Improvement of sealing performance for Al2O3 fiber-reinforced compressive seals for intermediate temperature solid oxide fuel cell

Abstract

Ceramic based compressive seal is regarded as an option for sealing the planar solid oxide fuel cell (SOFC) stack. However, during the practice of SOFC stack testing, the powder-based seals are found to have weakness in keeping mechanical integrity. In consideration of enhancing mechanical properties, ceramic fibers are added to the powder-based seals and the relationship between sealing performance and the content ratio of the ceramic fiber under different inlet gas pressure is investigated. The seal containing 20 wt% ceramic fiber (F20) is found to have the best sealing performance. The leakage rate can be maintained at about 0.01 sccm/cm at 750 °C during 10 thermal cycle testing. The interface between the seal and adjacent components exhibits good contact conditions and chemical compatibility which can effectively avoid the formation of interface leakage paths. Introducing the ceramic fiber reduces the tensile strength of the seal but enhances ductility and thus improves the reliability and structural integrity of the seal. The applicability of the F20 composite seal is verified in a SOFC 1-cell stack testing.