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1231 |
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Monday, June 02, 2008, Auditorium 2 2:00 PM Solid Oxide Fuel Cell 1 Coatings for SOFC components for mobile and stationary applications, thermal and electrical insulation by thermal sprayed ceramic coatings |
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Insulation and sealing of metal supported SOFC devices by plasma sprayed ceramic layers |
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Johannes Arnold* / German Aerospace Center (DLR)
Institute of Technical Thermodynamics
, BW Asif Ansar / German Aerospace Center, Institute of Technical Thermodynamics, Germany Uwe Maier/ ElringKlinger AG, Germany Rudolf Henne/ , Germany |
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Solid oxide fuel cells (SOFCs) are one of the potential options as auxiliary power units (APU) in transportation, e.g. in vehicles or aircraft. The supply of hydrogen in a stack can be realized after reforming of kerosene or gasoline, or by direct reforming in anode, without the need of a complex gas cleaning process removing the carbon monoxide. In particular metal supported plasma sprayed SOFCs, consisting of a metal frame and substrate coated with plasma sprayed functional layers, have shown excellent tolerance during redox cycling. In order to provide sufficient power, these single cells have to be assembled as stacks. To prevent short-circuiting the frame of each cell has to be electrically insulated from the neighbouring one. For that purpose glass seals were used previously which proved to have insufficient service life and poor reliability, particularly in cyclic conditions. Another approach consists in applying an electrically insulating ceramic coating on each metal frame by thermal spraying and brazing it to other stack components. The layer has to be designed in such a way that silver based brazing material should wet and adhere well with the ceramic deposit. On the other hand the coating has to maintain its insulating properties at high temperature. As the solder, which connects the cells and seals the gas manifold concurrently, is conductive, a good adhesion between brazing material and insulation layer is mandatory but penetration of brazing into the deposit has to be avoided. In this paper a description of the design and experience with these plasma sprayed isolation layers will be given. |