Oxidation Behavior of SiC/Si-B-C-N Ceramic Matrix Composites

Abstract

Silicon carbide fiber reinforced Si-B-C-N (SiC/Si-B-C-N) ceramic matrix composites were manufactured through polymer impregnation pyrolysis (PIP) process with SiC fiber as disperse phase and Si-B-C-N ceramic as continuous phase. Thermal stability of SiB-C-N ceramic and the high temperature oxidation behavior of SiC/Si-B-C-N ceramic matrix composites were studied. Results showed that the introduction of boron and nitrogen element restrained the growth of SiC grain and the formation of crystalline phase transformation effectively, and could help to keep the amorphous state up to 1400°C. In addition, SiC/Si-B-CN ceramic matrix composites possessed excellent high temperature oxidation resistance with bending strength retention rate of 80.57% after oxidation test at 1200°C for 100 hours due to the formation B2O3 or borosilicate glass from the oxidation of boron element. Liquid B2O3 or borosilicate glass with suitable fluidity could fill the pores and cracks in the interior which acted as a protective layer and lowered oxygen diffusivity according to the morphology and component analysis. Therefore, SiC/Si-B-C-N ceramic matrix composites possessed excellent oxidation resistance for a wide temperature range.