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Micro-Solid Oxide Fuel Cell (micro-solid + oxide_fuel_cell)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Anode-Supported Tubular Micro-Solid Oxide Fuel Cell

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2007
Partho Sarkar
A tubular anode-supported "micro-solid oxide fuel cell" (,SOFC) has been developed for producing high volumetric power density (VPD) SOFC systems featuring rapid turn on/off capability. An electrophoretic deposition (EPD)-based, facile manufacturing process is being refined to produce the anode support, anode functional and electrolyte layers of a single cell. ,SOFCs (diameter <5 mm) have two main potential advantages, a substantial increase in the electrolyte surface area per unit volume of a stack and also rapid start-up. As fuel cell power is directly proportional to the active electrolyte surface area, a ,SOFC stack can substantially increase the VPD of an SOFC device. A decrease in tube diameter allows for a reduction in wall thickness without any degradation of a cell's mechanical properties. Owing to its thin wall, a ,SOFC has an extremely high thermal shock resistance and low thermal mass. These two characteristics are fundamental in reducing start-up and turn-off time for the SOFC stack. Traditionally, SOFC has not been considered for portable applications due to its high thermal mass and low thermal shock resistance (start-up time in hours), but with ,SOFCs' potential for rapid start-up, new possibilities for portable and transportable applications open up. [source]

Time,Temperature,Transformation (TTT) Diagrams for Crystallization of Metal Oxide Thin Films

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2010
Jennifer L. M. Rupp
Abstract Time,temperature,transformation (TTT) diagrams are proposed for the crystallization of amorphous metal oxide thin films and their specific characteristics are discussed in comparison to glass-based materials, such as glass-ceramics and metallic glasses. The films crystallize from amorphous to full crystallinity in the solid state. As an example the crystallization kinetics for a single-phase metal oxide, ceria, and its gadolinia solid solutions are reported made by the precipitation thin-film method spray pyrolysis. The crystallization of an amorphous metal oxide thin film generally follows the Lijschitz,Sletow,Wagner (LSW) Ostwald ripening theory: Below the percolation threshold of 20 vol% single grains crystallize in the amorphous phase and low crystallization rates are measured. In this state no impact of solute on crystallization is measurable. Once the grains form primary clusters above the threshold the solute slows down crystallization (and grain growth) thus shifting the TTT curves of the doped ceria films to longer times and higher temperatures in comparison to undoped ceria. Current views on crystallization of metal oxide thin films, the impact of solute dragging, and primary TTT diagrams are discussed. Finally, examples on how to use these TTT diagrams for better thermokinetic engineering of metal oxide thin films for MEMS are given, for example, for micro-Solid Oxide Fuel Cells and resistive sensors. In these examples the electrical properties depend on the degree of crystallinity and, thereby, on the TTT conditions. [source]

Microstructure and Microfabrication Considerations for Self-Supported On-Chip Ultra-Thin Micro-Solid Oxide Fuel Cell Membranes

FUEL CELLS, Issue 5 2009
B.-K. Lai
Abstract La0.6Sr0.4Co0.8Fe0.2O3,,,, (LSCF) has been sputtered on bare Si and Si3N4 and yttria-stabilised zirconia (YSZ) thin films to investigate annealing temperature- and thickness-dependent microstructure and functional properties, as well as their implications for designing failure-resistant micro-solid oxide fuel cell (,SOFC) membranes. The LSCF thin films crystallise in the 400,450,°C range; however, after annealing in the 600,700,°C range, cracks are observed. The formation of cracks is also thickness-dependent. High electrical conductivity, ,520,Scm,1 at 600,°C, and low activation energy, ,0.13,eV, in the 400,600,°C range, are still maintained for LSCF films as thin as 27,nm. Based on these studies, a strong correlation between microstructure and electrical conductivity has been observed and an annealing temperature-thickness design space that is complementary to temperature-stress design space has been proposed for designing reliable membranes using sputtered LSCF thin films. Microfabrication approaches that maintain the highest possible surface and interface quality of heterostructured membranes have been carefully examined. By taking advantage of the microstructure, microfabrication and geometrical structural considerations, we were able to successfully fabricate large-area, self-supported membranes. These results are also relevant to conventional or grid-supported SOFC membranes using ultrathin nanocrystalline cathodes and ,SOFCs using cathode thin films other than LSCF. [source]

Crystallization and Grain Growth Kinetics for Precipitation-Based Ceramics: A Case Study on Amorphous Ceria Thin Films from Spray Pyrolysis

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
Jennifer L. M. Rupp
Abstract The introductory part reviews the impact of thin film fabrication, precipitation versus vacuum-based methods, on the initial defect state of the material and microstructure evolution to amorphous, biphasic amorphous-nanocrystalline, and fully nanocrystalline metal oxides. In this study, general rules for the kinetics of nucleation, crystallization, and grain growth of a pure single-phase metal oxide thin film made by a precipitation-based technique from a precursor with one single organic solvent are discussed. For this a complete case study on the isothermal and non-isothermal microstructure evolution of dense amorphous ceria thin films fabricated by spray pyrolysis is conducted. A general model is established and comparison of these thin film microstructure evolution to kinetics of classical glass-ceramics or metallic glasses is presented. Knowledge on thermal microstructure evolution of originally amorphous precipitation-based metal oxide thin films allows for their introduction and distinctive microstructure engineering in devices-based on microelectromechanical (MEMS) technology such as solar cells, capacitors, sensors, micro-solid oxide fuel cells, or oxygen separation membranes on Si-chips. [source]