MODIFICATION OF C/SIC COMPOSITES USING PARTIAL BORON CARBIDE SELF-SEALING MATRIX BY ICVI

摘要

C/SiC composites were modified using partial boron carbide (BC_x) as matrix by isothermal chemical vapour infiltration technique (ICVI). SEM results showed that the multilayer SiC-BC_x matrix exist among fibre bundles, nevertheless there were still SiC matrix among monofilaments. The modified composites hold better fracture roughness than the conventional C/SiC composites, although the other mechanic properties of the two kinds of composites were similar. The pull-out of multilayer matrix was the main factor of the increase of fracture toughness. Compared with the C/SiC composites coated with SiC/SiC/SiC, SiC/B-C/SiC or SiC/B/SiC coatings, the lower weight loss and higher residual strength of the modified composites were demonstrated. Furthermore, the weight gain and strength increase of the modified composites were found after oxidation at 1000 deg C and .1300 oC due to the self-sealing of the micro-cracks and pores as shown in SEM results.