Oxidation behaviors and mechanisms of CVD Si-B-C ceramic in wet oxygen from 700 °C to 1400 °C

Si-B-C ceramic is an effective self-healing component to improve the oxidation resistance of C/SiC composites for long-life applications in aircraft and aerospace fields. To clarify protection mechanisms, oxidation behaviors and mechanisms of CVD Si-B-C ceramic in wet oxygen from 700 °C to 1400 °C were investigated in this work. Microstructure, bonds transformation and phase evolution of Si-B-C ceramic after oxidation were analyzed. The weight loss of Si-B-C ceramic increased linearly with time between 700 °C and 1000 °C, while it changed in a non-linear way above 1200 °C. The oxidation production of Si-B-C ceramic in wet oxygen is mainly composed of Si(OH)4, SiO2, H3BO3, B2O3 and B2O. The oxidation resistance of Si-B-C in wet oxygen is better than that of single-phase B4C ceramic because borosilicate glass is rapidly formed, which can effectively resist the wet oxygen. No fiber oxidation is found up to 1400 °C.