A new route to fabricate SiB₄ modified C/SiC composites

In order to improve the oxidation and thermal shock resistance of 2D C/SiC composites, dense SiB₄-SiC matrix was in situ formed in 2D C/SiC composites by a joint process of slurry infiltration and liquid silicon infiltration. The synthesis mechanism of SiB₄ was investigated by analyzing the reaction products of B₄C-Si system. Compared with the porous C/SiC composites, the density of C/SiC-SiB₄ composites increased from 1.63 to 2.23g/cm³ and the flexural strength increased from 135 to 330MPa. The thermal shock behaviors of C/SiC and C/SiC-SiB₄ composites protected with SiC coating were studied using the method of air quenching. C/SiC-SiB₄ composites displayed good resistance to thermal shock, and retained 95% of the original strength after being quenched in air from 1300°C to room temperature for 60 cycles, which showed less weight loss than C/SiC composite.