Construction and toughening mechanism of B4C@TiB2 core–shell structural units inside the SiC ceramic

Core–shell structural B 4 C@TiB 2 composite powders were synthesized via the molten salt method using micron-sized B 4 C and TiH 2 powders as raw materials. Furthermore, a SiC composite ceramic with B 4 C@TiB 2 core–shell structural units as the toughening phase was prepared by spark plasma sintering using SiC powder and the obtained B 4 C@TiB 2 composite powder as starting powders. The effects of calcination temperature and raw material ratio on the phase compositions and microstructure of the B 4 C@TiB 2 composite powders were studied, and the synthesis mechanism of the B 4 C@TiB 2 composite powder was explored. The formation mechanism of B 4 C@TiB 2 core–shell toughening units inside the SiC matrix was investigated, and the toughening mechanism of the SiC–B 4 C@TiB 2 composite ceramic was discussed. Results show that the B 4 C@TiB 2 core–shell units in the SiC matrix can induce a complex crack propagation mode and consume abundant crack propagation energy. Therefore, a high fracture toughness of 6.47 ± 0.32 MPa m 1/2 is realized for the SiC–B 4 C@TiB 2 composite ceramics.