Investigation of SOFC-Gaskets Containing Compressive Mica Layers Under Dual Atmosphere Conditions

Mica gaskets and also composite gaskets containing compressive mica interlayers are under consideration as sealing material in solid oxide fuel cells (SOFC). The results of leak tests on commercially available mica papers under stationary and thermal cycling conditions are presented. The elastic recovery and spring constant at 1073 K was also determined. To study potential interactions between the interconnect steel Crofer22APU and the mineral phases vermiculite (exfoliated) (K,Mg,Fe)3(Si,Al)4O10(OH)2) and talc (Mg3Si4O10(OH)2), corrosion experiments were conducted in simulated SOFC conditions. In these experiments, the opposite walls of the gaskets were simultaneously exposed to air and wet H2. A substantial increase in the thickness of the oxide layers formed by the interconnect steel is observed in contact with mica. The Cr2O3/(Cr,Mn)3O4 duplex layer normally formed on the Crofer is replaced by a thicker (factor of 5-10) layer of a complex microstructure that is assumed to contain Cr2O3, (Cr,Mn,Mg,Fe)3O4 and Fe2O3 phases. The modified microstructure is found in the entire air manifold, with an increased thickness up to a distance of 300 μm from the mica.