Properties of super heat-resistant silicon carbide fibres with in situ BN coating

An in situ BN coating was prepared on the surface of a nearly stoichiometric continuous SiC fibre with trademark Cansas-3301 (C3). The coated fibre was then subjected to continuous pyrolysis at 1800 °C, obtaining a fibre named Cansas-BN-1800 (C18). After annealing in Ar at 1500 °C for 1 h, the strength retention ratio of C3 was 49%, and that of C18 was almost unchanged. The strength decrease of the C3 fibre was mainly caused by the formation of surface defects resulting from fibre decomposition and active oxidation. However, the in situ BN coating on C18 protected the fibre from forming surface defects, resulting in high strength. Due to slight growth of the grain and purification of the grain boundary during fast heating at 1800 °C, C18 showed excellent creep resistance in the range of 1200–1500 °C.