A new strategy to improve the ablation resistance of C/C-ZrC-SiC composites by using mesophase-pitch-based carbon fibers as heat transfer channels

Currently, C/C-ZrC-SiC composites prepared using the precursor impregnation pyrolysis (PIP) process still suffer from insufficient thermal conductivity of the components, leading to excessive surface heat accumulation. Herein, a 3D highly thermally conductive preform was prepared by using mesophase-pitch-based carbon fiber (CF_MP) as reinforcing fiber. Subsequently, the CF_MP/C skeleton was fabricated by chemical vapor infiltration and heat treatment at 2450 °C. Finally, the CF_MP/C skeleton was further treated using the PIP process, thereby obtaining the CF_MP/C-ZrC-SiC-2450 °C composites. Benefiting from the highly orientated graphite microcrystalline structure and large phonon mean free path of CF_MP, as well as the partial axial alignment of CF_MP in the X(Y)Z plane parallel to the ablation direction, the thermal conductivity of the CF_MP/C-ZrC-SiC-2450 °C composites in the X(Y)Z plane was higher than that in the XY plane, thereby effectively reducing the surface temperature. Afterward, the crystallinity of the graphite structure in CF_MP was again enhanced by increasing the heat treatment temperature to 3000 °C, and CF_MP/C-ZrC-SiC-3000 °C composites with excellent ablation resistance were obtained, corresponding to linear and mass ablation rates of 0.412 μm/s and 1.081 mg/s, respectively. The above results indicated that the highly crystalline CF_MP/C thermally conductive skeleton played a key role in reducing the ablation surface temperature and protecting the ZrC-SiC ceramics from oxyacetylene flame ablation, laying a solid foundation for the subsequent development of high-performance ablation-resistant C/C composites.