Mechanical Properties of SiC-C/SiBCN Composites Under Thermal Cycling

SiC coated C/SiC and C/SiBCN composites were prepared by chemical vapor deposition (CVD) combined with polymer infiltration and pyrolysis (PIP) techniques. The effects of thermal cycling on bending properties of the composites were studied. The results show that compared with SiC-C/SiC, the average bending strength of SiC-C/SiBCN is measured as around 605 MPa at room temperature, which increases by 126.6%. After the oxidation at 1000℃ and 1200℃ for 3 cycles, the residual bending strength of SiC-C/SiBCN is separately measured as 417 and 342 MPa. The corresponding strength retention rates at 1000℃ and 1200℃ are 68.9% and 56.5%, respectively. Compared with to the SiC ceramic matrix by PIP, the porosity of SiBCN ceramic matrix is lower. Meanwhile, SiO2 and B2O3 are formed during the oxidation of SiBCN, which could decrease the permeation ration of the oxygen. Thus, the oxidation resistance and strength retention rate of SiC-C/SiBCN are significantly better than those of SiC-C/SiC composite. © 2021, Science Press. All right reserved.