Materials engineering for next generation solid oxide fuel cells.

摘要

Fundamental challenges remain in developing the materials sets necessary to achieve required levels of performance and durability in SOFC. In this research, the development of a thin electrolyte by using a new processing method and the investigation of degradation mechanism of the metallic interconnect/electrode interface were performed.; Electron beam physical vapor deposition (EB-PVD) of 7 mol % yttria stabilized zirconia coating was performed in order to evaluate feasibility of EB-PVD process for producing solid oxide fuel cell (SOFC) electrolyte. Relatively dense columnar grain microstrucure was obtained. However, pores and other defects were observed especially as coating thickness increases. Smooth anode substrate surface and optimizing deposition parameter are required to obtain a dense coating. Ionic conductivity of 7YSZ coating decreased with increasing coating thickness due to increase in pores and defect in the microstructure. It is critical to improve density of coating in order for EB-PVD to be considered as a process for producing SOFC electrolyte because dense coating enhances ionic conductivity and gas tightness.; In IT-SOFCs, the in-service growth of an oxide layer between the metal component and adjoining oxide materials leads to undesirable increases in area-specific resistance (ASR) across the interface. In order to develop ideal electrical contact layer, fundamental mechanism of the evolution of interface between electrical contact and metallic interconnect in SOFC cathode environment was studied. Interdiffusion between electrical contact material and growing oxide was observed and contributed to ASR increase rate. It seems that development of electrical contact material that reacts with oxide scale and forms the phase that has low resistance is a direction to pursue.; To elucidate the role of electrical fields on oxidation processes, the development of ASR at the LNF electrode contact/SOFC metallic interconnect candidate alloys was studied. Based on experimental observations and parametric analysis, mechanisms accounting for the influence of electrical potential on the oxidative degradation of metal interconnect materials were explored. The assessment indicates that the transport rate of both oxygen and impurity ions in the alloy are significantly influenced by the applied electrical field. However, further study is required to elucidate the mechanism.