Development of composite substrate for metal-supported SOFC

Kurzfassung

This work was accomplished at the German Aerospace Center (DLR) in Stuttgart within the framework of the European project EVOLVE and presents a new innovation concept for the SOFCs development. The substrate development was based on metal foam with high porosity, in which ceramic composite LST/CGO was impregnated. High porosity creates surface imperfections that are possible to reduce with surface treatment, substrate flattening, and imprinting layers by cold lamination. The substrate was developed for the deposition of dense electrolyte. The deposition by bi-layers system has problems with de-lamination and surface cracking. Electrolyte deposition by screen-printing on smooth surface was successful, however the electrolyte obtained was not dense, because it needs high temperature thermal treatment for acceptable densification (>1200°C). Furthermore, substrate shrinking due to TEC mismatch between substrate and electrolyte, avoid the densification. Using vacuum plasma spray, thermal treatments is not necessary for electrolyte densification, but the process needs highly robust substrate surface to withstand the particle splats impact in order to obtain a dense electrolyte. The robustness increases with greater material load on the surface and has a strong dependence on thermal treatment temperature and atmospheric conditions. However, it is possible to obtain a robust surface with a simpler process, in which 2 metal foams were pressed into each other increasing the metal content and reducing porosity.