A great leap in ablative protection of SiC-coated sharp leading edge: Advanced 2.5D C/C composites with high thermal conductivity

The leading edge of spacecraft is facing greater thermal challenges. Herein, the high thermal conductivity 2.5D-C/C composites are prepared by isothermal chemical vapor infiltration. And SiC coatings are applied to the surface using chemical vapor deposition. The thermophysical properties and ablative resistance were explored. Results show that high-temperature treatment achieves high-quality graphite microcrystal structure of mesophase pitch-based carbon fibers, which constructs long-range heat transfer channel for composites, after 3000℃ treatment, composites' thermal conductivity in X(Y) direction can reach 311 W/m·K at 25℃, which is 94.4 % higher than that of polyacrylonitrile-based carbon fiber reinforced 2.5D-C/C composites. This good thermal conductivity reduces the surface temperature of the SiC coating by 115℃ during the ablation, weakens the tendency for active oxidation of SiC by 68.0 %, increases the erosion resistance of the oxide film. The mass and linear ablation rates were only 0.12 mg/s and −0.35 μm/s, a reduction of 120.3 % and 92.2 %, respectively.