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RESEARCH PRODUCT

Interconnecteurs métalliques de piles à combustible de type SOFC - Résistance à la corrosion et conductivité électrique à haute température

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The need of interconnect to connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. The main important criteria requires for interconnect is an excellent oxidation resistance in air and in H2/H2O. The goal of this study is to determine the influence on corrosion behaviour of a reactive element oxide coating (La2O3, Y2O3) realized by MOCVD on different metallic alloys like Crofer22APU, Haynes230 and Fe30Cr. The realisation of long ageing (7 700 and 15 400 hours) proved to be insightful. The corrosion kinetic experiments, the oxide scale characterisation and ASR measurements established that the presence of perovskite oxides (LaCrO3, YCrO3), formed during oxidation, can significantly improve the electrical conductivity of metallic interconnects. In H2/10%H2O (anode side), the beneficial effect of reactive element oxides is less important than in air. The oxide scales formed in wet hydrogen are more porous and have a smaller grain size; this fact increases the plasticity of the oxide scale and could be explained by an increase of the anionic diffusion. Finally, the study demonstrated that the realisation of a short pre-oxidation at 1,000°C on uncoated and coated alloys can improve the oxidation resistance. Two stage oxidation experiments at 800°C in 16O2/18O2 demonstrated that this improvement could be explained by a change of the corrosion mechanism; the pre-oxidation decreases the cationic diffusion.