Abstract: Traditional carbon/carbon composites, such as carbon fiber reinforced carbon matrix composites, are a promising carbon material widely applied in the aerospace field due to their unique mechanical, thermal, and electrical properties. However, it becomes almost impossible to further enhance their mechanical properties because of the weak van der Waals bonding within or between components. Here, by precisely controlling the graphitization transformation of nanodiamonds, we have successfully synthesized in-situ disordered graphitic carbon/nanodiamond composites under an industrially achievable pressure of 2 GPa and a moderate temperature of 1200-1400 °C. In the composites, nanodiamonds are dispersed in disordered graphitic carbon fragments, featured by a larger spacing compared to that of ideal graphite. Moreover, the nanodiamond and graphitic carbon components are irregularly connected at the interface through random sp² or sp³ bonding. Compared with the traditional carbon/carbon composites, the synthesized composites demonstrate exceptional properties: a hardness of up to 17.5 GPa, a compressive strength reaching up to 1.8 GPa, a flexural strength of up to 380 MPa, and an electrical conductivity of around 2290 S/m. This research makes it possible to fabricate high-performance carbon/carbon composites coupled high strength/hardness and electrical conductivity at an industrial achievable pressure.

Key words: Composite, Diamond, Disordered graphitic carbon, Mechanical properties, Electrical properties