Development of the graphite crystal contributing to the thermal performance of high-thermal-conductive C/C composites

The development of graphite crystals determines the thermal conductivity of carbon/carbon (C/C) composites. Nevertheless, its connection with dynamic thermal response behavior is not completely clear, especially for the high-thermal-conductive C/C (HTC-C/C) composites. This study investigates the influence of the different graphite crystal developments on the thermal response behavior of HTC-C/C composites by controlled graphitization. The results show that when the graphitization degree increases from 77.9% to 87.7%, the thermal conductivity of HTC-C/C composites in the X/Y direction increases from 311.84 W·m−1·K−1 to 453.05 W·m−1·K−1, and that in the Z direction increases from 23.13 W·m−1·K−1 to 66.17 W·m−1·K−1. The temperature distributions on the X–Y and Y-Z surfaces exhibit distinct "lattice-like" and "stripe-like" features, aligning with the arrangement of mesophase-pitch-based carbon fibers. By increasing the graphitization degree and reducing porosity, the thermal conduction of HTC-C/C composites can be significantly enhanced. The in-plane thermal conductivity is primarily governed by the graphitization degree, while the out-of-plane thermal conductivity is mainly dominated by the porosity in HTC-C/C composites.