Characterization of Porous Stainless Steel 430L for Low Temperatures Solid Oxide Fuel Cell Application

摘要

High operating temperatures in SOFC (e.g. ~900-1000°C) can cause serious physical and chemical degradation problems and are responsible for high cost of SOFC materials and operation. To address these issues, researches have aimed at reducing the operating temperature of SOFC. One option is to use alternative ceramic materials, by replacing conventional Yttria Stabilized Zirconia (YSZ) with materials possessing higher ionic conductivities at lower temperatures (e.g. 600-800°C), such as Samarium Doped Ceria (SDC). Operating temperatures below 700°C allows the use of metal-supported cells. Use of porous stainless steel layer can provide increased durability, reduced cost, higher oxidation resistance, and tolerance to thermal resistance. The porous metal support must satisfy several requirements: it must be porous enough (~20-40% porosity) to provide gas diffusion pathways, able to operate at high operating temperatures without oxidation, and match the coefficient of thermal expansion (CTE) with that of ceramic materials (YSZ and SDC have CTE of 10-12 ppm K-1). The stainless steel 400 series satisfies the above requirement and in the present work, SS430L (d50 = 44 μm) was chosen as support materials. The porous metal support is fabricated using various precursor formulations; such formulations comprise metal support powder (SS430L), plasticizer (DOP), pore former (PMMA), binder (PVB) and solvent (ethanol). Beside the precursor formulation, the sintering process is also critical. The sintering temperature profile was determined through thermogravimetric analysis (TGA) of individual components. The sintered porous metal support was characterized by Archimedes porosity measurements, dilatometry and SEM imaging. Correlation between precursor formulation, sintering profile and the resulting metal support was established. These measurements can provide guidelines to fabricate compatible metal support for MSOFC.