Evaluation of glass composites for sealing solid oxide fuel cells

Six metallic alloys, namely, Crofer22, ZMG232, an equivalent ZMG232, stainless steels SS430, SS304 and Inconel718 were investigated. A commercial Asahi Bulk Glass is sealed on these materials and evaluated for oxidation behavior under a hot air environment for various period of time and for thermal expansion. Then the resultant oxide scale was studied; with the microstructure and chemical composition of the crystalline phases investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopic (EDS) analysis. The results show the Asahi bulk glass on ZMG232 was good for compaction and adhesion; no vacancies in the glass. ZMG232 seems to be more suitable for Asahi bulk glass than the other alloys. The glass does not fully crystallize even after long-term heat treatments at 500-600 degrees C. Sealing glass over a long period of time during operation of a solid oxide fuel cell (SOFC) would generate thermal stresses in the seal and may have adverse effects on its mechanical performance. This may lead to cracking of the seal, resulting in mixing of the fuel and the oxidant gases.