Excellent interfacial structural integrity of pre-oxidized carbon fiber-reinforced carbon-carbon composites

Carbon-carbon composites are widely used in thermal management, photocatalysis, aerospace, high-speed railway, and nuclear energy applications, owing to their low density, high temperature stability, corrosion resistance, and excellent self-lubrication performance. Improving the weak combination interface of carbon-carbon composites has always been challenging. Prior to the present study, there was no effective method for stimulating the interaction between the reinforcing phase and the carbon matrix. In this study, pre-oxidized carbon fibers with abundant active functional groups were introduced into ultrafine carbon powder, for significantly improving interfacial structural integrity in carbon-carbon composites. The effects of pre-oxidized carbon fiber on the composites were systematically studied using metallographic microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy methods. The results show that chemical bonds are formed between pre-oxidized carbon fibers and the carbon matrix, increasing the interfacial bonding strength. The pre-oxidized carbon fibers expanded adaptively after sintering, with the diameter increasing by 19.47%. The fiber expansion process inhibited cracks, decreasing the composites' porosity by 21.6%. Compared with carbon fibers, the pre-oxidized carbon fibers improved the flexural strength, impact resistance, electrical conductivity, and thermal conductivity by 31.8%, 53.3%, 18.58%, and 14.06%, respectively.