High temperature behavior of metal substrates for solid oxide fuel cells

Kurzfassung

Durability of the metal substrate for Metal Supported SOFC is a critical challenge to be addressed for long term reliability (>2500h). The metal substrate has been identified as the main failing component of the single cells due to oxidation. Thus, the chemical composition of the metal substrate has to be tailored, in order to improve the resistance towards oxidation and the cell life time. In this study, the behavior of three different metal substrates, ITM porous substrates, FeCrAl-Y and pure Ni foams were investigated at high temperature by simulating a sintering step in air the substrate has to withstand when conventional ceramic coating process are considered for the cathode layering. The three samples were sintered in air at a temperature between 1000 °C and 1250 °C, the final electronic conductivity being the main criteria to estimate the degradation due to oxydation. The Nickel Foam was fully oxidized in all tested conditions therefore no significant electronic conductivity was measured. The upper temperature limit was found around 1000 °C and 1100 °C respectively for ITM substrates and for FeCrAl-Y foam. For ITM substrate, the microstructure (porosity) was not altered up to 1100 °C while the FeCrAl-Y foam did not show any significant degradation up to 1250 °C. An innovative composite architecture was investigated to improve the electronic conductivity by impregnating the porous substrates with an electron conducting material reducible in hydrogen. The best results were obtained for FeCrAl-Y foams which were able to withstand oxidation in air up to 1150 °C with better electronic conductivities than the reference sample. This makes FeCrAl-Y a promising candidate as metal substrate for SOFC.