3D C_f/SiBCN composites prepared by an improved polymer infiltration and pyrolysis

Using liquid poly(methylvinyl)borosilazanes (PMVBSZ) as precursor, carbon fiber reinforced SiBCN matrix composites (C_f/SiBCN) were fabricated by a modified polymer infiltration and pyrolysis (PIP) process. With dicumyl peroxide added as cross-linking agent, the PMVBSZ could be solidified at a low temperature of 120 ℃, leading to a high ceramic yield of ~70%. The cross-linking mechanism and ceramization processes of the precursor were investigated in detail. Moreover, a modified infiltration technology was developed, which improved the efficiency and protected the precursor against moist air during PIP. Consequently, the obtained C_f/SiBCN composites had an oxygen content of around 1.22 wt%. Benefiting from the high ceramic yield and high efficiency of the modified PIP, C_f/SiBCN composites with an open porosity of ~10% and uniform microstructure were obtained after only 7 cycles of PIP. The flexural strength and fracture toughness of the derived C_f/SiBCN composites were 371 MPa and 12.9 MPa·m^1/2, respectively. This work provides a potential route for the fabrication of high performance C_f/SiBCN composites.