Synergistic graphene modification and heat-treatment regulation for low-density 3D C/C composites with enhanced mechanical, thermal, and EMI shielding performance

Carbon/carbon (C/C) composites are key materials in the defense and aerospace fields. However, achieving low density while maintaining excellent macroscopic properties remains challenging. In this study, the microstructure of C/C composites was optimized by introducing graphene (GN) and by regulating the heat treatment temperature (2400, 2700, and 3000°C) to reduce porosity, improve texture, and optimize residual thermal stress. Accordingly, GN-C/C composites with excellent compressive, thermal, and electromagnetic protection performance at low densities were successfully prepared. The results show that the density of GN-C/C composites treated at 2400°C is only 1.81 g·cm⁻³, the Z-direction compressive strength is 331.34 MPa, the thermal conductivity in the XY directions at room temperature is 71.25 W·m⁻¹·K⁻¹, and the electromagnetic shielding effectiveness is 44 dB. Compared with the C/C composites without GN modification, the Z-direction compressive strength, room-temperature XY-direction thermal conductivity, and electromagnetic shielding effectiveness increased by 6.08%, 20.58%, and 41.94%, respectively, while the micropore porosity with diameters of 4–30 μm decreased by 18.07%. This method, based on nano-reinforcement and process synergy, provides a feasible strategy for preparing high-performance C/C composites.