution was calculated by using the critical stability constants. The structure of the Pd complexes and Te complexes in an aqueous solution was analyzed by using the EXAFS. EDTA and citric acid was used as a complex agent for Pd and Te, respectively. The mixed solution of 0.04698mol/l Na2PdCl4, 0.01645mol/l TeCl4, 0.094mol/l EDTA, 0.0658mol/l citric acid and 0.1175mol/l Na2SO4 was introduced into glass vessel, followed by the pH control from 1 to 13. Three ml of 0.33mol/l hydrazine solution with the same pH was added to the Pd-Te mixed solution. From the results of the calculation, Pd-EDTA complex was expected to synthesize in the pH range from 5 to 10. On the other hand, EXAFS study clearly demonstrated that Pd was connected to EDTA, while Te was bonded with the citric acid. Thus, in this system, the structure of the metal complexes in the solution was agreed with the result of the calculation, and double complexes which contained both metals were not formed. XRD results shows that Pd20Te7 alloy was synthesized only in the pH range from 5 to 10, while various materials except the PdTe alloys was formed in the pH range under 5, and only the Pd metals was synthesized in the pH range over 10. Crystalline lattice stripes of Pd20Te7 nanoparticles were clearly observed in the HR-TEM micrograph. Moreover, HR-TEM/EDX analysis of one particle shows that concentration of Pd and Te was 76.00-76.63% and 23.37-24.00%, respectively. Thus, it can be concluded that Pd20Te7 nanoparticles synthesized by this method has “uniform” and “well-crystallized” structure, and the calculation of the metal complexes is effective for the synthesis of the alloy nanoparticles with these properties.
9:00 PM - HH3.38
The Potential of Indium Selenide (In2Se3) Nanobelts for the Nanoscale Phase-change Memory Application.
Wei-Fan Lee 1 , Chung-Yang Lee 1 , Kuo-Wei Huang 1 , Ho-Yeh Hsieh 1 , Chi-Te Huang 1 , Lih-Juann Chen 1
1 Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractIn2Se3 is a compound semiconductor with potential applications in data storage and phase change memory. The synthesis of one-dimensional In2Se3 nanobelts have been achieved via a vapor-liquid-solid process with the Au catalysts. The morphology, crystal structure, and chemical composition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectrometer (EDS). The electrical property measurement indicated that electrical transport is related to the one-dimensional ordered superstructure. A reversible phase transformation between the crystalline and amorphous state with the resistance ratio of the order of 102 ~ 104 was found.
9:00 PM - HH3.39
Reaction Dynamics for Gold Nanoparticles Synthesis in Solution Plasma.
Junko Hieda 1 , Takahiro Ishizaki 1 , Nagahiro Saito 2 4 , Osamu Takai 3 4
1 Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Nagoya Japan, 2 Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University, Nagoya Japan, 4 CREST, JST, Nagoya Japan, 3 , EcoTopia Science Research Institute, Nagoya University, Nagoya Japan
Show AbstractGold nanoparticles have been utilized in the field of nanotechnology and biotechnology due to its visible optical property and high bioaffinity. Many fabrication methods of the gold nanoparticles, e.g. a chemical reduction method, have been reported. However, these methods require a reducing agent to fabricate metal nanoparticles from the solution containing metal ion and extraction process of residues. Plasma materials processing in liquid phase allows to fabricate metal nanoparticles without addition of the reducing agent due to the reaction product of discharge. Furthermore, it has a potential of an industrial process for metal nanoparticles since this process would realize extremely rapid reaction under a high pressure. In our previous study, gold nanoparticles were successfully synthesized with discharge in aqueous and non-aqueous solutions. In this study, in order to elucidate the formation mechanism of gold nanoparticles in solution plasma process, we investigated the relationships between discharge states and reaction rates. Gold nanoparticles were synthesized through reduction with a discharge in a reverse micelle solution containing chlorauric acid as metal source. The reverse micelle solution was prepared by a conventional method; Aerosol OT (AOT) was dissolved to dodecane as a surfactant and subsequently chlorauric acid solution was added to the solution. The discharge was generated by a pulsed power supply. The applied voltage and the pulse width were ca. 960 V and 2 μs, respectively. During discharge, Ar gas was introduced into the non-aqueous solution to support the generation of the discharge. The gold nanoparticles were observed by transmission electron microscopy (TEM). Plasmon band of the gold nanoparticles were measured by ultraviolet-visible spectroscopy (UV-Vis). The particle size of gold nanoparticles synthesized in the non-aqueous system varied depending on the amount of water added into the reverse micelle solutions. TEM images showed that the mean diameter of particles was varied from 4 nm to 11 nm with the increase of the addition amount of water. We measured the emission spectra and current-voltage curves of discharge generated in the non-aqueous solutions under various discharge conditions. The plasma density and electron temperature were also estimated.
9:00 PM - HH3.4
Synthesis of Silica Nanocontainers by Templating of Magnetic Assemblies for Drug Delivery Vehicles
Jaemoon Yang 1 , Jaewon Lee 1 , Jinyoung Kang 2 , Jin-Suck Suh 3 , Ho-Geun Yoon 4 , Yong-Min Huh 3 , Seungjoo Haam 1
1 Chemical Engineering, Yonsei University, Seoul Korea (the Republic of), 2 Graduate Program for Nanomedical Science, Yonsei University, Seoul Korea (the Republic of), 3 Department of Radiology, College of Medicine, Yonsei University, Seoul Korea (the Republic of), 4 Department of Biochemistry and Molecular Biology, Yonsei University, Seoul Korea (the Republic of)
Show AbstractThe synthesis of novel nanomaterials with well tailored structures is a major challenge in biomedical applications for drug delivery carriers, diagnostic agents, sensing probes and tracking labels. Due to the monodispersity, large surface area, high drug loading, and the potential for hybridization with other organic/inorganic materials, hollow nanostructures for drug containers were employed as a drug delivery system. Hollow nanoparticles can be synthesized with various materials such as organic polymer, silicates, carbon, titinia, and phosphates. To produce the nanoparticle cavity, various templates, such as polymeric micelles or surfactants, silicates, gold nanoparticles and luminescence semiconductors, were used. Of the hollow nanomaterials, silica nanoparticles have been widely used due to easy formation and a convenient surface modification procedure. However, using silica nanoparticles as drug carriers demonstrated a rapid drug release from the nanostructure. To accomplish sustained release with a hollow structure, a surface modification process should be employed. In this study, hollow silica nanoparticles (HSNPs) were synthesized as a nanocontainer for a drug delivery vehicle. As templates for the embodiment of a large cavity in the silica nanoparticles, magnetic assemblies (MAs) were prepared by clustering magnetic nanocrystals with a surfactant binder. Acting as seeds, MAs were then wrapped with a silica shell by the modified Stöber method. The resulting magnetic silica nanoparticles (MSNPs) were etched using hydrochloride and calcinated at high temperature to form silica nanoparticles with a cavity core. Although these HSNPs encapsulated a large amount of drug, the release from the HSNPs was too fast to control the drug release pattern. To this end, surface modified HSNPs were synthesized for sustained drug release.
9:00 PM - HH3.40
Amine-capped Magnetite Nanoparticles for Bioconjugating: Interfacial Synthesis and Fluorescent Decoration.
Kang Sun 1 , Ke Tao 1 , Hongjing Dou 1
1 State key lab of metal matrix composites, Shanghai Jiao Tong University, Shanghai China
Show AbstractBy using a novel interfacial coprecipitation method, hydrophilic magnetite nanoparticles (MNPs) capped with amine groups are facilely fabricated. In the approach, di-n-propylamine and water/cyclohexane mixture act as the alkali and medium, respectively, so that the coprecipitate reaction is confined only on the interface between water and cyclohexane. It is confirmed by several kinds of characterizations that the resultant MNPs possess amine-decorated surfaces, which renders them not only the dispersibility in water without adding stabilizing agent, but also the capability of being further modified. Fluorescein isothiocyanate (FITC) was employed as a model molecule to modify the surface of MNPs by means of the covalent bonding between amine group and FITC. The results show that the FITC was connected to magnetite successfully, and the resultant nanoparticles display proportional fluorescence intensity with the number of amine groups. The successful decoration of FITC demonstrates the capability of further modification of the amine-capped MNPs, as well as their potential in bioconjugation or bio-probing.
9:00 PM - HH3.41
The Facile Preparation of CdSe/ZnS Nanocrystal Assemblies on Inner Surface of Microcapsules.
Hyun Min Jung 1 , Yong Seok Kim 1 , Jae Heung Lee 1 , Soon Ryoung Hur 1
1 Advanced materials division, Korea Research Institute of Chemical Technology, Daejeon Korea (the Republic of)
Show AbstractThe hybrid assemblies of nanocrystals with polymer have been one of interesting nano-sized structures, since their potential use in biological indicators and sensors. In this work, a facile strategy has been proposed to obtain the tens of nanometer thickness polymer film containing of nanocrystal assemblies. The CdSe/ZnS nanocrystal is assembled on inner surface of hollow microcapsule that is formed through interfacial condensation polymerization. Melamine-formaldehyde (MF) condensates as a shell material of 50~70 nm thickness are precipitated between oil-water interface and grown as a closed shell. Oleic acid coated CdSe/ZnS nanocrystal included in aliphatic hydrocarbon as a core material is well dispersed to be hydrophobic core then encapsulated by MF shell. The ring-shape fluorescence image of encapsulated CdSe/ZnS nanocrystal is observed through laser confocal microscope, which from the nanocrystal deposition on inner surface of MF shell. The obtained fluorescence spectrum of 598 nm wavelength from the nanocrystal containing MF-microcapsule dispersed in ethanol is almost same wavelength and intensity as bare nanocrystals in solution. The octadecane as the core material of MF-microcapsule is eliminated under the condition that the shell of MF resin layer swells, then the MF-microcapsule can be deformed to be folded to hemisphere shape. Chloroform and dichloromethane are found to be the effective solvent for this kind of transformation. As the result of deformation, CdSe/ZnS nanocrystal array located between two 50 nm thickness MF resin is obtained from MF-capsule with inner surface assembled nanocrystals. Through the laser confocal microscope, the half-circle fluorescence image is observed from the nanocrystals which are located between two layers of folded hemisphere. There is no leaching out of nanocrystals assembled on inner surface of microcapsule during the core octadecane is dissolved and eliminated, then the nanocrystals are well trapped inside of MF-capsule to be formed as polymer-nanocrystal-polymer layers. On the other hand coumarin 314 as a small molecule fluorescence dye included in shell layer of microcapsule slipped out from the microcapsule under the condition of MF-resin is swelling. The TEM image of deformed MF-microcapsule clearly shows 50 nm thickness MF double layers assembled with CdSe/ZnS nanocrystals. The MF-microcapsule containing of nanocrystals can be controlled from tens of micrometer to 300 nm in particle size and containing of hydrophobic chemicals along with nanocrystals as fluorescence indicator through the simple procedure of interfacial polycondensation technique. The resulting nanocrystal-polymer assembly shows good potential applicability, since the assemblies of nanocrystals positioned just under several tens of nanometer thickness polymer layer give almost same fluorescence properties as bare nanocrystals besides good stability of no leaching out under various solution circumstances.
9:00 PM - HH3.42
Gold–Nanoparticle/Smart-Hydrogel Hybrid Materials with Switchable and Tailorable Anisotropic Electrical Properties.
Jifan Li 1 , Bunichiro Nakajima 1
1 , Hitachi Chemical Research Center, Irvine, California, United States
Show AbstractIn this paper, a poly(N-isopropylacrylamide) (polyNIPAm) based hybrid material having thermo-tunable and anisotropic electrical properties is synthesized by patterning gold nanoparticles onto the surface of the hydrogel. The gold nanoparticle/hydrogel hybrid material is electrical conductive above the low critical solution temperature (LCST), and dielectric below the LCST. This hybrid material also has the ability to switch between anisotropical and isotropical electrical properties upon the change of the temperature depending on the pattern of the gold nanoparticles. And for tailored applications, many other stimuli-sensitive hydrogels can be used as the substrate instead of thermo-sensitive hydrogels.
9:00 PM - HH3.44
Ionic Liquid Thermofluids Incorporating Nanoparticles.
Benjamin Harrison 1 , Patricia Harrison 1 , Richard Czerw 1
1 , NanoTechLabs Inc., Yadkinville, North Carolina, United States
Show AbstractHigh temperature single phase thermofluids are needed for both open (to atmosphere) and closed systems to effective transfer heat between locations. Ionic liquids, organic salts that are liquid below room temperature, possess low vapor pressures and good thermal stability. The thermal conductivity of ionic liquid thermofluids can be enhanced through the addition of nanoparticles such as carbon nanotubes. The effects of nanoparticles on thermal conductivity, viscosity, vapor pressure, and thermal stability in terms of nanoparticle and ionic liquid composition were investigated.
9:00 PM - HH3.45
Micro/Nano Particles Prepared by Electrospraying for Protein Drug Delivery.
Minyoung Kim 1 , Ji Youn Yoo 1 , Jonghwi Lee 1
1 School of chemical Engineering & Material Science, Chung-Ang Univ., Seoul Korea (the Republic of)
Show AbstractThe development of polymeric carriers having a suitable release pattern is important for protein drug delivery systems. The surface energy control capability of electrohydrodynamic force provides electrospraying. Electrospraying is a very useful technique to generate monodispersed aerosols with droplets in the range of tens of nanometer to hundreds of micron through the electrostatic charging. In electrospraying, a liquid is passing through a nozzle, and the plume of droplets is generated by electrically charging the liquid to a very high voltage. The charged liquid in the nozzle becomes unstable as it is forced to hold more and more charge. Soon the liquid reaches a critical point, at which it can hold no more electrical charge and at the tip of nozzle it blows apart into a cloud of tiny, highly charged droplets.Electrospraying has various potential advantages such as simple particle size control, mono-dispersity, high recovery, and mild processing conditions. The advantages are appropriate to improve the stability of protein drugs and control its release. Herein, a novel electrospraying system and coaxial system were developed, and its practical aspects were examined.Water and organic solvent based systems were processed using uniaxial and coaxial electrospraying. In uniaxial system chitosan solution was used. In the coaxial systems, Bovin Serum Albumin (BSA) and iron (II/III)oxide nanopowder were used as the materials for the inner nozzle. As the encapsulation materials for the outer nozzle, chitosan was used. These solutions were emitted into coagulation liquids circulated in a T-type chamber by a fixed quantity metering pump. The effect of voltage, flow rate, dispersant, size of chamber, etc were examined to obtain the maximum efficiency of electrospraying. Chitosan particles were analyzed by the laser light scattering particle size analyzer, scanning electron microscopy, and transmission electron microscopy. The amount of loaded BSA is measured by BCA assay techniques.BSA-loaded chitosan particles were prepared successfully in novel uniaxial and coaxial electrospraying systems. In our early systems, the particles initial formed out of an electrospaying nozzle showed a narrow particle size distribution, but once they arrived to the collector part, they tended to aggregate depending on their dispersion stability. As a consequence, the bimodal distributions of particles were often observed. This aggregation could be prevented by using a new electrospraying system using a T-type chamber, so unimodal size distributions were observed. But in the cases using TPP solutions and phosphate buffer solutions as dispersants, a bimodal size distribution caused by aggregation was produced. After freeze drying, the morphologies of electrospryed particles were changed into the fiber shape.
9:00 PM - HH3.47
Anisotropic Nanofiber Fabrication via Electrohydrodynamic Technology.
Chul Ho Park 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science, Chung-Ang University, Seoul, Heukseok-dong, Dongjak-gu, Korea (the Republic of)
Show AbstractNano-scale materials exhibit special characteristics which are not observed in bulk materials and can be tuned by adjusting the particle size. Due to the minimization of the interfacial tension energy, nanoparticles are typically prepared in spherical shape and their surface chemical groups are isotropically arranged. Theoretical works have shown that anisotropic particles could be very useful for controlling molecular recognition and self-assembling processes, which are one of the more intriguing and challenging aspects in a future materials science. Over the last few years, there has been increasing interest in an electrohydrodynamic (EHD) technology to fabricate nano-scale materials such as fibers, vesicles, and hollow structures. Especially, this technology has been used for anisotropically phase-separated particles or fibers in nano-scale by a simultaneous EHD of parallel polymer solutions under the influence of an electrical field. However, there are limitations of anisotropic particle fabrication, for example, miscibility and conductivity changes among polymer solutions or solvents which cause electrostatic instability on the meniscus and incapacity of EHD. In this study, countercharged EHD jetting technique was developed to overcome this limitation, which results in neutralization and collision between as-sprayed and as-spun materials based on the Coulomb force. Negative and positive charges were supplied for fiber and particle fabrication out of two identical nozzles consisting of stainless steel, respectively. Flow rates for both solutions were 1 ml/h. The nozzle-to-nozzle and nozzles-to-ground distance are 7 and 10 cm, respectively. The encountering (collision between as-spun fibers and as-sprayed particles) phenomenon was observed under more than 8 kV electric field. Hydrophobic polystyrene particles of nano- to micro-sizes were anchored on the hydrophilic surface of polymethylmethacrylate (PMMA) nano- or micro-fibers. In another application, small organic molecules were successfully coated on the PMMA fibers. Gold nanoparticles dispersed in water were attached on PS string fibers. These results suggest that countercharged EHD can provide a novel way to prepare composite nanostrucutures, especially anisotropic material fabrication, without a significant dependence on the selection of materials (polymers or solvents) and EHD variables such as conductivity, flow rate, viscosity, etc.
9:00 PM - HH3.48
Polymer Nanocomposites with Low Thermal Expansion Coefficient.
YuanQiao Rao 1 , Thomas Blanton 1
1 Research Labs, Eastman Kodak Co, Rochester, New York, United States
Show AbstractThis paper describes a PEO/clay(PVP) nanocomposite that was designed, as well as the nanocomposite film that was produced as a result. The film exhibits a low thermal expansion coefficient of about 10 ppm/oC, which is similar to that of metals. The film also exhibits an unexpectedly high heat distortion temperature as well as a much improved O2 barrier property, high stiffness, and high strength. The significant property improvements are related to the structure of the formed composite. The property change with the amount of clay added suggests that superior properties can be obtained when the added clay is above a critical point.
9:00 PM - HH3.49
Glass Transition of Polymer Nanocomposites: An Insight from the Nanoparticle-Polymer Interface.
Jaydeep Basu 1 , Sunita Srivastava 1
1 Physics, Indian Institute of Science, Bangalore, Karnataka, India
Show AbstractThe characteristic properties of nanoparticle-embedded polymers – polymer nanocomposites - have been the subject of study for a long time because of their unique optical, thermal, mechanical and electronic properties. However, attractive as such nanocomposites might be the process of blending or dispersing nanoparticles in a polymer matrix has proven to be problematic. In spite of progress made in preparation and bulk characterization of polymer nanocomposites over the last few years large scale applications and replacement of the existing technologies involving normal composites has not been achieved due to a fundamental lack of understanding of the micro/nanoscopic interactions between the polymer chains and the nanoparticle and the effect of these interactions and the structure at the nanoscale on the macroscopic properties of the composites. Hence to understand this problem appropriately it is necessary to use high-resolution localized probes to look at nanoscopic regions of the polymer nanocomposites, encompassing nanoparticle -polymer interfaces and try to relate this to macroscopic properties like visco-elasticity, glass transition (TG), etc. To address this issue we have performed highly sensitive modulated differential scanning calorimetry (MDSC) measurements of glass transition of polymer nanocomposites using various polymers like polymethylmethacrylate (PMMA) and polystyrene (PS) which are embedded with gold nanoparticles of various fractions and sizes and capped with respective polymers. To prepare PS capped gold nanoparticles we have used thiol-terminated PS while for PMMA capped gold nanoparticles we have used the same PMMA as the matrix. We were able to vary the polymer-nanoparticle interface morphology was controlled by varying the surface segment density and was characterized using small angle x-ray scattering (SAXS). We have used a new parameter, nanoparticle-polymer interfacial width, σ, in elucidating role of surface effects on glass transition of polymers. Gold nanoparticles of various diameters (2-20nm) were prepared as described earlier [1,2]. We have used numerical FFT to obtain consistent density profiles of the nanoparticle polymer interface from Porod plots of the, respective, SAXS for various fractions of gold nanoparticles embedded in respective polymers. We could tune the Tg of 120K PMMA (1170C) by almost 220C and more interestingly could observe both positive and negative deviation from bulk PMMA, by varying the interfacial width. Similarly, for the PS-thiol capped gold nanoparticles we could also observe both positive and negative deviation of Tg by variation of capping density – something not observed earlier. Systematic work is being carried out to generalize the observations for different combinations of nanoparticle and polymer.Reference:(1) S. Srivastava and J.K. Basu, Phy. Rev. Lett. 98, 165701 (2007)(2) S. Srivastava and J.K. Basu, J. Nanoscience and Nanotechnology 7, 2101 (2007)
9:00 PM - HH3.5
Nucleophilic Attack of Isocyanates by X-Type Faujasite Zeolite.
Jared DeCoste 1 , David Doetschman 1 , Miranda Lahr 1 , Barry Jones 1
1 Department of Chemistry, Binghamton University, Vestal, New York, United States
Show AbstractSince the Union Carbide disaster in Bhopal, India in 1984, isocyanates have been viewed as one of the most harmful class of chemicals. The Environmental Protection Agency, along with other sources, list methyl isocyanate (MIC) and 2,4/2,6 toluene diisocyanate along with other isocyanates as hazardous wastes, and potential pollutants. Isocyanates have been shown to be fairly unresponsive to conventional cleanup and scrubbing methods. It is well documented that isocyanates are susceptible to nucleophilic attack across the nitrogen/carbon pi bond. The zeolite sodium Faujasite X (NaX) has been shown to have nucleophilic character at oxygen atoms that are directly bonded to an aluminum atom in the framework, due to a delocalized anionic charge. Cyclohexyl isocyanate (CHIC), octyl isocyanate (OIC), isopropyl isocyanate (IPIC), tert-butyl isocyanate (TBIC), and toluene 2,4 diisocyanate (T24DI) were adsorbed by NaX in this study and the resulting products and residual isocyanate were characterized by 13C CP MAS NMR and solid state FTIR. All of the isocyanates reacted to give a carbamate framework type species with the zeolite oxygen atom attached to the functional carbon, and the anionic isocyanate nitrogen atom stabilized by the sodium cation. For the reaction of TBIC with NaX there appear to be two reactions occurring, one to form the framework carbamate species, and a second to form the corresponding olefin, 2-methyl propene. For the reaction of T24DI with NaX, only one of the isocyanate moieties reacts, while the other is left unperturbed. Subsequently water was added to the product to permit hydrolysis of the second isocyanate moiety to occur. Through FTIR it was confirmed that then there were no isocyanate functional groups left in our product. This NaX adsorption of isocyanates has very practical applications, not only in hazardous materials cleanup, but possibly also in controlling the release of isocyanate vapors in the workplace and from factories.
9:00 PM - HH3.50
Radial Assembly of Quantum Dots in Amphiphilic Block-Copolymer Aggregates.
So-Jung Park 1 , Brenda Sanchez-Gaytan 1 , Weihong Cui 1 , YooJin Kim 1 , Miguel Mendez-Polanco 1 , Michael Fryd 1 , Bradford Wayland 1
1 Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show AbstractA unique radial assembly of quantum dots (CdSe nanocrystals stabilized with trioctylphosphine oxide) was formed in spherical aggregates of poly(acrylic acid)-block-polystyrene (PAA-b-PS) block-copolymers by the slow addition of water to the dimethylformamide solution of quantum dots and block-copolymers. The intensity profiles of transmission electron microscope images reveal that the assemblies were composed of three parts: 1) an outer polymer shell, 2) an inner polymer core, and 3) quantum dots arranged at the interface between the polymer core and the shell. The quantum dots incorporated in the polymer assemblies were highly luminescent retaining the quantum yield (40 % - 75 %) of the original nanoparticles and they were very stable in aqueous solution over a period of months showing a promise for their use as an optical imaging probe. Importantly, it was found that quantum dots assemble cooperatively with block-copolymers and induce a drastic morphology change of block-copolymer aggregates rather than being simply incorporated as solutes. This study demonstrates that the manipulation of the interactions among nanoparticles, block-copolymers, and solvent can lead to unique assembly structures that are not possible by the simple solubilization approach.
9:00 PM - HH3.51
Carbon-Halide Nanocomposites for Asymmetric Hybrid Supercapacitors.
Prabeer Barpanda 1 , Glenn Amatucci 1
1 Department of Materials Science and Engineering, Rutgers University, Piscataway, New Jersey, United States
Show Abstract With the advent of nanotechnology, nanostructured materials and nanocomposites have been investigated for applications ranging from structural materials to semiconductors/ electronic devices. One such commercially successful usage of nanomaterials is in the broad field of energy storage and electrochemistry. The induction of nanotechnology has been reported to achieve high-performance intercalation and conversion materials ranging from metal-halides and transition metal oxides. Recently, our group has shown a new path towards improved volumetric capacity (~200-500% increase) in electrochemical double layer capacitor (EDLC) materials by using a new class of carbon-halide nanocomposites. EDLC (known as supercapacitors) is a leading energy storage device owing to its outstanding power density, extraordinary cycling stability and robustness. Activated carbons are most widely used in EDLCs due to their economic production and tunable surface morphology. The current work unveils the synthesis and usages of a novel high-performance carbon-based electrode with nanoscale physico-chemical modification. The true capacitance of carbon electrodes is a combined effect of the Helmholtz double layer on the electrode-electrolyte interface (non-faradaic) and the space charge capacitance of solid electrode. The performance of these electrodes can be enhanced by inducing Faradaic reactions by different physico-chemical modification of activated carbons. Here, we have reported one such high-capacity carbon electrode by chemical treatment with halides (iodine and bromine). Halides have been incorporated into activated carbons at nanoscale by vapor halidation or high energy mechanochemistry techniques. The morphology and porosity of these host carbons have been controlled by mechanical milling and chemical activation. The highly-reactive halides induce charge-transfer reactions with the semi amorphous carbon host thus modifying the chemical structure and bonding nature of halidated carbon, forming different polyhalides compound and altering its DOS. Subsequently, these halidation improves the overall capacity of carbons by modifying the non-Faradaic and inducing a psuedocapacitive Faradaic component. The physical and electrochemical properties of these halidated carbons have been extensively studied by X-Ray, Raman spectroscopy, TGA, BET analysis and electrochemical testing and will be reported.
9:00 PM - HH3.52
Mixing Homogeneity, Porous Texture, and Thermal Stability of Copper-based Nanocomposite Materials/Catalysts.
Yu Xing 1 , Zhenxin Liu 1 , Steven Suib 1 2
1 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States, 2 Department of Chemical, Materials & Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractHomogeneity of a nanocomposite material, representing the quality of mixing of heterophase nanoparticles, is of importance for the performances of structural materials, coatings, catalysts, pharmaceuticals, and advanced energetic, electronic, photonic, and magnetic materials. Copper/aluminium nanocomposite materials were prepared via different inorganic synthesis methods including coprecipitation, gelation, and stepwise thermal modification. Nitrogen sorption measurements and X-ray diffraction were used for textural and structural analysis, respectively. FESEM, HRTEM and CBED were used for the observation or structure determination of the copper/aluminum nanocomposites. Solid-solid reaction analysis and differential scanning calorimetry (DSC) analysis were developed for the determination of the mixing homogeneities of copper-based nanocomposite materials. Preparation methods significantly affect the mixing homogeneity, average pore size, and pore size distribution of the nanocomposites. A “hereditary” character of the homogeneity of copper/aluminum nanocomposites was revealed: the homogeneity of a decomposable copper/aluminum nanocomposite (e.g. Cu2CO3(OH)2/Al(OH)3) may dominate the homogeneity of its decomposed product (e.g. CuO/Al2O3), and the latter continues to dominate the homogeneity of its reduced product (e.g. Cu(0)/Al2O3). A sintering experiment, 250-600 °C for 350 hr under methanol-steam reforming conditions, was carried out to compare the stability of supported Cu(0) nanoparticles. Although a large initial size of supported nanoparticles is not favorable, those supported nanoparticles with a small initial crystallite size (e.g. 8-9 nm) cannot ensure good thermal stability. Mixing homogeneity of a nanocomposite is likely the major factor for the stabilization of nanoparticles. Creation of narrow distributions of pore size with small major pore diameters (e.g. around 35 Å) caused a “sintering stop zone” over a wide temperatures, possibly via space limitations. By delicate inorganic synthesis design, the specific copper loading of copper/aluminum nanocomposites can be significantly increased, which might be valuable for apparatus with space limitation, such as vehicle fuel cell systems.
9:00 PM - HH3.53
Mechanisms Leading to Improved Mechanical Performance in Nanoscale Alumina Filled Epoxy.
Su Zhao 1 , Linda Schadler 1 , Henrik Hillborg 2 , Tommaso Auletta 2
1 Materials Science and Engineering Department and Rensselaer Nanotechnology Center, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 , ABB Corporate Research, Västerås Sweden
Show AbstractOne of the potential advantages of nanoparticle filled thermosets is the unique combination of mechanical properties that can be obtained. There have been several reports of improved ductility and toughness in brittle thermoset polymers due to the addition of equiaxed nanoparticles. The mechanisms leading to these improvements, however, are poorly understood. In the present study, a model system of nanoscale alumina filled bisphenol A based epoxy with two interface conditions was used to highlight the mechanisms leading to significant improvements in ductility, toughness, modulus and fatigue crack propagation resistance. It was found that crack deflection, interfacial debonding and particle pull-out were critical for composites with a weak interface, but that a stronger interface lead to additional mechanisms of further crack deflection, plastic deformation, microcracking and as a result a further improvement in mechanical properties.
9:00 PM - HH3.54
Formation and Characterization of Multifunctional Palladium-Silsesquioxanes Nanocomposites.
Sonia Letant 1 , Amitesh Maiti 1 , Ticora Jones 1 , Richard Gee 1 , Robert Maxwell 1 , Andrew Saab 1
1 Chemistry, Materials, and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Show AbstractPrompted by the need to design stable and functional nanoscale catalytic materials, we explored a system comprised of Pd nanoparticles coated with functionalized polyhedral oligomeric silsesquioxane (POSS) cages. Experimental results showing the successful stabilization of Pd nanocrystals with functional POSS molecules will be presented for various POSS functionalities and symmetries. Parameters governing the kinetics of nucleation, dispersion, and precipitation of these Pd/POSS nanocomposites will be discussed using mesoscale simulations performed with Dissipative Particle Dynamics (DPD). Efficient hydrogenation was observed when exposing a mixture of Pd/POSS and unsaturated diphenylbutadiyne (DPB) to hydrogen, thus demonstrating catalytic activity of the coated Pd nanoparticles. In order to gain deeper insight into the catalytic mechanisms we performed density functional theory (DFT) calculations of POSS binding to Pd(110) surface through various functional groups, and investigated the hydrogen storing ability of POSS, as well as possible pathways for hydrogen radicals from the catalyst surface to unsaturated bonds located further away. Our next goal is to use the theoretical models developed in this study as a design tool to build a versatile and self-contained catalyst-scavenger system, which could be embedded into different polymer matrices.This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-Eng-48. It was funded by a Laboratory Directed Research and Development grant (06-SI-005). UCRL-ABS-231684.
9:00 PM - HH3.55
Spectroscopic Investigations of Dendrimer-Au Hybrid Nanoclusters.
Akinori Tanaka 1 , Yoshiaki Murase 1 , Takanobu Kitagawa 1 , Hidehiro Yasuda 1
1 Department of Mechanical Engineering, Kobe University, Kobe Japan
Show AbstractWe have systematically synthesized the dendrimer-Au hybrid nanoclusters, and have carried out the various spectroscopic studies in order to investigate their optical properties and electronic structures. Dendrimer-Au hybrid nanoclusters were prepared using the second generation COONa- and OH-terminated poly(amidoamine) dendrimer templates. From the transmission electron micrographs and electrospray ionization mass spectra of thus-prepared samples, it is found that a size-selective ultrafiltration treatment allows us to divide among the relatively larger Au nanoclusters stabilized outside the dendrimer and the relatively smaller ones encapsulated inside the dendrimer. While the extinction spectra of Au nanoclusters stabilized outside the dendrimer with mean diameter of 2.5-3 nm show distinct plasmon resonance, the dendrimer-encapsulated Au nanoclusters with mean mass number of Au13-Au25 show no Mie plasmon resonance, indicative of non-metallic features due to the quantum confinement effect. In addition, the photoluminescence spectra of these dendrimer-encapsulated Au nanoclusters exhibit the strong blue emissions as reported in the literature. However, these photoluminescence spectra are similar to those of dendrimer templates used in this work. Therefore, it is considered that the photoluminescence of the present dendrimer-encapsulated Au nanoclusters is related to dendrimer template. The valence-band X-ray photoemission spectra of the present Au nanoclusters show the distinct decrease of apparent width of Au 5d-derived bands, compared with that of bulk Au crystallite. This originates from the lower averaged nearest Au coordination numbers in the relevant size regime. Moreover, we have measured the Au core-level photoemission spectra in order to investigate the interface features between the Au nanoclusters and dendrimer templates. From these results, we discuss the detailed electronic structures of dendrimer-Au hybrid nanoclusters.
9:00 PM - HH3.56
The Interfaces Between Aluminum by Metal Organic Chemical Vapor Deposition and Various Basic Structure Unit-oriented Mesophase Pitch-based Carbon Fibers.
Takakazu Suzuki 1
1 , AIST, Tsukuba Japan
Show AbstractGraphite basic structure unit (BSU)-oriented mesophase pitch-based fibers will make those applications very attractive, and will improve those composite materials properties. But little is known about effects of the BSU orientations in mesophase pitch-based carbon fibers on the interface reactivity of the matrix. We present the effect of the BSU orientation in mesophase pitch-based carbon fibers on the compatibility with Al.The tensile properties of BSU-oriented mesophase pitch-based carbon fibers/Al composites were measured after annealing of 773-873K for 2h in Ar. Mesophase pitch-based carbon fiber's nanotexture which was assigned as a random, a radial, or an onion structure was evaluated by SEM. Interactions between those fibers and aluminum were observed bt TEM and EDX. Lc(002) increases with the Young’s modulus of fibers (200-700GPa), while d002 decreases.Changes in tensile strength were strongly affected with the BSU orientation of mesophase pitch-based carbon fibers. Composites of aluminum and onion structured fibers exhibited higher tensile strength than that of other structured fibers. Reactivity of Al varied with the nano-structured fibers.The results show except in the JIS-70(onion structure, young’s modulus 700GPa)/Al composite that a reaction products form in the neighborhood of the interface. In the NS-20(random structure, 200GPa)/Al composite, we observed a black band layer of 10 nm in thickness formed along the outer circumference of the fiber.With EDX line analysis, gentle concentration gradients were obtained for both carbon and Al, while the profile of oxygen had a peak on the interface, it suggests that a concentration of oxygen exists at the interface. Similar results were obtained with the P-55 (radial structure, 400GPa)/Al composite.The black band had a thickness of 10 nm, which was nearly equal to that of the NS-20/A1 compositeFurthermore the black band part shows a number of protuberances as if indicating a process of tissue proliferation; carbon appears to have diffused into the aluminum.TEM image of the NS-60(random structure, 600GPa)/Al showed that the thickness of the black band at the interface decreases to about 5 nm.The result together with the presence of excess oxygen and small amount of carbon, makes an oxycarbide the likely reaction producr.No black band was observed, however, in the JIS-70/Al composite. The comparatively steep gradient in carbon content and markedly low oxygen content, compared to previously mentioned composites, were measured at the interface by EDX.This means that the fiber of an onion structure itself has some sort of diffusion barrier layer, thereby suggesting the possibility that it may be usable without any additional barrier coating*. By optimizing the fiber nanostructure orientation, we may be able to produce innovative composite materials for more applications that require high temperature stability or increased compatibility.*Takakazu Suzuki etal, Carbon,37(1999),47-59.
9:00 PM - HH3.57
Compatibilizing Polyvinylidene Fluoride/Nylon6 Blends with Montmorillonite Nanoclay Particles.
Loan Vo 1 , Emmanuel Giannelis 1
1 Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractWe have utilized nanoclay particles to compatibilize poly(vinylidene fluoride)/nylon6 immiscible blends. By organically modifying the clay, the affinity of the particles can be adjusted such that there is dispersion throughout the matrix and at the polymer/polymer interface. The reinforcement of the matrix and improved interfacial adhesion in the nanocomposite leads to a stronger, stiffer, and tougher blend. The addition of clay particles also leads to a finer morphology with suppressed domain phase crystallization. The properties of the nanocomposite blends will be presented, and the compatibilization and toughening mechanisms will be discussed.
9:00 PM - HH3.58
Anisotropic Phospholipid-Nanorod Composites.
Christopher Orendorff 1 , Darryl Sasaki 1 , Todd Alam 1 , Bruce Bunker 1
1 , Sandia National Laboratory, Albuquerque, New Mexico, United States
Show AbstractMetal nanorods and nanowires have attracted considerable attention in recent years due to their interesting mechanical and optoelectronic properties. The 1D and 2D anisotropic assembly of metal nanorods has been demonstrated by a variety of chemical, physical, and biological methods. Here, we present the synthesis and directed assembly of phospholipid-nanorod composites. Lipid-modified nanorods self-assemble into liquid crystalline ordered structures while as-prepared cetylritmethylammonium bromide- (CTAB) protected nanorods assemble into disordered nanorod networks. We also present strategies for creating dynamic nanostructures; where the functionality to facilitate switchable assembly is engineered directly into the composite. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.
9:00 PM - HH3.6
Control of Twinning in Oblique Angle Deposited Copper Nanorods.
Huafang Li 1 , Asit Kar 1 , Thomas Parker 1 , Gwo Wang 1 , Toh Lu 1 , Christopher Johansen 2 , Hanchen Huang 2
1 Center for Integrated Electronics, Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show AbstractTexture and twinning in copper films can significantly affect properties, such as mechanical strength, oxidation resistance, and electrical conductivity. Oblique angle deposition (OAD), which uses atomic shadowing effect, has produced isolated crystalline copper nanorods. These nanorods can have an average diameter ranging from a few tens of nanometers to more than one hundred nanometers, depending on the deposition conditions. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), and x-ray pole figures were used to characterize the morphology, twining and texture of these nanorods. For stationary substrate depositions at a large oblique angle of 85° with respect to the surface normal, single crystalline copper nanorods were produced with the <110> aligning preferentially with the rod axis. The nanorod film as a whole has a preferred texture that is nearly biaxial. Twins are rarely observed in these nanorods. In contrast, when a swing rotation is used (back and forth rotation of the substrate about an azimuthal angular range) during the deposition, we have found for the first time that the density of twinning in these copper nanorods can be modified dramatically. The twin density within each nanorod can be controlled by the swing speed and the angular range of the swing. We have successfully introduced twins with periodicity of a few nanometers along the nanorod length. Possible mechanisms that contribute to the formation of these twinning interfaces in the copper nanorods, such as anisotropic surface diffusion rates of the deposited atoms and energy barriers for diffusion of adsorbed atoms, will be discussed. This work is supported by the NSF award 0506738. T Parker and C G Johansen are supported by DOE GAANN.
9:00 PM - HH3.60
Preparation and Photocatalytic Activity of Self-assembled Transparent Heteropolyacid-TiO2 Hybrid Thin Films by Layer-by-layer Coating.
Sayaka Yanagida 1 , Akira Nakajima 1 , Yoshikazu Kameshima 1 , Kiyoshi Okada 1
1 Department of Metallurgy & Ceramic Science, Tokyo Institute of Technology, Tokyo Japan
Show AbstractHeteropolyacids (HPAs) are a series of inorganic clusters, and their general formula is described as XMO (M = W, Mo, V, Nb or Ta, and X is called as the hetero atom). It is well known that HPAs is a strong acid and Keggin type HPAs (HxXM12O40n-) have been well investigated as a thermal catalyst for chemical industry. HPAs are also known as a photocatalyst. Very recently, it was reported that W-based HPA decompose fluorocarbons in water by UV illumination. Since fluorocarbons are hard to decompose by TiO2 photocatalyst, this result imply that the W-based HPAs possesses stronger oxidation power that TiO2. When UV light is illuminated on the HPA, electrons are excited from O2p to W3d, and the hole generated oxidizes various organic molecules. Since HPAs often adsorb and form complex between organic substances, they have a good potential for photocatalyst with high activity for environment purifiction. The HPAs are highly soluble in water and in organic solvents. For that reason, they are commonly used as homogeneous catalysts. However, direct use of HPAs for photocatalytic purification presents an obstacle to their separation from treated water. Therefore, preparation of a heterogeneous catalyst system of HPAs has been investigated using inorganic host materials such as mesoporous silica and clays.In this work, we prepared HPA-TiO2 hybrid thin films by layer-by-layer coating. Then, their photocatalytic activity was evaluated. We employed 12 tungsto phosphoric acid (H3PW12O40, hereafter denoted as PW12) and commercial TiO2 nano-particle. In acid solution, TiO2 has positive charge, therefore PW12 polyanion adsorbed on TiO2 surface by coulombic interaction. PW12 and TiO2 were alternatively deposited on glass substrate n times and the thin film (PW12/TiO2) n was prepared. PW12 was identified from composite by FT-IR spectra and XPS measurement. Layer-by-layer growth of the hybrid film was confirmed by constant absorbance change in UV-vis spectra. Photocatalytic decomposition activity on gaseous 2-propanol was examined in air using hybrid thin films prepared and a control TiO2 film. 2-propanol was decomposed to acetone and finally oxidized to CO2 and H2O in photocatalytic decomposition process. Concentrations of 2-propanol, acetone and CO2 were monitored by gas chromatograph during UV illumination. Comparing TiO2 film, PW12/TiO2 composites exhibit higher decomposition ratio. Especially, quite high acetone decomposition rate was obtained when film top layer was PW12. Detailed adsorption experiment revealed that PW12/TiO2 powder composites possess higher acetone adsorption capability than TiO2 powder. On the other hand, the composite exhibits low adsorption capability against 2-propanol than PW12. These results imply that decomposition rate difference can not be attributable to adsorption behavior, and that PW12 photocatalytic property or its scavenger effect against TiO2 might play an important role on the high decomposition rate of the hybrid films.
9:00 PM - HH3.61
Nafion®-based Nanocomposite Membrane Using Phosphoric Acid-Functionalized Silica.
Jung-Soo Kang 1 , Li-Jin Ghil 1 , Chang-Kyeom Kim 1 , Hee-Woo Rhee 1
1 Chemical and Biomolecular Engineering, Sogang University, Seoul Korea (the Republic of)
Show AbstractNafion®, preferred membrane in proton exchange membrane fuel cell (PEMFC), has to be fully hydrated to obtain an ideal efficiency because its proton conduction relies on sulfuric acid group which needs water to dissociate protons. For this reason, PEMFC is usually operated below 80 oC to prevent dehydration of Nafion® membrane. To solve this problem, nano-scaled solid proton conductor (SPC) has been employed to modify Nafion® membranes.To synthesize SPC based on phosphoric acid, the desired ratios of phosphoric acid and dimethyl dichlorosilane were mechanically mixed under N2 atmosphere. The acquired SPC was placed in vacuum oven for 1 day and was ultrasonically mixed with Nafion® polymer solution, and the solution was cast on a Teflon® plate and dried. The proton conductivity of the composite membrane was measured by 4-probe current interrupt method using impedance spectroscopy (IM6, Zahner) and showed maximum conductivity at 20 wt% of SPC, which was 30% higher than the conductivity of Nafion®.Glass transition temperature (Tg) will be measured with dynamic mechanical analyzer (DMAQ 800, TA Instrument). FT-IR (Nicolet 380 Spectrometer) and solid-state 29Si NMR (400 MHz) will be employed to confirm the chemical structure of composite membrane. Thermal behavior of composite membrane will be studied by thermo-gravimetric analysis (TGA, TA Instrument).
9:00 PM - HH3.62
Preparation and Characterization of Ag/redoped Polyaniline Nanoparticle Composites.
Sooyoen Sim 1 , Seungsoon Im 1
1 Fiber and polymer Engineering, Hanyang university, Seoul Korea (the Republic of)
Show AbstractPolyaniline nanoparticles doped mercaptosuccinic acid (MSAPani) was synthesized via doping, dedoping and redoping method. Ag/redoped polyaniline nanoparticle composites (MSAPani-Ag) was successfully prepared as adding aqueous silver nitrate solution, and the structures and chemical properties of the nanoparticles are confirmed by FT-IR and UV-vis spectroscopy. Morphology of the MSAPani nanoparticles is globular or ellipsoidal in shape, and their typical size is below 100 nm. In XPS spectra, we clearly observed thiolate peak at 162.7 eV, which is indicative of Ag-sulfur bonding but DBSA is not completrly removed by dedoping process. The thermal stabilities of the MSAPani and MSAPani-Ag were studied by measuring TGA thermograms, the surface resistivity and XPS. The surface resistivity data showed that MSAPani-Ag had the lower resistivity at the higher temperature, which indicates that the introduction of Ag. improved the thermal stability of the polyaniline MSAPani-Ag had the lowest resistivity at 120 degree and different aging treatment condition (under N2 , O2 ) affected to resistivity .Under O2 condition, the sample had the lower resistivity than N2 condition, confirming that oxidation leaded to improved thermal stability of the Ag/polyaniline. In XPS spectra, we observed new thiolate peak at 161.7 eV, which may be attributed to the Ag-sulfur bonding and XPS 2p reveals the formation of monosulfide after heating under air and N2 atomosphere.
9:00 PM - HH3.63
Flame Retardant Intumescent Polyamide 11 Nanocomposites: Thermal, Mechanical, and Flammability Properties.
Joseph Koo 1 2 , Si Lao 1 , Wen Yong 1 , Gerry Wissler 2 , Louis Pilato 2 , Zhiping Luo 3
1 Mechanical Engineering, The University of Texas at Austin, Austin, Texas, United States, 2 , KAI, LLC, Austin, Texas, United States, 3 Microscopy and Imaging Center, Texas A&M University, College Station, Texas, United States
Show AbstractCurrent thermoplastic polymer polyamide 11 and 12 are lacking in fire retardancy and high strength/high heat resistance characteristics for a plethora of finished parts that are desired and required for performance driven applications. By the introduction of surface modified montmorillonite (MMT) clay, carbon nanofibers (CNFs), and conventional intumescent flame retardant (FR) additives into the polyamide 11/polyamide 12 (PA11/PA12) by melt processing conditions, a family of intumescent polyamide 11 nanocomposites was created. It is anticipated these intumescent polyamide 11 and 12 nanocomposites will result in enhanced polymer performance characteristics, i.e., fire retardancy, high strength, and high heat resistance. It will expand the market opportunities for polyamide 11 and polyamide 12 polymer manufacturers.The objective of this research is to develop improved polyamide 11 and 12 polymers with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) in rapid manufacturing (RM). In the present study, a nanophase was introduced into the polyamide 11 and combining it with a conventional intumescent FR additive via twin screw extrusion. Arkema RILSAN® polyamide 11 molding polymer pellets was used with two types of nanoparticles: chemically modified montmorillonite (MMT) organoclays, carbon nanofibers (CNFs); and Clairant’s Exolit® OP 1230 intumescent FR additives were used to create a family of FR intumescent polyamide 11 nanocomposites.Wide angle X-ray diffraction (WAXD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to determine the degree of dispersion. Injection molded test specimens were fabricated for physical, thermal, mechanical properties, and flammability measurements. Thermal stability of these intumescent polyamide 11 nanocomposites was examined by TGA. Mechanical properties such as tensile, flexural, and elongation at break were measured. Flammability properties were also obtained using the Cone Calorimeter at an external heat flux of 50 kW/m2 and UL 94. UL 94 V0 rating was achieved by several intumescent PA11-clay nanocomposite formulations. Cone calorimetry data also showed a significant reduced of peak heat release rate by 72% with the intumescent PA11-clay formulations as compared to the PA11 control polymer. A synergistic effect was achieved with the nanoclays and conventional intumescent FR additives. TEM micrographs, physical, mechanical, and flammability properties of these novel nanocomposites will be presented in the paper.Based on flammability and mechanical material performance, selective polymers including polyamide 11 nanocomposites and control polyamide 11 will be cryogenically ground into fine powders for SLS RM processing. SLS specimens will be fabricated for flammability, mechanical, and thermal properties characterization.
9:00 PM - HH3.64
Perovskite and Composite Materials for Intermediate Temperatures Solid Oxide Fuel Cells.
T. Kharlamova 1 , Svetlana Pavlova 1 , V. Sadykov 1 , Galina Alikina 1 , Tamara Kriger 1 , Mezentseva Natalia 1 , Vitalii Muzykantov 1 , Andrei Boronin 1 , Vladimir Zaikovskii 1 , Arcady Ishchenko 1 , Vladimir Rogov 1 , Nikolai Uvarov 2 , Jorge Frade 3 , Christos Argirusis 4
1 , Boreskov Institute of Catalysis, Novosibirsk Russian Federation, 2 , Institute of Solid State Chemistry and Mechanochemistry, Novosibirsk Russian Federation, 3 , University of Aveiro, Aveiro Portugal, 4 , Clausthal University of Technology, Clausthal-Zellerfeld Germany
Show Abstract9:00 PM - HH3.65
Processing-Structure-Property Relationships of Polystyrene-Carbon Nanofiber Composites.
Arun Kota 1 , Hugh Bruck 1 , David Bigio 1 , Srinivasa Raghavan 2 , Dan Powell 3
1 Dept. of Mechanical Engr., University of Maryland, College Park, Maryland, United States, 2 Dept. of Chemical Engr., University of Maryland, College Park, Maryland, United States, 3 , NASA GSFC, Greenbelt, Maryland, United States
Show AbstractIn this paper, we report the processing-structure-property relationships of Polystyrene (PS) - Carbon Nanofiber (CNF) composites fabricated via high throughput Twin Screw Extrusion (TSE) and laboratory-scale Solvent Evaporation (SE). PS was chosen as the matrix polymer because of its suitability for both TSE and SE processing. The composites were prepared at 1, 3, 5, 7, 10, and 15 wt% of CNFs. The influence of TSE processing parameters such as screw speed and location of the filler feed port on the microstructure were studied. Isolated regions of very high CNF concentrations were observed in optical and scanning electron microscopy. The size and number of such regions decreased at higher screw speeds and when the CNFs were fed earlier in the process. The TSE and SE processed PS-CNF composites were subsequently characterized for their electrical conductivity, rheological properties, and quasi-static mechanical properties. While the SE processed composites exhibited an electrical percolation threshold of 5 wt%, the as-fabricated TSE processed composites did not show a consistent electrical conductivity up to 15 wt% of CNFs. Upon annealing, the extruded PS-CNF composites exhibited an increase in electrical conductivity due to relaxation of the surface structure of the extrudate that was imparted by the exit die. Furthermore, the conductivity increased with increasing annealing temperature and annealing time suggesting that the phenomena may be diffusion-related. Comparison of the microstructures also indicated that CNFs tend to stay preferentially below the surface for the extruded composites and annealing exposes the CNFs. Dynamic rheological measurements indicated the onset of a pseudo-solid like behavior at 5 wt% of CNFs due to percolation of the CNFs. Unlike electrical conductivity, the SE and TSE processed composites exhibited similar rheological behavior, indicating that the surface morphology may differ, but the bulk microstructure is similar. Using a power-law fit to the electrical conductivity, a ‘degree of percolation’ parameter was established and used to predict the dynamic rheological properties of the composite by treating it as a combination of two interpenetrating phases: a CNF reinforced polymer, and a pseudo-solid like network of percolated CNFs. Furthermore, comparison of normalized dynamic rheological parameters with normalized electrical conductivity showed the difference between rheological and electrical percolation. Finally, preliminary characterization of the quasi-static mechanical properties indicates a 100% increase in the tensile modulus, 45% increase in the tensile strength and 81% decrease in ductility at 10 wt% of CNFs compared to pure PS. The quasi-static bulk mechanical properties did not exhibit a strong dependence on the distribution of CNFs that was further confirmed by localized nanomechanical measurements.
9:00 PM - HH3.66
Rapid Modification of TiO2 Nanoparticle Surface with Highly Conformal Multilayer.
Hongfeng Yin 1 , Wenfu Yan 2 , Sheng Dai 1
1 Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun China
Show AbstractAn one-step rapid modification of TiO2 surface with highly conformal multi-layer silicon oxide was described. By employing surface sol-gel chemistry through a layer-by-layer growth approach and tris(tert-butoxy)silanol as precursor, the surface of anatase TiO2 nanoparticles was successfully coated with a highly conformal silicon oxide up to 20 layers in an one-step reaction. HRTEM studies indicated that silica coating failed to retain the conformability with the formation of silica aggregation between coated TiO2 nanoparticels when more SiO2 layers were deposited. The multilayer silica coating increased the phase transition temperature of anatase to rutile from 900°C to 1200°C, while the monolayer coverage of silica on the surface of the same substrate only led to the increasing of the phase-transition temperature to 1000°C. Our new methodology highlights a new avenue to selectively control the surface properties of oxide nanoparticles.
9:00 PM - HH3.67
Effects of Pigment and its Dispersion on UV Degradation of Epoxy and Acrylic Urethane Polymeric Systems.
Stephanie Watson 1 , Amanda Forster 1 , I-Hsiang Tseng 1 , Li-Piin Sung 1 , Justin Lucas 1 , Aaron Forster 1
1 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show AbstractTiO2 and other pigments/fillers are heavily used in building and construction applications. Generally, these components are added to increase the opacity and improve the appearance of a polymeric coating system. However, the addition of pigments has been found to change the properties of the polymer system, especially its durability. Basically, pigments can interact with their polymer binder in three different (but not mutually exclusive) ways: (a)Protect the resin from direct photochemical degradation. Some polymers are particularly susceptible to direct ultraviolet (UV) degradation, which has sufficient energy to break chemical bonds within the resin. In this case, the absorption of UV by TiO2 mitigates direct photochemical attack. The absorption of UV by the pigment continues and will lead to photocatalytic attack as well, but is an initially less favored process. (b)Degrade the resin by photocatalytic degradation. Radicals generated by the pigment oxidize the polymeric binder and is the process pigment manufacturers attempt to minimize via surface treatments of the pigment.(c)Physical interactions with the resin. Degradation of a coating can lead to chalking, which is the physical separation/exposure of the pigment. Another factor, which is particularly important, especially in binders susceptible to photochemical attack, is the relative degree of dispersion of the pigment particles. Well-dispersed pigments absorb more UV and provide more UV protection.The aim of the present study is to examine the effects of the type (i.e. surface treatment), the particle size, and concentration of pigment on the photodegradation of resin systems exposed on the Simulated Photodegradation by High Energy Radiant Exposure (SPHERE) at NIST. Two well-characterized polymer systems were studied; a less durable amine-cured epoxy and more durable acrylic urethane were chosen to compare the effects of the durability of the polymeric binder. The polymer and pigment were analyzed separately to gain an understanding of their contributions to chemical changes observed for the entire system (pigmented polymer system). Electron paramagnetic resonance spectroscopy (EPR) was used to follow the free-radical generation in the pigments and free-radical degradation in the pigmented polymers. Surface-sensitive analytical techniques, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were utilized to monitor the degradation reactions at the surface (10 nm – 500 nm) of the resins. Dispersion of the cured pigmented polymer films was characterized using a conventional SEM analysis. Laser scanning confocal microscopy (LSCM) was also to monitor the pigment –polymer near and sub-surface interactions before and after UV degradation. The results of these analyses are evaluated in context of pigment and polymer properties and pigment dispersion in the polymer system.
9:00 PM - HH3.68
Impact of Large-Scale Morphology on the Reinforcement of Nanocomposites.
Dale Schaefer 1 , Ryan Justice 1
1 Chemical and Materials Engineering, University of Cincinnati, Cincinnati , Ohio, United States
Show AbstractBy definition, nanocomposites display morphological features on the nanometer scale. Nanoscale particles, domains, tubes, sheets are evident by electron imaging techniques. What is less widely appreciated is that morphological features usually extend to much larger length scales. Often hierarchical relationships among various levels of structure occur such as particles aggregated into clusters that in turn form micron-sized agglomerates. Hierarchical morphologies that are often missed in imaging are evident in scattering experiments. Imaging and scattering data will be compared and contrasted for several classes of polymer-based nanocomposites including silica-filled elastomers, and carbon nanotubes and clays dispersed in solvents and polymers. Based on a combination of x-ray and light scattering, it is evident that all these systems are much more complex and more disordered than is generally appreciated. The reasons these features are often missed in imaging studies will be discussed.Depending of the property in question large-scale morphological features can be beneficial or detrimental. Regarding electrical properties, disorder can lead to reduced percolation thresholds. Regarding mechanical properties a drastic reduction in modulus enhancement is found in hard materials, but not soft. This reduction is traced to reduced aspect ratio of the native filler caused by abusive processing.
9:00 PM - HH3.69
Osteoblast Behaviors on Novel Self-assembled Helical Rosette Nanotubes and Hydrogel Composites for Bone Tissue Engineering.
Lijie Zhang 1 , Sharwatie Ramsaywack 2 , Hicham Fenniri 2 , Thomas Webster 1
1 Division of Engineering, Brown University, Providence, Rhode Island, United States, 2 National Institute for Nanotechnology and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
Show AbstractTo date, although traditional autografts and allografts have been standard methods to treat bone fractures and defects, the formation of biocompatible and injectable scaffolds at the site of bone fracture to induce new bone growth is still a promising method to repair bone defects considering their minimally invasive and osteoinductive features. Therefore, numerous research efforts in bone tissue engineering have focused on the development of novel bone-like scaffolds (including natural or synthetic polymers, ceramics, composites (i.e., polymers with ceramic fillers), etc.) in order to more successfully promote osteoblast adhesion and tissue integration at bone defect sites. In this study, a novel bone tissue engineering scaffold based on the self-assembled properties of helical rosette nanotubes (HRNs) and biocompatible hydrogels (specifically, poly(2-hydroxyethyl methacrylate)-pHEMA) was designed to fill bone fractures and repair bone defects. HRNs are a new type of organic nanotubes with a hollow core 11 Å in diameter, which originate from the self-assembly of DNA base pair building blocks (guanine-cytosine) in water. Moreover, since HRNs can significantly change their aggregation state and become more viscous based on heating or adding to serum free medium at body temperature, HRNs with biocompatible hydrogels may provide an exciting therapy to heal bone fractures as injectable bone substitutes. Two types of HRNs, one with a lysine side chain and the other conjugated to different amounts of RGD (arginine-glycine-aspartic acid) peptides on HRNs, were prepared and dispersed into hydrogels. Due to their nanometric features and the helical architecture of HRNs which biomimic collagen and other structures in the natural bone matrix, preliminary results showed that these HRNs can significantly improve osteoblast adhesion when combined with pHEMA hydrogels. Furthermore, 0.01 mg/ml HRNs with RGD side chains embedded in and coated on hydrogels can also enhance osteoblast attachment compared to 0.01 mg/ml HRNs with a lysine side chain embedded in and coated on hydrogels. Results showed an increasing trend of osteoblast adhesion on these scaffolds with more RGDs on HRNs. In addition, transmission electron microscopy demonstrated HRNs can form a network inside hydrogels. Long term osteoblast behaviors (such as differentiation and mineralization) will be presented on these novel nanotube/hydrogel composites. In this manner, nanostructured HRN hydrogels provide a promising alternative to repair bone defects considering the flexibility in the design of HRNs and their exceptional cytocompatibilty properties.
9:00 PM - HH3.70
Cellulose/titanium Dioxide/inorganic Pigment Composite Spherical Microbeads Prepared by Viscose Phase Separation Method and their Evaluation as Colored Materials.
Shoji Nagaoka 1 , Kenji Arinaga 2 , Seitaro Kobayashi 3 , Chikako Murata 4 , Masanori Nagata 1 , Makoto Takafuji 3 , Hirotaka Ihara 3
1 Materials Development Department, Kumamoto Industrial Research Institute, Kumamoto, Kumamoto, Japan, 2 , Kyushu Inoac Co. Ltd., Nagasu-machi, Kumamoto, Japan, 3 Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University, Kumamoto, Kumamoto, Japan, 4 Scientific Instrument Division, Sysmex Corporation, Kobe, Hyogo, Japan
Show AbstractCellulose/inorganic pigment, i.e. iron oxide series (red color), cobalt oxide series (blue and green color) and bariuma oxide series (yellow color) etc, composite spherical microbeads for environmental composite pigment were made by a phase-separation method using viscose and an aqueous solution containing sodium polyacrylate. The amount of TiO2 appearing on the surface of the spherical microbeads was found to depend on the surface electric property of the TiO2 powder used. The distribution of TiO2 particles (20 nm) on the composite spherical microbeads was found to relate to the electric repulsion between the CSS- group and TiO2. The narrower the zeta potential distribution of TiO2 particles, the more TiO2 particles were driven out from the cellulose xanthate domain. The removal of acetaldehyde gas was confirmed to depend on the amount of TiO2 particles on the surface of the cellulose. We also report our findings regarding the relationships between cellulose xanthate and the electronic characteristics of TiO2 particles used in the cellulose/inorganic material composite sphering process. These findings suggest that the location of TiO2 particles in cellulose microbeads is related to electric repulsion between the CSS- group and TiO2. The distribution of TiO2 particles onto composite spherical microbead surfaces was also evaluated by investigating the removal property of acetaldehyde gas. In addition, in order to develop color materials that can remove harmful substances from the environment, we succeeded in preparing cellulose/TiO2/inorganic pigment composite, i.e. Fe2O3, CoO-Al2O3, TiO2-BaO-NiO, TiO2-CoO-NiO-ZnO, spherical microbeads with both color function and photocatalytic property. We also investigated flowability of cellulose spherical beads, cellulose composite spherical microbeads, TiO2, inorganic pigment, particles and cellulose granular using powder rheometer. The relationship between surface properties of composite microbead and flowability were discussed. Although the composite spherical microbeads which loaded inorganic pigment particles on the surface showed much higher flowability than inorganic pigment alone, their flowability was lower than cellulose alone microbeads. Their behavior of flowability was similar to pattern of inorganic pigment particles, respectively. We tested the color-fastness of the cellulose/TiO2/inorganic pigment particles composite spherical microbeads by UV irradiation. The color showed no change in spite of longer irradiation, demonstrating that the inorganic pigment particles particles protected the cellulose matrix from photo-degradation. As results, their advantages are as follows: 1) handling is easy because the shape of microbead is spherical, 2) in spite of being color materials, the composite particles are photocatalytic and can aid in cleaning the environment 3) no photo-degradation of the cellulose matrix was found to occur against UV irradiation.
9:00 PM - HH3.71
Mechanical Properties of Thermoplastic Olefin (TPO) /Clay Nanocomposites.
Ruan Yonghong 1
1 Dept. Physical and Materials Science, City University of Hong Kong, HongKong China
Show AbstractAs engineering materials, thermoplastic elastomers (TPEs) exhibit excellent weather ability and outstanding ozone resistance. However, the drawbacks, e.g. poor strength properties at low temperatures and lower chemical resistance, limit the end of use application. To achieve an optimum mechanical properties, some thermoplastics (e.g. PP) and fillers (e.g. carbon black) have been incorporated into elastomer components (e.g. EPDM, SEBS), which results in reinforcing materials, i.e. thermoplastic Olefin (TPO).We focused on thermoplastic polyolefin (TPO) materials consisting of SEBS elastomer and polypropylene (PP), by changing the ratio of thermoplastics to elastomers. In addition, montmorillonite (MMT) is particularly attractive as reinforcement for the polymer because it has very large aspect ratio and is environmentally friendly, readily available in large quantities with low cost. In this study, thermoplastic olefin (TPO)/MMT nanocomposites were made with clay loadings of 0-1.5 wt % by a two-step compounding method. The X-ray diffraction (XRD) was used to determine the successfully intercalation of MMT into TPO system. The morphology of these TPO/MMT nanocomposites was investigated with atomic force microscopy (AFM) and scanning electron microscopy (SEM). These results show the distribution of dispersed-phase, e.g. PP nanocomposites, in SEBS matrix. With the increasing clay loading, the size of SEBS phase becomes smaller and the distribution of PP nanocomposites in SEBS matrix becomes finer. The increasing reinforcing effect of PP nanocomposites in SEBS matrix leads to improved mechanical properties. As a result, the Young’s modulus and the yields strength increase with the increasing clay loading. Also, the impact strength of TPO nanocomposites at low temperature increases. In addition, the fracture energy is highlighted by means of essential fracture of work (EWF) approaches. It was confirmed both the essential work of fracture, we, and the non-essential work of fracture, wp, increase with the clay loading in TPO systems.
9:00 PM - HH3.72
Thermal Diffusivity of Polyetheretherketone/nano Filler Composite.
Sung-Ryong Kim 1 , Dong Ju Kim 1 , MinHyoung Kim 1
1 Dept. of Polymer Sci. and Eng, Chungju National University, Chungju Korea (the Republic of)
Show Abstract9:00 PM - HH3.73
Carbon Nanotube/Copper Composite Coatings Fabricated by Cold Spraying.
Sung-Hee Kwon 1 , Dae-Yul Lee 2 , Dong-Yong Park 3 , Ae-Cheon Yoon 1 , Kee-Ahn Lee 1
1 School of Advanced Materials Engineering, Andong National University, Andong, Gyungbuk, Korea (the Republic of), 2 , Carbon Nano-material Tech., Pohang, Gyungbuk, Korea (the Republic of), 3 , Tae-Kwang Tech., Pohang, Gyungbuk, Korea (the Republic of)
Show AbstractCarbon nanotubes(CNTs) have outstanding mechanical, thermal, and electrical properties. Thus, by placing nanotubes into appropriate matrixes, it is postulated that the resulting composites will have enhanced properties. Cold spray can produce thick metal based composite coatings with very high density, low oxygen content and phase purity, which leads to excellent physical properties. In this study, CNT/copper composite coating layers were fabricated by cold spraying process. The precursor powder mixture, in which CNT filled into copper particle, was prepared to improve the distribution of the CNT in copper matrix. Pure copper coating was also conducted by cold spraying as a reference. Annealing heat treatment was applied to the coating to examine its effect on the properties of the composite coating. Microstructures of coatings were observed under optical microscope and FE-SEM, and macroscopic properties were evaluated by Vickers hardness, wear resistance test and electrical conductivity measurement. The hardness of CNT/copper composite coating represented similar value to that of pure copper coating. However, the composite coating exhibited superior wear resistance compared with the pure copper coating. It was importantly found that the electrical conductivity of the CNT/copper composite coating was increased from 14% for the standard condition to almost 55% in the optimized condition, taking annealed (500oC/1hr.) copper coating as a reference (100%). The microstructural evolution of CNT/copper coating was also investigated and related to the macroscopic properties.
9:00 PM - HH3.74
Novel Tunable Inorganic/Organic Hybrid Aerogels with High Mechanical Strength and Low Dust.
Ying Tang 1 , Wendell Rhine 1 , Je Kyun Lee 1
1 , Aspen Aerogels, Inc., Northborough, Massachusetts, United States
Show AbstractInvented by Kistler in 1931, silica aerogels are prepared by sol-gel processes and dried by the supercritical solvent extraction, a drying process that minimizes pore shrinkage and collapse. Since then, aerogel materials have become attractive due to their lightweight (down to 0.003g), high porosity (up to 99%), nanosized pores, and high surface area (up to 1500 m2/g) with numerous applications including thermal and sound insulation, radiation detectors, capture of cometary dust particles, and adsorbents. Regardless of their long history and the tremendous potential, silica aerogels have not been commercially available in large quantities mainly due to their intrinsic weak and brittle structure, which results in aerogels being easily broken and dusty. Aspen Aerogel, Inc. has reinforced aerogels with inorganic and polymeric fibers to make them in a flexible blanket form. In this presentation, we will present results of research conducted to further improve their mechanical properties. This research involved chemically reinforcing the aerogels by incorporating different bis trialkoxysilyl terminated urea-compounds as bridging units to form crosslinked inorganic/organic hybrid aerogels. Results will be presented to show that the structure and the properties of the resulting materials can be tailored by adjusting content and molecular weight/type of the bridging compound. Using this strategy, we successfully developed organic/inorganic hybrid aerogels that were either stronger (~20% enhanced compression moduli) or were ~10 times less dusty while maintaining their low thermal conductivities, low densities, nanosized pores, and high surface areas.
9:00 PM - HH3.76
The Synthesis with Periodical Twin and Superlattice Acicular Ni31Si12 Nanowires By a Vapor Condensation Method.
Chung-Yang Lee 1 , Chun-Wen Wang 1 , Kao-Feng Laio 1 , Ping-Hung Yeh 1 , Wen-Wei Wu 1 , Cheng-Lun Hsin 1 , Kuo-Wei Huang 1 , Ming-Yen Lu 1 , Wei-Fan Lee 1 , Lih-Juann Chen 1
1 Department of Material Science and Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractA acicular Ni31Si12 nanowires were successfully synthesized with a simply vapor phase deposition method at 650 oC. The diameters of tip and stem parts of the acicular nanowires are 20-40 nm and 60-100 nm, respectively. Periodically spaced twins were observed. The twins possess {01-5} twin plane and a periodicity of 0.91nm. A superlattice of four (01-5) planes stages was also observed. Both of periodically twin and superlattice are coexisted in a Ni31Si12 NW. The resistivity of the acicular Ni31Si12 NWs was measured to be 558 μΩ-cm by a two-terminal electrical measurement. The field-enhancement factor β were found to be about 596.
9:00 PM - HH3.8
Self-assembled Hollow Polyaniline/Au Nanospheres.
Lijuan Zhang 1 , Hui Peng 1 , Jing Sui 1 , Paul Kilmartin 1 , Jadranka Travas-Sejdic 1
1 , the University of Auckland, Auckland New Zealand
Show Abstract Polyaniline (PANI) nanostructures have attracted a great deal of attention because the high surface area of these materials is of interest for development of sensors and catalytic materials.Recently, it has been demonstrated that composite nanostructures of PANI and metals show significant enhancement of sensing and catalytic capabilities. A number of different methods have been used to prepare PANI/metal composites nanostructures. Among those, the procedure of ‘one-pot synthesis’ is the most attractive: in such procedure a gold salt acts both as an oxidant for aniline and as a source of metal atoms. To our best knowledge, there are no published reports on preparation of PANI-metal nanospheres. In this work, polyaniline/Au nanospheres were prepared in the solution of p-toluenesulfonic acid (p-TSA) by oxidative polymerization using gold (III) chloride trihydrate solution as the oxidant. The morphologies of the reaction products were measured by SEM and TEM. Their structural features were characterized by FTIR, Raman spectra and XRD. The presence of gold in the composites was confirmed by the electron diffraction and X-ray diffraction. The room temperature conductivity of PANI/Au composite was two orders of magnitude higher than that of PANI.The obtained PANI/Au-modified glassy carbon electrode showed high catalytic activity for the oxidation of ascorbic acid.
9:00 PM - HH3.9
Superparamagnetic Composite Colloids with Anisotropic Structures: Synthesis and Assembly.
Yadong Yin 1 , Jianping Ge 1 , Yongxing Hu 1
1 Department of Chemistry, University of California, Riverside, Riverside, California, United States
Show AbstractWe report the synthesis and assembly of superparamagnetic magnetite-polystyrene composite colloids with anisotropic structures. Magnetite colloidal nanostructures were first synthesized using a high-temperature hydrolysis process, and then used as seeds for the subsequent emulsion polymerization process. By controlling the interfacial tension between the seeds and the monomers, and the swelling and phase separation of the monomer in the growing polymer shell, we are able to produce magnetite-polystyrene composite particles with various geometric shapes, including isotropic core-shell spheres, anisotropic core-shell spheres, doublets and rods. The anisotropic structures show dramatically different self-assembly behavior than isotropic structures when they are subjected to an external magnetic field, producing unusual structures such as zig-zag chains. These colloidal composite particles, with superparamagnetic property and anisotropic structures, would allow a wide range of potential applications, for example, as active components for biosensors and building blocks for photonic bandgap materials.
Symposium Organizers
Sridhar Komarneni The Pennsylvania State University
Katsumi Kaneko Chiba University
John C. Parker Cabot Microelectronics Corporation
Paul O'Brien University of Manchester
HH4: Properties and Applications of Nanophases and Nanocomposites
Session Chairs
Tuesday AM, November 27, 2007
Room 302 (Hynes)
9:30 AM - **HH4.1
Ultrananocrystalline Diamond (UNCD) as a MEMS Material.
John Carlisle 1 , Nicolaie Moldovan 1 , Charles West 1 , Neil Kane 1
1 , Advanced Diamond Technologies, Inc., Romeoville, Illinois, United States
Show AbstractDiamond has long been recognized for its potential as a MEMS material due to its many outstanding bulk and surface properties. However, in this context diamond is also notorious for over-promising and under-delivering. Several recent studies have validated that the properties of diamond can be translated to superior device performance, ranging from diamond AFM probes that exhibit excellent wear resistance to RF MEMS resonators in which high acoustic velocities translate to high frequency (> 1 GHz) filters and time references with high quality factors and low insertion losses. Despite these encouraging results, technical barriers remain to commercialization of these devices due to the limitations of previous diamond thin film technologies, in particular scalability to large area deposition suitable for wafer-level production and the lack of reproducibility of the synthesis process itself.Recently, nanostructured diamond materials have emerged that show considerable promise to overcome many of the previous issues with incumbent technologies. In particular, the ultrananocrystalline diamond (UNCD®) technology developed at Argonne National Laboratory and being commercialized by Advanced Diamond Technologies, Inc. (ADT) exhibits a number of unique material and process attributes that make it attractive for many applications in which a thin, smooth diamond film would have value, including MEMS. UNCD films are phase-pure sp3-bonded carbon materials with no graphitic phases present and consist of diamond grains only 2-5 nm in size with atomically abrupt grain boundaries. UNCD films have nearly the same hardness and modulus of natural diamond or homoepitaxial diamond thin films but are much more easily integrated into thin film heterostructures typical of MEMS and related applications.The focus of this talk is to highlight some of the unique materials properties of UNCD relevant to MEMS and discuss work to develop a UNCD MEMS module that addresses head-on the twin technical barriers of scalability and reproducibility that have effectively blocked the technology from serious consideration by MEMS designers. ADT is working to elevate DOI (diamond-on-insulator) wafers to the same level of maturity that SOI (silicon-on-insulator) is today. ADT is also developing a number of UNCD MEMS devices that are enabled by this advance, including monolithic diamond AFM probes, RF MEMS filters and switches, and electrochemical MEMS for water purification and biosensors. The close correlation between nanoscale materials properties and device performance will be highlighted for each of these application areas.
10:00 AM - HH4.2
Transparent Nanocomposite containing ZnO Nanoparticles as Potential Material for Graded Refractive Index (RI) Applications.
Minhao Wong 1 , Katsumi Yamaguchi 2 , Ryotaro Tsuji 1
1 Frontier Materials Development Laboratories, Kaneka Corporation, Settsu, Osaka, Japan, 2 Kane Ace R&D Group, Performance Polymer Division, Kaneka Corporation, Takasago Japan
Show Abstract10:15 AM - HH4.3
Hot-wire Chemical Vapor Deposition of Crystalline Metal Oxide Nanoparticles.
A. Mahan 1 , Phil Parilla 1 , Kim Jones 1 , Se Lee 1 , Anne Dillon 1
1 , NREL, Golden, Colorado, United States
Show AbstractMetal oxide films which exhibit ion-electron insertion properties have a wide variety of applications, including electrochromic (EC) devices, gas sensors, and batteries. While films with a wide variety of structural properties, including amorphous films, have been studied for these applications, recent work has been devoted to the applications of crystalline nano-particles, due to their high surface area and short diffusion path for charge insertion (1). Previously, WO3 nano-powders were generated using the hot wire chemical vapor deposition (HWCVD) technique by evaporating a W filament heated to a temperature of ~ 1400C in a partial oxygen atmosphere (2). After deposition, the nano-powders were scraped off the walls of the quartz tube and were analyzed by x-ray diffraction, Raman spectroscopy, and Transmission electron microscopy (TEM). As the powders are slightly oxygen deficient, a unique electrophoresis technique can be used to rapidly deposit thin films from these nano-powders. In the present work, we describe the structural properties of these films as the deposition temperature, chamber pressure and oxygen partial pressure are varied. We then focus on the properties of the films deposited, with an oxygen partial pressure of 16%, at a deposition temperature (chamber pressure) of 300C (50 Torr), and detail the superior EC properties exhibited by this material (3). Finally, we compare and contrast the structural properties of the present WO3 films with those of other metal oxide material systems as we change the HWCVD deposition parameters in a similar fashion. These other materials systems include MoO3 and Va2O5, which have significant battery applications (4).(1). A.H. Mahan, P.A. Parilla, K.M. Jones, and A.C. Dillon, Chem. Phys. Lett. 413 (2005) 88.(2). P. Poizot, S. Laurelle, S. Grugeon, L. Dupont, and J-M. Tarascon. Nature 407 (2000) 496.(3). S-H Lee, R. Deshpande, P.A. Parilla, K.M. Jones, B. To, A.H. Mahan, and A.C. Dillon, Advanced Materials 18 (2006) 763. (4). A.C. Dillon et al., this conference.
10:30 AM - HH4.4
Flame-made TiO2-based Gas Sensors.
Alexandra Teleki 1 , Nada Bjelobrk 1 , Perena Gouma 2 , Sotiris Pratsinis 1
1 Department of Mechanical and Process Engineering, ETH Zurich, Zurich Switzerland, 2 Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York, United States
Show AbstractAnatase TiO2 nanoparticles were produced by flame spray pyrolysis (FSP) and characterized by transmission/scanning electron microscopy, X-ray diffraction, Raman spectroscopy and nitrogen adsorption [1]. Thick films of these powders were prepared by either drop-coating or doctor-blading and tested for sensing of acetone, isoprene, ethanol and CO at 300 - 500 °C in dry N2/O2. A high n-type sensor signal was recorded at ppm levels of the organic vapors with fast response and recovery times. No phase transformation or grain growth took place during sensor tests, demonstrating the high stability of the particles at these conditions. Furthermore, Nb- and Cu-doped TiO2 nanoparticles were made similarly. Niobium stabilized the anatase phase and retarded grain growth up to 600 °C. Copper promoted rutile formation as the anatase to rutile transformation was already observed just above 400 °C during post-synthesis calcination. This was accompanied by a segregation of large (> 100 nm) CuO crystals which were initially small (< 5 nm) asperities on the titania surface. Pure as well as doped TiO2 showed an n-type signal to CO and ethanol. Both dopants improved the sensitivity towards CO over that of pure TiO2. In contrast, for ethanol a high increase in sensitivity was observed only for Nb-doped TiO2. The measured sensor signals were correlated to mass spectrometer signals measuring the system’s off-gas. Differences in gas adsorption on the pure and doped TiO2 materials were investigated by FT-IR (DRIFTS) spectroscopy. [1] Teleki, A., S.E. Pratsinis, K. Kalyanasundaram, and P.I. Gouma, “Sensing of organic vapors by flame-made TiO2 nanoparticles”, Sens. Actuators, B, Chem 119, 683-690 (2006).
11:15 AM - HH4.5
Nanofiber Network Membranes for PEM Fuel Cells.
Olivier Arnoult 1 , Jonghyun Choi 2 , Ryszard Wycisk 2 , Kyung Min Lee 1 , Peter Pintauro 2 , Patrick Mather 1
1 Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2 Chemical Engineering, Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractA number of different polymers and polymer composite materials along with new membrane fabrication methodologies have been investigated to overcome the poor performance of perfluorosulfonic acid (PFSA) membranes at high temperature and low relative humidity. None of these approaches, however, has worked particularly well for a variety of different reasons. For example, the use of very high ion-exchange capacity polymers improved proton conductivity at reduced humidity but the resulting membranes were often brittle in the dry state (raising concerns of membrane/MEA processibility) with excessive swelling and poor mechanical properties when fully hydrated.The present contribution describes an entirely new approach for fabricating fuel cell membranes, where a three-dimensional, interconnected network of proton-conducting polymeric nanofibers (approximately 100 nm in diameter) is embedded in an inert/impermeable polymer matrix. The nanofiber network, occupying from 15 to 70% of the dry membrane volume, is composed of a high ion-exchange capacity (IEC) sulfonic acid polymer to ensure high water affinity and a high concentration of protogenic sites. The inert (hydrophobic) polymer matrix will control water swelling of the nanofiber (i.e., the diameter of the nanofibers will not change appreciably with temperature and relative humidity) and provide overall mechanical strength to the membrane, thus permitting the fibers to have a fixed-charge concentration much greater than that which is practical in a homogenous ion-exchange membrane (unlike other fuel cell membranes, the role of the polymer support matrix will be decoupled from that of the proton-conducting channels). The structure also ensures optimum utilization of percolation pathways of protogenic polymer (i.e., there will be no isolated high IEC polymer domains or any dead-end nanochannels within the inert polymer matrix).Our talk will describe the experimental techniques used to: (i) electrospin a sulfonated polymer into nanofibers, which are then collected into a mat of uniform thickness, (ii) densify the mat to increase the volume fraction of fibers, (iii) vapor weld fibers to create a 3-D interconnecting fiber network, and (iv) fill the void volume between welded fibers in a densified mat with an inert (water/gas impermeable) matrix polymer. We will report on the impact of fiber diameter, especially elevated temperature performance where capillary condensation afforded by the nanometer scale may enhance water retention and thus proton conductivity.
11:30 AM - HH4.6
Multifunctional Nanocomposite Plasma Coatings – Enabling New Biomaterials Applications.
Dawn Balazs 1 , Dakang Shen 2 , Stefanie Lischer 1 , Kathrin Grieder 1 , Giuseppino Fortunato 1 , M. Mokbul Hossain 1 , Enrico Koerner 1 , Peter Wick 1 , Dieter Haas 2 , Manfred Heuberger 1
1 Advanced Fibers, Empa, Swiss Materials Science & Technology, St. Gallen Switzerland, 2 Department of Fundamental Microbiology, University of Lausanne, Lausanne Switzerland
Show Abstract11:45 AM - HH4.7
Functionalized Photonic Crystal Sensor Elements based on Nanoporous Polymers.
Sung Jin Kim 1 , Elizabeth Nio 1 , Huina Xu 1 , Vamsy Chodavarapu 3 , Albert Titus 1 , Mark Swihart 2 , Alexander Cartwright 1
1 Electrical Engineering, University at Buffalo, the State University of New York, Amherst, New York, United States, 3 Department of Electrical and Computer Engineering, McGill University, Montreal, Quebec, Canada, 2 Department of Chemical and Biological Engineering, University at Buffalo, the State University of New York, Amherst, New York, United States
Show AbstractWe report the development of oxygen sensors using functionalized nanoporous polymer photonic bandgap structures. These integrated sensor elements provide a new platform for the development of low cost, low power, lightweight, robust, fast and small sensors. To this end, we demonstrate an approach to encapsulation of chemical and biological recognition elements within the porous polymer structures. This sensing platform is built on our recently demonstrated nanofabrication technique using holographic interferometry of a photo-activated mixture that includes a volatile solvent as well as monomers, photoinitiators, and co-initiators. The resulting structure is a nanoporous polymeric 1D photonic bandgap structure with the reflection property tuned for direct integrated into CMOS (Complementary Metal Oxide Semiconductor) optical sensor systems. These optical sensor systems include phototransistors, transimpedance amplifiers, and additional signal processing units to enhance the signal to noise of the detected signal. Combining the CMOS chip with the porous polymer reflection grating, we demonstrate a prototype oxygen sensor by encapsulating the fluorophore (tris(4,7-diphenyl-1,10-phenathroline)ruthenium(II) within the grating and measuring the changes in fluorescence intensity or lifetime (phase detection) in the presence of varying concentrations of oxygen.
12:00 PM - HH4.8
Colloidal Synthesis of Pure and Doped-BaF2 Nanoparticles and its Application as Filler in Polymer Nanocomposites.
Srivatsan Sathyamurthy 2 1 , Enis Tuncer 1 , Shafiq Bhuiyan 1 , Baohua Gu 1 , Mariappan Paranthaman 1
2 , The University of Tennessee, Knoxville, Tennessee, United States, 1 , Oak Ridge National Laboratory, Oak Ridge, TN, Tennessee, United States
Show AbstractNanomaterials have attracted great interest in recent years because of their unique properties. Inorganic fluoride nanoparticles have a number of unusual electrical, optical, and magnetic properties with a strong size and shape dependence. Alkaline earth fluorides (BaF2, CaF2 and SrF2) are dielectric fluorides which have a wide variety of potential applications in microelectronic devices. Additionally, these fluorides can potentially act as ideal host crystals for light amplification and laser materials when doped with rare-earth ions. These fluorides are cubic and have refractive indices that can be matched well with various glass and polymer matrices. The transparency of these fluorides in the visible and infra-red regions, and their stability make them an ideal candidate for use in nanocomposite materials. In our work, we have synthesized BaF2 nanoparticles using colloidal processing using trioctylphosphine oxide (TOPO) as the solvent and surfactant. These particles were found to be completely soluble in common organic solvents such as hexane or toluene, and fully crystalline. Using X-ray diffraction and transmission electron microscopy, the particles were found to be phase pure with an average particle size of 13 nm. The particles could be easily doped with rare-earth ions, and the doped particles exhibited photoluminescence in the visible range. These nanoparticles were incorporated into polymethyl methacrylate (PMMA) as filler material and the change in the dielectric properties of PMMA were monitored. Dielectric permittivity measurements were performed between 20 and 1 MHz on the temperature window 30-295 K. Dielectric breakdown data were measured at 77 K. Preliminary measurements indicate an enhancement in the dielectric properties of PMMA. In this paper an in-depth analysis of the dielectric properties of PMMA/BaF2 nanocomposites along with the effect of rare-earth doping on the properties of the BaF2 nanoparticles and the nanocomposites will be discussed. Supported by the U.S. DOE, Division of Materials Sciences and Engineering, Office of Science, and Office of Electricity Delivery and Energy Reliability. The research was performed at the Oak Ridge National Laboratory, managed by UT-Battelle, LLC for the USDOE under contract DE-AC05-00OR22725.
12:15 PM - HH4.9
Synthesis and Characterization of Amorphous SiC and SiOC Aerogel Composites for Use in High Temperature Thermal Protection Systems.
Owen Evans 1 , Decio Coutinho 1 , Kiranmayi Deshpande 1 , Hua Dong 1 , Wenting Dong 1
1 , Aspen Aerogels, Inc., Northborough, Massachusetts, United States
Show AbstractSince their discovery in 1931, silicate based aerogels have been used in a wide variety of thermal insulation applications. The utility of these novel solids as insulation is due primarily to their very large surface areas and porosity. In particular, the nanoporosity of these materials coupled with low bulk density affords the lowest thermal conductivity of any known solid. We have been particularly interested in exploiting this unique property to develop state-of-the-art thermal protection systems for use at high temperatures. However, the thermal insulating properties of standard silicate based aerogels degrade rapidly at temperatures exceeding 1000 °C. This loss in performance is due in large part to the loss of surface area and pore volume resulting from thermally induced viscous sintering. We have overcome these shortcomings by developing novel sinter-resistant SiC and SiOC composite aerogel formulations that exhibit excellent thermal and oxidative stability at temperatures exceeding 1000 °C, significantly outperforming standard silicate-based aerogels at elevated temperatures. This work will briefly describe the development, characterization and testing of these materials.
12:30 PM - HH4.10
Synthesis of Nanocrystalline Al-Mg Powders for Hydrogen Storage Applications.
Fereshteh Ebrahimi 1 , Mahesh Tanniru 1 , Sankara Sarma Tatiparti 1
1 Materials Science and Engineering, University of Florida, Gainesville, Florida, United States
Show AbstractMetal hydrides are promising materials for hydrogen storage on-board of vehicles. Considering the weight issue, hydrides of Al and Mg, such as magnesium hydride and magnesium alanate, are of great interest. Recent studies indicate that the kinetic of hydrogenation/dehydrogenation as well as the maximum capacity of hydrides increases significantly when the grain size is reduced to the nano-regime. Furthermore, increasing the surface area by reducing the metal powder size or creating porosity is demonstrated to enhance these properties. The objective of this study has been to fabricate nanocrystalline Al-Mg powders with various magnesium content and to investigate the evolution of phases as a function of composition. Electrodeposition technique using an organometallic based electrolyte was employed for synthesis of the powders. Detailed characterizations of the morphology, phases, grain size and composition of the deposits were conducted using SEM, XRD, TEM and EPMA techniques, respectively. We have been able to fabricate powders with compositions from pure Al to over 90% Mg. The Al-Mg alloy powders produced are highly porous and exhibit a hierarchical structure with the finest unit smaller than micrometer in size. Depending on composition, they consist of different proportions of supersaturated fcc-Al and hcp-Mg solid solutions. Compositional analyses suggest that the maximum solubility values of Al in hcp-Mg and Mg in fcc-Al are limited to approximately 20at% under the deposition conditions used in this study. In all cases the hcp-Mg solid solution nucleates over the fcc-Al phase. Both phases have grain sizes within the nano-regime. The supersaturated hcp-Mg phase was found to be highly unstable and the precipitation of intermetallics takes place at low temperatures and short exposure times. In this presentation the possible phase evolution mechanisms will be discussed.
12:45 PM - HH4.11
Temperature Dependent Sensitivity Inversion in SnO1.8:Pd Mixed Nanoparticle Layer Based CO Sensors.
Ivaturi Aruna 1 , Frank Kruis 1
1 Institute of Nano Structures and Technology (NST), Faculty of Engineering, University of Duisburg-Essen, Duisburg Germany
Show AbstractPd has been the widely exploited metal additive in SnO2 sensor research. The modifications in sensing of Pd doped SnO2 in various toxic and flammable gases have been well reported in literature. Of the various systems studied, the interaction of Pd doped SnO2 with CO, the most commonly studied system, is of great interest in the field of air quality control, combustion processes and engine emission (CO being one of the prominent part of the polluting agents of the atmosphere). CO is a reducing gas and it is generally accepted that for such a gas increase in conductance of SnO2 occurs. It was indeed observed for undoped and Pd-doped SnO2 powders, thick as well as thin films synthesized by various techniques.1 Recently, an interesting observation of humidity dependent sensitivity inversion towards CO has been reported in Pd (2 nm, 2.5-3.1 at%) surface doped SnO2 nanoparticles synthesized by organometallic approach.2This study reports a novel observation of temperature dependent inversion in CO sensitivity of the nanoparticle layers consisting of homogeneously mixed monodispersed Pd and SnO1.8 nanoparticles. CO sensors have been fabricated using monodispersed SnO1.8: Pd mixed nanoparticle layers synthesized using the novel gas phase synthesis using aerosol route3 and deposited using low pressure impaction on Si substrates with gold electrodes bonded to a DIL-24 chip carrier through gold bond wires. The Pd nanoparticle size (mobility diameter = 5-15 nm) and concentration (number concentration = 0-3%) has been varied keeping SnO1.8 nanoparticle size constant (20 nm). The sensing behaviour of the mixed nanoparticle layers towards different concentration of CO (10 ppb – 104 ppm) has been studied in the temperature range 200-400°C. The dilution of CO and measurement of the variation in electrical resistance of nanoparticle layers in different gas environments has been carried out by using a fully automated setup consisting of a system of mass flow controllers and a picoammeter with an internal voltage source. Enhanced sensitivity (to CO of as low as 10 ppb) has been observed with decrease in nanoparticle size (to 5 nm) in the samples mixed with Pd nanoparticles, as compared to samples without Pd nanoparticles which show no sensitivity to CO in ppb levels. In contrast to the conductivity increase in SnO1.8 in response to CO exposure in the absence of Pd, the mixed nanoparticle layers exhibit decrease in conductivity. With increase in the operating temperature (200 to 400°C) reversal in the sensitivity has been observed at higher CO concentrations. The observed behavior has been understood in terms of the electronic and physiochemical processes. 1M. Batzill and U. Diebold, Prog. Surf. Sci. 79, 47 (2005).2L. Erades, D. Grandjeans, C. Nayral, K. Soulantica, B. Chaudret, P. Menini, F. Parret and A. Maisonnat New J. Chem. 30, 1026 (2006).3M.K. Kennedy, F.E.Kruis, H.Fissan, H. Niehaus, A.Lorke and T.H. Metzger, Sensors and Actuators B 108, 62 (2005).
HH5: Processing of Nanomaterials and Thin Films
Session Chairs
Sridhar Komarneni
Greta Patzke
Tuesday PM, November 27, 2007
Room 302 (Hynes)
2:30 PM - **HH5.1
Targeted Synthesis of Nanostructured Transition Metal Oxides.
Greta Patzke 1 , Ying Zhou 1
1 Institute of Inorganic Chemistry, University of Zurich, Zurich Switzerland
Show AbstractThe development of a future nanotechnology requires clear-cut and efficient synthetic pathways to building blocks for nano-device fabrication, such as anisotropic particles with nanoscale dimensions [1]. Transition metal oxides play an essential role in these developments, because they exhibit a multitude of key properties that lead to their manifold applications, for example in catalysis, photochromic systems, battery materials and sensor technology [2]. In order to fabricate nanostructured transition metal oxides in a controlled manner, we apply a variety of preparative techniques, including conventional or high-throughput hydrothermal syntheses and microwave- or ultrasound-assisted processes. Moreover, the elucidation of selected mechanistic pathways to key materials is in the focus of our investigations as well as their characterization, e.g. in the field of battery and sensor technology.For this purpose, we prepare anisotropic nanoscale molybdenum and tungsten oxides. Their transformation into mixed Mo/W-oxides benefits from morphological and structural synergisms, thereby leading to materials with superior catalytic and sensor properties.The particle shape of nanostructured molybdenum and tungsten oxides can be controlled through the use of alkali chlorides. We have tracked down the different growth mechanisms for molybdenum oxide nanorods and nanoscale hexagonal alkali tungstates through complementary in situ XRD/EXAFS techniques: Whereas the anisotropic molybdenum oxides grow within a few minutes via a dissolution-precipitation sequence [3], the alkali tungstates are formed through an hour-scale nucleation controlled mechanism [4].Consequently, the kinetics of mixed Mo/W-oxide formation displays an intermediate reaction rate, following a nucleation controlled process. Moreover, their nanoscale morphology can be tailored quite efficiently with alkali chlorides to yield a wide spectrum of mixed alkali Mo/W-oxide materials.Furthermore, the fabrication of hybrid materials from fibrous transition metal oxides and bio-macromolecules opens up unexplored research areas. Chitosan is a particularly effective additive for the formation of bio-inorganic composites. We therefore investigate its influence on the hydrothermal growth of molybdenum oxide rods and mixed nanostructured Mo/W-oxides.[1] C. N. R. Rao, A. Müller, A. K. Cheetham (Eds.), The Chemistry of Nanomaterials, Wiley-VCH, Weinheim, 2004.[2] C. N. R. Rao, F. L. Deepak, G. Gundiah, A. Govindaraj, Prog. Solid State Chem. 2003, 31, 5.[3] A. Michailovski, J.-D. Grunwaldt, A. Baiker, R. Kiebach, W. Bensch, G. R. Patzke, Angew. Chem. Int. Ed. 2005, 44, 5643.[4] A. Michailovski, R. Kiebach, W. Bensch, J.-D. Grunwaldt, A. Baiker, S. Komarneni, G. R. Patzke, Chem. Mater. 2007, 19, 185.
3:00 PM - HH5.2
The Formation and Characterization of Self-Assembled Nanoscale Vanadium Layered Compounds by Hydrothermal Reaction.
Chunmei Ban 1 , Natalya Chernova 1 , M. Stanley Whittingham 1
1 Chemistry, SUNY at Binghamton, Binghamton, New York, United States
Show AbstractVanadium oxide – poly (methyl methacrylate) (PMMA) composite fibers were synthesized by electrospinning method using vanadium oxide triisopropoxide and PMMA as starting materials. Upon mild hydrothermal treatment using either acetic acid or lithium acetate-acetic acid buffer solution the fibers were converted in vanadium oxide nanofibers or lithium intercalated vanadium oxide nanorods, respectively. The lamellar structure similar to δ-phase V4O10 is found in both nanosized products by x-ray powder diffraction. The interlayer distance is 10.4 Å in the lithium vanadium oxide and 11.4 Å in the vanadium oxide. The structure, composition and vanadium oxidation state were further studied by FTIR, TGA, DCP-AES, chemical analysis and magnetic properties. The possibility of the morphology control at the electrospinning step is demonstrated by TEM and SEM studies. The assembling of vanadium and lithium-vanadium phosphates with attractive morphologies were also performed by hydrothermal treatment of electrospun fibers including (NH4)H2PO4 as phosphate precursor. Their composition, structure, and magnetic properties are characterized. The effect of synthesis conditions at both electrospinning and hydrothermal steps on the formation nanoscale materials is discussed. This work is supported by the National Science Foundation through grant DMR-0705657.
3:15 PM - HH5.3
Reactivity of Metal Nanoparticles in Multi-metal Systems: Insights into Low Temperature Solution Synthesis of Intermetallic Nanomaterials.
Brian Leonard 1 , Raymond Schaak 1
1 Chemistry, Texas A&M University, College station, Texas, United States
Show AbstractThe ability to synthesize multi-metal intermetallic compounds as nanocrystals has important implications for many fundamental scientific studies and emerging technological applications. While exploring multi-metal systems, we recently discovered a new ordered ternary intermetallic compound, AuCuSn2, that could be synthesized as nanocrystals using a low temperature solution technique. Further investigation of the reaction revealed that it proceeds through a unique pathway with four distinct stages: (1) galvanic reduction of Au(III) to Au(0) nanoparticles with concurrent oxidation of Sn(II) to Sn(IV) (as a SnO2 shell), (2) formation of NiAs-type AuSn along with Cu and Sn nanoparticles using NaBH4 reduction, (3) aggregation and thermal interdiffusion to form a ternary alloy, and (4) nucleation of the ordered intermetallic compound AuCuSn2. The proposed pathway was tested by reacting AuSn nanoparticles with Cu nanoparticles formed ex-situ, and AuCuSn2 was formed upon heating. Further investigations into the reactivity and kinetics of chemical transformations involving metal nanoparticles have lead to the idea of orthogonal reactivity in multi-component nanoparticle systems, which would allow phase (or metal) specific reactions to take place within a system of multiple metal nanoparticles. This chemistry could have potential future applications in the formation of advanced nanocomposites and nanoelectronic materials.
3:30 PM - HH5.4
Synthesis of Platinum Nanoparticles with Size and Shape Optimized for Oxygen Reduction Reaction.
Chao Wang 1 2 , Shouheng Sun 2 , Tetsunori Koda 3 2 , Hideo Daimon 3
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 Chemistry, Brown University, Providence, Rhode Island, United States, 3 Development & Technology Division, Hitarchi Maxell, Ltd., Tsukubamirai, Ibaraki, Japan
Show AbstractTo enhance the activity and reduce the usage of the Pt catalyst for oxygen reduction reaction (ORR) is one of the key solutions to the fuel cell technology for practical applications. Here we report a simple high-temperature organic phase synthesis of Pt nanoparticles (NPs) with size and shape control. Platinum acetylacetonate, Pt(acac)2 was reduced in an organic solvent in the presence of oleic acid and oleylamine as surfactants to synthesize spherical Pt NPs. Pt nanocubes and truncated octahedrons were obtained by adding a trace amount of Fe(CO)5 to the reaction mixture. The size of Pt NPs was controlled from 3 nm to 12 nm by tuning the ratio of precursor to surfactant. Systematic cyclic voltammetry and rotational ring disk electrode (RRDE) studies on these Pt NPs show that the Pt nanocubes, with the presence of dominant (100) phase, have much higher catalytic activity than spherical or other shaped Pt NPs. The Pt nanocubes have specific activity over 3-fold higher than that from the commercial Pt catalyst. X-ray photoelectron spectroscopy (XPS) analyses revealed that the enhanced catalytic activity of Pt nanocubes came from the lower energy level of d-band electrons on Pt (100) surface than other Pt planes (like (111) and (110)). Our approach provides a simple way of producing active Pt nanocube catalyst with enhanced ORR catalysis for fuel cell applications.
4:15 PM - **HH5.5
Electronically Tunable Nanomaterials.
Horst Hahn 1 , Subho Dasgupta 1 , Robert Kruk 1
1 Institute for Nanotechnology, Forschungszentrum Karlsruhe GmbH, Kalsruhe Germany
Show AbstractThe properties of materials are typically controlled in a static manner by the microstructure. This implies control of the grain size, defect concentration, structure and metastability. As long as the microstructure does not change during the use of the material, the properties of the material are fixed, or irreversible. In semiconducting materials, properties can be tuned by the application of an external field due to the space charge regions which extend far from the interfaces. In metallic systems, this effect cannot be observed unless the dimensions of the structures are in the nanometer regime. The reason for this different behaviour is the small spatial dimension of the space charge regions due to the effective screening of the induced charges by the conduction electrons. In nanoporous metals and thin films exposed to appropriate electrolytes, it has been demonstrated that substantial changes of physical properties can be induced by the application of a potential between the nanostructured metal and a counter electrode. Examples of our own work on the changes of the electrical resistivity of thin Gold films and nanoporous Gold will be presented. In addition, some results of work reported in the literature will be summarized. The experimental results can be interpreted by surface stress effects and the change of the electron density distribution at the interface of the metal and the electrolyte.
4:45 PM - HH5.6
Unexpected Phase Formation upon Gas Nitriding of Nanocrystalline Iron Thin Films.
Markus Wohlschloegel 1 , Udo Welzel 1 , Eric Mittemeijer 1
1 , Max Planck Institute for Metals Research, Stuttgart Germany
Show Abstractα-Fe thin films of similar thicknesses, but different average lateral crystallite sizes – 80 nm and 400 nm – have been deposited onto <001> oriented single crystalline Al2O3 substrates by molecular beam epitaxy. During gas nitriding of these films the thermodynamic nitriding parameters have been chosen such that only the phase γ’-Fe4N1-x should develop. Cross sections of the as-deposited and the through-nitrided films have been cut and visualized by focused ion beam microscopy. X-ray diffraction analysis of the nitrided films revealed that besides γ’-Fe4N1-x another phase – ε-Fe3N1+x – has developed upon nitriding of the iron film exhibiting the smaller crystallite size. This phenomenon did not occur during nitriding of the coarse grained iron film and bulk iron specimens. A thermodynamic interpretation of this finding is given on the basis of the Gibbs-Thomson effect, calculating the Gibbs energy as a function of the nitrogen content in the binary system iron – nitrogen. As a side result the grain boundary energy in the γ’-Fe4N1-x thin film has been determined to be 1.6 J/m2.
5:00 PM - HH5.7
Dry Lithiation Study of Molybdenum Trioxide Thin Films Prepared by Electron Beam Evaporation.
Gisia Beydaghyan 1 , Pandurang Ashrit 1
1 Département de physique et d'astronomie, Université de Moncton, Moncton, New Brunswick, Canada
Show AbstractTransition metal oxides such as tungsten trioxide (WO3), molybdenum trioxide (MoO3), and titanium dioxide (TiO2) are known for their electrochromism, defined as reversible coloration with the intercalation/de-intercalation of electrons/ions or atoms. Among the applications of electrochromism are smart windows, variable reflectance mirrors, and displays. Molybdenum trioxide films exhibit pronounced electrochromism, and in addition show photo- and thermochromic properties. Here, we present work on as-deposited and annealed molybdenum trioxide films prepared by electron beam deposition in a vacuum chamber with a base pressure of 3×10-6 Pa. Samples were annealed after deposition by being kept at a temperature of 400 °C for one hour under atmospheric pressure. Films are characterized with spectrophotometry, atomic force microscopy, and spectroscopic ellipsometry. Electrochromic properties are investigated with dry lithiation – a technique developed in our laboratory. As-deposited films show a granular morphology, with typical grains of 10 – 50 nm diameter. These samples show pronounced coloration upon intercalation of lithium, with maximum coloration in the visible region. Atomic force micrographs of annealed films show the formation of large grains (0.5 – 4 μm), and also indicate the presence of a layered morphology. The grains contribute to a large diffuse component in the transmission and reflection spectra of the films. These samples show less coloration compared to as-deposited films, as well as saturation of coloration at lower values of inserted charge. We compare these results with previous works on electrochromism of molybdenum trioxide films, and further discuss the potential of porous nanostructured films prepared by the technique of glancing angle deposition.
5:15 PM - HH5.8
Nanostructured Thin Film Oxide by Oblique Reactive RF Sputtering.
S. Barron 1 , R. van Dover 1 , L. Schneemeyer 2 , D. Werner 3
1 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States, 2 Department of Chemistry, Rutgers University, Newark, New Jersey, United States, 3 , Los Alamos National Labs, Los Alamos, New Mexico, United States
Show AbstractNanostructured thin film oxides have a variety of applications, ranging from the tunability of optical properties to catalytic activity to sensor applications. We report on a simple, one step process to form a thin film of tantalum oxide with a nano-sized void structure. The Ta2O5 film was reactively sputtered RF from a metallic target; to effect the desired void structure, we have placed the substrate 90° off-axis to the sputter target (parallel to the sputter gun axis). Off-axis substrates are not subject to the intense oxygen ion bombardment that one obtains for the traditional on-axis placement of the substrate during reactive RF sputtering. The lack of ion bombardment limits the surface mobility of depositing species and leads to a structure of columnar voids, ~ 2-10 nm, as observed using high resolution transmission electron microscopy. There are no observable voids in on-axis sputtered Ta2O5; additionally, in the off-axis configuration, we find that the void structure can be eliminated by applying a deliberate, controlled RF bias to the substrate, which generates a flux of Ar+ ions. The dielectric properties of ion-bombarded films suggest that they are both amorphous and dense, implying that ion-bombardment offers an essential control over the void structure. In the off-axis non-bombarded configuration, the void structure varies with distance from the sputter gun, as inferred from the variation in capacitive response to humidity changes. We have observed a four-fold capacitance change in the oxide when exposed to humidity changes. The capacitance change is attributed to a hopping conductivity of charge carriers along water molecules adsorbed within the voids; the conductivity is found to be thermally activated with an energy of 370 meV. Further characterization for humidity sensor applications is on-going. Our simple thin film deposition technique enables a nano-sized void structure, similar to those explored for sensor applications or for a tunable index of refraction. The void structure observed can be controlled by several simple process modifications, such as substrate position and RF bias.
5:30 PM - HH5.9
Stabilization of Nanostructures by Grain Boundary Doping - Experiments and Molecular Dynamics Simulations.
Stefan Mayr 1 , Dennis Bedorf 1
1 I. Physikalisches Institut, Universitaet Goettingen , Goettingen Germany
Show AbstractCoarsening of nanocrystalline systems at elevated temperatures can be prevented by adding small amounts of impurities to grain boundaries and interfaces, as found in a variety of instances. For the model systems, CuBi and CuAg, we investigate atomic-scale mechanisms, which underlie stabilization of the nanophase in the presence ofan open surface, using experiments, molecular dynamics computer simulations and thermodynamic considerations. We find that the occurrence of locally negative grain boundary free energies due to dopants is sufficient to frustrate grain growth via a metastable equilibrium. Our treatment can be generalized to other systems with large enough segregation.[1] S.G. Mayr and D. Bedorf, Phys. Rev. B 2007 (in press)Financially supported by the DFG-SFB 602, TP B3.
5:45 PM - HH5.10
Synthesis and Structural Characterization of Three-Dimensionally-Epitaxially-Strained Oxide Thin Film Nanocomposites.
Jeffrey Eastman 1 , Guo-Ren Bai 1 , Krishna Uprety 2 , Peter Baldo 1 , Dillon Fong 1 , Orlando Auciello 1 2 , Boyd Veal 1 , Paul Fuoss 1 , Loren Thompson 1 , IL-Seok Kim 1
1 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States, 2 Center for Nanoscale Materials, Argonne National Laboratory , Argonne, Illinois, United States
Show AbstractIn this presentation we will describe the synthesis and structural characterization of novel coherently-strained epitaxial thin film two-phase oxide nanocomposites. These nanocomposites are produced by co-deposition of phase-separating materials with related structures and closely-matched lattice parameters. Through control of growth conditions it is possible to synthesize either nanoparticles or nanopillars of one material dispersed in a matrix of another. Such structures can exhibit emergent behavior due to proximity effects associated with the multitude of strained heterointerfaces in the system.These studies were inspired by recent pioneering work by Moshnyaga et al. [1], who demonstrated that epitaxially-strained (Lax,Ca1-x)MnO3 (LCMO) nanoparticles in an MgO thin film matrix can be created by co-deposition of these two materials onto single crystal MgO substrates, resulting in large changes in LCMO magnetotransport properties. Zheng and co-workers extended this synthesis strategy [2] by synthesizing quasi-hexagonally-arranged multiferroic 3D nanostructures consisting of ferromagnetic CoFe2O4 nanopillars embedded in a ferroelectric BaTiO3 matrix. In the current study, we have focused on synthesis of two new nanocomposite systems where interesting and novel ionic and/or electronic conduction behavior occurs. MgO-Mg2TiO4 was chosen as a model system that, due to the fact that there are only two cation species, is ideal for determining the effects of processing parameters such as growth temperature, growth rate, composition, and misfit-induced strain on nanocomposite size, morphology, and self-organization. Nanocomposites are prepared by metal-organic chemical vapor deposition (MOCVD) onto (001) MgO substrates. The second system that we will discuss is yttria-stabilized zirconia (YSZ)-In2O3. Epitaxial nanopillars of YSZ in an In2O3 matrix (or vice versa) exhibit interesting anisotropic conduction behavior since YSZ is an excellent ionic conductor with limited electronic conduction, while doped In2O3 is a well-known electronic conductor. In this case, samples are prepared by RF sputter deposition onto YSZ (001) single crystal substrates. For both systems the structure, composition, and morphology of the nanocomposites determined using AFM, SEM, and X-ray scattering techniques will be described. The implications of these results on the possibilities for obtaining desirable proximity-induced enhancements in conductivity in nanopillar heterostructures will be discussed. This work is supported by the U. S. Department of Energy under Contract No. DE-AC02-06CH11357.1.V. Moshnyaga et al., Nature Mater. 2, 247 (2003).2.H. Zheng et al., Science 303, 661 (2004).
Symposium Organizers
Sridhar Komarneni The Pennsylvania State University
Katsumi Kaneko Chiba University
John C. Parker Cabot Microelectronics Corporation
Paul O'Brien University of Manchester
HH6: Nanoporous Materials
Session Chairs
Wednesday AM, November 28, 2007
Room 302 (Hynes)
9:30 AM - **HH6.1
Highly Ordered Mesoporous Organosilicas with Integral Organic Functionality.
Shinji Inagaki 1 2
1 , Toyota Central R&D labs., Inc., Aichi Japan, 2 , CREST, JST, Kawaguchi Japan
Show AbstractPeriodic mesoporous organosilicas synthesized from bridged organosilanes [(R'O)3Si-R-Si(OR')3] by using the supramolecular templating method of surfactant have homogeneous distribution of organic fragments and silica moieties (≡O3Si-R-SiO3≡) within the framework. The materials have uniform pores, higher stability, and control on morphologies and potential application in a variety of areas, including optoelectronics, sensing, enantoselective separation and catalysis. The main object of contemporary hybrid mesoporous materials synthesis is to control the geometry of a material at the molecular level of design. We have described the surfactant-mediated synthesis of phenylene- and biphenylylene-silica hybrid mesoporous materials with crystal-like pore walls possessing well-oriented phenylene and biphenylylene arrangements. The addition of crystallinity to the pore wall of mesoporous materials has long been sought after and is a most important development in this research field.The extension of organic linker in crystal-like mesoporous organosilica is quite interesting from both of practical and scientific viewpoints. We have succeeded in the synthesis of novel mesoporous organosilicas including methylcarbazole, naphthalene, and anthracene as organic linkers. They were prepared from 100% of organosilane precursors in the presence of surfactant under a basic or acidic condition. The organosilane precursors were newly synthesized by rhodium-catalyzed disilylation. X-ray diffraction patterns showed strong diffraction at low angle below 5 degree due to the ordered mesostructures. The naphtharene-silica material particularly showed the highly ordered mesostructure and also shows molecular-scale periodicity, 0.98 nm, within the pore walls. We have also functionalized the mesoporous aromatic-silica hybrids by attaching functional groups such as sulfonic group (-SO3H) and amine group (-NH2) for the applications of catalysis and electrolyte for fuel cells. Mesoporous biphenylylene-silica (BP-HMM) film was prepared by dip-coating of sol solution on the glass substrate. The film was transparent with a thickness of approximately 200 nm. XRD patterns showed some reflections in low angle region due to a mesoscopically ordered structure. BP-HMM-film showed absorption band at λ=267 nm, which was almost the same to BTEBp monomer. The fluorescence spectra showed the strong emissions at λ=375 nm due to the biphenylylene groups in the frameworks, which was largely shifted from the emission band (λ=315 nm) of BTEBp monomer. These results strongly suggest that the emission is due to the excimer formation of biphenylylene groups. Fluorescence quantum yield of BP-HMM-film was Φ=0.56, which was larger than those of BTEBp monomer (Φ=0.35) and biphenyl (Φ=0.10).
10:00 AM - HH6.2
Facile Synthesis of Mesoporous Carbons through Co-operative Self-assembly of Resorcinol/formaldehyde and Block Copolymers.
Xiqing Wang 1 , Chengdu Liang 1 , Sheng Dai 1
1 Chemical Sciences Division, Oak Ridge National Lab, Oak Ridge, Tennessee, United States
Show AbstractA very simple and highly reproducible synthetic route of mesoporous carbons (both worm-like and highly ordered hexagonal meso-structures) has been developed through co-operative self-assembly of resorcinol/formaldehyde and block copolymers (e.g., F127 and F108). One key factor to make well-defined mesoporous carbons is to use highly acidic condition (e.g., 1.5 M), which enables fast reactions of resorcinol and formaldehyde to generate phenolic prepolymers and facilitates their in situ organization with block copolymers to form meso-structured nanocomposites. The typical mesoporous carbon resulted has a BET surface area of 500 m2/g, a high pore volume of 0.5 cm3/g, and a narrow pore size within 6-7 nm. Such mesoporous carbon materials are highly thermally stable and can undergo graphitization under 2600 °C without obvious structural degradation. This method, to be another synthetic feature, allows easy incorporation of different functionalities with uniform mesoporisity into carbon materials, e.g, for the formation of magnetically separable mesoporous carbons and mesoporous carbon/crystalline metal carbide composites, which will show promising properties for separation and catalysis, respectively.
10:15 AM - HH6.3
Synthesis of Mesoporous Ferroelectric Oxides.
Ru Zhong Hou 1 , Paula Ferreira 1 , Paula Vilarinho 1
1 Ceramic and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro Portugal
Show AbstractPerovskite ferroelectrics have been widely investigated in the form of ceramics, films and single crystals. It is accepted that the macroscopic physical properties of ferroelectrics are not only determined by their intrinsic nature but also influenced by the morphology of the materials. Some emerging topics based on morphology control, such as one-dimensional structured ferroelectrics [1], ferroelectric inverse opals [2,3] and mesoporous ferroelectrics [4], provide novel applications and further understanding of the well-known ferroelectric materials. Mesoporous films of SrTiO3 were first prepared via a template self-assembled method by Grosso et al. [4] Although the described process seems to be promising, it is difficult to reproduce due to the commercial unavailability of the copolymer used as template and which is, according to the authors, the responsible for the mesophase formation.In the present work, a facile route to directly synthesized mesoporous BaTiO3 crystallites with single-crystalline framework was developed. A cationic surfactant cetyltrimethylammonium chloride (C16TMAC) and a non-ionic block copolymer Pluronic PE 10300 commercially available were used as structure-directing agents. The materials were characterized by powder X-ray diffraction, SEM, TEM and low temperature nitrogen adsortion-desorption isotherms. Clear wormhole-like mesoporous structures were observed by TEM. HRTEM gave evidence of the single-crystalline nature of the framework around the mesoporous. For the sample prepared with C16TMAC, the pore size distribution peaked at 1.5 nm and a specific surface BET area of ca. 50 m2/g and a 27% volume ratio of mesopores were obtained. Such data suggested the existence of closed or inaccessible pores for nitrogen molecules in the present sample. Samples prepared with Pluronic PE 10300 had larger mesopore size and higher specific surface area than those prepared with C16TMAC [5]. The effect of the preparation conditions on the pore structure and order of the barium titanate single crystallites are presented and discussed. The relations between the mesostructure and macroscopic properties of BaTiO3 are established. BaTiO3 with optimised pore size and ordering are very promising as photonic crystals or electrofunctional nano-composite materials.References[1].J. J. Urban, W. S. Yun, Q. Gu and H. Park, J. Am. Ceram. Soc. 124, (2002) 1186.[2].I. Soten, H. Miguez, S. M. Yang, S. Petrov, N. Coombs, N. Tetreault, N. Matsuura, H. E. Ruda and G. A. Ozin, Adv. Funct. Mater. 12 (2002) 71.[3].B. Li, J. Zhou, L. Li, X. J. Wang, X. H. Liu and J. Zi, Appl. Phys. Lett. 83 (2003) 4704. [4].D. Grosso, C. Boissière, B. Smarsly, T. Brezesinski, N. Pinna, P. A. Albouy, H. Amenitsch, M. Antonietti and C. Sanchez, Nature Mater. 3 (2004) 787.[5].R. Z. Hou, P. Ferreira and P. M. Vilarinho, A Facile Route for Synthesis of Mesoporous Barium Titanate Crystallites, accepted in Microporous and Mesoporous Materials
10:30 AM - HH6.4
AM-6: A Microporous 1-Dimensional Ferromagnet.
Russell Howe 1 , Rachel Yeates 1 , Abbie Mclaughlin 1 , Morag Murdoch 1
1 Chemistry, University of Aberdeen, Aberdeen United Kingdom
Show AbstractAM-6 is a microporous vanadosilicate zeolite isostructural with the titanosilicate zeolite ETS-10. These novel structures contain one-dimensional chains of VO6 or TiO6 octahedra connected via silicate tetrahedra, forming a three dimensional 12-ring zeolitic pore structure. [1,2] The TiO6 chains in ETS-10 form semiconductor nanowires [3], which have been extensively studied for their photocatalytic reactivity [4,5]. The V(IV) in AM-6 is paramagnetic, unlike Ti(IV) in ETS-10. As a result, AM-6 has interesting magnetic properties. In this paper, we will describe the structural characterisation of the VO6 chains by EXAFS and vibrational spectroscopy, and report EPR and magnetic susceptibility data showing that the V(IV) ions in the chains are ferromagnetically coupled. Below 50 K, AM-6 behaves as a one dimensional ferromagnet.This is the first example of a nanoporous one-dimensional ferromagnet.We will discuss the possible modulation of the magnetic properties with molecules adsorbed in the zeolite pores, and the interaction between the magnetic properties and the semiconducting properties of the VO6 chains.References:1.Anderson M.W., Terasaki O., Ohsuna T., Malley P.J.O., Phillipou A., Mackay S.P., Ferriera A., Rocha J., Lidin S., Phil.Mag.B 1995, 71, 813.2.Rocha J., Brandao P., Lin Z., Anderson M.W., Alfreddson V., Terasaki O., Angew.Chem.Int.Ed. 1997, 36, 100.3. Bordiga S., Palomino G.T., Zecchina A., Ranghino G., Giamello E., Lamberti C., J.Chem.Phys. 2000, 112, 3859.4. Xamena F.X.L., Calza P., Lamberti C., Prestopino C., Damin A., Bordiga S., Pelizetti E., Zecchina A., J.Am.Chem.Soc. 2003, 125, 2264.5. Krisnandi Y., Howe R.F., Applied Catal. A 2006, 307, 62.
11:15 AM - HH6.5
Optical Properties of Double-Decker-Shaped Poly (Silsesquioxane.)
Akira Watanabe 1 , Shohei Tadenuma 1 , Tokuji Miyashita 1
1 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai Japan
Show AbstractThe POSS (polyhedral oligomeric silsesquioxane) has a nanometer-sized silica-like cage structure functionalized with various kinds of organic groups. The POSS as a building block provides elegant designs and the controllable reaction for organic-inorganic hybrid materials. The hybridization between organic and inorganic moieties can be controlled by the chemical reaction of the functionalized POSS. In this study, we report the optical properties of a novel organic-inorganic hybrid polymer (DDPSQ) based on a double-decker-shaped silsesquioxane (DDSQ). The DDSQ is a new family of silsesquioxanes consisting of a Si-O-Si case structure and functional organic side chain. The DDPSQ was synthesized by the hydrosilylation reaction between a hydrosilane-functionalized DDSQ and d vinyl-functionalized DDSQ with a Pt catalyst. The DDPSQ has a high transparency in the visible and UV regions and a high thermal stability up to 350oC owing to the inorganic Si-O-Si cage structure. The DDPSQ also has a high solubility in common organic solvent owing to the organic substituent. The refractive index dispersion and the thermo-optic coefficient (dn/dT) of the spin-coated DDPSQ films were observed by spectroscopic reflectometry. The values of the thermo-optic coefficient were compared among three kinds of silsesquioxanes. The first is the DDPSQ-1 consisting of DDSQ units. The second is the DDPSQ-2 consisting of DDSQ and linear siloxane chain. The third is the amorphous polysilsesquioxane (PSQ) synthesized by the hydrolysis of phenyltrichlorosilane. Although very high negative values of the thermo-optic coefficient around- 400 ppm/K were observed for both DDPSQ-1 and DDPSQ-2, the DDPSQ-2 with a flexible siloxane chain showed the higher thermo-optic coefficient. The refractive indexes of the DDPSQ-1 and DDPSQ-2 showed reversible change in the temperature region from 30 to 250o. On the other hand, the thermo-optic coefficient of the amorphous PSQ is around - 200 ppm/K and the temperature change of the refractive index was irreversible, which was caused by the thermal reaction of the reactive residue such as a silanol group. The high thermo-optic coefficient of the DDPSQ was explained considering the voids around the DDPSQ polymer chain consisting of a bulky Si-O-Si cage structure and the thermal expansion of the polymer chain around the voids. The thermally stable and transparent DDPSQ with the high thermo-optic coefficient can be applicable to a thermo-optic switch.
11:30 AM - HH6.6
Fabrication of SnO2:CuO Films by Pulsed Laser Deposition: Influence of CuO-loading and Surface Nanostructure on Sensitivity to H2S.
Craig Jeffrey 1 , Laurent Peigat 1 , James Tunney 1 , Xaiomei Du 1 , Pierre Dalmay 1 , Michael Post 1
1 Materials for Chemical Sensors and Devices, National Research Council of Canada - Institute for Chemical Processes and Environmental Technology, Ottawa, Ontario, Canada
Show AbstractWednesday, November 28New AbstractHH6.6 @ 10:30 AMFabrication of SnO2:CuO Films by Pulsed Laser Deposition: Influence of CuO-loading and Surface Nanostructure on Sensitivity to H2S. Craig JeffreyFabrication of SnO2:CuO Films by Pulsed Laser Deposition: Influence of CuO-loading and Surface Nanostructure on Sensitivity to H2S. Craig A. Jeffrey, Laurent Peigat, James J. Tunney, Xaiomei Du, Pierre Dalmay, Michael Post. Materials for Chemical Sensors and Devices, National Research Council of Canada - Institute for Chemical Processes and Environmental Technology, Ottawa, ON, Canada. Tin dioxide (SnO2) films loaded with copper oxide (CuO) have shown great promise as sensor materials for many molecules including hydrogen sulfide (H2S). Many deposition and fabrication methods have been employed to produce these materials yet there has been relatively little attention paid to Pulsed Laser Deposition (PLD) despite the advantages this approach provides; these include a range of variable deposition parameters and the ability to produce two-phase composite films from a single target of corresponding stoichiometry. This study examines the efficacy of varying levels of CuO loading in detecting H2S as well as representative alkene and alkane molecules. With the optimum CuO content determined, two series of films were deposited while varying the substrate deposition temperature and the deposition chamber oxygen pressure respectively. Characterization of these films by Scanning Electron Microscopy (SEM) reveals that a wide range of interfacial morphologies can be produced by altering these deposition conditions. Experiments to determine the sensitivity to H2S are presented and demonstrate remarkable response at relatively low temperature (~ 200°C). Initial results concerning the interfacial structure of these films on silicon-based prototype devices are also presented.
11:45 AM - HH6.7
Periodic Mesoporous Phosphorus Oxyimides.
Kai Landskron 1 , Paritosh Mohanty 1
1 Chemistry, Lehigh University, Bethlehem, Pennsylvania, United States
Show AbstractPeriodic mesoporous phosphorus oxyimides with P6mm hexagonal and body centered cubic structure (PON-1 and PON-2) were successfully synthesized by a solvent-free nanocasting route using periodic mesoporous silica as hard template. The synthesis succeded via a melt-infiltration/nitridation route using (PNCl2)3/NH3 and subsequent template removal. EDS and element analyis show that the siliceous template can be highly selectively removed. The materials exhibit excellent mesopore uniformity and periodicity with pore diameters of ca. 5 nm. The materials have high surface areas of 380 and 244 m2/g and excellent thermal stabilities (600 and 750°C) for PON-1 and PON-2 respectively.
12:00 PM - HH6.8
Periodic Mesoporous Benzene-silica Material with Uniform Phosphine Oxide Ligand Distribution: Synthesis, Characterization and Study of its Potential Application as Support for Optical Active Species.
Paula Ferreira 1 , Joao Alonso 1 , Tsvetelina Petkova 1
1 Ceramic and Glass Engineering, CICECO, University of Aveiro, 3810-193 Aveiro Portugal
Show AbstractThe ordered mesoporous organo-silica materials gained a large interest since 1992 because of the possibility of tailoring the pore structure, framework composition and morphologies over a broad range.[1] The potential applications, such as separation, catalysis, nanoelectronics, sensors, host-systems, arise from high specific surface area and large pore diameters (between 2 and 10 nm) of these materials. They can be prepared by three methodologies: a) by attachment of organic functionalities directly onto amorphous silica based mesoporous material; b) by co-condensation of silylated organic compounds with silica based precursors and c) by condensation of bissilylated organic precursors. The later method leads to the formation of periodic mesoporous organo-silicas (PMOs) materials, which started to be developed in 1999 [2] and have the great advantage of incorporate homogeneously the organic function inside of the wall of the mesoporous material with low reduction of the surface area. Inagaki and co-workers [3] reported that an hierarchically ordered structure with meso- and molecular-scale periodicity is obtained for phenylene-bridged mesoporous systems. PMO with crystal-like walls are of considerable interest because they may exhibit improved thermal stability, selectivity and activity in catalytic applications. Bion et al.[4] reported the synthesis of periodic mesoporous benzene-silica hybrid materials prepared with three surfactants and as a result they have different pores sizes, while maintaining the wall molecular-scale periodicity.In this work, we simultaneously co-condensate a silylated organophosphine (diphenyl-3-(triethoxysilyl)ethylphosphine) ligand with a bissilylated benzene (1,4-bis(triethoxysilyl)benzene) precursor using a non-ionic triblock copolymer P123 (EO20PO70EO20) surfactant under acidic conditions. After hydrothermal treatment the copolymer was extracted by ethanolic/acid solution. The extracted material was then fully oxidized by hydrogen peroxide treatment. The benzene-silica material containing uniform phosphine oxide ligand distribution was characterized by powder XRD, solid state NMR (13C, 29Si and 31P), low temperature N2 isotherms, elemental analysis and TEM.The insertion of the phosphine ligand and subsequent oxidation do not affect the meso-order or reduce significantly the surface area. Europium nitrate and yttrium nitrate were reacted with the material in order to study the reaction of complexation to the phosphine oxide ligand and the results will be presented.1 C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli, J. S. Beck, Nature 1992, 359, 710.2 T. Asefa, M. J. MacLachlan, N. Coombs, G. A. Ozin, Nature 1999, 402, 867; S. Inagaki, S. Guan, Y. Fukushima, T. Ohsuna, O. Terasaki, J. Am. Chem. Soc. 1999, 121, 9611. 3 S. Inagaki, S. Guan, T. Ohsuna, O. Terasaki, Nature 2002, 416, 304.N. Bion, P. Ferreira, A. Valente, I. S. Gonçalves, J. Rocha, J. Mater. Chem. 2003, 13, 1910.
12:15 PM - HH6.9
Highly Crystalline, Thermal Stable Mesoporous Metal Oxides and Their Catalytic Applications.
Donghai Wang 1 , Jun Liu 1 , Sheng Dai 2 , Zhen Ma 2 , Zimin Nie 1 , Qisheng Huo 1 , Chongmin Wang 1
1 Chemical & Materials Science Division and Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, Richland, Washington, United States, 2 Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractHigh surface area nanocrystalline metal oxides including TiO2, CeO2, and SnO2 have wide applications. For catalysis, retaining its nanostructure and activities at high temperatures is a great challenge. Here we report synthesis of a new class of highly crystalline, thermally stable mesoporous metal oxides by using a surfactant matrix to simultaneously control the pore dimension and the crystallization process. In particular in TiO2, a surfactant matrix to simultaneously control crystallization process, orientation and spatial arrangement, producing novel highly crystalline mesoporous TiO2 from aligned nanorod-like building blocks, a drastic departure from traditional mesoporous TiO2 containing randomly oriented anatase. X-ray diffraction patterns and N2 sorption isotherms reveal their high-surface-area mesoporous structure with tunable mesopore diameter. TEM and SEM measurements show that framework of the mesoporous TiO2 is composed of aligned rutile rod-like nanocrystals grown along [001] direction. Such stable, highly crystalline mesoporous materials are expected as a good candidate of stable catalyst support. The new mesoporous crystalline TiO2 supported Au nanoparticles showed high reactivity and on-stream stability towards low-temperature CO oxidation even after heat treatment at 400°C to 500°C. Similar synthesis strategy is extended to highly crystalline mesoporous CeO2 and SnO2. The high temperature activity, the thermal stability and sintering resistance of mesoporous CeO2 supported Au nanoparticles have been also demonstrated in water gas shift reaction. In summary, we have developed a new approach to produce highly crystalline mesoporous metal oxide. These materials have potential as robust high-surface-area catalyst supports and other applications such as electrodes in high capacity batteries.
12:30 PM - HH6.10
In-situ X-ray Diffraction Experiments During the Synthesis of Nanoporous Gold.
Steven Van Petegem 1 , Stefan Brandstetter 1 , Andrea Hodge 2 , Helena Van Swygenhoven 1
1 , Paul Scherrer Institute, Villigen Switzerland, 2 , Lawrence Livermore National Laboratory, Livermore, California, United States
Show Abstract12:45 PM - HH6.11
Lightweight Aerogel Structural and Insulation Materials.
Decio Coutinho 1 , Wendell Rhine 1 , Kiranmayi Deshpande 1
1 , Aspen Aerogels, Northborough, Massachusetts, United States
Show AbstractNASA’s exploration systems architecture presents some propulsion challenges that require new technologies to be developed. To solve these challenges, NASA needs new technologies for long term cryogenic propellant storage, management and acquisition applications in-space as well as on the lunar surface. These technologies will impact cryogenic systems for space transportation orbit transfer vehicles, space power systems, spaceports, spacesuits, lunar habitation systems, robotics, and in situ propellant systems. The sizes of these systems range from the small (< 20 m3 for supercritical air and payload cooling) to very large (> 3400 m3 for LOX and LH2 propellant storage). Advanced materials are needed to help solve the unique requirements of these small to very large storage systems. Aerogels could be used as advanced insulation materials capable of retaining structural integrity over a large range of operating temperatures with improvements in strength over current state of the art aerogel formulations. We have developed high strength hybrid inorganic/organic aerogels by modifying the aerogel framework with cross-linking agents. The reinforced aerogels were prepared by cogelling the appropriate bridged trialkoxysilane with a hydrolyzed silica sol. The aerogels prepared showed a remarkable increase in the compression modulus, while maintaining excellent thermal insulating capability compared to native silica aerogel.
HH7: Processing and Properties of Nanomaterials
Session Chairs
Wednesday PM, November 28, 2007
Room 302 (Hynes)
2:30 PM - **HH7.1
Chemically Designed Nanoparticles and Nanowires: Controlled Growth, Applications and Devices.
Sanjay Mathur 1 2
1 Leibniz Institute of New Materials, Saarland University, Saarbruecken Germany, 2 Department of Chemistry, Wuerzburg University, Wuerzburg Germany
Show AbstractAvailability of high-purity nanophase materials exhibiting specific properties, tailored shape and microstructure is essential for transforming the developments of nanoscience into nanotechnology. Despite extensive research in the synthesis and processing of inorganic materials, producing nanoscaled matter with precise control over chemical composition, morphology and microstructure remains an overarching task. The conventional synthesis of inorganic compositions, controlled by diffusion of ionic and atomic species through both reactants and products, is rather crude for the unit-by-unit assembly of nanostructures. Given the inherent limitations of traditional material processing routes, we are developing chemical concepts for a designed materials synthesis and evaluating their applications in chemical nanotechnologies. Since molecular level synthesis of inorganic materials is not a predictive science, it is difficult to anticipate the phase structure and properties of the resulting solid from the knowledge of the chemical design. This talk will present how chemically processed nanoparticles and nanowires of different metal oxides open up new vistas of material properties, which can be transformed into advanced material technologies. The examples will include application of superparamagnetic iron oxide nanoparticles for drug delivery applications and development of single-nanowire based devices.
3:00 PM - HH7.2
Quantum Confined Inorganic Nanowires with Polymer-Like Properties.
Ludovico Cademartiri 1 , Reihaneh Malakooti 1 , Gerald Guerin 1 , Paul O'Brien 2 , Andrea Migliori 3 , Nazir Kherani 2 , Mitchell Winnik 1 , Geoffrey Ozin 1
1 Department of Chemistry, University of Toronto, Toronto, Ontario, Canada, 2 Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, Canada, 3 , CNR-IMM, Bologna Italy
Show AbstractBi2S3 is among the best thermoelectric materials known. Shrinking its feature size below two nanometers would allow for greatly improved thermoelectric performance as the thermal conductivity should be drastically reduced by boundary scattering.We hereby present the synthesis and characterization of Bi2S3 nanowires with unprecedented narrowness (<2 nm), flexibility and polymer-like properties, obtainable in gram-scale quantities with no need of catalysts. In the time available we will present data regarding their microstructure, the electrical conductivity, photoconductivity, persistence length and conformation in solution.
3:15 PM - HH7.3
Effect of Ligand Exchange on the Stability and Optical Properties of CdSe Quantum Dots.
Jacqueline Siy 1 , Lindsay Leone 1 , Michael Bartl 1
1 Chemistry, University of Utah, Salt Lake City, Utah, United States
Show AbstractRecent advances have shown that II-IV semiconductors, in particular CdSe, have a wide range of potential applications. Extensive studies have been done mainly to develop methods to prepare various kinds of nanomaterials, as well as the ability to manipulate their size-dependent unique properties. Here we present a new post-synthesis heat-treatment/ligand-exchange procedure that allows tailoring the size of CdSe quantum dots, while still retaining their excellent luminescent efficiency. We will show that careful heat-treatment of before-made quantum dots in the presence of alkyl-amine surfactants results in the tunable reduction of the nanoparticle size over a large range accompanied by a change in the optical properties. We will discuss in detail the influence of crucial reaction parameters such as the temperature, amount of surfactant and solvent, nanocrystal initial size and the length of time of treatment on the observed size evolution. The mechanism of this heat/ligand-exchange-dependent size reduction is investigated by a number of characterization techniques including optical microscopy, electron microscopy and NMR. This study provide us with valuable insights into the growth evolution, surface phenomena and stability of nanocrystals which can serve as a framework for designing, controlling and processing nanomaterials and devices.
3:30 PM - HH7.4
The Role of Synthesis Conditions in the Formation and Curvature of Vanadium Oxide Nanotubes, Nano-urchins and (enH2)V7O16.
Megan Roppolo 1 , Natasha Chernova 1 , Shailesh Upreti 1 , M. Whittingham 1
1 , State University of New York at Binghamton, Binghamton, New York, United States
Show AbstractIn order to fully understand the formation mechanism, structure and role of structural curvature of vanadium oxide nanotubes (VONTs), two isostructural vanadium oxides of different morphologies, vanadium oxide nano-urchins [1] and the ethylene diamine-intercalated compound (enH
2)V
7O
16 [2], were synthesized. X-ray diffraction, electron microscopy, Fourier transform infrared spectroscopy, electron paramagnetic resonance (EPR), thermal gravimetric analysis, and magnetic measurements were used to characterize these compounds. Vanadium oxide nano-urchins with composition VO
2.3(C
12H
25NH
3)
0.4 . 0.3H
2O were synthesized for the first time using n-dodecylamine as an intercalating amine template. The resulting nano-urchins were 8-10 μm in size and were composed of radial arrays of high-quality VONTs. Ethylene diamine-intercalated vanadium oxides were synthesized using V
2O
5 and ethylene diamine at several pH values, with (enH
2)V
7O
16 obtained for the first time as pure phase at pH 3. These plate-like crystals have allowed us to study structure, magnetic properties, and EPR spectra without the complications brought on by tubular curvature. The effect of synthesis conditions on the formation of nano-urchins and (enH
2)V
7O
16 is discussed. We have shown that in nano-urchins and (enH
2)V
7O
16 vanadium is more reduced than in regular VONTs. The V
4+ fraction attains 0.8 in these compounds as compared to only 0.5 in the VONTs. The role of vanadium reduction in the formation of VONTs and nano-urchins is discussed. This work is supported by the National Science Foundation through grant DMR-0705657.
1. C. O’Dwyer et al., Chem. Mtls. 2006, 18, 3016.
2. M. Wörle, et al. Z. Anorg. Allg. Chem. 2002, 628, 2778.
4:15 PM - HH7.5
Metal Oxide Nanoparticles for Improved Lithium Ion Battery Technologies.
Anne Dillon 1 , Se-Hee Lee 1 , Yong-Hyun Kim 1 , Rohit Deshpande 1 , Philip Parilla 1 , Kim Jones 1 , Erin Whitney 1 , Shengbai Zhang 1 , Archie Mahan 1
1 Energy Sciences, National Renewable Energy Lab, Golden, Colorado, United States
Show AbstractLithium-ion batteries are the current power sources of choice for portable electronics. Although such batteries are commercially successful, they are not keeping pace with the rapid advances in computing technologies. Also, further improvement of performance and simultaneous reduction in cost as well as material toxicity could allow for the deployment of lithium-ion batteries in hybrid electric vehicles. Hot-wire chemical vapor deposition has been employed as an economically scalable method for the deposition of crystalline metal oxide nanoparticles at high density. Under optimal synthesis conditions, only crystalline nanostructures with a smallest dimension of ~ 10 - 50 nm are observed with extensive transmission electron microscopy analyses. The crystalline phases of the nanoparticles have been probed with Raman spectroscopy, as well as, electron and x-ray diffraction. Recently the incorporation of crystalline molybdenum oxide nanoparticles into porous films has led to profound advancements in state-of-the–art negative electrodes (anodes) in lithium-ion batteries. An unprecedented high and reversible capacity of ~ 630 mAh/g has been observed. Furthermore, the nanoparticle materials exhibit a high rate capability due to the reduced solid state Li-ion diffusion length. Theoretical calculations have been employed to elucidate the Li-ion intercalation mechanism and explain the reversible capacity. Investigations to employ alternate metal oxides to improve the positive electrode (cathode) materials are underway. The synthesis of these novel nanostructured materials and the mechanism for improving lithium-ion battery technologies will be discussed in detail.
4:30 PM - HH7.6
Structure and Luminescence of Ce-doped Lu2SiO5 Nanophosphor.
Ross Muenchausen 1 , Bryan Bennett 1 , Luiz Jacobsohn 1 , Stephanie Sitarz 1 , James Smith 1 , Ruigang Wang 2 , Peter Crozier 2 , D. Cooke 1
1 Materials Science & Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Center for Solid State Science and School of Materials, Arizona State University, Tempe, Arizona, United States
Show AbstractNanophosphors correspond to nanostructured inorganic insulator materials that emit light under particle or electromagnetic radiation excitation. While an intense investigative effort on the optical properties of nanostructured semiconductors has been carried out for more than a decade, nanophosphors have remained largely unexplored until recently. Of particular interest is the synthesis and characterization of rare-earth (RE) doped nanophosphors with emphasis on optical properties and how these change with reduced dimensionality. RE ions are particularly effective as luminescent centers in host lattices and are commonly utilized to produce high quantum efficiency bulk phosphors; accordingly, these are the nanophosphors of choice for our current research. In this work we investigate the structure and luminescent properties of Ce-doped Lu2SiO5 (LSO) nanophosphors prepared by solution combustion synthesis with the Ce content 0.1 to 12 at.%. Samples were characterized by transmission electron microscopy (TEM), line scan electron energy-loss spectroscopy (EELS) and x-ray diffraction (XRD). Contrary to bulk phosphors that possess C2/c space group, LSO nanophosphors crystallize in the P21/c arrangement with nanocrystal dimensions typically tens of nanometers. Photoluminescence excitation and emission spectra are composed of two major bands centered at 360 and 430 nm, respectively. These results reveal a red-shift and enhanced Stokes shift for the nanophosphors when compared to bulk. Ce content was also found to affect photoluminescence emission intensity and fluorescent lifetime. The nanophosphor concentration quenching curve presents a broad maximum centered at 1 at.%. Lifetime measurements show a continuous decrease from 34 to 21 ns as Ce content is increased. These results reveal unique properties of reduced dimensional phosphors and show that nanophosphors are promising materials for fundamental science investigation as well as technological applications.
5:00 PM - HH7.8
Selforganization of Nanodots and Nanogaps by Anodization and Room-temperature Observation of a Giant Coulomb Blockade Voltage.
Yasuo Kimura 1 2 , Takami Muto 1 , Ryo-taro Yamaguchi 1 , Ken-ichi Ishibashi 1 , Kingo Itaya 2 3 , Michio Niwano 1 2
1 Laboratory for Nanoelectronics and Spintronics, RIEC, Tohoku Univ., Sanda, Hyogo, Japan, 2 CREST, Japan Science and Technology Corporation, Sendai Japan, 3 Department of Applied Chemistry, Faculty of Engineering, Tohoku University, Sendai Japan
Show AbstractA technology for fabricating nanostructures has been extensively studied in order to develop electronic or photonic devices based on new types of mechanisms such as quantum effects. There are generally two complementary approaches to fabrication of nanostructures. One is a top-down process as typified by a lithography technique widely used in LSI technology and the other is a bottom-up process such as a selforganization process. In the case of the conventional lithography technique, it is not easy to fabricate nanostructures although it is suitable for controlling their positions. In contrast, a selforganization process does not control positions of nanostructures though it can easily produce nanostructures. Therefore, it is important to develop a hybrid technique of these complementary techniques. It is well-known that an anodization process of aluminum easily forms porous anodic alumina with self-ordered nanohole arrays. Here, we fabricated nanodots controlled their positions using both the anodic porous alumina formation process and a photolithography technique. As a result, we observed a clear Coulomb staircase with a very large Coulomb energy of about 2 to 3 eV at room temperature. This very large Coulomb energy is attributed to the device structure depending strongly on the anodization mechanism. Our results indicate that a single electron transistor (SET) operating at room temperature can be fabricated at an appropriate position using both bottom-up and top-down processes. Our technique can be applied to another valve metal such as titanium and gives new selections of materials and methods of nanodevices leading to producing nanodevices with new functions.
5:15 PM - HH7.9
SnO2/Pt Nanocrystals Coated ZnO Nanowires for Highly Sensitive Gas Sensors.
Jiajun Chen 1 , Kai Wang 1 , Weilie Zhou 1
1 , Advanced Materials Research Institute, New Orleans, Louisiana, United States
Show AbstractSnO2 and ZnO nanostructures (nanoparticles and nanowires) are promising materials for fabricating highly sensitive sensors due to their high aspect ratio. One strategy to increase the sensitivity of nanowire based gas sensors is to introduce noble metal nanoparticles on the surface of nanowires. In this presentation, we used vapor-liquid-solid (VLS) grown ZnO nanowire arrays as templates and grew SnO2 nanocrystals on the surface of ZnO nanowires by pulsed laser deposition (PLD), followed with Pt sputtering as catalysts to further enhance the sensitivity of the gas sensors. The synthesized nanostructures are characterized by field-emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) equipped with electron energy dispersive x-ray analysis (EDS). SnO2 nanocrystals were grown on ZnO nanowires with Volmer-Weber (island) growth mode due to the large lattice mismatch between the SnO2 and ZnO. Pt nanoparticles were also deposited on these nanostructures by DC sputtering. These nanostructures can be used for highly sensitive gas sensor fabrication. Back-gated field effect transistors (FET) based on SnO2/Pt nanocrystals coated ZnO Nanowires have been prepared by nanolithography. The I-V properties of these devices show that the nanowires worked as n-type channel. The gas sensing properties of this nanosensor will also be discussed.
5:30 PM - HH7.10
A Self-Templated Approach to TiO2 Microcapsules.
Yongxing Hu 1 , Jianping Ge 1 , Tierui Zhang 1 , Yadong Yin 1
1 Department of Chemistry, University of California, Riverside, Riverside, California, United States
Show AbstractWe report a self-templated approach for the direct preparation of hollow TiO2 microcapsules from their solid counterparts without the involvement of additional sacrificial templates. TiO2 microcapsules with tunable size and wall thickness have been synthesized by heating sol-gel derived TiO2 microspheres with polyacrylic acid (PAA) in a diethylene glycol (DEG) solution. PAA plays a crucial role in the formation of microcapsules by crosslinking the surface TiO2 nanoparticles and preventing them from dissolution by DEG. Hollow microcapsules form when DEG molecules penetrate the outer layer and remove the core materials by forming soluble titanium glycolate. Comparing to the conventional templating methods, the direct synthesis approach has advantages in practical applications due to significantly reduced production cost and the ease of scaling up. Here we will also discuss the extension of the syntheses to composite microcapsules containing TiO2 and various other nanostructured materials.
5:45 PM - HH7.11
Doped Zirconia Luminescent Nanoparticles.
Dajie Zhang 2 , Jennifer Sample 1
2 , Johns Hopkins University Advanced Technology Laboratory, Baltimore, Maryland, United States, 1 , Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, United States
Show AbstractNanoparticles that fluoresce or absorb light in the visible and near-IR wavelengths are desirable for a variety of applications including biological tagging for medical imaging purposes and for solar control glazing in the automobile industry. Semiconductor quantum dots are commercially available and dyed polymer nanoparticles as well as organic dye/silica core shell nanoparticles have also been demonstrated. We report the synthesis, characterization, and optical properties of another luminescent nanoparticle: doped zirconia. The zirconia nanoparticles reported in this study are doped with up to 10% of the lanthanide dopants Er, Gd, Nd and Eu. These materials emit in the visible and near-IR wavelengths depending on the dopant and are refractory, making them useful for high temperature applications. These cations were found to stabilize the cubic phase over the monoclinic phase of zirconia, at approximately 10% dopant, as characterized by X-ray diffraction. We report the luminescence spectra of these nanoparticles at various wavelengths which reveal emissions from the matrix as well as from the dopants.
HH8: Poster Session: Nanophase, Nanocomposite and Nanostructured Materials I
Session Chairs
Katsumi Kaneko
Sridhar Komarneni
Paul O'Brien
John Parker
Thursday AM, November 29, 2007
Exhibition Hall D (Hynes)
9:00 PM - HH8.10
Microwave-assisted Synthesis of Nanomagnetic Materials, Sintering and Properties.
Sridhar Komarneni 1 , Sarabu Murthy 2
1 , The Pennsylvania State University, University Park, Pennsylvania, United States, 2 , Osmania University, Hyderabad India
Show AbstractLead oxide and tantalum oxide added Mg-Cu-Zn ferrite and Ni0.5-xCuxZn0.5Fe2O4 (x=0, 4, 6, 8 or 12mol%) ferrite powders were prepared by using a microwave-hydrothermal (M-H) process. The synthesized ferrite samples were characterized by powder X-ray diffraction (XRD), infrared spectroscopy and transmission electron microscopy (TEM). Nanophase ferrites (~10-60 nm) with high surface area were synthesized at a temperature of 160oC in 1 hour. The nanopowders were sintered at 900oC / 4h in air atmosphere. The variations of the sintered density, saturation magnetization and other properties with dopant concentration have been investigated. The doped and sintered magnetic materials are expected to be useful for high frequency applications.
9:00 PM - HH8.11
Crystal Size Effects on Breakdown of Dislocation-mediated Plasticity at the Nanoscale.
Dipanjan Sen 1 2 , Markus Buehler 1
1 Laboratory for Atomistic and Molecular Mechanics, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractConfinement effects in nanomaterials have often been suggested as the explanation for the high strength of nanostructured materials. Here we provide a systematic theoretical and molecular dynamics study of size effects that control dislocation-mediated plasticity in crystals. For the molecular dynamics study, we utilize a model coupled harmonic and Morse two-body atomic potential with finite stacking fault and unstable stacking fault energies that allows us to tweak elastic and dislocation-controlling parameters of the atomic system independently. Through the analysis of a confined crack in a nanocrystal under mode II loading, we prove the existence of two universal length scales that control the mechanism of plastic deformation. The two length scales separate characteristic material dimensions that distinguish complete dislocation nucleation, partial dislocation and no dislocation nucleation from the crack tip. We establish the importance of these length scales on the changes in plastic deformation modes in nanocrystalline bulk materials and thin films.
9:00 PM - HH8.12
Morphology Control of Core-Shell Nanoparticles in a Matrix with Electric Field.
Jonghyun Park 1 , Wei Lu 1
1 Mechanical Engineering, University of Michigan, Ann Arbor, Ann Arbor, Michigan, United States
Show Abstract9:00 PM - HH8.13
Oxygen Vacancy Ordering in Transition Metal Oxide Nanowires.
Zhiqiang Chen 1 , Uros Cvelbar 2 , Miran Mozetic 2 , Mahendra Sunkara 1
1 Institute for Advanced Materials & Renewable Energy, University of Louisville, Louisville, Kentucky, United States, 2 Plasma Laboratory , Jozef Stefan Institute, Ljubljana Slovenia
Show Abstract9:00 PM - HH8.14
Dispersion and Assembly of Submicron- and Nanoparticles into New Materials.
Andre Studart 1 2 , Urs Gonzenbach 1 , Lorenz Bonderer 1 , Ilke Akartuna 1 , Franziska Krauss 1 , Elena Tervoort 1 , Ludwig Gauckler 1
1 Department of Materials, ETH Zurich, Zurich Switzerland, 2 School of Engineering & Applied Sciences / Department of Physics, Harvard University, Boston, Massachusetts, United States
Show AbstractSubmicron- and nanoparticles are widely used for the manufacture of advanced materials and are also likely involved in the biomineralization processes leading to exquisite structures in nature. The surface chemistry of these colloidal building blocks is of major importance to control the interactions between particles and interfaces during the assembly process of such structures. Inspired by the unique microstructures built by living organisms, we deliberately tailor the surface chemistry of colloidal particles in order to fabricate new structural and functional materials. Here, we illustrate how the surface chemistry of colloidal particles can be tailored (i) to disperse nanoparticles in concentrated aqueous and non-aqueous suspensions and (ii, iii) to direct the assembly of submicron- and nanoparticles at interfaces to create novel 2D and 3D materials. The surface chemistry of colloidal particles can be tailored through the adsorption of specific molecules on the particle surface. To deliberately control the surface chemistry, we used short molecules with a head-tail architecture. The head group is chosen to strongly adsorb on the particle surface, while the tail segment is selected according to the functionalization desired. In the first example (i), the architecture and length of the organic molecules were designed in order to provide a steric layer around the nanoparticles that prevents their strong agglomeration due to attractive van der Waals forces. In the second example (ii), platelets with tailored surface chemistry are assembled at an air-water interface and later spin-coated with an organic layer to produce artificial hybrid films with mechanical behavior similar or superior than that of bone, dentin and nacre. In the final example (iii), short molecules are used to control the wettability of particles in the liquid phase, so as to promote their adsorption at fluid interfaces and thus the stabilization of wet foams and emulsions. By controlling the surface chemistry of particles in such a manner one is able to produce nanostructured ceramic films, particle-coated capsules, macroporous materials, as well as strong hybrid films for a variety of applications.
9:00 PM - HH8.15
Enzymatic Synthesis and Incorporation of Polyaniline into MCM-41 Zeolite Channels.
Erika Flores-Loyola 1 , Jorge Romero-Garcia 2 , Rodolfo Cruz-Silva 3 , F. Castillon 4 , M. Farias 4 , A. Cabral-Prieto 5
1 Escuela de Ciencias Biológicas, Universidad Autónoma de Coahuila, Torreón, Coahuila, Mexico, 2 , Centro de Investigación en Química Aplicada, Saltillo, Coahuila, Mexico, 3 Centro de Investigación en Ingeniería y Ciencias Aplicadas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, Mexico, 4 Centro de Ciencias de la Materia Condensada, Universidad Nacional Autónoma de México, Mexico, D.F., Mexico, 5 , Instituto Nacional de Investigaciones Nucleares, Ocoyoacac, Mexico, Mexico
Show AbstractPolyaniline (PANI) is a conductive polymer which has attracted considerable attention due to its interesting electrochemical behavior, the reversible nature of its electrical conductivity as well as its environmental stability. This polymer is usually synthesized by chemical and electrochemical methods. However, during the last years great attention has been paid to the enzymatic polymerization of aniline due to its efficiency and environment alliance. Nevertheless, the aniline enzymatic polymerization in template free environments proceeds preferentially by 1,2 and multisubstitutions yielding branched polymer chains. To avoid branching or crosslinking during synthesis, a mesoporous inorganic material can be used as template to promote the polymerization in a more ordered and efficient form. For that reasons, in this work, the structure of PANI synthesized by enzymatic oxidation in the pores of MCM-41 mesoporous inorganic substrates was studied. This material was prepared by polymerizing aniline, absorbed in the pores of MCM-41, in acidic medium by enzymatic synthesis using Soybean Peroxidase (SBP) and Horseradish Peroxidase (HRP) as catalysts, and hydrogen peroxide as oxidizer. The characterization of the chemical structure of the enzymatically synthesized PANI was carried out by electronic absorption and X-ray photoelectron spectroscopy. The results indicated that the polymeric material extracted with N-methyl-2-pyrrolidinone from MCM-41 hosts corresponds to emeraldine, the conductive form of PANI. The intrachannel polymerization was probed by the change in the pore volume from the empty host to the hosted MCM-41. This evaluation was done by nitrogen sorption and through the free volume determination by positron annihilation life time spectroscopy (PALS). The results showed a change in porosity of about 85%, which confirmed that aniline polymerization take place mainly intrachannels. Thermal stability was analyzed by thermo gravimetric analysis, which indicated that the encapsulated PANI in the pores of MCM-41 is thermally more stable than bulk PANI. Apparently the use of enzymes with different stability do not affect significantly the chemical structure of PANI, but the reaction yields are considerably influenced, achieving higher yields (77%) with SBP than with HRP (35%).In conclusion, polyaniline can be enzymatically synthesized in the presence of MCM-41 inorganic substrates under acidic conditions obtaining the chemical structure of emeraldine. The polymerization have place mainly intrachannels, and the different enzyme types do not have significant influence on the PANI chemical structure.
9:00 PM - HH8.16
Nanowires, Nanoplatelets and Nanocubes of Hexagonal WO3.
Krithika Kalyanasundaram 1 , P. Gouma 1 , Hajime Haneda 2 , Naoki Ohashi 2
1 Materials Science and Engg, SUNY, Stony Brook, Stony Brook, New York, United States, 2 Sensor Materials Center, National Institute of Materials Science, Tsukuba Japan
Show Abstract9:00 PM - HH8.18
Solvothermal Synthesis of BaTiO3 Nanocrystals, Thin Films and Applications.
Limin Huang 1 2 3 , Zhuoying Chen 1 2 , Stephen O'Brien 1 2 3
1 Applied Physics and Applied Mathematics, Columbia University, New York, New York, United States, 2 the Columbia Materials Research Science and Engineering Center, Columbia University, New York, New York, United States, 3 the Columbia Nanocenter , Columbia University, New York, New York, United States
Show Abstract9:00 PM - HH8.19
Effect of Pore Morphology on the Electrochemical Properties of EDL Carbon Cryogel Supercapacitors.
Betzaida Garcia 1 , Aaron Feaver 2 , Guozhong Cao 1
1 Materials Science & Engineering, University of Washington, Seattle, Washington, United States, 2 , Energ2, Seattle, Washington, United States
Show AbstractIn this study a group of resorcinol-formaldehyde carbon cryogels (CC) have been processed chemically, via catalyst and activation, to obtain various nanostructures and pore size distributions. To understand the relation between structure and electrochemical properties an alternate approach to the transmission line’s cylindrical pore method is used. Using electrochemical impedance spectroscopy (EIS), the capacitor can be studied as a dielectric system composed of the porous electrode and the electrolyte (PC/ TEATFB). The complex capacitance and power are used to study the behavior of the system below the relaxation frequency fo (φ = -45o). Therefore, the relaxation of the capacitor system at the low frequency range, f < fo, can be used as a measure of pore/ electrolyte interaction. The approach here proposed also allows for a direct experimental characterization of the capacitance and power at low frequencies where small pores are likely to affect the diffusion dynamics of the electrolyte molecules. The results suggest a correlation between the occurrence of small micropores and that of high power losses that are related to the resistive element produced at the low frequency range. The measurements show that the dissipative power of the samples increased steadily with decreasing micropore diameter (2 – 1.6nm), from 3% to 36% when measured at a frequency of 0.004Hz (below f0). But this was not the case in all samples, the sample with smallest micropore diameter (d = 1nm) the power loss decreased to 20%. The former behavior can be explained by a shift of the micropores’ capacitive peak (or low frequency peak) to lower frequencies. Moreover, the impact that the micropore structure has in the supercapacitor’s performance can be seen in its capacitance and energy as well. In addition to the complex power and capacitance; other measurements like BET Nitrogen sorption, cyclic voltammetry, galvanic cycling and X-Ray Raman Scattering were used to characterize the samples and support these results. Ultimately this method of evaluating the electrochemical behavior can be related to tuning parameters of CC like the catalyst and activation, which are responsible for the structural differences.
9:00 PM - HH8.20
Triple-crystal Zinc Selenide Nanobelts.
S. Liu 1 2 , Wallace Choy 1 , Y. Leung 1 , G. Zheng 2 , A. Soh 2
1 Department of Electrical & Electronic Engineering, the University of Hong Kong, Hong Kong China, 2 Department of Mechanical Engineering, University of Hong Kong, Hong Kong China
Show AbstractRecently, many papers have reported on II-VI compound semiconductor nanomaterials with wurtzite structure, particularly in ZnO and ZnS because of their interesting properties such as piezoelectricity and pyroelectricity resulting from the noncentro-symmetric wurtzite structure. These low-dimensional II-VI compounds show tremendous potential in engineering applications. It has been demonstrated that the shape, morphology and structural parameters have significant influence on the properties of nanostructures. For some sophisticated nanocrystals such as three-terminal ballistic junctions or Y-branch junctions, novel properties or applications might emerge. Up to date, the control of shape and morphology of these nanostructures mainly rely on the anisotropic nucleation and growth of nanocrystal from the liquid phase. There are other typical methods to control the shape and morphology of the nanostructures such as the regulation of the growth rates of different crystal facets and growth on templates. In the synthesis of 1D nanocrystals, observation of the growth of three-dimensional (3D) architecture is very rare.In this paper, one-dimensional ZnSe nanobelts with three-dimensional triple-crystal architecture have been fabricated on Au coated Si substrates by thermal evaporation of ZnSe powders. The as-synthesized triple-crystal ZnSe nanobelts are metastable 2H-wurtzite structure while the typical structure of ZnSe nanocrystal is stable zinc-blende. The triple-crystal nanobelts have a typical length of tens of micrometers and a thickness of 30-80 nm. The morphology and growth mechanisms of the triple-crystal nanobelts which cannot be described by the commonly used Octahedral Multiple-Twin growth model for similar nanostructures are investigated and explained based on the {10-13} twins and two fastest growing directions of [0001] and [1-100] of the belt. The thermodynamics of the formation of metastable wurtzite ZnSe nanostructures are also discussed in terms of the temperature and surface energy. The photoluminescence spectra show that the triple-crystal nanobelts possess high quality crystalline structure.
9:00 PM - HH8.21
Synthesis of Pure and Loaded WO3 Nanoparticles Using Flame Spray Pyrolysis Method.
Lisheng Wang 1 , Perena Gouma 1 , Alexandra Teleki 2 , Sotiris Pratsinis 2
1 Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 2 Particle Technology Laboratory, ETH Zürich, Zürich Switzerland
Show AbstractAs an important kind of semiconducting metal oxides, WO3 is a promising functional material used for electrochromic devices such as smart windows and resistive gas sensors, esp. for NOx gas detection. In this report, a new method called flame spray pyrolysis was applied to synthesize ultrafine WO3 nanoparticles. The sizes of as-synthesized particles, varying from 15 nm to 50 nm, can be controlled by modifying setup. Most of the products can be indexed as monoclinic phase while a small portion belong to a new tungsten oxide hydrate. Heat treatment enables the particles to grow up and removes the byproduct. In addition, two elements, Mn and Cr, were doped into the system. Among them, a second monoclinic MnWO4 phase is formed if manganese is doped. In contrast, chromium atoms take place of tungsten sites, forming a solid solution W1-x CrxO3 and resulting in a structure distortion.
9:00 PM - HH8.22
Shape Selective Gold Nanoparticle Synthesis Using Different Liquid Crystalline Phases.
George John 1 , Ajay Mallia 1 , Praveen Kumar Vemula 1 , Ashavani Kumar 2 , Pulickel Ajayan 2
1 Department of Chemistry, City College of the City University of New York, New York, New York, United States, 2 Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
Show Abstract9:00 PM - HH8.23
Calcium Phosphate Nanopowders Contaning Tailoring Product.
Tatiana Safronova 1 , V. Putlayev 1 , M. Shekhirev 1 , A. Kuznetsov 1 , M. Steklov 1 , S. Korneychuk 1 , A. Sergeeva 1
1 , Moscow State University, Moscow Russian Federation
Show Abstract9:00 PM - HH8.24
Low-temperature Asymmetric Growth of CdSe Quantum Dots to Quantum Rods.
Jonathan Doll 1 2 , Rongfu Li 1 2 , Fotios Papadimitrakopoulos 1 2 3
1 Institute of Materials Science, University of Connecticut, Storrs, Connecticut, United States, 2 Nanomaterials Optoelectronics Laboratory, University of Connecticut, Storrs, Connecticut, United States, 3 Department of Chemistry, University of Connecticut, Storrs, Connecticut, United States
Show Abstract9:00 PM - HH8.25
Processing of Electro-active β-PVDF Micro- and Nano-composites Based on PVDF.
Joao Gomes 1 2 , Daniel Miranda 1 , Jivago Nunes 1 , Carlos Costa 1 2 , Sérgio Mendes 1 , Vitor Sencadas 1 , Senentxu Lanceros-Mendez 1
1 Smart Materials, CeNTI, Famalicão, Minho, Portugal, 2 Physics, Universidade do Minho, Braga, Minho, Portugal
Show Abstract9:00 PM - HH8.26
Flow Mechanics of Polymer Nanocomposites.
Benjamin Anderson 1 , Charles Zukoski 1
1 Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractIn this paper we explore the rheological behavior of polymer nanocomposite of increasing MW and relate the flow mechanics to the particle microstructure probed with ultra small angle x-ray scattering. These studies were conducted to understand polymer mediated particle-particle interactions, filler effects on polymer chain dynamics, and potential particle-polymer phase separation. The phase behavior of polymer nanocomposites will be governed by enthalpic and entropic contributions. A variety of phases are expected as particle volume fraction, polymer molecular weight, and segment-surface interactions are varied: homogeneous fluid, phase separation, or nonequilibrium gel. The development of systematic studies aimed at understanding filler effects on melt mechanics is difficult. Relaxation times are long for high molecular weight polymers. This makes attaining equilibrium questionable. To circumvent this issue, we have investigated nanosilica dispersions in low molecular weight polyethylene glycol (PEG) and PEG derivatives of increasing molecular weight. In previous work, nanosilica was shown to be stable in PEG melts witnessed by the particle second virial coefficient being slightly greater than unity and to interact as hard spheres of slightly larger excluded volume through measurement of the particle structure factor. These results imply immobilized polymer on the particle surface which provides steric stabilization due to a favorable attraction between the particle surface and polymer segments. In recent studies, we find the relative viscosity to increase upon addition of filler particles as Einstein predicts but the slope of the increase is greater for higher MW polymers. As we raise the filler volume fraction, we see an arresting of chain dynamics witnessed by a plateau in the elastic modulus that depends on filler volume fraction and polymer molecular weight suggesting a phase transition. At the same time, multiple relaxation behavior is seen in the viscous modulus when approaching the transition volume fraction. We relate the results to polymer confinement between two plates and find remarkable similarities to previous work.
9:00 PM - HH8.27
Interfacial Elastic Constants For Polymer-Nanotube Composites From Molecular Dynamics Simulation.
Sarah-Jane Frankland 1 , Thomas Gates 2
1 , National Institute of Aerospace, Hampton, Virginia, United States, 2 Durability, Damage Tolerance and Reliability Branch, NASA Langley Research Center, Hampton, Virginia, United States
Show AbstractThe inclusion of carbon nanotubes in structural composites for aerospace applications is limited to date, not only by production and processing issues, but also by their lower than expected mechanical performance in polymeric materials. In a composite, the weak interaction between the nanotube and the polymer may be improved by chemical modifications (functionalization) to the carbon nanotube that improve the interface with the polymer. One way to probe the interfacial region is to examine the changes in elastic constants as a function of distance from the carbon nanotube. Elastic constants of polymer nanocomposites can then be determined for representative volume elements (RVE) of the molecular structure by using molecular dynamics simulation to calculate configurational energy changes under mechanical deformation. To understand how the nanotube affects the elastic constants of the polymer at the polymer nanotube interface, a broad range of spatial definition is required. In the present work, the elastic constants are calculated as a function of radial distance C(r) from the carbon nanotube. These interfacial elastic constants are determined directly from the energies of deformation in the MD simulation for subcomponents of the RVE. The objectives of the present work are first to describe the proposed method, and then to determine the spatial dependence of the transversely isotropic elastic constants of the polymer surrounding a carbon nanotube as a function of distance from the nanotube. The method is applied to epoxy/nanotube systems in which the nanotube may be pristine or functionalized.
9:00 PM - HH8.28
Electrical and Mechanical Properties of Nylon-12 and PETI-298 Carbon Nanotube Composites.
Melanie Morris 1 , Amy Hofstra 1 , Jennifer Sample 1
1 , Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, United States
Show AbstractIn theory nanocomposites made by incorporating carbon nanotubes (CNTs) with a polymer matrix can enhance the properties of the polymer. CNTs have uniquely high strength to mass ratio, intrinsic light weight, thermal conductivity, electrical conductivity, and chemical functionality. They have also been shown to prevent delamination and provide structural stability in nanocomposites. However, dispersion of the CNTs within the polymer matrix can affect final properties. The two polymers chosen for this study are Nylon-12 and PETI-298. Different sample preparation methods are used to try and improve the dispersion of the CNTs; dry mixing, melt mixing, in situ and solution. In addition, the use of functionalized versus non-functionalized CNTs with varying concentration levels are used. Once samples are prepared, test specimens are molded using a hot press. Spectoscopic studies, high resolution imaging, and electrical/mechanical property measurements are used to evaluate the dispersion of the CNTs and the final nanocomposite for comparisons.
9:00 PM - HH8.29
The Role of Polymer-particle Interactions on the Viscoelastic Properties of Polymer Nanocomposites.
Alireza Sarvestani 1 , Esmaiel Jabbari 1
1 Chemical Engineering, University of South Carolina, Columbia, South Carolina, United States
Show Abstract9:00 PM - HH8.3
Templated Mesoporous Silica Colloids with Controlled Internal Structures.
Weon-Sik Chae 1 , Paul Braun 1
1 Dept. of Materials Science & Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractIt is well known that lyotropic liquid crystals can template bulk silica mesophases, and since this initial discovery, it was found that when a silica mesophase is formed under one- or two-dimensional confinement, additional factors including structural frustration, interfacial interactions, and confinement-induced entropy loss strongly modulate the structure of the confined mesophase. Although considerable work has been performed on one- and two-dimensionally confined systems, there are few examples of mesoporous silica synthesis in three-dimensionally confining environments. Here, we demonstrate the synthesis of mesoporous silica in the unique and controllable three-dimensional environment of a polymer inverse opal. First a colloidal silica opal is used to form a polymer inverse opal, then, this inverse opal polymer template is used direct the structure of mesoporous silica colloids (MSCs). The effect of connectivity, surface energies, and diameter on the mesostructural organization of the confined mesophase systems was studied. As the surface energy of the polymer template is changed from hydrophilic, to intermediate, to hydrophobic, the organization of the confined mesostructure of the MSCs changes from circularly wound to pseudo-rhombohedral dodecahedral to disordered. When the average number of interconnects between cavities is decreased, the pseudo-rhombohedral dodecahedral organization is no longer observed. Such unique mesostructures formed in three-dimensional confining environments are impossible to obtain via symmetric bulk confinement, such as in solution or in the gas phase. We expect that the ability to define the organization of the mesostructure of MSCs based on the confinement induction concept may open applications where transport is important including supercapacitors, drug delivery, and catalysis.
9:00 PM - HH8.30
Bifunctional Nanostructured Layer-by-Layer Films Incorporating Pt-Nanoparticles.
Jose Siqueira 1 , Frank Crespilho 1 , Valtencir Zucolotto 1 , Osvaldo Oliveira 1
1 Physics and Materials Science Department, Physics Institute of São Carlos, São Carlos, SP, Brazil
Show Abstract9:00 PM - HH8.31
Fabrication and Characterization of High Resistant Polymeric Carbon Nanocomposites.
Renato Minamisawa 1 , Bopha Chhay 1 , Daryush Ila 1
1 , Alabama A&M University, Huntsville, Alabama, United States
Show Abstract9:00 PM - HH8.32
Self Assembled Nanocomposites for Fuel Cell Applications.
Ramasudhakar Dhullipudi 1 , Yuri Lvov 1 2 , Tabbetha Dobbins 1 3
1 Institute for Micromanufacturing, Louisiana Tech University, Ruston, Louisiana, United States, 2 Chemistry, Louisiana Tech University, Ruston, Louisiana, United States, 3 Physics, Grambling State University, Grambling, Louisiana, United States
Show Abstract9:00 PM - HH8.33
Sol-Gel Processing of Enzymatically Functional Carbon Nanotube-Based Composite Materials.
Evan Goulet 1 , David Luzzi 1
1 Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States
Show Abstract We report the production of a functionally gradient coating on carbon nanotubes (CNTs) utilizing aqueous sol-gel processing. The coating is comprised of a mesoporous network of colloidal silica particles produced under conditions that are conducive to the entrapment of enzymes within the coating. The porosity of the coating can be controlled via colloidal particle size, making the coating versatile in the types of enzymes and molecules that can be immobilized. CNTs present a high aspect ratio structure that can be utilized as a biofunctional substrate in the form of mats, suspensions, and probe configurations. Enzymatic activity of the CNT-based complex is characterized with respect to variations in pH and temperature, as well as substrate molecule concentration.
9:00 PM - HH8.34
Characterization of Interfacial Properties of Polymeric Nanocomposites.
Juntao Wu 1 , Xiaohong Gu 1
1 Materials and Construction Research Division, NIST, Gaithersburg, Maryland, United States
Show Abstract9:00 PM - HH8.35
Solid-State Shear Pulverization: A Viable Process for the Production of Well-Exfoliated and Dispersed Polymer-Clay Nanocomposites.
Cynthia Pierre 1 , John Torkelson 2 1
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States, 2 Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States
Show AbstractMany polymer-clay nanocomposites cannot be produced in the well-exfoliated state using conventional processing methods such as melt processing or in situ polymerization. Furthermore, commercial application of polymer-clay nanocomposites calls for a production method that begins from polymer and clay rather than in situ polymerization. Here we demonstrate that a continuous, industrially applicable process called solid-state shear pulverization (SSSP) can produce well-exfoliated polymer-clay nanocomposites using both homopolymers and polymer blends. The SSSP apparatus is a modified twin-screw extruder equipped with a cooling system that maintains the polymer in the solid-state throughout processing; thus, SSSP is a continuous, industrially scalable process.We show via a combination of methods, including x-ray diffraction and transmission electron microscopy, that the well-exfoliated state can be achieved via SSSP processing of polyethylene-clay and polypropylene (PP)-clay nanocomposites using both organically modified and pristine clay. Equally important is that the well-exfoliated state is stable to long-term annealing in the melt state; this means that the exfoliation can be maintained during subsequent melt processing. These well-exfoliated polymer-clay nanocomposites yield significant property enhancements such as an increase of ~30 K in the onset temperature of degradation of PP at 5 wt% loss and a 20% increase in the Young's Modulus for PP-clay nanocomposites. Other mechanical properties, oxygen permeation, and the crystallization kinetics of these nanocomposites will also be discussed.We also show through SSSP processing of various compositions of PP and polystyrene (PS) blends that well-exfoliated organoclay is present at interfacial regions of the blends. This provides a potential pathway for arresting coarsening of the dispersed PS phase during subsequent melt state processing, i.e., blend compatibilization.
9:00 PM - HH8.36
Mechanical and Electrical Characterization of Age-Hardened Waspaloy Microstructures.
Ricky Whelchel 1 , V. Siva Kumar Kelekanjeri 1 , Rosario Gerhardt 1
1 Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States
Show Abstract Nickel-base superalloys are a common material utilized in turbine blades due to their excellent mechanical properties such as high strength and creep resistance at high temperature, corrosion resistance, and low temperature ductility. These properties are ideal for the operating conditions of a turbine blade, which operate under constant stress at high temperature. Nickel-base superalloys such as Waspaloy obtain their superior strength retention properties through precipitation hardening, whereby nanometer scale precipitate phases (γ’) are formed in the nickel-rich matrix phase (γ). The current work is focused on understanding the mechanisms responsible for microstructural evolution in aged Waspaloy microstructures through both mechanical and electrical characterization. Three bars of industrial grade Waspaloy were solution treated at 1145 °C for 4 hours and subsequently quenched. The solution treated bars were subsequently aged at temperatures of 725, 800, and 875 °C for times ranging from 0.5 to 263.5 hours with frequent intermediate sampling. Electrical characterization of the heat-treated specimens was conducted via DC four-point probe resistivity measurements at room temperature. Hardness data was obtained via Vickers microhardness measurements. The four-probe resistivity increased initially upon aging at 725 and 800 °C, and then decreased progressively upon prolonged aging. At 875 °C, the resistivity initially showed a decreasing trend, followed by an increase after 1.5 hours, and then a decrease for aging times up to 263.5 hours. Hardness measurements at 800 and 875 °C show peaks at 88.5 and 1.5 hours respectively, followed by continuous decreases, whereas, the peak in hardness was not clearly attained even after 263.5 hours of aging at 725 °C. The present results indicate that DC four-point probe measurements are more sensitive to microstructural evolution during initial aging stages, whereas, hardness measurements are more useful during later aging stages. A combination of these two techniques shows a good potential for studying the kinetic phenomena that drives microstructural evolution in Waspaloy.
9:00 PM - HH8.37
Fabrication of Machinable Nano-laminated Ternary Carbides by a New Synthetic Technology.
Jae-Ho Han 1 , Kyung-Don Nam 1 , Sung-Ho Yun 1 2 , Kyung-Sun Cho 1 2 , Sung-Sic Hwang 3 , Dongyun Lee 1 , Sang-Whan Park 1
1 Metearials Science and Technology Division, Korea Institute of Science and Technology, Seoul Korea (the Republic of), 2 Department of Materials Science and Engineering, Hanyang University, Seoul Korea (the Republic of), 3 National Core Research Center for Nanomedical Technology, Yonsei University, Seoul Korea (the Republic of)
Show Abstract9:00 PM - HH8.38
Biomimetic Synthesis and Characterization of Polypyrrole and Poly(3,4-ethylendioxythiophene) / Mesoporous Silica Nanocomposites.
Paulina Roman 1 , Selene Sepulveda-Guzman 3 , Elisa Tierrablanca 2 , Jorge Romero-Garcia 2 , Rodolfo Cruz-Silva 1
1 Laboratorio de Polimeros, Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Cuernavaca, Morelos, Mexico, 3 Chemical Engineering, The University of Texas at Austin, Austin, Texas, United States, 2 , Centro de Investigacion en Quimica Aplicada, Saltillo, Coahuila, Mexico
Show Abstract9:00 PM - HH8.39
Electron Energy Loss Spectroscopy (EELS) Studies of Electron-Beam-Induced Deposition of Tungsten Nanomaterials.
Juntao Li 1 , Matthew Bresin 1 , Kathleen Dunn 1 , Bradley Thiel 1
1 College of Nanoscale Science and Engineering, University at Albany, Albany, New York, United States
Show Abstract9:00 PM - HH8.4
Electronic Properties of LaB6 Nanostructures.
Guangping Li 1 , Renat Sabirianov 1 , Jin Lu 1 , Wai Ning Mei 1 , Chin Li Cheung 2 , Xiao-Cheng Zeng 2
1 Physics, University of Nebraska at Omaha, Omaha, Nebraska, United States, 2 Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States
Show AbstractWe performed electronic structure calculations of quasi-one dimensional LaB6 nanorods with different cross-sections and nanoclusters with long and sharp edges. Our purpose is to correlate the relationship between work functions and rod shapes, which is motivated by the experimental reports that LaB6 obelisks generated stronger photoelectric current than in the bulk case. In the calculations, our samples are (i) infinite and periodic along c axis with cross-sections consist of up to ten or more unit cells, i.e. na x mb, where a, b are lattice vectors, and n x m ~ 10. (ii) Finitely long rod, i.e. na x mb x lc, with l much larger than m and n. To accomplish our calculations, we applied GGA density functional theory with ultrasoft pseudopotentials. After calculating charge densities, we deduce the density of states and the work functions of our systems. In addition, the wave functions obtained from the computation can be used to derive diffusive and ballistic transport properties thus helpful to understand the nanomaterial field emission with different tip structures and to assess their applications in electron emitter devices.
9:00 PM - HH8.41
Geometrical Study on Change of Pore Volume of MCM-41 Functionalized with Aminopropyl Groups.
Kenji Murakami 1 , Kiyoshi Fuda 1 , Mikio Sugai 1
1 , Faculty of Engineering and Resource Science, Akita University, Akita Japan
Show AbstractMCM-41 functionalized with aminopropyl groups (NH2-MCM-41) was synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyl triethoxylsilane (APTES). The amount of aminopropyl groups in the NH2-MCM-41 increased with the amount of APTES added. Values of d100 for the NH2-MCM-41 measured by X-ray diffraction were 4.1 – 4.3 nm independent of the amount of immobilized aminopropyl groups. Moreover, the NH2-MCM-41 samples were characterized by nitrogen adsorption. The pore size, surface area, and pore volume of the NH2-MCM-41 decreased with increasing the amount of immobilized aminopropyl groups. In particular, the pore volume drastically decreased from about 900 mm3/g for the MCM-41 to about 300 mm3/g for the NH2-MCM-41 (1.65 mmol-NH2/g). The nitrogen adsorption onto the NH2-MCM-41 was geometrically simulated on the assumption that a size of silica framework was constant independent of the amount of immobilized aminopropyl groups and a shape of aminopropyl group was a rigid column of 0.7 nm length and 0.5 nm diameter. The results for the case that the aminopropyl groups immobilized regularly onto the inner silica wall agreed well with the experimental results.
9:00 PM - HH8.42
Production of Complex Cerium-Aluminum Oxides Using an Atmospheric Pressure Plasma Torch.
Jonathan Phillips 1 2 , Claudia Luhrs 2 , Paul Fanson 3
1 , Los Alamos National Lab, Albuquerque, New Mexico, United States, 2 Mechanical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 3 Materials Research Department, Toyota Technical Center, USA Inc., Ann Arbor, Michigan, United States
Show AbstractNanoparticle applications, for batteries, fuel cells, catalysts, specialty solid fuels, etc, require not simply nanoparticles, but highly engineered nanoparticles. For example, in applications ranging from batteries to catalysts, there is a need for nanoparticles with a ‘core’ to do the chemical work and a shell to prevent sintering. In our work we have produced a number of novel nano structured ceramic structures using an atmospheric pressure microwave though which an aerosol containing precursor species is passed, a technique we call ‘Aerosol-through-plasma’ (A-T-P). For example, ceria-alumina particles of a wide variety of structures, from micron sized hollow spheres to core (ceria)/shell (amorphous alumina) nanoparticles, were produced. The amount of water present with the nitrate salts, the ratio of the salts, the power employed, the carrier gas flow rates, etc. were all found to significantly affect the morphology of the resulting material. In order to achieve the full applications potential of the nanoparticles better engineering is required. Of particular importance, production rate per energy expended must be increased, equipment costs must decrease, and process ‘design’ must be rationalized so that generation of particular product moves from the Edisonian to the engineered. In the talk we describe the first step in the process of engineering; the development of a successful conceptual model of nano particle formation. Next, we chart the efforts needed, including new plasma models, required to allow plasma modification of particulate materials to become a truly engineered technology.
9:00 PM - HH8.43
Effect of Morphology on Toughening Mechanisms of Layered-Silicate/Epoxy Nanocomposite.
Bahereh Tekyeh-Marouf 1 2 , Reza Bagheri 1 , Raymond Pearson 2
1 Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States, 2 Materials Science & Engineering, sharif Univeristy of Technology, Tehran , Tehran, Iran (the Islamic Republic of)
Show Abstract9:00 PM - HH8.44
Synthesis and Characterization of Nanostructured Magnesia-Yttria Based Nanocomposites.
Jafar Al-Sharab 1 , Rajendra Sadangi 1 , Vijay Shukla 1 , Bernard Kear 1
1 Ceramic and Material Science, Rutgers University, Piscataway, New Jersey, United States
Show Abstract9:00 PM - HH8.45
Computer Simulation of Nanoparticle Aggregate Fracture.
Brian Henz 1 , Takumi Hawa 2 , Michael Zachariah 3 2
1 , U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland, United States, 2 , National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 3 Department of Mechanical Engineering and the Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States
Show AbstractNanoparticle aggregates have been found to possess unique mechanical properties. Aggregates of metal nanoparticles can be strained up to 100% before failure, and even typically brittle materials are observed to have a ductile failure mode. In this effort two materials; namely gold and silicon, were chosen to represent ductile and brittle materials, respectively. Aggregates with 2 to 10 particles were simulated using the molecular dynamics (MD) algorithm to determine the stress-strain behavior of the aggregate. Various approaches to accelerate the simulated time were also investigated and are discussed in detail.Using a two nanoparticle aggregate of 5 nm diameter particles we have been able to simulate a system similar to an AFM experiment that measured the force required to separate an AFM tip from a surface after contact has occurred. This comparison shows that qualitatively the MD results are able to predict the ductile behavior of the silicon system and the jagged force versus displacement curve of the gold system. We have found the largest limitation of the computer simulations for this system to be the actual versus simulation strain rates. We are currently studying the effect of strain rate on the stress versus strain behavior of the nanoparticle aggregate. These results will provide a relationship for comparing simulation results at a high strain rate to experimental results at a much lower strain rate.Another important aggregate parameter is the primary particle diameter. The nanoparticle diameter affects many of the mechanical properties of the aggregate. Some of the parameters affected are the contact area, nanoparticle melting temperature, and sintering time. Through MD simulations we have been able to determine the relationship between nanoparticle diameter and contact area, a major determining factor in the ultimate strength of an aggregate. During the mechanical testing of the aggregate the yield strength will be reached and plastic deformation will occur. As the plastic strain increases, a neck will form and grow. The neck growth depends upon the strain rate, nanoparticle material, and other parameters that affect the surface atoms that diffuse into the neck region between nanoparticles. This diffusion maintains the neck thickness and prevents the rupture of the aggregate. The diffusion process and the neck elongation are investigated in this work.
9:00 PM - HH8.46
Distant-ion Dragging of Polarizable Nanodroplets and Solvated DNA on Nanotubes.
Boyang Wang 1 , Petr Kral 1
1 Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractWe present by molecular dynamics simulations the solvation of ions at nanometerseparations from polarizable nanodroplets [1]. The ions are intercalated insidesemiconducting single-wall carbon nanotubes (SWNT) and dressed by 20-800 watermolecules adsorbed on their surfaces. Application of electric fields on theions allows easy manipulation of the nanodroplets attached to them. We alsodemonstrate that solvated single-strand DNA molecules adsorbed on SWNTs canbe driven by ionic solutions flowing inside the tubes, similarly like ionsand polar molecules in vacuum [2]. These novel phenomena can be applied inbio-molecular delivery, separation, desalination and other technologies.[1] Boyang Wang and Petr Kral, submitted.[2] Boyang Wang and Petr Kral, JACS 128, 15984 (2006); submitted.
9:00 PM - HH8.47
Nanostructured Indium Tin Oxide For Application In Opto-electronic Devices.
S. Fernando 1 , N. Gerein 1 , M. Brett 1
1 Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractIn glancing angle deposition (GLAD), physical vapour deposition and controlled substrate rotation are combined to produce nanostructured thin films composed of distinct columns, resulting in arrays of helices, chevrons, or slanted posts. The process provides precise control over film morphology at the nano-scale and enables order-of-magnitude increases in surface area. For this reason, the application of GLAD to indium tin oxide (ITO) – a transparent conductor – is expected to lead to significant performance improvements in opto-electronic devices such as displays. However, it is difficult to fully characterize such films due to their unique morphology – standard characterization methods are historically tailored for use with solid thin films. Here we report the electrical characterization of nanostructured electrodes with average density less than 50% of a bulk film. The GLAD process was used to fabricate nanostructured indium tin oxide (ITO) electrodes exhibiting enhanced surface area. These consisted of arrays of short posts approximately 50 nm tall and 50 nm in diameter, grown on top of a solid ITO film. UV-visible spectrophotometry was used to assess the optical transmittance of the electrodes, while their chemical composition and crystal structure were evaluated using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. A variety of novel techniques were used to measure the electrical properties of the films, both parallel to the substrate and parallel to the posts, and allowing for the determination of the resistivity of individual ITO posts.
9:00 PM - HH8.48
A Wet-Chemical Route to ZnO Nanowire Array/Nanoparticle Composite Films.
Jih-Jen Wu 1 , Hung-Hsien Yang 1 , Chen-Hao Ku 1
1 Department of Chemical Engineering, National Cheng Kung University, Tainan Taiwan
Show AbstractZnO nanowire (NW)-layered basic zinc acetate (LBZA)/ZnO nanoparticle (NP) composite films with different NP occupying extents have been synthesized using a simple wet-chemical route, i.e., aligned ZnO NW array first formed by an aqueous chemical bath deposition (CBD) and then heterogeneous nucleation and growth of LBZA/ZnO NPs on the surface of ZnO NWs by another base-free CBD. The features of the composites from three-dimensional NW-nanosheet networks, dense NW-NP composite film to NW-NP composite film with flower-like particles are able to be obtained easily by varying the NP growth period. HRTEM analyses indicate that there is no epitaxial relationship between the ZnO NW and ZnO NPs, suggesting that heterogeneous nucleation of LBZA structure on the surface of the ZnO NWs is crucial for the formation of the NW-NP composite using the base-free route. In addition, ZnO NW array/TiO2 NP composite films have been successfully synthesized using a similar wet-chemical route as well. Photovoltaic measurements of the ZnO NW array/NP composite dye-sensitized solar cells will be discussed in the presentation.
9:00 PM - HH8.49
Synthesis and Sensing Properties of Tungsten Oxide Nano-particle Thin Films.
Tim Huelser 1 2 , Pascal Ifeacho 2 , Hartmut Wiggers 2 , Axel Lorke 1
1 Department of physics and CeNIDE, Universität Duisburg-Essen, 47057 Duisburg Germany, 2 Institute of combustion and gas dynamics, and CeNIDE, Universität Duisburg-Essen, 47057 Duisburg Germany
Show AbstractThe sensing mechanism of solid-state gas sensors is based on the change of the electrical properties with changing gas environment. This is attributed to the adsorption of atoms and molecules on the inorganic semiconductor surface, which affects properties such as conductivity and surface potential. The scientific work on solid state gas sensors increasingly focuses on high surface-to-volume ratio that is to say nano-sized materials. Tungsten oxide (WO3) is a suitable material for gas-sensing applications and is known to be a very promising candidate with high selectivity for air pollutants like NO/NO2, CO/CO2 and ethanol. Tungsten oxide nanoparticles particles are synthesized in a low pressure premixed flame reactor using WF6 as precursor material. The parameters can be adjusted to synthesize WOx particles with 2.6 < x < 3. Thin films of particles in the size range from 5 nm to 9 nm deposited on interdigital structures are investigated by AC-methodsElectrical measurements of the as-prepared sensors are performed between 553 K and 583 K. The data from DC measurements reveal a good sensitivity S=Rair/Rgas for CO and NO under dry synthetic air. For NO a sensitivity of S = 4.3 and in the case of CO S = 2.9 is reached at 583 K. We observe a fast response time for both species within the first 120 seconds after the addition of the gases, followed by a slower, but dominant, increase of sensitivity during further measurements. A detailed analysis of the data reveals a faster response time as well as a better sensitivity for NO. The short response time within the first seconds is usually not seen with common micro-sized WO3 sensors and may be attributed to the high surface to volume ratio of the nano-sized oxide.To investigate and separate the sensitivities of the core (volume) and the grain-boundaries (surface) in detail impedance spectra have been measured and analyzed by means of sophisticated fitting algorithms. This analysis reveals two contributions to the overall impedance, which can be assigned to the core and the grain boundary conduction process. The resistances obtained from fit results have been used to determine the different sensitivities (grain-boundary and core) on NO and CO.The core contributions reveal a decrease of sensitivity with rising temperature for CO, and an increasing sensitivity for NO. Additionally, much higher sensitivities (up to S=12) for CO are observed for grain boundary processes compared to the corresponding bulk sensitivities, while the temperature behaviours of grain boundary and core sensitivities are clearly different. These results received from AC and DC investigations suggest a fast sensing mechanism at the particle surface with an excellent response time and a distinct slower process within the core.
9:00 PM - HH8.5
Investigation of Nano-thin Beta-SiC Layers for Chemical Sensors.
N. Shelton 1 , Ronak Rahimi 1 , Dinesh Penigalapati 1 , Andrew Balling 1 , D. Korakakis 1 , Srikanth Raghavan 2 , Andrew Woodworth 2 , Tobias Denig 2 , Charter Stinespring 2
1 Lane Department of Computer Science & Electrical Engineering, West Virginia University, Morgantown, West Virginia, United States, 2 Department of Chemical Engineering, West Virginia University, Morgantown, West Virginia, United States
Show Abstract9:00 PM - HH8.50
Inorganic Nanocrystal–based Inverters and Nano-floating Gate Memory Devices Fabricated on Flexible Substrates.
Jaewon Jang 1 , Kyoungah Cho 1 , Jeonggwon Yun 1 , Sangsig Kim 1
1 , Korea University, Seoul Korea (the Republic of)
Show AbstractTransparent and flexible inverter logic gates and floating gate memory devices were fabricated on poly-ether-sulphone (PES) substrates in this work. In the inverter logic gates, two thin film transistors composed of sintered HgTe nanocrystal films as active layers were connected on the PES substrates coated with cross-linked poly-4-vinlyphenol (C-PVP). In order to isolate and form active layer on the surface of C-PVP buffer layers, the conventional photo-lithography and an UV/ozone treatment were employed. When the substrate was flat, a representative inverter revealed the signal swing (VH-VL) of 10 V and the gain of 1.0. When the substrate was bent until the bending radius of the substrate reaches 2.4 cm which corresponded to a strain of 0.7% the HgTe thin film experienced, the flexible inverters exhibited similar values. On the contrary, for the flexible floating gate memory devices, sintered HgTe nanocrystal films and Pt nanoparticles were used as active layers and floating gate layers, respectively. The Pt nanocrystal layer was formed by spin-coating on the tunneling oxide layer which was deposited on sintered HgTe layer, followed by deposition of control oxide layer with 60 nm. In the both cases of flat and bent substrates, the fabricated flexible memory devices revealed a shifted threshold voltage of 2~3 V and retention time of 10000 sec.
9:00 PM - HH8.51
Nanowire-array Based Thin Films for Energetic Applications.
Eugen Panaitescu 1 , Latika Menon 1
1 Physics, Northeastern University, Boston, Massachusetts, United States
Show Abstract9:00 PM - HH8.52
Cu Rich Nanostructured Alloys with Enhanced Mechanical Properties.
K. Georgarakis 1 , K. Ota 1 , A. LeMoulec 1 , F. Charlot 1 , A. Yavari 1
1 SIMAP - CNRS, Institut National Polytechnique de Grenoble, Saint-Martin-d'Hères France
Show AbstractNew copper rich alloys with elemental additions of transition metals and group IIIA and IVA elements have been prepared by casting and rapid solidification. The prepared alloys showed very interesting microstructures; a thick surface layer was observed to form with nanocrystalline eutectic like structure, while in the bulk the microstructure was coarser lamellar or dendritic. Their microhardness was found to be exceptionally high for Cu rich alloys, reaching values of 450-550HV. Furthermore, the microhardness of the surface layer was higher than that in the bulk, indicating that these alloys can be considered for a variety of applications including tribological and structural applications. In situ tensile tests in a scanning electron microscope (SEM) and compression tests were employed in order to study the mechanical properties of the prepared alloys. Their mechanical strength was found to be remarkably high, presenting the best combination of mechanical strength and ductility ever reported for copper rich alloys. The deformation and fracture mechanisms were investigated by in-situ SEM observations and ex-situ examination of the fractured surfaces.
9:00 PM - HH8.53
Self-ordered Anodic Aluminum Oxide (AAO) Formed by Sulfuric Acid Hard Anodization (HA).
Kathrin Schwirn 1 , Woo Lee 1 , Reinald Hillebrand 1 , Martin Steinhart 1 , Kornelius Nielsch 1 , Ulrich Goesele 1
1 , MPI of Microstructure Physics, Halle, Saxony-Anhalt, Germany
Show Abstract9:00 PM - HH8.54
UV-reactive Monolayers of Aryl Esters on Oxidic Surfaces: Patterning and Chemical Surface Modification via Photo-Fries Rearrangement.
Thomas Hoefler 1 , Bernhard Basnar 2 , Julius Cirac 3 , Thomas Griesser 1 , Gregor Hlawacek 7 , Helmuth Hoffmann 2 , Quan Shen 7 , Jaroslav Kovac 3 , Michael Ramsey 4 , Alexander Satka 6 , Christian Teichert 7 , Susanne Temmel 5 , Anna Track 4 8 , Gregor Trimmel 1 , Egbert Zojer 8 , Wolfgang Kern 1
1 Institute for Chemical Technolgy of Organic Materials , Graz University of Technology, Graz Austria, 2 Institute for Applied Synthetic Chemistry, Vienna University of Technology, Vienna Austria, 3 Departement of Microelectronics, Slovac University of Technology, Bratislava Slovakia, 7 Institute of Pysics, Montanuniversitaet Leoben, Leoben Austria, 4 Institute of Experimental Physics, Graz University, Graz Austria, 6 , International Laser Center, Bratislava Slovakia, 5 , Polymer Competence Center, Leoben Austria, 8 Institute of Solid State Physics, Graz University of Technology, Graz Austria
Show AbstractIn previous works it was demonstrated that the photo-Fries rearrangement causes a large increase of the refractive index (between +0.03 and +0.05) in polymeric materials [1]. Moreover, the surface chemistry changes significantly as aryl esters of carboxylic acids are transformed into ortho-hydroxy ketones [2]. The present contribution describes surface layers obtained with molecules A-B-C, where A is a photoreactive group (aryl ester), B is a spacer unit (alkylene chain) and C is an anchoring group for oxidic surfaces (trichlorosilyl). In particular, mono- and oligolayers of acetic acid, [4-(trichlorosilyl-alkyl)phenyl ester] are assembled on oxidized Si surfaces. The surface film properties are characterised by ellipsometry, AFM, XPS, FTIR, SEM, contact angle as well as by zeta potential measurements. The progress of the photoreaction is monitored by enhanced internal reflexion and external reflection IR spectroscopy. In both cases the monolayer films are sandwiched between two high refractive index materials, which increases signal intensity. The photoreaction in the surface layer also increases the surface polarity as evidenced with contact angle measurements. In a similar fashion, electrokinetic measurements (zeta potential) are used to follow the progress of the photoreaction. The OH groups generated by the photoreaction are employed for further derivatization, e.g. with acid chlorides. Selective coupling of metal ions in the irradiated zones is also demonstrated. Using contact masks, lithographic patterning of the surface layers is achieved. The surface structures are investigated by friction force AFM. Summing up, the properties and the reactivity of a surface can be tuned in a wide range when photoreactive surface layers are employed. [1] T. Höfler, T. Griesser, X. Gstrein, G. Trimmel, G. Jakopic, W. Kern, “UV reactive polymers for refractive index modulation based on the photo-Fries rearrangement”, Polymer 48, 1930-1939 (2007).[2] T. Griesser, T. Höfler, S. Temmel, W. Kern, G. Trimmel, "Photolithographic patterning of polymer surfaces using the photo-Fries rearrangement: selective post-exposure reactions”, Chem. Mater. 19, 3011-3017 (2007).The present work was funded by the Austrian Science Fund FWF (Vienna) within the National Research Network (NFN) on "Interface Controlled and Functionalized Organic Films" (project S9702-N08). finacial support was also provided by the bilateral Austria-Slovakia project No.57s08.
9:00 PM - HH8.55
Growth of Nano-grained Indium Thin Films by Cryogenic Sputtering.
Jung-Hyun Park 1 , Dong-Joo Kim 1
1 Material Engineering, Auburn Univerity, Auburn University, Alabama, United States
Show AbstractUnderstanding the role of grain boundaries on the electrical and optical properties of films is critical to the success of many envisioned applications of nanocrystalline materials. Synthesis of thin films composed of controlled nanophase grains are still under investigation. This study is focused on indium since this material can be is attractive for potential applications in specific narrow band pass filters, electrodes for organic display, seeding materials for In2O3 nano wire-based devices. Indium has been deposited on amorphous substrate cooled at cryogenic temperature by a sputter deposition method, and process parameters have been investigated for atomic-scale control of structure during film formation. The resizing of grain from micro to nano scale in indium films was made possible, and grains with about 50 nm of average diameter were uniformly formed in three dimensions.. Scanning electron microscope (SEM) was used to identify their microstructural evolution. Scanning probe microscopy (SPM) was also utilized to quantify structural change. Electrical and optical properties of indium films consisting of nanograined indium films were characterized. Low sheet resistances were obtained in much thinner films deposited in cryogenic, and reflectance of films was varied depending on the size of grain in the film. Mechanism of growth is discussed by correlating the structure with process parameters.
9:00 PM - HH8.56
Nanocomposite Transition Metal Oxide Films for Thin Film Battery and Electrochromic Applications.
Dane Gillaspie 1 , Se-Hee Lee 1 , C. Tracy 1 , Roland Pitts 1
1 , National Renewable Energy Laboratory, Golden, Colorado, United States
Show AbstractImproving energy efficiency and energy storage are two of the major enabling technologies that will make it possible to maximize the amount of renewable, carbon-neutral power that can be used. In this talk I will discuss a nanocomposite material that shows promise in both technology regimes.We have grown novel nanocomposite transition metal oxide films using multiple vacuum deposition techniques. The structure of the resulting films has been characterized using x-ray diffraction and electron microscopy. These films have a large, reversible charge capacity when cycled in a lithium cell. The capacity of the composite films compares favorably to literature results for lithium manganese oxides and lithium cobalt oxides. The films also show strong anodic electrochromic activity. This is especially true in the most visible wavelengths from 400-700nm. This means these films could be excellent candidates to use as the counter-electrode in energy-efficient electrochromic windows.
9:00 PM - HH8.57
Characterization of Polymer Materials Through Transmission Ellipsometry.
Georgi Georgiev 2 1 , Yaniel Cabrera 1 , Brian Feinberg 1 , Peggy Cebe 1
2 Department of Natural Sciences, Assumption College, Worcester, Massachusetts, United States, 1 Physics Department, TUFTS University, Medford, Massachusetts, United States
Show AbstractWe are exploring the effects of nucleating agents, nanoparticles like carbon nanotubes and organically modified silicates on the crystallographic phase of polymer materials. As a result of different processing conditions different crystallographic forms and different degree of perfection of polymer crystals result. Those material forms and their characterization are important for developing polymer materials with new useful properties. The advantages of transmission optical ellipsometry are that it is a quick and convenient analytical method for materials characterization. Through measuring the azimuthal angle orientation of the fast optical axis relative to a reference direction of ordered structures and their effect on optical retardation R it is proving rich information about the internal structure of the material, the crystallographic form, the crystal orientation, and the degree of perfection of the crystals. The retardance is calculated using Stokes analysis of measured intensity transmitted through the sample. R is equal to (2π/λ)dΔn, where λ is the wavelength of incident light, d is film thickness, and Δn is the birefringence. This is a real time, two dimensionally resolved technique with spatial resolution of 1μm, and retardance resolution greater than λ/1000. The wavelength used in these studies is 550nm. Research supported by: the National Science Foundation, Polymers Program grant (DMR-0602473) and NASA grant (NAG8-1167).
9:00 PM - HH8.58
Nanostructured Photoresponsive Polymers Based on Azobenzene Liquid Crystalline Elastomers.
John Koval 1 2 , Timothy White 2 3 , Timothy Bunning 2 , Richard Vaia 4 , Nelson Tabirian 5 , Svetlana Serak 5 , Vladimir Grozhik 5
1 Materials Science and Engineering, University of Illinois, Champaign, Illinois, United States, 2 , AFRL/MLPJ, Wright Patterson AFB, Ohio, United States, 3 , General Dynamics IT, Wright Patterson AFB, Ohio, United States, 4 , AFRL/MLBP, Wright Patterson AFB, Ohio, United States, 5 , BEAM Co., Winter Park, Florida, United States
Show AbstractPhotoresponsive polymers made from liquid crystalline monomers with azobenzene linkages have been previously shown to exhibit polarization dependent actuation with illumination with 442-532 nm laser lines. Recently, we have imparted nanostructure onto these materials using holographic photopolymerization. This work will compare and contrast the properties of holographically nanostructured azobenzene liquid crystalline elastomers to materials made with floodlit photopolymerization.
9:00 PM - HH8.59
Co-Sputtered Nanocomposite Thin Films of Platinum / Yttria Stabilized Zirconia for Solid State Electrochemical Applications.
Joshua Hertz 1 2 , Harry Tuller 1
1 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland, United States
Show Abstract Since the discovery of high temperature ionic conductivity in yttria-stabilized zirconia (YSZ), platinum has been used in conjunction as a chemically stable and electrochemically active electrode. It has long been believed that the electrode half-reactions in such a system occur preferentially in the local vicinity of the triple phase boundary (TPB), the common intersection of the electron-conducting, ion-conducting, and gas phases. A nanocomposite of platinum and YSZ would thus be highly advantageous since it would result in a large interaction length between the two solid phases and thus a very large TPB length per unit area of surface. Since both electrons and ions must access the TPB, a bicontinuous, interpenetrating network of platinum and YSZ grains is required. Here we report on the production of thin film composite electrodes with nanometric grains of platinum and YSZ. The films were reactively co-sputtered in a single step, using DC sputtering with a platinum target and RF sputtering with an yttrium/zirconium alloy target. Composition was successfully controlled by adjusting the relative sputtering powers. The films were structurally and chemically characterized over a range of deposition conditions. The substrate temperature was found to play a large role in the structural characteristics. In addition, a few of the films were electrochemically characterized by forming microelectrodes of various sizes onto single crystal yttria-stabilized zirconia. The activation polarization resistance exhibited an activation energy of 1.3-1.5 eV and was found to have an approximate inverse dependence on microelectrode radius squared, consistent with mixed ionic-electronic conductivity. Area specific polarization resistances of less than 500 Ω×cm2 were achieved at 400°C in a dense thin film electrode. The attractiveness of these nanocomposite electrodes for use in microfabricated solid oxide fuel cells, of interest as portable power sources, is discussed.
9:00 PM - HH8.6
Synthesis and Structural Transformation of Luminescent Nanostructured Gd2O3:Eu Produced by Solution Combustion Synthesis.
Luiz Jacobsohn 1 , Brytan Bennett 1 , Ross Muenchuasen 1 , Stephanie Sitarz 1 , James Smith 1 , D. Cooke 1
1 Materials Science & Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractIn this work we explore the uniqueness of solution combustion synthesis (SCS) technique to produce luminescent nanostructured materials with metastable phases. We synthesized Gd2O3:Eu with the high-temperature phase and induced phase transformation toward the room temperature phase to investigate the effects of structural transformation on the luminescent properties. SCS is based on exothermic redox reactions that undergo self-sustaining combustion, yielding powders composed of agglomerates of nanocrystals with typical dimensions of tens of nanometers. Synthesis of materials through SCS occurs in conditions far from thermodynamic equilibrium and, due to the high temperatures achieved during combustion, metastable crystallographic phases can be formed. Eu-doped Gd2O3 was obtained with base-centered monoclinic structure and average nanocrystal size of 35 nm as determined by Debye-Scherrer analysis. Phase transformation to the cubic structure was induced by isothermal annealing at 1000 oC for up to 152 hrs and followed by x-ray diffraction (XRD). Luminescence excitation and emission spectra were obtained as a function of annealing time. The transformation from monoclinic to cubic structure was followed by the behavior of the (111) monoclinic/(222) cubic intensity ratio. The ratio value for the as-prepared material is 6, decreasing fast to 3 after 5 hrs. annealing, and reaching a value of 0.1 after 152 hrs. Concomitant to the structural transformation, nanocrystal size was followed for both crystalline phases. The average nanocrystal size for the cubic phase increases from 27 to 47 nm from 1 to 152 hrs., respectively. On the other hand, nanocrystals with the monoclinic phase remained with a constant size around 38 nm. Overall, variation in size is small due to the low connectivity among nanocrystals resulting from the low uniaxial pressure employed to prepare the pellets, together with the non-uniform shape of the agglomerates. Photoluminescence excitation spectra are dominated by a broad band centered near 278 nm and assigned to the O2—Eu3+ charge transfer band. Photoluminescence emission results present the 5D0-7FJ (with J = 0-4) transitions of Eu3+ ions. The behavior of these bands was investigated as a function of annealing time and subsequently related to the structural changes.
9:00 PM - HH8.60
Formation of Nanoscale Refractory Carbide Films and Particulates with A Vapor Phase Transport Method.
Dajie Zhang 1 , Jennifer Sample 2
1 Advanced Technology Laboratory, Johns Hopkins University, Baltimore, Maryland, United States, 2 Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, United States
Show Abstract9:00 PM - HH8.62
Shear Resistance of CuNb Bimaterial Interface.
Jian Wang 1 , Richard Hoagland 1 , Amit Misra 1
1 , LANL, Los Alamos, New Mexico, United States
Show AbstractLayered composites of Cu/Nb with individual layer thicknesses less than 10 nm achieve very high strength levels attributable to the interfaces acting as barriers to slip. When a dislocation reaches an interface in these composites, the core spreads within the interface. This spreading effectively traps a dislocation making it very difficult to transmit into the adjacent layer. The knowledge of shear resistance and shear response of interfaces are important to enable us to capture how the dislocation core spreads within the interface and the interaction between the gliding dislocations and bimaterial interfaces. In this paper, we describe the shear resistance and shear response of two types of CuNb interfaces. The first, referred to KS-1, is formed by directly combining two semi-infinite perfect crystals having the Kurdjumov-Sachs (KS) orientation relationship. The second, referred to KS-2, is formed by inserting a strained Cu monolayer as an intermediate layer between the adjoining crystals in the KS-1 interface. The results reveal that (1) the shear resistance is strongly anisotropic in both interfaces. (2) The KS-1 interface has much higher shear resistance than the KS-2 interface. (3) When the applied shear stresses reaches the critical level needed to induce irreversible sliding along the bimaterial interfaces, the slip only occurs in the interface between Cu crystal and Nb crystal for KS-1, but for KS-2 occurs in two interfaces, between the Cu monolayer and Nb crystal, and between the Cu monolayer and Cu crystal. (4) Shear resistance is not uniform in the interface. As a result core spreading quite complex within the interface. This work was supported by DOE, Office of Basic Energy Sciences.
9:00 PM - HH8.63
Synthesis of Metal-MoS2 Nanostructures by High Power Pulse Ion Ablation.
Somuri Prasad 1 , Tim Renk 2 , Paul Kotula 3 , Tarasankar Debroy 4
1 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 2 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 3 , Sandia National Laboratories, Albuquerque, New Mexico, United States, 4 , The Pennsylvania State Universityen, University Park, Pennsylvania, United States
Show Abstract9:00 PM - HH8.64
V2O5/TiO2/Ag Thin Films for Visible Light Photocatalysis.
Kerri-Ann Hue 1 2 , Hassan El-Shall 1 2
1 , University of Florida, Gainesville, Florida, United States, 2 Particle Engineering Research Center, University of Florida, Gainesville, Florida, United States
Show AbstractThe increase in germicidal-resistant strains of infectious microorganisms, as well as drug toxicity to patients, has made it necessary to investigate new methods of microbial inactivation. Nanocomposite materials have garnered a lot of attention for their improved electrical, optical, photochemical, and germicidal properties. Many researchers have reported nanomaterials that are capable of inactivating microorganisms. For example, semiconductor photocatalysts, specifically titanium dioxide (TiO2), have been successfully used for the reduction of viable microorganisms using ultraviolet (UV) light. An ideal photocatalyst would inactivate using longer wavelengths of light, i.e. visible light. To achieve this goal photocatalytic nanocomposite materials have been synthesized. TiO2 nanoparticles and thin films have been doped with noble elements, other semiconductors, and polymers to achieve visible light photocatalysis. A nanocomposite thin film, comprised of vanadium pentoxide (V2O5), TiO2 and silver nanoparticles, was synthesized using sol-gel processing techniques. Statistitical design of experiments was used to (1) determine the synthesis parameters that most significantly affect the quality of the film produced and to (2) optimize the thin film. To confirm optimization band gap, crystal structure, porosity, surface area, and dye degredation were measured using characterization techniques such as Electron Microscopy, X-Ray Diffraction, UV-Visible Spectroscopy, physisorption techniques, and thermal analysis.
9:00 PM - HH8.66
Nanoscale Structuring to Control Fracture.
Marian Kennedy 1 , Ryan Cates 3 , David Bahr 3 , Neville Moody 2
1 Material Science and Engineering, Clemson University, Clemson, South Carolina, United States, 3 School of Mechanical and Materials Engineering, Washington State University , Pullman, Washington, United States, 2 , Sandia National Laboratory, Livermore, California, United States
Show AbstractA broad range of devices, from microelectronics to NEMS, use thin films to form composite structures. The films in these multilayer structures commonly have nm thickness which has been shown to influence the mechanical properties of these films, such as strength and hardness. These alterations in mechanical properties are due to several mechanisms including dislocation pile-up, interface strengthening and changes in chemical bonding due to short-range diffusion. Another property that can be affected by control of plasticity is the practical adhesion energy or interfacial fracture energy. This study will look at the influence of nanoscale structures along the Pt/Si interface, their consequential effects on film plasticity and resulting influence on the measured fracture energy. Specifically, this study will look the effects of changing the nano structure’s shape, size and placement along the interface. Two types of structure have been deposited on (100) Si including Si domes and polymer tubes. Both of these structures are near 100nm in diameter. The influence of these structures will be compared to a uniform Pt/Si interface, which has been measured to have a fracture energy of 1.7 J/m2.
9:00 PM - HH8.67
Influence of the Electron Injection on the Light Emission Characteristics of Si Nanocrystals in a Silicon Nitride Film.
Chul Huh 1 , Kwan Sik Cho 1 , Kyung-Hyun Kim 1 , Jongcheol Hong 1 , Jae-Heon Shin 1 , Gun Yong Sung 1
1 , Electronics and Telecommunications Research Institute, Daejeon Korea (the Republic of)
Show AbstractRecently, silicon nanocrystals (nc-Si) embedded in a dielectric matrix has attracted a great interest due to their potential for applications in silicon-based micro-photonics because the nc-Si has the advantage of enhanced radiative recombination rate and large band gap up to the visible range due to a quantum confinement effect. Our group previously reported that well-organized nc-Si embedded in a silicon nitride matrix grown by a conventional plasma enhanced chemical vapor deposition system could emit from the near infrared to the blue region depending on the size of nc-Si, which showed a clear quantum confinement effect. In addition, we fabricated the prototype nc-Si light-emitting diode (LED) by employing the n-type SiC and indium tin oxide layers as a transparent doping layer and current spreading layer, respectively. To realize efficient nc-Si LEDs, an investigation on the device structure to further enhance the carrier injection into the nc-Si should be needed. In the present work, we have investigated the effect of an introduction of the undoped SiC layer between active Si nanocrystal layer and n-type SiC layer on performance of the nc-Si LEDs. The average size and dot density of nc-Si were around 4 nm and 6.0×1011 cm2, respectively. The electrical property of nc-Si LED with an undoped SiC layer was much superior to that of the nc-Si LED without an undoped SiC layer above 2 factors of magnitude. Moreover, the output power of the LED with an undoped SiC layer was enhanced more than 2 factors of the magnitude over all voltage ranges investigated, compared to that of the LED without an undoped SiC layer due to an enhancement of the carrier injection into the active layer containing the nc-Si. A detailed investigation of the performance of the nc-Si LEDs will be presented.
9:00 PM - HH8.68
Bioinspired Design of Dental Multilayers: Experiments and Models.
Nima Rahbar 1 2 , Xinrui Niu 3 2 , Stephen Farias 3 2 , Wole Soboyejo 3 2
1 Civil Engineering, Princeton University, Princeton, New Jersey, United States, 2 Princeton institute for the science and technology of materials, Princeton University, Princeton, New Jersey, United States, 3 Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey, United States
Show Abstract9:00 PM - HH8.69
New Polypropylene-boron Oxide Composite with a High Tensile Strength: A Possible Method for the Conversion of Microcomposite to Nanocomposite.
S. Chopra 1 , Changfeng Ge 3 , K. Song 4 , Kalathur Santhanam 1 2
1 Center For Materials Science and Engineering, Rochester Institute of Technology, Rochester, New York, United States, 3 Packaging, Rochester Institute of Technology, Rochester, New York, United States, 4 , ExxonMobil Chemical Company, Macedon, New York, United States, 2 Department of Chemistry, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractAn industrially viable composite having a microstructure that can be converted into a nanostructure material by post chemical treatments potentially holds a commercially viable solution to the development of many new nanostructure materials. Such nonomaterials will find useful applications in nanosensors, nano power, material degradation, neutron shield, heat transfer and packaging . In this regard a polypropylene-boron oxide composite provides a model study for the post conversion of the material. Polypropylene-boron oxide is a less studied composite in comparison to polypropylene-boron nitride In this paper we wish to report the synthesis of polypropylene-boron oxide composites with different concentrations of boron oxide by melt grafting and through reactive extrusion. The tensile strengths of the ideal composite has been found to be several times higher than polypropylene. By chemically treating the composites for a period of 24 hours to 72 hours the tensile strength of the composites changed by 11-15%. The composites have been characterized by Fourier transform infra red spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Recently, a similar increase in tensile strength has been observed with polypropylene/multiwalled carbon nanotubes composites where the tensile strength increased by five times over polypropylene. The increased tensile strength has been attributed to the conversion of micro structured composites to nanostructure ones. A thermogravimetric analysis (TGA) of the boron oxide composite shows an improved thermal stability by about 50oC and a further shift of 40oC after the chemical conversion. The improvement in the thermal stability can be attributed to polypropylene-boron oxide interaction. An interesting characteristic of this composite has been the development of a gradient surface potential that changes upon visible light excitation.
9:00 PM - HH8.7
Influence of the Time-Temperatur-Profile on Powder Characteristics of Nanocrystalline Anatase (TiO2) produced by Chemical Vapor Synthesis.
Ruzica Djenadic 1 3 , Shankanilay Roy Chowdhury 1 3 , Maryna Spasova 2 3 , Cedrik Meier 2 3 , Markus Winterer 1 3
1 Faculty of Engineering, University Duisburg-Essen, Duisburg Germany, 3 CeNIDE, University Duisburg-Essen, Duisburg Germany, 2 Faculty of Physics, University Duisburg-Essen, Duisburg Germany
Show AbstractChemical Vapor Synthesis (CVS) is the conversion of molecular species into nanocrystalline particles by chemical reactions in a gas flow reactor. The time-temperature-profile in the gas phase of the reactor has a profound influence on the particle characteristics such as particle microstructure and surface chemistry and, therefore, on the quality of the powder consisting of nanocrystalline particles. Pure anatase nanoparticles are generated in a hot wall reactor from titanium isopropoxide using different time-temperature-profiles. The powder characteristics are analysed in detail using nitrogen adsorption, X-ray diffraction, dynamic light scattering, FTIR spectroscopy and transmission electron microscopy. The powders show a very high degree of crystallinity, small particle size and a low degree of agglomeration.
9:00 PM - HH8.71
Synthesis of Dumbbell-like Fe3O4-NM (NM = Au, Ag, AuAg) Nanoparticles.
Youngmin Lee 1 , Chao Wang 1 , Shouheng Sun 1
1 Chemistry, Brown University, Providence, Rhode Island, United States
Show Abstract9:00 PM - HH8.8
Size Dependent Elastic Constants of a Layer-structured Nanometal.
Theodoros Karakasidis 1 , C. Charitidis 2 , D. Skarakis 2
1 Civil engineering, University of Thessaly, Volos Greece, 2 School of Chemical Engineering, National Technical University of Athens, Athens Greece
Show Abstract9:00 PM - HH8.9
Ultra Flame Resistant Polymer Electrospun Nanofibers Containing Halogen-Free 4,4’-Bishydroxydeoxybenzoin.
SungCheal Moon 1 , BonCheol Ku 1 , Todd Emrick 1 , E. Coughlin 1 , Richard Farris 1
1 Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, United States
Show AbstractHighly oriented yarns of nanofibers of 4,4’-bishydroxydeoxybenzoin(BHDB)-polyphosphonate were prepared and characterized for their mechanical and thermal properties. After optimizing the polymer concentrations and related experimental conditions, electrospun nanofibers with a consistent fiber diameter of ~100 nm could be spun without beads or cracks. High yarn orientation was achieved by collecting filaments made from concentrated BHDB-polyphosphonate solutions (up to 70 wt %) onto a rapidly rotating electrically grounded cylindrical target. The measured heat release capacity (HRC) of these BHDB nanofibers was exceptionally low, (~70 J/(g K)) and the char yield was 53 %. These values are comparable to highly flame resistant aramid fibers such as Nomex. The electrospun nanofibers of BHDB-polyphosphonate were capable of being drawn approximately 50% and displayed good mechanical strength (~78 MPa) and modulus (~2.9 GPa). These novel materials are of interest in a number of applications including flame resistant textiles, porous membranes, and aerospace applications.
Symposium Organizers
Sridhar Komarneni The Pennsylvania State University
Katsumi Kaneko Chiba University
John C. Parker Cabot Microelectronics Corporation
Paul O'Brien University of Manchester
HH9: Nanocomposite and Nanostructured Materials
Session Chairs
Thursday AM, November 29, 2007
Room 302 (Hynes)
9:30 AM - HH9.1
Bottom-Up Assembly of Colloidal Platelets into Bio-Inspired Composite Films.
Lorenz Bonderer 1 , Andre Studart 1 , Ludwig Gauckler 1
1 , ETH Zurich, Zurich, ZH, Switzerland
Show AbstractThe controlled assembly of organic and inorganic materials is expected to enable the fabrication of novel composite materials with enhanced properties. Nacre is one example from nature of how a highly tough material can be produced by combining inorganic and organic materials at different length scales. In this study we present a method to prepare thin film composites consisting of highly ordered alumina platelets with interlayers of organic phase. The films were assembled layer-by-layer using the Langmuir-Blodgett technique. Firstly, the platelets are homogeneously adsorbed to an air-water interface and subsequently transferred onto a substrate by dipping. Secondly, a thin polymer film is deposited on the top of the platelets by spin coating. Different synthetic and biological polymers were investigated. SEM images showed a very well ordered nacre-like layered structure. Texture analysis by XRD confirmed the almost perfect alignment of the basal plane of the platelets perpendicular to the direction of the film thickness. Focused ion beam tomographies showed the tight bonding between the ceramic platelets and the polymer without pores. The mechanical properties of the composites strongly depended on the organic-inorganic interface. For optimally tailored interfaces, the composite is up to 4 times stronger and stiffer than the polymer whereas the plasticity was decreased only by 25 %. Both the tensile strength and the strain at break of the composite exceeded the values from nacre. When illuminated from the side, the composites showed iridescent colors similar to those of nacre. The main features of this technique to mimic biological inorganic-organic structures will be discussed and perspectives for further improvements will be presented.
9:45 AM - HH9.2
Nanocomposites for Electromagnetic Applications via 3D Self-assembly.
Amit Goyal 1 , S. Wee 1
1 Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge , Tennessee, United States
Show AbstractNanocomposites comprising ordered 3D arrays of nanodots of one type of ceramic material coherently embedded in another ceramic matrix comprise a novel class of materials for wide-ranging applications. Such materials are expected to exhibit novel physical properties tunable by adjusting the overall composition, concentration, feature size and spatial ordering of the nanodots. Such nanocomposites have potential applications in many areas such as photovoltaics, solid state lighting, ultra-high density storage and high temperature superconductivity. We report here on achieving 3D ordering via 3D self-assembly of nanodots of a complex ceramic material within another complex ceramic material, such as 3D self-assembly of BaZrO3 nanodots in REBCO superconducting films. Examples will also be given for other ceramic and metal/ceramic systems. In all cases 3D self-assembly was obtained in epitaxial thick films grown via pulsed laser ablation on single-crystal or single-crystal-like substrates. Research was sponsored by the U.S. Department of Energy under contract DE-AC05-00OR22725 with the Oak Ridge National Laboratory, managed by UT-Battelle, LLC.
10:00 AM - HH9.3
CVD Deposition of Alumina-mullite Nano-composite Coatings.
Tushar Kulkarni 1 , H. Wang 1 , S. Basu 1 , V. Sarin 1
1 Manufacturing Engineering, Boston University, Brookline, Massachusetts, United States
Show AbstractAlthough chemical vapor deposited mullite (3Al2O3.2SiO2) environmental barrier coatings have shown promise in protecting Si-based substrates for gas-turbine applications, there is concern that the silica content within the mullite coating itself might be susceptible to hot-corrosion and recession during long term exposure to corrosive atmospheres. There is thus a strong motivation to substantially reduce or even virtually eliminate the silica from the surface of the mullite coatings that are in direct contact with atmospheres containing corrosive oxides and steam.Functionally graded mullite coatings have been grown and the composition has been tailored in these coatings, with the Al/Si ratio being stoichiometric (~ 3) at the coating/substrate interface for coefficient of thermal expansion (CTE) match, and increasing monotonically towards the outer coating surface. These functionally graded coatings have some of the highest Al-rich mullite reported to date at the coating surface. At these extremely high Al/Si ratios, formation of nano-sized high-alumina mullite grains occurs. High-resolution transmission electron microscopy has been used to characterize the structure and composition of this nano-composite region. The structure and phase transformations in this nano-composite region will be discussed.
10:15 AM - HH9.4
Gaseous Deposition of Lead Sulfide Nanoparticle/Conducting Polymer Composite Films.
Adam Zachary 1 , Igor Bolotin 1 , Daniel Asunskis 1 , Amanda Wroble 1 , Luke Hanley 1
1 Chemistry, University of Illinois at Chicago, Chicago, Illinois, United States
Show AbstractComposite materials composed of inorganic semiconductor nanocrystals (NCs) dispersed in organic matrices may find use in photovoltaics, photodiodes, nonlinear optical devices, and other applications. This interest arises from the possibility of tuning the optoelectronic properties of the composite by varying the NP size and concentration within the organic matrix. Bulk PbS is a group IV–VI semiconductor with a narrow band gap of 0.41 eV at room temperature. Strong quantum size effects occur for <20 nm PbS NCs. Among the other potential advantages of PbS NCs is their high electron affinity, which will enhance charge transfer from an intermingled organic phase. Most of the lead salt NP photovoltaics devices produced to date have been prepared from the solution phase using colloidal techniques. However, gaseous deposition techniques possess certain advantages for the synthesis of nanocomposites: it is inherently suited to film deposition, is compatible with traditional methods of fabricating semiconductor devices, allows control of oxidation during deposition, and it can reduce the agglomeration of NCs. This work demonstrates that gaseous deposition can synthesize a composite film with <5 nm diameter PbS NCs of narrow size distribution embedded within titanyl phthalocyanine (TiOPc) and sexithiophene (6T) organic matrices. Composite film samples were fabricated here using a cluster beam deposition source combining magnetron DC-sputtering and gas-agglomeration techniques in a fashion similar to that originally developed by Haberland and coworkers. X-ray photoelectron spectroscopy showed that PbS was successfully incorporated into both matrices-TiOPc and 6T-during co-deposition. Transmission electron microscopy (TEM) was used measure the size, shape, distribution, and crystallinity of the NCs in these composite films. Soft-landing of PbS clusters into the organic matrices allowed the clusters to maintain their three-dimensional structure upon deposition. In the absence of the TiOPc matrix, PbS showed the aggregation into much larger, irregularly-shaped particles. PbS NCs appeared homogeneously distributed in both TiOPc and 6T with particle spacings of several times the particle diameter. TEM also showed that at least some NCs deposited into TiOPc were crystalline. This method also allows for deposition of composite films composed of any evaporable organic and inorganic nanoparticles that can formed by sputtering and reaction within the cluster source.
10:30 AM - HH9.5
Layer-by-Layer Assembly of Novel Nanocomposites from Cellulose Nanocrystals.
Paul Podsiadlo 1 , Lang Sui 2 , Bong Sup Shim 1 , Yaseen Elkasabi 1 , Peter Burgardt 1 , Jaebeom Lee 6 , Ashwini Miryala 1 , Winardi Kusumaatmaja 1 , Mary Carman 5 , Max Shtein 2 , John Kieffer 2 , Joerg Lahann 2 3 4
1 Chemical Engineering Department, University of Michigan, Ann Arbor, Michigan, United States, 2 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 6 Nanomedical Engineering, Pusan National University, Busan Korea (the Republic of), 5 Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, United States, 3 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract Cellulose nanocrystals (NCs) are emerging as a new class of reinforcing material for the preparation of high performance nanostructured composites. The combination of their natural and renewable origins with exceptional mechanical properties: bending strength ≈ 10 GPa and E ≈ 150 GPa, make them an attractive nanomaterial for the preparation of low cost, light-weight, and ultra-strong hybrid composites for multitude of applications. Unlike carbon nanotubes (CNTs), their exceptional properties (only 6-7 times lower then those of single walled CNTs) are thus far largely unexplored and currently described nanocrystal reinforced composites possess far lower properties then theoretically achievable. We present here preparation of thin film composites from cotton (100-300 nm long) and/or tunicate (a marine animal, several microns long) NCs with different polyelectrolytes using the layer-by-layer (LBL) electrostatic assembly technique. We present our results from the evaluation of mechanical properties of the thin films both with standard stretching technique and Brillouin light scattering. LBL assembly of the cotton NCs with poly(diallyldimethylammonium chloride) (PDDA), results in nanocomposites with ultimate tensile strength, σUTS ≈ 40 MPa and Young’s modulus, E ≈ 2 GPa (as high as 10 GPa from Brillouin light scattering). Post-assembly thermal-treatment increases σUTS to ≈ 130 MPa without a change in E. We also show that LBL assemblies of tunicate NCs possess strong antireflection (AR) properties, having an origin in a novel and highly porous architecture reminiscent of a “flattened matchsticks pile”, created by randomly-oriented and overlapping NCs. At an optimum number of LBL deposition cycles, light transmittance reaches nearly 100% (λ ~400 nm) when deposited on a microscope glass slide and the refractive index is ~1.28 at λ = 532 nm. This first example of LBL layers of tunicate NCs can be seen as an exemplary structure for any rigid axial nanocolloids, for which given the refractive index match, AR properties are expected to be a common property. Similarly, the films exhibit exceptional mechanical properties with E reaching as high as 30 GPa.
11:15 AM - HH9.6
Novel Synthesis of Opto-Thermal Responsive Polymer-Metal Nanocomposites.
Jose Morones 1 , Wolfgang Frey 2
1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States, 2 Biomedical Engineering, University of Texas at Austin, Austin, Texas, United States
Show AbstractGreat interest has arisen to develop nanocomposites by coupling nanoparticles of noble metals with “intelligent materials”, materials that can react to an external stimulus and perform a desired mechanical or physicochemical action. Nanoparticles of noble metals have interesting optical, electrical, thermodynamic and chemical properties, many of which have a strong dependence on the particle size and shape, and the electronic configuration of the metal. These particles produce highly localized fields associated with surface plasmon resonances at distinct dipole, quadrupole and higher multiple resonances. The plasmon absorption is followed by thermal dissipation of the photon energy and the heat is transferred into the local surroundings. This allows metal nanoparticles to act as amplifiers or modulators of an external optical stimulus, which makes these nanocomposits interesting for use in biomedical applications such as drug delivery vehicles and tissue engineering. Here we demonstrate the synthesis of an optothermal responsive composite of metallic nanoparticles, gold and silver, with an environmentally-sensitive polymer, p(N-isopropylacrylamide) (PNIPAM). The synthesis takes advantage of the polymer capable of acting as a nucleating and capping agent for in situ synthesis of the metallic particles, as well as being an environmentally sensitive actuator. The ability of PNIPAM to cap the metal nanoparticles and control the growth process, and therefore the size, is strongly dependant on the concentration ratio with the metal ion, gold or silver. TEM studies show that we can control the growth process to form highly monodisperse colloidal suspensions with spherical shape particles. The product obtained not only has a narrow distribution of particle sizes, it additionally is a composite, which is temperature-sensitive, without further conjugation for PNIPAM typical LCST of 32 °C, as well as responsive to the absorption wavelength of the metallic nanoparticles, 520 nm for gold and 415 nm for silver. We have developed a novel synthesis of a metal-polymer nanocomposite with light and temperature response. All of these processes are reversible, and the system can be cycled several times.
11:30 AM - HH9.7
Carbon Nanotube – Unsaturated Polyester Resin Composites.
Virginia Davis 1 , Matthew Kayatin 1 , Devin Jones 2 , Robert Yuan 2
1 Dept. of Chemical Eng., Auburn University, Auburn, Alabama, United States, 2 Dept. of Civil Engineering, Lamar University, Beaumont, Texas, United States
Show Abstract Carbon nanomaterials have tremendous potential as structural reinforcements in polymers both with and without the inclusion of traditional materials such as glass fibers. We have investigated unsaturated polyester resin (UPR) property enhancements in resulting from the incorporation of single-walled carbon nanotubes (SWNTs), vapor grown carbon fiber (VGCFs), and sidewall functionalized single-walled carbon nanotubes (R-SWNTs). Two methodolgies were explored: 1) dispersing the nanomaterial into the unsaturated polyester and 2) Resin impregnation of VGCF, SWNT, and R-SWNT films (Bucky-papers). It is well known that the potential for property enhancement is determined by both the degree of nanotube dispersion throughout the composite material and adhesion between the nano-reinforcement and resin matrix. For this reason, the performance of materials made with SWNTs and R-SWNTs were compared. The R-SWNTs were produced by oxidizing purified HiPco SWNTs with HNO3/H2SO4 to create carboxyl (-COOH) functionalization. The functionalization was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA)/Mass Spectroscopy, Atomic Force Microscopy (AFM), and Raman Spectroscopy.The dispersions of SWNTs, R-SWNTs, and VGCF in UPR were first examined pre-cure to determine the relationship between structure, processing conditions, and resulting composite properties. The microstructure of the carbon nanomaterial-UPR systems was characterized by rheology and microscopy. Correlations between variation in bulk viscosity and dynamic modulus were established with respect to the degree of nanotube dispersion. The UPR impregnated Bucky-papers produced were evaluated by SEM prior to vacuum assisted resin impregnation for uniformity. Various lay-up geometries were produced with and without the addition of glass fibers. The mechanical properties of these composite materials are discussed and related to morphology of the bulk composite and fracture surfaces.
11:45 AM - HH9.8
Fabrication of Multiwall Carbon Nanotube-nanocrystalline Copper Nanocomposite Film by Electrochemical Deposition.
JungJoon Yoo 1 , JaeYong Song 2 , Jin Yu 1
1 Dep. of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 Division of Advanced Technology, Korea Research Institute of Standards and Science, Daejeon Korea (the Republic of)
Show Abstract Nanocomposite materials of polymers, ceramics and metals are expected to have more excellent electrical, thermal and mechanical properties when being combined with carbon nanotube (CNT). To date, there are many studies of incorporating CNTs into various metal matrices such as Cu, Ni, and Al, etc., in order to improve the mechanical properties and, recently, a few successful results; e.g. a bulky nanocomposite of copper-CNT produced by a sintering process in high temperature and pressure has a nanocrystalline structure composed of well-dispersed CNTs in nanocrystalline copper matrix showing higher modulus and hardness. In present study, we developed a new method of fabricating nanocomposite films made up of multiwall carbon nanotube (diameter 10 ~ 40 nm, length > 1 µm) and nanocrystalline copper by using an electrochemical deposition, which is a low cost and low temperature process. There are several important factors in fabricating nanocomposite thin films with good quality. One is a homogeneous dispersion of carbon nanotubes in metal matrix. They should be well dispersed in the depth direction as well as the planar direction to the substrate. The other is a densification of CNTs and metal matrix, i.e. CNTs should be embedded in the matrix without voids. We introduce the effects of several amphiphilic polymers and organic additives on the dispersion of CNTs in the Cu matrix and the variation of nanocrystalline structure of Cu matrix. The experimental parameters such as CNTs concentration in the solution, frequency, and amplitude of current pulse wave were used to control the microstructure and composition of nanocomposite films. Results showed that the composition was varied by current amplitude and CNTs concentration in the solution. CNTs were well dispersed in both the planar and depth directions to form void-free nanocomposite films. The enhanced mechanical and electrical properties such as hardness, modulus and resistivity of nanocomposite films are introduced with the variation of CNTs concentration and compared with the other studies. The nanocomposite films are expected to be used for the application as interconnecting and thermal interface materials of electronic devices.
12:00 PM - HH9.9
A Superhydrophobic and Conductive Coating Fabricated from Carbon Nanotubes Dispersed in a Conjugated Block Copolymer Solution.
Jianhua Zou 1 , Qun Huo 1 , Lei Zhai 1
1 Nanoscience Technology Center, University of Central Florida, Orlando, Florida, United States
Show AbstractA superhydrophobic and conductive nanocomposite coating with an average water contact angle between 155-160o was fabricated from multiwalled carbon nanotubes dispersed in poly (3-hexylthiophene)-b-polystyrene block copolymer solution. By casting the dispersion on substrates and followed by quick drying, the nanotube-block copolymer mixture naturally formed a honeycomb structure with microscale features. The hierarchical combination of micro-scaled honeycomb structure with nano-scaled MWCNTs provides the cast films with superhydrophobicity. The superhydrophobic coating can be formed on a wide range of substrates including gold, aluminum foil, graphite, plastics, paper, glass and silica wafer. The conductivity of the thin film coating falls in the range of 10-100 S/cm depending on the composition of the dispersion. The nanocomposite material reported here meets the requirements of many potential applications such as electromagnetic interference (EMI) shielding and electrostatic dissipation.
12:15 PM - HH9.10
Tridimensional Microstructures of SWCNT Reinforced Polymer Nanocomposite by Means of a Microfluidic Infiltration Approach.
Louis Laberge Lebel 1 , Brahim Aissa 2 , My Ali El Khakani 2 , Daniel Therriault 1
1 Mechanical Engineering, Ecole Polytechnique of Montreal, Montreal, Quebec, Canada, 2 , INRS - Energy, Materials and Telecommunications, Varennes, Quebec, Canada
Show AbstractWe report the successful fabrication of 3D microstructures of SWCNT/polymer nanocomposite by using a new approach based on the infiltration of microfluidic 3D networks with a polymer loaded with various contents of SWCNTs. The microfluidic network is first fabricated by direct-write assembly. This approach consists in the robotised micro-extrusion of cylindrical fugitive ink micro-rods on an epoxy substrate to form a 3D structure. After infiltration of the deposited structure with an epoxy resin, the fugitive ink is removed by heating, resulting in a 3D network of microchannels. After proper cleaning, this microfluidic network is then infiltrated by a UV-curable polymer loaded with SWCNTs. The single-wall carbon nanotubes (SWCNTs) were produced by the UV-laser ablation method, physico-chemically purified and appropriately dispersed in a polymer matrix using ultrasonic treatment in dichloromethane. The infiltrated nanocomposite (i.e.; SWCNT reinforced polymer) is then cured under UV exposure followed by heat post-curing. Flexural mechanical testing was performed on 3D microstructures consisting of rectangular sandwich beams having an epoxy core and nanocomposite fibers placed parallel to the beam axis, on both sides of the core. The mechanical results are presented for microfluidic channels of different diameters and a constant cross-sectional area. On the structural level, the nanocomposite beams were also characterized by means of Raman spectroscopy and scanning electron microscopy (SEM and TEM). The nanocomposite infiltration of microfluidic networks is shown to be a very promising approach to achieve 3D microstructures of reinforced nanocomposites.
12:30 PM - HH9.11
Carbon Nanotube Reinforced Ceramic Coatings.
Abhishek Kothari 1 , Brian Sheldon 1 , Janet Rankin 1 , Eres Gyula 3 , Zhenhai Xia 2
1 Engineering, Brown university, providence, Rhode Island, United States, 3 Center for nanophase materials and science, Oakridge national laboratory, Oakridge, Tennessee, United States, 2 Mechanical Department, University of Akron, Akron, Ohio, United States
Show AbstractCarbon nanotubes hold significant potential to toughen ceramic coatings. Multiwalled nanotube preforms were first prepared by catalytic decomposition of acetylene at 700C. Silicon nitride was then infiltrated using dichlorosilane and ammonia in low pressure (200 mTorr) at 720C to obtain dense coatings reinforced with nanotubes. A simple Thiele modulus calculation guided the efforts to minimize residual porosity in composite coatings that were up to 30 μm thick. Thicker coatings (200-400 μm) were also formed from nanotube preforms that were obtained from patterned islands. This permitted better gas transport into the nanotube array. In some cases, standard lithographic techniques were used to first deposit iron in a predetermined pattern (these were then annealed to enable nanotube growth). This patterned CNT growth also allowed us to infiltrate nanocrystalline diamond after a thin layer of silicon nitride was formed. This made it possible to produce relatively thick nanocrystalline diamond coatings that were reinforced with nanotubes. Fracture surfaces of both silicon nitride and diamond matrix coatings showed extensive nanotube pull out, up to 50 times the CNT diameters (evidence of pull out is a qualitative indication of toughening). The composite coatings were also indented with a cube corner tip (nanoindentation), and crack lengths were then used to calculate the fracture toughness. This analysis was based on a finite element model that accounts for residual stress and the bridging contribution provided by the nanotubes. The results show that the nanotubes significantly improved the toughness of these ceramic coatings. Acknowledgement : This research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.
12:45 PM - HH9.12
Metallized Nanotube Polymer Composite (MNPC).
Cheol Park 1 , Jae-Woo Kim 1 , Godfrey Sauti 1 , Jin Ho Kang 1 , Peter Lillehei 2 , Sharon Lowther 2 , Joycelyn Harrison 2 , Negin Nazem 3 , Larry Taylor 3
1 , Nat Inst of Aerospace, Hampton, Virginia, United States, 2 Advanced Materials & Processing Branch, NASA Langley Research Center, Hampton, Virginia, United States, 3 Chemistry, Virginia Tech, Blacksburg, Virginia, United States
Show AbstractThe incorporation of more composites into aircraft structures offers benefits of weight savings and fuel efficiency. However, it presents a significant challenge with respect to electromagnetic shielding and lightning protection as compared to traditional metallic structures. The large mismatch in electrical conductivity between the composite matrix resin and carbon fiber reinforcement can lead to serious damage in composite structures from lightning strikes and interference in aircraft systems from other electromagnetic effects (EME). Here we present a metallized nanotube polymer composite (MNPC) which can provide sufficient electrical conductivity to shield aircraft structures from EME while providing mechanical reinforcement. The MNPC is primarily composed of a lightweight polymer resin, highly reinforcing nanotubes, and metallized nanoparticles incorporated by supercritical fluid infusion. Each component of the MNPC plays a unique role in making the composites suitable for harsh flight conditions. The selected polyimide matrix provides weight reduction, thermal stability, and mechanical durability at elevated temperatures. Superstrong nanotube inclusions such as single wall carbon nanotubes offer additional mechanical reinforcement and electrical conductivity. Incorporation of the nanotubes also decreases the coefficient of thermal expansion of the polymer composite to match more closely with those of reinforcing carbon fibers and non-replaceable metal frame structures at elevated temperatures. Further augmentation of electrical conductivity to reach the level necessary for lightning protection and electromagnetic interference shielding is achieved by incorporating metallic nanoparticles into the nanotube-polymer composites using a supercritical carbon dioxide fluid impregnation method. In this presentation, the morphology and electrical/dielectric properties of MNPC will be discussed as a function of nanotube and metallic content and metal infusion conditions.
HH10: Nanocomposites
Session Chairs
Sridhar Komarneni
Greta Patzke
Thursday PM, November 29, 2007
Room 302 (Hynes)
2:30 PM - HH10.1
Synergistic Physical Properties of Multiphase Nanocomposites with Carbon Nanotubes and Inorganic Particles.
Jan Sumfleth 1 , Luis Prado 1 , Katja Leckband 1 , Malte Wichmann 1 , Karl Schulte 1
1 Institute of Polymers and Composites, Technische Universität Hamburg-Harburg, Hamburg, Hamburg, Germany
Show AbstractNanoparticles are considered to posses a high potential to improve the properties of polymeric materials. The comprehension and exploitation of this potential are far from being complete, especially for novel nanoparticles, such as carbon nanotubes. The potential differs with different types of nanoparticles. The dispersion of fumed silica leads to a strong influence of the rheological properties of liquid polymers, thus it is possible to tailor their processing properties. Others, e.g. titanium dioxide, improve the resistance to ultraviolet light. Carbon nanotubes (CNT) can implicate an electrical conductivity to epoxies with resulting conductivities of up to 10-2 S/m for filler contents of about 0.5 wt. % of carbon nanotubes. Percolation threshold could be found below 0.1 wt.-%. In addition, carbon nanotubes can improve the mechanical properties of polymeric systems. An increase of up to 45% in fracture toughness could be observed for only small amounts auf double-wall carbon nanotubes in an epoxy matrix without a decrease in other mechanical properties (Young’s modulus, tensile strength, strain to failure). The application of different types of nanoparticles in a polymeric matrix leads to a multiphase structure and can change the state of dispersion drastically, thus several important material properties can be improved.In the present work, multiphase epoxy-nanocomposites based on multi-wall carbon nanotubes (MWCNT) and inorganic nanoparticles (SiO2 and TiO2) were produced with a highly effective shear mixing process including a three roll mill. TEM-investigations reveal different microstructures for different combinations of particles, e.g., MWCNT/SiO2 or MWCNT/TiO2 due to different interactions between the nanoparticles themselves. The rheological and electrical properties were investigated in order to reveal detailed informations about these interparticle interactions. Synergistic effects can be found for MWCNT/SiO2 nanocomposites regarding a decrease in viscosity compared to MWCNT nanocomposites. Due to changes in the formation of the percolated MWCNT-network, the electrical conductivity is decreased if the concentration of the non-conductive fillers exceeds a critical value.The fracture toughness can be increased twice as much for multiphase nanocomposites compared to dualphase nanocomposites because of an improved state of dispersion. Thermo-mechanical properties are suspected to be correlated with the actual curing behaviour as to be found in DSC analysis. The presence of nanoparticles leads to a chemical inactivation of reactive groups of the matrix. Thus, the generated interphase between matrix and nanoparticles exhibits a lower curing degree which results in lower thermo-mechanical properties. For the multiphase systems the glass transition temperature is decreased less due to a self assembly of the different types of nanoparticles which leads to a higher curing degree of the interphase.
2:45 PM - HH10.2
New Fabrication Technique of V2O5 Nanorod/polyvinyl Alcohol (PVA) Composite Fibers and their Electrical Properties.
Jae Woo Lee 1 , Kang-Ho Lee 1 , Jeong-Min Lee 1 , Gye Tae Kim 1 , Alan Dalton 2
1 Electrical Engineering, Korea University, Seoul Korea (the Republic of), 2 Electronics & Physical Sciences, University of Surrey, Surrey United Kingdom
Show AbstractA simple fabrication technique of V2O5 nanorod/polyvinyl alcohol (PVA) composite fibers was developed by drawing composite wires from the membrane layer floating between PVA solution and acetone separated by the difference of the density. Because of the chemical reaction at the interface between PVA and acetone layer, a thin layer of the membrane film was clearly observable. The drawn wires from the floating membrane layer could be rolled up similar with the case of nylon fibers. The well-dispersed PVA solution with V2O5 nanorods was essential for the homogeneous composite fibers. The non-linear current-voltage characteristics of V2O5 nanorods/PVA composites were noticeable at room temperature with the hysterical current-voltgae characteristics, indicating the possible contribution of the ionic current through the composite fibers.
3:00 PM - HH10.3
Fabrication of Transparent, Highly Conductive Conjugate Polymer-Silver Nanoparticle Composite Films.
Sreeram Vaddiraju 1 , David Kusters 1 , Karen Gleason 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractFabrication of transparent and highly conductive conjugated polymer-silver nanoparticle composites was accomplished by sandwiching silver nanoparticles in oxidative chemical vapor deposited (oCVD) conducting copolymer thin films. The conjugated polymer films were obtained by copolymerization of either ethylenedioxythiophene (EDOT) or pyrrole, with a monomer having the carboxylic acid functionality. Monomer with carboxylic acid functionality, either thiophene-3-carboxylic acid or thiophene-3-acetic acid was employed for this purpose. Iron chloride (FeCl3) is used as the oxidizing agent for the oCVD process. This copolymerization helped in obtaining highly conductive copolymer films, with –COOH functional groups on the surface. The presence of carboxylic acid functional group in the obtained films was confirmed using FT-IR and XPS analyses. Four-point probe measurements showed that the obtained copolymer films are highly conductive and have conductivities as high as 200 S/cm. Preliminary results, with silver nanoparticle attachment to the copolymer films, indicated that the inclusion of silver nanoparticles (100 nm in diameter) in the copolymer films led to a two-fold increase in the conductivity. The presence of silver in the copolymer films was confirmed by scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) absorption spectroscopy. These highly conductive, transparent films are very useful in the fabrication of flexible organic electronic devices.
3:15 PM - HH10.4
Structure-Property Relationship of Model Epoxy Nanocomposites.
Luyi Sun 1 2 , Jae Boo Woong 1 , Abraham Clearfield 2 , Hung-Jue Sue 1
1 Polymer Technology Center, Department of Mechanical Engineering, Texas A&M University, College Station, Texas, United States, 2 Department of Chemistry, Texas A&M University, College Station, Texas, United States
Show Abstract3:30 PM - HH10.5
Use of Sonication and Influence of Clay Type on the Enhancement in Physical Properties of Poly(methyl methacrylate) Nanocomposites.
Sharon Ingram 1 3 , Hugh Dennis 3 , Ian Hunter 3 , John Liggat 1 , Craig McAdam 1 , Richard Pethrick 1 , Carl Schaschke 2 , Sylwia Staszczak 1 , David Thomson 2 3
1 Pure and Applied Chemistry, University of Strathclyde, Glasgow United Kingdom, 3 , Carron Phoenix Limited, Falkirk United Kingdom, 2 Department of Chemical and Process Engineering, University of Strathclyde, Glasgow United Kingdom
Show Abstract4:15 PM - HH10.6
Mechanisms Leading to Enhanced Mechanical Properties in Polymer Clay Nanocomposites.
Debashis Sikdar 1 , Shashindra Pradhan 1 , Kalpana Katti 1 , Dinesh Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show Abstract4:30 PM - HH10.7
Morphology and Mechanical Properties of Amorphous Polyamide/Nanoclay Nanocomposites.
Xingui Zhang 1 , Leslie Loo 1
1 Chemical and Biomedical Engineering, Nanyang Technological University, Singapore Singapore
Show AbstractAmorphous polyamide nanocomposites with well-exfoliated montmorillonite nanoclay particles have been successfully prepared for the first time by melt compounding. The polymer matrix is a semi-aromatic polyamide produced by the polycondensation of an aliphatic diamine and an aromatic dicarboxylic acid. It is found that processing conditions and the type of organic surfactant present on the nanoclay played an important role in achieving high levels of clay dispersion. Wide-angle X-ray diffraction and transmission electron microscopy were employed to characterize the morphology in the nanocomposites. Tensile tests were also performed on dogbone specimens to evaluate mechanical properties. The structure-property-processing relationships for the nanocomposites have been explored. Nanocomposites derived from pristine clay resulted in nanoclay aggregation and did not exhibit improvement in Young’s modulus and tensile strength compared with the neat polymer. Nanocomposites prepared from organoclays containing phenyl groups and hydrogen-bonding had well-exfoliated morphology, leading to dramatic increase in Young’s modulus and an increase in yield strength.
4:45 PM - HH10.8
Ultra-Strong and Ultra-Stiff Polymer Nanocomposites: Clear Competitors.
Paul Podsiadlo 1 , Amit Kaushik 2 , Bong Sup Shim 1 , Anthony Waas 3 2 , Ellen Arruda 2 6 , Nicholas Kotov 1 4 5
1 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Aerospace Engineering, University of Michigan, Ann Arbor, Michigan, United States, 6 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show Abstract5:00 PM - HH10.9
New Core/shell Ta2O5-PMMA Nanocomposites for Applications as Polymer Waveguides.
Dorothee Szabo 1 , Rolf Ochs 1 , Sabine Schlabach 1 , Ritzhaupt-Kleissl Eberhard 1 , Thomas Hanemann 1
1 Institut fur Materialforschung III (IMF III), Forschungszentrum Karlsruhe, Eggenstein-Leopoldshafen, Baden-Wuerttemberg, Germany
Show Abstract5:15 PM - HH10.10
In-situ Coating of Rutile TiO2 Nanoparticles with SiO2 by Flame Spray Pyrolysis.
Alexandra Teleki 1 , Martin Heine 1 , Sotiris Pratsinis 1
1 Department of Mechanical and Process Engineering, ETH Zurich, Zurich Switzerland
Show AbstractFreshly-formed Al-doped TiO2 particles of high rutile content were coated with SiO2. A solution of TTIP in xylene containing small fraction of Al-trisec butoxide was combusted to form mostly rutile TiO2-nanoparticles in an enclosed flame spray pyrolysis (FSP) reactor by a quartz glass tube. Downstream of the FSP nozzle, hexamethyldisiloxane (HMDSO) vapor was introduced through a metal ring tube at various heights above the burner resulting in SiO2/Al2O3/TiO2 particles. The as-prepared powders were characterized by transmission/scanning electron microscopy, elemental mapping, energy dispersive X-ray analysis, X-ray diffraction, FT-IR (DRIFTS) spectroscopy, nitrogen adsorption and zeta potential measurements. The low levels of alumina promoted rutile formation in the titania core particles [1] while it did not alter particle size or its surface (IEP) properties significantly. Depending on the location of the ring delivering the HDMSO vapor, these particles were encapsulated by smooth and rather homogeneous silica coatings of controlled thickness. In contrast, premixing the precursors for Si/Al/Ti in FSP synthesis, resulted in mostly anatase particles segregated in amorphous and crystalline domains as with vapour fed-flame synthesis of such mixed oxides [2]. The anatase promotion of silica is significantly reduced as HDMSO is added after alumina/titania particle formation. [1] Akhtar, M.K., S.E. Pratsinis, and S.V.R. Mastrangelo, “Vapor-phase synthesis of Al-doped titania powders,” J. Mater. Res. 9, 1241-1249 (1994). [2] Teleki, A., S.E. Pratsinis, K. Wegner, R. Jossen, and F. Krumeich, “Flame-coating of titania particles with silica,” J. Mater. Res. 20, 1336-1347 (2005).
5:30 PM - HH10.11
High Strength Cu/Nb Nanocomposite Wires Processed by Severe Plastic Deformation: Effects of Size and Composite Structure on Mechanical Properties.
Vanessa Vidal 1 , Ludovic Thilly 2 , Florence Lecouturier 3 , Pierre-Olivier Renault 2 , Steven Van Petegem 4 , Helena Van Swygenhoven 4
1 , CEMES, Toulouse France, 2 Lab. Metallurgie Physique, University of Poitiers, Futuroscope France, 3 , LNCMP, Toulouse France, 4 , Paul Scherrer Institute, Villigen Switzerland
Show AbstractCopper-based high strength nanocomposite wires reinforced by Nb nanotubes are prepared by severe plastic deformation, applied with an Accumulative Drawing and Bundling process (ADB), for the windings of high pulsed magnets. The ADB process leads to a multi-scale Cu matrix containing up to N=85^4 (52.2 10^6) continuous parallel bcc tubes with diameter down to few tens nanometers. After heavy strain, The Nb nanotubes exhibit a homogeneous microstructure with grain size below 100 nm and <110> texture. The Cu matrix presents a complex microstructure with bimodal grain size distribution and duplex texture (<111>, <200>). These conductors possess elevated strength originating from a controlled access to nanometre scale, increased Cu-Nb interfaces surface (dislocations barriers), and whiskers behaviour for the Cu nanofibers inside the Nb nanotubes (Scripta Mat 57 (2007) 245).Multiple tensile loading-unloading cycles have been performed under synchrotron beam on such nanocomposite wires: the macroscopic stress-strain curves exhibit strong hysteresis (Bauschinger effect). X-ray diffraction has the advantage that the strains in both phases can be examined separately and simultaneously: the continuous following of elastic strains and peak profiles versus applied stress evidenced the co-deformation behavior with different elastic-plastic regimes. The Cu matrix exhibit size effect in the finest channels while the Nb nanotubes remain elastic up to the macroscopic failure, with a strong load transfer from the Cu matrix onto the Nb nanotubes. The yielding of large Cu channels upon macroscopic unloading was evidenced and could be related to the build-up of internal stresses because of large yield stress mismatch in the nanocomposite structure and to the dislocation storage in the different phases (APL 90 (2007) 241907).
5:45 PM - HH10.12
Size Effects on the Plastic Deformation of Nanocomposites Prepared from SiCN and SiCNAlYO Nanopowders Synthesized by Laser Pyrolysis.
Nathalie Herlin-Boime 1 , Romuald Dez 1 , Jean Louis Besson 2 , Dominique Porterat 1 , Cecile Reynaud 1
1 SPAM-LFP (CEA-CNRS URA 2453), CEA Saclay, CEA, Gif/Yvette Cedex France, 2 , SPCTS, Limoges France
Show AbstractIn material science, the ability to create nanoparticles with finely controlled characteristics is very important for the manufacture of nanostructured materials. This paper deals with the specific case of Si3N4/SiC structural ceramics, for which it is highly important to obtain hard materials exhibiting plastic deformation at high temperature. Such materials would make it easier to manufacture geometrically accurate parts, comparable to those produced for metal. In silicon nitride based ceramics, the small size and the "spherical" shape of the grains constituting the material are two important parameters in favour of high temperature deformation. Therefore, SiCN nano-sized powders are real candidates as starting materials to elaborate dense Si3N4/SiC nanocomposites exhibiting the microstructure required for ductility at high temperature.In this study, we demonstrate the possibility to prepare by CO2 laser pyrolysis of gaseous or liquid precursors SiCN nanopowders with very good thermal stability which can be used to elaborate dense nanocomposites by hot pressing sintering, and that the plastic deformation of the final nanomaterial depends directly on the grain size. SiCN nanopowders with different chemical compositions and characteristics (degree of crystallisation, thermal stability…) have been synthesized by aerosol laser pyrolysis. Characteristics of powders such as chemical composition, morphology, structure and thermal stability are reported as a function of synthesis parameters, such as chemical nature of the precursor and laser power. A correlation between synthesis conditions of powders and their thermal stability is established, and the best conditions determined. Dense nanocomposites have been obtained by hot pressing sintering under 35 MPa at 1600°C after mixing with commercial sintering aids nanopowders. The grain size of the final nanomaterial is shown to be strongly dependant on the elaboration process, and values in between 60 and 200 nm were obtained. The ductile behaviour of several samples has been studied through compressive creep tests and we evidence a strong effect of the grain size. True strain up to 45% have been obtained under 180 MPa, at 1350°C, under air, for the smallest grain size.Finally, SiCNYAl nanopowders have been synthesized in a one-step process through laser pyrolysis of an aerosol containing also precursors of the sintering aids (Al, Y). The powders have been characterized by TGA and HRTEM, they exhibit a good thermal stability up to 1500°C and all the elements (Si,C,N,Al,Y,O) are present in every grain of powder. Dense materials (100 % of the theoretical density) with nanometric structure have been elaborated from these powders by hot pressing without any preparation step of the powders. This study proves the interest of laser pyrolysis for the synthesis of powders which can be directly sintered without preparation step.
HH11: Poster Session: Nanophase, Nanocomposite and Naostructured Materials II
Session Chairs
Katsumi Kaneko
Sridhar Komarneni
Paul O'Brien
John Parker
Friday AM, November 30, 2007
Exhibition Hall D (Hynes)
9:00 PM - HH11.1
Shape-controlled Conversion of β-Sn Nanocrystals into Intermetallic M-Sn Nanocrystals.
Nam Hawn Chou 1 , Raymond Schaak 1
1 , Penn State University, State College, Pennsylvania, United States
Show Abstract9:00 PM - HH11.10
Synthesis and Microstructure of Chemically Anisotropic Nanoparticles.
Eric Mock 1 , Charles Zukoski 1
1 Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show Abstract9:00 PM - HH11.11
Effect of Conductive State on the Defect Cluster Stability in Tin-Doped Indium Oxide.
Talgat Inerbaev 1 , Ryoji Sahara 1 , Hiroshi Mizuseki 1 , Yoshiyuki Kawazoe 1 , Takashi Nakamura 2
1 , Institute for Materials Research, Sendai Japan, 2 Institute for Materials Research, Tohoku University, Sendai Japan
Show AbstractTin-doped indium oxide (ITO) is a degenerated semiconductor that is one of the most commonly used transparent conducting oxides. Its optical and electrical properties are exploited in expanding variety of transparent electrode applications, including flat-panel displays, electrochromic windows, organic light-emitting diodes, and solar cells. Although the defect structure of pure and tin-doped indium oxide is being studied over the past three decades it continues to attract the unrelenting interest of researchers. In present contribution density functional theory calculations are used to estimate the energy of interstitial oxygen release from ITO. The defect clusters of different topology and local dopant atoms arrangement around the interstitials are examined. It is found that in contrast to the current concept, the local arrangement of tin around interstitial has only minor effect on the defect clusters nonreducibility. The extraction energy of interstitial oxygen from ITO critically increases simultaneously with the charge carrier concentration. This effect is rationalized as the noticeable change of doubly charged interstitial oxygen deionization energy caused by screening of ion-ion Coulomb interaction by conductive electrons.
9:00 PM - HH11.12
Microwave-Assisted High Temperature Synthesis of Novel Nanoporous Silica Nanocoops and their Applications in Biomolecule Adsorption.
Veerappan Balasubramanian 1 , Pavuluri Srinivasu 1 , Ajayan Vinu 1
1 Nano-ionics Materials Group, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Show AbstractMesoporous materials have initiated an intensive research effort towards applications in catalysis, adsorption, separation, biomedical engineering and environmental pollution control owing to their excellent textural characteristics such as very high surface area, pore volume and tunable pore diameters. These mesoporous materials are synthesized under hydrothermal condition which is a time-consuming process. Microwave-assisted synthesis of mesoporous materials is a new area of research and offers several advantages than hydrothermal synthesis due to its rapid and uniform heating of the synthesis mixture. In the present study, we focused on synthesis of novel mesoporous materials using nonionic, cationic and anionic surfactants using “high temperature” microwave-assisted method. It has been found that the mesoporous materials with the specific surface area in the range of 350-800 m2/g and pore diameter in the range of 3-20 nm can be prepared by tuning the microwave synthesis conditions such as reaction time, reaction temperature and stirring time. It has also been found that the pore diameter of the materials is increased up to 20 nm (Silica Nanocoops) with big cages at the expense of the specific surface area. It was interested to note that the length of the unit cell increases from 16.61 to 23.76 nm with increasing microwave temperature. The textural parameters of these novel mesoporous materials can be easily tuned by synthesis condition of microwave temperature. The effect of changes in the structure and textural characteristics of the materials as a function of microwave synthesis conditions will be discussed in the presentation. Moreover, the results of the adsorption of lysozyme (Lz) onto silica nanocoops with various pore diameters will be discussed. The amount of adsorbed Lz depends on the solution pH as well as on the specific pore volume and pore diameter of the adsorbents. The maximum adsorption was observed near the isoelectric point of the Lz (pI ≈ 11), suggesting that suppression of electric repulsion between the enzymes plays an important role in the adsorption process. Moreover, the amount adsorbed depends on the pore size and pore volume of the nanoporous silica adsorbents, indicating that the Lz molecules are adsorbed inside the mesopores. It has been observed that maximum amount of lysozyme adsorption was observed for the mesoporous silica sample synthesized at higher microwave temperature.
9:00 PM - HH11.13
Scale up of Nanofibers using Multiple Jets from Plastic Filters.
Arun Kumar 1 , Ming Wei 1 , Carol Barry 1 , Julie Chen 2 , Joey Mead 1
1 Plastics Engineering, University of Massachusets, Lowell, Massachusetts, United States, 2 Mechanical Engineering, University of Massachusets, Lowell, Massachusetts, United States
Show AbstractElectrospinning is the process to produce nanoscale fibers using electric fields. Of commercial significance is the ability to electrospin at industrially relevant rates. This work investigates the effect of multiple jets compared to single jet electrospinning using polyethylene oxide. The rate of production for multiple jets compared to single jets and the effect of repulsion of the jets was studied. The production rate for multiple jets (seven) was found to be 15% more using the same flow rate and voltage as in the single needle electrospinning. When the limiting flow rate and voltages were used, the production rate was found to increase by 146 %. Fiber repulsion between jets could be controlled through proper selection of the jet dimension and materials used in the construction of the jet array.
9:00 PM - HH11.14
Shape-Controlled Synthesis of 2D Nanostructures without Surfactants.
B. Viswanath 1 , Paromita Kundu 1 , Ravishankar Narayanan 1
1 Materials Research Centre, Indian Institute of Science, Bangalore India
Show AbstractShape-controlled synthesis is vital due to the large tunability of properties that is possible with shape change of the nanostructures. In most of the synthesis, surfactants are used to control the shape. In several situations, removal of excess capping agent will be difficult and in some cases capping agent degrade the properties. Hence, it is important to have alternative methods where shape control can be achieved without surfactants. Here we report a novel synthesis method for two-dimensional nanostructures of noble metals without the use of capping agent. This method relies on tuning the chemical driving force to induce the formation of two dimensional nanostructures. Using this approach, we have developed the morphology diagram to delineate regions where 2D nanostructures form. The validity of the morphology diagram has been tested by the experiments that are carried out in aqueous medium using standard reducing agent at room temperature.
9:00 PM - HH11.15
Enhanced Luminescence of Y3Al5O12:Ce3+ Nanocrystalline Phosphor by Microwave Treatment.
Shih-Chin Lin 1 2 , Mei-Ching Chiang 1 , San-Yuan Chen 1 2 , Chia-Hsin Lin 1 , Syh-Yuh Cheng 1
1 , Industial Technology Research Institute, Hsinchu Taiwan, 2 , National Chiao Tung University, Hsinchu Taiwan
Show Abstract9:00 PM - HH11.16
Synthesis of Ultrasensitive Magnetic Resonance Contrast Agents for Cancer Imaging using PEG-Fatty Acid.
Jaemoon Yang 1 , Tong-Il Lee 2 , Jaemin Lee 1 , Eun-Kyung Lim 1 , Jin-Suck Suh 3 , Ho-Geun Yoon 4 , Yong-Min Huh 3 , Seungjoo Haam 1
1 Chemical Engeering, Yonsei Univ., Seoul Korea (the Republic of), 2 , ATGen, Advanced Technology Research Center, , Seongnam Korea (the Republic of), 3 Radiology, College of Medicine, Yonsei Univ., Seoul Korea (the Republic of), 4 Biochemistry and Molecular Biology, Center for Chronic Metabolic Disease Research, College of Medicine, Yonsei Univ., Seoul Korea (the Republic of)
Show AbstractMagnetic nanoparticles have received attention in several biomedical applications, including targeted drug delivery, cell labeling and separation, immunoassay, magnetic resonance imaging (MRI) and magnetic hyperthermia. Out of the available magnetic substances, magnetic nanocrystals synthesized by the thermal decomposition method are considered the most suitable material because of their high magnetic sensitivity and low toxicity. In addition, magnetic sensitivity of magnetic nanocrystals could be enhanced with control of magnetic spin structure. However, due to their low colloidal stability in the aqueous phase, surface modifications are required to increase physico-chemical stability. In general, magnetic nanoparticles in organic solvents are coated with inorganic/organic polymers or hydrophobic ligands that are exchanged with hydrophilic ligands for preparation of a stable aqueous magnetic solution. PEGylation is one approach used to accomplish phase transfer to the aqueous phase. In this study, we report the synthesis of novel ultrasensitive magnetic resonance contrast agents (UMRCAs) composed of magnetic nanocrystals covered with amphiphilic block copolymers. The monodispersed MnFe2O4 nanocrystals were synthesized in organic solvent. MnFe2O4 presented excellent MR signal enhancement effects because of magnetic spinel structure under magnetic field. The magnetic susceptibility of MnFe2O4 was approximately magnetic spins of 5 μB that was higher than other metal ferrites. In order to prepare stable UMRCAs using MnFe2O4 nanocrystals in the aqueous phase, amphiphilic mPEG-DA block copolymers were synthesized as stabilizers using the bioconjugation method. The morphology, size distribution and composition of successful core-shell structures were analyzed. For application as MR probes, ultrasensitivity, colloidal stability and biocompatibility of UMRCAs were evaluated. Furthermore, the ability of UMRCAs to detect cancer in vivo was investigated in animal models using MR imaging.
9:00 PM - HH11.17
Ga Doped ZnS Precursor-nanowires for ZnO/ZnGa2O4 Composite Nanotubes.
Ujjal Gautam 1 , Yoshio Bando 1 , Dmitri Golberg 1
1 Nanoscale Materials Center, National Institute for Materials Science, Tsukuba, Ibaraki, Japan
Show AbstractSemiconductor nanowires and nanotubes offer many possibilities of assembly of nanoscale devices and demonstrate enhanced properties crucial to many areas of technology. Composite nanostructures contain more than one phases in the same nanostructure harboring multiple properties and functionality. Thus these materials are important building blocks for fabrication of single component nanodevices. However, synthesis of such systems is non-trivial and the controls are system specific. In this presentation, we, first, demonstrate the Ga doping of ZnS nanowires. Ga occupies the Zn sites which are tetrahedrally coordinated by the S2- anions. Stoichiometry analysis of the sample is suggestive of Ga being in +2 oxidation state. These features are uncommon for Ga and not reported in a nanosystem, thus rendering the system unique for further studies. The nanowires have a diameter of ~100 nm and lengths of several micrometers, besides being insulated with a thin layer of carbon of controllable thickness. The procedure can be extended to dope In also. Secondly, the synthesis of these nanowires was intended to be used as precursor materials for composite nanostructures of ZnO and GaZn2O4. One of our general interests is to develop catalyst free synthetic routes to obtain composite materials and heterostructures. We demonstrate that the controlled oxidation of the nanowires yield nanotube, the walls of which are consisting of ZnO and GaZn2O4 nanograins. Thus the nanowires act as self-template for the one dimensional tubular assembly of these two important phosphors having preferential resistance towards environmental corrosions. Details of structural features, mechanism of formation, control of morphology and some interesting properties (such as field emission) of these materials shall be discussed.
9:00 PM - HH11.18
Distinguishing between Aggregates and Agglomerates of Flame-made TiO2 by High-pressure Dispersion.
Alexandra Teleki 1 , Robert Wengeler 2 , Lukas Wengeler 3 1 , Hermann Nirschl 2 , Sotiris Pratsinis 1
1 Department of Mechanical and Process Engineering, ETH Zurich, Zurich Switzerland, 2 Institute for Mechanical Process Engineering and Mechanics, Universität Karlsruhe (TH), Karlsruhe Germany, 3 , Rheinisch-Westfälische Technische Hochschule Aachen, Aachen Germany
Show AbstractThe potential of high pressure dispersion (HPD) and dynamic light scattering (DLS) is explored [1] for rapid and quantitative estimation of the extent of particle aggregation and agglomeration by analyzing the entire particle size distribution [2]. Commercially available and tailor-made TiO2 particles by flame spray pyrolysis (FSP) were characterized by X-ray diffraction, nitrogen adsorption and transmission electron microscopy (TEM). Volume distributions of these particles were obtained by DLS of their electrostatically stabilized (with Na4P2O7) aqueous suspensions. Dispersing these suspensions through a nozzle at 200 to 1400 bar reduced the size of agglomerates (particles bonded by weak physical forces) resulting in bimodal size distributions composed of their constituent primary particles and aggregates (particles bonded by strong chemical or sinter forces). Sintering FSP-made titania particles from 200 to 800 °C for four hours progressively increased the minimum primary particle size (by grain growth) and aggregate size (by neck growth and phase transformation). [1] Wengeler, R., A. Teleki, M. Vetter, S.E. Pratsinis, and H. Nirschl, “High pressure liquid dispersion and fragmentation of flame-made silica agglomerates,” Langmuir 22, 4928-4935 (2006). [2] Teleki, A., R. Wengeler, L. Wengeler, H. Nirschl, and S.E. Pratsinis, “Distinguishing between aggregates and agglomerates of flame-made TiO2 by high pressure dispersion,” Powder Technol. in press (2007).
9:00 PM - HH11.19
Preparation of Organically-Modified Nanosheets with Ti-O Network: Surface Modification of Layered Titanium Oxychloride with Various n-Alcohols.
Yoshitaka Kamochi 1 , Kaori Kikukawa 1 , Natsuki Watanabe 1 , Seiichi Tahara 1 , Yoshiyuki Sugahara 1 , Nobuhiro Kumada 2
1 Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo Japan, 2 Department of Research Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi Japan
Show AbstractOrganically-modified nanosheets with Ti-O network were prepared. Direct reaction between lithium ethoxide and titanium oxychloride (TiOCl) led to the formation of ethoxy modified TiOCl, as shown by X-ray diffraction (XRD), 13C NMR, and elemental analysis. Other n-alkoxy derivatives of TiOCl were prepared from ethoxy derivative of TiOCl via alcohol-exchange-type reactions with n-alcohols. Plate-like morphology was maintained through the reactions, as shown by scanning electron microscopic observation. For all the alcohols, new low-angle reflections appeared in XRD patterns and the reflection due to the ethoxy derivative completely disappeared. The relationship between the interlayer distance and the number of carbon atoms in n-alcohol was found to be linear. Elemental analysis demonstrated that the amounts of carbon were increased from ethoxy derivative of TiOCl after the reactions. Solid state 13C NMR spectra, furthermore, demonstrated that signals assignable to α-carbon (-C-O-) atoms appeared at around 80 ppm, indicating the formation of Ti-O-C bonds. These results clearly demonstrated that ethoxy modified TiOCl was synthesized and ethoxy groups present in the ethoxy derivative were substituted with other n-alkoxy groups.
9:00 PM - HH11.2
Surface Properties of Nanophase Ceramics that Reduce Macrophage Activity.
Peishan Liu-Snyder 1 , Dongwoo Khang 1 , Thomas Webster 1 2
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 Orthopedics, Brown University, Providence, Rhode Island, United States
Show AbstractInteractions of biomaterials with the immune system are very important for their clinical applications. Prolonged and extensive inflammatory reactions should be avoided in order to reduce the failure of implanted biomedical devices. A previous study has shown that nanophase alumina (60.6 nm and 97.7 nm grain sizes) reduces macrophage (inflammatory cells) adhesion and proliferation compared to conventional alumina (187.4 nm grain size) in both the absence and presence of an activating factor. Similar results have been seen for nanophase compared to conventional titania. In present study, we investigated macrophage responses and discerned individual surface properties of nanophase ceramics (such as surface roughness, crystallinity, and surface energy) that may be responsible for this novel finding. Our results indicated that the physical and chemical properties of nanophase ceramic surfaces impact macrophage viability and activity. These findings provide valuable information for the engineering of nanophase materials to improve orthopedic implant design.
9:00 PM - HH11.20
Inorganic Nanosheet with Low-Valence Tungsten: Preparation of a Layered Tungstic Acid HxW2O7 via Acid Treatment of Bi2W2O9 in the Presence of Reducing Reagent.
Seiichi Tahara 1 , Takakazu Minato 1 , Nobuhiro Kumada 2 , Shigenobu Hayashi 3 , Yoshiyuki Sugahara 1
1 Department of Applied Chemistry, School of Science and Engineering, Waseda University, Tokyo Japan, 2 Department of Research Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi Japan, 3 Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki Japan
Show AbstractA reduced layered tungstic acid, HxW2O7, was prepared by acid treatment of an Aurivillius phase Bi2W2O9 in the presence of Sn2+ ions. Although the color of the product formed by the acid treatment without the presence of Sn2+ ions, H2W2O7, is yellow, the blue powder was obtained after the acid treatment in the presence of Sn2+ ions. Scanning electron microscopic observation of the products showed no change in the morphology after acid treatment. X-ray diffraction pattern of the product treated with acid in presence of the Sn2+ ions was very similar to that of H2W2O7. Inductively coupled plasma emission spectrometry demonstrated essentially all the Bi3+ ions were lost upon acid treatment, indicating the occurrence of selective leaching of bismuth oxide sheets in Bi2W2O9. UV-visible absorption spectrum and XPS analysis of the product treated with acid in the presence of Sn2+ ions demonstrated that the W6+ ions were partially reduced to the W5+ ions. TG analysis showed that the amount of proton in the product was 2.4 per [W2O7]. These results suggested the successful formation of a reduced layered tungstic acid H2.4W2O7.
9:00 PM - HH11.21
Optical Property of Diamond-like Carbon Coated Nanocrystalline Silicon Particles.
Masaki Hiruoka 1 , Keisuke Sato 2 , Kenji Hirakuri 1
1 , Tokyo Denki University, Saitama Japan, 2 Quantum Beam Center, NIMS, Ibaraki Japan
Show AbstractLuminescent nanoparticles have been expected for biomedical applications as bio-imaging and drug-delivery-systems. In particular, diamond-like carbon (DLC) coated nanocrystalline silicon (nc-Si) particles have attractive features such as multi-color luminescent function, stable surface condition and biocompatibility. In this paper, we fabricated the nc-Si particles that completely coated with the DLC layer. The luminescent property of the DLC coated sample has reported.Sample was fabricated by following manufacturing processes. First, the DLC layer was deposited on the natrium chloride (NaCl) substrate using a ratio frequency (RF) plasma chemical vapor deposition (CVD) method. After that, the water soluble nc-Si particles were applied on the NaCl substrate with the DLC layer. Moreover, the surfaces on the nc-Si particles were coated with the DLC layer. The DLC/nc-Si particles/DLC layer was exfoliated from the NaCl substrate by immersion in pure water and then the nc-Si particles surrounding the DLC layer were dispersed in pure water by ultrasonic vibration process. The optical transmittance, surface composition and luminescent property of the sample were evaluated by ultraviolet (UV) spectrophotometer, Raman spectroscopy and photoluminescence (PL) analysis.The DLC layer on the surfaces of the nc-Si particles consisted of typical disorder band (1350 cm-1) and graphite band (1580cm-1). The sample exhibited the red luminescence with a peak wavelength of 800nm, because the optical transmittance of DLC layer was high value more than 80% in visible range, which is luminescence wavelength from the nc-Si particles. Moreover, the red luminescence was very stable in pure water.
9:00 PM - HH11.22
Preparation of Intelligent Drug Nanoparticles by Comminution.
Sujung Kim 1 , Jonghwi Lee 1
1 Chemical Enginerring and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractINTRODUCTIONStable drug nanoparticles can be conveniently prepared by wet comminution in the presence of polymeric stabilizers. Chitosan as a polymeric stabilizer of drug nanoparticles is a hydrophilic polymer with positive charge. The absorbed chitosan chains can be ionically cross-linked with tripolyphosphate(TPP) and encapsulate drug nanoparticles. The main advantages of encapsulated drug nanoparticles lie in their capacity to cross biological barriers and to deliver drugs of macromolecules to a target site with subsequent controlled release. This method was further developed to prepare polymeric empty carriers and surface modified drug nanocrystals. Empty carrier can be loaded with different materials.MATERIALS AND METHODSLow energy comminution was used to produce nanocrystal dispersions using grinding media. Drug was mixed with chitosan (Mw > 10 K) solution and the media beads were put into the mixture. The comminution speed and time were 125 rpm and 5 days.Naproxen suspension was dropped into TPP solution with stirring. The suspension was centrifuged at 7000 rpm for 5 min. The supernatant water was removed and the remainder was freeze dried. Empty carriers were prepared via the removal of drug nanocrystal cores by adding methanol to dried powder.Paclitaxel was used as targeted drug. For constructing targeting systems, Paclitaxel suspension dropped into TPP solution with stirring. Folic acid and 1-(3-dimethylaminopropyl-3-ethylcarbodiimide (EDC) were dissolved in buffer (pH 9). Paclitaxel suspension contained cross-linked chitosan dropped into folic acid solution. Conjugation was allowed to take place for 20 h at room temperature with stirring.RESULTSThe resulting suspension contained chitosan-absorbed drug nanoparticles. The particle size of naproxen was about 130 nm and the particle size distributions were unimodal.The empty carriers were confirmed by TEM image. The figure below shows the empty space in cross-linked chitosan formed by removing core drug particles.Conjugation of chitosan and folic acid was checked by 1H-NMR. On comparing with 1H-NMR spectra of folic acid, the spectra of chitosan-folic acid are absence of the carboxylic proton signals at δ 11.4. Spectra of chitosan-folic acid have aromatic proton signals at around δ 6.8-8.7 in comparison with the spectra of chitosan. Consequently, Chitosan and folic acid were successfully conjugated. The particle size of paclitaxel was about 330 nm and barely changed in spite of the modification of polymer.CONCLUSIONSNanocrystal suspensions were prepared by wet comminution and then the absorbed chitosan chains were cross-linked with TPP. Empty carriers were successfully prepared by removing drug nanocrystal cores within the cross-linked chitosan.
9:00 PM - HH11.25
Development of a Simple Sintering Law for Fractal Aggregates Composed of Unequal Sized Primary Particles.
Takumi Hawa 1 2 , Michael Zachariah 1 2
1 Process Measurements Division, NIST, Gaithersburg, Maryland, United States, 2 Mechanical Engineering, Chemistry and Biochemistry, University of Maryland, College Park, Maryland, United States
Show AbstractA simple modification to the Frenkel sintering law is developed for fractal aggregates composed of unequal sized nanoparticles, based on molecular dynamics (MD) simulations. The fractal aggregates investigated consist of up to 110 primary particles of silicon, with primary particles of 2.5 and 5 nm in diameter. Aggregates of Fractal dimension of 1 (wire), 1.9 (complex), and 3 (compact) were considered. Sintering of aggregates consists of three steps, a) reaction between particles to minimize surface defects, (b) sintering of multiple secondary branches to the primary branch, and (c) contraction of the primary branch. The sintering times normalized by the average primary particle diameter showed a universal relationship that depends on the number of particles in the aggregate, a volume ratio of primary particles, and its fractal dimension. This result for the sintering of arbitrary fractal aggregates can be approximated with a power law modification of the Frenkel viscous flow equation (sintering of dimmer), to include a dependence on the number of particles in a fractal aggregate, the volume ratio, and the fractal dimension.
9:00 PM - HH11.26
Organic-Inorganic Hybrid Liquid Crystals: Induction of Thermotropic Liquid-Crystallinity into Disk-Shaped Iron Oxide Magnetic Nanoparticles.
Kiyoshi Kanie 1 , Shun Hatayama 1 , Hiroshi Nakamura 2 , Atsushi Muramatsu 1
1 Institute of Multidisciplinary research for Advanced Materials, Tohoku university, Sendai Japan, 2 , TOYOTA R&D Labs. Inc., Aichi-gun Japan
Show AbstractRecent remarkable progress in synthetic inorganic fine- and nano- particles is becoming us to obtain various types of monodispersed nanoparticles with size and shape uniformities, thus, we can expected to meet new horizon of nanoparticle-based novel functional materials by the utilization of size- and shape-controlled inorganic nanoparticles as key components. As nanoparticle-based novel-type of functional materials, we have recently developed organic-inorganic hybrid liquid crystals (LCs). For example, hybridization of organic LCs with an amino group with monodispersed needle-like TiO2 nanoparticles obtained by the Gel-Sol method,1) brought the induction of thermotropic liquid-crystallinity into the TiO2 nanoparticles.2) Basis on this idea, we have also succeeded in thermotropic liquid crystallization of monodispersed a-Fe2O3 fine particles with spindle- and cubic-shapes.3) For the induction of thermotropic liquid crystallinity into inorganic nanoparticles, the aspect ratio of the inorganic particles and their uniformity in morphology are decisive factors. Furthermore, adsorption of functional groups-substituted organic LCs on the surfaces of inorganic particles also plays an essential role for the formation of thermotropic LC phases. In the present study, we focused on disk-shaped and monodispersed magnetic iron oxide nanoparticle, which was reported by Alivisatos et al,4) for the induction of thermotropic liquid crystallinity. Phase transition behavior and the self-assembled structures of hybrids of the disk-shaped nanoparticles and carboxyl group-substituted organic LCs will be discussed. 1) T. Sugimoto, “Monodispersed Particles,” Elsevier, Amsterdam, 2001.2) K. Kanie, T. Sugimoto, J. Am. Chem. Soc., 125, 10518 (2003).3) K. Kanie, A. Muramatsu, J. Am. Chem. Soc., 127, 11578 (2005).4) M. F. Casula, Y.-W. Jun, D. J. Zaziski, E. M. Chan, A. Corrias, A. P. Alivisatos, J. Am. Chem. Soc., 128, 1675-1682 (2006).
9:00 PM - HH11.27
Preparation of Iron Oxide Nanoparticles by Microwave Synthesis and Their Characterization.
Ozge Acarbas 1 , Ahmet Ozenbas 1
1 Metallurgical and Materials Engineering, Middle East Technical University, Ankara Turkey
Show Abstract9:00 PM - HH11.28
Structural and Mechanical Properties of Novel Multi-Phase Gallium Nitride Nanowires.
Benjamin Jacobs 1 , Kaylee McElroy 1 , Virginia Ayres 1 , Martin Crimp 1 , MaoQe He 2 , Joshua Halpern 2
1 , Michigan State University, East Lansing, Michigan, United States, 2 , Howard University, Washington , District of Columbia, United States
Show AbstractA novel gallium nitride (GaN) nanowire homostructure which incorporates both wurtzite and zinc-blende phases in a longitudinal configuration has been identified [1]. The nanowire structure was characterized with high-resolution transmission electron microscopy (HRTEM), and HRTEM cross sectional analysis of the multi-phase nanowire homostructure was done using focused ion beam (FIB) techniques. The nanowires used in this study were grown via a catalyst-free method, which leads to the multi-phase structure occurring by means of a self-organized process [2-3]. Variations in zinc-blende and wurtzite phase ratios were also studied and directly correspond to furnace growth temperatures, where a reduction in the zinc-blende phase ratio occurs at higher temperatures. Scanning tunneling microscopy (STM) measurements of the nanowire surface have also been conducted, which allowed for structural studies of the nanowire surface. Bandgap measurements using cathodoluminescence have shown large shifts in both the zinc-blende and wurtzite nanowire bandgaps relative to GaN bulk values indicating high levels of strain in the system. The connections between the electronic and nano-mechanical properties are under investigation using both spectroscopic and nanomanipulator techniques. The multi-phase nanowire structure indicates the unique nature of the catalyst-free growth mechanism, which is as yet not well understood. This structure has also been used in electronic devices and the multi-phase nanowire may indicate phase specific electronic transport with high current density capability leading to high power electronic applications [4].[1] B. W. Jacobs, V. M. Ayres, M. P. Petkov, J. B. Halpern, M. Q. He, A. D. Baczewski, K. McElroy, M. A. Crimp, J. Zhang, H. C. Shaw, Nano Lett. 7, 1435-1438 (2007).[2] M. He, P. Zhou, S.N. Mohammad, G.L. Harris, J.B. Halpern, R. Jacobs, W.L. Sarney and L.J. Salamanca-Riba, J. of Crys. Grow. 231, 357-365 (2001).[3] A. M. S. ElAhl, M. He, P. Zhou, G. L. Harris, L. Salamanca-Riba, F. Felt, H. C. Shaw, A. Sharma, M. Jah, D. Lakins, T. Steiner, and S. N. Mohammad, J. of Appl. Phys. 94, 7749-7756 (2003).[4] B.W. Jacobs, V.M. Ayres, M.A. Tupta, R.E. Stallcup, A. Hartman, J.B. Halpern, M-Q. He, M.A. Crimp, A.D. Baczewski, N.V. Tram, Q. Chen, Y. Fan, S. Kumar, L. Udpa , 2006 6th IEEE Conference on Nanotechnology Proceedings, ISBN 1-4244-0078-3.The NASA Graduate Student Research Program, and the National Science Foundation PREMS and IREE Programs are gratefully acknowledged.
9:00 PM - HH11.29
Synthesis and Sintering of TiN/Si3N4 Nanocomposite Powders at Cryogenic Solution.
Mei Yang 1 , Mingli Lv 1 , Hongmin Zhu 1
1 , University of Science and Technology Beijing, Beijing China
Show AbstractA new method of TiN/Si3N4 nanocomposite powders through reduction at super low temperatures was proposed and tested. The reduction of TiCl4 and SiCl4 by Na was conducted in liquid ammonia at the the temperature range of 223K-233K, and TiN and Si3N4 nanopowders were obtained. Based on this reaction, in-situ coating and co-precipitation was conducted. The TiN nano-particles deposited on the surface of Si3N4 particles as the nuclei in the in-situ coating and in the co-precipitation two or more source of ions were reduced uniformly in the liquid ammonia. TiN/Si3N4 nanocomposite powders were prepared by the both routes and were characterized with X-ray diffraction(XRD), transmission electron microscopy(TEM). The effects of in-situ and the particle size on the morphology of the composite were discussed. Sintered by Spark Plasma Sintering(SPS), dense TiN/Si3N4 nanoceramic with the average gain size of 200nm was obtained.
9:00 PM - HH11.3
Rod-shaped Assemblies of Biphasic Nanostructures Through Dynamic Templating.
Qingyu Yan 1 , Makala Raghuveer 1 , Huafang Li 1 , Binay Singh 1 , Taeyun Kim 1 , Mutsuhiro Shima 1 , Arijit Bose 2 , Ganapathiraman Ramanath 1
1 Matierials Science, Rensselaer Polytechnic Institute, Troy, New York, United States, 2 Chemical Engineering Department, University of Rhode Island, Kingston, Rhode Island, United States
Show AbstractThe synthesis of inorganic nanocrystals with control over shape and size is necessary for both fundamental studies of electrical, optical and magnetic properties, as well as many emerging applications. Many strategies are available to synthesize and assemble one-dimensional nanocrystals, e.g. via vapor-liquid-solid, physical, chemical, and biological templating routes. Crystal shape control usually is driven by selective adsorption of surfactants onto specific crystallographic facets. Here, we report a completely new approach for forming rod-shaped biphasic assemblies of FePt and PtTe2 nanostructures through dynamic interactions between the inorganic phases during surfactant-mediated nucleation, growth and stacking. Although neither FePt nor PtTe2 when synthesized separately form one-dimensional structures by polyol reduction of the metal salts and orthotelluric acid, co-precipitation of both phases produces 100-400 nm-long 40-60 nm-wide rod-shaped assemblies. Based upon transmission electron microscopy, X-ray photoelectron spectroscopy and infrared spectroscopy measurements, we show that sucrose and trioctylphosphine oxide direct the formation and stacking of 20-30 nm-long 3-nm-wide PtTe2 platelets, providing the framework for the rod-shaped assemblies in which FePt nanoparticles nucleate and grow between the platelets. The magnetic properties and thermal stability of the assemblies will be briefly described. Our synthesis strategy offers an attractive alternative to direct the assembly of nanoscopic heterostructures of controllable shape, especially in cases where shape control in the constituent inorganic phases is difficult. In order to illustrate the versatility of our approach, we will demonstrate the synthesis of assemblies of biphasic nanostructures of PtTe2 and PbTe, which could be useful for thermoelectrics applications.
9:00 PM - HH11.30
A General Strategy for Synthesizing FePt Nanowires and Nanorods.
Chao Wang 1 2 , Yanglong Hou 2 , Jaemin Kim 2 , Shouheng Sun 2
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 Chemistry, Brown University, Providence, Rhode Island, United States
Show AbstractSynthesis of FePt nanoparticles with controlled shape and magnetic alignment has become an important goal in developing nanocrystal arrays for applications in information storage, permanent-magnet nanocomposites, and catalysis. Previous work on the synthesis and self-assembly of FePt nanocubes suggests that elongated nanocrystals may be used to achieve texture and magnetic alignment. This controlled alignment of FePt nanoparticles is essential for the fabrication of single-particle recording media with ultrahigh density, magnetic nanocomposites with maximum energy product, and magnetotransport devices with optimum magnetoresistivity. Herein we report a general strategy for synthesizing FePt nanowires (NWs) and nanorods (NRs) by simultaneous reduction of platinum acetylacetonate, Pt(acac)2, and thermal decomposition of iron carbonyl, Fe(CO)5, in a mixture of oleylamine (OAm) and octadecene (ODE). The length can be controlled from 20 nm to several micrometers by tuning the ratio of OAM to ODE, while the diameter was kept around 3 nm. Owing to the structure confinement in the elongated shapes, these NWs and NRs show partial structural and magnetic alignment in hard magnetic phase (fct) obtained by thermally annealing the nanorod or nwnowire self-assemblies. This study indicates that well-controlled NWs or NRs are likely the future choice for controlling texture and magnetic alignment in self-assembled nanomagnet arrays to support high-density magnetic information and as building blocks for fabricating highly sensitive magnetotransport devices.
9:00 PM - HH11.31
Polystyrene Nanocomposites from Thermally Stable Phosphonium Modified Montmorillonites.
Sijia Zhao 1 , Mayu Si 1 , Miriam Rafailovich 1
1 Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York, United States
Show AbstractThe thermal degradation of alkyl quaternary ammonium-modified montmorillonites limits the synthesis and processing of polymer layered silicate nanocomposite (PLSN). Our efforts to address the issue focus on developing improved organophillic treatment rendering thermally stable montmorillonite (MMT). Phosphonium-containing salts were successfully employed to modify sodium montmorillonite by the standard ion exchange reaction. The use of phosphonium salts as surfactant gives the corresponding treated MMT a 50-60°C improvement in thermal stability in nitrogen atmosphere as compared to the commercial Cloisite® 20A. To examine the miscibility of the new clay with polymers, polystyrene (PS)-clay nanocomposites were then melt-blended and characterized by transmission electron microscopy, small-angle X-ray scattering, thermal gravimetric analysis and dynamic mechanical analyzer. The phosphonium-treated MMT were observed to be finely dispersed in the PS matrix to form a predominantly intercalated/exfoliated morphology.
9:00 PM - HH11.32
Synthesis and Characterization of Spectroscopically Encoded Nanocomposites.
Baker Jawabrah Al-Hourani 1 2 , Sheng Dai 1 , Ramon Alvarez-Puebla 1 , Juan Bravo-Vasquez 1 , Hicham Fenniri 1 2
1 , National Institute for Nanotechnology, National Research Council, Edmonton , Alberta, Canada, 2 Gunning/Lemieux Chemistry Center, Uinversity of Alberta, Edmonton, Alberta, Canada
Show AbstractNano-structured gold could conjugate with thio containing organic compounds, which gives rise to the enhanced vibrational spectrum known as surface enhanced Raman scattering (SERS). Three thio-containing styrene monomers with different leaving groups, S-4-vinylphenyl ethanethioate, 1,2-bis(4-vinylphenyl)disulfane, butyl(4-vinylphenyl)sulfane, were synthesized through nucleophilic substitution/addition reactions and purified through column chromatography. In aqueous solution, these monomers could bind to the surface of gold nanoparticles and give enhancement factors of more than 105. The formation of self-assembled monolayer was characterized by Raman, SERS, SEM, XRD, etc. It was evident of the difference between the Raman spectra of bulk monomers and their SERS on gold surface. The enhanced factors and the formation of SAM were dependent on monomer structure and fabrication method. To form a stable nanostructure, surface polymerization could be initiated on the self-assemble monolayer. Such system would have potential application as the template for micro-analysis in biological science.
9:00 PM - HH11.33
Synthesis and Characterization of POSS-PDMS Nanocomposites.
Ticora Jones 1 , Theodore Baumann 1 , Thomas Wilson 1 , Andrew Saab 1 , Robert Maxwell 1
1 , Lawrence Livermore National Lab, Livermore, California, United States
Show AbstractA series of nanocomposite materials based on Polyhedral Oligomeric Silsesquioxane (POSS) and Polydimethyl Siloxane (PDMS) has been synthesized via a hydrosilation reaction. This series includes composites based on two global architectures: systems that utilize multifunctional POSS to create a highly crosslinked network, and systems that incorporate the POSS as a crosslinker/pendant moiety. The incorporation of a variety of nanoparticles into inorganic/organic blends of polymers has relevance as the next generation of nanocomposite materials evolves. Improvement of the mechanical properties of PDMS systems has been shown when the nanofiller (POSS) is chemically rather than physically incorporated. Controlling the method (crosslink/pendant or simple crosslink) and level of POSS incorporation and relating these tuneable characteristics to structure- property relationships in nanocomposites is critical. The difference between these two incorporation strategies and the impact on the resulting properties will be explored using mechanical and thermal analysis. To date, comparisons of nanofiller incorporation with crosslinking and/or pendant moieties as property enhancing materials has not included elastomer based systems. The addition of these POSS-PDMS based nanocomposites will provide further insight into the impact of nanofillers on elastomeric systems as well as provide a roadmap for increased decomposition and glass transition temperatures, and improved mechanical strength.This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract W-7405-Eng-48. It was funded by a Laboratory Directed Research and Development grant (06-SI-005). UCRL-ABS-231684.
9:00 PM - HH11.34
Forming Polymer Nanocomposites with a New Class of Environmentally Compatible, Thermally Stable, Functionalized Clays.
Seongchan Park 1 , Takashi Kashiwagi 2 , Tadanori Koga 1 , Jonathan Sokolov 1 , Miriam Rafailovich 1
1 Materials Science and Engineering, Stony Brook University, Stony Brook, New York, United States, 2 Fire Research Division, NIST, Stony Brook, Maryland, United States
Show AbstractFunctionalization of sodium clays is essential to achieve the degree of exfoliation necessary for producing nanocomposites. On the other hand, production of large quantities has also raised many concerns regarding the toxicity of the process. Here we describe an easy, but effective method to functionalize the clays without the use of di-tallow molecules. We show that clays functiolized with our method can be exfoliated and intercalated using shear in different polymers and polymer blends using standard melt blending techniques. Our technique involves the adsorption of RDP, a phosphorus-based flame retardant agent, on the surface of the natural clay. Blends were made with the clays and ethylene vinyl acetate (EVA) and high impact polystyrene (HIPS). In order to clarify localization of the intercalated and exfoliated clays, TEM images were obtained which indicated that the clays were intercalated and partially exfoliated. Blends were also made with PC and poly( styrene-acrylonitrile of 24 % (SAN24) and the samples were studied with SAXS. We found that d001=2.23nm in the pure clays was shift to d001= 3.83nm in PC/SAN24 blend. The system is a typical immiscible blend, with two different glass transition temperatures, 127°C and 167°C. Using DMA addition of only 5% clay results in a single value of for Tg=120°C for the blend. These results are similar to those obtained with di-tallow clays. But in contrast to di-tallow clays, TGA analysis confirmed that the RDP coating has much higher thermal stability. Hence SAXS data showed that the intercalation was retained even if the melt was heated up to 450°C. Cone calorimetry indicated that the RDP functionalized clays were also more effective than di-tallow clays at reducing the heat release and mass loss rates of the blends
9:00 PM - HH11.35
Effect of Functionalization on the Crystallization and Mechanical Properties of MWNT-PBT Nanocomposites.
Gaurav Mago 1 , Carlos Velasco-Santos 3 , Ana Martinez-Hernandez 3 , Frank Fisher 1 , Dilhan Kalyon 2
1 Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, United States, 3 Centro de Fisica Aplicada y Tecnología Avanzada, Universidad Nacional Autonoma de Mexico, Queretaro Mexico, 2 Department of Chemical, Biomedical and Materials Engineering, Stevens Institute of Technology, Hoboken, New Jersey, United States
Show AbstractA number of researchers are interested in using low loadings of multiwalled carbon nanotubes (MWNTs) to enhance the mechanical properties of polymers. For effective reinforcement proper dispersion is a requirement, which results in more uniform stress distribution and minimizes the presence of stress-concentrators. In many cases, nanotube functionalization has been shown to increase the effectiveness of the nanotube reinforcement, often attributed to better dispersion of the nanotubes within the polymer. However, at the moment it is not clear how this nanotube functionalization changes the crystallization kinetics and polymer morphology for semi-crystalline polymer nanocomposites. In our interest to understand the effect of MWNT functionalization on PBT crystallization kinetics, morphology and mechanical properties, nanocomposites were fabricated with both as-received and functionalized MWNTs. Initial results show that the addition of unfunctionalized nanotubes greatly alters the crystallization temperature and crystal size for quiescent samples in comparison to that of the pure polymer. In addition, isothermal crystallization studies using an Advanced Rheometric Expansion System (ARES) unit show an increase in rate of crystallization under shear for the unfunctionalized MWNT nanocomposite samples as compared to pure polymer. The rate of crystallization was found to increase with increase in MWNT loadings, increase in shear rate and decrease in temperature. Further, tensile testing of quiescent nanocomposite samples (prepared from unfunctionalized MWNTs) shows a decrease in toughness and yield stress with an increase in MWNT loading. The overall goal of this work is to study how MWNT functionalization changes the polymer morphology and crystallization kinetics for semi-crystalline polymer nanocomposites, and how these changes relate to changes in rheological and mechanical properties of the nanocomposite system.
9:00 PM - HH11.36
Nano-dispersed Particulate Ceramics in Poly-Lactide-Co-Glycolide Composites Improve Implantable Bone Substitute Properties.
Huinan Liu 1 , Thomas Webster 1
1 Division of Engineering, Brown University, Providence, Rhode Island, United States
Show AbstractBecause natural bone is under continuous physiological stresses (such as compression, tension, torsion, and/or bending), the mechanical properties of orthopedic implant materials should closely match those of living bone. This is necessary to minimize stress and strain imbalances during physiological loading conditions which will lead to implant failure. Current materials used in orthopedic implant applications do not match the mechanical properties of bone. Previous studies demonstrated that dispersed nano-particulate titania in poly-lactide-co-glycolide (PLGA) scaffolds promote osteoblast (bone-forming cell) adhesion and long-term functions (such as collagen synthesis and calcium-containing mineral deposition) compared to pure PLGA scaffolds and more agglomerated titania in PLGA scaffolds. The controlled dispersion of titania nanoparticles in PLGA also furthered decreased the weight loss of scaffolds, reduced harmful acidic pH changes during PLGA degradation, and prolonged the mechanical integrity of the scaffolds. The objective of the present study was to characterize the mechanical properties of PLGA with well-dispersed nanophase ceramics, including titania and hydroxyapatite (HA). The dispersion of ceramics in PLGA was controlled by sonication and was characterized by field emission scanning electron microscopy and image analysis. For this purpose, two major stresses (compression and tension) that natural bone experiences under physiological loading conditions were characterized using an Instron Material Testing System. The results showed that nano-dispersed ceramic (titania or HA, respectively) particles in PLGA increased the compressive and tensile modulus of such scaffolds compared to pure PLGA scaffolds and the more agglomerated ceramics in PLGA scaffolds. The mechanisms behind these results were also speculated. Since the predominant feature of nano-particles lies in their ultra-fine dimension, a large fraction of filler atoms can reside at the PLGA-ceramic interface which can lead to a stronger interfacial interaction, but only if the nano-particles are well dispersed at the nanometer level in the surrounding polymer matrix. As the interfacial PLGA-ceramic structure plays a critical role in determining the mechanical properties of composites, nano-composites with a great number of smaller interfaces could be expected to provide unusual properties, and the shortcomings induced by the heterogeneity of conventional (or micron) particle filled composites would also be avoided. Therefore, coupled with prior studies demonstrating greater osteoblast functions, the combination of PLGA with a strong and biocompatible well-dispersed nano ceramic (titania or HA) phase may provide better candidate materials for orthopedic applications.
9:00 PM - HH11.37
Preparation of Cellulose/inorganic Materials CompositeSpherical Microbeads for Polishing Materials and their Evaluation.
Seitaro Kobayashi 1 , Shoji Nagaoka 2 , Kazunari Hirakawa 3 , Kazuhiro Tonda 1 , Masanori Nagata 2 , Makoto Takafuji 1 , Hirotaka Ihara 1
1 Faculty of Engineering, Department of Applied Chemistry and Biochemistry, Kumamoto, Kumamoto, Japan, 2 Materials Development Department, Kumamoto Industrial Research Institute, Kumamoto, Kumamoto, Japan, 3 , Nishinihon Nagase Co. Ltd., Fukuoka, Fukuoka, Japan
Show AbstractWe prepared various types of cellulose/inorganic materials hybrid spherical microbeads, which were hybridized with SiC, Al2O3, CeO2, and diamond particles by a one-step phase separation method using a cellulose xanthate aqueous solution (viscose) and a sodium polyacrylate aqueous solution (PAA), respectively, as polishing materials to polish quartz glass and silicon wafer. It was found out that the differences relative to dispersibility of inorganic material particles in viscose occurred in the distribution of particles containing in microsphere. Therefore, the relationships between the mechanism of hybrid-sphering and properties of inorganic materials particles used were discussed. Cellulose microbeads (Cell/SiC), which were hybridized with SiC particles, supported SiC particles on their surfaces. In addition, cellulose microbeads (Cell/CeO2) hybridized with CeO2 particles, also supported CeO2 particles on the surface, namely “Shell-form”. In the case of hybridization of diamond particles were not only distributed on the surface, but also dropped out of composite spherical beads (Cell/Dia). These phenomena were considered to depend on dispersibility of particles in viscose. The SiC, CeO2, and diamond particles possessed minus zeta electric potential, respectively. We previously reported that cellulose/TiO2 composite spherical microbeads could be prepared by above-mentioned one-step phase separation method. The narrower the surface minus electric potential distribution of TiO2 nano-particles is, the more the TiO2 nano-particles appear on the surface (Shell-form). The potential distribution of SiC or CeO2 particles used was similar to that of TiO2 particles used for the preparation of cellulose/TiO2 Core/Shell composite spherical microbeads. These indicated that these particles dispersed in the sphering pH condition, i.e., in pH 13. Since above-mentioned inorganic materials particles used for sphering have the uniform minus electric potential, they were driven out by CSS- group of cellulose xanthate and COO- group of polyacrylic acid. Therefore, SiC or CeO2 particles localized at the interface between viscose phase and PAA aqueous solution phase. In addition, diamond particles were driven by CSS- group more outside cellulose xanthate phase, because of shifted to too minus potential. The polishing property for quartz glass disk was also influenced on the surface properties.On the other hand, the zeta electric potential distribution of Al2O3 was the broadest of those of all given inorganic materials. The surface electric potential of Al2O3 was inhomogeneous and occurred the diffusion into plus electric potential. As reported previously, the kind of TiO2 particles that had broad electric potential distribution were involved in the microbead internally, namely “Core-form”. As expected, Al2O3 particles used were located within the viscose phase. The Cellulose/Al2O3 composite spherical microbead was core-form composite spherical microbead.
9:00 PM - HH11.38
Crystallisation and Dielectric Properties of Poly(lactic acid)/montmorillonite Composites.
Kalliopi Vartzeli-Nikaki 1 , Vassilis Fotopoulos 1 , Stavros Christopoulos 1 , Anna Spanoudaki 1 , Polycarpos Pissis 1 , Ioannis Zuburtikudis 2 , S. Marras 3 , C. Panayiotou 3
1 Department of Applied Mathematics and Physics, National Technical University of Athens, Zografou Greece, 2 Department of Industrial Design Engineering, TEI of Western Macedonia, Kozani Greece, 3 Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki Greece
Show AbstractWe present calorimetric and dielectric studies of polymer nanocomposites with poly(lactic acid) (PLA) as a matrix and montmorillonite (MMT) inclusions modified with decaexylamine (C16A). The nanocomposites were prepared through solution casting using chloroform as a solvent. The concentration of the inclusions varied from 0 to 15%. The degree of intercalation has been examined using X-Ray spectroscopy and the samples have been thermally and mechanically characterised using Differential Scanning Calorimetry, Thermogravimetric Analysis and Dynamic Mechanical Analysis. The results have shown that the hybrid materials have an increased thermal stability and improved mechanical properties. In order to study the polymer dynamics more thoroughly we conducted Dielectric Relaxation Spectroscopy (DRS) in a broad temperature and frequency range (123–393 K, 10-1– 106 Hz), as well as Thermally Stimulated Depolarisation Currents (TSDC) measurements. Differential Scanning Calorimetry and Isothermal Crystallisation techniques were employed, in order to investigate the influence of the presence of montmorillonite nanoparticles on the crystallisation rate of PLA and on the quality of the produced crystallites.
9:00 PM - HH11.39
Dielectric and Thermomechanical Properties of Polypropylene/Multi-Walled Carbon Nanotubes Nanocomposites.
Athanasios Kanapitsas 1 , Emmanuel Logakis 2 , Christos Pandis 2 , Ioannis Zuburtikudis 3 , Polycarpos Pissis 2 , Constantinos Delides 4
1 Electronics, Technological Educational Institute of Lamia, Lamia Greece, 2 Physics, National Technical University of Athens, Athens Greece, 3 Industrial Design Engineering, Technological Educational Institute of West Macedonia, Kozani Greece, 4 Laboratories of Physics and Materials Technology, Technological Educational Institute of West Macedonia, Kozani Greece
Show AbstractCarbon nanotubes (CNTs) have attracted special interest as new materials for mixing with polymers due to their exceptional electrical, mechanical and thermal properties. Polymer/CNTs nanocomposites are promising materials with potential applications as electromagnetic shielding coatings, electrostatically dissipative materials, aerospace structural materials and active elements in sensors.In the present study, the nanocomposites were prepared by melt mixing a starting masterbatch (Hyperion Catalysis, USA) of polypropylene (PP) containing 20 wt% multi-walled carbon nanotubes (MWCNTs) with an isotactic PP (Melt index 35.0 g/10 min) in a Plasti-corder kneading machine, followed by compression moulding using a laboratory hydraulic press in order to obtain different concentrations in CNTs.The purpose of this work is to examine the thermal, mechanical and electrical properties of multi-walled carbon nanotubes (MWCNT) filled PP nanocomposites formed by melt-mixing. To that aim differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and dielectric relaxation spectroscopy (DRS) were employed. The influence of CNT on the thermal transitions (glass transition temperature, melting, crystallization) of the pure polymers is investigated. The results are discussed in terms of nucleating action of CNT and interfacial polymer-filler interactions. Special attention is paid to percolation aspects by both ac and dc conductivity measurements for the samples which are above the percolation threshold. Percolation threshold is the critical concentration of the filler where conducting pathways are formed by CNT and consequently a transition from the insulating to the conducting phase is observed. pc is usually determined through dc conductivity measurements. In this work ac measurements were performed, as apart from the determination of dc conductivity, the opportunity to study in detail the frequency dependence of conductivity is provided by defining the critical frequency, where the transition from dc to ac conductivity is observed. Furthermore, the actual aspect ratio (length-to-diameter ratio) of the inclusions in the nanocomposites is calculated using two different theoretical models (E.J. Garboczi et al. and I. Balberg et al. model) and the exported values are correlated with the percolation threshold values. It is already known that CNT have the tendency to form bundles due to van der Waals interactions and the final aspect ratio of CNT in the nanocomposites is much lower, comparing with the value of an individual nanotube. This fact leads to increased percolation threshold values. Besides, the conductivity mechanism is examined through the temperature dependence of conductivity.Acknowledgement: This work is financed by the project PENED 2003. The project is cofinanced 75% of public expenditure through EC- European Social Fund, 25% of public expenditure through Ministry of Development,GSRT and through private sector.
9:00 PM - HH11.4
Optical Enhancing Properties of Ag/Au Bimetallic Nanoshells Immobilized on Electronic Silicon Surfaces.
Ramon Alvarez-Puebla 1 , Juan Bravo-Vasquez 1 , Pavel Cheben 3 , Dan-Xia Xu 3 , Philip Waldron 3 , Hicham Fenniri 1 2
1 , National Institute for Nanotechnology, Edmonton, Alberta, Canada, 3 , Institute for Microstructural Sciences, Ottawa, Ontario, Canada, 2 Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
Show Abstract9:00 PM - HH11.40
Electrosynthesis and Properties of Calcium Phosphate- silver Nanowires Composite.
Stanislau Khomich 1 , Vladimir Novikov 2 , Nadezda Ischenko 2
1 , Belarus State Medical University, Minsk Belarus, 2 , Joined Institute of Solid State and Semiconductor Physics, National Academy of Sciences of Belarus, Minsk Belarus
Show Abstract9:00 PM - HH11.41
Co3O4 Nanocubes Embedded in Silica Matrix.
Ulrike Grossner 1 , Heidi Nielsen 1 , Poul Norby 1 2
1 Centre for Materials Science and Nanotechnology (SMN), University of Oslo, Oslo Norway, 2 Department of Chemistry, University of Oslo, Oslo Norway
Show AbstractCobalt spinel, Co3O4, is an promising functional material for a wide range of technological applications such as sensors, energy storage, spintronics and medical applications. Apart from bulk and thin film samples, Co3O4 can also be grown as nanoparticles. However, for some advanced applications, embedding of well dispersed nanoparticles in a matrix is required. Single-crystalline Co3O4 nanocubes were synthesized following the procedure by R. Xu, where Co(II) in an aqueous solution is partially oxidized by air under reflux conditions in the presence of a surfactant (polyoxyethylene(20) sorbitan trioleate, TWEEN-85). By controlling nucleation and growth nanocubes with a narrow size distribution may be produced. In order to encapsulate the nanocrystals in a matrix (in an ordered and disordered fashion), a dispersion of Co3O4 nanocubes in water have been mixed with tetraethylorthosilicate (TEOS) and sodium hydroxide. By hydrolysis a 3D silica lattice is formed with Co3O4 inclusions. For 2D growth, acid catalyzed hydrolysis was used, followed by deposition by spin coating. The obtained precipitates and layers were characterized by X-ray diffraction. After calcination in air at 500°C a color change to blue was observed, indicating a chemical reaction between the cobalt spinel nanocubes and silica, resulting in tetrahedrally coordinated divalent cobalt. The conditions for obtaining ordered structures are being discussed.
9:00 PM - HH11.42
Photo-change in Pore Size of Mesoporous Silica Materials with the Isomerization of Planted Azobenzene.
Keiji Arai 1 , Hiromi Ogino 1 , Toshihiro Tanaka 1 , Masakazu Iwamoto 1
1 Chemical Resources Laboratory, Tokyo Institute of Technology, Yokohama Japan
Show Abstract Mesoporous silica materials such as MCM-41 (M41) have regular arrays of uniform mesopores. The pore diameters are fixed but their reversible change would be very interesting from the viewpoint of advanced materials. The planting of azobenzene (Az) on the pore wall and its photo-change with UV or visible light irradiation is expected to result in the realization of photocontrollable nano-pores because of the well-known reversible trans-cis isomerization (Figure 1). In fact the idea was already suggested by a few researchers [1, 2], but the change in the pore size with the isomerization has not been confirmed yet. This study was therefore devoted to verify the change. Az-planted MCM-41 (Az-M41) was prepared by silylation of M41 pores with triethoxy[4-(phenylazo)phenyl]silane. The trans to cis isomerization efficiency of Az groups on M41 was greatly dependent on the surface density of Az groups planted. It was approximately constant (40-60%) below ca. 0.9 group/nm2 and steeply decreased at or above the value. The findings mean that too much loading of Az groups onto the pore wall induced the congestion of the groups and the lowering of the isomerization efficiency. The loading amounts of Az groups on M41 was roughly adjusted at 0.9 group/nm2 in the present work. We first attempted to directly observe the photo-change in the pore diameter by N2 adsorption/desorption at 77 K. Unfortunately, no change in the pore distribution was observed, which is probably due to the adsorption of nitrogen molecules between Az groups. It indicates that we need to employ larger molecules to determine the change. Next we try to measure the change in the fluorescence spectra of p-N,N-dimethylaminobenzilydenemalononitrile (DMABMN) loaded in the pores since the intensity is reported to depend on the degree of the molecule's free rotation but we could observe only small change. During this study we found that the UV-Vis absorption spectrum of DMABMN was blue-shifted with increasing the pore diameter. We thus prepared several organic group-modified M41 by using R-Si(OEt)3 (R = Ph or Me). The wavelengths of absorption band of DMABMN incorporated into R-M41's were blue-shifted with increasing the pore diameter as shown in Figure 2. The absolute wavelengths of DMABMN were dependent on the surface organic groups, while the slopes between the pore diameters and the wavelengths are almost the same. It is clear that we can use this correlation to determine the degree of diameter change in the Az-M41 pores with the UV irradiation. The shift of the absorption bands resulting from the UV irradiation was depicted in the figure and concluded the increment in the pore size of approximately 1.0 nm of Az-M41. The reversible change in the pore diameters were also confirmed. References : [1] N. Liu et al., Nano Lett., 4, 551 (2004). [2] K. Maeda et al., Chem. Lett., 35, 736 (2006).
9:00 PM - HH11.43
``Ship-in-a-bottle" Synthesis of Porphyrin J-Aggregates in Mesoporous Silica.
Giorgio Macchi 1 2 , Francesco Meinardi 1 2 , Riccardo Tubino 1 2 , Patrizia Valsesia 1 3
1 Scienza dei Materiali, Università di Milano Bicocca, Milano Italy, 2 , INFM, Milano Italy, 3 , INSTM, Milano Italy
Show AbstractSelf-assembling processes of molecular components into supramolecular structures are primarily investigated because of their involvement in many fundamental physico-chemical as well as biological processes: the possibility of changing the mesoscopic structure of the resulting species through a proper choice of the molecular components opens the way to the design and synthesis of materials capable to exhibit specific properties and functions. Within this line of thoughts, porphyrins are well suited building blocks because they can spontaneously self-assemble in aqueous solution into dimers or higher aggregates through non-covalent interactions: the structure and spectroscopy of such molecular aggregates are of much interest because of the special properties and possible technological applications of the mesoscopic materials which are intermediate between molecules and solids.In recent years, the synthesis of ordered mesoporous inorganic-based materials, especially MCM-41, by employing supramolecular assembly of surfactant to template the reaction of inorganic species has been the subject of considerable research, due to their large surface area (1000m2/g) and storage capacity for applications in catalysis, gas and vapours adsorption, and molecular confinement.The inclusion of molecular building-blocks within a porous inorganic host, such as MCM-41, is a well-known method to protect these species from environmental moisture and chemical impurities (solvents, oxygen). Nevertheless, the insertion of aggregates with dimensions comparable to pore diameter is usually a challenging task. In the present work, we describe the successful preparation of a novel nanophase material following a so-called “ship-in-a-bottle” synthesis. The aggregation of sulphonatophenyl-porphyrin (TPPS) (which is known to be enhanced by the presence of a surfactant agent in acidic medium) has been carried out in the reaction mixture at the beginning of silica synthesis. In this way, TPPS aggregates, surrounded by surfactant molecules, template the growth of the porous host. Bright-field images of the resulting material have shown that silica particles retain the expected morphological structure. The photophysical investigation of the obtained powder has shown the typical emission of TPPS J-aggregates at 714 nm, giving us a strong evidence that both surfactant micelles and the porous oxide matrix play an effective role in the protection of the included molecular species by preserving their spectral features in a non-conventional chemical environment (dry medium, neutral pH). These results appear to be very promising for the inclusion of functional molecular and supramolecular units in inorganic host matrices as active materials in various applications, such as optoelectronic devices and luminescent probes.
9:00 PM - HH11.45
Polymer Composite Stress/strain Gauge Based on Carbon Nanofiber Paper Sheet.
Li Sun 1 , Hao Xing 1 , Gangbing Song 1
1 Mechanical Engineering, University of Houston, Houston, Texas, United States
Show Abstract9:00 PM - HH11.46
Mechanical Properties of PDMS/CNTs Nanocomposites.
Chung-Lin Wu 1 , Hsueh-Chu Lin 1 , Chien-Hsin Huang 1 , Ming-Chuen Yip 1 , Weileun Fang 1
1 Dept. of Power Mechanical Engineering, National Tsing Hua University, Hsinchu Taiwan
Show AbstractThe aim of this article is to study the mechanical properties of PDMS/CNTs nanocomposites such as Young’s modulus, yield strength, fracture strength and creep behavior. The elastic modulus, fracture, and yield strength were determined from the tensile test. In addition, the main matrix of PDMS is polymeric, and the creep behavior is a significant issue for the PDMS/CNTs composites. Thus, the creep behavior of PDMS before and after adding the CNTs will be investigated in this study. The test specimens of nanocomposites were manufactured using the thermoforming method. The mixtures of PDMS and CNTs were stirred by the ultra sonic instrument for preventing the polymerization. A feeler gap was used to define the thickness of the specimens. Therefore, the thickness can be controlled within the range of ~100 um. Microscope optical system was used to measure the dimensions of the specimens with a resolution of 0.1um. The micro tester (Instron Corp.) was used to perform the tensile and creep tests. Three different kinds of specimens were investigated, including pure PDMS, 1.0 wt%, and 2.0 wt% CNTs polymeric composites. The fracture strength of pure PDMS, 1.0 wt% and 2.0 wt% CNTs were 0.89 MPa, 1.46 MPa and 1.54 MPa, respectively. And, the yield strength of pure PDMS, 1.0 wt% and 2.0 wt% CNTs can be obtained to define a 0.2% strain off set. The yield and fracture strength of PDMS/CNTs nanocomposites will increase with raising the content of CNTs. The Young’s modulus of pure PDMS is about 0.64MPa, and the elastic modulus of PDMS with 1.0 wt% and 2.0 wt% CNTs were 1.11 MPa and 3.04 MPa respectively. The creep behavior of nanocomposites for three different kinds of specimens has been described in this research. In addition, the electrical resistances of the PDMS/CNTs nanocomposites were also investigated by a four point probe. Moreover, the microstructures composed of the mixtures of PDMS/CNTs will be presented in this study.Key words : PDMS/CNTs (polydimethylsiloxane and carbon nanotubes), Creep
9:00 PM - HH11.47
Chemically and Photochemically Reactive Siloxane Layers for Modification of Inorganic Surfaces.
Alexandra Lex 1 , Peter Pacher 2 , Susanne Temmel 1 , Quan Shen 3 , Gregor Hlawacek 3 , Oliver Werzer 2 , Anna Track 2 4 , Paul Frank 2 , Veronika Proschek 2 , Robert Schennach 2 , Georg Koller 4 , Michael Ramsey 4 , Christian Teichert 3 , Roland Resel 2 , Adolf Winkler 2 , Egbert Zojer 2 , Wolfgang Kern 1 , Gregor Trimmel 1
1 , Institute for Chemistry and Technology of Organic Materials, Graz Austria, 2 , Institute of Solid State Physics, Graz Austria, 3 , Institute of Physics, Leoben Austria, 4 , Institute of Physics, Graz Austria
Show AbstractIn this contribution, we report on the chemical modification of surfaces of inorganic insulators and semiconductors. Silicon oxide and pure silicon surfaces are modified with reactive organo siloxane layers that are capable of undergoing chemical and photochemical reactions. For this purpose, thin layers containing both sulfonyl chloride and sulfonic acid groups are deposited onto silicon wafers with thermally grown silicon oxide. By grazing incidence X-ray reflection the thickness of the layers is determined to be 2 nm. The reaction of such layers with ammonia and other small organic amines leads to the formation of the corresponding sulfonamide and the ammonium sulfonate salt, respectively. To obtain an in-depth understanding of the chemical surface properties and the composition before and after the reaction, we investigated the layers with a variety of methods in particular contact angle (CA) measurements, Zeta-potential measurements, X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (FT-IR). Organic thin film transistors (OTFTs) modified with such interfacial reactive layers between the gate dielectric and the semiconducting polymer show a strong dependence of the electric characteristics on the presence of amines rendering them highly promising for chemical probes and sensors.Another approach towards surface functionalization are UV reactive siloxane molecules. We synthesized organo trimethoxysilane compounds bearing the photoreactive benzyl thiocyanate (SCN) that undergoes a photoisomerization to the benzyl isothiocyanate group (NCS) when exposed to UV light. The benzyl isothiocyanate group is chemically more reactive than the thiocyanate and post modification reactions with amines and thiols can be selectively carried out. FT-IR spectroscopy and XPS are used to confirm the photoreaction and the post modification with amines. Using UV lithographic techniques, patterned surfaces are achieved because only the illuminated areas undergo photoisomerization and subsequently bind amino functionalized molecules. AFM measurements show that resolutions down to a few micrometers can be obtained with contact masks.The herein presented chemical and photochemical reactive layers are of great interest for immobilisation techniques, chemical probes, and tailoring of surface properties of inorganic substrates.Financial support by the Austrian Nano Initiative (RPC0700-RP0701 and RP0702) and the Austrian Science Fund (FWF, S9702-N08) is gratefully acknowledged.
9:00 PM - HH11.48
Polymer Dynamics within Carbon Nanotube Networks.
Jaseung Koo 1 , Kwanwoo Shin 4 , Young-Soo Seo 5 , Tadanori Koga 2 , Seongchan Park 1 , Sushil Satija 6 , Xuming Chen 3 , Kyunghwan Yoon 3 , Benjamin Hsiao 3 , Jonathan Sokolov 1 , Miriam Rafailovich 2
1 Materials Science, State University of New York at Stony Brook, Stony Brook, New York, United States, 4 Department of Chemistry, Sogang University, Seoul Korea (the Republic of), 5 Department of Nano Science & Technology, Sejong University, Seoul Korea (the Republic of), 2 Chemical and Molecular Engineering Program, State University of New York at Stony Brook, Stony Brook, New York, United States, 6 Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 3 Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York, United States
Show AbstractWe have investigated the effect of the multi-walled carbon nanotube (MWNT) on the dewetting dynamics of two immiscible polymer films, a polystyrene (PS) film on a poly(methyl metacrylate) (PMMA) substrate. Nanotubes with different lengths were imbedded in the PMMA bottom layer. From the opening velocity of the dewetting holes, the viscosity of the bottom layer was determined as a function of the mass fraction of the nanotubes. The results showed that the dewetting progress was suppressed by adding long nanotube, resulting in increasing viscosity by a factor of more than 30 compared to the control sample. However, the short nanotube only allowed four times improvement in the viscosity. We understand this difference in terms of a nanotube network which is allowed to form if the nanotubes are longer than the mesh size. Neutron reflectivity was also used to measure the effect of the nanotube on the diffusion of the polymer chains. From the results, we found that the diffusion dynamics were not affected by adding the nanotubes regardless of the length of the tube. These results indicated that no attractive interactions exist between the polymer and the nanotubes. The long-range motion, such as dewetting, is physically obstructed by the nanotube network, even if the overlap distances are large. The short-range motion of the chains is not restricted by the nanotube network since the distance between overlapping points is longer than the entanglement length of the PMMA chains. These different behaviors have been also confirmed by the bulk rheological measurements of the PMMA/MWNT nanocomposites where the nanotubes had a strong effect on the PMMA chain relaxation at low frequencies.
9:00 PM - HH11.49
Nanocomposites of Poly(vinylidene fluoride) with Organically Modified Silicates Containing Gamma Phase Crystals.
B. Seyhan Ince-Gunduz 1 , Kristina Burke 2 1 , Peggy Cebe 1 , Michelle Koplitz 3 1 , Matthew Meleski 2 1 , Ari Sagiv 4 1
1 Physics Department, Tufts University, Medford, Massachusetts, United States, 2 , Gallaudet University, Washington, District of Columbia, United States, 3 , Rochester Institute of Technology, Rochester, New York, United States, 4 , Drexel University, Philadelphia, Pennsylvania, United States
Show Abstract9:00 PM - HH11.5
Electrospun Manganese Oxide Nanofibers as Anode for Lithium-Ion Batteries.
Quan Fan 1 , Ruigang Zhang 1 , Chunmei Ban 1 , M.Stanley Whittingham 1
1 , Binghamton University, Binghamton, New York, United States
Show AbstractNanoscale transition-metal oxides as anode for lithium ion batteries have gained attention recently because of their relative high capacity and high cycle retention. In this paper, electrospinning of polymeric gels, containing poly (methyl methacrylate) (PMMA) and manganese acetate, was successfully used to form manganese oxide nanofibers. The morphology of the nanofibers was examined with SEM and showed their diameters from 100 nm to 300 nm depending on the concentration of PMMA. The spinel Mn3O4 nanofibers with lattice parameters a=5.777 Å,c=9.480 Å was obtained after heating the composite fibers in air. From the TEM images and XRD pattern, the heated manganese oxide nanofibers, which mainly keep the original size, are consisted of many smaller strands with around 20 nm in diameter. The electrochemical behavior of the manganese oxide nanofibers was determined in a lithium cell at 0.5 mA/cm2 on both charge and discharge. The data show a clear and large discharge capacity below 0.5 V, which is quite reproducible after first ten cycles. The electrochemical behavior was characteristic of single-phase behavior. The discharge capacities exceed 600 mAh/g for the first five cycles and maintain a capacity in the range of 450-500 mAh/g for the first 50 cycles, which are comparable to tin-based anode and higher than Co3O4. Considering the much lower cost of manganese, this nanosized oxide warrants further study. This work is supported by the US Department of Energy, Office of FreedomCAR and Vehicle Technologies through the BATT program.
9:00 PM - HH11.50
Dielectric Relaxation Behavior of PVDF/OMS Nanocomposites.
Lei Yu 1 , B.Seyhan Ince-Gunduz 1 , Bret Stenger 1 , Peggy Cebe 1
1 Physics, Tufts University, Medford, Massachusetts, United States
Show Abstract9:00 PM - HH11.51
On Nanophase Decomposition of Eutectoid Zn-Al Alloy Films.
YaoHua Zhu 1 , Sandy To 1 , WingBum Lee 1
1 Industrial and Systems Ingineering, Hong Kong Polytechnic University, Hon Kong, Hong Kong, China
Show AbstractThe structural evolution of the nanofilms of a eutectoid Zn-Al based alloy was studied using X-ray diffraction, scanning electron microscopy and transmission electron microscopy techniques. The decomposition of a nanophase, eta, was discovered to started with clustering to form Z-zones, followed by a transitional phase and metastable phase, which is accompanied with a eutectoid decomposition. another nanophase beta appeared relatively stable during prolonged ageing at 220C. The stability of the nanophase stability is discussed by comparing it with the phase stability of the bulk microstructural alloy. The very strong preferred orientation at (111) crystal planes of the nanophase plays the important role of decomposing the nanophases in the eutectoid Zn-Al based alloy.
9:00 PM - HH11.52
New Imaging Techniques in Raman Spectroscopy - Defining New Standards for High Speed and Nano-scale Imaging Data Acquisition.
Ken Williams 1
1 Spectroscopy Products Division, Renishaw plc, Gloucestershire United Kingdom
Show AbstractRaman spectroscopy continues to provide analytical solutions in a variety of material science applications offering chemical specificity on a micrometer scale.The ability to create chemical and stress images by acquiring Raman spectra from an array of positions and then processing them to reveal the parameter of interest is a powerful technique. Traditionally, these spatially-related data have been collected by raster scanning the sample beneath the incident laser spot, typically in micrometer intervals. New approaches to Raman imaging have been developed that enhance the capabilities of modern Raman instruments. The use of a piezoelectric-controlled sample stage permits accurate and repeatable sample movements in intervals significantly smaller than the diffraction limited laser spot size. When used in conjunction with an atomic force microscope tip, feedback can be applied to ensure the sample’s surface remains in the plane of the laser focus, optimising efficiency. Topographic images of the surface can be correlated with Raman images as the data are acquired simultaneously. This approach is likely to prove useful in the research of semiconductor and biological materials.Additionally, a new method of acquiring confocal Raman images has been developed – ‘Streamline’. Spectra are collected in parallel, rather than in series using the traditional methods. Shorter total acquisition times result, with high quality individual spectra recorded in the order of fifty milliseconds. The method also benefits from ‘on the fly’ data analysis resulting in real time image creation. This innovative approach allows the technique to succeed where others have failed: producing uncompromised data and images for small or large areas at speeds much greater than possible with competing methods. Pharmaceutical, polymer and materials examples will be shown to illustrate the benefits of this method. For example whole tablet Raman chemical images can be produced in less than thirty minutes which offers real advantages for surveying and identifying the real areas of interest.
9:00 PM - HH11.53
Effects of Oxygen Defect Chemistry at HfO2:Si Interfaces.
Chunguang Tang 1 , Ramamurthy Ramprasad 1
1 , university of connecticut, Storrs, Connecticut, United States
Show Abstract Continued miniaturization of microelectronic devices requires the replacement of the conventional SiO2 gate dielectrics by a thin (usually several nanometers) layer of higher dielectric constant material such as HfO2. However, undesirable phases, such as Hf silicide, silicate or SiO2, not predicted by the equilibrium phase diagrams, are often created during processing between the HfO2 layer and the Si substrate. These interfacial phases are detrimental as they could decrease the effective dielectric constant, impact electron mobility in the underlying Si channel, or disrupt the positioning of the band edges at the interface. The mechanism of the formation of such interfacial phases is under debate currently, but is believed to be closely related to the high diffusivity of oxygen defects. In this work we have investigated the evolution of the interface chemistry by performing first principles simulations on the diffusion and accumulation of oxygen defects in the system. Extensive studies of the relative stabilities of several types of Si:HfO2 interfaces in different crystal structures have been performed, and general trends concerning the preferred locations of oxygen vacancies and interstitials with respect to the interface location have been inferred. Energetic barriers for the site-to-site migration of the defects as a function of location were also explored at the first principles level of theory using the nudged elastic band method and molecular dynamics simulations. Our results show unambiguously that oxygen vacancies and interstitials tend to segregate to the interface mediated by both thermodynamic and kinetic driving forces. These computations indicate directly that the local chemistry or bonding at the interface can be impacted by the presence of oxygen defects and due to their mobility, thereby resulting in interfacial phases not predicted by phase diagrams.
9:00 PM - HH11.54
Gradient Copolymers: The Realization of Nanostructured Morphologies in a Purely ``Interphase" System.
Michelle Mok 1 , Jungki Kim 2 , John Torkelson 1 2
1 Materials Science and Engineering, Northwestern University, Evanston, Illinois, United States, 2 Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States
Show Abstract9:00 PM - HH11.55
A Novel Metal/semiconductor Epitaxial Interface at the Nanoscale: NiO-Au Cookie-like Nanoparticles in SiO2 Sol-gel Films Showing Gas Sensing Capability.
Dario Buso 1 , Massimo Guglielmi 1 , Alessandro Martucci 1 , Giovanni Mattei 2 , Paolo Mazzoldi 2 , Michael Post 3
1 mechanical engineering - materials sector, Padova University, Padova Italy, 2 Physics, Padova University, Padova Italy, 3 Institute for chemical process and environmental technology, National Research Council of Canada, Ottawa, Ontario, Canada
Show AbstractThe known favorable lattice match between crystalline Au and NiO (difference between unit cell constants reported as a few hundredths of nm [1]) made possible the growth of unique cookie-like nanoparticles (25 nm mean diameter) inside a porous SiO2 film by tailoring the film synthesis parameters. The unusual aggregates result from the coupling of well defined Au and NiO hemispheres, which are in contact through the (111) and (200) lattice planes, respectively. High resolution TEM analysis revealed that the twofold nanostructures show a sharp flat interface with epitaxial coherence between the Au and NiO phases. Typical Au nanoparticles Surface Plasmon Band (SPR) frequencies are strongly affected by this unique configuration, and result from the overlap of Au, NiO and SiO2 refractive nature. Formation of such peculiar clusters is the result of a complex interplay between ions diffusion and matrix densification that occurs during the annealing process of the nanocomposites. A specific study has been conducted to clarify the dynamics of the aggregates formation, either from a kinetic and a thermodynamic point of view. Moreover the films show a distinct and reversible change in optical transmittance when exposed to CO and H2, a property that can be effectively exploited in optical fibres based gas sensors. A detailed study of the role of the aggregates in the detection process will be presented, as well as a study on the effect of different porous matrix structures on the overall sensing performance. [1] Powder Diffraction File No.: 04-0784 (Au), 78–0643 (NiO)
9:00 PM - HH11.56
Photocatalytic Hydrogen Production from Gas-phase Methanol and Water with Nanocrystalline TiO2 Thin Films in High Vacuum.
Kei Noda 1 , Masashi Hattori 1 , Kouichi Amari 1 , Kei Kobayashi 2 , Toshihisa Horiuchi 1 , Kazumi Matsushige 1
1 Electronic Science & Engineering, Kyoto University, Kyoto Japan, 2 International Innovation Center, Kyoto University, Kyoto Japan
Show AbstractNanocrystalline titanium dioxide (TiO2) thin films have been well studied in various research and industrial fields, which include photocatalysts for water splitting and decomposition of organic molecules, dye-sensitized solar cells and purification methods for air and water. In particular, solar hydrogen production from water and alcohols via photocatalytic reaction has been greatly expected as a promising new clean energy resource for solid fuel cells. However, solar hydrogen production were normally examined in liquids, where the formation and diffusion of hydrogen bubbles inside solutions limit the speed for taking hydrogen gases out of liquid. This would be a shortcoming for driving vehicles and machines with fuel cells at a higher velocity. Therefore a challenge for developing a new system for high-speed hydrogen production should be done.In this background, we focused here on photocatalytic hydrogen production from gaseous methanol and water using nanocrystalline anatase-TiO2 thin films with Pt nanoparticles (TiO2/Pt) in high vacuum. TiO2 films on quartz substrates were prepared by spreading TiO2 gels and successive calcining at around 450°C. The average size of titania crystallites was less than 10 nm. After that, platinum nanoparticles were formed onto TiO2 film surfaces by photoelectrodeposition. A vacuum chamber for gas-analysis during photocatalytic reaction, which is equipped with a quadrupole mass spectrometer, a special home-made gas injecting nozzle and collecting duct, was newly developed. The hydrogen generation process over these TiO2/Pt specimens was investigated under various partial pressures of gaseous methanol and water. As a result, hydrogen generation was successfully detected under ultraviolet ray (UV) illumination even in high vacuum (∼10-7 Torr). This result suggests that protons (H+) separated from gaseous methanol or water by photocatalytic reaction on TiO2 surfaces can move to Pt nanoparticles as cocatalyst and are reduced to H2 gases. This proton movement was probably caused by electric fields on TiO2 surface induced by UV irradiation. This new mechanism of solar hydrogen generation using gas-phase molecules might be possibly applied to high-speed hydrogen production in the future.
9:00 PM - HH11.57
Transport and Optical Characteristics of Al-rich AlO Film and its Application to a Non-volatile Memory.
Shunji Nakata 1 , Shingo Nagai 2 , Minoru Kumeda 2 , Takeshi Kawae 2 , Akiharu Morimoto 2 , Yoshitada Katagiri 1 , Tatsuo Shimizu 2
1 , NTT Microsystem Integration Labs., Atsugi Japan, 2 Grad. School of Natural Sci. & Tech., Kanazawa Univ., Kanazawa Japan
Show AbstractCharge trap memory devices have been attracting increasing attention because they are expected to provide low-voltage-writing operation and large-scale integration. Recent studies have shown that using Al2O3 for the blocking insulator instead of SiO2 leads to operation at much lower voltage [1]. Usually, Al2O3 is fabricated by ALD or MOCVD. However, there remain some problems, such as the presence of residual carbon and the high cost of the fabrication apparatus. We have been trying sputtering methods for the fabrication to resolve these problems [2].In the present work, we succeeded in fabricating Al-rich AlO using a RF magnetron co-sputtering method where a few Al metal plates are set on the Al2O3 target. The Al content of AlO can be controlled by the Al plate area. We used the Al-rich AlO as a charge storage layer for non-volatile Al2O3 memory.Regarding with conduction characteristics, we fabricated AlO films with the thickness of about 50 nm. For Al2O3, the conduction current is smallest, on the order of 10-8 A/cm2 at 200 kV/cm. For Al-rich AlO, it is on the order of 10-4 A/cm2. This is due to the increased trap sites in the insulator.Experimental optical absorption characteristics are also changed with the Al content of AlO. Al2O3 shows almost no optical absorption in the wavelength range from 250 to 2500 nm. On the other hand, Al-rich AlO shows large optical absorption. This is also due to the increased trap sites.Next, we fabricated an Al2O3 memory structure using an Al-rich layer. First, 31 nm of Al2O3 was deposited as a tunnel insulator using ordinary RF magnetron sputtering on Si wafers. Next, 44 nm of Al-rich AlO was deposited as a charge storage layer by the co-sputtering method. Finally, 33 nm of Al2O3 was deposited as the blocking insulator, successively.We measured the high-frequency C-V characteristics of this sample at 1 MHz. The hysteresis voltage window ΔV was 17.5 V when the gate voltage was ±20 V.The stored charge per unit area ΔQ can be evaluated as ΔQ=CbΔV/2, where Cb is the capacitance per unit area of the blocking insulator [3]. The Cb is written as Cb=ε/db, where db is the blocking-insulator thickness. We assume that charges are trapped in a range of about 10 nm from the tunnel insulator. This assumption is valid, from the previous work [3]. Then, we can estimate db as 33+(44-10)+(10/2)=72 nm. Therefore, ΔQ is estimated to be 9.7x10-7 C cm-2, so that the electron trap density [Ne=ΔQ/(10nmx1.6x10-19 C)] is estimated to be 6.1x1018 cm-3. This value is almost the same as that of MNOS, 7x1018 cm-3 [3]. Moreover, the electrical field E in the present Al2O3 memory is 37 % that of MNOS memory. This low E writing is thought to be the effect of the increased trap sites produced by the Al-rich AlO structure.[1]C.H. Lee et al., APL 87, 073510 (2005).[2]S. Nakata et al., Electronics Lett. 41, 721 (2005).; APL 87, 223110 (2005).; JJAP 45, 3176 (2006).[3]S. Minami et al., IEEE ED 38, 2519 (1991).
9:00 PM - HH11.58
Growth and Characterization of a Combinatorial Array of Mixed-Phase Magnesium–Aluminum Thin-Film Alloys.
Charles Olk 1 , Daad Haddad 1
1 Materials & Processes Lab, General Motors Research Development & Planning, Warren, Michigan, United States
Show Abstract9:00 PM - HH11.59
The Construction of Rambutan-like Crystalline Tin@Carbon Nanoarchitecture and Its Reversible Li+ Storage Properties.
Da Deng 1 , Jim Yang Lee 1
1 Chemical and Biomolecular Engineering, National University of Singapore, Singapore Singapore
Show AbstractGeneration of complex nanoarchitectures from simple building blocks (e.g. nanospheres & nonorods) is still a significant challenge in nanotechnology. In some cases self-assembly chemistry may be used to advantage as a fabrication tool. We report here a simple procedure (Scheme 1) enabling the construction of a complex Rambutan-like nanoarchitecture of carbon encapsulated crystalline metallic tin composite. The nanounits involved in the construction of the “skin” of the 3-D carbon mesospheres were “protruding” 1-D carbon nanotube coaxially encapsulated tin nanorods, and 0-D carbon encapsulated tin nanopears/particles. The “core’ of the 3-D carbon mesospheres consisted exclusively of 0-D tin nanoparticles. The unique Rambutan-like nanocomposite was thoroughly characterized by FESEM, TEM, XRD, EDX. A modified “base-growth” mechanism was used to explain the formation of the beautiful Rambutan-like nanoarchitecutre. The reversible Li+ storage properties of the nanocomposites were evaluated to demonstrate a potential application of this nanomaterial in lithium ion batteries. Scheme 1. A simplified scheme for the design and fabrication of the Rambutan-like carbon-tin composite nanoarchitecture.
9:00 PM - HH11.6
Design and Synthesis of Redox Active Capping Agents for Gold Nnanoparticles (AuNPs).
Jhinuk Gupta 2 , Sajini Vadukumpully 2 , Suresh Valiyaveettil 2
2 Department of Chemistry, National University of Singapore, Singapore, Singapore, Singapore
Show Abstract9:00 PM - HH11.60
Phase Separation in Silica Sol-gel System Containing Anionic Surfactant.
Taisuke Matsui 1 , Kazuki Nakanishi 1 , Kazuyoshi Kanamori 1 , Teiichi Hanada 1
1 Chemistry, Graduate School of Science, Kyoto University, Kyoto Japan
Show AbstractMonolithic silica gels with controlled macropores via the polymerization-induced phase separation and concurrent sol-gel transition have been prepared in the systems containing anionic, cationic and neutral polymers as well as in those containing neutral and cationic surfactants. Due to their strong acidity, the solubility of anionic surfactants carrying sulfate group depends strongly on the solvent composition. In addition, mixed surfactant systems are reported to exhibit unique feature in templating mesoporous oxides in nanometer ranges.In the present experiment, we adopted three kinds of anionic surfactants which differ from each other in the length of hydrocarbon chain (CH3(CH2)17SO3Na,CH3(CH2)15SO3Na,CH3(CH2)13SO3Na). Tetramethoxysilane (TMOS) was hydrolyzed in the presence of one of the above surfactants using nitric acid as a catalyst. The starting mixture was vigorously stirred for hydrolysis, and kept closed at a constant temperature for gelation. Gels thus prepared were solvent-exchanged with water/methanol followed by the evaporation-drying at 60 °C. Some of the dried gels were heat-treated at 650 °C for 2 h. The macroporous morphology of the dried gels was examined by a scanning electron microscope (SEM) and the mesoporous structure was analyzed by nitrogen adsorption method.Silica monoliths with well-defined co-continuous macroporous were obtained from the systems containing either of the surfactants. Due to the moderate interaction between silica oligomers and surfactants, most of the surfactants are distributed to the solvent phase which determines the macropore volume. The median size and volume of the macropores could be controlled independently by the starting composition. In the absence of any additive to enhance templating by the surfactant, the samples exhibited only amorphous mesopores. Effects of addition of co-surfactant or pore-expander will be examined in detail using nitrogen adsorption, XRD and FE-SEM observation.
9:00 PM - HH11.61
Drying Evolution of Mesopore Structure of Hierarchically Macro/mesoporous Silica by Thermoporometry.
Etsuji Fukui 1 , Keisuke Shinohara 1 , Kazuki Nakanishi 1 , Kazuyoshi Kanamori 1 , Teiichi Hanada 1
1 Chemistry, Graduate School of Science, Kyoto University, Kyoto Japan
Show AbstractThermoporometry is a method for characterizing pore structure from melting or freezing point of a substance confined in pore spaces. Determining pore size distributions theoretically requires temperature dependence of physical parameters such as surface tension, contact angle, heat of fusion, and specific volume. However, literature values for these parameters are not confident to direct transformation of phase transition temperature into absolute pore size distributions. Thus, we must resort to indirect transformation using empirical formula derived from reference materials that have been carefully measured by complementary methods, such as mercury intrusion or nitrogen adsorption. The technique enables evaluation of pore structure with a material in wet condition. Some physical parameter changes from wet condition to dry condition or the reverse can be measured by thermoporometry. Monolithic silica having hierarchical macro/mesopores can be prepared by a sol-gel process accompanied by phase separation. Using a surfactant both as a template a phase-separation inducer, gels with well-defined macropores and long-range ordered mesopores can be obtained in alkoxy-derived silica systems. Depending on the pore size distribution mainly in micro- and mesopore regimes, the evolution of pores templated by the surfactants and those formed as interstices among the structural units will take place in each of the fabrication stages such as gelation, aging, drying and heat-treatment. In the present study, we have examined the relation between freezing/melting points of pore-confined water measured by DSC and the pore size distribution which was reliably measured by nitrogen adsorption. In the case of cylindrical mesopores template by surfactant molecules, the pore size distribution was not affected by the length of the pores. An evaluation by thermoporometry has been done of micro/mesopore distribution of porous silica through aging and solvent exchange processes. Even in the presence of template molecules, thermoporometry was proven to be a useful tool to detect the change in pore structure in the wet state.
9:00 PM - HH11.62
White Cast Iron with Network Morphology – its Formation and Properties.
Yip Yeuk Lan 1 , Leung Ching Chuen 1 , Mok Siu Wah 1 , Kui Hin Wing 1
1 Physics, The Chinese University of Hong Kong, Hong Kong China
Show Abstract9:00 PM - HH11.63
Stress-Induced Noble Metal Nanostructure on Silicon.
Luohan Peng 1 3 , Hong Liang 1 2
1 Materials Science and Engineering, Texas A&M University, College Station, Texas, United States, 3 Physics, Texas A&M University, College Station, Texas, United States, 2 Mechanical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractWe demonstrate that using an atomic force microscope (AFM), nanostructures can be produced through mechanical force. The formation of a thin line was accomplished by simply sliding a gold (Au) or silver (Ag) coated AFM probe against a single-crystalline silicon (Si) at room temperature. Different processing parameters were applied to fabricate the line-like nanostructure in both Au-Si and Ag-Si systems. It was found that the Au and Ag line nanostructures have similar topographic properties. Interestingly, the line structures are independent of the crystal orientation of Si substrate. Comparing Au and Ag, it is noticed that Ag requires a higher number of sliding strokes than that of Au in order to form a line. Discussions on mechanical and thermal energy dispersion in this presentation helps to understand the process developed here.
9:00 PM - HH11.64
Thermal and Electric Data Writing into Metal/oxide Interface: 2D Reactions at Metal/yttria Interface Observed by X-rays.
Masashi Ishii 1 , Aiko Nakao 2 , Kenji Sakurai 1
1 ICYS, National Institute for Materials Science (NIMS), Tsukuba, Ibaraki, Japan, 2 , RIKEN, Wako, Saitama, Japan
Show AbstractIn recent years, interface chemical reactions are considered to be applicable for data storage. Since quasi-stable chemical states correspond with the on/off states in memory devices, quick alternation of the chemical states would be high frequency switching. As another advanced example, selective reaction at buried interface can be used for durable data print in media, post-formation of nano-structures in layer structures, etc. For these attractive applications, we focused on interface oxidization-reduction at metal/yttria (Y2O3) interface, and evaluated it by x-ray analyses.The interface structure was made by the following procedure. Y2O3 was deposited on Si wafer with a metalorganic decomposition method. On the Y2O3 thin layer, Pt or Au was deposited by a sputtering. The thicknesses of the Y2O3 and metal were ~50 and ~30 nm, respectively. In our experiments, thermal or electric perturbation was applied to induce the interface reactions. We evaluated the Pt/Y2O3 and Au/Y2O3 interface reactions by X-ray reflectometory (XRR) and X-ray photoemission spectroscopy (XPS). The XRR measurement can non-destructively provide structural information at the interfaces with high depth resolution less than nm. In addition to the structure information by XRR, the XPS analyses can reveal the chemical states at the interfaces. In the thermal perturbation, the key point is how the selective reaction at interface can be induced without surface modifications. For this purpose, we used catalysis between metal and Y2O3; O would transfer from Y2O3 to the metal at low temperature. We performed the annealing of metal/Y2O3 at 373 K in nitrogen ambience. During the annealing, the surface morphology observed by atomic force microscopy was not changed. In fact, the unchanged surface roughness of ~0.82 nm (rms) for Pt and ~0.66 nm for Au was obtained. On the other hand, the XRR measurement indicated that Pt reacted with Y2O3 gradually and Pt/Y2O3 interface was stabilized after 90 min annealing. Similar XRR measurement revealed that Au reacted with Y2O3 significantly and the most coherent Au/Y2O3 interface was observed after 60 min annealing. These findings indicate the thermal printing at interface; the post-formation of an interface structure can be achieved. In electric perturbation, we confirmed that Pt/Y2O3 system has a non-volatile memory effect in resistance: a positive bias change the system to a low-resistance state, and following a negative bias transform it a high-resistance state. The hysteresis of resistance should be random access memory in the next generation. In XPS analyses, we confirmed the formation of Pt(OH)2, PtO2, and YOOH at the interface. This finding can be understood as the electrically induced O transfer from Y2O3 to Pt and following reaction with water in the atmosphere. The memory effect would be caused by alternative O transfer between Pt and Y2O3.This work was supported by KAKENHI, Grant-in-Aid for Scientific Research (C) (19560029).
9:00 PM - HH11.66
Controlling Space Charge Properties in Nanocrystalline Electroceramics by Heterogeneous Doping.
Scott Litzelman 1 , Harry Tuller 1
1 Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractNanocrystalline electroceramic materials show great potential for improvements in ionic and/or electronic conductivity due to space charge effects at grain boundaries and other interfaces [1]. Much effort has been made to better understand the relationship between nanocrystalline grain size and variations in electrical conductivity. In this work, a novel approach is undertaken: the attempt to control space charge properties in nanocrystalline electroceramics by heterogenous doping. Thin films of cerium oxide and Gd-doped ceria were deposited by pulsed laser deposition (PLD) and displayed grain sizes on the order of 20-45 nm and a columnar morphology. The thin films were modified by deposition and precisely-controlled in-diffusion of cations such as Ni and Gd at temperatures from 600-800C along the grain boundaries. Electrical characterization via impedance spectroscopy showed these modified films to be approximately ten times less conductive than as-deposited samples, yet with no apparent change in conduction mechanism. These data are presented and analyzed with respect to the space charge potential that exists in grain boundary cores. This work is supported by the NSF under grant DMR-0243993.[1] J. Maier, Solid State Ionics 154-155 (2002) 291-301.
9:00 PM - HH11.67
Control of Surface Chemistry by Electronic Structures.
Sreeya Sreevatsa 1 , Yan Zhang 2 , Haim Grebel 3
1 Applied Physics, New Jersey Institute of Technology, Newark, New Jersey, United States, 2 Electrical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States, 3 Electrical Engineering, New Jersey Institute of Technology, Newark, New Jersey, United States
Show AbstractWe set to control ionic currents to and from a surface by adding a transistor-like structure in front of it. As an example, we examine the corrosion of metallic surfaces which are interfaced with alternate layers such as, n-p-n or p-n-p. The chemistry at an interface is dictated by the concentration of the ionic species and its potential distribution. One may provide with an ion-gating mechanism, maintained through electronic currents, by adding a permeable, multilayered semiconductive doped structure in front of the surface. Such construction may be useful for electronic control of various membrane functions as well as, study of ionic currents through such structures. In the past, passive protective films on iron have been extensively studied using potentiodynamic polarization measurements. We used this technique to carefully monitor the oxidation and reduction rate under biasing electronic currents.Imbedding microelectronic concepts in electrochemistry and biochemistry has been implemented mainly by two common concepts: 1. a gate potential is used to control ions in an isolated and inherently charged, nano-channel or, 2. ions in solution are affecting the gate potential of an otherwise pure electronic device (for example, Ion Selective Field-Effect Transistor, or, ISFET). In contrast, we propose here a different approach whereby ionic current is driven across a (permeable) structure much like the BJT construction. The control over the ionic current is made by applying electronic current at the structure base electrode thus, changing the electronic band structure. Our membrane is made of functionalized Single wall Carbon Nanotubes (SWCNT) layers. By using polymers we achieved p- and n-type, mostly individual SWCNT. Thin films of functionalized SWCNT were successively deposited on a steel substrate. By alternating the film type we achieved either p-n-p or n-p-n complex. This multi-layered permeable structure was then introduced into an electrochemical cell. A typical cell has three electrodes: emitter (working), collector (counter) and reference electrodes. A biasing electrode is added to the middle layer of the permeable structure (say, the n-layer in a p-n-p structure) for ionic current control purposes. The entire element may be viewed as a common emitter (CE).Anodic reaction (corrosion) took place at the p-n-p/working electrode interface. Tafel plots, obtained through potentio-dynamic measurements, showed that the p-n-p coated iron exhibited a much smaller corrosion current compared with its bare steel counterpart. As we were biasing the transistor-like structure, an interesting oscillatory behavior of the corrosion current was noted.In summary, we affected ionic currents by biasing transistor-like structures during corrosion experiments.
9:00 PM - HH11.68
Effect of the Density and Conductivity for the Photocatalytic Activity of CdS Films.
Hideyuki Takahashi 1 , Akihiro Takahashi 1 , Kazuyuki Tohji 1
1 Tohoku Univ., Environmental studies, Sendai Japan
Show AbstractRecently, many researchers reported that natural energy should be utilized for the human life because of the depletion of fossil fuel and also the environmental problem. Among the various methods to utilizing the natural energy, photocatalytic decomposition of hydrogen sulfide (H2S) into hydrogen (H2) is considered as efficient route for the conversion of natural energy (solar energy) into clean energy (H2). On the other hand, photodecomposition rate of water is relatively low because of its low electrolysis potential. Moreover, photocatalytic decomposition system of H2S may lower the energy consumption, since quite large amounts of energy was consumed for the decomposition of harmful H2S gas evolved from various plants. Among the various semiconductor materials, only the sulfide type photocatalyst can act stably in the H2S solution, while metallic and/or oxide type photocatalyst is sulfurized. Taking the industrial use of the photocatalyst into consideration, film type photocatalyst has the great advantages as compared with the powder type form. However, in generally, catalytic activity of the film type photocatalyst was lowered than the powder type form, nevertheless former was constructed by using the later. Thus, it can be considered that the photo-excited electron’s path between the photocatalytic particles is limited in the films type form. Therefore, in this study, relationship between the “density and/or conductivity of CdS thin films” and “photocatalytic activity of CdS thin films” were evaluated by using the cadmium sulfide (CdS) thin film synthesized by the chemical bath deposition (CBD) method.CdS thin films were prepared by CBD method. Ti plate, with and without Cd plating, were used as substrate. Synthesized CdS thin films were physically pressed at from 100 to 500 kg/cm2 for 1h, and were evaluated by the XRD (Rigaku, MULTI FLEX) and SEM (Hitachi, S-4100). Photocatalytic activity was evaluated by measuring the photocurrent under the Xe lamp (15.2W/6.0cm2, Wakom: KXL-552HPF) irradiation in the 0.1M Na2S solution at 22 degree. CdS thin film and Pt were used as anode and cathode, respectively. Results of the photocatalytic activity measurement of the CdS thin film was clearly demonstrated that it was seriously depended on the film density and conductivity between CdS particle and substrate. Photocatalytic activity of the CdS thin films, which gap of the CdS particles were filled with the electrical pass (Cd metal) and density of the film was increased, was about 1.7 times higher than the traditional CdS film.
9:00 PM - HH11.69
Fabrication, Characterization and Field Emission Properties of Potassium Tungsten Bronze Nanostructures.
Ting Yu 1 , Zhe Zheng 1 , Bin Yan 1 , Yumeng You 1 , Zexiang Shen 1 , Jixuan Zhang 2 , Hao Gong 2
1 physics, nanyang technological university, Singapore Singapore, 2 Materials Science and Engineering, National University of Singapore, Singapore Singapore
Show AbstractThe single-crystalline potassium tungsten bronze nanostructures have been successfully synthesized directly from tungsten metal foils by a rather simple method. The morphologies of the nanostructures are able to be tuned as rodlike, ribbonlike or sheetlike by simply varying the heating temperatures. Scanning electron microscopy (SEM) study on the dynamic growth process of a specific individual nanoribbon elucidated the growth mechanism is the tip-growth vapor-solid (VS) process in this work. Polarized micro-Raman scattering is employed to study the crystal properties of individual nanoribbons and nanosheets. Both the Raman spectra and images revealed the single crystalinity of the nanostructures. In the past few decades, although much attention has been paid to tungsten bronzes due to their photochromic1 and superconducting properties2 there is no electron field emission study on potassium tungsten bronze nanoribbons. In this work, field emission properties of the nanoribbon arrays are also investigated. This is believed to be useful and important for both the fundamental study and practical application of tungsten bronze nanostructures as a future display medium.1.S. Reich, Y. Tsabba, Eur. Phys. J., 1999, B9, 1–4.2.L. H. Cadwell. R. C. Morris, W. G. Moulton, Phys. Rev. B, 1981, 23, 2219 – 2223.
9:00 PM - HH11.7
Structural Characterization of Nanocrystalline Apatites Obtained by Mechanochemical Synthesis.
Ivonne Rosales 1 , Lauro Bucio 1 , Eligio Orozco 1 , Carlos Magana 1
1 Solid State Department, Universidad Nacional Autonóma de México, Mexico, D.F, Mexico
Show Abstract9:00 PM - HH11.70
Investigation of Phase Transition in Stacked Ge-Chalcogenide/Sn-Chalcogenide Phase-change Memory Films.
Feiming Bai 1 , Surendra Gupta 2 , Archana Devasia 1 , Santosh Kurinec 1 , Kris Campbell 3
1 Microelectronic Engineering, Rochester Institute of Technology, Rochester, New York, United States, 2 Mechanical Engineering, Rochester Institute of Technology, Rochester, New York, United States, 3 Electrical and Computer Engineering , Boise State University, Boise, Idaho, United States
Show AbstractPhase-change random access memory, also called phase-change memory (PCM), is an emerging nonvolatile, resistance variable memory technology based on very fast amorphous to crystalline phase transition.[1] Most previous research in PCM materials has focused on chalcogenide materials that have been applied for rewritable optical recording disks. Among the many chalcogenide materials, Ge2Sb2Te5 (GST) has widely been used because of its fast crystallization speed, very high overwrite cycles and a long archival life time of more than 10 years.[2] However, the major obstacle of GST memory cell is the large programming current, which leads to high power consumption and reduced life cycles.[3] Stacked Ge-Chalcogenide/Sn-Chalcogenide phase change layers recently show promise with a low programming current, <10^(-4)A, and endurance greater than 2 million cycles.[4] However, the phase transition and voltage polarity phenomenon in the bilayers are not well understood. In current work, the phase transition of amorphous Ge-Chalcogenide layer (Ge2Se3) has been studied using an area detector set-up (D8 Discover, Bruker) by monitoring the d-spacing change of crystalline Sn-Chalcogenide layer (SnTe) as a function of temperature. A broad phase transition has been identified starting at ~180oC, far below the glass transition temperature of bulk Ge2Se3, ~340oC. Phase structure and residual stress analysis show that the phase transition includes three stages: (i) migration of Sn atoms/ions into Ge2Se3 network and significant increment of tensile stress; (ii) separation of SnSe phase at ~270 oC; and (iii) formation of new chalcogenide solid solution, which is preserved to room temperature. I-V curve measurement of annealed samples at different temperatures showed that the resistance changed dramatically near 270oC, corresponding to the formation of SnSe phase in Ge2Se3 network. The contribution of the SnSe phase in the amorphorous Ge2Se3 network to the desired change of electrical resistivity in phase-change material is discussed.Key words: Phase Change Memory, Crystallization, XRD2, Reference:1. A. L. Lacaita, Solid State Electronics, 50 (2006), 24-312. N. Yamada, E. Ohno, K. Nishiuchi and N. Akahira: J. Appl. Phys. 69 (1991), 2849-2856 3. S. Lai, Electron Device Meeting, 2003, IEDM’03 Technical Digest, IEEE International, 2003, p10.1.1-10.1.44. Campbell, K.A. and Anderson, C.M. Microelectronics Journal 38 (2007) 52-59
9:00 PM - HH11.71
Mechanism of the Electrophoretic Deposition of CdSe Nanocrystal Films.
Shengguo Jia 1 2 , Sarbajit Banerjee 1 2 , Irving Herman 1 2
1 MRSEC, Columbia University, New York, New York, United States, 2 Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York, United States
Show AbstractThe charge on nanocrystals is not only used to stabilize the colloidal systems but also to assemble these materials into novel films and superlattices. Here, we propose a model for the charging of colloidal CdSe nanocrystals in non-aqueous solvents involving the dissociation of ligand molecules from specific surface sites. We also develop a mechanistic model to explain the electrophoretic deposition of nanocrystal films based on electrophoretic mobility measurements, photoluminescence from nanocrystal solutions and films, and observations from deposition experiments. Even though equally thick nanocrystal films are obtained on both negative and positive electrodes, the numbers of positive and negative nanocrystals are not equal in solution. After appropriate reprecipitation cycles, the surface ligands on colloidal CdSe nanocrystals are partially removed, giving rise to unpassivated surface sites that may enable the nanocrystals to better “stick” to electrodes during electrophoretic deposition. Thus, the surface charge of the nanocrystals is very significantly influenced by the presence of coordinating ligands. The factor limiting the maximum thickness achievable by electrophoretic deposition is thought to be the concentration of the minority charged nanocrystals (negatively charged nanocrystals in our experiments). Analogous results are obtained for mixtures of different sized CdSe nanocrystals, as well as oxide nanocrystals, indicating that the proposed model may be widely generalizeable to different kinds of colloidal nanocrystals. This work was supported primarily by the MRSEC Program of the NSF under Award No. DMR-0213574 and by NYSTAR.
9:00 PM - HH11.72
Porous High Temperature Ceramics Structured on Multiple Length Scales.
Marleen Kamperman 1 , Robert Weissgraeber 1 , Andrew Burns 1 , Ulrich Wiesner 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States
Show Abstract9:00 PM - HH11.74
Characterization of Self-Assembled Hexadecanethiolates Grown on Silver Islands.
Liang Hu 1 , Leslie Allen 1
1 Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States
Show AbstractWe describe preliminary work on self-assembled hexadecanethiolates which grow on three-dimensional Ag islands (diameter less than 20 nm). Infrared spectroscopy study of these hexadecanethiolates reveals that they are of high conformational order. The characteristics of melting (Tm, Hm, Sm) and specific heat are studied by measuring heat capacity with NanoDSC [1], which has high heating rates (~30 000 K/s) and cooling rates [2, 3]. Two different melting transitions are observed, which indicates the co-existence of two different phases. The relative amount of these two phases can be changed by adjusting the heating and cooling schedules. X-ray diffraction confirms that the phase with the higher melting point is of layered structure.Reference:[1] Zhang, Z.S., Allen, L.H., et al., Heat Capacity Measurements of Two-dimensional Self-assembled Hexadecanethiol Monolayers on Polycrystalline Gold. Applied Physics Letters, 2004. 84(25): p. 5198.[2] Efremov, M.Y., Allen, L.H., et al., Ultrasensitive, fast, thin-film differential scanning calorimeter. Review of Scientific Instruments, 2004. 75(1): p. 179.[3] Efremov, M.Y., Allen, L.H., et al., Glass transition in ultrathin polymer films: Calorimetric study. Physical Review Letters, 2003. 91: p. 085703.
9:00 PM - HH11.75
Development of Micro- and Nanocellular Polymers.
Holger Ruckdaeschel 1 , Peter Gutmann 1 , Volker Altstaedt 1 , Holger Schmalz 2 , Axel Mueller 2
1 Polymer Engineering, University of Bayreuth, Bayreuth Germany, 2 Macromolecular Chemistry II, University of Bayreuth, Bayreuth Germany
Show AbstractThe growing importance of polymer foams, for example for light-weight structural applications and for thermal insulation, implicates steadily growing requirements to the materials performance. It is therefore highly desirable to develop new materials and processes for controlling the foam density, but also the cell sizes over multiple length scales, down to the nanocellular range - both factors of primary importance for the property profile. Such tailored materials can potentially show enhanced mechanical properties as well as significantly reduced thermal conductivities. As a promising approach to meet the demand for such novel cellular materials, the foaming of nanostructured polymer blends and block copolymers was systematically investigated. In order to obtain nanostructured blends, immiscible poly(2,6-dimethyl-1,4-phenylene ether) / poly(styrene-co-acrylonitrile) (PPE/SAN) blends were melt-compatibilised via polystyrene-b-poly(1,4-butadiene)-b-poly(methyl methacrylate) triblock terpolymers (SBM). Due to the specific interaction between the respective components, a nanostructured interphase between PPE and SAN is generally observed. With regard to neat block copolymers, the self-assembly of solvent-cast SBM triblock terpolymers was exploited in order to produce nanostructured morphologies. As an example, equal weight contents of each block led to lamellar structures of polystyrene, poly(1,4-butadiene) and poly(methyl methacrylate). Subsequently, batch foaming of both blends and block copolymers was performed using carbon dioxide as a blowing agent. The resulting foam morphology was characterized by evaluating the foam density as well as the cell size. Moreover, transmission electron microscopic observations provided an in-depth insight into the cell wall morphology. Combined with the nanoscale structure of the non-foamed material and its thermal as well as rheological behavior, relationships between the foaming characteristics and the cellular morphology were systematically established. On the one hand, submicro-cellular foams were observed by foaming PPE/SAN blends compatibilised by SBM triblock terpolymers, while the cell walls still revealed the nanostructured morphology. On the other side, the batch-foaming of neat SBM triblock terpolymers led to the formation of microcellular foams; however, as highlighted by scanning electron microscopy, the cell walls did undergo some further expansion and formed additional, nano-sized cells. In the light of these results, new routes for processing submicro- and even nanocellular polymers are derived by systematically exploiting the multiphase characteristics of polymer blends and block copolymers.
9:00 PM - HH11.76
Effect of Crystalline Structure of CdS Nanoparticles on the Photocatalytic Activity.
Shun Yokoyama 1 , Hideyuki Takahashi 1 , Kazuyuki Tohji 1
1 Tohoku Univ., Environmental Studies, Sendai Japan
Show AbstractThe visible light active type photocatalyst has been vigorously studied because of its great potential to generate the new energy (hydrogen) by photo-splitting of water. However, reaction rate of photo-splitting of water into H2 and O2 is low since theoretical electrolysis potential of water is relatively high. On the other hand, photocatalytic decomposition of hydrogen sulfide (H2S), which has about 4 times low theoretical electrolysis potential than water, is considered as an efficient alternative route to produce H2 compared with the splitting of water. Recently, Arai et.al reported that the synthesis of CdS nano-sized capsule like formed particle which had the gradient Cd concentration in its wall, called as “stratified CdS nanoparticles”, and demonstrated that these materials showed the high photocatalytic activities for the decomposition of H2S. Stratified CdS nanoparticles was synthesized by the reaction between Na2S and Cd(OH)2 or CdO nanoparticles. However, they had not discussed the effect of the crystal structure and crystalline structure of the stratified CdS nanoparticles nevertheless catalytic activity was seriously depended on these properties. Therefore, in this study, well-crystallized stratified CdS with uniform crystal structure was tried to synthesize, and effect of the crystalline structure for the photocatalytic activity of stratified CdS nanoparticles was studied. Crystal shape and crystalline structure of stratified CdS was seriously depended on the precursor materials. For the synthesis of well-crystallized stratified CdS, it is important to improve the crystallinity of precursor materials. Cd(OH)2 type precursor material has the two crystalline phase, one is hexagonal and another is monoclinic. By the traditional method, stratified CdS photocatalyst was synthesized from mixture of them. Therefore, we tried to synthesize the Cd(OH)2 which has single crystal phase by controlling the treating temperature, concentration of Cd ion in the solution, and the amount of the NaCl added. Moreover, crystallinity of precursor materials was tried to improve by heat converting from Cd(OH)2 type precursor to CdO type precursor. Crystal shape and photocatalytic activities of stratified CdS was seriously depended on the type of precursor compounds, while crystalinity of stratified CdS showed negligibly changed between the difference of the crystallinity of precursor materials. These results clearly demonstrated that, for the synthesis of well-crystallized stratified CdS, it is important to control the sulfurized reaction rate or improve the crystallinity of CdS nanoparticles after synthesized. At the meeting, the relationship between these factor and the photocatalytic activities of stratified CdS will be discussed.
9:00 PM - HH11.78
Synthesis of the Colloidal CdSe Quantum Rods and Their Optoelectronic Properties.
Chinho Park 1 , Umme Farva 1 , Young Na 1 , Truong Nguyen 1
1 School of Display and Chemical Engineering, Yeungnam University, Gyeongsan, Gyeongsangbuk-do, Korea (the Republic of)
Show Abstract9:00 PM - HH11.8
Absorption and Photoluminescence Polarization Anisotropy of Single CdSe Nanowires.
Aidong Lan 1 , Valdimir Protasenko 1 , Masaru Kuno 1
1 Chemistry and Biochemistry, Univ. of Notre Dame, Notre Dame, Indiana, United States
Show AbstractThe polarization studies of semiconducting nanowires (NWs) are of particular importance to understand the basic electronic and optical properties of these one dimensional nano-structures. Therefore, the experimental polarization results obtained solely from single NWs are highly desirable. In this talk, we present a comprehensive experimental study on both absorption and photoluminescence polarization anisotropy of single CdSe NWs. The CdSe NWs employed in this study was synthesized by a recently developed solution-liquid-solid (SLS) reaction scheme. The high crystallinity and uniformity of Nanowire were confirmed by high resolution transmission microscope characterizations. The diameters of the wires range from 5 nm to 30 nm, well within the quantum confinement regime, while the lengths of NWs easily exceeds 1 micronmeter. The morphology of single NWs will vary from straight to distinct V-shaped and tripods depending on the ratio of precursor concentration. The single NWs measurements of this study are ensured by deliberately selecting such branched wires. The high polarization anisotropy values (ranging from 0.6 to 0.9) are obtained on both photoluminescence and absorption spectra from all examined single CdSe wires. The dependence of anisotropy values on the NWs diameters, excitation energy and dielectric environment were investigated. It is found that the NWs with larger diameter showed evidently higher anisotropy values than their thinner counterpart, while only weakly dependence of anisotropy was observed on dielectric environment and excitation energy. An interesting intra-wire anisotropy variation was probed on branched wires and we attributed it to attenuated dielectric constant contrast. In addition, prominent anisotropy spectral dependence was manifest in photoluminescence polarization study. All above phenomenon was discussed in the context of existence of two origins of anisotropy, i.e., classic dielectric constant contrast effect and intrinsic quantum confinement effect.
9:00 PM - HH11.9
Topotatic Synthesis of Mesoporous ZnS and ZnO Nanoplates and Their Photocatalytic Activity.
Jum Suk Jang 2 3 , Chung-Jong Yu 1 , Sun Hee Choi 1 , Jae Sung Lee 2 3
2 Department of Chemical Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 3 School of Environmental Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 1 Beamline Research Division, Pohang Accelerator Laboratory, Pohang Korea (the Republic of)
Show AbstractThe application of nanostrucured ZnS and ZnO are strongly dependent upon specific morphology and textural properties such as surface area and porosity. While one-dimensional nanowires and nanorods have been extensively studied, two-dimensional (2-D) nanostructured materials have not attracted much attention recently. However, high potentials as chemical and biological sensors, nanoelectronic devices, and catalysts, raise significant interest in the development of 2-D nanomaterials with high surface area and large pore volume. In this study, we fabricated mesoporous ZnS and ZnO nanoplates by calcinations of ZnS(en)0.5 complex, which was solvothermally synthesized using ethylenediamine(en) as a single solvent. When the ZnS(en)0.5 complex was heated, ethylenediamine bound to the complex was gradually decomposed at 673-773 K, producing mesoporous nanoplates with the pore size of 3-15 nm which was composed of wurtzite ZnS crystallites embedded into amorphous ZnS(en)0.5. Further oxidation of the complex at 873 K caused the transformation to ZnO while maintaining the porous morphology, but increasing the pore size to 10-30 nm. The transformation of the materials was characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), synchrotron powder x-ray diffraction, x-ray absorption near-edge structure (XANES), and extended x-ray absorption fine structure (EXAFS). The transformation process of the ZnS(en)0.5 → ZnS → ZnO appeared to be topotatic because of the crystallographic relation among their structures. As a result, nanoporous single crystalline ZnS(en)0.5 nanoplates were transformed into mesoporous but still single-crystalline ZnS and ZnO nanoplates exhibiting pseudomorphism. Photocatalytic performance of the materials was investigated for hydrogen production from aqueous Na2S/Na2SO3 solution and decomposition of azo dye acid red 14. The ZnS(en)0.5-derivatived ZnS calcined at 773 K exhibited the highest hydrogen production rate of ~9.0 μmol/h through water splitting under visible light, and more than 90% of the dye was photocatalytically degraded over ZnO calcined at 823-873 K upon uv-irradiation for 100 min.