Stephanie Brock Wayne State University
George Gould Aspen Aerogels
Anna Roig Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC)
Debra Rolison U. S. Naval Research Laboratory
BB4: Poster Session
Monday PM, November 29, 2010
Exhibition Hall D (Hynes)
1:00 AM -
BB4.10 Transferred to BB8.5
1:00 AM -
BB4.14 Transferred to BB3.3
1:00 AM -
BB4.23 Transferred to BB3.2
BB1: The Final Frontier
Monday AM, November 29, 2010
Room 103 (Hynes)
9:30 AM - **BB1.1
A History of the Solar System Captured in Aerogel: Analysis of STARDUST Cometary and Interstellar Samples.
Rhonda Stroud 1 Show Abstract
1 Code 6366, Naval Research Laboratory, Washington, District of Columbia, United States
The NASA STARDUST spacecraft deployed two collector trays of silica aerogel tiles. One tray was dedicated to the capture of gas and dust from comet 81P/Wild 2 at an encounter velocity of 6.1 km/s. The second tray was for the collection of interstellar dust grains with encounter velocities of up to hundreds of km/s. When the STARDUST samples returned to Earth in January, 2006, the success of the cometary collection was visibly demonstrated by the tracks in the aerogel produced by the captured particles. Detailed study of the cometary samples, both in situ in the aerogel, and as extracted grains, has been performed by hundreds of researchers world-wide, using nearly every available analytical technique. The effects of the hyper-velocity capture on the cometary materials vary dramatically, but some grains of both refractory minerals and even organic matter survived capture and can provide new insight into the history of the solar system. The preliminary analysis of the interstellar tray samples is also underway, but is significantly more challenging than that of the cometary samples, because of the higher expected capture velocity, smaller grain size, and low numbers of collected particles.
10:00 AM - BB1.2
The Role of Gravity in the Evolution of Sol-gel-derived Architectures.
Stephen Steiner III 1 , Thomas Coffee 1 , Shuonan Dong 1 , Mark Schneider 1 , Arya Tafvizi Zavareh 1 Show Abstract
1 Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
In most chemical systems, the effects of gravity on the system's chemistry are considered negligible. But there are some chemical systems in which secondary phenomena arising from the presence of an acceleration field (such as buoyancy and convection) can influence the physics and consequently the chemistry of the system. Sol-gel systems are an example of such systems influenced by secondary effects of gravity. Buoyancy-driven fluid flow, for example, has been shown to affect the formation of micro- and nanostructures in a gel in that prior to gelation, buoyancy-induced eddies and sedimentation can significantly perturb sol-gel substructures and such deleterious perturbations may become “frozen” as imperfections in the gel’s structure.[2,3] Furthermore, Smith et al. found that chemistry intended to produce Stöber particles resulted in low-density gels in space, while samples prepared in 1 G remained in suspension. Thus it seems that the effects of an acceleration field somehow influence the evolution of the chemical structure of colloidal silica particles in a way that alters the manor by which they can agglomerate to form a gel (e.g., from condensation of reactive moieties on the particle surfaces).Aerogels are one class of materials that should retain a record of such gravity-sensitive features. We conducted an extensive experiment involving the preparation of 80 silica gels on a parabolic flight aboard ZERO-G Corporation’s B727 aircraft. Gels were prepared in microgravity conditions (<0.01 G), during straight-and-level flight (1 G), and induced-gravity (1.8 G) parabolas. A specially-optimized sol-gel process employing an ethanol-based NaF/NaOH catalyst added to a solution of TMOS in ethanol was used to ensure gelation of samples would occur within the ~16 s time frame of stable microgravity conditions attainable aboard the aircraft yet still maintain high monolithicity and optical transparency. The gels were then purified and supercritically dried from CO2 on the ground where they could be analyzed.In this work, we present the differences in bulk materials properties of aerogels as a function of G-load experienced during gelation. Specific surface area, pore & particle size statistics, and skeletal density are presented and correlated with microstructural observations made with SEM and TEM. Raman spectroscopy is used to understand branching motifs and surface functionality. The effects of Ostwald ripening in aged gels formed in 1 G and microgravity is presented. This work provides insights into the chemical physics underlying particles transitioning from Brownian motion to Newtonian motion as a result of growth and agglomeration. D.A. Noever, Microgravity Sci. Technol. 3 (1994) 14. J.X. Zhu, M. Li, R. Rogers, W. Meyer, R.H. Ottewill, STS-73 Space Shuttle Crew; W.B. Russel, P.M. Chaikin, Nature 387 (1997) 883. D.D. Smith, L. Sibille, R.J. Cronise, A.J. Hunt, S.J. Oldenburg, D. Wolfe, N.J. Halas, Langmuir 16 (2000) 10055.
10:15 AM - BB1.3
Hybrid Aerogel-MLI Insulation System Performance Studies for Cryogenic Storage in Space Applications.
Redouane Begag 1 , Shannon White 1 Show Abstract
1 , Aspen Aerogels, Inc., Northborough, Massachusetts, United States
Long duration storage of large quantities of cryogenic fluids for propulsion, power, and life-support is an essential requirement for missions into space. Efficient and reliable insulation materials are key to the success of these missions. The required insulation material must outperform the current standard multi-layer insulation (MLI) for thermal insulation and provide additional features such as durability, micrometeoroid orbital debris protection, and flexibility all in one single-layer material. Ultra-low density and highly hydrophobic fiber reinforced aerogel material integrated with MLI has the potential to offer a great insulation package which will overcome several issues that the current standard MLI alone suffers from such as: 1) damage during installation, 2) high price, and 3) degradation over time. The hybrid aerogel/MLI solution affords a more reliable alternative because it is robust, and will outperform the MLI in cases of vacuum loss. Low density and highly resilient methyltriethoxysilane (MTES) aerogel will contribute less solid conductivity to the overall heat transfer within the aerogel/MLI system. Sol-gel optimization of low density and low dust MTES aerogels will be presented. Thermal performance of two prototypes of hybrid aerogel/MLI composites and a baseline MLI system (1 inch thick, 90 layers) fabricated by Aerospace Fabrication and Materials (AFM) and tested at cryogenic temperatures under different vacuum level conditions (Cryogenics Test Laboratory, NASA KSC) will also be presented.
BB2: Synthesis I-New & Noteworthy
Monday AM, November 29, 2010
Room 103 (Hynes)
11:00 AM - **BB2.1
Hydrogels and Aerogels from Noble Metal Nanoparticles.
Alexander Eychmueller 1 Show Abstract
1 , TU Dresden, Dresden Germany
We report on the synthesis and characterization of non-supported noble metal aerogels. These exhibit an average density three orders of magnitude lower than the respective materials in their bulk states. Their primary structural units match the size range of single nanoparticles (5–20 nm). No chemical cross-linkers are involved in the self-assembly process. The formation of such noble-metal nanoparticle-based mesoporous monometallic and bimetallic aerogels is an important step towards self-supported monoliths with potentially high catalytically active surfaces. Considering that metal nanoparticles possess very specific optical properties owing to their pronounced surface plasmon resonance, aerogels from metal nanoparticles may also find future applications in nanophotonics, for example, as advanced optical sensors and ultrasensitive detectors.
11:30 AM - BB2.2
Phosphide Aerogels: A New Class of Porous Nanostructures.
Keerthi Senevirathne 1 , Asha Bandara 1 , Ronald Tackett 2 , Parashu Ram Kharel 2 , Gavin Lawes 2 , Autumn Burns 3 , Mark Bussell 3 , Stephanie Brock 1 Show Abstract
1 Chemistry, Wayne State University, Detroit, Michigan, United States, 2 Physics & Astronomy, Wayne State University, Detroit, Michigan, United States, 3 Chemistry, Western Washington University, Bellingham, Washington, United States
The application of sol-gel strategies for assembly of metal oxides, or organic molecules, into porous extended structures has been exploited for the creation of a wide range of aerogels with unique functional attributes. Functionality arises from the intrinsic characteristics of the solid component (governed by composition), the presence of nanoscale interfaces, and the interconnected pore structure. In an effort to tune functionality through composition, we and others have shown that aerogels can be formed from metal chalcogenide building blocks, giving rise to quantum-confined high surface area porous nanostructures with direct bandgaps ranging from the UV into the IR. Our synthetic approach to metal chalcogenide aerogels is based on oxidative gelation of discrete metal chalcogenide nanocrystals followed by standard supercritical (CO2) drying. We have demonstrated the efficacy of this approach for a range of systems, including CdS, CdSe, ZnS, PbS. Recent mechanistic studies have shown that the mechanism of assembly is governed by oxidation of chalcogenide ions on the exposed nanoparticle surfaces, Q2- (Q = S, Se), to particle-bridging per-chalcogenides, Qn2- (n≥2). In the present work, the application of oxidative gelation to formation of metal phosphide aerogels of (1) InP (a direct bandgap semiconductor), (2) MnP (a material with long-range magnetic order) and (3) Ni2P (a hydrodesulfurization catalyst) will be presented. The physical characteristics of these systems will be described and the likely mechanism of self-assembly of phosphide nanoparticles will be discussed and contrasted with the established mechanism for metal chalcogenides.
11:45 AM - BB2.3
Mesoporous Titania Nanoparticle Networks.
Nicola Huesing 1 3 , Oliver Diwald 2 , Stefan Baumann 2 , Michael Elser 2 Show Abstract
1 Materials Chemistry, Paris Lodron University of Salzburg, Salzburg Austria, 3 Inorganic Chemistry, Ulm University, Ulm Germany, 2 Institute of Particle Technology, University Erlangen-Nuremberg, Erlangen Germany
In this work, we describe two independent pathways leading to the formation of mesoporous titania nanoparticle monoliths. In the first approach, a monolithic TiO2 aerogel was employed as a precursor structure and subjected to controlled thermal annealing treatment. For the production of the aerogel an ethylene glycol-modified titanium precursor (EGMT) was used as a starting compound, converted into a gel by sol-gel processing under acidic conditions in the presence of a structure-directing agent. The differences of applying EGMT in comparison to commercially available titanium alkoxides will be discussed. After aging of the wet gels, the pore fluid therein was removed by drying with supercritical CO2 leaving monolithic aerogel bodies behind. For the creation of a mesoporous anatase nanoparticle network, the aerogel was annealed in O2.The second approach starts from agglomerated anatase nanocrystals derived from metal organic chemical vapor deposition in a flow reactor system (CVD-NPN, chemical vapour deposition nanoparticle networks). After thermal treatment in vacuo and in oxygen, the nanoparticles were exposed to a hydration-dehydration cycle, viz. by dispersing the nanocrystals in water under ultrasound exposure and subsequent removal of the liquid by drying. This procedure results in the loss of volume and the formation of solid monoliths, similar to the aerogel structures obtained from the first approach, which were subject to thermal treatment in order to remove surface hydroxyl species.While in the latter approach junctions between particles are only formed in the course of nanoparticle processing, the controlled heat treament of the aerogel is associated with the simultaneous crystallization of nanoparticles and junctions. Both types of networks will be thoroughly compared with respect to their structure and electronic properties.
12:00 PM - BB2.4
A Clean and Effective Supercritical Carbon Dioxide Method for the Host-guest Synthesis and Encapsulation of Photoactive Molecules in Nanoporous Matrices.
Nerea Murillo-Cremaes 1 , Ana Maria Lopez-Periago 1 , Xavier Saurina 2 , Concha Domingo 1 , Anna Roig 1 Show Abstract
1 , ICMAB-CSIC, Bellaterra Spain, 2 Analytical Chemistry, Universitat de Barcelona, Barcelona Spain
The use of supercritical carbon dioxide (scCO2) as a solvent to perform adsorption and impregnation, materials functionalization and chemical reactions has received considerable attention as a viable and sustainable alternative to conventional liquid solvents. A particular case of host-guest synthesis procedure is the encapsulation of chromophores and cationic organic dyes within nanoporous matrices to be used in optical applications such as solid-state dye lasers, aerogel-platform gas sensors or in photocatalytic applications. The present work is concerned with host-guest processes in micro and mesoporous restricted spaces provided by silica aerogels and aluminosilicates. A supercritical carbon dioxide ship-in-bottle approach was used for the synthesis of photoactive molecules (triphenylpyrylium and dimethoxyltrityl cations) inside those nanoporous matrices. Results of the encapsulation ability and photochemical stability for the mentioned cations in transparent mesoporous silica aerogels were compared with those obtained for opaque zeolites. For all the studied matrices, the impregnated cations showed higher hydrolysis stability when encapsulated, than in the crystalline form. The characterization of the resulting materials was based on infrared, ultraviolet-visible and fluorescence spectroscopies, thermogravimetric analysis, surface area nitrogen adsorption and optical microscopy. The hybrid nanocomposites obtained are expected to act as stable and recoverable heterogeneous photocatalysts, having obvious advantages with respect to the more easily degraded organic cations frequently used in homogeneous catalysis.
12:15 PM - BB2.5
Highly Porous Inorganic-organic Gels via Click-modification.
Miriam Keppeler 2 , Nicola Huesing 1 2 Show Abstract
2 Inorganic Chemistry, Ulm University, Ulm Germany, 1 Materials Chemistry, Paris Lodron University of Salzburg, Salzburg Austria
Combining the enormous variation potential of organic groups with the advantages of thermally stable and robust inorganic substrates is particularly attractive to broaden the areas of application of porous matrices e.g. in chromatography or catalysis. As a new method for functionalizing the surface of highly porous silica monoliths, Sharpless Click-chemistry , specifically Huisgen 1,3-dipolar cycloaddition has been used. In the last years Click-chemistry achieved more and more attention in material science. It is a comparatively young “synthesis-philosophy”, whose developers were strongly inspired by reactions taking place in nature. In the present study, hierarchically organized porous silica monoliths were obtained by sol-gel-processing of ethylene glycol-modified silanes. To functionalize the silica-network we used a co-condensation reaction with trialkoxysilanes containing chloromethyl-, and alternatively chloropropyl-groups. Pluronic P123, a non-ionic triblockcopolymer, was used to generate the desired hierarchical porous structure via a true liquid crystal templating mechanism . Subsequently, the chloro moieties were converted to azides by nucleophilic substitution with NaN3. These samples then were reacted Cu(I)-catalyzed with molecules holding terminal acetylenes (phenyl acetylene, carboxylic acids and glycoside derivatives) to get 1,2,3-triazole-rings with different organic groups attached on the silica-surface. The success of these reactions was confirmed by 13C-CPMAS, elemental analyses and IR-ATR spectroscopy. Surprisingly, the large macroscopic monoliths tolerate all reactions steps without destruction. The structure of the silica-gels is not only preserved during all reaction steps, but is even improved on all length scales, which was confirmed by SAXS, N2-sorption analysis, SEM and TEM. Further investigations in terms of the network structure, point out that an improvement with respect to the periodic organization and uniformity of the pores is achieved, which can be related to the interaction with DMF/NaN3 solution that is used for nucleophilic substitution during the second synthesis step. Even pure silica monoliths without chloroalkyl groups show an improvement in their structural features, when they are treated with DMF/NaN3 solution under same conditions.J. F. Moses, A. D. Moorhouse, Chem. Soc. Rev., 2007, 36, 1249-1262D. Brandhuber, N. Hüsing, C. K. Raab, V. Torma, H. Peterlik, J. Mater. Chem., 2005, 15, 1801-1806
12:30 PM - BB2.6
Chiral Binaphthyl Frameworks for Periodic Mesoporous Organosilica Materials.
Jenny Du 1 , Tom Blackburn 1 , Nicholas Mosey 1 , Graham Gibson 1 , Richard Oleschuk 1 , Cathleen Crudden 1 Show Abstract
1 Chemistry, Queen's University, Kingston, Ontario, Canada
Surfactant-templated, porous periodic mesoporous organosilicas (PMOs) have emerged as a unique type of hybrid material in which functional organic groups can be incorporated into the framework of an inorganic matrix through hydrolysis and condensation of organic monomers bearing more than one condensable silyl group. These materials show great potential in a variety of applications such as heterogeneous catalysis, chromatography, and optics due to the tailorability of the monomers and the porous nanostructure.Our group has described the preparation of chiral PMOs by the condensation of chiral monomers. In particular, the combination of chiral and achiral monomers has been shown to result in interesting and useful structural and chemical material properties. For example, chiral monomers have been shown to transfer chirality to achiral bulk monomers in the condensed phase. This behaviour has interesting implications for the preparation of chiral supports for asymmetric catalysis and chiral chromatography.Here, we present the succinct synthesis of a chiral binaphthylene-bridged monomer and its co-condensation with an achiral biphenylene-bridged host monomer using a surfactant templating approach to yield porous powders and monoliths. Chiral induction from the guest to the host species is evaluated by circular dichroism and the differential adsorption of various enantiomeric analytes. For a recent review see: F. Hoffmann et al., Angew. Chem., Int. Ed., 2006, 45, 3216. S. Macquarrie et al., J. Am. Chem. Soc., 2008, 120, 14099.
12:45 PM - BB2.7
Functional and Functionalized Silicate Materials.
Brandy White 1 , Brian Melde 1 , Baochuan Lin 1 , Paul Charles 1 , Anthony Malanoski 1 Show Abstract
1 Center for Bio/Molecular Sc & Eng, Naval Research Laboratory, Washington, District of Columbia, United States
Mesoporous organosilicate materials combine tunable binding characteristics, high surface area, and low materials density with an ordered pore network. Surface modifications provide the potential for incorporation of a variety of functional groups. We have taken advantage of these characteristics for the development of a range of materials to be utilized in various applications. In one approach, porphyrins are incorporated into the materials to provide unique catalytic properties. In these materials, the organosilicate scaffold stabilizes the porphyrin catalyst and facilitates interaction of the catalyst and target. Catalysis can be stimulated through exposure to light or application of an electrical current. The selectivity of the materials can be influenced through choice of organic bridging groups in the organosilicate structure and through selection of the porphyrin component. In addition, a type of molecular imprinting can be applied to provide sites on the pore walls that enhance adsorption selectivity for the target. These materials are directed at the development of self-decontaminating surfaces and coatings. Similar materials characteristics have been utilized in the development of solid-phase extraction materials for use in the pre-concentration of nitroenergetic targets from ground and surface water samples. These materials are being applied to the development of systems for in situ water quality monitoring. Materials can be applied to the encapsulation of proteins and nucleic acids, stabilizing them for wider application of technologies utilizing these reagents. Modifications to the pore surfaces, in this case, are used to incorporate stabilizing agents such as sugars and proteins which should extend shelf-life and reduce storage restrictions. Controlled release/access mechanisms can also be incorporated into the structures.
BB3: Function (Thermal & Mechanical)
Monday PM, November 29, 2010
Room 103 (Hynes)
2:30 PM - **BB3.1
Polymer Crosslinked Aerogels: From Armor to Porous Carbides and Metals.
Nicholas Leventis 1 Show Abstract
1 Chemistry, Missouri University of Science and Technology, Rolla, Missouri, United States
Bulk aerogel properties such as low thermal conductivity and dielectric constants as well as high acoustic impedance come at a high cost: fragility. In polymer crosslinked aerogels the skeletal inorganic nanoparticles (e.g., silica and >30 other metal oxides) are bridged covalently by a thin conformal polymer coating that leaves the mesoporosity almost intact ; in essence, the inorganic framework plays the role of a template for accumulation of polymer. Those 3D core-shell nanostructures are true multifunctional materials with unprecedented mechanical properties that allow applications unthinkable for aerogels before such as ballistic protection. A new recent development is the use of polymer crosslinked aerogels for the pyrolytic synthesis of pseudomorphic porous ceramics through carbothermal processes taking place at the inorganic-core/polymer-shell interface. Thus, a facile synthesis of highly porous monolithic SiC aerogels has been demonstrated from polyacrylonitrile-crosslinked silica aerogels made via surface-initiated polymerization of the monomer on the silica framework .Expanding this line of reasoning to interpenetrating inorganic (MOx) aerogels with a carbonizable resorcinol-formaldehyde (RF) network, a general method has been developed whereas upon pyrolysis, some polymer crosslinked interpenetrating RF-MOx systems smelt to macroporous metal aerogels (case of M: Fe, Co, Ni, Sn, Cu) [3,4] and some others (case of refractories Cr, Ti, Hf) yield macroporous carbides. Native RF-MOx aerogels undergo similar carbothermal reductions at as much as 400 °C higher temperatures than the corresponding crosslinked samples. The effect of compactness on the kinetics of reactions between nanoparticles is studied in detail for its implications in the design of energetic materials. N. Leventis “Three-Dimensional Core-Shell Superstructures: Mechanically Strong Aerogels,” Acc. Chem. Res. 2007, 40, 874-884. N. Leventis et al. “Click Synthesis of Monolithic SiC Aerogels from Polyacrylonitrile-Coated 3D Silica Networks,” Chem. Mater. 2010, 22, 2790-2803. N. Leventis et al. “Smelting in the Age of Nano: Iron Aerogels,” J. Mater. Chem. 2009, 19, 63-65.N. Leventis et al. “One-Pot Synthesis of Interpenetrating Inorganic/Organic Networks of CuO/Resorcinol-Formaldehyde Aerogels: Nanostructured Energetic Materials,” J. Am. Chem. Soc. 2009, 131, 4576-4577.
3:00 PM - BB3.2
Mechanical Properties of Porous Hierachical and Hybrid Materials.
Lena Weigold 1 , Theresa Noisser 1 , Matthias Wiener 1 , Christian Balzer 1 , Gudrun Reichenauer 1 Show Abstract
1 , Bavarian Center for Applied Energy Research, Wuerzburg Germany
The macroscopic mechanical properties are important parameters in terms of tailoring porous functional materials. The mechanical characteristics of a system are affected by its chemical composition, its porosity and the connectivity of the solid phase on the different length scales present. While completely connected foams have been studied with respect to their mechanical properties both experimentally as well as theoretically in very detail, the relationships between structure and mechanical properties in highly porous, only partly interconnected systems are much more complex. For example Ma et al.  showed that in aerogel type systems only a very small part of the solid phase is actually carrying the load applied externally.Hierarchically porous materials as well as hybrid systems that comprise a backbone consisting of two different solid phase components (e.g. organic and inorganic backbone sections) significantly expand the options to tune macroscopically effective mechanical properties.In this study we investigate the impact of the structural arrangement in two phase systems (void and solid phase). Experimental data are derived for different disordered porous model systems such as foams and aerogels. Within the framework of this study we in particular focus on the Young’s modulus and analyze the impact of structures of different length scales on its macroscopic mechanical properties. Here different experimental methods are applied. The length scale with the highest influence on Young’s modulus is identified. In addition, we investigate the effect of defects introduced in these systems by replacing the solid phase locally by a solid with significantly different mechanical properties. The results can be used to find strategies for decoupling of mechanical and thermal properties in porous hybrid materials.Ma, H.S., et al., Mechanical structure-property relationship of aerogels. Journal of Non-Crystalline Solids, 2000. 277(2-3):p. 127-141
3:15 PM - BB3.3
Polyimide-silica Hybrid Aerogels with High Mechanical Strength for Thermal Insulation Applications.
Wenting Dong 1 , Wendell Rhine 1 , Shannon White 1 Show Abstract
1 , Aspen Aerogels, Inc., Northborough, Massachusetts, United States
High performance polyimide has been widely investigated for excellent thermal, mechanical, and electronic properties due to the highly rigid structures. Aspen has developed an approach to prepare polyimide aerogels which have applications as low dielectric constant materials, separation membranes, catalyst carriers and thermal insulators. In this presentation, we will discuss the method Aspen developed to prepare polyimide-silica hybrid aerogel materials with good mechanical strength and low thermal conductivity. The polyimide-silica hybrid aerogel materials were made by a two-step process and the materials were characterized to determine thermal conductivity and compressive strength. Results show that compressive moduli of the polyimide-silica hybrid aerogels increase dramatically with density (power law relationship). Thermal conductivity of the aerogel is dependent on the aging conditions and the density of the hybrid aerogels, with the lowest value achieved so far being ~12 mW/m-K at ambient conditions. The relationship between aerogel density and surface area, thermal stability, porosity and morphology of the nanostructure of the polyimide-silica hybrid aerogels will also be described in the presentation.
3:30 PM - BB3.4
Highly Transparent, Flexible and Superhydrophobic Organically Modified Silica Aerogel Thin Films.
Hulya Budunoglu 1 , Adem Yildirim 1 , Mustafa Guler 1 , Mehmet Bayindir 1 2 Show Abstract
1 UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, Ankara, Bilkent, Turkey, 2 Department of Physics, Bilkent University, Ankara, Bilkent, Turkey
Organically modified silica hybrids produced with soft inorganic methods, have capability of mixing organic and inorganic materials in the same matrix at the nanometer length scale. These materials have properties between those of polymers and glasses meeting the requirements such as, flexibility and stability at atmospheric conditions, which cannot be afforded either by organic polymers or glasses alone. Highly water repellent superhydrophobic surfaces with a water contact angle larger than 150° and a sliding angle lower than 10° have potential applications including self-cleaning materials, stain-resistant textiles and prevention of snow accumulation on antennas, windows and traffic lamps. Lotus leaf is a well known example of such a surface existing in nature, which contains both micrometer and nanometer scaled patches resulting in a well designed superhydrophobic surface with self-cleaning properties. In this work we used alkyltrifunctional methyltrimethoxysilane monomer for preparation of highly transparent, flexible and superhydrophobic ORMOSIL aerogel thin films by a one-pot sol-gel method. The resulting gel surface is covered with non-hydrolysable methyl groups which have dual function: give the films hydrophobic character and prevent collapse of the pores during drying. The solution obtained from gel by dilution can be applied on variety of substrates including glass, wood and plastics at ambient conditions. The coatings were easily obtained without any surface pre-treatments with common thin film deposition methods such as; spin and spray coating. The films exhibit contact angles reaching 179.9° with sliding angles as small as 1°. As a result of organic-inorganic hybrid nature, prepared superhydrophobic films exhibit both flexibility and thermal stability. The films exhibit superhydrophobicity during bending and after repetitive bending-flattening cycles. Further more films preserve superhydrophobic behavior up to 500 °C.
4:15 PM - **BB3.5
Polyimide Aerogels with 3-D Cross-linked Structure.
Mary Ann Meador 1 , Baochau Nguyen 2 , Haiquan Guo 2 Show Abstract
1 , NASA Glenn Research Center, Cleveland, Ohio, United States, 2 , Ohio Aerospace Institute, Cleveland, Ohio, United States
Inflatable decelerators for future entry, descent and landing (EDL) applications require thin, flexible insulation in order for the inflatable to be packed into a compact shape and deployed when needed. To this end, polyimide aerogels have been fabricated in monolithic and thin film forms using several different approaches. Polyamic acid gels are formed by cross-linking with aromatic triamines or amino-phenyl decorated POSS structures. In one approach, chemical imidization is used to cure the polyamic acid gels before supercritical fluid extraction. Alternatively, chemical imidization of amine terminated branched polyamic acid oligomers in solution is carried out, followed by reaction with di-isocyanates to effect gelation in a final room temperature cure. Different backbone chemistries and use of clay or graphene nanoparticles have also been explored to maximize flexibility and durability, and minimize shrinkage in the aerogel films. Mechanical testing, thermal properties and other characterization will also be discussed.
4:45 PM - BB3.6
Preparation of Mechanically Improved Organic Aerogel for Thermal Insulation.
Myung Cho 1 , Sangho Park 1 , Sungwoo Hwang 1 , Kwang Hee Kim 1 Show Abstract
1 Material Center, Samsung Adanced Institute of Technology, Yongin-Si, Kyunggi-Do Korea (the Republic of)
Aerogel, which is an ultrafine porous material having a low density, is applied in various fields, including catalyst supports, thermal insulation materials, noise absorbing materials, and particle accelerators. In particular, silica Aerogel is a super-insulation material that is highly efficient when used for refrigerators, freezers, and thermal reservoirs due to its nano-sized pore structure which resulted in extremely low thermal conductivity. However, silica Aerogel, which is typically prepared in the form of powder or beads, is disadvantageous because it is brittle and thus easily breaks down even under small impact, undesirably exhibiting very low strength. Due to the nature of Aerogel structure, it has very weak mechanical properties and low thermal conductivity. However, even with such low super insulation properties still Aerogel is remained under going research. The main reasons not to commercialization are due to high cost production process and property that difficult to handling or modification. Recently, Aerogel is commercially available in the form of blanket types and this has well structured with impregnated silica Aerogel into blanket. They attempt to develop techniques for preparing Aerogel in the form of an expanding pack or a blanket, resulting from the impregnation of nonwoven fabric with Aerogel powder. Different from previously mentioned silica Aerogel, we have prepared organic/polymeric Aerogel. In our lab, we had developed various structures of organic Aerogel with low thermal conductivity including previously published by Pekala group in 1992. The monolith Aerogel conductivity shows as low as 12.7mW/mK in RF Aerogel , and other newly synthesized organic Aerogel show under 15mW/mK. These organic Aerogel monoliths show higher mechanical property over the silica Aerogel, however, still have weak mechanical properties compare to other insulators that commercially now applying into devices. Now, we have prepare Aerogel with mechanically strong with maintain the low thermal conductivity. The most of our organic composite Aerogel structures achieved compression strength 24MPa at 10% pressured state and around 16mW/mK of thermal conductivity. In this presentation we will discuss more detail technical data and chemistry. Reference:  X. Lu, M. C. Arduini-Schuster, J. Kuhn, O. Nilsson, J. Fricke, and R. W. Pekala, Science, (1992), Vol. 255. no. 5047, pp. 971 - 972
5:00 PM - BB3.7
Polyimide Aerogels: Thermal, Mechanical and Electrical Properties.
Nicholas Zafiropoulos 1 , Shannon White 1 , Wendell Rhine 1 Show Abstract
1 , Aspen Aerogels, Northborough, Massachusetts, United States
Aspen Aerogels has developed high-performance polyimide aerogel insulation material that is lightweight and thermally efficient as well as being structurally sound. Aerogels have fine pores of nanometer dimensions, extremely high porosities (generally between 90 and 99%), and very unique lattice structures. Because of their nanoporous, low-solid structures, there is a complex interrelationship between gas conduction, solid conduction, and radiation components of thermal conduction within aerogel structures making them excellent insulating materials. Polyimide aerogels have been prepared as reinforced and non-reinforced composites with variable final densities. Thermal and mechanical performances have been evaluated across the density range studied and will be presented. Extensive compression and flexural analyses on these samples reveal their superior strength over other aerogel systems, in particular silica and silica/hybrid systems. Thermal conductivity data was obtained under cryogenic and low vacuum conditions that will be discussed. The dielectric constant and loss tangent have also been measured for polyimide aerogels, a linear relationship was observed with respect to the final density of the aerogels. Results of these tests will be presented along with BET porosimetry, TGA/DSC, infrared spectroscopy, and SEM.
5:15 PM - BB3.8
Multifunctional Organic Aerogels.
Wendell Rhine 1 , Nicholas Zafiropoulos 1 , Redouane Begag 1 , Wenting Dong 1 , Irene Melnikova 1 , Shannon White 1 Show Abstract
1 , Aspen Aerogels, Inc., Northborough, Massachusetts, United States
Aerogel insulation materials are one of the few nanotechnologies developed over the last decade that have been successfully transitioned into practical commercial applications. However, most aerogels are still considered to be weak materials and not suitable for structural applications. Aspen Aerogels will present results of our efforts to develop multifunctional aerogel materials that are lightweight, good insulators, and strong enough to be used as the core of sandwich composites. Aspen has developed polyimide aerogel materials that are lightweight, have low thermal conductivities, and have excellent strength to weight ratios. The organic polyimide (rigid) aerogel is strong enough to be used as the insulating core of a sandwich composite to fabricate insulating panels that can also be used for structural applications. The polyimide aerogels can also be converted to carbon aerogels which also have exceptional strengths and relatively low thermal conductivities. The polyimide and carbon aerogels have been characterized to determine their densities, thermal conductivities, surface areas, morphologies and mechanical properties. The results obtained from these investigations will be presented.
5:30 PM - BB3.9
Thermal Transport in Carbon Nanotube Aerogels.
Abhishek Yadav 1 , Huarui Sun 1 , Scott Schiffres 3 , Kyu Kim 2 , Mohammad Islam 2 , Jonathan Malen 3 , Kevin Pipe 1 Show Abstract
1 Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 Chemical Engineering, carnegie mellon university, Pittsburgh, Pennsylvania, United States
Aerogels are ultraporous solids that show promise for a number of applications due to their very low density and amenability to functionalization. Because they are generally made from silica particles or pyrolized organic compounds and have a high density of voids, their thermal conductivities are typically very small (~0.02 W/mK) . Improving the thermal properties of aerogels could enable high-performance heat transfer applications such as heat sinks with ultralow weight.Recent work has examined the fabrication of aerogels using carbon nanotubes (CNTs) . Because the thermal conductivity of an individual multiwall CNT has been measured to be as high as 3000 W/mK , which is similar to that of diamond, such aerogels offer the potential for significantly enhanced heat transfer.Here we study the thermal conductivity of CNT aerogels fabricated by a critical point drying technique . Using a time domain thermoreflectance (TDTR) technique in which an ultrafast laser is used both to generate a pulsed heat source on the surface of the aerogel and to measure its associated thermal decay, we derive the CNT aerogel’s thermal conductivity by fitting a 1D heat transfer model to the measured decay. This measurement is further corroborated by a frequency-domain (3-omega) technique in which a hot wire, immersed in the aerogel, is driven by an AC voltage. The wire acts as both a heat source and a thermometer, and the aerogel’s thermal conductivity is determined by fitting a 1D radial heat transfer model to the amplitude of the temperature response. These measurements confirm substantial improvements in the thermal conductivity of CNT aerogels versus traditional aerogels. J. Fricke et. al, Thin Solid Films 1997, 297, 212-223. M. B. Bryning et. al, Adv. Mater. 2007, 19, 661-664. P. Kim et. al, Phys. Rev. Lett. 2001, 87, 215502-1.
5:45 PM - BB3.10
Mechanical Deformation of Nanoporous Carbons.
Sergei Kucheyev 1 , M. Worsley 1 , T. Baumann 1 , J. Satcher 1 , A. Hamza 1 Show Abstract
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Mechanical properties of porous solids exhibit strongly superlinear dependencies on the material density. Hence, ultralow-density nanoporous materials have notoriously poor mechanical properties. This remains the major factor limiting many potential energy-related applications of these materials. For example, silica aerogels with densities below ~100 mg/cm3 typically have a very low Young’s modulus of ~1 MPa. In this presentation, we will discuss synthesis and mechanical properties of a novel class of robust ultralow-density nanoporous sp2-bonded carbons. These materials, with monolithic densities of ~10 mg/cm3 and above, are made of single-walled carbon nanotubes decorated and interconnected by carbon nanoparticles. Such nanofoams exhibit unprecedented mechanical properties, including high stiffness, fracture toughness, and effective yield stress. Deformation is characterized by strain-dependent elastic properties and viscoelastic energy dissipation. These findings are compared with deformation modes of better studied nanoporous systems such as silica and conventional carbon aerogels.This work was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.
BB4: Poster Session
Monday PM, November 29, 2010
Exhibition Hall D (Hynes)
9:00 PM - BB4.1
Alumina and Nickel-alumina Aerogels Prepared via Rapid Supercritical Extraction for Green Automotive Catalysis Applications.
Nicholas Dunn 1 , Mary Carroll 1 , Ann Anderson 2 Show Abstract
1 Chemistry Department, Union College, Schenectady, New York, United States, 2 Mechanical Engineering Department, Union College, Schenectady, New York, United States
Aerogels are strong candidates for gas-phase catalysis applications due to their high surface area, variable chemical composition and high thermal stability. They can perform several catalytic functions that are currently carried out by noble metal catalysts, such as the conversion of nitrogen oxides into N2 and O2, CO into CO2 and the oxidation of hydrocarbons into CO2 and H2O. These reactions are most frequently performed on automobile exhaust to make it less harmful when released into the atmosphere.Rapid supercritical extraction (RSCE) has proven effective as a general aerogel preparation method that does not require multiple solvent exchanges. Instead, the solvent in the pores of the wet sol-gel matrix is brought to its supercritical state when the sol-gel is heated in a contained mold in a hydraulic press. RSCE preparation of aerogel catalysts reduces the cost, chemical waste and time input required for the synthesis, thereby reducing the environmental impact of the aerogel catalyst compared to both traditional aerogel preparation methods and noble metal catalysts, and making RSCE aerogels attractive alternatives for catalytic applications.Alumina and nickel-alumina gels with varying Ni loads have been synthesized using the proton scavenging epoxide method and RSCE, and characterized by IR and visible absorption as well as BET surface area analysis. The syntheses took as little as a day from starting materials to aerogel, including a soaking step in ethanol to rinse byproducts and unreacted reagents out of the sol-gel network. The IR spectra of both the alumina and nickel-alumina gels are very similar to spectra available in the literature for alumina aerogels, indicating that the RSCE method does not significantly alter the chemistry of the gel relative to traditional extraction methods. Visible absorption spectroscopy performed on the remaining solvent after the nickel-alumina gel synthesis shows very little nickel remaining in solution, indicating that it is either being incorporated into or trapped within the sol-gel network. Preliminary BET analysis shows that the alumina aerogels have a surface area of 410 m2/g, with a pore size distribution from 10-100 nm. Further investigation of surface properties will be performed by more comprehensive BET analysis and by SEM imaging. XRD analysis will be employed to determine whether there are crystalline phases forming within the aerogel due to the high heat and pressure experienced during RSCE.
9:00 PM - BB4.11
Optical Fibre Devices Packaged in Silica Aerogel.
Limin Xiao 1 , Matthew Rollings 1 , Michael Grogan 1 , Richard England 2 , William Wadsworth 1 , Tim Birks 1 Show Abstract
1 Dept. of Physics, University of Bath, Bath United Kingdom, 2 Dept. of Chemical Engineering, University of Bath, Bath United Kingdom
Tapered optical fibres are important components in communication networks, as well as having applications in sensing and as nonlinear light sources. They are made by heating and stretching normal telecom fibres, creating a waist section several centimetres long and (sometimes) smaller than one-micron diameter. Tapering two fibres together into a single waist can cause some or all of the light to couple between the fibres depending on wavelength. This is known as a fused coupler, which is the fibre optic equivalent of a beam splitter and plays a vital role in many applications. Such tapered fibres and devices are small and fragile: they are strongly affected by bending, dust and the refractive index environment.
We have encapsulated tapered fibres and fused couplers in aerogel to provide a lightweight, rigid, protective shell while maintaining the original optical properties. The natural material compatibility with fibre optics, coupled with a refractive index similar to air, makes silica aerogel an ideal host medium for supporting the entire taper waist. We encased tapered fibres using base-catalyzed sol made from tetramethoxysilane: after gelling, the wet gel was aged under methanol for at least one week. Surface hydroxyl terminations were partially replaced by trimethylsilyl ones, resulting in hydrophobic aerogel after carbon dioxide supercritical drying. The aerogel typically shrunk by less than 1% and the resulting density was ~0.2 g/cm3.
We have demonstrated tapers of various sizes embedded in aerogel, with losses less than 1 dB. The smallest tapers, just 800 nm in diameter, were used in sensing acetylene gas that diffuses to the fibre through the aerogel pores, showing its spectral “fingerprint” on a remote detector. Larger-diameter tapered fibres (1 – 2.2 microns) have been used for nonlinearly generating intense white "supercontinuum" light from infrared laser pulses. Unprotected fibres degrade in a few hours, and conventional protective packaging contains glues and other materials more susceptible to harsh operating conditions than silica itself. As an example, the splitting ratio in aerogel encapsulated fused couplers changed by less than 1% even when heated to 250°C.
9:00 PM - BB4.12
Optical Quality Plasmonic Aerogel with Gold Nanoparticles.
Michael Grogan 1 , Susannah Heck 2 , Matthew Rollings 1 , Limin Xiao 1 , Richard England 3 , William Wadsworth 1 , Stefan Maier 2 , Tim Birks 1 Show Abstract
1 Dept. of Physics, University of Bath, Bath United Kingdom, 2 Dept. of Physics, Imperial College, London United Kingdom, 3 Dept. of Chemical Engineering, University of Bath, Bath United Kingdom
Optical-quality "plasmonic" silica aerogel (with applications in Raman spectroscopy, gas sensing and nonlinear light generation) was made in a base-catalysed TMOS process by partly replacing water with an aqueous colloid of gold nanoparticles. Undesirable aggregation of the particles on exposure to methanol (making the gel purple instead of pink) was avoided by delaying addition of the colloid until after silica condensation in the sol had begun. The alcogels were formed in PMMA cuvettes, which were removed by softening in methanol for 2 days to speed up subsequent diffusive water removal, hydrophobic treatment and solvent exchange. Care was taken during supercritical-CO2 drying to control the expanded fluid phases formed from residual methanol in the (windowed) vessel.
Electromagnetic simulations of gold particles surrounded by the average refractive index of the alcogel and aerogel predicted surface plasmon resonance (SPR) wavelengths different in both cases from those measured by spectrometer. Indeed the electric field around each gold nanoparticle decays over a distance of the order of the diameter of the nanoparticle, so only the particle’s immediate environment matters. We conclude that this environment differs from the average, and found a very good match between calculated and measured SPR wavelengths if each particle is assumed to be completely coated in a silica layer comparable in thickness to the silica strands in the aerogel.
9:00 PM - BB4.13
Engineering Porosity into Thermoelectrics: Synthesis and Characterization of PbTe and Bi2Te3 Aerogels.
Shreyashi Ganguly 1 , J. Sharp 2 , P. Gilbert 2 , John White 2 , Stephanie Brock 1 Show Abstract
1 Chemistry, Wayne State University, Detroit, Michigan, United States, 2 , Marlow Industries, Dallas, Texas, United States
The use of modified sol-gel techniques for assembly of PbTe and Bi2Te3 nanoparticles into aerogels, and the resultant physical properties of these materials, is described. The work is motivated by the expectation of enhanced thermoelectric performance through a combination of nanostructuring and incorporation of porosity. Thermoelectrical devices operate by converting thermal energy to electrical energy, or vice versa, governed by the dimensionless figure of merit of the material, ZT = (S2σ/κ)T (S = Seebeck coefficient, σ = electrical conductivity, and κ = thermal conductivity). As such, they provide a method of generating electrical energy from waste heat, or refrigeration without the need for bulky compressors. Because of the interrelationship between S, σ, and κ, augmenting ZT is a balancing act, and the best materials are found to be doped semiconductors with heavy element constituents, like PbTe and Bi2Te3, which have ZT ~ 1. For widespread commercial use, materials with ZT ~ 3 are needed. Improvements in thermoelectric performance can potentially be attained by preparing nanostructured formulations and introducing porosity. The high density-of-states at the Fermi level due to quantum confinement effects is predicted to lead to increases in thermopower (S2σ), whereas the presence of scattering centers, nanoparticle interfaces or pores, is demonstrated to reduce κ. The unique pore structure of aerogels in particular leads to extremely low thermal transport, making these architectures of interest in the design of new thermoelectric material forms. In the present work, the formation of aerogels of PbTe and Bi2Te3 is described for the first time. The synthesis, pore characteristics and morphology of the telluride aerogels will be presented and discussed in light of thermoelectrically relevant properties.
9:00 PM - BB4.15
High Surface Area Carbon Aerogels: Characteristics of Wetting and Porosity.
Margaret Rakowsky 1 2 , Alexander Gash 2 , Theodore Baumann 2 Show Abstract
1 Chemistry, U.S. Air Force Academy, USAF Academy, Colorado, United States, 2 , Lawrence Livermore National Lab, Livermore, California, United States
High surface area carbon aerogels have the potential to provide the skeletal framework for holding catalysts, sensors, or other species for specific applications. The relationship of porosity--macropore, mesopore, or micropore--and how that porosity can be manipulated, to the wetting characteristics of the particular aerogel will be reported. The aerogels being studied are air-dried resorcinol-formaldehyde (RF), both acid-catalyzed and base-catalyzed carbonized resorcinol-formaldehyde (CRF) formed by heating RF under N2, activated carbon aerogel (ACA) formed by heat-treating the sample with gaseous CO2, and O2-activated ACA formed by heating carbonized RF in an air flow. There are several factors, including pore size and intermolecular attractions or repulsions between the aerogel and second phase species, that are important in successfully infiltrating the aerogel. In the experiments with these materials, after infiltration with a salt (saturated aqueous solution, ionic liquid, or other variation), the changes in the aerogel in mass %, surface area, morphology, and thermal behavior were determined. For example, of these five types, the one with the highest surface area as determined by BET (Brunauer-Emmett-Teller method) is the acid-catalyzed ACA. Yet the aerogel which appears to wet easier—that is, it is not repelled by the solution—is the O2-activated ACA—with about 1/3 of the surface area of the acid-catalyzed ACA aerogels. The correlation between amount of surface area and the increase in mass due to infiltration, thermal behavior, and morphology will be reported.
9:00 PM - BB4.16
Investigation and Study of a Transparent and Translucent Facade System, with a Minimum Thickness, a Free Form Design, and a High Thermal Insulation Value, to be used in to Architectural Development.
Luis Alonso 1 Show Abstract
1 Department of Building and Architectural Technology from UPM, Architect and PhD, Madrid, Madrid, Spain
This research is aimed at the study of alternatives for the transparent and translucent facades systems, looking for having a better thermal insulation, and a thinner section than the in the commercial systems, and also would allow a free-form design. Emphasize the use of Monolithic Silica Aerogel as a thermal insulation and the interstitial vacuum camera system as part of these improvement alternatives. Most of the commercial products are composed of Granular Silica Aerogel (Nanogel), instead of Monolithic Aerogel. The Nanogel is used as fill material into existing panels on the market (Encapsulated of Nanogel), like polycarbonates, polymers reinforced or double glazing.Of all the commercial panel systems that use Nanogel as a thermal insulation, stresses the VIP OKAGEL panel of the OKALUX brand, is the first panel of this type that the market is trying to commercialize, but it's still at the prototype stage. This panel consists in to a double glazing in whose chamber, filled with granules Aerogel, a vacuum is created, generating a translucent panel. Outside of the commercial products, there are several prototypes and among which two have achieved high levels of transparency and a very high thermal isolation value. The first (Zae Bayern) consists of a double glazing with vacuum chamber and splitters of Aerogel in the chamber to prevent the buckling of the glazing panel. The second (HILIT+) is a double glazing with a vacuum chamber which has a monolithic block of Aerogel inside.After a comparison, this study has determined that the panels that best outcome commercial offer are the VIP (Double glazing with air chamber and insulation vacuum in the chamber), but because there still is a prototype, are still being tested in real conditions.Additionally, this work opens a new experimental way, through the theoretical proposition of a prototype that would take the good performance of the panels in the market and evolve to incorporate new design of panels using Monolithic Aerogel encapsulated into a chamber vacuum within fiber reinforced polyester elements. These panels systems will generate semi-monocoque elements.
9:00 PM - BB4.17
Development of Non-compacting Aerogel Insulation for Cryogenic Propellant Storage.
Kiranmayi Deshpande 1 , Wendell Rhine 1 , Shannon White 1 Show Abstract
1 , Aspen Aerogels Inc, Northborough, Massachusetts, United States
NASA’s planned exploration of space requires that new technologies be developed for long term cryogenic propellant storage. The Altair (Lunar Lander) ascent stage requires LO2 and LCH4 storage durations of up to 14 days in LEO and up to an additional 210 days on the lunar surface. Long term storage (224 days) of LO2 cryogenic propellant on the lunar surface is required to support space power systems, spaceports, spacesuits, lunar habitation systems, robotics, and in situ propellant systems. Long term storage (6 months) of LO2/ LH2/ LCH4 cryogenic propellants on the surface of the Earth with minimal propellant loss is required to support launch site ground operations. Currently, Aspen Aerogels Inc. is developing non-compacting aerogel insulation for cryotanks used on launch vehicles, for in-space cryogenic fuel storage, as well as for terrestrial cryogenic storage applications. The desired advanced insulation material should be non-compacting (> 5 psi compressive strength), low density (< 0.05 g/cc), and have a low thermal conductivity (< 28 mW/m■K). Low density organic-inorganic hybrid aerogels with excellent thermal insulation properties and compressive strengths have been prepared by co-gelling tetraethylorthosilicate with bis(trialkoxysilane)alkyl moieties as bridging groups. Incorporation of alkyl groups develops inherent hydrophobicity in the material which is needed for cryogenic applications. Aerogel materials have also been reinforced with various fibers to impart flexibility. The aerogel hybrid materials prepared have been characterized to determine morphology by SEM, BET surface area, thermal conductivities, thermal stability (TGA) and compressive strength. The relationships between density, crosslinking groups and mechanical properties will be presented.
9:00 PM - BB4.2
Design of Highly Porous FeCo(Ni)–SiO2 Nanocomposite Aerogels for Catalyst Applications.
Danilo Loche 1 , Anna Corrias 1 , Maria Casula 1 , Andrea Falqui 1 2 , Sergio Marras 2 , Zoltan Konya 3 , Daniele Gozzi 4 , Alessandro Latini 4 , Pietro Moggi 5 Show Abstract
1 Dipartimento di Scienze Chimiche, Università di Cagliari, Monserrato, Cagliari, Italy, 2 , Istituto Italiano di Tecnologia, Genova Italy, 3 Applied and Environmental Chemistry Department, University of Szeged, Szeged Hungary, 4 Dipartimento di Chimica, Università degli Studi di Roma "La Sapienza", Roma Italy, 5 Dipartimento di Chimica Organica e Industriale, Università di Parma, Parma Italy
In this work, we present the sol-gel synthesis and characterization of highly porous FeCo(Ni) aerogel catalysts constituted of alloy nanoparticles dispersed into a highly porous amorphous silica matrix.The samples were synthesized thanks to the development and optimization of a new acid-base catalyzed two-step sol-gel method, by co-gelation of the precursors of the dispersed and of the matrix phases. Urea, a base gradually and slowly releasing OH- group, was used as base catalyst in the second step. Supercritical drying is followed by thermal treatments, including reduction, to obtain alloy nanoparticles as dispersed phase, with different loadings and different metals ratio.Characterization of the aerogels was performed by X-Ray powder diffraction, transmission electron microscopy and N2 physisorption at 77 K. The aerogel matrix show very large mesopores. Excluding the Co rich samples, the XRD pattern and TEM images of the aerogels confirm the formation of nanocrystalline FeCo alloy (the amount of Ni being very low) which are well dispersed within the matrix. The average size of the nanoparticles grows up to about 10 nm in the aerogel with the largest Fe+Co loading.These nanocomposites were tested as catalysts in the production of Multi Wall Carbon Nanotubes (MWCNTs) by Catalytic Chemical Vapour Deposition (CCVD). The influence of catalyst composition and CCVD parameters on the quantity, quality, shape and dimension of the MWCNTs was investigated. The results show that the catalysts are very effective in producing very high yield of high purity MWCNTs whose diameters and average number of walls was dictated by the catalyst nanoparticle size.Besides, the same nanocomposites were tested as catalyst in the liquid fuels production by Fischer-Tropsch synthesis. The preliminary results show an interesting high selectivity towards light hydrocarbon fractions.The Regione Autonoma della Sardegna is gratefully acknowledged for financial support through POR Sardegna FSE 2007-2013, L.R.7/2007 “Promozione della ricerca scientifica e dell’innovazione tecnologica in Sardegna”.
9:00 PM - BB4.20
Synthesis of Various Organic Aerogels and Hybrid Aerogels for Thermal Insulation.
Sungwoo Hwang 1 , Sangho Park 1 , Kwang Hee Kim 1 , Myung D. Cho 1 Show Abstract
1 Materials Research Center, Samsung Advanced Institue of Technology, Samsung Electronics Co., LTD, Yongin Korea (the Republic of)
Aerogel is a unique porous material consisting of interconnected nanometer-sized colloidal or polymeric particles with 3-dimensional mesoporous network structure.The objective of this study is to demonstrate the feasibility of a time-efficient way, the probability as a thermal superinsulator, and to highlight correlations between sol-gel parameters and these newly developed nanostructured polymer-based organic aerogels.In this work, some of crack-free monolithic organic aerogels with various compositions have been developed. Organic polymer-base aerogels such as typical RF aerogel and their new derivatives were synthesized by connecting building blocks via cross-linking with strong covalent bonding. A new class of aerogels prepared with hydrophobic acrylamide derivatives via a radical polymerization, benzoxazine-based polymeric aerogels and their hybrids, and polyimide based aerogels and their hybrids were also developed. The physicochemical properties such as skeletal/bulk densities, shrinkage during supercritical drying and porous characteristics were measured and the effective thermal conductivities of resulting aerogels measured by heat-flow method were also discussed in detail. These organic aerogel monoliths show excellent mesoporous features with low thermal conductivity and a relatively higher mechanical strength or even flexibility without further operation such as surface modification.
9:00 PM - BB4.21
Characterization and Optimization of Fluid Flow for High Biot Number Systems.
Jason Prapas 1 , Marc Hodes 1 , Vincent Manno 1 , Douglas Matson 1 , Luisa Chiesa 1 , Richard Wlezien 1 Show Abstract
1 Mechanical Engineering, Tufts University, Medford, Massachusetts, United States
Convective heat transfer is investigated for flow between slabs of porous media separated by a mechanical structure (a separator). We analyze the flow between these layers and through the separator and develop a simplified analytical model to describe the system. This model depends on the relative thermal resistance due to convection from the fluid flow and conduction into the porous slab. This can be cast as a Biot number and drives the design of optimized separators. An experimental apparatus was designed and fabricated to quantitatively assess pressure drop through the system using different separator strategies and we compare experimental results to the model. Unobstructed channels are shown to behave like a classical Poiseuille flow, in close agreement with the simplest analytical model. Channels with separators can be modeled with a two-term equation: a baseline Poiseuille term and a form drag term. A variety of separator designs are compared and their effect on overall performance is discussed. Existing designs developed for spacing the layers of membrane filters are shown not to work well for high Biot number. We also discuss strategies for an optimized overall approach.
9:00 PM - BB4.22
Synthesis of New Flexible Aerogels from Di- and Trifunctional Organosilanes via Ambient Pressure Drying.
Gen Hayase 1 , Kazuyoshi Kanamori 1 , Kazuki Nakanishi 1 , Teiichi Hanada 1 Show Abstract
1 Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto Japan
Silica aerogels are still far from applications regardless of the well-known excellent properties such as low thermal conductivity. There has been a lot of research to improve the mechanical properties of aerogels and to obtain without supercritical drying while maintaining the excellent properties. We have reported that transparent organic-inorganic hybrid aerogels with improved mechanical properties are obtained solely from organoalkoxysilane when the starting compositions and synthetic conditions are adequately controlled. These aerogels are made from methyltrimethoxysilane (MTMS) as precursor and surfactant n-hexadecyltrimethylammonium chloride (CTAC) which is added to control phase separation, by a modified acid/base two-step sol-gel reaction utilizing acetic acid and urea as catalysts.Up to now, little is known about the relationship between starting compositions and properties of these aerogels. The roles of surfactant and urea, in particular, should be clarified. In addition, the MTMS-derived aerogels are already excellent in compressive mechanical properties; however, highly flexible aerogels with elastic deformability against tensile and shear stresses will make the aerogel handling much easier and will open the way to various applications. For this purpose, we used a mixture of MTMS and dimethyldimethoxysilane (DMDMS) to further lower the cross-linking density and to introduce more hydrophobic methyl groups.First, we investigated the relationship between starting compositions and physical properties in detail. Bulk density, visible light transmittance (at 550 nm), compressive mechanical properties such as Young's modulus are investigated. Concentration of CTAC is found to largely affect the properties of aerogels. Too high concentration of CTAC made aerogels weaker and have lower light transmittance because CTAC to some extent hindered the polycondensation of MTMS and lowered the crosslinking density. Conversely, too low concentration of CTAC did not effectively suppress macroscopic phase separation, resulting in the lower light transmittance. Concentration of urea influences the polycondensation behavior, resulting in changes in light transmittance.Next, to make the aerogels flexible, we used a mixture of MTMS and DMDMS instead of a single precursor MTMS in the above-mentioned sol-gel system containing CTAC and urea. The obtained opaque aerogel has high flexibility enough to endure the surface tension during a drying process at ambient temperature and pressure, and to withstand against the tensile stress exerted during a bending test. We systematically investigated variations of pore structures and mechanical properties of this material with changing starting compositions and synthesis conditions. Only a few reports have been made for the preparation of low density and bendable aerogels, and we believe that this material would be a new candidate for various applications such as thermal and acoustic insulators.
9:00 PM - BB4.24
Nano-scale Creep Compliance of Hybrid Aerogels.
Nicolas de la Rosa-Fox 1 , Victor Morales-Florez 2 , Manuel Pinero 3 , Luis Esquivias 4 Show Abstract
1 Fisica Materia Condensada, Universidad de Cadiz, Puerto Real (CADIZ) Spain, 2 ICMSE, CSIC-US, Sevilla Spain, 3 Fisica Aplicada, Universidad de Cadiz, Puerto Real (CADIZ) Spain, 4 Fisica Materia Condensada-ICMSE, Universidad de Sevilla, Sevilla Spain
Hybrid organic/inorganic aerogels are nanostructured materials composed by an entangled network of silica particles surrounded by the polymeric chains. Depending on the relative organic content, the mechanical behaviour changes drastically, tuning from a brittle solid (pure SiO2 aerogel) to an elastomeric solid (Ormosil aerogel). The copolymerization is accomplished by the application of high power ultrasounds (≈1 kJ cm-3) to the precursor liquid mixtures using the classical sol-gel method. The specific organic precursor was selected in the silanol-terminated polymer family and the inorganic in the silicon alkoxide one. Ultrasounds, by means of the acoustic cavitation process, influence the formation of a very fine distribution of silica particles and avoid the cyclidation of the polymer chain, thus favouring the copolymerization with the inorganic particles and leading to the formation of a highly porous and rubbery-like solid aerogel.Creep test were carried out in a Nanotest automatic device from MicroMaterials Ltd. (UK) equipped with a diamond indenter with Berkovich pyramidal tip (100 nm diameter). Load–depth hysteresis curves were recorded in order to calculate the mechanical parameters. Creep data were collected along 3600 s for several surface sites and different loads; measurements were made in a closed cabinet with controlled humidity 40% and temperature of 28 degree C. The tests were run under different loads in the range from 1 to 50 mN, using load rates from 0.1 to 5 mN/s. Creep compliance curves, corresponding to the time-dependent depth response to a step load are imprint site dependent, discerning pore, soft and stiff sites. In all cases, an instantaneous elastic deformation is apparent. For higher times, depending on the imprint sites, elastic deformation and Newtonian flow produce the up and fall of the creep compliance value. Isochronous stress-strain diagrams show a two-regime trend, linear in the low load range and parabolic behaviour for the higher one, which seems to indicate the nonlinear viscoelasticity of these hybrid aerogels. The mechanical response to creep test of several organic precursors with different concentration inside the inorganic matrix will be presented in this study.
9:00 PM - BB4.25
Soliton Wave Induced Controlled Assembly of Sol-gel Derived Mesostructural Films.
Aaron Kessman 2 , Paul Richter 1 , Darran Cairns 2 Show Abstract
2 , West Virginia University, Morgantown, West Virginia, United States, 1 , BTU International, Chelmsford, Massachusetts, United States
This work describes a novel process for producing sol-gel silica films with aligned and spaced mesostructural features that are similar to those made by surfactant templating. In this process, an alkoxysilicate sol is prepared with a certain portion of the sol flocculated in-situ during the sol hydrolysis to provide seed particles for mesostructure formation. A soliton wave assisted coating process is then used to provide a continuous matrix coating with repeatable assembly of mesostructed, 3-dimensional features. A study of optical and mechanical properties of these coatings is included.
9:00 PM - BB4.26
Characterization of Titania-silica Aerogels Fabricated Using Rapid Supercritical Extraction.
Lauren Brown 1 , Ann Anderson 1 , Mary Carroll 2 Show Abstract
1 Mechanical Engineering Department, Union College, Schenectady, New York, United States, 2 Chemistry Department, Union College, Schenectady, New York, United States
Titania-silica (Ti-Si) aerogels can be used for photocatalytic oxidation of volatile organic compounds to clean up pollutants in air and water. However, methods for fabricating these aerogels can be complicated and time consuming. In this work we describe the use of a rapid supercritical extraction technique (RSCE) for making Ti-Si aerogels in as little as 8 hours. The RSCE technique uses a metal mold and a four-step hydraulic hot press procedure to bring the chemical precursors to a supercritical state and control the supercritical fluid release process. Two different recipes for Ti-Si aerogels were employed using the RSCE method. In the first technique, which took approximately 1 week of processing time, a silica wet gel was prepared using tetramethylorthosilicate (TMOS), water (H2O), methanol (MeOH) and ammonia (NH3) in a molar ratio of TMOS:H2O:MeOH:NH3 of 1:4.1:7.2:0.01 and allowed to age for 48 hrs. The wet gel was soaked in isopropanol for 24 hours, then bathed in a TPAA solution (titania isopropoxide (TIP) and acetylacetone) for 24-48 hours and afterward bathed again in isopropanol. The wet gel was then processed using a 7 hour RSCE technique to fabricate an aerogel. This process yielded transparent aerogels with high surface areas (600-650 m2/g) and low density (0.14-0.18 g/mL). The density was found to increase with increased soaking time in the TPAA. The second recipe, which took 8 to 24 hours to complete, combined tetraethylorthosilicate (TEOS), ethanol (EtOH), H2O, and hydrochloric acid (HCl) with TIP in a molar ratio of TEOS: EtOH: H2O:HCl:TIP of 0.02:0.51:0.08:0.274x10-3:0.0208. In some cases the precursor chemicals were allowed to gel for 18 hours before processing in a 7 hour RSCE technique, in others the chemicals were poured directly into the metal mold and processed in a 7-13 hr RSCE. The resulting aerogels were opaque and less monolithic but had high surface areas (400-700 m2/g). The surface morphology of the samples was evaluated using SEM. We employed FTIR spectroscopy to evaluate the chemical bonding within the aerogel matrix.
9:00 PM - BB4.27
Modeling and Measurements of Supercritical CO2-based Alcogel Drying Rates.
Justin Griffin 1 , Martin Cleary 1 , Drew Mills 1 , Douglas Matson 1 , Luisa Chiesa 1 , Richard Wlezien 1 , Vincent Manno 1 , Marc Hodes 1 Show Abstract
1 Mechanical Engineering, Tufts University, Medford, Massachusetts, United States
A time-consuming step in aerogel production is the supercritical CO2 drying process. Improved understanding of the process is necessary to accelerate aerogel production rates and thus make aerogels more economically viable. A model has been formulated in which the transport of supercritical carbon dioxide and ethanol is analyzed within an idealized single pore of silica alcogel during drying. The drying process was found to be diffusion dominated. Furthermore, this model elucidates the importance of accurately determining the binary diffusion coefficient in the ethanol-CO2 system, specifically its dependence on system composition. A second macro-scale model addresses drying in a sheet of aerogel as CO2 flows through a narrow gap adjacent to it. This model quantifies the importance of ethanol buildup in the narrow gap on the transient drying process, which was shown to be negligible in the parametric range examined. A supercritical extraction rig with a one-liter pressure vessel was built to allow experimental validation of the single pore and macro scale models. An infrared concentration sensor at the outlet of the pressure vessel allowed the ethanol concentration in the effluent supercritical CO2-ethanol mixture to be measured in real time during the extraction process. Two different alcogel geometries were developed to match the differing boundary conditions in each model. First, a cylindrical geometry was fabricated to validate the single pore model, which assumes that there is no ethanol build-up at the mouth of the pore. Second, an annular parallel plate-type geometry was implemented, which allowed the macro-scale model to be validated. A parametric analysis for both configurations was performed as the temperature, pressure, and mass flow rate of supercritical CO2 were varied.
9:00 PM - BB4.28
Fabrication and Analysis of TEOS-based Aerogels Prepared via Rapid Supercritical Extraction.
Suzanne Estok 1 , Thomas Hughes 1 2 , Mary Carroll 1 , Ann Anderson 2 Show Abstract
1 Chemistry Department, Union College, Schenectady, New York, United States, 2 Mechanical Engineering Department, Union College, Schenectady, New York, United States
The low density and excellent insulating properties of translucent aerogels render them particularly attractive materials for many commercial applications such as window and skylight insulation and specialty windows. In this poster, we describe aerogels prepared using the silica precursor tetraethylorthosilicate (TEOS) and a rapid supercritical extraction (RSCE) method. Fabricating TEOS-based aerogels with an RSCE method offers some distinct advantages. The main advantage is the relative simplicity of the RSCE approach: liquid precursors are mixed and poured into a mold in a hydraulic hot-press, where gelation, aging and extraction of liquid from the pores occur. Much of the previous work on silica aerogels by our group has focused on the use of TMOS-based precursor mixtures. Reaction of TEOS to form sol gels yields ethanol as a byproduct. A process that releases ethanol, rather than methanol (as in the TMOS-based aerogels) may be more appealing for commercial applications, involving scale-up of the process. We have successfully fabricated silica aerogels via a seven-hour RSCE process, using a precursor mixture of TEOS, ethanol, and water (molar ratio of 1.0:4.9:6.3), with oxalic acid to catalyze hydrolysis, followed by aqueous ammonia to catalyze the polycondensation reactions. The resulting monolithic RSCE aerogels have average bulk density of ~0.088 g/cm3, average pore diameter ca. 40 nm, average BET surface areas up to 320 m2/g, and skeletal density of 2.04 g/cm3. These aerogels are opaque, which renders them less attractive for certain applications. Consequently, we are ascertaining the precursor recipe and hot-press processing parameters required to make high quality, monolithic, translucent TEOS-based silica aerogels via the RSCE process. With regard to the precursor recipe, we are varying catalyst concentration, molar ratio of water/ethanol, and time allowed for hydrolysis prior to adding the base catalyst. We employ a barrage of characterization methods including density, thermal conductivity, and optical transmission in the visible region, BET surface area and BJH pore size distribution. In addition, we investigate the surface morphology of the resulting aerogels using SEM.
9:00 PM - BB4.3
Dye Sensitized Solar Cells Using Uniform TiO2/CNT Gel.
Sungwoo Yang 1 Show Abstract
1 Chemistry, Duke University, Durham, North Carolina, United States
We fabricated Dye-sensitized solar cells (DSSCs) using uniform mixture of titanium dioxide and carbon nanotubes (CNTs). The high conductivity of CNTs was expected to improve the electron transport rate and extend the electron lifetime in TiO2 electrode resulting in higher efficiency of DSSCs. In addition, the mechanical strength of TiO2 film was also expected to increase with CNT network. We used the sol-gel method to make uniform mixture of TiO2/CNT composite. There were already several publications before reporting that CNTs’ improvement on DSSCs performance. However, uniform of TiO2/CNT composite in this project enables us to exceeds previous other’s result in DSSCs efficiency. After the uniform TiO2/CNT gel film was successfully synthesized, we use this film to fabricate the DSSCs. Peptization of TiO2 was a critical process to fabricate an uniform TiO2 film which decides DSSCs’ performance by optimizing TiO2 film’s porosity, thickness and aggregated TiO2 particle’s diameter. In addition, hydrothermal treatment for TiO2 gel was used to control anatase/rutile ratio and TiO2 nanoparticle size. So far, adding CNTs shows about 15% increase of solar cells efficiency compared with the one without CNTs addition. We believe that this improvement is mainly because of the faster electron transport through CNTs nextwork resulting in increase of the short circuit current while the open circuit voltage almost remains as TiO2 gel without CNTs addition. In near future, we are expecting further improvement on DSSCs efficiency by using the TiO2/CNT composite.
9:00 PM - BB4.30
An Easy Method for Synthesizing Carbon Gel Milispheres Based on Microwave-assisted Gelation.
Ana Arenillas 1 , J.Angel Menendez 1 , Esther Calvo 1 , Emilio Juarez-Perez 1 , Esteban Ruisanchez 1 Show Abstract
1 , INCAR-CSIC, Oviedo Spain
Carbon gel spheres ranging from 0.5 to 4 mm were synthesized by simply pouring a resorcinol/formaldehyde gel, at the precise gelation point, into a stirred bath of hot glycerine. The novelty of this method consist in carrying out the gelation process under microwave heating at a constant temperature of 85C and controlling the exact point of gelation following the energy consumed by the microwave oven. At this point, the gelation process is stopped for a while in order to pure the incipient gel into a glycerine bath, which is being stirred at the same temperature, i.e., 85C. Thus, after a few minutes spheres of the organic gel start to coalesce. Interestingly, the diameter of these spheres can be controlled adjusting the stirring speed. After completing the gelation process in the stirred bath, the spheres are taken apart, washed with acetone, dried in a stove and carbonized at 800C. The resulting spheres of the carbon gel present good mechanical properties and well developed porosity in the rage of micro-mesopores. Moreover, the pore size distribution of these gels can by tailored by adjusting the pH of the resorcinol-formaldehyde precursor. It is believed that these carbon gel spheres can be used in a number of applications like catalyst supports, absorbents, carbon molecular sieves, etc.
9:00 PM - BB4.31
Synthesis of Resorcinol Formaldehyde Aerogel Using Photo-acid Generators for Inertial Confinement Fusion Experiments.
Kyle Saito 1 , Reny Paguio 1 , Jared Hund 1 , Rene Jimenez 1 Show Abstract
1 IFT, General Atomics, San Diego, California, United States
Typically, the synthesis of Resorcinol Formaldehyde (R/F) Aerogels consists of a 2-step polycondensation reaction driven by a base followed by an acid catalyst developed by Pekala et al. Since the acid catalyst in the 2-step polycondensation reaction controls the gelation time, we are able to replace the acid catalyst with a non-ionic photo-acid generator and dramatically decrease the gelation time to a couple minutes at room temperature using a UV light source. Not only is the reaction rate fast, but the liquid precursor is stable for several hours prior to UV exposure. After drying, the resulting aerogel porosity is not changed significantly from the standard process. Scanning electron microscopy and porosimetry will be used to compare the similarities between the original and modified R/F pore structures. This paper will discuss themodifications made to the traditional R/F formulation, as well as the benefits of a fast gelation time for aerogel casting applications such as thin films, cylinders, and solid and hollow microspheres. The modified R/F formulation process also opens up the possibility of directly patterning aerogels into complex shapes on a surface using a photo-mask.
9:00 PM - BB4.4
Self-assembled Inorganic-organic Hybrid Nanoarchitectures for PV Applications.
Richard Brotzman 1 , Adam Nye 1 Show Abstract
1 Energy Systems, Argonne National Laboratory, Argonne, Illinois, United States
Hybrid composites, which are composed of organic and inorganic semiconductors and ceramics, can be fabricated from a broad range of materials and structured at a mesoscopic, nanoscopic, and molecular level. Correctly matching the materials and structure can deliver exceptional electronic properties that can be exploited in a broad range of applications.However, the ability to fabricate hybrid composites from liquid precursors by directed self-assembly not only yields interesting material architectures, but also offers the promise of processing these architectures inexpensively using roll-to-roll techniques.The self-assembly of two dissimilar materials into bicontinuous morphologies gives rise to the formation of extremely high internal area material junctions with periodicities on the 10 nm length scale. Functional materials may be introduced into the self-assemblies to yield energy harvesting materials for solar cell applications.Hybrid composites, comprised of n-type inorganic semiconductors, p-type organic semiconductors, and ceramic absorbers, and methods of directed self-assembly will be detailed. Composition-structure-processing correlations will be discussed and functional behavior will be compared with current photovoltaic energy harvesting materials.
9:00 PM - BB4.5
Cation Exchange Reactions in ZnS Gels for Heavy Metal Sequestration and Generation of Novel Materials.
Irina Pala 1 , Stephanie Brock 1 Show Abstract
1 Chemistry, Wayne State University, Detroit, Michigan, United States
Semiconducting metal chalcogenide aerogels benefit from the constructive intertwining of the properties of two classes of materials. On the one hand, the high porosity and the easily accessible particle surfaces of aerogels make them good candidates for applications as catalysts and sensing materials. At the same time, they consist of a 3D network of nanoparticles, interconnected without the use of any organic linker, which maintains the quantum confined opto-electronic properties of the building blocks. For example, the ability to access bandgaps that span from the UV into the IR, resulting in a favorable overlap with the solar spectrum, is beneficial for potential applications in photovoltaic devices or photocatalysis. The synthesis of metal chalcogenide aerogels is achieved by a two-step process: nanoparticle synthesis and oxidation induced assembly. This has been successfully applied to a range of materials, among them CdSe, CdS, PbS and ZnS. However, this approach requires the optimization of both the nanoparticle synthesis and the gelation conditions, which are not trivial and might not be easily tailored for certain chemistries. A larger variety of materials could be accessed by circumventing these tedious processes, enabling exploitation of the dual void/ particle interconnected network in other applications. Accordingly, we have adapted ion-exchange routes as a means to access new phases, successfully exploited for formation of Ag2Se, PbSe and CuSe from CdSe gels.In order to further expand the range of phases accessed, and because, the ability to uptake ions via exchange could potentially be useful for sequestration of heavy metal ions, in which case the host lattice should originally have a cation of lower toxicity and higher solubility, we have turned our attention to cation exchange of ZnS gels. In this presentation, recent work aimed at accessing new aerogel chemistries from exchange of ZnS gels will be described and the potential application of these reactions to processes like heavy-metal removal from water, discussed.Q. Yao, I. U. Arachchige, S. L. Brock, J.Am.Chem.Soc. 2009, 131, 2800.
9:00 PM - BB4.6
Synthesis and Characterization of New Zn/Sn/S Aerogel by Metathesis Reaction.
Youngtak Oh 1 Show Abstract
1 Chemistry, Northwestern University, Evanston, Illinois, United States
Porous zinc tin sulfide materials in the form of aerogels (belonging to the class of chalcogels) were synthesized by metathesis reactions between zinc salts and thiostannate cluster salts of [SnS4]4-, [Sn2S6]4-, [Sn4S10]4- units. Self-assembly reaction of the Zn2+ linker and anionic thiol stannate clusters in formamide solution yielded a polymeric aggregation of nanoparticles with interconnected solvent and counter ions. Supercritical drying and solvent exchange resulted in a new family of random porous inorganic Zn/Sn/S aerogels with high surface areas and high pore volumes. The bandgap energies of these materials range from 2.8-3.2eV. The zinc-tin chalcogenide aerogels also possess high affinities toward soft heavy metals and strong electron-accepting molecule. The properties and physical characterization of these materials will be presented.
9:00 PM - BB4.7
Silica/Carbon Hybrid Aerogels for Electrochemical Sensors.
M. Hamza Ikram 1 2 , Marti Gich 2 , Anna Roig 2 , Andreu Llobera 3 , Ester Carregal 3 , Cesar Fernandez-Sanchez 3 Show Abstract
1 , Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi Pakistan, 2 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 3 , Institut de Microelectrònica de Barcelona (CNM-IMB-CSIC), Bellaterra Spain
We present silica/carbon microstructured hybrid aerogels which are electrically conductive and mechanically robust, as well as a protocol to enhance the adhesion to Si wafers. These properties, together with a controlled density and pore structure, make of the proposed aerogels suitable candidates for their implementation as electrodes in electrochemical sensors. Moreover, the sol-gel technique allows the patterning of high-aspect ratio structures in Si substrates by micromolding or imprinting techniques .  C. Fernández-Sánchez et al. Chem. Mater. 20 (2008) 2262.
9:00 PM - BB4.8
Organo-modified Silica Aerogels and Implications for Material Hydrophobicity and Mechanical Properties.
Laura Martin 1 2 , Josep Oriol Osso 3 , Susagna Ricart 1 , Olga Garcia 4 , Anna Roig 1 Show Abstract
1 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 2 Department of Chemistry, Universitat Autònoma de Barcelona, Bellaterra Spain, 3 , MATGAS 2000 A.I.E., Bellaterra Spain, 4 , Instituto de Ciencia y Tecnología de Polímeros (CSIC), Madrid Spain
Silica aerogels are extremely sensitivity to moisture and, in general, they present poor mechanical properties. Those shortcomings reduce their potentiality for technological applications. To overcome that a number of strategies have been investigated. Here, we will report on an organo-modified silica gel resulting from condensing tetramethoxysilane (TMOS) with trimethoxymethylsilane (TRIMOS). The concentration of organic part was increased until the gels lost their transparency (60 % TRIMOS). The wet gels were dried either at supercritical conditions of methanol or at supercritical conditions of the carbon dioxide. Such hybrids were found to be highly hydrophobic with mechanically improved properties whilst still maintaining the characteristic transparency of pure silica aerogels. Solid-state 29Si-NMR spectroscopy was used to determine the condensation degree of the silanols and to evaluate the number of superficial hydroxyl groups. Mechanical properties were measured using nanoidentation. We observed that, as the organic part increases, the hybrid aerogels can be more easily deformed (lower Young Modulus values) although the hardness value is not affected.  F. Schwertfeger et al., J. Sol-Gel Sci Technol., 1994, 2, 103-108; A.V. Rao et al., Journal of Non-Crystalline Solids, 2001, 285, 202-209; A. Roig et al., Chem. Commun., 2004, 2316-2317; E. M, Lucas et al. J. Non-Cryst. Solids, 2004, 350, 244 ; Ann M. Anderson et al., J. Sol-Gel Sci. Technol., 2010, 53, 199-207. L. Martín, J. O. Ossó, S. Ricart, A. Roig, O. García and R. Sastre, Journal of Materials Chemistry, 2008, 18, 207-213.
9:00 PM - BB4.9
Drug Impregnated Magnetic Nanospheres for Biomedical Applications.
Nerea Murillo-Cremaes 1 , Elena Taboada 1 , Ana Maria Lopez-Periago 1 , Xavier Saurina 2 , Concha Domingo 1 , Anna Roig 1 Show Abstract
1 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 2 Analytical Chemistry, Universitat de Barcelona, Bellaterra Spain
The use of supercritical carbon dioxide (scCO2) as a solvent to perform adsorption and impregnation processes, materials functionalization and chemical reactions has received considerable attention as a viable and sustainable alternative to conventional liquid solvents. We will present the use of supercritical fluid assisted sol-gel methods for the production of a nanostructured magnetic carrier (Fe3O4@SiO2) as well as the use of supercritical carbon dioxide to impregnate a therapeutic agent (triflusal) in such magnetic silica microporous nano-spheres without modifying the matrix or the guest material. The designed systems will have applications as a controlled and target drug delivery system having the greatest therapeutic potential in those clinical scenarios that require the delivery of active agents at a specific point of the body while avoiding systemic effects of toxicity.
Stephanie Brock Wayne State University
George Gould Aspen Aerogels
Anna Roig Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC)
Debra Rolison U. S. Naval Research Laboratory
BB5: Energy I - Oxides
Tuesday AM, November 30, 2010
Room 103 (Hynes)
9:30 AM - **BB5.1
Designing Transition Metal Oxide Aerogels for Enhanced Energy Storage.
Veronica Augustyn 1 , Jong Woung Kim 1 , Bruce Dunn 1 Show Abstract
1 Materials Science & Engineering, University of California Los Angeles, Los Angeles, California, United States
Transition metal oxide aerogels possess a number of significant electrochemical properties not exhibited by the corresponding xerogel and crystalline materials. The continuous macroporous and mesoporous volume of an aerogel is quite beneficial as it provides both molecular accessibility and rapid mass transport, which are important for electrochemical electrode reactions. In addition, short electron and ion diffusion paths, a high concentration of surface sites, and an interconnected porosity enable the electrolyte to fully penetrate the electrode and have complete access to the redox-active pore walls. In this paper we describe the enhanced energy storage properties of vanadium oxide aerogels. The characteristic nanoscale ribbon morphology of this material leads to the development of a pseudocapacitive charge storage mechanism. The high capacities and specific capacitances shown by vanadium oxide aerogels lead to electrochemical characteristics which combine elements of both capacitor and battery behavior. The reversible insertion of a wide variety of monovalent and divalent ions allows the possibility for the use of vanadium oxide aerogels in non-lithium energy storage systems. In addition, our recent studies show that vanadium oxide aerogels can be cycled reversibly at low potentials to produce capacities in the range of 800 mAh/g; in contrast, the orthorhombic material cannot sustain such high lithiation levels. There is very little “bulk” material in vanadium oxide aerogels: their unique electrochemical properties are therefore dominated by surface and interface effects.
10:00 AM - BB5.2
Amorphous Lithium Manganese Phosphate Aerogels via Non-aqueous Sol-gel Processing.
Michael Stark 1 , Juergen Holzbock 1 , Norio Sato 2 , Nicola Huesing 1 3 Show Abstract
1 Inorganic Chemistry, Ulm University, Ulm Germany, 2 Materials&Research R&D, Toyota Motor Europe, Zaventem Belgium, 3 Materials Chemistry, Paris Lodron University of Salzburg, Salzburg Austria
Lithium manganese phosphates have received increasing attention in recent years as electrode materials for rechargeable lithium batteries. One of the major drawbacks of LiMnPO4 in the application as electrode material is the low ionic (lithium ions) and very low electronic conductivity. For an improvement of the latter point, a carbon coating is typically applied on the phosphate material; to improve the lithium ion conductivity, the particle size has to be decreased.The very unique properties displayed by aerogels, e.g. nanoscale particles building up the solid backbone comprising a highly porous network with pore sizes mainly in the nanometer regime, not only provide molecular accessibility and rapid mass transport, but also fast lithium ion diffusion due to the small particle sizes.[1, 2] Combined with the high porosities, large specific surface areas und low densities, LiMnPO4 based aerogels seem to be ideal candidates as precursor materials for such electrodes. Interestingly, only few aerogel compositions – mainly focusing on carbon and vanadium oxides – have been investigated for battery applications up to now. Lithium manganese phosphate syntheses are typically based on solid state reactions, however recently, solution-based techniques became more and more attractive, since a better stoichiometric control, shorter reaction times at lower temperatures, in addition to a better control over pore sizes and morphology (particles, fibers, tubes) can be achieved.In the present work, a synthesis based on sol-gel processing in non-aqueous environments is applied to obtain an amorphous, highly porous LiMnPO4 matrix after supercritical extraction with carbon dioxide. Stoichiometric control is achieved via carefully adjusting the precursor composition. The thus obtained amorphous LiMnPO4 aerogels were thoroughly characterized by XRD, electron microscopy, infrared spectroscopy, sorption and chemical elemental analysis. The stability of the gels with respect to ageing and temperature as well as their electrochemical performance will be discussed. Via heat treatment phase pure, crystalline lithium manganese phosphate with olivine structure is obtained.  G.M. Pajonk, Catal. Today, 1997, 35, 319 N. Hüsing, U. Schubert, Angew. Chem. Int. Ed. 1998, 37, 22 D.R. Rolison, B. Dunn, J. Mater. Chem., 2001, 11, 963
10:15 AM - BB5.3
Iron (III) Oxide Aerogels as Li-ion Intercalation Hosts for Electrochemical Energy Storage.
Benjamin Hahn 1 , Jeffrey Long 1 , Debra Rolison 1 Show Abstract
1 Surface Chemistry Branch (Code 6170), Naval Research Laboratory, Washington, District of Columbia, United States
Recent advances in nanotechnology have spurred the development of new cathode materials for Li-ion batteries with an emphasis on designing intercalation hosts that display electrochemical reversibility and large Li-ion capacities. Compared to conventional microcrystalline phases, nanocrystalline domains have lower solid-state transport lengths, are less influenced by the mechanical strain that is incurred during electrochemical redox, and have higher surface-to-volume ratios that both amplify interfacial contact with the electrolyte and increase electrochemical reaction kinetics. These advantages have been realized with γ-Fe2O3, where 8–10 nm particles have been shown to achieve Li-ion capacities > 200 mAh/g at high Coulombic efficiency. We plan to extend this work by synthesizing iron oxides through an epoxide-based protocol to achieve highly porous, three-dimensional architectures with extremely low densities (i.e., aerogels). The stoichiometry and crystallinity of these materials can be tailored at low temperatures (< 300°C) while maintaining surface areas > 100 m2/g. The goal of this project is to demonstrate proof-of-concept data that high-performance electrode materials can be designed from composites consisting primarily of rust and void space.. A. S. Aricò, P. Bruce, B. Scrosati, J.-M. Tarascon, W. V. Schalkwijk, Nature Mater., 4, 366 (2005)..M. Quintin, O. Devos, M. H. Delville, and G. Campet, Electrochim. Acta, 51, 6426 (2006)..J. W. Long, M. S. Logan, C. P. Rhodes, E. E. Carpenter, R. M. Stroud, and D. R. Rolison, J. Am. Chem. Soc. 126, 16879 (2004).
10:30 AM - BB5.4
Lithium Titanate Aerogel for Advanced Lithium Ion Batteries.
Ryan Maloney 1 , Jeffrey Sakamoto 1 Show Abstract
1 Chemical Engineering & Materials Science, Michigan State University, East Lansing, Michigan, United States
As society transitions away from fossil fuels towards alternative energy sources, it has become increasingly important to develop advanced materials for energy storage. For electrical energy in particular, lithium-ion technology is the current state of the art, and yet it is not without limitations. Recent advances in cathode materials have greatly improved the promise of lithium-ion batteries, but for widespread adoption the anode must be similarly improved upon. Current carbon anodes undergo dimensional changes during lithiation, causing internal stress and leading to degradation of the material as evidenced by capacity loss with cycling, especially at high charge rates. Lithium titanate spinel, however, undergoes negligible strain during charging, allowing it to undergo thousands of cycles with little capacity loss. In addition, in contrast with carbon-based anodes, lithium titanate does not form a Solid Electrolyte Interface (SEI), and thus there are no limitations regarding its surface area. Many groups have made progress in increasing the active surface area by reducing the grain size through high-energy ball milling or sol-gel processing of lithium titanate. These efforts have in general improved the power density and rate capability of the material. However, the sol-gel processing generally utilizes ambient drying techniques, resulting in xerogel and an increase in particle size after calcination.In this work, we present the synthesis and characterization of lithium titanate aerogels that maintain a surface area and microporosity close to that of their wet gel state. The composition, dimensions, surface area, rate capability and cycling performance of the lithium titanate aerogel are compared with lithium titanate xerogel powder. In addition, the effect of conductive additives added to the sol on the crystallite size and electrochemical performance is explored, as is the use of sacrificial carbon templates to decrease tortuosity and increase the power density of the electrode.
10:45 AM - BB5.5
Nanostructured Electrodes Fabricated Using Atomic Layer Deposition on Silica Aerogel Scaffolds for Photovoltaics.
Angel Yanguas-Gil 1 , Jeffrey Elam 1 , Vennesa Williams 3 , Richard Brotzman 1 , Michael Pellin 2 , Joseph Hupp 3 Show Abstract
1 Energy Systems Division, Argonne National Laboratory, Argonne , Illinois, United States, 3 Department of Chemistry, Northwestern University, Evanston, Illinois, United States, 2 Materials Science Division, Argonne National Laboratory, Argonne, Illinois, United States
Nanostructured electrodes are at the core of many photovoltaic devices. Two examples are dye sensitized solar cells and photoelectrochemical cells, which harness solar energy to generate electricicy or induce chemical reactions. The conventional way of synthesizing these nanostructured electrodes is by sintering nanoparticles of the desired composition into a film. An alternative approach recently developed involves a two-step process that combines sol-gel and Atomic Layer Deposition (ALD) to create first a silica aerogel scaffold that is later functionalized with the material of choice using ALD. ALD is a vapor phase chemical vapor deposition technique able to coat homogeneously substrates with high-aspect ratio features or high specific areas. One of the advantages of this method is the ability to create core-shell structures that incorporate different layers of functional materials. The goal of our research is to achieve a scalable, cost-effective manufacturing route that maximizes the efficiency and improves the electron collection efficiency of dye sensitized solar cells.In this work, we study the influence of both the sol-gel step and the Atomic Layer Deposition processes on the microstructure and properties of nanostructured electrodes for dye sensitized solar cells. We have examined the role that formulation, aging and drying have on the pore size distribution of the aerogel thin films, as well as the impact of the Atomic Layer Deposition on the microstructure and properties of the final nanostructured electrodes. Using this approach we have fabricated aerogel templated TiO2 and SnO2 nanostructured electrodes as well as core-shell structures involving transparent conducting oxides such as Al:ZnO/TiO2 and Sn:In2O3/TiO2. The results from our characterization and testing of these nanostructured photovoltaic devices will be presented.
BB6: Energy II - Carbon
Tuesday AM, November 30, 2010
Room 103 (Hynes)
11:30 AM - **BB6.1
Multifunctional Carbon Nanoarchitectures as Designer Electrode Platforms for Electrochemical Energy Storage.
Jeffrey Long 1 , Megan Sassin 1 , Christopher Chervin 2 , Jean Wallace 2 , Azzam Mansour 3 , Katherine Pettigrew 2 , Natalie Brandell 1 , Jennifer Dysart 1 , Debra Rolison 1 Show Abstract
1 Code 6170, Surface Chemistry Branch, Naval Research Laboratory, Washington, DC, District of Columbia, United States, 2 , Nova Research, Inc., Alexandria, Virginia, United States, 3 , Naval Surface Warfare Center-Carderock Division, West Bethesda, Maryland, United States
Carbon aerogels and nanofoams exhibit structural characteristics including high specific surface areas, through-connected networks of porosity with tunable pore sizes, and good electrical conductivity, that enable their use as high-performance electrode structures for electrochemical energy storage and conversion. To further extend their applicability, we use fiber-paper-supported carbon nanofoams as the basis for “multifunctional electrode nanoarchitectures” in which the nanofoams serve as conductive, ultraporous scaffoldings for subsequent incorporation of electroactive functionalities such as metal oxides, metal nanoparticles, and ultrathin polymers. The resulting functionalized carbon nanofoam papers are designed to serve as “plug-and-play” electrode structures in electrochemical devices ranging from high-rate Li-ion batteries and electrochemical capacitors to metal-air batteries and fuel cells. For electrochemical energy-storage applications, we have developed self-limiting electroless deposition protocols to generate conformal, nanoscopic coatings of either manganese or iron oxides on the exterior and interior surfaces of carbon nanofoams. The nanoscopic morphology of the metal oxide enables charge-storage capacities that are higher than typically observed for the respective oxides used in conventional composite-electrode structures, while the nanoarchitecture design itself facilitates rapid charge–discharge of the oxide coating. En route to practical applications, these multifunctional nanoarchitectures also serve as convenient platforms for the investigation of fundamental electrochemical processes at nanoscale interfaces using a variety of spectroscopic techniques.
12:00 PM - BB6.2
Ultrahigh Surface Area Single Wall Carbon Nanotube Aerogel.
Kyu Hun Kim 1 , Mohammad F. Islam 1 2 Show Abstract
1 Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
Significant efforts have been focused on creating bulk single wall carbon nanotube (SWCNT) materials that exhibit the properties of individual SWCNTs due to many potential applications. Although SWCNTs have been predicted to have very high specific surface area (SSA) of 1315 m2/g (capped) , all SWCNT bulk materials thus far have order of magnitude lower surface area, possibly due to SWCNT bundling. We created ultralow density, free-standing, and electrically conducting single wall carbon nanotube (SWCNT) aerogel with high surface area from a wet gel of isolated SWCNTs. The density of our aerogel can be as low as 7.2 mg/mL. Our aerogel fabrication process avoided SWCNT aggregation resulting in an aerogel with surface area as high as 1238 m2/g which is close to the theoretical limit for pristine SWCNTs. The electrical conductivity of our SWCNT aerogel can reach as high as ~ 10 S/m at room temperature. Despite the ultralow density, the aerogel has improved structural integrity, and thus, polymer reinforcements are not needed. The high surface area, large porosity, thermally insulating, and electrically conducting properties can make these aerogels excellent candidates as electrodes in organic photovoltaic devices and thermoelectric converters. This work was supported by NSF through grants DMR-0645596 & CBET-0933510, and the Sloan Foundation.References  Peigney, A.; Laurent, Ch.; Flahaut, E.; Bacsa, R.R.; Rousset, A., “Specific surface area of carbon nanotubes and bundles of carbon nanotubes”, Carbon, vol. 39, pp. 507-514, 2001.
12:15 PM - **BB6.3
Novel Carbon Aerogel Architectures for Energy Storage Applications.
Theodore Baumann 1 , Marcus Worsley 1 , Joe Satcher 1 Show Abstract
1 , Lawrence Livermore National Laboratory, Livermore, California, United States
Carbon aerogels (CAs) are a unique class of porous materials that hold technological promise for a variety of applications, including catalysis, adsorption and energy storage. The utility of these materials is derived from their high surface areas, electrically conductive frameworks and tunable porosities. In addition, the flexibility associated with CA synthesis allows for the incorporation of modifiers, such as carbon nanotubes or metal nanoparticles, that can potentially enhance the thermal, electrical, mechanical or catalytic properties of the aerogel. In this presentation, we will discuss our recent efforts in the design of new CA architectures for use in a range of energy-related technologies, including hydrogen storage, catalysis, batteries and electrochemical actuators. These efforts were supported in part by DOE through the Energy Efficiency and Renewable Energy program.Work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
12:45 PM - BB6.4
Functionalized Carbon Nanofoam Architectures as Air-cathodes for Li–air and Zn–Air Batteries.
Christopher Chervin 1 , Natalie Brandell 1 , Jeffrey Long 1 , Jean Wallace 2 , Debra Rolison 1 Show Abstract
1 Surface Chemistry Branch, The Naval Research Laboratory, Washington, District of Columbia, United States, 2 , Nova Research, Inc., Alexandria, Virginia, United States
Sol–gel-derived carbon nanofoam architectures are promising gas-diffusion substrates for air-cathode applications due to their tunable pore structures, through-connected pore–solid network, highly conductive carbon framework, and ease of functionalization with oxygen reduction electrocatalysts.1 Scalable, monolithic carbon nanofoam substrates are synthesized by infiltrating carbon fiber paper supports with a phenolic–formaldehyde sol followed by curing, drying, and pyrolysis. The resulting carbon nanofoams are then converted to active oxygen reduction electrodes by functionalizing with electrocatalysts such as manganese oxide (MnOx) or specifically adsorbed Pd nanoparticles on and within the interior of the nanofoam. Conformal, 10–20-nm thick coatings of MnOx are “painted” onto the walls of the carbon nanofoam via electroless deposition using aqueous permanganate, whereas pre-formed Pd is distributed at the carbon surfaces by specifically adsorbing to sulfur functionalities on thiophene-modified nanofoams. Here we present the fabrication and electrochemical characterization of functionalized carbon nanofoam electrodes evaluated under air-cathode conditions in either aqueous (Zn–air battery operation) or nonaqueous (Li–air battery operation) electrolytes. D.R. Rolison, J.W. Long, J.C. Lytle, A.E. Fischer, C.P. Rhodes, T.M. McEvoy, M.E. Bourg, and A.M. Lubers, Chem. Soc. Rev. 2009, 38, 226.
BB7: Reactive Aerogels I - Bio & Medical
Tuesday PM, November 30, 2010
Room 103 (Hynes)
2:30 PM - **BB7.1
Aerogels for Pharmaceutical Applications.
Irina Smirnova 1 Show Abstract
1 Institute of Thermal Separation Processes, Hamburg University of Technology, Hambug Germany
In this presentation an overview about the potential applications of organic and inorganic aerogels in the fields of pharmacy, cosmetics, and medicine is given. Having exceptionally high surface area and pore volume, aerogels are ideal candidate for drug delivery systems. Active agents can be incorporated into aerogels either by adsorption from liquid or supercritical solutions or by co-processing during the sol-gel process. In all cases the drug should withstand the corresponding experimental conditions. The chemistry of aerogel materials is rather flexible: their pore size and surface area can be tailored; furthermore different functional groups can be implemented in order to provide effective drug-aerogel interactions and so to influence the release kinetics. Here the possibility to tailor the release kinetics of drugs by changing of aerogel`s properties (hydrophobicity, density, surface area, pore size) is demonstrated. Adsorption of drugs on aerogels leads to the formation of amorphous layer of the drug on the aerogel surface. The concentration of the drug on the carrier can be varied by altering of the aerogel`s density and surface area, whereas the release rate of the drug depends on the hydrophobicity and pore size of the aerogel. In case of hydrophilic aerogels extremely fast release of drugs is achieved, which is especially advantageous for poorly water soluble drugs leading to their improved bioavailability. This effect bases on the collapse of the structure of hydrophilic aerogels in aqueous solutions due to the surface tension inside the pores. Hydrophobic aerogels exhibit slower release, which is governed by diffusion, since they are more stable in water. Application of aerogels as a carrier for a number of drugs (e.g. ketoprofene, ibuprofene, flurbiprofene, miconazol, griseofulvin) is presented and the performance of the resulting formulations is compared with that of corresponding nanoparticles. Furtherone, dependence between the nature and amount of the functional groups on the aerogel surface and their adsorption and release properties is demonstrated. At last, the processing of the aerogels to pharmaceutically relevant formulations (tablets, creams) is shown.
3:00 PM - BB7.2
Organic Biodegradable Aerogels Used In Controlled Drug Release.
Anja Veronovski 1 , Zoran Novak 1 , Zeljko Knez 1 Show Abstract
1 Faculty of Chemistry and Chemical Engineering, University of Maribor, Maribor Slovenia
There are a lot of synthetic polymers which can be used for controlled drug delivery. However, they are not easily accepted by organism. Also, incorporating drugs into carriers runs under difficult conditions. Therefore scientists have been inclined to use natural-origin polymers, such as proteins and polysaccharides. Some of these promising natural polysaccharidic candidates are alginic acid sodium salt, guar gum and chitosan due to their outstanding merits. They are similar to extracellular matrix having high chemical versatility, good biological performance and cell or enzyme-controlled degradability. Many polysaccharidic hydrogels for drug delivery have already been prepared, but one of their weakness is their short life in dry air conditions; thus, special coating materials are being developed for enhancing their life time.Alginates were used in the present research for the synthesis of organic biodegradable gels by sol-gel process, which were further easily converted to aerogels by supercritical drying. They are safe for use, nontoxic, and derived from renewable sources. Aerogels made of alginate are dry and stable materials, and that makes them interesting as a substitute to hydrogels. Alginates undergo reversible gelation in aqueous solution through interaction with divalent cations such as Ca2+, which create ionic inter-chain bridges. Two fundamental methods of ionic cross-linking were used to prepare alginate hydrogels: the diffusion method, where spheres are created, and the internal setting method, resulting in monoliths. After producing hydrogel, alcogels were formed by solvent exchange using absolute ethanol. Ethanol was later replaced by CO2 with supercritical drying (100 bar, 35°C). Aerogels made from natural polysaccharides combine both biocharacteristics and aerogel characteristics such as high porosity and specific surface area, which makes them really attractive in drug delivery applications. The aerogels obtained in the present research were therefore studied as drug carriers. The effects of alginate composition and synthesis method on model drug nicotinic acid release were investigated. The results indicated that by using the internal setting cross-linking method for obtaining aerogels, nicotinic acid was released in a more controlled manner. That is why further investigation was done on alginate spherical beads for prolonging the drug release. A multi-step sol-gel process was applied to generate complex aerogels with multi-membranes. First, ionically cross-linked spherical cores were obtained by dropwise addition of sodium alginate solution into a CaCl2 solution. These cores were further immersed into alginate solution, which is saturated with nicotinic acid, filtered through a sieve and dropped into a salt solution again. By repeating the above process, different multi-membrane hydrogels were produced and further converted to aerogels. By adding more membranes around core burst drug release was successfully inhibited.
3:15 PM - BB7.3
Aerogel-inspired Synthesis of Magnetic Silica Nanospheres by Supercritical Fluid Assisted Sol-gel Approach Application as T2 Contrast Agent for MRI.
Anna Roig 1 , Elena Taboada 1 , Elisenda Rodriguez 2 Show Abstract
1 , Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 2 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
We will report on a convenient method for the synthesis of magnetic silica nanospheres as well as the results from the evaluation of these materials as contrast agents for MRI. Fabrication of the magnetic silica nanospheres was done in a straight forward one-pot method combining sol-gel chemistry and supercritical fluids technology . Briefly, pre-formed iron oxide superparamagnetic nanoparticles stabilized in hexane (7 nm in diameter) are dispersed in a sol containing a silicon alkoxide, water and acetone as the solvent. The precursor solution is introduced in an autoclave and pressurized with compressed CO2. Then, pressure and temperature are raised over the supercritical conditions of the CO2/acetone mixture allowing the silicon alkoxide to hydrolyze and condensate forming the silica shell. The composite gel nanoparticles get dried as the solvent is extracted at supercritical conditions. Composite nanospheres present a narrow particle size distribution. Each nanosphere consists of a magnetic core of several non-contacting γ-Fe2O3 nanoparticles, surrounded by a microporous silica shell. The nanospheres are superparamagnetic at RT presenting an enhanced magnetization compared to the initial preformed iron oxide nanoparticles. Their size can be tuned by controlling the reaction conditions. Some advantages of the method are short reaction times, purity of the product and potentiality of the method to be scaled up. Moreover, the silica shell could be further functionalized with targeting directing agents or it could be used to carry a therapeutic pay load. Cytotoxicity and evaluation of the composite nanospheres as contrast agents for MRI will also be reported. Remarkably, the composite nanospheres show very high transversal relaxivity values (130 – 326 s-1mMFe-1 at 20 MHz, 37 C) that can be linearly correlated with the magnetic moment of the composite particles .  Taboada et al., Advanced Functional Material, 19, 14 (2009) 2319. Taboada et al., Mater. Res. Soc. Symp. Proc. 1257, (2010), 1257-O05-06We are grateful to Prof. R. Weissleder at the Center for Molecular Imaging Research, Massachusetts General Hospital for the relaxivity and cytotoxic measurements performed by E.R. during the post-doc stay in his group.
3:30 PM - BB7.4
Self-organized Protein Superstructures in and out of Ultraporous Silica Nanoarchitectures.
Debra Rolison 1 , Amanda Harper-Leatherman 2 1 , Mariam Iftikhar 2 , Adela Ndoi 2 , Christopher Rhodes 1 , Jeffrey Long 1 Show Abstract
1 Surface Chemistry, U.S. Naval Research Laboratory, Washington, District of Columbia, United States, 2 Chemistry & Biochemistry, Fairfield University, Fairfield, Connecticut, United States
Ultraporous, multifunctional nanoarchitectures are fabricated by “nanogluing” appropriate guests into the network of an about-to-gel silica sol . Biofunctionality can also be engineered into supercritical-fluid-processed silica aerogel nanoarchitectures. We have incorporated viable cytochrome c (cyt. c), a heme protein, into silica nanoarchitectures by nanogluing a cyt. c superstructure (nucleated in the liquid phase by colloidal gold) into the gel. In buffered medium, the superstructure (containing thousands of proteins) stabilizes the interior proteins, as shown by a shift to higher pK of unfolding, while also stabilizing them to the harsh conditions necessary to produce an aerogel, as monitored by shape and intensity of the Soret band. Within the silica matrix, the protein reversibly binds gas-phase NO and remains in a stable configuration for >6 weeks at room temperature under ambient humidity . We have also explored the properties of the colloid-nucleated self-organized protein superstructure by varying the size and type of metal colloid and the protein . We have recently shown that the Au nanoparticle that nucleates the protein superstructure serves as a nanoscopic Fort Knox for the protein molecules whereby hundreds to thousands of electrons are extracted from the Au nanoparticle to form ferrocytochrome c. These studies provide fundamental information on the interactions between self-organized biological entities, porous mineral membranes, and physicochemical conditions normally deleterious to biomolecules.  C.A. Morris, M.L. Anderson, R.M. Stroud, C.I. Merzbacher, D.R. Rolison, Science 284 (1999) 622. J.M. Wallace, J.K. Rice, J.J. Pietron, R.M. Stroud, J.W. Long, D.R. Rolison, Nano Lett. 3 (2003) 1463. J.M. Wallace, B.M. Dening, K.B. Eden, R.M. Stroud, J.W. Long, D.R. Rolison, Langmuir 20 (2004) 9276.
3:45 PM - BB7.5
Nanostructured Three-dimensional Architectures Incorporating Bioactivity.
Amanda Harper-Leatherman 1 , George Lisi 1 , Christopher Koenigsmann 1 , Jessica Fullagar 1 , Mariam Iftikhar 1 , Adela Ndoi 1 , Steven Scappaticci 1 Show Abstract
1 Chemistry & Biochemistry, Fairfield University, Fairfield, Connecticut, United States
Sol-gel-based aerogels are three-dimensional, nanoscale materials that combine large surface areas and high porosities. These traits make them useful for sensing or electrochemical applications when chemical dopants are incorporated into the gels to add functionality. Our work involves encapsulating proteins into aerogels as there is potential to make use of these biomolecular aerogels in bioanalytical devices. These studies also add to the knowledge of how protein environment and organization affect protein properties. Cytochrome c (cyt. c) has been successfully doped into aerogels through the incorporation of gold (or silver) nanoparticle nucleated protein superstructures,,. We have recently replaced the organizing nanoparticles in the superstructures with conductive carbon nanotubes (CNTs) to open up the possibility for future electrochemical device development. We will present UV-visible, fluorescence, and circular dichroism spectroscopic results demonstrating the viability of CNT~cyt. c assemblies in buffered media and encapsulated in aerogels. We will also discuss our recent efforts that show that cyt. c retains some structural integrity in aerogels under specific buffer strength, protein concentration and drying conditions without the presence of nucleating nanoparticles. Wallace, J.M.; Rice, J.K.; Pietron, J.J.; Stroud, R.M.; Long, J.W.; Rolison, D.R. Nano Lett. 2003, 3, 1463–1467. Wallace, J.M.; Dening, B.M.; Eden, K.B.; Stroud, R.M.; Long, J.W.; Rolison, D.R. Langmuir 2004, 20, 9276–9281. Wallace, J.M.; Stroud, R.M.; Pietron, J.J.; Long, J.W.; Rolison, D.R. J. Non-Cryst. Solids 2004, 350, 31–38.
BB8: Reactive Aerogels II - Energy & the Environment
Tuesday PM, November 30, 2010
Room 103 (Hynes)
4:30 PM - **BB8.1
Magnetic Nanocomposite Aerogels.
Anna Corrias 1 Show Abstract
1 Department of Chemical Sciences, University of Cagliari, Monserrato (Cagliari) Italy
Aerogels are regarded as ideal candidates for the design of functional nanocomposites containing supported metal or metal oxide nanoparticles. The large specific surface area together with the open pore structure enables aerogels to effectively host finely dispersed nanoparticles up to the desired loading, to provide nanoparticle accessibility and/or to prevent nanoparticle agglomeration, as required to supply their specific functionalities.The preparation of highly porous nanocomposite aerogels containing magnetic metal, alloy or metal oxide nanoparticles dispersed into amorphous silica, with high purity and homogeneity, was successfully achieved by a novel sol-gel procedure involving urea-assisted co-gelation of the precursor phases. This method allows fast gelation, giving rise to aerogels with 97% porosity, and it is very versatile allowing to vary composition, loading and average size of the nanoparticles. The characterization of the morphological and structural features of the nanocomposite aerogels is carried out using different techniques, such as X-ray diffraction, Transmission Electron Microscopy and X-ray Absorption Spectroscopy. The characterization of the magnetic properties is carried out by SQUID magnetometry.
5:00 PM - BB8.2
Fabrication and Characterization of Novel Energetic Nano-composites from Carbon-based Aerogel Scaffolds.
Alex Gash 1 , Theodore Baumann 1 Show Abstract
1 Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California, United States
Carbon aerogels are porous solids with interconnected carbon particles that have continuous porosities and very high surface to volume ratios. Activated carbon aerogels are characterized by extremely high surface areas (~3000 m2/g) and a hierarchical pore structure consisting of macro- and micro-pores. This assembly is especially flexible for fabricating free-standing monolithic aerogel nano-composites for several reasons: 1) Its macro-pores enable rapid fluid diffusion of a second phase precursor into its structure, 2) The micro-pores that allow deposition of nanometer-sized domains of dopant and provide intimate contact between the component phases, and 3) The mechanical strength of the material allows air-drying of monoliths without cracking. Here we describe the use of carbon aerogels as a scaffolds for the formulation of energetic nano-composites by infiltrating the carbon scaffold with a solution inorganic oxidizers and removal of the carrier solvent through ambient or freeze-drying. This approach enables energetic composites with oxidizer and fuel mixed on extremely fine scale, unavailable by other techniques. Composites were characterized by scanning electron microscopy, differential scanning calorimetry, elemental analysis, and thermo-gravimetric analysis. These results are compared and contrasted with those for straightforward mechanical mixes of carbon foam fuel and inorganic oxidizer. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344
5:15 PM - BB8.3
MgO Aerogels for Absorption Enhanced Reforming of Methane.
Winny Dong 1 , Mingheng Li 1 , Kenneth Kelley 1 , Michael Siditsky 1 , Joshua Wilson 1 Show Abstract
1 Chemical and Materials Engineering, Cal Poly Pomona, Pomona, California, United States
Both experimental and computational studies indicate that CO2 adsorption during the steam reforming of methane is a promising technique for enhanced hydrogen production. For adsorption enhanced reforming (AER), hydrotalcite, a MgO based ceramic, is the most commonly used adsorbent. In this study, the CO2 adsorption/desorption characterics of sol-gel dervied MgO, Ni- and Co-doped MgO aerogels were measured and compared to that of hydrotalcite. This was accomplished through TGA and analyzing the gas composition in a miniature reactor. The experimental results were coupled with theoretical thermodynamic analysis to explore the effect of CO2 adsorption on graphite formation in the catalyst. The results can lead to catalysts with longer lifetimes and lower reaction temperatures.
5:30 PM - BB8.4
3-D Nanostructured Catalytic Aerogels for Simultaneous Low-temperature Destruction and Electrical Detection of Chemical Warfare Agent Simulants.
Jeremy Pietron 1 , Lindsey Szymczak 1 , Debra Rolison 1 Show Abstract
1 Surface Chemistry, U.S. Naval Research Laboratory, Washington, District of Columbia, United States
We are developing a detection/mitigation system comprising catalytically active 3-D composites of Au nanoparticles sited within anatase titanium dioxide nanoarchitectures. The detection functionality arises because oxidative reactivity of chemical warfare agents (CWAs) at the Au–TiO2 nanocomposites induces transient changes in the electrical impedance of the composite. One architecture thereby enables simple, rapid electrical detection of CWAs simultaneously with their mitigation.When nanoscopic Au is supported on activating oxide supports such as titania, it is well established that peroxy species are generated at the metal/oxide boundary in the presence of molecular oxygen, even in the dark and at ambient temperature. Oxide-supported nanoscopic Au is renowned for its ability to oxidize carbon monoxide (CO) at room temperature to carbon dioxide. The high surface areas characteristic of aerogel-like nanoarchitectures are critical to throughput and adsorption of maximum quantities of CWAs. Our Au–TiO2 aerogels feature specific surface areas of ~100–150 m2/g: 2–3-fold greater than that of commercial nanocrystalline TiO2. The Au–TiO2 nanoarchitectures developed in our laboratory increase the triple-phase contact area of metal–oxide–agent, retain facile molecular transport (approaching open-medium diffusion rates), and stabilize the metal nanoparticles indefinitely with no special storage.Testing of the activity of Au–TiO2 aerogels towards the catalytic destruction of the CWA simulant dimethyl methylphosphonate (DMMP) is underway, as is the impedance response of the 3-D nanoarchitecture to the catalytic reaction.
5:45 PM - BB8.5
Fluorescent Organically Modified Silica Aerogel Thin Films for TNT Sensing.
Adem Yildirim 1 , Hulya Budunoglu 1 , Hakan Deniz 1 , Mustafa Guler 1 , Mehmet Bayindir 1 2 Show Abstract
1 Material Science and Nanotechnology Institute, Bilkent University, Ankara Turkey, 2 Department of Physics, Bilkent University, Ankara Turkey
Hybrid aerogel (super critically dried) and aerogel like xerogel (ambient dried) thin films are intrinsically porous, with random, well accessible, cylindrical, and branched mesopores. The high porosity allows molecules to easily access the inner parts of the material resulting very high diffusion rates. Although such high porosity hybrid structures would be indispensable in sensing and catalysis application, to date, aerogel thin film related work has been limited to applications that use only the intrinsic properties of these materials, such as low k materials and resistivity based humidity sensors. To the best of our knowledge, this work is the first demonstration of hybrid silica aerogel thin film preparation for an advanced application like sensing. Here we report a one pot approach for the preparation of a hybrid aerogel like xerogel thin film for TNT sensing by organic dye incorporation into ORMOSIL network. Aerogel thin films can be prepared by modifying the gel network with hydrophobic groups at atmospheric condition instead of by super critical drying. These hydrophobic groups on the surface prevent network collapse due to capillary tension and condensation reactions. In our case, we used intrinsically hydrophobic methyltrimethoxysilane (MTMS) monomer to achieve ambient drying in one pot process in which the unhydrolysable methyl groups cover the gel surface making the gel hydrophobic. Doping silica gels with organic molecules can be achieved by physical or by covalent bonding. If the organic molecules are dissolved in the monomer solvent in order to trap in the gel network during polymerization, these molecules are washed out during the washing and supercritical drying steps. To prevent leakage, dopants must be fixed into the silica network by covalent bonding or electrostatic forces, which further complicate the process. Our one pot approach, effectively overcomes leakage problem by altogether eliminating washing and supercritical drying steps; hence fluorescent ormosil coatings were successfully prepared by physical encapsulation of the Meso-tetrakis-p-carboxy-phenylporphyrin (TCPPH2) dye molecules.