Development of a novel compressive h-BN based seal for planar intermediate temperature SOFC

A novel compressive boron nitride (h-BN) based seal has been developed for planar intermediate temperature solid oxide fuel cell (SOFC). It exhibited extremely low leakage rates and thermal cycling stability under simulated stack conditions. The h-BN based seal showed leakage rates of 0.01 sccm/cm under gas pressure of 6.8 kPa in the temperature range of 650-800 °C, and maintained similar leakage rates during 10 thermal cycles. The excellent sealing performance can be explained by oxidation of h-BN surface to form liquid B2O3 layers beyond the critical temperature of 700 °C. Two of compliant B2O3 glass layers were observed on the surface of the h-BN to adjoin well cell and metallic interconnect. The sandwich structure with liquid B2O3 layer on two sides of the h-BN seal could not only enhance interfacial adherence but also eliminate the gas leakage paths at SOFC operation temperature. The applicability of the h-BN based seal has also been verified by single cell test.