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

摘要

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 degrees C to 1400 degrees 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 degrees C and 1000 degrees C, while it changed in a non-linear way above 1200 degrees 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 degrees C. (C) 2016 Elsevier Ltd. All rights reserved.