Abstract
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. 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 an important 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 ceramic coating was made from low-cost commercially available powders and deposited by atmospheric plasma spray (APS) method. The coating composition and fabrication procedure were optimized for high mechanical robustness, low electric conductivity. Experimental results based on coated “button” samples have demonstrated good bond strength between the plasma-sprayed ceramic layers and interconnect substrates, excellent thermal shock resistance, good electrical insulation properties, and low permeability. Initial testing result of a composite seal formed with a glass filler has shown a low gas leak rate and good thermo-cycling resistance.
