Influence of precursor composition on oxidation behavior of SiBCN multiphase ceramic and oxidation resistance of SiC/SiBCN composites

The oxidation behavior of SiBCN multiphase ceramics and SiC/SiBCN composites with different compositions in high-temperature oxidation environments was studied by means of scanning electron microscopy, thermogravimetric analysis, elemental analysis, and mechanical performance test. Results showed that the PCS content was an important factor affecting the high-temperature oxidation resistance of SiBCN multiphase ceramics and SiC/SiBCN composites. The surface and cross-section oxygen content of the SiBCN multiphase ceramics first decreased and then increased with the growth of polycarbosilane (PCS) content. Furthermore, the composition and structural stability of SiBCN multiphase ceramics at 1200 °C were significantly better than that at 1500 °C. The decrease in mechanical properties of SiC/SiBCN composites at the oxidation temperature of 1500 °C was mainly due to the gradual volatilization of oxidation products, forming a large number of pores and cracks on the surface and inside of the substrate, destroying the stability of material components and structure, and forming channels for the penetration of oxidation media, which might become the main factor of material performance degradation.