Compression properties and leakage tests of mica-based seals for SOFC stacks

Sealing properties and compression properties of two mica‐based materials, Thermiculite 866 and Statotherm HT were measured. Thermiculite 866 was tested in two forms: as‐made and precompressed (consolidated). Sealing tests were carried out at 800 °C with simulated fuel cell anode gas. Seals were pressed to a constant thickness, which represents the conditions in fuel cell stacks. Both seals showed stable leak rates over test periods of roughly 400 h. Leak rates of Thermiculite 866 samples were found to be independent of the hydrogen overpressure within the measurement accuracy in the pressure range of 10–100 mbar(g). However, a Statotherm HT gasket tested with lower compression stress compared to Thermiculite 866 gaskets showed roughly linear dependency on the overpressure. Compression tests were carried out at room temperature and at 800 °C. Compression properties of both materials were found to strongly depend on temperature. Both materials experienced swelling when heated to 800 °C and were more ductile compared to room temperature.