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Symposium R: Materials for Renewable Energy at the Society and Technology Nexus

Symposium R: Materials for Renewable Energy at the Society and Technology Nexus Image
April 14 - 16, 2009

Chairs
David Ginley
NCPV NREL SERF W102
National Renewable Energy Laboratory
15313 Denver W. Pkwy.
Golden, CO 80401
303-384-6573
         Rahul Tongia
Dept. of Engineering & Public Policy
Carnegie Mellon University
Wean Hall 4624
Pittsburgh, PA 15213
412-268-5619


Proceedings to be published online
(see MRS Online Proceedings Library at www.mrs.org/opl)
as volume 1170E
of the Materials Research Society
Symposium Proceedings Series.


* Invited paper

SESSION R1: Energy and Environment
Chairs: Betsy Fleischer and David Ginley
Tuesday Morning, April 14, 2009
Room 2018 (Moscone West)


8:00 AM *R1.1
Wireless Sensor Networks for Energy and Process Monitoring Dan Steingart, Chemical Engineering, City College of New York, New York, New York.

While there is significant interest in improving materials that can convert renewable resources to electricity and store said electricity, there is also a need to improve electrical efficiency across industrial processes and commercial buildings. Wireless sensor networks provide a first step in measuring and aggregating various quantities such as pressure, temperature, current, potential, and humidity among others. Installations have been used to measure quantities in-situ in situations ranging from office buildings to photovoltaic arrays to aluminum smelters. This presentation will 1) review the capabilities and limitations of modern wireless sensor networks, 2) review the environmental conditions that can power such sensors and 3) provide a case study on how these nodes have been used to date, and what opportunities exist for future deployments. Wireless sensor nodes have existed in research labs for a decade, and over the past five years have seen implementation in fields from asset tracking to environmental monitoring to security to energy management. Nodes can be as simple as identification tags or powerful enough to sample at a 1 kHz frequency and perform statistical analysis before sending a calibrated data value. An overview of the current marketed nodes will be discussed, including the ease of use of setting up a network, cost per node, and extendability. Wireless sensor nodes typically operate well under 1 mW, with subsecond pulses on the order of 10 mW to 50 mW required for sensing, receiving and sending data. In the laboratory mechanisms ranging from vibration to photovoltaic harvesting have been proposed and verified, but real-world environmental coupling provides a difficult set of challenges. Successful implementations in aluminum smelters and residential use will be discussed, with particular attention paid to the pre-engineering auditing of the installation area. The economics of energy harvesting will also be discussed, as well as general guidelines size factors required. Finally, implementations of wireless sensor networks within aluminum smelters will be profiled. Aluminum smelters are an ideal use case for energy monitoring wireless sensor networks because 1) the production units are largely distributed, 2) aluminum smelting uses roughly 400 MW continuously per plant and 3) aluminum smelters operate at 45% to 50% of ideal efficiency. Additionally, the Hall-Heroult process produces considerable toxic and greenhouse gasses in addition to any emissions from the associated power plant. Methods of detecting and reducing such emissions with wireless sensor networks will be discussed.


8:30 AM *R1.2
The Global Energy Landscape Revisited. V. S. Arunachalam1, Anshu Bharadwaj1 and E. L Fleischer2; 1Center for Study of Science, Technology & Policy, Bangalore, India; 2Materials Research Society, Warrendale, Pennsylvania.

This paper presents recent developments in the energy field since the publication of the “Global Energy Landscape” article in the MRS Bulletin special issue, “Harnessing Materials for Energy.” Concerns about global warming and the need to harness renewable carbon-free energy have grown, with many governments of the world accepting the findings of the Intergovernmental Panel on Climate Change. This has brought in a renewed interest in nuclear power and also in nuclear breeders that use plutonium in a closed configuration rather than relying on a “once through” process. Solar power is evoking considerable interest and many countries are investing in large manufacturing facilities both for photovoltaic and concentrating solar thermal power. Notwithstanding the fluctuations in crude oil prices, research into hybrids and electric motor vehicles appears to be continuing with efforts to enhance the performance of batteries. Nanomaterials are seen as promising enablers for improving the performance of batteries. Despite the high costs, there is welcome progress in adopting light-emitting diodes for home and commercial lighting in preference to fluorescent lamps. Some countries have undertaken projects to convert coal to liquid fuel and to develop underground coal gasification in a shift toward domestic resources. On the other hand, there is still uncertainty as to when carbon capture and sequestration will emerge as a mature technology for large-scale commercial adaptation. There has not been significant development in harnessing hydrogen energy or further development and application of fuel cells.


9:15 AM *R1.3
Quantifying the Flow of Exergy and Carbon through the Natural and Human Systems. Richard Sassoon1, Weston A Hermann2, Ljuba Miljkovic1, I-Chun Hsiao1, Aaron J Simon3 and Sally Benson1; 1GCEP, Stanford University, Stanford, California; 2Tesla Motors, San Carlos, California; 3Lawrence Livermore National Laboratory, Livermore, California.

Exergy is the useful portion of energy that allows us to do work and perform energy services. While energy is conserved, its exergy content can be destroyed when the energy undergoes a conversion. We gather exergy from distinct, energy-carrying substances in the natural world we call resources. These resources are converted into forms of energy called carriers that are convenient to use in our factories, vehicles, and buildings for providing energy services such as heat, light and work. While there is no shortage of exergy resources, there are considerable environmental, economic, and other risks associated with the manner and magnitude of their use. This article describes a unique approach to examining and presenting data on our energy use at a global scale. It provides insights into the efficiencies and carbon emissions of many energy pathways, and could form the basis for an examination of future energy options. In this study, we trace the flow of exergy and carbon through the natural and human systems, revealing the major destructions of exergy, the exergy efficiency of human energy processes, and the processes most associated with atmospheric carbon emissions. A web-based interface (EnergyNavigator) has been developed to allow convenient investigation and analysis of global exergy and carbon flows.


10:30 AM R1.4
Green Innovation: Product, Process and Business Innovation Gains for Competitive Advantage. Shiva S Hullavarad and Nilima V Hullavarad; Office of Electronic Miniaturization, University of Alaska Fairbanks, Fairbanks, Alaska.

With rising electricity, gas and heating oil prices the human civilization is exploring new energy resources for sustaining the existence for future generations. Every innovation in energy conversion has lead to cheaper energy prices and hence enhanced energy demand, thus depleting the fossil fuel energy resources at an ever faster rate. There has been a tremendous interest gained in past 2 decades in harnessing energy from non-fossil fuels thus leading to a new industry in itself. The rabbit and turtle race between the fossil and non-fossil fuel energy adoption, prices and demand due to uncertainties in the consumer market has forced the business to adopt a radical approach in addressing the energy production by “green” methods, identify the preferred customer base and capture the “green” energy market. The paper addresses the “green innovation” in the non-fossil fuel industry. The objective of the study is to identify the changes in trends of non-fossil fuel energy industry demand, growth and opportunities. The study uses the databases such as patents, news events, income/financial statements to assess the company status and the track record of the industry. The paper provides innovation strategies based on inputs such as depleting fossil deposits, increasing energy prices, green technology implementation climate, consumer awareness and adaptation and obstacles. The research underlines the nature of energy solutions like development of hybrid motor vehicles as an alternative to oil motor vehicles, efficient energy storage batteries, fuel cells, and harnessing geothermal, hydro and biomass energy to key energy sectors. The study emphasizes how particular dominant designs in above energy sectors followed by disruptive innovations have lead to a new business model based on “organic” or “green” energy processing. This study correlates the gains in innovation tripartite (product, process, business) to the corporate competitive advantage. The study also summarizes the sustainable competitive advantages of some of the successful companies in the energy sector.


10:45 AM *R1.5
Conventional vs Sustainable Transportation Fuels for the Future Russell Robert Chianelli, MRTI, UTEP, El paso, Texas.

It is clear that in the next ten years major changes will be required in our liquids for transportation energy scenario. These changes are driven by two major factors. The first is the desire to achieve "energy independence" and the second is the desire to achieve an "environmentally friendly" fuel supply. These two forces will dominate energy research and development in the near future. This presupposes that the lack of viable hydrogen storage materials and the long range electric vehicle materials will continue to be limiting the hydrogen and electric vehicle technology. The DOE recently reported that the available amounts of heavy hydrocarbons (tars, coal and shale oils) in North America (United States, Canada and Mexico) are sufficient for 500 years at current rates of usage. However, these sources must be converted to liquid transportation fuels in an environmentally favorable manner. Also, promising sources of sustainable liquid transportation fuels maybe found in growing algae and converting the contained lipids to biodiesel. In this presentation we discuss recent development in both areas that promise a smooth transition from conventional to the use of sustainable transportation fuel sources.


11:30 AM *R1.6
Increasing Use of Recycled and Renewable Materials in Production Planning. Elsa A. Olivetti1, Randolph Kirchain1,2 and Frank Field2; 1Materials Science and Engineering, MIT, Cambridge, Massachusetts; 2Engineering Systems Division, MIT, Cambridge, Massachusetts.

It is estimated that the total consumption of non-fuel materials in the US exceeds 60 kg per person per day. While per capita consumption in the rest of the world lags the US by nearly an order of magnitude, it is growing at twice the rate. These estimates point to an important emerging global challenge in dealing with the attendant effects of unprecedented levels of materials use. Given the scope of this issue, the materials community will need to play a role in achieving sustainable consumption employing a wide variety of strategies. Increasing the efficient use of both secondary (i.e. recycled) and renewable (bio-derived) resources provides one such strategy. Energy benefits from increased use of recycled resources can be quite dramatic, such as for the case of aluminum which requires 175 MJ/kg for primary production compared to only 10-20 MJ/kg for secondary production. Secondary recovery also forestalls depletion of non-renewable resources and avoids the deleterious effects of extraction and winning (albeit by substituting some effects of its own). Regarding renewables, the ultimate benefits, including reduced energy use, reduced non-renewable depletion, and carbon sequestration, remain controversial for many current technologies and applications. Nevertheless, the trend in renewables technology development is promising. Increased use of secondary or renewable raw materials suffers from at least one barrier related to economic implementation - variation in incoming raw materials. In many instances, variability in quality is larger for raw materials derived from waste or from renewable, bio-derived sources than for raw materials derived from primary or synthetic sources. Controlling variation is crucial for producing materials that reliably meet quality specifications. Unfortunately, the most prevalent implementations of batch planning tools, a key means for production planning in process industries, overestimate this disincentive, and thereby underutilize highly variable raw materials. This research examines the benefits, in terms of increased recycling and renewable materials use, of one approach to batch planning that explicitly considers raw material variability, a chance-constrained (CC) model formulation. Previous work has shown that explicit consideration of operational uncertainties through the use of stochastic programming, in production planning can improve batch operator decisions without compromising the likelihood of batch errors. This work examines the pervasive nature of quality variability management through examples in both recycled and renewable materials contexts including cases from industries such as metals recycling, paper production, rubber processing and biomaterials production (such as collagen and gelatin). Specifically, we explore the generality of the benefits of a CC-based batch planning model, the drivers of that benefit, and the conditions that maximize benefit.


SESSION R2: Photovoltaics
Chairs: George Crabtree and Phil Parilla
Tuesday Afternoon, April 14, 2009
Room 2018 (Moscone West)

1:30 PM *R2.1
Materials Challenges in Photovoltaic Solar Energy Conversion. Reuben T. Collins1 and David S Ginley2; 1Physics Department, Colorado School of Mines, Golden, Colorado; 2National Renewable Energy Laboratory, Golden, Colorado.

Given, the immense size of the solar resource, photovoltaic (PV) conversion of solar energy into electricity has the potential to play an essential role in next-generation green power production. The PV industry has been experiencing rapid growth, however, the cost of PV produced electricity is still high relative to fossil sources and only a small fraction of world electricity production actually comes from solar energy. Reduced costs and improved efficiencies are essential if photovoltaics are to realize their potential, and materials advances are critical to both of these. While today’s technology relies primarily on wafer-based crystalline and polycrystalline silicon, efforts to substantially reduce costs emphasize highly absorbing thin films on low cost substrates. Technologies using polycrystalline inorganic semiconductors such as CdTe or Cu(InGa)Se2 are now in the market place and exhibiting much lower costs than silicon. Organic solar cells, which are compatible with low temperature solution synthesis and roll-to-roll production, offer the potential for significantly reduced cost if efficiencies and stability can be improved. Multijunction approaches allow a larger fraction of the solar spectrum to be captured with tradeoffs in complexity and cost that can be offset through use of solar concentrators. Nanoscale materials are receiving considerable attention because they offer additional degrees of freedom through control of size and shape that can be used to tune energetics and relative carrier relaxation rates to boost efficiency. In each of these systems resolving materials issues that extend from contacts, window layers and interactions at the interfaces to developing a better fundamental understanding of defect structure, surface passivation, and the basic nature of carrier relaxation dynamics is critical to the development of successful technologies. This talk will summarize materials research in these systems with an emphasis on the underlying materials challenges that need to be addressed in each.


2:15 PM R2.2
Abstract Withdrawn


2:30 PM *R2.3
Steady as She Goes: Sustaining Rapid Growth in Photovoltaics. John P. Benner1 and Marie K Mapes2; 1National Center for Photovoltaics, NREL, Golden, Colorado; 2U. S. Department of Energy, Washington, District of Columbia.

The installed capacity for photovoltaic generation of electricity in the United States is still a tiny slice of the generating mix of the country -- far less than 0.1%. The industry must maintain a growth rate greater that 40% annually to achieve national goals to exceed 10% of the total electricity capacity by 2020. Surprisingly, this high rate of growth has been exceeded during the past several years even as the industry passed through its first major bottleneck. The shortage of silicon feedstock certainly impeded the expansion plans of many companies, left much production capacity unused, and likely contributed to a flattening of the trajectory of cost reduction. Perhaps sales would have been even higher had this shortage not constrained growth. It is unlikely that the silicon shortage could have been avoided. As a young industry with disruptive technology, PV leaders were cautious in projecting growth figures. During the past decade internal industry estimates as well as those of analysts have consistently projected sales growth substantially below achieved rates. Suppliers undoubtedly subtracted a conservative margin from industries projections to counteract a presumed exuberance within the young industry. Looking forward, we can anticipate a number of other bottlenecks. We are already seeing longer lead times in equipment delivery. Feedstock for several leading technologies, including silicon, may continue to constrain growth. Distributed generation will soon grow to a point where utilities’ ability to integrate these sources may impede expansion. The current financial turmoil will limit expansion capital. Ultimately, we should all expect and welcome a shortage of government incentives, such that the technologies will be competing as low-cost energy producers. This paper will provide a status report on photovoltaics and explore means to overcome anticipated barriers to sustaining the necessary growth.


3:30 PM *R2.4
Prospects for Organic Solar Cells Michael David McGehee, Materials Science and Engineering, Stanford University, Stanford, California.

Molecular photovoltaic cells can be fabricated at low-cost using roll-to-roll coating processes similar to those used to make newspapers. They can be much cheaper than conventional cells because, in addition to having low materials costs, the cells can be printed and connected to each other in a high-throughput, integrated architecture. Today’s best organic solar cells have an efficiency of 6.5 % and last approximately 1 year under sunlight. The Center for Advanced Molecular Photovoltaics has plans for raising the efficiency and making the cells stable for ten years or more. Highlights of recent research will be presented.


4:15 PM R2.5
Predicting Electronic Properties and Efficiencies of Dye-Sensitized Solar Cells. Bryan M. Wong, Materials Chemistry, Sandia National Laboratories, Livermore, California.

Dye-sensitized solar cells (DSCs) have gained immense interest in the last few years due to their potential for converting clean solar energy to electricity at low cost. In particular, current research is now directed towards organic dye sensitizers which are less expensive and easier to synthesize. In order to develop these highly-efficient sensitizers, it would be extremely useful and cost-effective to use computational models beforehand to predict the efficiencies of candidate DSCs. To address this problem, we have recently used a new density functional computational method specifically designed to capture the charge-transfer effects in solar cell dyes. Based on several benchmark tests, we demonstrate that this computational approach provides an accurate description of light absorption efficiency to help guide the organic synthesis of candidate DSCs. The results of these calculations enable a guided approach to maximizing the light-harvesting properties and potential capabilities of future dye sensitizers.


4:30 PM *R2.6
Towards Highly Efficient Organic Solar Cells: Lateral Architecture for Absorption Enhancement. Rafi Shikler1,3 and Iris Visoly-Fisher2,3; 1Electrical and Computer Engineering, Ben Gurion University of the Negev, Beer Sheva, Israel; 2Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, Israel; 3IK Institute of Nanoscience and technology, Ben-Gurion University of the Negev, Beer-Sheva, Israel.

Organic semiconductors are excellent candidates for low cost photovoltaic (PV) cells, offering ease of processing and compatibility with flexible substrates. Common limitations to the function of organic PV materials include the small exciton diffusion length and low charge carrier mobilities, implying the need for a limited active layer thickness. Consequently, a small volume of material is used, reducing its cost, but at the same time limiting its possible absorption and, as a result, its efficiency. In addition, unlike inorganic semiconductors that can absorb all solar photon energies above their absorption edge, dye molecules absorb specific bands. These bands do not necessarily coincide with the intensity peaks in the solar radiation spectrum, and leave unabsorbed gaps in it. Various strategies were previously suggested to increase absorption and widen the absorbed wavelength range in organic solar cells. Commonly, the absorption enhancing entity is added above or below the photoactive layer, or mixed with it, which may affect charge transfer to the electrodes, induce quenching or limit the direct photon flux to the device. We present a new design aimed at enjoying the benefits of photonic structures without affecting the optimized PV device properties, which is low cost, simple and flexible, so as to allow accommodation of various organic PV devices with linear and non-linear absorption enhancement schemes. Furthermore, the proposed photonic crystal can combine linear photonic absorption enhancement with various nonlinear optical effects, approaching full-spectrum utilization. The innovation of our design is in the parallel implementation of each of its components, i.e., the photovoltaic cell and the photonic structure. This unique implementation allows optimization of each component separately, without affecting the other component. The hosting photonic structure traps the incident light inside the cell leading to enhanced absorption. Changing the material modifies the refraction index of the structure, while tuning the period determines the exact location of the enhanced absorption peaks. Using these two factors the wavelength of the trapped light can be tuned to coincide with the desired wavelength for maximized absorption of the molecular cell. We show theoretical calculation of enhanced absorption in the proposed structure. We also present an extension of this concept to include advanced absorption enhancement schemes with the use of plasmons in small metallic islands of gold or silver integrated into the photonic structure.


SESSION R3: Fuel Cells and Hydrogen I
Chairs: Reuben Collins and Sam Mao
Wednesday Morning, April 15, 2009
Room 2018 (Moscone West)

8:00 AM *R3.1
Novel Materials for Fuel Cell and Fuel Reforming Applications Yingke Zhou1, Robert Pasquarelli1, Michael Sanders1, Tim Holme2, Grover Coors4, Joe Berry3, David Ginley3 and Ryan O'Hayre1; 1Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado; 2Mechanical Engineering, Stanford Unviersity, Stanford, California; 3National Renewable Energy Laboratroy, Golden, Colorado; 4Ceramatec Inc., Salt Lake City, Utah.

The Advanced Energy Materials Laboratory at the Colorado School of Mines focuses on the characterization and deployment of nanostructured materials to improve energy conversion technologies including fuel cells and solar cells. This presentation will discuss two aspects of our recent research with particular relevance for fuel cell and fuel reforming applications: 1) doped carbon-supports for enhanced catalytic applications and 2) high temperature steam permeation in co-ionic ceramic materials. 1) Doped carbon supports for enhanced catalysis. Recent research suggests that catalytic activity of Pt nanoparticles towards a variety of low-temperature fuel-cell relevant reactions is significantly enhanced (by 3-10X) when a nitrogen-doped carbon support is used in place of a standard carbon support. This level of enhancement brings the technological promise of low-temperature fuel cells much closer to reality. Furthermore, the basic idea of catalyst-support doping opens the door to a game-changing new method for catalyst design, with applications not only in fuel cells, but also in industrial chemistry, biology, energy, and even medicine. While the reason for this surprising dopant-induced enhancement effect have so far remained uncertain, in this presentation we provide both experimental and theoretical results that clarify the situation by using highly ordered pyrolytic graphite (HOPG) as a model support. Our experimental results provide clear and compelling evidence that N-doping can be used to substantially enhance the catalytic activity (by a factor of 3-6 fold) and durability (by a factor of 10 fold) of carbon-suppported Pt catalysts. Supporting experimental evidence and theoretical calculations to show that the activity enhancement is due to a chemical doping effect, where N-HOPG donates charge to Pt clusters, changing the d-band electronic structure, and therefore the catalytic activity. Our theoretical calculations suggest that B-doping at low levels will have a similar impact as high-doses of N-doping. Therefore, a predictive model has been proposed, and experimental confirmation is ongoing. 2) High temperature steam permeation in co-ionic ceramics. Selective steam transport in dense proton-conducting ceramic membranes has been recently been hypothesized, but has so far never conclusively demonstrated experimentally. If verified, high-temperature ceramic steam-permeation membranes (SPMs) would have the potential to significantly improve the efficiency of a variety of energy conversion technologies including solid oxide fuel cells, membrane reformers, and gasification. In this presentation, we provide direct experimental evidence for steam permeation in yttrium-doped barium zirconate (BZY20) and discuss the mechanism of steam permeation in this material based on cell permeation and hydration dilatometry measurements over a temperature range of 20° - 1100°C.


8:45 AM R3.2
Proton Conductivity in Co-doped Perovskite Oxide BaZr0.5In0.25Yb0.25O3-δ. Istaq Ahmed1, Sten G Eriksson1 and Elisabet Ahlberg2; 1Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden; 2Chemistry, University of Gothenburg, Gothenburg, Sweden.

Introduction: Considerable attention is being focused on the synthesis and characterisation of new electrolyte materials with high proton conductivities at temperatures in the range 200-600°C. The lack of suitable materials currently limits the development of intermediate temperature range fuel cells [1]. The development and improvement of material conduction properties necessitates an understanding of the proton transport mechanism. Several models have been suggested to rational the correlation between structure and conductivity of perovskite oxides. Recently, Imashuku et al. [2] showed that proton conductivity can be improved by co-doping at B-site. However, this study was carried out on lightly doped systems. The concentration of protons in the material depends on the doping level of acceptor dopant. In this context we are aiming to investigate the crystal structure, microstructure and proton conductivity of heavily doped perovskite oxides, BaZr0.5In0.25Yb0.25O3-δ. The material was prepared via a traditional solid state sintering route. The results of x-ray powder diffraction, scanning electron microscopy (SEM), dynamic thermogravimetric analysis (TGA), and impedance spectroscopy will be discussed. Results: The unit cell parameter a, was determined to be 4.1991(5) Å with average P m-3m symmetry. Dynamic TGA on pre-protoneted sample shows that mass loss occurred beyond 300°C. The mass loss was 1.18‰ which implies that 78‰ of the protonic defects (OH●) were filled during hydration. The proton conductivity in this sample was investigated by using 2- probe AC impedance spectroscopy. Nyqvist plot of pre-protonated sample showed that grain-boundary conductivity is significantly higher than the bulk conductivity, which is typical for ziconate systems. References: [1] T. Norby, Solid State Ionics 125(1999) 1-11. [2] S. Imashuku et al., J. Electrochem. Soc., 155 (2008) B 581-B586.


9:00 AM R3.3
Synthesis of NiO/YSZ-YSZ Nano Composite Powders and Their Application for SOFC Anodes. Dae Il Yoon1,2, Jong Jin Lee1, Sang Hoon Hyun1 and Jae Hyuk Jang3; 1Advanced Materials Science and Engineering, Yonsei University, Seoul, Korea, South; 2The Specialized Graduate School of Hydrogen and Fuel Cell, Yonsei University, Seoul, Korea, South; 3Samsung Electro-Mechanics, Suwon, Gyeonggi-do, Korea, South.

The effects of the anode functional layer (AFL) for improving the performance of solid oxide fuel cells have been examined by inserting the NiO/YSZ-YSZ functional layer between the NiO-YSZ anode and YSZ electrolyte. The dual NiO/YSZ-YSZ composite powders synthesized by the polymerizable-complex method could be well described as the composite of nano-sized NiO and YSZ particles adhered to core YSZ particles, and their mean particle size and surface area were 0.4 µm and 39.0 m2/g, respectively. The AFL was fabricated by dip-coating the anode substrate with the slurry of composite powders, and the anode supported YSZ electrolyte was also prepared by dip-coating the composite anode with the YSZ slurry, followed by sintering at 1400°c. It was concluded that the composite AFL could minimize the possibility of defect occurrence between anode and electrolyte layers during processing as well as increase the number of the three phase boundary(TPB) considerably. The unit cell with the AFL of 8 µm thickness in conjunction with the LSM-YSZ cathode showed the maximum power density of 1.58 W/cm2 at 800°c in hydrogen (3% H2O), which is about 3 times higher than that of the unit cell without the AFL layer, and an excellent cell durability.


9:15 AM R3.4
Synthesis of YSZ and Ti: YSZ by Emulsion Precipitation Method and its Impedance Study. Manasa Kumar Rath, Susant K Acharya and Byung G Ahn; Major Electronic Materials Engineering, Chonbuk National University, Jeonju, Cholla Buk Do, Korea, South.

As it is well know that the dimension and the types of materials affect the performance of the SOFC. Hence a different anode material Ti:YSZ (anode) compatible thermal expansion coefficient with YSZ (electrolyte) was synthesized by emulsion precipitation followed by heat treatment. Nano-set ball milling of the powder was carried out in ethanol media. The phase, morphology and the porosity of the powder were analyzed by XRD, SEM, TEM and BET. YSZ pellet were prepared (99% of theoretical density) by cold iso-static uniaxial pressing with varying thickness, Ti: YSZ were coated on the pellets by screen printing process. Impedance spectroscopy was carried out at different temperatures of the symmetry cell and the half cell. Impedance measurement data were collected using different suitable circuit elements and plotted for analysis. The effect of relative thickness of the YSZ and the Ti: YSZ to the cell performance at intermediate temperature has been discussed in detail.


9:30 AM R3.5
High-temperature Oxidation of Metallic Alloys for SOFC Interconnects: Stress and Morphological Developments during Oxide Scale Growth and Influence of Reactive Elements. Audric Saillard1,2, Mohammed Cherkaoui1,2, Laurent Capolungo3 and Esteban P Busso4; 1Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia; 2UMI 2958 Georgia Tech - CNRS, Metz, France; 3Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico; 4Centre des Matériaux, Mines ParisTech, Evry, France.

Metallic alloys are massively employed in energy generation devices subjected to high temperatures such as gas turbines or more recently interconnects in solid oxide fuel cells (SOFC). However, an oxide scale inevitably grows at the oxygen-exposed surface, accompanied in most cases by the development of stresses and non-flat interfaces. While these phenomena limit the lifetime of such systems, the underlying mechanisms are still poorly understood which prevents material optimization. This work investigates the critical oxide/metal interface evolution. A framework has been developed along with a finite element-based numerical code for the propagation of the phase boundary coupled with stress development. The model considers a diffusion-driven process with mass consumption and it incorporates the large volumetric strain associated with phase transformation. A continuum mechanics description of a dissipative sharp interface propagation is derived to include the influence of the stress state and accommodation work on the phase boundary motion kinetics. The implementation of this complex formulation and its framework required the development of an original numerical scheme allowing a field-dependent propagation of a sharp interface. A finite element method is used for the strain/stress and concentration fields resolution, coupled with an external routine for calculating the interface composition, the effects of fast diffusion and the phase boundary propagation. The oxidation of a chromia-forming SOFC interconnect material is simulated and stress and morphological developments are investigated, with a particular focus on the influence of the known reactive element effects. The mechanisms likely leading to mechanical failure are discussed.


9:45 AM R3.6
Utilizing Micro X-Ray Tomography, ESEM, and ICP-MS to Characterize MEA/GDE Properties Mark Nelson, Tommy Rockward, Gang Wu, Rodney Borup and Fernando Garzon; MPA-11, Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico.

We report the use of Environmental Scanning Electron Microscopy, Laser Ablation Mass Spectrometry (ICP-MS), and high resolution X-ray Computed Tomography (XCT) to observe internal changes in the catalyst/ionomer morphology and catalyst distribution in the membrane and electrode assemblies (MEAs)/gas diffusion electrodes (GDE) after they have been subjected to various operating conditions and forms of testing. (e.g such as drive cycle testing) Membrane and electrode assemblies consisting of both conventional Pt-carbon catalyst mixtures and various non-precious metal catalysts were studied before and after fuel cell testing. Voltage cycling through potentials of 0.8 V causes Pt electrocatalyst sintering and consequently losses in electro-active surface area. Carbon corrosion is greatly accelerated when the FC is subjected to harsh start-up/shut-down conditions. In the case of non-precious catalysts, we are probing the catalyst/ionomer migration into the gas diffusion layer at various hot pressing temperatures. XCT imaging has the advantages of being non-invasive, requiring little sample preparation, not requiring the sample to be conductive, and not disturbing the microstructure of the sample when compared to conventional SEM or TEM. Elemental analysis via ICP-MS and X-ray analysis from the ESEM will be used to study catalyst and impurity distributions within MEAs at various stages of fuel cell lifecycle testing procedures.


10:30 AM R3.7
The Synthesis and Characterization of Durable Electrocatalyst Nanocomposite Supports Kimberly Michelle Cross and Yunfeng Lu; Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California.

The United States department of energy has placed hydrogen fuel cell research and development at the heart of its drive for energy independence. The current key barriers preventing commercialization of automotive-scale fuel cells are cost and durability of materials. Current materials used for catalyst support for electrocatalytic applications, such as carbon black, are continuously exposed to highly oxidative environments, which lead to carbon corrosion. Ceramic materials are highly stable in corrosive environments in comparison to carbon materials; however making inexpensive, conductive ceramic materials with adequate electronic conductivity, and controlled pore structure remains a major challenge. Corrosion-resistant mesoporous ceramic/carbon nanocomposites can be designed and fabricated by incorporating the conductivity of low-cost carbon materials with the chemical robustness of ceramic inorganic materials, thus creating a family of conductive, corrosion-resistant, chemically stable, porous nanocomposites which can be used for the next generation of durable electrocatalyst supports. Random disorder porous nanocomposites have been synthesized using a simple self-assembly process with a ceramic cluster (hydrolyzed tetraethylorthosilicate), a carbon precursor (sucrose), and porogens (zinc chloride). Pore size control was achieved by tuning the concentration of activation reagent, in which increasing the amount of ZnCl2 resulted in higher porosity (pore volume 0.1-0.3 cm3/g) and larger pore size (2-3nm). In addition, carbon/ceramic nanocomposites with ordered crystalline pore structures were constructed from a sol gel route using a surfactant (pluronic F127), inorganic cluster (hydrolyzed tetraethylorthosilicate), and oligomeric assembling blocks (phenol). Subsequent carbonization at high temperature produces both disordered and ordered mesoporous nanocomposites with controlled composition and pore structure. Preliminary conductivity studies concluded that an increase in carbon content leads to higher conductivity. When the carbon content is higher than 56%, the conductivity of carbon/silica nanocomposite can reach 6.6 S/cm, which is adequate for current fuel cell device application. Promising corrosion resistance was obtained from the carbon/silica nanocomposites. The weight loss under oxidative environment is reduced by ten times with the addition of silica while the nanocomposites is able to retain a high enough electrical conductivity. The fabrication of these nanocomposites provides a new family of porous nanocomposites for many potential applications, such as adsorbents, catalyst supports and hydrogen storage.


10:45 AM R3.8
Enhanced Electroactivities of Tungsten Carbides Supported Catalysts for Low Temperature Fuel Cells. Dong Jin Ham, Jae Sung Lee, Gang Hong Bae and Duck Hyun Youn; Chemical engineering, Pohang university of science and technology, Pohang, Korea, South.

Many researchers have investigated to develop a suitable anode catalyst for low temperature fuel cells such as DMFC and PEMFC. A large amount of precious noble metals particularly platinum is used for electrooxidation which makes the cost of DMFC and PEMFC prohibitively very high. Considering this fact, tungsten carbides have been considered as an alternating electrocatalyst at the anode and cathode electrode of low temperature fuel cells. Because they have shown high activities for electro-oxidation of hydrogen, methanol with minimal loading of noble metals or without them due to their platinum-like behaviors in catalysis. We have fabricated the various structures and phases of tungsten carbides preserved the excellent physicochemical properties and electro-activities via polymer induced carburization method. All electrocatalysts were characterized by XRD, PSD, SEM, HRTEM, LSV, CV and Single cell test so on. The fabricated tungsten carbides were corresponded to microporous and mesoporous W2C microspheres and mesoporous WC nanoparticle. Small amount of noble metals (less 10wt%) was loaded on these tungsten carbides via conventional chemical reduction and polyol method. Regarding the electrochemical evaluation, these electrocatalysts showed the higher electrochemical active surface area (EAS) values represented the hydrogen oxidation ability, and electro-activity for methanol oxidation reaction (MOR) than commercial Pt/C and PtRu/C electrocatalysts, respectively. Especially, 7wt% Pt loaded tungsten carbides resulted in the higher EAS values by factors of 3.0-3.5 than that of commercial 20wt% Pt/C (E-Tek) catalyst. And, they also displayed the high CO tolerance superior to the commercial Pt/C in 1% CO dissolved electrolyte. In addition, mass activity (mA/mg of Pt taken at 0.75V - Ag/AgCl) of all 7wt% Pt loaded tungsten carbide based catalysts showed the 2.5-3.42 times higher activity for methanol oxidation than commercial 20wt% PtRu/C (E-Tek) catalyst. Particularly, the single cell performances of small amount of noble metals loaded tungsten carbides for methanol oxidation will be firstly demonstrated in this presentation. These enhanced electro-activities may be originated from the synergistic effect between platinum and tungsten carbides including the intrinsic properties of tungsten carbides. Tungsten carbides could become a noble metal economic electrocatalyst for low temperature fuel cells.


11:00 AM R3.9
High-Throughput Optimization of Polyimide Blends for Proton Exchange Membrane Fuels Cells. Keith Gregory Reed and Carson Meredith; Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia.

The proton exchange membrane (PEM) fuel cell has become a central focus within the alternative energy industry. Its high power density and efficiency, along with environmental benefits and relatively low operation temperature make the PEM fuel cell an especially ideal power source for transportation applications. However, this promising technology is still not economically feasible for use in automobiles, being significantly limited by the PEM material itself, which degrades under the acidic operating conditions. To meet commercialization targets set by the Department of Energy for 2010, a radical new approach is needed for locating materials with markedly improved durability and performance-to-price characteristics. The extensive selection of low-cost polymers and polymer combinations, coupled with the broad effects of polymer processing conditions present an engineering challenge that is well-suited for high-throughput screening. In this work we describe the development and implementation of an efficient and thorough approach for screening these variables using high-throughput characterization of key fuel cell performance indicators. These include mechanical strength, proton conductivity, water transport, and chemical resistance. By incorporating combinatorial film synthesis techniques to produce 1-D and 2-D sample libraries, we have shown that we are able to screen and optimize processing properties such as composition ratio, thickness, annealing temperature, and cross-linking density with respect to the key fuel cell performance indicators in a cost-effective manner. From this screening, we can determine potential PEM candidates suitable for more detailed performance analysis. Of particular interest to this study are polyimide blends which are low cost and can be tuned for mechanical strength and durability through cross-linking density.


11:15 AM R3.10
Ionic Conductivity of NASICON-like MI3PO4-MIIIPO4 (MI-Li, Na; MIII-In, Sc) Phases. Galina Zimina1, Anna Potapova1, Irina Smirnova1, Felix Spiridonov2, Sergey Stefanovich2, Mariya Zhuravleva1 and Andrey Novoselov1; 1Department of Chemistry and Chemical Engineering for Rare and Dispersed Elements, Lomonosov Moscow State Academy of Fine Chemical Technology, Moscow, Russia; 2Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia.

Approach to targeted synthesis of promising superionic materials on the base of complex phosphates of Group III elements (In and Sc) was developed. New phases of high ionic conductivity were obtained using results of the systematic study on binary and ternary systems and crystal chemistry analysis of ionic transport in complex phosphates with NASICON-like three-dimensional framework. Heterovalent substitution into phosphates cation sublattice realized according to scheme M3+→M4++v (where v-is a vacancy) allows increasing conducting cation (Li, Na) mobility and tracing structure motif evolution. Samples were prepared through every 2-10 mol%, annealed at 800, 850, 900 and 1050°C during 200-400 h, quenched in liquid nitrogen and then were subject of powder X-ray diffraction analysis. Temperature dependence of ionic conductivity of NASICON-like Li3In2(PO4)3 solid solutions and heterovalent Zr-substituted Na3Sc2(PO4)3 samples was studied by impedance spectroscopy. Ionic conductivity of a solid solutions sample Li3-xIn2+1/3x(PO4)3 (x = 0.8) was calculated to be 0.44x10-2 S/cm at 300°C. This value is comparable to that of well-known NASICON-like compounds such as Li3Fe2(PO4)3. Heterovalent Zr-substitution of Na3Sc2(PO4)3 according to scheme Sc3+→Zr4++v leads to solid solutions formation up to 10 mol% Zr, while further substitution up to 20 mol% results in formation of a secondary phase. Ionic conductivity of Na3Sc2(PO4)3 (1.6x10-2 S/cm at 300°C) was considered to be the best among NASICON-like complex phosphates. However, that of 10 mol% Zr-substituted sample obtained in this work was calculated to be 3.18x10-1 S/cm at 300°C, which is one order of magnitude higher than ionic conductivity of pure Na3Sc2(PO4)3. Summarizing, as-obtained heterovalent substituted Na3Sc2(PO4)3 phase can be proposed as a promising solid-state electrolyte for applications working at elevated temperature.



SESSION R4: Fuel Cells and Hydrogen II
Chairs: Ryan O'Hayre and Elsa Olivetti
Wednesday Afternoon, April 15, 2009
Room 2018 (Moscone West)

1:30 PM *R4.1
Materials and the Sustainable Energy Challenge. George Crabtree, Materials Science Division, Argonne National Laboratory, Argonne, Illinois.

The global dependence on fossil fuels is among the greatest challenges facing our economic, social and political future. The uncertainty in the cost and supply of oil threatens the global economy and energy security, the pollution of fossil combustion threatens human health, and the emission of greenhouse gases threatens global climate. Meeting the demand for double the current global energy use in the next 50 years without damaging our economy, security, environment or climate requires finding alternative sources of energy that are clean, abundant, accessible and sustainable. The transition to greater sustainability involves tapping unused energy flows such as sunlight and wind, producing electricity without carbon emissions from clean coal and high efficiency nuclear power plants, and using energy more efficiently. Achieving these goals requires creating materials of increasing complexity and functionality to control the transformation of energy between light, electrons and chemical bonds. Electricity and hydrogen are among the most sustainable energy carriers, for their cleanliness (once produced) their versatility, and their interchangeability. Challenges and opportunities for developing the complex materials and controlling the chemical changes that enable greater sustainability will be presented.


2:00 PM *R4.2
AlN Nanostructures as Potential Hydrogen Storage Materials. Qiang Sun1, Qian Wang2 and Puru Jena2; 1Department of Advanced Materials and Nanotechnology, Peking University, Beijing, China; 2Physics Department, Virginia Commonwealth University, Richmond, Virginia.

Hydrogen, the third most abundant element on earth, has the potential to meet the energy needs of the mobile industry. However, its economical use as an alternate energy has substantial difficulties to overcome. Among these, the most difficult challenge is to find materials that can store hydrogen with large gravimetric and volumetric density and operate under ambient thermodynamic conditions. The Department of Energy's system target for the ideal hydrogen storage material is that the gravimetric density of hydrogen should reach 6 wt % by 2010. In addition, the storage materials should be able to reversibly adsorb /desorb H2 in the temperature range of -20 to 50 C and under moderate pressures (max. 100 atm). The first requirement limits the choice of storage materials to be composed of elements lighter than Al, while the later requires hydrogen binding energies to be between physisorption and chemisorption energies. We have systematically studied the capability of AlN nanostructures (nanocage, nanocone, nanotube, and nanowire) to store hydrogen using gradient corrected density functional theory. In contrast to bulk AlN which has the wurtzite structure and four-fold coordination, the Al sites in AlN nanostructures are un-saturated and have two- and three-fold coordination. Each Al atom is capable of binding one H2 molecule in quasi-molecular form, leading to 4.7 wt % hydrogen, irrespective of the topology of the nanostructures. With the exception of AlN nanotube, energetics does not support the adsorption of additional hydrogen. The binding energies of hydrogen to these unsaturated metal sites lie in the range of 0.1 - 0.2 eV/H2 and are ideal for applications under ambient thermodynamic conditions. Furthermore, these materials do not suffer from the clustering problem that often plagues metal coated carbon nanostructures. References: [1].Q. Sun, Q. Wang, P. Jena, B.V. Reddy, and M. Marquez Hydrogen Storage in Organometallic Structures Grafted on Silsesquioxanes Chemistry of Materials 19, 3074 (2007); [2]. Q. Sun, P. Jena, Q. Wang, and M. Marquez First-principles study of hydrogen storage in Li12C60 J. Am. Chem. Soc. 128, 9741 (2006); [3]. Q. Sun, Q. Wang, P. Jena, and Y. Kawazoe Clustering of Ti on a C60 fullerene and its effect on hydrogen adsorption J. Am. Chem. Soc. (Communication) 127, 14582 (2005); [4]. Q. Sun, Q. Wang, and P. Jena Storage of molecular hydrogen in B-N cage: Energetics and thermal stability Nano Letters 5, 1273 (2005)


3:15 PM R4.3
Microporous Carbon Nitride Spheres and Their Hydrogen Storage Properties. Se Yun Kim1,2, Won Hyuk Suh2, Jung Hoon Choi1, Yoo Soo Yi3, Sung Keun Lee3, Galen D Stucky2 and Jeung Ku Kang1; 1Dept. of Materials Science and Engineering, KAIST, Daejeon, Korea, South; 2Dept. of Chemistry and Biochemistry, University of California, Santa Barbara, Santa Barbara, California; 3School of Earth and Environmental Sciences, Seoul University, Seoul, Korea, South.

Microporous carbon nitride spheres (CNSs) were synthesized from melamine-formaldehyde spheres (MFSs). The carbonization of the MFSs was performed at 400 °C, 600 °C, and 800 °C, and the surface area and pore volume increased as the temperature of carbonization increased. CNS800 (carbonized at 800 °C) had the largest surface area of 995 m2/g and pore volume of 0.50 cc/g. Also, most pores in CNS800 are sub-nanometer size. Since it was theoretically proved that nanopores (< 1 nm) have energy barriers against the penetration of hydrogen molecules through those pores, CNS800 has good potential for use in hydrogen storage; the hydrogen storage capacity of CNS800 is 1.9 wt% under 77 K and 1 atm. The atomic structure of CNS800 was analyzed using 13C MAS NMR without any isotope labeling, and it was determined that CNS800 consists of amorphous and graphite-like carbon atoms that have two or three distinct sp2 carbon bondings.


3:30 PM R4.4
Nanosized (complex) Metal Hydrides for Hydrogen Storage Prepared by Melt Infiltration of Porous Carbons. Philipp Adelhelm, Rene Bogerd, Jinbao Gao, Krijn P de Jong and Petra E de Jongh; Debye Institute for NanoMaterials Science, Utrecht University, Utrecht, Netherlands.

Metal hydrides are promising materials for the future on-board storage of hydrogen, as they allow the storage of large quantities of hydrogen in a small volume at room temperature. Uptake and release of hydrogen can be controlled by altering temperature and pressure (metal hydride <---> metal + H2). However, most of the metal hydrides are thermodynamically too stable and release hydrogen at temperatures that are too high for practical applications. Furthermore, kinetics are often slow leading to hydrogen release/uptake at insufficient rates and often poor reversibility. A promising approach to improve kinetics and possibly to alter the thermodynamics of a metal (hydride) system is to reduce the particle size to the nanometer scale. In this size regime, diffusion limitation is minimized and even changes in the thermodynamic properties of the metal (hydride) can be expected [1]. One route to synthesize nanosized particles is to deposit the desired compound onto a porous support. Recently it was shown that significant improvements in terms of kinetics and reversibility can be obtained this way by depositing e.g. ammonia borane [2] and LiBH4 [3] in porous silica and carbon materials. In this project, we study how kinetics and thermodynamics of the (de)hydrogenation reaction can be influenced by particle size and interaction with the carbon matrix. We discuss MgH2 (7.7 wt% H), MgxNiyHz, NaAlH4 (7.4 wt%), NaH, (4.2wt%), and LiH (12.7 wt%). The nanosized metal hydrides are synthesized by novel melt infiltration technique using nanoporous carbons as support [4]. The size of the nanoparticles can be influenced by using carbons of different porosity. For example, well separated Mg nanoparticles smaller than 5 nm can be synthesized. The metal hydride content can be, depending on the system, as high as 85 wt%. The resulting nanocomposite materials are studied with XRD, TEM and nitrogen physisorption. Hydrogen sorption properties are investigated using thermally programmed desorption, gravimetric and volumetric measurement techniques. The hydrogen release temperatures (under Ar) of the nanocomposite materials are found to be significantly lower compared to bulk materials. For example, the hydrogen release of nanosized-MgH2 starts around 200 °C lower compared to bulk MgH2 (~400 °C). The carbon support additionally contributes to a better thermal conductivity of the overall system, rendering the possibility of improved thermal management to steer the large heat flows that occur during reaction. The results clearly show that melt infiltration of porous carbons is an effective way to synthesize nanosized metal (hydrides) and significant improvements of the hydrogen storage properties are obtained. [1] Wagemans R.W.P. et al, 2005, JACS, 127(47) [2] Gutowska, A. et al, 2005, Angew. Chem. Int. Ed. 44(23) [3] Gross, A.F., J.J. Vajo, et al, 2008, J. Phys. Chem. C, 112(14) [4] de Jongh et al, 2007, Chem. Mater., 19(24)


3:45 PM R4.5
Numerical Analysis and Experimental Verification of the Exothermic Absorption Process for High-density Hydrogen Storage Vessels using TiCrV Metal Hydride Alloy. Sang-kun Oh1, Sung-Wook Cho2 and Kyung-woo Yi1; 1Materials Science and Engineering, Seoul National University, Seoul, Korea, South; 2Korea Institute of Geoscience & Mineral Resources, Daejeon, Korea, South.

The heat formed during the absorption of hydrogen to form metal hydrides for hydrogen storage is a critical factor which affects absorption speed and storage density. It is a particularly important issue for large-scale, high-density storage devices in which the heat produced may raise the system's temperature to unpractically high levels. In this study, we present a hydrogen storage device design based on numerical analysis and experimentally obtained data for the heat from TiCrV hydride generation. The design is focused on the objectives of high volumetric storage density and rapid absorption rates. The generated heat is dissipated through heat conduction via interior cooling fins and convective release. The simulation considers both thermal behavior and gas flow in the system. An experimental device based on the design and modified to allow for obtainment of temperature readings in strategic locations was then constructed. Temperature data from the experimental system was then used to verify the simulations and to construct a more comprehensive numerical model of the heat of hydride formation.


4:00 PM R4.6
Combinatorial Investigation of Mg-Tm (transition metals) Jason Ryan Hattrick-Simpers1, Edwin J Heilweil2 and Leonid A Bendersky1; 1Materials Science Lab, National Institute of Standards and Technology, Gaithersbug, Maryland; 2Physics Lab, National Institute of Standards and Technology, Gaithersbug, Maryland.

A significant amount of time has been devoted to searching for new methods to enhance the kinetics of hydrogen absorption/desorption in Mg, including alloying and structural modifications. Our concept is to use alloying with transition metals that are immiscible in Mg, so that after processing the transition metal forms a fast diffusion path to the nano-size Mg grains. We report on work done in the Mg-Tm (Tm=Cr, Mn, Hf, Zr, Mo, and V) systems. Discrete combinatorial thin film libraries were deposited and annealed in a multi-gun e-beam deposition chamber, which allows up to 12 different elements to be deposited in a single deposition. It will be shown by in-situ IR emissivity measurements that annealing the libraries at different temperatures significantly alters the kinetics of hydrogenation. The microstructure of the films, investigated by X-ray diffraction and transmission electron microscopy, will be discussed in relation to their hydrogen storage properties.


4:15 PM R4.7
Hydrogen Storage Properties of Mg-Ti-H System Prepared by Mechanical Milling Jun Lu1, Zhigang Z Fang1, Young Joon Choi1, Hong Yong Sohn1 and Eva Ronnebro2; 1Metallurgical Engineering, University of Utah, Salt Lake City, Utah; 2Sandia National Lab, Livermore, California.

Magnesium is a very attractive material for hydrogen storage due to its abundance, low cost, high theoretical gravimetric H2 density (7.6 wt %) and high volumetric H¬2 density (110 g/L). However, practical applications are limited by the high dehydrogenation temperature of MgH2 and its slow kinetics. In the present work, we investigated the dehydrogenation/rehydrogenation behavior of Mg-Ti-H system prepared by mechanical milling, which has a theoretical hydrogen capacity of 7.1 wt%. Thermogravimetric analysis (TGA) of as-milled sample indicated that the onset temperature of the dehydrogenation of MgH2 is decreased to about 100 C, compared to that of pure MgH2 (>300 C). Pressure-composition-isothermal (PCI) results showed that the plateau pressure of the reaction involved (MgH2=Mg+H2) is also increased to about 2 bar at 290 C, indicating that the thermodynamic properties have been changed. Temperature-programmed-desorption (TPD) measurements showed that the decomposition of 5 wt% hydrogen occurred in less than 5 min at 290 C, indicating that the desorption kinetics has been improved significantly. The adsorption kinetics has been improved even more significantly with absorbing 5 wt% H2 in less than 50 seconds, measured by temperature-programmed-adsorption (TPA). More importantly, the current system exhibit excellent cyclic stability. There is no hydrogen capacity loss after 120 cyclic measurements at 290 C.


SESSION R5: Poster Session
Wednesday Evening, April 15, 2009
8:00 PM
Salon Level (Marriott)

R5.1
High-rate Discharge Ability and Cycling Performance of Carbon-coated LiFePO4 Cathode Material. Xiaoke Zhi and Guangchuan Liang; Institute of Power Source & Ecomaterials Science, Hebei University of Technology, Tianjin, China.

LiFePO4/C composite cathode materials were synthesized by carbothermal reduction route using inexpensive FePO4 as raw material and glucose as reductive agent and carbon source. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), particle size analysis and charge-discharge test. The results indicated that the carbon generated from glucose does not affect the olivine structure of the cathode materials but considerably improved its high-rate discharge ability and cycle performance. The sample contained 6.3% carbon (sample C6.3) showed high initial specific discharge capacities of 138 and 121 mAhg-1 at 2C and 5C rates, respectively, which is ascribed to the enhancement of the electronic conductivity and reduction of the crystallites size by carbon coating. The sample C6.3 also exhibited excellent cycle performance, whose capacity could reach 135 mAhg-1 at 2C rates after 200 cycles. It is believed that the active materials and electrolyte are separated by carbon coating, thus leading to better stability in the electrolyte and excellent cycling performance of LiFePO4/C cathode materials.


R5.2
The Preparation and Characterization of Olivine LiFePO4/C Doped with Nb2O5 by a Carbothermal Method. Xiaoke Zhi and Guangchuan Liang; Hebei University of Technology, Tianjin, China.

Li0.99Nb0.01FePO4/C composite cathode materials were synthesized by carbothermal reduction route using inexpensive FePO4 as raw material and glucose as reductive agent and carbon source. The microstructure and morphology of the samples were characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). Cyclic voltammetry (CV) and charge/discharge cycling performance were used to characterize their electrochemical properties. The results indicate that mix-doping method does not affect the olivine structure of the cathode but considerably improves its capacity delivery and cycle performance. Among the prepared cathode materials, the sample heat-treated at 750C for 9h showes best electrochemical performances. It shows initial specific discharge capacities of 155 and 120 mAhg-1 with C rates of 0.2C and 5C, respectively, which is ascribed to the enhancement of the electronic conductivity by ion doping and carbon coating.


R5.3
Preparation of Dense Cu(In1-xGax)Se2 Targets by the Mechanochemical Method Deuk Ho Yeon, Hee Jeen Kim, Bhaskar C. Mohanty, Yeon Hwa Jo, Ik Jin Choi and Yong Soo Cho; Materials science and engineering, Yonsei University, Seoul, Korea, South.

This report describes the optimum conditions for preparing single phase and dense pellets of Cu(In1-xGax)Se2 (CIGS), known promising potential candidates for photovoltaic applications. The bulk samples are designed to be used as cost-effective targets for the film deposition techniques such as sputtering and pulsed laser deposition. Fine powder of the CIGS with controlled Ga contents from 0 to 0.3% was successfully synthesized by the mechanochemical method. Numerous parameters, e.g., sintering temperature, duration and annealing ambient, were varied in order to obtain the optimal quality of the resultant pellets. Highly dense and phase pure CIGS pellets were achieved only when the samples were sintered at 600oC for 60 min. Different Ga contents did not change the phase purity but found a noticeable change in lattice constant according to the X-ray diffraction patterns of powders. The highest intensity peak, corresponding to (112) plane, was found to shift towards higher 2θ values (from 26.60 to 26.90) with increasing Ga content, indicating the reduction of unit cell dimensions. Scanning electron microscopy equipped with energy dispersive X-ray analysis was used to study variations in microstructure and relative elemental profiles over the powders prepared according to different synthesis conditions and Ga incorporations.


R5.4
High Energy Density Cathode Materials for Rechargeable Li Ion Power Batteries. Rahul Singhal1, Rajesh Katiyar2, Ricky Valentin2 and Ram S Katiyar1; 1Physics, University of Puerto rico, San Juan, Puerto Rico; 2Mechanical engineering, University of Puerto Rico, Mayaguez, Puerto Rico.

In this work we are going to present some high energy density materials for Li ion rechargeable batteries, e.g LiMn2-xTxO4 (T = Cr, Co, Ni, Al). Stoichiometric compositions of lithium acetate, manganese (II) acetate, and chromium/cobalt/aluminum acetate were separately dissolved in 2-ethylhexanoicacid with continuous stirring and slow heating. After one hour, all solutions were mixed together followed by heating and continuous stirring upto boiling point for 1 hour. The solution was dried and the resulting powder was heated at 450oC for 4h for complete organic removal. Finally, the powder was calcined at 875oC for 15 hr in O2 atmosphere. The resultant powders were structurally characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro Raman scattering. The cathodes were prepared by mixing cathode material, PVDF binder and carbon black in 80:10:10 weight ratio and N-methyl pyrolidon was used as solvent to make slurry and slurry was spread onto Al foil followed by drying at 80oC. The cathode was cut into small circular disc to make the coin cells. The coin cell was fabricated in Ar atmosphere using LiPF6 (dissolved in ethylene carbonate and dimethyl carbonate, 1:1 v/v ratio) as electrolyte and Li foil as anode. The coin cells were electrochemically characterized by cyclic voltammetry (CV) and charge-discharge characteristics. The XRD patterns of LiMn2-xTxO4 cathode materials shows cubic spinel phase structure having Fd-3m space group, where Li+ ions occupy tetrahedral (8a) sites; Mn3+, Mn4+ and Cr+ ions occupy octahedral (16d) sites and O2- reside at (32e). The electrochemical performance of LiMn2-xTxO4 has been studied and the results will be presented. Acknowledgements The above research work was supported by grant received from NASA (NNX 08AB12A).


R5.5
Structure and Properties of the Composite Cathode in La0.6Sr0.4Co0.2Fe0.8O3-La2NiO4+δ System for IT-SOFC. Bok-Hee Kim1, Min Chen2, Byeong-Hwa Moon1, Byung-Guk Ahn1 and Qing Xu3; 1Div. of Advanced Materials Engineering, Chonbuk National University, Jeonju, Jeonbuk, Korea, South; 2Department of Hydrogen and Fuel Cells Engineering, Chonbuk National University, Jeonju, Jeonbuk, Korea, South; 3School of Materials Science and Engineering, Wuhan University of Technology, Wuhan, Hubei, China.

La2NiO4+δ (LNO) and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) are current candidate materials for cathodes of intermediate temperatures solid oxide fuel cells (IT-SOFC) because of their electronic-ionic conducting properties. In this work, (100-x)vol.%LNO-xvol.%LSCF (x=30-70) system composite cathodes have been designed to decrease the thermal expansion of LSCF and increase the electrical conductivity of LNO. The effect of composition on the structure, chemical stability, mixed conducting properties and thermal expansion behaviors of the composite cathodes have been investigated from the viewpoint of seeking for the preferred compositions with both the desired electrical conducting and thermal expansion properties. LSCF powder was synthesized using glycine nitrate process and calcined at 973K for 2hr. LNO powder was prepared by DTPA process and calcined at 1173K for 2hr. The chemical compatibility between the LNO and LSCF at high temperatures has been investigated. X-ray diffraction (XRD) analysis was employed to examine the phase structure of the compositions after sintering at 1673K for 4hr. The results indicated that the XRD peaks of the composites can be assigned to those of the two end members, respectively. No significant solid state reaction product was detected between the two components during the sintering, demonstrating an acceptable chemical compatibility for the LNO and LSCF. A dense structure composing of homogenously distributed constituent phases was observed. It was found that the electrical conducting and thermal expansion properties of the composite cathodes are sensitive to the fraction of LSCF composition. Increasing the relative content of LSCF resulted in a rise of electrical conductivity, a decrease of ionic conductivity and an increase of thermal expansion coefficient (TEC). In terms of both electrical conductivity and thermal expansion properties, the composite cathode containing 50 vol.% LSCF was ascertained to be the optimum composition. This composition offers sufficiently high electrical conductivities above 136 S /cm at 1073K and a moderate thermal expansion coefficient of 14.5×10-6 K-1 averaged between 293 and 1073K, roughly near to the requirement for cathode materials of SOFCs.


R5.6
Inorganic-Organic Hybrid Membranes for Proton Conductor at Intermediate Temperatures. Junji Umeda, Makoto Moriya, Wataru Sakamoto and Toshinobu Yogo; EcoTopia Science Institute, Nagoya University, Nagoya University, Nagoya, Aichi, Japan.

Polymer electrolyte fuel cells (PEFC) are gaining significance because of their high efficiency and low pollution level. However, as their performance degrades at higher temperatures above 100 centigrade, the present PEFCs are designed to operate at around 80 centigrade. Carrying out this operation at low temperatures causes several problems, such as the contamination of Pt anode catalyst by trace amounts of CO present in the fuel gas, low energy conversion efficiency, and heat management problems, etc. Therefore, new proton conducting membranes with a better performance at temperatures above 100 centigrade(an intermediate temperature) are required to solve the current problems and improve the performance of PEFCs. The authors reported the synthesis of inorganic-organic hybrid membranes including chemically bound phosphonic acid groups [1,2]. This paper describes the synthesis of proton conductive inorganic-organic hybrid membranes from alkoxysilanes and derivatives of phosphonic acid. Phosphonic acid groups were incorporated to the membranes as functional molecules for proton conduction. The structures of the hybrid membranes were analyzed by FT-IR and Raman and NMR spectroscopy. 13C and 29Si NMR confirmed that three-dimensional siloxane network was formed in the prepared hybrid membrane by hydrolysis and condensation reactions. DTA-TG analysis showed that these membranes were thermally stable up to 200 centigrade. The proton conductivities of the hybrid membranes increased with phosphonic acid content and temperature up to 130 centigrade. The conductivities of the membrane were 1.0 x 10-1 S cm-1 and 4.5 x 10-4 S cm-1 at 100% relative humidity and non-humidified conditions, respectively, at 130 centigrade. 1. M. Kato, S. Katayama, W. Sakamoto and T. Yogo, Electrochim. Acta, 52, 5924 (2007). 2. M. Kato, W. Sakamoto and T. Yogo, J. Membr. Sci., 303, 43 (2007).


R5.7
Low Temperature Sintering of Sr-, Mg- doped Lanthanum Gallate by Control of Sintering Atmosphere. Jaemyung Chang and Suk-Joong L Kang; MSE, KAIST, Daejeon, Korea, South.

Sr-, Mg-, doped lanthanum gallate is one of the promising solid electrolytes to replace conventional doped zirconia ceramics. However due to higher sintering temperature, the use of this material is limited to the practical application with Ni-based anode using co-firing process. In order to reduce the sintering temperature or a processing temperature of co-firing, many of possibilities have been tried. Our approaches on low sintering temperature of LSGM ceramics is control of ambient atmospheres. Using controlled atmospheres, the sintering temperature of LSGM can be dropped to 1423 K. 4-probe dc electrical conductivity of LSGM sintered in controlled atmosphere is about 0.024 at 873 K. The activation energy is ~ 0.91eV. The possibility of co-firing with Ni-based anode via atmosphere control is also investigated. Dense and Ni-free electrolytes are observed in bi-layer sintered in controlled atmospheres. The detailed description of processing and the possible explanation of enhanced sintering properties will be discussed in this presentation.


R5.8
The Y-substituted BaZrO3 Proton Conductor for Intermediate Temperature Solid Oxide Fuel Cells and Similar Solid State Electrochemical Devices Alejandro Ovalle1, Artur Braun1, Vladimir Pomjakushin2, Antonio Cervellino3, Jan Embs2 and Thomas Graule1; 1Laboratory for High Performance Ceramics, EMPA, Swiss Federal Laboratories for Materials Testing & Research, Duebendorf, Switzerland; 2Laboratory for Neutron Scattering, Paul Scherrer Institute, Villigen, Switzerland; 3Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland.

Energy efficiency plays an increasing role in addressing energy and environmental sustainability of our society. While fuel cells are increasingly move to the center of attention, the high temperature solid oxide fuel cells are still troubled because of high temperature related, malign issues. Reduction of the operation temperature from 800°C to 500°C would be a major progress in SOFC technology, and is generally possible by using proton conducting ceramics, but the search for a proton conductor that can perform well at such low temperature is an ongoing quest. This is also because the relation between materials properties and proton conductivity is fundamentally not yet well known. We apply quasi elastic neutron scattering and other neutron, synchrotron and electrochemical methods for basic studies on proton conductors in order to improve the understanding of proton phonon coupling on the molecular scale.


R5.9
Highly Faceted Multioctahedral Pt Nanocrystals as Oxygen-Reduction Electrocatalysts with Enhanced Durability. Byungkwon Lim and Younan Xia; Biomedical Engineering, Washington University, St Louis, Missouri.

Fuel cells represent one of the most important forms of environmentally benign energy sources. Despite the considerable advances in fuel cell technology in recent years, certain key issues still need to be addressed. For oxygen reduction reaction (ORR) on the cathode of low temperature fuel cells, durability of the Pt-based electrocatalysts has been identified as one of the major concerns since poisoning and loss of electrochemical active surface area (ECSA) over time are the primary sources of decay in efficiency. Here we present a simple wet chemical route to the synthesis of highly faceted Pt nanocrystals with a large number of interconnected arms in a quasi-octahedral shape. In this work, the multioctahedral Pt nanocrystals were synthesized by reducing H2PtCl6 precursor with poly(vinyl pyrrolidone) in aqueous solutions containing a trace amount of FeCl3. The iron species (Fe3+ or Fe2+) play a key role in the formation of the multioctahedral structure by decreasing the reduction rate and thus inducing the overgrowth of Pt seeds along their corners. Electron microscopy studies revealed that most of the exposed facets on the multioctahedral Pt nanocrystals are {111}, along with the presence of a large number of edge and corner sites. The size of the Pt multioctahedrons can be controlled by varying the concentration of FeCl3 added to the reaction and/or the reaction temperature. These multioctahedral Pt nanocrystals were tested as electrocatalysts for the ORR in a proton exchange membrane (PEM) fuel cell. In the accelerated durability tests at room temperature, 20-nm Pt multioctahedrons only showed a slight loss of 5.7% in ECSA after 4000 cycles, but a significant loss of 34% in ECSA was observed for Pt/C catalyst (20 wt% 3.2-nm Pt nanoparticles on Vulcan XC-72 carbon support; E-TEK), demonstrating the higher durability of multioctahedral Pt nanocrystals compared to commercial Pt/C catalyst. The improved durability of Pt multioctahedrons can be attributed to the unique morphology, i.e., a highly branched structure consisting of interconnected octahedral arms, and absence of carbon support. In addition, the 20-nm Pt multioctahedrons showed the specific activity that was 2.7 times higher than that of Pt/C catalyst, presumably due to the preferential exposure of {111} facets on their surfaces.


R5.10
Synthesis and Electrical Properties of Non-fluorinated Diblock Copolymer Based on Poly(arylene sulfone ether ketone) and Poly(sulfonated styrene-co-acrylonitrile) for Polymer Electrolyte Membrane Fuel Cell. Tae Ann Kim and Won Ho Jo; Material Science and Engineering, Seoul National University, Seoul, Korea, South.

The perfluorinated ionomer membrane, Nafion®, has been the most widely used membrane for fuel cell due to its high proton conductivity and chemical stability. However, the proton conductivity of Nafion® falls off rapidly at high temperature (above 100 °C) due to decrease of relative humidity which perturbs the formation of proton conduction channel. Furthermore, the low glass transition temperature (80- 120 °C) of Nafion may also induce the loss of mechanical property and dimensional stability at high temperature. Operation at higher temperatures provides several benefits including: (i) improved tolerance of the Pt catalyst to contaminants, (ii) accelerated reaction kinetics at anode and cathode, (iii) facilitation of water management, and (iv) alleviation of the cooling system. There have been many efforts to synthesize new membranes which show less dehydration at elevated temperature and maintain high mechanical properties and dimensional stability. One of the approaches is the use of hydrocarbon like aromatic polyether, because the aromatic hydrocarbon has high thermal, mechanical properties and low production cost which are critical properties for polymer electrolyte membrane. Nevertheless, the proton conductivity of membrane based on aromatic hydrocarbon is still low due to its poor phase-separation. In this study, we have designed and synthesized novel diblock copolymers comprising of poly(arylene sulfone ether ketone) and poly(sulfonated styrene-co-acrylonitrile) by two step synthesis: first, the hydrophobic part of diblock copolymers, poly(arylene sulfone ether ketone) (PASK), was synthesized by step-growth polymerization, and then the chain end of PASK was modified to generate an initiating site for atom transfer radical polymerization (ATRP). The hydrophilic part as the second block was polymerized through ATRP of acrylonitrile and sulfonated styrene. We changed the hydrophobic/hydrophilic chain length ratio and the degree of sulfonation to optimize the phase-separated morphology for giving the highest proton conductivity, since diblock copolymers have various self-assembled nanostructured morphologies (spherical, lamellar or cylinder) depending upon the block length ratio.


R5.11
Synthesis and characterization of Mixed Conducting Oxide Cathodes for Intermediate Temperature Solid Oxide Fuel Cells Ki Woog Song, Ki Tea Lee, Jong Yeol Yoo and Chun Kang Jo; advanced Materials Engineering, Chonbuk National University, Jeonju, ChollaBukDo, Korea, South.

The Mixed Conducting oxide of a perovskite-related compound, Ba0.5Sr0.5Co0.8Fe0.2O3-δ, has been investigated as cathode materials for intermediate temperature solid oxide fuel cells. In this study, we doped a variety of elements with desirable quantities such as Cu, Ni, Fe and Co at B site in Ba0.5Sr0.3CoO3-δ of a perovskite crystal structure. The cathode powder was synthesized by a glycine nitrate process (GNP) and a citrate-EDTA complexing method, and calcined at appropriate temperatures for each powder. The structural and morphological properties of the cathode powder were analyzed by XRD, SEM and FESEM. The electrical conductivity was measured using a four-prove DC method from 200 to 800 degree C with 50 degree C increments. Electrolyte supported symmetric cells for Ba0.5Sr0.5MO3-δ cathode materials and half cells with three-electrode configuration in order to separate and monitor polarization resistance(Rp) of cathodes were fabricated by screen printing on the GDC electrolyte, and the electrochemical performance were estimated with AC impedance spectroscopy at 400 to 800 degree C. The Rp of the cathode materials with respect to a number of doped elements at B site in Ba0.5Sr0.3MO3-δ is reported.


R5.12
Synthesis of YSZ by Emulsion Precipitation Method and its Impedance Study. Yun Ho Yang, Manasa Kumar Rath, Susant K Acharya and B. G Ahn ; Major Electronic Materials Engineering, Chonbuk National University, Jeonju, Cholla Buk Do, Korea, South.

As it is well know that the microstructures of materials affect the performance of the SOFC. 8YSZ (electrolyte) was synthesized by emulsion precipitation followed by heat treatment. Nano-set ball milling of the powder was carried out in ethanol media. The phase and morphology of the powder were analyzed by XRD, SEM, and FESEM. YSZ pellet were prepared (99% of theoretical density) by cold iso-static uniaxial pressing with varying thickness, BSCF (Ba0.5Sr0.5Co0.8Fe0.2O 3-δ) cathode were coated on the pellets by screen printing process. Impedance spectroscopy was carried out at the temperature range 400~ 800 C of the symmetry cell and the half cell configuration. Impedance measurement data were collected using different suitable circuit elements and plotted for analysis. The Arrhenius plot for the YSZ pellet for the symmetry cell configuration shows that the microstructures have an effect on the conductivity.


R5.13
Fabrication of Nanomodified Anodes for Power Density Enhancement of Microbial Fuel Cells. Rebecca Filardo Schaller1, Yanzhen Fan2, Shoutao Xu2, Hong Liu2 and Jun Jiao1; 1Physics, Portland State University, Portland, Oregon; 2Biological and Ecological Engineering, Oregon State University, Corvallis, Oregon.

Microbial fuel cells (MFCs) use microorganisms to simultaneously break down organic materials and generate electricity. One of the greatest challenges in the practical application of MFCs is to sufficiently increase their power generation. Nanomodified graphite carbon anodes were prepared for use in MFCs to enhance the electron transport from the microbes to the electrode. Nanomodification to the anodes included growth of nanoparticles, multi-walled carbon nanotubes (MWCNTs), and nanorods. Nanoparticles of various metals, including Au, Ni, Pd, and Fe, were synthesized through thermal annealing; Fe Catalyst MWCNTs were synthesized through chemical vapor deposition; and ZnO nanorods were synthesized through thermal chemical bath deposition. Power density was measured in MFCs for each type of nanomodified electrodes. Significant increase in power density was observed for the MFC with anodes decorated with MWCNTs (with 50-100nm diameters).


R5.14
Microwave Assisted Syntheses of Stable Solvent Based Colloidal Sols of Tailored Ceria Nanoparticles. Olivier J Poncelet1, Julien Jouhannaud1 and Denis Chaumont2; 1L2T/LITEN, CEA Grenoble, Grenoble, France; 2UMR5209 CNRS, Université de Bourgogne, Dijon, France.

The pressure of environmental laws in many advanced countries becoming more restricting year after year, it is asked to automobile companies to strongly control the carburant consumption of cars that they put on the market and also to eliminate toxic chemicals coming from exhaust emission gases. This is particularly true for diesel oil which is particularly efficient in terms of carburant consumption but known to release toxic chemicals in exhaust gases. Among the materials able to solve these concerns, ceria (CeO2) is a choice catalyst because it can work in two different ways first as an oxygen store by release of oxygen in the presence of reductives gases (CnHn and CO), and also by removing oxygen by interaction with oxidising species (NOx), leaving finally in exhaust gases H2O, CO2 and N2. To be efficient ceria has to be used under nanoparticle form directly added in the diesel oil. The surface developed by the nanoparticles due to their small size positively influence the catalytic properties (both oxidation and reduction step) in terms of kinetic, so the ignition delay time for nanosized particles in the combustion chamber of diesel motors fits well with the high performance diesel motor characteristics. The true challenge is to be able to prepare stable solvent based sols of crystalline ceria nanoparticles which could be used without plugging the injection nozzles. We present various synthetic ways to produce ceria nanoparticles in water followed by their surface modification allowing stable colloidal sols in organic medium to be designed. We emphasize more particularly the microwave assisted synthesis which by enhancing nucleation of the nanosized particles versus growth of nanoparticles allows very narrow sized distribution of nanoparticles to be obtained. Moreover in terms of synthetic processes, microwave assisted syntheses allow to strongly reduced the synthetic time without compromise in terms of cristallinity (TEM and XRD). Surface modifications of the nanoparticles have been monitored by FT-IR, FT-Raman, while their sizes have been monitored by DLS (differential light scattering) from water to solvents suspension proving the efficiency of ether carboxylic acids as surface modifiers. Finally we will show preliminary results on the microwave assisted syntheses of mixed oxides materials (CeZrOx) and the way to design organic based sols of nanoparticles.


R5.15
Effect of Electropulsing Treatment on Texture Development of Cold Rolling AZ31 Strip. Guan Lei and Tang Guoyi; Advanced Materials Institute, Graduate School at Shenzhen, Tsinghua University, Shenzhen, China.

The effect of electropulsing treatment (EPT) on texture development of cold rolling AZ31 strip was investigated with the help of light microscopy and X-ray diffraction technique. Several processing parameters such as thickness reduction per pass and frequencies of electropulsing were varied. Microstructure and texture were measured on specimens subjected to EPT experiments of different frequencies. Grain refinement was found to occur actively during EPT, producing a very fine grain size of ~9μm after high frequency EPT in the condition of large reduction in single pass. It was found that EPT weakens the basal plane texture in different extent according to the amount of reduction per pass. To the large reduction, as increasing the frequencies of electropulsing, EPT can decrease the pole intensity of basal plane by making the basal orientation titling 45°~60° to the normal direction around the RD and by increasing the amount of prism planes parallel to rolling plane. To the small reduction, EPT can weaken the pole intensity of basal plane in the same way as to the large reduction at the low frequency, whereas EPT sharpens the basal plane texture as the frequencies of electropulsing increased.


R5.16
Pseudo Capacitance of Nano Structured Metal Oxide Films in Gas Phase. Ilia Kiselev1, Vyacheslav Musatov2 and Martin Sommer1; 1The Institute for Microstructure Technology, Forschungszentrum Karlsruhe, Karlsruhe, Germany; 2Saratov State Technical University, Saratov, Russia.

Metal oxide structures have been established themselves distinctly in super- and pseusdocapacity investigations and developments. Still, for them as well as for other employed materials, the usable region of voltage is limited to a few volts only. Contrary, in this report we present results concerning supercapacitor properties using higher voltages, which could be applied due to the use of metal oxide films in gas atmosphere. Originally designed for gas sensing applications, complex structures with metal oxide films as active components show the capacitive characteristics, which match good to those of super/pseudocapacitors. Very probably, moderate changes in the design of these structures may lead to improved supercapacitor properties, especially very high power densities. The structures used in this study are composed basically on surface-oxidized Si substrates with an active layer of about 150 nm thick nano-structured film on the top of it. Contact electrodes and heaters are sputtered Pt stripes of about 80 μm width and 1 μm thickness. The heaters are located on the rear side of the substrate. The working area is 4x8 mm. The working temperature was 300°C, while operating gas in contact with the film was synthetic air with a relative humidity of 50%. SnO2 + (1%)Pt and WO films have been prepared using sputtering and sol-gel procedures. Positive voltages to ground in the range of 5-50V have been applied and removed step-wise on the Pt electrodes and the resulting currents were recorded. As first result, we observed the charging and discharging currents as dissymmetrical. The best capacitive characteristics were found with the SnO2 films on Si substrates. The accumulated energy density amounted to 25 W*h/kg, the power density at discharge till 90% was about 5*103 W/kg, the specific capacitance was ~10 F/g. Dependencies of the charging characteristics on the film composition, structure and production procedures as well as variations of the characteristics depending on air humidity and operating temperatures have been analyzed. Also the dependence on the O2 concentration in the gas phase was investigated. Because in the case of supercapacitance the ions accumulated at the metal oxide surface would provide an enormously high level of depletion in the film and would drive it to a non-conducting state, which wasn’t observed in this study, we assume mostly pseudocapacitance instead of double-layer capacitance for our investigated structures.


R5.17
Reversible Solid State Capture and Storage of Carbon Dioxide with Hydroxylated Amidines Myung-Sook Kim and Ji-Woong Park; Department of Materials Science and Engineering, Gwangju Institute of Science and Technology, Gwangju, Korea, South.

Amidines are known to react with carbon dioxide in the presence of water or alcohol to form amidinium bicarbonate salts. The carbonated amidine can be reverted to the decarbonated form by heating [1]. 1,8-Diazabicyclo[5.4.0]-undec-7-ene (DBU) is an amidine capable of well-cotrolled, reversible carbon dioxide capture and release. In this study, we modified the structure of DBU so as to capture and release carbon dioxide in the solid state. We synthesized hydroxylated DBU (HODBU) derivatives. This novel HODBU could capture carbon dioxide gas effectively in the absence of solvents stoichiometrically. The HODBU was mixed with dry silica particles to form powdery carbon dioxide scrubber, which can help to release the heat of reaction and to capture carbon dioxide faster by increasing surface area. The carbon dioxide-capture/release property of various HODBUs and their mixtures with silica particles was studied by nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. HODBU carbonate salt was thermally stable at ambient temperature if it is tightly sealed. The HODBU carbonate salts are potentially useful as a quantitative solid state carbon dioxide source. Acknowledgement: This work was supported by the Program for Integrated Molecular Systems (PIMS) at GIST in Korea. [1] Jessop PG, Heldebrant DJ, Li X, Eckert CA, Liotta CL., Nature (2005) 436, 1102.


R5.18
Abstract Withdrawn


R5.19
Purification of Refined Metallurgical-grade Silicon up to Solar Grade Silicon by Extraction. Sergey Karabanov1,2, Dmitriy Suvorov1,2 and Boris Sazhin1; 1Ryazan Metal Ceramics Instrumentation Plant JSC, Ryazan, Russia; 2Ryazan State Radio Engineering University, Ryazan, Russia.

Nowadays due to intensive development of photovoltaics it is important to find new methods of industrial silicon purification to obtain solar-grade silicon for solar cell production. These new methods are to be not only economically efficient but also ecologically safe. The ecologically safe methods are based on liquid and gas extraction of impurities from silicon melt, recrystallization, oriented crystallization, vacuum refining, etc. The present paper analyzes theoretically silicon purification by extraction from fine-dyspersated solid phase. In comparison with traditional purification methods, the examined method has a few advantages: chemically active and ecologically dangerous substances are not used during purification; there is no phase transition of silicon being purified and its chemical compounds are not formed. Besides, one of the method advantages is its relatively simple hardware. The essence of the method is in extractive processing of metallurgical-grade silicon by a substance-extractant at high (more than 1200°C)temperature. Before the extractive processing the metallurgical-grade silicon was powdered up to 10-80 micron and pretreated by chemical methods. If the impurity concentration in the substance-extractant is less than in silicon particles (the necessary purification condition), the diffusion of silicon impurities, to the particle surface and their further solution in substance-extractant takes place. Mainly, the purification efficiency is limited by the particle size and the impurity diffusion coefficient which strongly depends on temperature. The work represents the mathematical model of impurity diffusion with the assumption of spherical geometry of silicon particles. Diffusion of the basic impurities determining the quality of solar-grade silicon (boron, phosphorus, aluminum, carbon, iron, copper) has been taken into account. Using the model we have obtained axial profile impurity concentration in silicon particles at the various points of time, the time dynamics of average impurity concentration at various purification conditions (temperature, particle size, impurity concentration in extractant). On the basis of simulation data the requirements to the technological purification mode when acceptable time and purification efficiency is reached have been determined. Thus, the mathematical modeling method shows the possibility of extraction use for silicon purification in industrial scale. The design of industrial-scale plants for extractive purification process realization is shown schematically.


R5.20
Influence of Cu for Ca on Thermoelectric Properties of Ca3-xCuxCo4O9 (0≤x≤0.3) Kyeongsoon Park1, J. W Choi1, S. W Nam1, M. H Heo1 and W. S Seo2; 1Sejong University, Seoul, Korea, South; 2Korea Institute of Ceramic Engineering and Technology, Seoul, Korea, South.

Thermoelectric materials with high energy conversion efficiency are strongly required for both electric power generation in terms of waste heat recovery and the refrigeration of electronic devices. Metallic oxides have been recognized as good candidates for applications in power generation because of their excellent thermal and chemical stability, ease of manufacture and low manufacturing cost. Nanocrystalline Ca3-xCuxCo4O9 (0≤x≤0.3) powders were prepared by combustion process. The as-sintered Ca3-xCuxCo4O9 samples consisted of plate-like grains and showed a monoclinic symmetry. For the Ca3-xCuxCo4O9 samples, higher Cu content yielded a higher density and a larger grain size. The thermoelectric properties were measured in the temperature range of 723-1073K. The added Cu gave rise to a significant increase in the high-temperature electrical conductivity because the added Cu increased the density, the grain size, and the hole concentration of the system. The sign of the Seebeck coefficient was positive over the measured temperature range, indicating that the major conductivity carriers were holes. In this study, we obtained enhanced high-temperature thermoelectric properties by adding Cu for Ca in Ca3Co4O9.


R5.21
Microstructure and Thermoelectric Properties of Cu-added Na(Co1-xCux)2O4 (0≤x≤0.2) Thermoelectric Compounds Kyeongsoon Park1, S. W Nam1, J. W Choi1, M. H Heo1 and W. S Seo2; 1Sejong University, Seoul, Korea, South; 2Korea Institute of Ceramic Engineering and Technology, Seoul, Korea, South.

Thermoelectric power generation converts thermal energy directly to electrical energy via the Seebeck effect. Oxide-based materials are regarded as a candidate for power generation because they are chemically and thermally stable as well as highly oxidation resistant in air at high temperatures. The Na(Co1-xCux)2O4 (0≤x≤0.2) thermoelectric samples had a bronze-type layered structure. A small amount of NaCuO2 phase was observed at the Na(Co1-xCux)2O4 (x=0.15 and 0.2) samples with high Cu content. The density and grain size of the sintered Na(Co1-xCux)2O4 samples increased with an increase in Cu content. The sintered Na(Co1-xCux)2O4 bodies showed plate-like grains. The electrical conductivity decreased with an increase in temperature, i.e., metallic behavior. The Seebeck coefficient increased with increasing temperature. The Cu-added Na(Co1-xCux)2O4 showed much higher electrical conductivity and Seebeck coefficient compared to Cu-free NaCo2O4. The microstructure and thermoelectric properties of the Na(Co1-xCux)2O4 samples were discussed, depending on Cu content. We demonstrate that Cu-added Na(Co1-xCux)2O4 (0≤x≤0.2) could be promising for power generation at high temperatures.


R5.22
Effect of Substrate Temperature on the Molecular Orientation of Subphthalocyanine Thin Film Chi-Ta Chou1, Wei-Li Tang1, Chin-Hsin J Liu1, Kuei-Hsien Chen2 and Li-Chyong Chen3; 1Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan; 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan; 3ICenter for Condensed Matter Science, National Taiwan University, Taipei, Taiwan.

Boron subphthalocyanine chloride (SubPc-BCl) is a p-type organic semiconductor with the highest occupied molecular orbital (HOMO) higher than that of copper phthalocyanine (CuPc), thus resulting in a higher open circuit voltage (Voc) for the bi-layer organic photovoltaic device.The efficiency will be increased by the ordered organic film. SubPc-BCl thin films were deposited by vacuum thermal evaporation technique, and morphology of the film was controlled with various substrate temperatures. The films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The XRD pattern shows two diffraction peaks, (221) and (122), and the intensity ratio (221)/(122) increases with increasing substrate temperature. A molecular orientation model indicates that the construction of the (122) plane requires the existence of some disordered SubPc molecules. From AFM, the 2D growth mode was found for the SubPc film deposited at room temperature, 3D growth mode for that at 120 degree C, and 2D+3D mode for that at 70 degree C and 100 degree C.


R5.23
Electrical Properties and Crystallographic Characterization of Ho2O3 Doped BI2O3 Polymorphs. Mehmet Bozoklu1, Semra Durmus1, Meral Gokkoyun1, Selma Erat2,3, Artur Braun2, Hulya Metin4 and Mehmet Ari1; 1Department of Physics, University of Erciyes, Kayseri, Turkey; 2Empa, - Swiss Federal Laboratories for Materials Testing & Research, Dubendorf, Switzerland; 3Department for Nonmetallic Inorganic Materials, ETH Zurich, Zurich, Switzerland; 4Department of Physics, University of Mersin, Mersin, Turkey.

The main aims of this study are to determine new phases of bismuth trioxide holmium trioxide binary system and the temperature dependence of the electrical transport properties. The reaction products obtained in an open air atmosphere were characterized by x-ray powder diffractions (XRD) and the unit cell parameters were calculated from the diffraction patterns. The α+β-Bi2O3, β-Bi2O3 and β+δ-Bi2O3 crystal system were obtained by doping 0,01< %Ho2O3 <0,02 mole, 0,02< %Ho2O3 <0,09 mole and 0,09< % Ho2O3 <0,1 mole, respectively. Thermal behavior and thermal stability of the phases were investigated by using thermal analysis techniques. Surface and grain properties of the related phases were determined by making SEM analysis. The empirical formula of the synthesized solid solutions was determined by elemental analysis. The temperature dependence of the electrical properties of β-Bi2O3 solid solution was measured by using four point probe method.


R5.24
Electrical Properties and Crystallographic Characterization of Gd2O3 Doped BI2O3 Polymorphs. Semra Durmus1, Mehmet Bozoklu1, Meral Gokkoyun1, Selma Erat2,3, Artur Braun2, Hulya Metin4 and Mehmet Ari1; 1Department of Physics, University of Erciyes, Kayseri, Turkey; 2Empa, - Swiss Federal Laboratories for Materials Testing & Research, Dubendorf, Switzerland; 3Department for Nonmetallic Inorganic Materials, ETH Zurich, Zurich, Switzerland; 4Department of Physics, University of Mersin, Mersin, Turkey.

The main aims of this study are to determine new phases of bismuth trioxide gadolinium trioxide binary system and the temperature dependence of the electrical transport properties. The reaction products obtained in an open air atmosphere were characterized by X-ray powder diffractions (XRD) and the unit cell parameters were calculated by using the diffraction patterns. The α+β-Bi2O3, β-Bi2O3 and β+δ-Bi2O3 crystal system were obtained by doping 0,01≤ %Gd2O3 ≤0,02 mole, 0,02≤ %Gd2O3 ≤0,07 mole and 0,08≤ %Gd2O3 ≤0,15 mole (at 750oC), respectively. The α+β-Bi2O3, β-Bi2O3 and δ-Bi2O3 crystal system were obtained by doping 0,01≤% Gd2O3≤0,04 mole, 0,05≤ %Gd2O3 ≤0,08 mole and 0,09≤ %Gd2O3 ≤0,15 mole (at 760oC,quench), respectively. The α+β-Bi2O3 and δ-Bi2O3 crystal system were obtained by doping 0,01≤ %Gd2O3 ≤0,08 mole, 0,09≤ %Gd2O3 ≤0,15 mole (at 810oC, quench), respectively. Thermal behavior and thermal stability of the phases were investigated by thermal analysis techniques. The temperature dependence of the electrical properties of β-Bi2O3 solid solution and of δ-Bi2O3 solid solution was measured by four point probe method.


R5.25
Charge Transfer in LSF-Ni System Monitored by Core Level Soft X-ray Absorption Spectroscopy of Oxygen. Selma Erat1,2, Artur Braun1, Alejandro Ovalle1, Zhi Liu3, Ludwig J. Gauckler2 and Thomas Graule1,4; 1Empa, - Swiss Federal Laboratories for Materials Testing & Research, Dubendorf, Switzerland; 2Department for Nonmetallic Inorganic Materials, ETH Zurich, Zurich, Switzerland; 3Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California; 4Technische Universität Freiberg, Freiberg, Germany.

We work on the crystallographic and electronic structure, and transport properties of a complete matrix of LaSrFeNi-oxides (which are potentially promising cathode material for the solid oxide fuel cells) including its end members LaFeO3, SrFeO3-delta, LaNiO3-delta, and SrNiO3-delta. The samples with La1-xSrxFe0.75Ni0.25O3-delta show different conductivity at room temperature possible due to either crystallographic phase transformation or electronic structure changes depending on the stoichiometry. In order to determine the crystallographic structure and monitor the phase transformation we performed neutron diffraction. For the electronic structure, we measured oxygen K edge absorption spectra which give information about metal 3d, as well. The strong hybridization between the iron 3d and oxygen 2p shown in the spectra favors the charge transfer from oxygen 2p to iron 3d which can affect the conductivity. The charge transfer is shown by the growing pre-peak in the spectra. There are two differences in the pre-peak depending on the stoichiometry. One is increasing the peak intensity the other is shifting to Fermi energy with increasing the Sr content up to 50%. Over this Sr content peak intensity starts to decrease and shifts to lower energy.


R5.26
Development of Bottom ash Block for control Surface Temeperature of Pavement and Non-point Source Pollution. Jong-Bin Park1, Sang Ho Lee2, Ree Ho Kim2 and Hee Bum Pyun1; 1Environment Research Division, Korea Institute of Construction Technology, Goyang, Gyeonggi-Do, Korea, South; 2Advanced Environment Technology Research Division, Korea Institute of Construction Technology, Goyang, Gyeonggi-Do, Korea, South.

Permeable pavement systems to alleviate urban heat island phenomena are suitable for a variety of residential, commercial and industrial applications, yet are confined to light duty and infrequent usage. And Most of study for the permeable pavement is limited to asphalt pavement. Also, immense quantities of coal combustion by-products are produced every year, but only a small fraction of them are currently utilized, particularly bottom ash which is used in this study. In this study, we aimed at the development of new permeable and water absorbing pavement blocks. Optimum conditions for compressive strength and water absorption, volume of water retention and porosity characteristics were investigated for production of the pavement blocks from bottom ash. In addition, removal efficiencies of pollutants in road runoff by the pavement blocks were compared under various conditions. Experimental results showed that the compressive strengths and water absorption after 28days for blocks were 12~15MPa and 18%, respectively. Also, turbidity and heavy metals in rainwater were successfully removed. So, further study on the durability test such as the effect of surface fouling by dust is possibly needed prior to use the new bricks as construction materials.


R5.27
Synthesis of Platinum Cube & Hexapod Nanostructures via Modified Polyol Process. Sang-Beom Han, Kyung-Won Park and Choonkoo Zho; Chemical and Evironmental Engineering, Soongsil University, Seoul, Korea, South.

We prepared Pt nanocube catalyst with about 3.6 nm in size by a polyol process in the presence of PVP as a stabilizer and Fe ion as a kinetic controller. The crystal structure of Pt nanocube with {100} faces was confirmed by field-emission transmission electron microscopy. In a cyclic voltammogram, we found that the Pt nanocube catalyst showed relatively high ratio of the forward anodic peak current to the reverse anodic peak current resulting in less accumulation of residues on the catalyst. The Pt nanocube catalyst with the edge of stepped {100} faces was preferable to breakage of CH3OH and CH3CH2OH compared to polycrystalline Pt nanocatalyst. In an electrochemical measurement for methanol and ethanol electrooxidation, the Pt nanocube catalyst showed an excellent catalytic activity, i.e., lower onset potential and higher current density, compared to the polycrystalline Pt nanocatalyst. We prepared Pt hexapod nanoparticles with 6.4 ~ 9.7 nm in size by a polyol process in the presence of PVP as a stabilizer and inorganic ion as a kinetic controller. The structure and morphology of Pt nanostructures were confirmed by field-emission transmission electron microscopy. Morphological control over platinum nanoparticles was achieved by varying the amount of seeds added to a polyol process, where platinum precursor was reduced by ethylene glycol to form Pt nanoparticle at 150 °C. As volume ratio between precursor-solution and seed-solution was increased from 10 to 50, the shape of Pt nanostructures was evolved from small seeds to tripod and hexapod. In addition, the size-controlled platinum hexapodnanostructures were successfully obtained using seeding method.


R5.28
Polymer Composites of Carbon Nanotube as Counter Electrode of Dye-sensitized Solar Cells. Benhu Fan, Xiaoguang Mei, Kuan Sun and Jianyong Ouyang; Materials Science and Engineering, National University of Singapore, Singapore, Singapore.

Polymer composites of carbon nanotube can be prepared by a solution processing, such as spin-coating. The composites were used to replace the precious platinum as the counter electrode of dye-sensitized solar cells. The devices exhibited high performance with the energy conversion efficiency of 6.5%, short-circuit current of 15.5 mA cm^-2, open-circuit voltage of 0.66 V, and fill factor of 0.63. This performance is close to the devices using conventional platinum as the counter electrode.


R5.29
Optimizing TiO2 Electrodes for Dye-Sensitized Solar Cells Xiaojuan Fan, Physics, Marshall University, Huntington, West Virginia.

Dye-sensitized solar cells DSSCs provide next generation, low cost, and easy fabrication photovoltaic devices based on organic sensitizing molecules, polymer gel electrolyte, and metal oxide semiconductors.1,2 One of the key components is titanium dioxide in porous structure enabling high surface area to attach more dye molecules. We report a rapid and low cost method to fabricate nanorod array TiO2 thin films used as photo electrodes for solid-state DSSCs.3 Poly(methylmethacrylate) (PMMA) gel is blending with titanium alkoxide to form a precursor. As-coated TiO2/PMMA wet thin film is against to a micro-nanorod featured PDMS master stamp. After curing, PDMS can be peeled off without damage. The final thermal removal of polymer leads to a smooth, crack-free, and large area nanorod structured TiO2 thin film. The vertically aligned nanorod array of TiO2 electrode is sensitized with a dye and filtrated with an ionic gel polymer electrolyte followed by a counter electrode to form an array of sub-cells connected in parallel. The new architecture DSSCs are expected to significantly enhance the energy conversion efficiency compared to the traditional planar thin film solar cells. *Corresponding author, email: x.fan@marshall.edu References: 1 B. Oregan and M. Gratzel, Nature 353 (6346), 737 (1991). 2 X. J. Fan, D. P. Demaree, J. M. S. John et al., Applied Physics Letters 92 (19), 193108 (2008). 3 M. Law, L. E. Greene, J. C. Johnson et al., Nature Materials 4 (6), 455 (2005).


R5.30
Next Generation of Phase Change Composites for Thermal Storage in Solar Steam Electrical Plants. Milka Markova Hadjieva1, Metodi Bozukov1 and Tsenka Tsacheva2; 1Central laboratory of Solar Energy, Bulgarian Academy of Sciences, Sofia, Bulgaria; 2Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria.

The new generation of modified phase change material (PCM) composite is elaborated for utilizing both, a high thermal capacity of the NaNO3/KNO3 eutectics and a good thermal conductivity of the graphite matrix. The form of containment to prevent leakage of the liquid phase change material is another function of a graphite matrix. Particle porosity and larger specific surface are intended to avoid a salt clusters formation during solidification alongside the heat flow exchange improved. An extensive study on structural and thermal behavior of the modified PCM was carried out for NaNO3/KNO3/graphite composite samples, structured through different manufacturing routes with variety graphite content (10-30 wt%). Thermophysical data, collected by DSC and thermal cycling methods, include the composite phase transition temperatures from 215 to 2600C and thermal storage capacity of 75-88 [kJ/kg]. The NaNO3/KNO3/graphite crystallization process, responsible for heat released, was studied by LINKAM thermal microscopy, scanning electron microscopy (SEM). The precise imaging allowed identification of the adhesive bonding development among surfaces of salt and graphite matrix. The spectral FTIR study, performed before and after the composite re-crystallization, did not register additional functional groups due to chemical destruction. The elemental characterization of the composite surface by the use of X-ray microanalysis (EDS) method specified a few areas of Na-rich spherical masses and the K-rich layered structure on the graphite plane. As the areas of inhomogeneous elemental distribution influence thermal stability of the salt/graphite composite structure, the research focus on solidification/nucleation process is obvious and planned for controlling the composite structural stability during repeatable thermal cycling process. The correlation between morphology and thermal storage capacity allowed selection of the NaNO3/KNO3/graphite composite samples with optimal thermal storage behavior. Applicability of the new generation modified PCM composite to the high temperature thermal storage process would increase energy efficiency of saturated and superheated steam commercial plants through accumulating and use the waste heat.


SESSION R6: Batteries
Chairs: Ryan O'Hayre and Phil Parilla
Thursday Morning, April 16, 2009
Room 2018 (Moscone West)

8:00 AM *R6.1
Present Status of Energy Storage for Portable and Stationary Application: Materials Limitations. M. Stanley Whittingham, Chemistry and Materials, SUNY, Binghamton, New York.

Energy storage is the limiting technology for renewable energy, such as wind and solar, and particularly for the next generation of hybrid electric vehicles, the plug-in hybrid electric vehicle (PHEV). If long-lived, low cost and safe batteries or capacities are to be developed, the materials limitations must be overcome. This presentation will discuss the present status of batteries and related pseudocapacitors.


8:45 AM R6.2
Evaluating System Approaches to Alkaline Battery Recycling. Elsa A. Olivetti1,3, Randolph Kirchain1,2 and Jeremy Gregory3; 1Materials Science and Engineering, MIT, Cambridge, Massachusetts; 2Engineering Systems Division, MIT, Cambridge, Massachusetts; 3Energy Initiative, MIT, Cambridge, Massachusetts.

Approximately 80% of all batteries manufactured in the world are so-called alkaline dry cells with a global annual production exceeding 10 billion units. Today, the vast majority of these batteries end up in landfills at end-of-life, equivalent to landfilling 60 thousand metric tons of steel and 40 thousand tons of zinc annually. An increased focus on environmental issues related to battery disposal, along with the recently implemented end-of-life battery directives in Europe and Canada, has intensified the discussions about end-of-life battery regulations globally. Careful evaluation of the economic and environmental impacts of alkaline battery recycling is critical to determining the conditions under which alkaline battery recycling should take place. The material composition of alkaline batteries adds layers of complexity to the recycling dilemma, as some of the materials found in such batteries, including potassium hydroxide and zinc, can be considered harmful under certain conditions. Recycling approaches for batteries include both pyrometallurgical and hydrometallurgical techniques and tradeoffs exist between the environmental benefit brought by the resulting material recovery and the attendant environmental burden of the collection and recycling steps of the process. In addition, the large quantity of alkaline batteries that are retired each year, the broad dispersion of those batteries, and the small size of each individual battery, makes the logistics of battery collection particularly challenging. This research investigates the role of the overall collection and recycling system in establishing the environmental performance of materials recovery for end-of-life batteries. This work compares the influence of system architecture and context on a baseline scenario involving collection and landfilling of alkaline batteries as part of a municipal solid waste stream with several collection scenarios for recycling of batteries through pyrometallurgical and hydrometallurgical material recovery. A series of network models to understand the impact of various collection schemes, material disposition models to understand the impact of material disposal and recovery, and life cycle assessment methods enable the evaluation of various end-of-life collection schemes and treatment scenarios for alkaline batteries in the United States.


9:00 AM R6.3
V2O5 Nanorods for High-performance Li Ion Intercalation. Alexey Glushenkov and Ying Chen; Department of Electronic Materials Engineering, The Australian National University, Canberra, Australian Capital Territory, Australia.

Vanadium pentoxide (V2O5) is a traditional material used for the electrodes in Li-ion batteries and electrochromic devices. However, the performance of V2O5 particles is significantly limited by a slow rate of lithium diffusion in the lattice and low electronic conductivity. 1D nanostructures of vanadium pentoxide are able to solve these conventional problems and provide good electrode performance. Here we report a solid-state, mass-quantity transformation directly from V2O5 powders to nanorods has been realized via a two-step approach. The nanorods were formed through a controlled nanoscale growth from the nanocrystalline V2O5 phase. The nanorods grow along the [010] direction and are dominated by {001} surfaces. Surface energy minimization and surface diffusion play important roles in the growth mechanism. Real large quantity production can be achieved when the growth process is conducted in a fluidized bed which can treat large quantities of the milled materials at once. The beneficial crystal orientation of V2O5 nanorods with suppressed thickness along the [001] direction provides an improved cycling stability for lithium intercalation.


9:15 AM R6.4
Nanostructured Anodes for Li-Ion Batteries Ming Au, Savannah River National Laboratory, Aiken, South Carolina.

Currently, carbon base anodes are being used for Li-ion rechargeable batteries through Li ion intercalation process. The theoretic capacity is limited at 372 mAh/g. The volume expansion and breakdown of solid electrochemical interface of carbon anodes during overcharging is one of the reasons of thermal runaway and fire ignition. Searching for new anode materials that possesses higher energy storage capacity and inherent fire safety is not only scientist’s passion, but the mandate of industries and customers, particularly for plug-in hybrid vehicles and portable power sources. It is found that metal oxides and metals can host Li ions through conversion process that changes lattice structure of metal oxides or forms alloy of metals. The theoretic capacity of metal oxides and metals is in the range of 500 ~ 3000 mAh/g. The volume of some metal oxides will shrink down during conversion with less mechanical stress. The metal oxides do not react with polymer electrolyte and cause fire. The aligned nanostructure, such as nanorods, creates large inter-rods space that is capable to store the charges and accommodates the volume expansion caused by conversion. It is expected the aligned nanorods of metal oxides will offer high energy and power density and inherent safety. Growing nanostructured anode materials on electrode directly will eliminate paste blending and coating processes. In this presentation, we will report our results of investigation on metal oxide nanostructured anode materials and their performance in electrochemical cells.


9:30 AM R6.5
Coating of pre-formed Si Nanoparticles with Hydrothermal Carbon as Novel Anode Material for Lithium-Ion Batteries Titirici Maria Magdalena1, Hu Yong-Sheng2, Demir-Cakan Rezan1, Mueller Jens-Oliver3, Schloegl Robert3, Maier Joachim2 and Antonietti Markus1; 1Colloid Chemistry, Max-Planck Institute for Colloids and Interfaces, Potsdam, Germany; 2Max-Planck-Institute for Solid State Research, Stuttgard, Germany; 3Fritz-Haber Institute of the Max-Planck Society, Berlin, Germany.

Rechargeable lithium-ion batteries are one of the most essentials portable electronics and electrical devices in today’s society. Due to the rapid development of such equipments there is an increasing demand for lithium-ion batteries with high energy density and long cycle life. Recent work has demonstrated that silicon/carbon composite anodes can combine the advantageous properties of carbon (high coulombic efficiency, > 90%) and silicon (high lithium storage capacity, Li4.4Si, ~ 4200 mAhg-1) to improve the overall electrochemical performance of the anode for lithium-ion batteries. Various methods have been used to synthesize nanodispersed silicon in carbon such as, chemical vapour deposition, thermal vapour deposition, pyrolitic process and PVA as a carbon source. Contrary to all these rather complicated high temperature processes we report here a new, simple and green methodology for simultaneously coating preformed silicon nanoparticles with a thin layer of SiO2 and carbon using hydrothermal carbonization of glucose under mild conditions1. This Si@SiOx/C nanocomposite with a typical core/shell structure, which was further modified by electrochemical in-situ generation of a passivated layer, shows a significantly improved lithium storage performance in terms of a highly reversible lithium storage capacity (~ 1100 mAhg-1), excellent cycling performance and high rate capability, rendering it a promising candidate as an anode material in lithium-ion batteries 2. References: 1. M. M Titirici, A Thomas, M. Antonietti, Adv. Funct. Mater, 2007, 17 (6), 1010 2. Y-S Hu, R Demir-Cakan, M. M Titirici, J O. Müller, R Schlögl, M Antonietti, J. Maier-Angew. Chem. Int. Ed., 2008, 47(9), 1645


9:45 AM R6.6
Encapsulation of Silicon Nanoparticles in Carbon Nanofibers for Li-ion Batteries Application. Chunlei Wang, Yan Yu, Abirami Dhanabalan and Kevin Bechtold; Mechanical & Materials Engineering, Florida International University, Miami, Florida.

Silicon composites have attracted much attention since they are considered to be a potential substitute for the commercial graphite anodes based on their high theoretical reversible specific capacities. However, the practical implementation of these silicon composites is hampered by the large capacity loss during the first cycle and poor cyclability. One reason for the capacity loss is attributed to the significant volume changes during cycling, which causes mechanical failure and the loss of electrical contact in the electrode. Another reason is believed to be the aggregation of silicon nanoparticles during the cycling of Si-Li alloy. Although some progress on improving the electrochemical properties of silicon composite anodes have been achieved, it is still a great challenge to fabricate silicon composites anode with high capacity, excellent cyclability and good rate capability. It is well known that nanomaterials can be used to improve the electrochemical performance of solid-state electrodes used in batteries because of the short diffusion lengths. In this work, we fabricated silicon nanoparticles encapsulated in carbon nanofibers using coaxial electrospinning. Si/carbon nanofibers were fabricated using an electrospinning technique with dual nozzles and an auxiliary cylindrical electrode. Polyacrylonitrile (PAN)/ dimethylformamide (DMF) solution was fed to the outer nozzle and the mixture of Si particles and mineral oil was fed to the inner nozzle. The feeding rates for the PAN and Si/mineral oil solutions were 20 and 5µLmin−1, respectively. As-deposited nanofibers were heated at three different temperatures, 600°C, 700°C, and 800°C. The as-deposited and heated nanofibers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray absorption spectroscopy (XAS), and Raman scattering. The heated nanofibers were mixed with 10 wt.% polyvinylidene difluoride (PVDF) dissolved in 1-methyl-2-pyrrolidinone (NMP) using an agitator for 10 min. The slurry was coated onto a copper foil current collector and dried in a hot air oven at 110°C for 2h. The active material coated copper foil was cut into circular discs of diameter 14 mm and coupled with a lithium foil counter electrode separated by polypropylene separator. The electrolyte was 1M LiPF6 with 2wt.% vinylenecarbonate (VC) dissolved in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) mixed in 1:1 (v/v) ratio. All cells were cycled in the voltage range between 0.01 and 2.0V with a battery test system (NEWARE BTS-610). The optimum electrochemical performance delivered by the samples will be discussed in detail.


10:30 AM R6.7
Tuning Porous Nanostructure Materials for Supercapacitor. Zheng Chen, Kim Cross and Yunfeng Lu; UCLA, Los Angeles, California.

Electrochemical capacitors (supercapacitors) have been attracting continuous interest because of their large capacity and high rate capability, which would satisfy the energy and power demand in many electric systems and devices, such as hybrid electric vehicles, computers and mobile electric devices. Based on charge storage mechanisms, supercapacitor electrode materials can be divided into two categories: 1) large surface area carbon for electrochemical double layer capacitance (EDLC) and 2) redox active materials (metal oxides, etc.) for pseudocapacitance. In search for electrode materials, materials with high porosity are of great interest because they exhibit desirable properties such as a large electrolyte/electrolyte interface which is vital for high storage capacity. Activated carbons which have a large surface area are commonly used as electrode materials for EDLC, the capacitance can reach up to 320 F/g at very low rate, but dramatically decreases as scan rate increases because of tortuous pore structure and high microporosity. Templated mesoporous carbons exhibit uniform pore geometry and high surface area but the transport problem has still not been addressed. Carbon nanotube (CNT) shows high rate capability but the energy density is relatively low. Metal oxides, such as RuO2, MnO2, NiO, Co3O4, and V2O5 can provide much higher capacitance than carbon materials, however they have either high cost, low operation voltage, or poor rate capability. Hierarchical pore structure will benefit the electrolyte transport and ion accumulating; nanostructure materials could provide a relatively short ion transport and thus improve the utilization of electrode active materials. Therefore, using hierarchical nanostructure architecture will not only increase the charge storage ability, but also improve the rate capability of supercapacitor electrode. In this work, we designed methods for synthesizing electrode materials with hierarchical porous structures, including carbon, metal oxides and their composites. By choosing different processes, materials that have different external structures were synthesized, such as monolith, nanoparticle, nanotube and nanowire. For example, we used surfactant assisted self-assembly to synthesize mesoporous carbon and carbon metal oxide monoliths with surface area as high to 600 m2/g. Aerosol assisted multicomponent assembly was used to synthesize porous graphite carbon nanoparticles with surface area more than 1500 m2/g. Mesoporous metal oxides with large surface area were also synthesized. In addition, CNTs were combined with metal oxides (V2O5, etc.) to fabricate porous CNT/nanowires network. All the materials were further investigated by electrochemical tests and the results indicated that the electrode materials with tuned porous nanostructure have both a larger capacitance and higher rate capability.


10:45 AM R6.8
Effects of ZnO Coating on the Electrochemical Performance & Thermal Stability of LiCoO2 as Cathode Materials for Lithium-Ion Batteries Wonyoung Chang1, Jung-Woo Choi2, Jong-Choo Im2 and Joong Kee Lee1; 1Battery Research Center, Korea Institute of Science and Technology, Seoul, Korea, South; 2Chemical & Biochemical Engineering, Dongguk University, Seoul, Korea, South.

ZnO-coated LiCoO2 particles are prepared by plasma-enhanced chemical vapor deposition (PECVD) method in the coating range from 0.08 to 0.49wt.%, and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic absorption spectroscopy (AAS). From the charge-discharge cycling tests in the 3.0-4.5V range, it was shown that both bare and ZnO-coated LiCoO2 exhibit little differences in their discharge capacities during the initial 10 cycles. With subsequent cycles, the bare LiCoO2 abruptly degraded with cycling, while the ZnO-coated LiCoO2 faded relatively slowly. In addition, different coating amounts caused different capacity retention upon cycling. To investigate the coating effect on the thermal stability of the charged cathode to 4.5V, the thermal decomposition behavior of both uncoated and coated LiCoO2 was examined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Both DSC and TGA data revealed that the ZnO-coated LiCoO2 electrodes have much smaller amount of exothermic reaction at higher onset temperature for thermal decomposition compared to uncoated electrode, and their thermal behavior with coating amount is almost consistent with the tendency of the results obtained from their cycling tests. These results indicate that the ZnO coating is effective in retarding the decomposition reaction of LiCoO2 with electrolyte as well as improving the capacity retention on cycling. The role of ZnO coating is further confirmed by impedance analysis.


11:00 AM R6.9
Porous Sn/C Composites as Anode Materials for Lithium Ion Batteries. Chunlei Wang, Xifei Li, Abirami Dhanabalan, Kevin Bechtold and Yan Yu; Mechanical & Materials Engineering, Florida International University, Miami, Florida.

In comparison with commercial graphite anode electrodes in Li-ion batteries, SnO2 can store twice the amount of lithium during cycling. During charge and discharge cycle, SnO2 reacts with lithium to form alloys with varying lithium content up to a maximum of 4.4. This process is accompanied by large volume change, which induces mechanical strain resulting in crumbling and exfoliating of the active components from the anode electrode. Furthermore, SnO2 is a wide band-gap oxide semiconductor, with reported band gap of Eg=3.6-4.0 eV. The huge volume changes and poor electrical conductivity severely prohibits SnO2 from the application in lithium ion batteries. Electrostatic Spray Deposition (ESD) provides a simple and versatile means for depositing porous metal oxide thin films. In this research, we used ESD technique to deposit porous SnO2 thin film in order to minimize the damage due to the large volume change during cycling. The precursor solution was prepared by dissolving AgNO3 and tin acetate in the solvent of Butyl carbitol and Ethanol (4:1, v/v). SnO2 / Ag composites were deposited at a temperature of 250°C. The structure and electrochemical performance of ESD-derived porous SnO2 / Ag were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge testing. It was found that porous SnO2 / Ag composites are favorable for the improvement of electrochemical performance of active materials due to improved electronic conductivity and stress resistant porous nature.


11:15 AM R6.10
Time-Resolved X-ray Diffraction Study on Structural Evolution in Olivine Materials for Lithium Rechargeable Battery. Jung-Ting Hung, Jacob Jones and Shirley Meng; University of Florida, Gainesville, Florida.

Olivine LiMPO4 where M = Fe, Mn, Co, Ni, with theoretical capacity (~170 mAh/g) have attracted numerous interests in the research field of energy storage materials. However, except for LiFePO4 (3.4V), none of these materials (LiMnPO4 - 4.1V, LiCoPO4 - 4.5V and LiNiPO4 - 5.1V) have yet demonstrated reversible capacities over ~100 mAh/g at significant charge/discharge rates, even though they are made into nano-scale. Some recent works provide new insights into the mechanisms behind high rate capability and cycle life in LiFePO4, though they are still under debate. Using time-resolved x-ray diffraction, a quantitative understanding of the time dependence of interphase boundary motion as well as the time-dependence of the changing structural occupancies can be determined. We show that the materials synthesized under different conditions show significant differences in the delithiation behavior. The observed difference correlate with the differences in microstructure, morphology and surface chemistry of samples and shed new light on the understanding of the delithiation mechanism in nano-scale LiMPO4. Such understanding is crucial in developing and optimizing the Olivine materials with higher voltages for potential application in plug-in hybrid electric vehicles.


11:30 AM R6.11
αMoO3, Potential Candidate as Active Material of Cathodes in Lithium Batteries: First Discharge and Durability During Cycling. Sebastien Berthumeyrie1,2,3, Jean-Claude Badot1,3, Stephane Bach2, Jean-Pierre Pereira-Ramos2 and Olivier Dubrunfaut3; 1CNRS-ENSCP, Paris, France; 2ICMPE, Thiais, France; 3LGEP, Gif sur yvette, France.

The molybdenum trioxide αMoO3 is one of the first material studied as a cathode for lithium batteries [1][2] and it remains a promising material as its theoretical capacity is about 1.5 Li/Mo (280mAh/g) for an average potential of about 2V [1]. This leads to specific energy of about 560 Wh/kg which is comparable to V2O5 [3]. Furthermore, αMoO3 is known to be less hazardous for health than V2O5 [4]. As αMoO3 is made of sheets [5] linked together with Van der Waals forces, it is particularly favourable to lithium ions insertion. The injection of electrons comes with the insertion of these cations in αMoO3. The knowledge of electronic and ionic transports is required to better understand electrochemical behaviours. This work deals with comprehension of both αMoO3 evolution during the first discharge of the battery and lifetime issues of these batteries. Structure of LixMoO3 compounds obtained by chemical and electrochemical lithium insertion of commercial αMoO3 powders are characterized by X-ray diffraction (XRD). Structures of these compounds are compared in order to show chemical lithium insertion can model electrochemical one. Broadband dielectric spectroscopy (40Hz-10GHz) has been used on lithiated molybdenum oxide in order to study the electronic conductivity and the motions of electrons (small-polarons). Two types of small-polaron motions have been evidenced: the first an interchain hopping (parallel to a- axis) and second one is an intrachain hopping (parallel to c- axis). These measurements have been performed in the temperature range from 190K to 300K. Investigation of activation energy of small-polarons would tend to show that the first inserted lithium ions would be localized within αMoO3 layers and not in the interlayer gap. It is a new insight to the investigation of this problem not yet solved in literature as most as we know. Commercial αMoO3 powders are cycled within a SwagLok type battery using organic electrolyte. Durability of these batteries is studied and some solutions are proposed to get better lifetime. Solubility in electrolyte and technology used to prepare αMoO3 cathodes are discussed. [1] J. O. Besenhard, R. Schöllhorn, J. Power Sources, 1, 1976/1977, 267 [2] L. Campanella, G. Pistoia, J. Electrochem. Soc., 118, 1971, 1905 [3] D. Linden, T. Reddy in: HandBook of batteries, Third Edition, ed: McGraw Hill, 2001 [4] MSDS for MoO3 and V2O5 in Alfa Aesar web site [5] J.B. Parise, E.M. McCarron III, R. Von Dreele, J.A. Goldstone, J. of Solid State Chem., 93(1), 1991, 193


11:45 AM R6.12
Abstract Withdrawn


SESSION R7: Novel Materials
Chairs: John Benner and Reuben Collins
Thursday Afternoon, April 16, 2009
Room 2018 (Moscone West)

1:30 PM *R7.1
Case Study: Titanium Dioxide and the Material Need for Renewable Energy Technologies. Samuel S. Mao, University of California at Berkeley, Lawrence Berkeley National Laboratory, Berkeley, California.

Titanium dioxide is perhaps the most versatile material that has found applications in a number of energy efficiency and renewable energy technologies. Examples include solar cells that convert solar energy to electricity, solar water splitting that produces hydrogen fuel, organic light-emitting diodes, solid-state hydrogen storage, and self-cleaning windows. Nevertheless, the nature of less-than-perfect properties of titanium dioxide prompts the need of modifying the material or finding alternative, application-specific new materials. It this talk, selected energy technology applications of titanium dioxide will be introduced, followed by a discussion of the limit of titanium dioxide and the challenges of finding alternative materials for the rapidly evolving energy efficiency and renewable energy technologies.


2:15 PM *R7.2
Modification of Thermal Sprayed Ni-WC Deposit Microstructure by Laser Glazing for Improved Corrosion and Mechanical Properties of the Coatings. Smita Kumari, R&D, EWAC Alloys Ltd., Mumbai, Maharashtra, India.

Ni-based, thermally sprayed coatings have many commercial applications for wear and corrosion resistance at low and moderate temperatures. The performance of Ni-based coatings can be improved further by adding hard precipitates such as carbides of refractory metals and cemented carbides. High Velocity Oxyfuel (HVOF) and post heat treatment by laser glazing process are combined to improve properties of hard particles imbedded Ni-based coatings. Results shows: (1) formation of new phases of borides and carbides, (2) a decrease of the pore network connectivity, voids and partially fused zones, (3) the growth of fine dendritic structures due to rapid resolidification, which could be interesting with regard to the improvement of the corrosion and mechanical properties of the coating. The rectification of these defects of thermal sprayed coatings by laser glazing process enhanced the performance of the coatings with a notable improvement in the corrosion resistance and mechanical properties of the coatings.


3:30 PM R7.3
New Materials for Unique Semiconductor and Solar Equipment Components John Foggiato and Ron Campbell; Greene Tweed, Santa Clara, California.

New materials and processes for fabricating semiconductor and solar devices require development of new materials for the components of the fabrication equipment. Higher attainable vacuums and operating at higher temperatures, the elastomeric seals have had to become more temperature resistance including higher resistance to corrosive plasmas. With the increasing need for cleanliness at the gaseous level, seal outgassing and permeability have decreased to meet these requirements. Further improvements have occurred by application of new materials to the metal components within the equipment. Coatings of metal oxides applied by thermal plasmas and high density electroplating enhance chemical resistance of the process chamber surfaces. For better thermal uniformity and gas dynamics' control within the process chambers, materials with high thermal conductivity and chemical resistance have been developed. This paper will present the progression of seal development starting with basic polymers, additives and processing technology. Seals utilizing metal oxide fillers are reviewed for their thermal and chemical resistance, although application limited due to particle generation. New development of organic based fillers has required unique processing technology to attain high temperature resilience and resistance to fluorine based plasmas; however do not shed particles as they are consumed during processing. Additional improvements are attained with seals directly bonded to metal, metal oxide or carbide parts, thus enhancing productivity. Higher temperature environments require materials with thermal characteristics along with corrosion resistance. New materials of composites are being formulated to address replacing ceramics used in such applications. Descriptions of such materials, their properties and typical applications are reviewed. Note will be made of the weight savings using such materials, especially for the large parts required for solar manufacturing. Glass plates with areas larger than 5 m2 are handled by robotic systems comprised of composite materials. Metal oxide ceramics are used for many components within solar manufacturing equipment; however development of carbides with thermal conductivity, has led to new capabilities by providing better resilience to corrosive processing environments. With in-situ cleaning of processing equipment, highly corrosive NF3 gas is used, in gaseous form gas and delivered as fluorine radicals. Radical lifetime, hence density, is very dependent on the transfer tubing materials and surface characteristics. The use of sapphire has greatly increased the gas reaction efficiency lowering consumption. Data showing its benefit will be shown, along with further improvements by surface preparation of the sapphire. In closing, the importance of component materials in improving semiconductor and solar devices will be reviewed, giving additional examples with data, along with future expected improvements.


3:45 PM R7.4
Synthesis of Ethanol and Higher Alcohols from CO Hydrogenation Using Electrodeposited Co-Cu-ZnO Nanowires as Catalysts. Mayank Gupta and James J Spivey; Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana.

Alcohols such as ethanol and higher alcohols can be used as cleaner fuel or fuel additives. One of the ways to produce these alcohols is via CO hydrogenation: an environmentally friendly and cost effective alternative. However, because of low selectivity and low yield of this reaction, there has been a recent research drive toward novel preparation methods of catalysts that can control the metal/ oxide environment more accurately as opposed to conventional methods such as wet impregnation and co-precipitation. In this pursuit, novel catalysts i.e. electrodeposited nanowires of Co-Cu-ZnO are fabricated. These nanowires are electrochemically deposited from a single aqueous electrolyte containing nitrates of cobalt, copper, and zinc. The nanowires are grown on a polycarbonate membrane by applying various current pulses. Their compositions and metal environments are controlled by carefully choosing different pulse schemes and electrolytes. A fixed bed reactor is used for CO hydrogenation reaction. Low pressure (5-10 bar) and gas hourly space velocity of 10,000 scc/ hr-gcat are found to be the most suitable reaction conditions for the formation of alcohols. Temperature programmed reduction (TPR) studies are performed to assess the interaction between copper and cobalt oxides. It is found that the reduction temperature of copper and cobalt oxides was much less than the reduction of their pure oxides thus suggesting a strong interaction between them. However, the reduction temperature of mixed oxides is different from the oxides that were prepared from conventional methods, implying different environments. It is observed that the uniform composition along the length of the nanowires is essential for obtaining higher selectivity toward alcohols. It is also found that cobalt assists in improving selectivity toward ethanol and higher alcohols. Methane and CO2 are the two most undesirable products of this reaction and their formation is minimized by appropriate selection of operating conditions during CO hydrogenation and electrodeposition.


4:00 PM R7.5
The Specific Surface Area of Copper Foam with Different Porosities Zhao Peng and Pu Yuping; Powder Metallurgy Department, Central Iron and Steel Research Institute, China, Beijing, Beijing, China.

The porous foam metal is applied in many fields especially for its high specific surface area. Different porosities of copper foam was prepared by electro-deposition method in this paper. The porosity was controlled through the electro-deposition process. The specific surface area of materials was tested by BET method, and was also calculated based on the tested characters of fluid flow within the material. The specific surface area result detected by the two methods was compared and the relation between the specific surface area and the porosity was discussed.


4:15 PM R7.6
Nitrogen Doped Carbonaceous Materials via Hydrothermal Carbonization. Titirici Maria Magdalena, Li Zhao and Markus Antonietti; Colloid Chemistry, Max-Planck Institute for Colloids and Interfaces, Potsdam, Germany.

The properties of carbon materials are dependent, to a large extent on the raw material, surface structure and porosity. However, the greatest effect on physicochemical properties of activated carbons is exerted by heteroatoms that are built into their structure (oxygen, nitrogen, boron, halogens, etc). Recently, nitrogen-containing carbons are the subject of particular interest to researchers due to their remarkable performance in applications such as CO2 sequestration, removals of contaminants from gas and liquid phases, environmental protection industry, catalysts and catalysts supports, or in electrochemistry as supercapacitors, cells and batteries to improve their capacity parameters. The methods for the production of such materials relay normally on very harsh and multistep processes, which involve high temperature production of carbon materials followed by introduction of nitrogen to the structure using ammonia, amines or urea. Here we present a green and sustainable alternative to produce nitrogen rich carbons which is based on the hydrothermal carbonization of nitrogen containing carbohydrates such as chitosane or glucosamine. This takes place by simply placing the carbohydrate precursor in an autoclave, followed by hydrothermal treatment over night at 180-200°C. The resulting material is a carbon like material containing up to 9% nitrogen. The level of structural order can be improved by further carbonization at higher temperatures (up to 750°C), while the nitrogen content is maintained within the samples. The materials can also be nanostructured by performing the hydrothermal reaction in the presence of either hard or soft templates. A detailed characterization of these types of materials after hydrothermal carbonization and different further heat treatments using techniques such as 13C and 15 N-Solid State NMR, XPS, FT-IR, XRD, SEM, TEM; TGA is presented. The materials were successfully applied as adsorbents for CO2 capture. Given the simplicity of this method and the low cost of the starting precursors we believe that this method represents a sustainable alternative for the production of nitrogen containing materials.




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