In situ toughened two-phase B₁₂(C, Si, B)₃–SiC ceramics fabricated via liquid silicon infiltration

In situ toughened B₁₂(C, Si, B)₃–SiC ceramics were successfully fabricated via the liquid silicon infiltration process. Two types of B₁₂(C, Si, B)₃ phases, with high and low Si contents, respectively, and plate-like SiC particles were formed by the reaction between B₄C and Si. The in situ toughening mechanism involved two effects: the multiple crack deflections caused by the increased grain boundaries, and the pullout and rupture of a significant amount of plate-like SiC particles. Block ceramics with a high fracture toughness of 6.5 ± 0.5 MPa·m^1/2 were fabricated via the in situ toughening mechanism. A strong interface bond was present between the high- and low-B₄C-content layers in the laminated ceramics, which led to residual compressive stress inside the materials. As a result, the laminated structural design enhanced the fracture toughness to 7.5 ± 0.5 MPa·m^1/2.