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Type of Document Thesis Author Bettge, Martin Author's Email Address m.bettge@gmx.de URN etd-07082004-163809 Title Processing of Porous Electrodes for Solid Oxide Fuel Cells Using Tape Casting and Unidirectional Freeze-Drying Degree Master of Science Department Mechanical Engineering, Department of Advisory Committee
Advisor Name Title Peter J. Gielisse Committee Chair Peter N. Kalu Committee Co-Chair Juan C. Ordonez Committee Member Keywords
- Ceramic Processing
- Porous Media
- Mass Transport
- Aligned Pores
- Porosity Measurement
- Particle Sedimentation
- Particle Settling
- Ceramic Membranes
- Metallic Membranes
- Particle Dispersion
- Binder
- Metallic Filter
- Ceramic Filters
- Particle Size Distribution
- Powder Processing
- Metal Processing
- Porous Metals
- Porous Copper
- Porous Structures
Date of Defense 2004-07-01 Availability unrestricted Abstract The objective in conducting this thesis was the improvement of porous Solid Oxide Fuel Cells (SOFCs) structures. It is known that changes in porosity and pore geometry affect the rate of mass transport of the reactant gases through porous ceramic electrodes. This in turn influences the overall energy conversion efficiency of the fuel cell. Two ceramic processing methods, tape casting and directional freeze-drying - both capable of forming dense and porous ceramic structures - were compared in this effort. Directional freeze-drying was found to be the most promising technique. It achieved extremely high porosities (up to 90 %), aligned pores and graded porosity at levels of lower sintering shrinkage than that for tape casting. By starting out with YSZ particles, and subsequently using fine copper particles, it was shown that this method is apparently readily applicable to various materials without major modifications. Graded functional cermet layers, which are particularly important in porous SOFC electrodes, could also be incorporated into the porous body with the freeze-drying approach. Pore forming mechanisms, porosities, pore sizes and geometry were investigated using scanning electron microscopy. It was found that the mechanism which drives pore formation in directional freeze-drying is based on convective motion of the water-based polyvinyl alcohol solution.Files
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