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Monday, May 15, 2006 - 9:40 AM
APP11.3

Application of Plasma Sprayed Coatings in a Novel Integrated Composite Seal for SOFCs

X. Huang, K. Ridgeway, S. Narasimhan, K. Reifsnider, University of Connecticut, Storrs, CT; X. Ma, Inframat Corp., Farminton, CT

Affordable and reliable solid oxide fuel cells (SOFCs) are being widely sought as the next-generation answer to the power needs of many applications throughout the world.  Maintaining stable hermetic sealing is critical for SOFC stacks to achieve high efficiency and longevity.  Existing glass and glass ceramic seals have shown limited failure resistance to thermo-cycling.  In long term, chemical interaction between sealing glass and Fe-Cr based interconnect material sometime results in a weakened interface.  Compressive seals based on mica have been shown to have excellent thermal cycle stability. However, they require expansive high-temperature load-frame to maintain a high compressive force.  The authors have introduced a novel multi-layered composite seal, consisting of thin layers of oxidation resistant alloys, plasma sprayed ceramic, and hermetic filler materials.  The seal structure will be directly fabricated onto the surfaces of mating adherends using low-cost manufacturing methods such as atmospheric plasma spray (APS).  During stack assembly, sealing can be achieved through a simple heat/pressure-assisted curing process. As part of the layered composite seal, a plasma sprayed porous alumina-YSZ (yttria-stabilized zirconia) ceramic coating on Fe-Cr based interconnect material has been developed.  The coating was made from low-cost commercially available powders and deposited by atmospheric plasma spray method.  The coating composition and fabrication procedure were optimized for high mechanical strength/toughness, low electric conductivity, and good refractory properties.  Results based on “button” composite seal samples have demonstrated good bond strength between the plasma-sprayed ceramic layers and interconnect substrates, good electrical insulation properties, satisfactory gas sealing performance, long-term chemical stability, and improved thermo-cycling resistance.  

Summary: The authors report the application of plasma sprayed coatings in an integrated composite seal structure for solid oxide fuel cells. The composite seal, consisting of layers of oxidation resistance meta, porous ceramics, and hermetic fillers, are directly fabricated on to a Fe-Cr substrates (interconnet). The sealing can be formed by a simple pressure assited curing processes. The composites seal fabrication, performance characterization methods and results are dicssed in detail.