Enhanced microstructure as well as mechanical and oxidation resistance of C/C–SiC composites fabricated by RMI for thermal protection

In this study, two-dimensional needle-punched laminated C fibres were used as preforms, and interfacial phases were prepared via chemical vapor infiltration (CVI) using pyrolytic carbon (CVI-PyC), sucrose-derived carbon (S/C), and pitch-derived carbon (P/C). The effects of interfacial phases on fibre coatings and siliconizing properties were investigated. The results demonstrated that the CVI-PyC interfacial phase is the most continuous and dense, providing the best protection effect on the fibres and forming a uniform cylindrical structure after siliconizing. The S/C interfacial phase is the second best; however, the matrix is fragmented after siliconizing. The P/C interfacial phase is the worst, leading to a lamellar surface structure and microcracks after siliconizing. Using CVI-PyC and S/C alternately as matrix carbon sources, C/C–SiC composites were synthesized via reactive melt infiltration, which comprised carbon fibres, SiC, and residual Si. According to mechanical property test results, the bending and tensile strengths of the prepared C/C–SiC composites were 345.4 and 156 MPa, respectively, which are considerably higher than those of single sucrose-derived carbon (134 and 75 MPa, respectively) and CVI-PyC matrix carbon (261.9 and 108 MPa, respectively). Oxidation-resistant coatings were prepared on the surface of the materials through chemical vapor deposition. High-temperature examination demonstrated that the coating effectively inhibited fibre oxidation, and the tensile strength retention rate reached 41% at 1500 °C in an oxygen environment, whereas the strength of the uncoated samples decreased to <10 MPa. This study provides an important reference for optimizing the interface design and high-temperature oxidation resistance of C/C–SiC composites.