Processing and oxidation behaviour of C/SiC-SiB₄ composite

SiB₄ powder was infiltrated into porous C/SiC, then a C/SiC-SiB₄ composite was densified by using polymer infiltration and pyrolysis (PIP) combined with chemical vapor infiltration (CVI) process. Phase composition and microstructure of the composite were characterized by XRD, EDS and SEM. Oxidation behavior of the composite was investigated in air at temperatures ranging from 500 to 1000°C, and compared with that of densified C/SiC. The results showed that the powder was infiltrated mainly into inter-bundle pores of the as-fabricated composite. It was combined with the subsequent infiltrated SiC very well. The SiB₄ powder can hinder the inwards diffusion of oxygen in air, and protect the carbon fibres and interphase from oxidation. At the temperature of 600-900°C after oxidation for 10h, the weight loss rate of the C/SiC-SiB₄ composites were less than that of densified C/SiC. The flexural strengths of both C/SiC-SiB₄ composites did not decrease obviously, which was higher than that of densified C/SiC.