Influence of h-BN as additive on microstructure and oxidation mechanism of C/C-SiC composite

Due to the favorable self-healing performance, hexagonal boron nitride (h-BN) as additive in the matrix can significantly influence the oxidation behavior and the kinetic characteristics of C/C-SiC composites. In this work, C/C-SiC composites modified by h-BN (C/C-BN-SiC) were prepared by low-temperature compression molding (LTCM), pyrolysis and liquid silicon infiltration (LSI). Microstructure, oxidation behavior and kinetic characteristics of the C/C-BN-SiC composites were investigated compared with the C/C-SiC composite. Because h-BN is non-wetted by liquid silicon, the h-BN flakes in the matrix can obstruct and prolong the flow path of silicon, and protect the carbon fibers from corrosion to a certain extent. The oxidation kinetics of composites occur in low and high temperature domains, with different oxidation-controlling mechanisms, and the addition of h-BN can hinder the inward diffusion and lead to the decline of carbon recession and apparent activation energy.