Ablative property and mechanism of pitch-based carbon fiber modified C/C composites with high thermal conductivity

The novel C/C composites with thermal transport function were prepared using the mesophase-pitch carbon fibers (CF_MP) as the thermal diffusion channels. The introduction of CF_MP greatly improved the microstructure, thermal properties, and ablative resistance of the C/C composites. During the graphitization process, compared with PAN fibers (CF_PAN), CF_MP was more likely to be graphitized to form a highly ordered three-dimensional graphite structure. The highly organized microcrystalline structure of CF_MP resulted in a tight interface with PyC that lessened the likelihood of flaws and cracks during graphitization. CF_MP, which acted as a thermal conduction skeleton, significantly improved the thermal conductivity of C/C composites. After 3000 °C HTT, the thermal conductivity of C/C-3000-Z composites was increased to 51.70 and 225.02 W/(m K) in the XY and Z planes, respectively. During the ablation process, C/C-3000-Z specimen exhibited a lower temperature gradient and less thermal stress owing to the outstanding thermal properties and fewer defects. After 30 s ablation, the temperature difference of surface and backside was only 495.9 °C, and the mass and linear ablation rates were 0.3 μm/s and 0.9 mg/s, respectively.