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Pretreatment using O2 plasma is a commonly used method today to increase the surface activity of CFs and enable more functional groups to be grafted onto them. Although the oxidation treatment of the CF surface is considered a key procedure for further grafting with functional groups, few researchers have investigated how the oxidation treatment influences the grafting processes. In this paper, the effects of the degree of oxidation on the grafting of amino functional groups onto CFs were experimentally investigated. The experiment showed that the oxidation process developed in steps including initial oxidation, saturation oxidation, and peroxidation. The results demonstrated that the degree of oxidation was positively correlated with the grafting efficiency within a certain range. Furthermore, the groups (unsaturated C, C-OH, and O=C-OH) produced after oxidation determined the results of grafting with amino (C-N, C-NH2, and O=C-NH2) groups. When the O2 plasma treatment time was increased from 0 min to 3 min, the IFSS of CF@HA increased by 1.07 times and the flexural strength of CFRP increased by 1.26 times. This work proves that the ammonia grafting of CF can be controlled by adjusting its earlier oxidation process. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Using Fe reaction products to overcome the poor wettability between copper and carbon, C/Cu-Fe composites with excellent properties were prepared by gas pressure infiltration technique. The elemental Fe, being distributed between carbon and Cu, reacted with carbon to form Fe3C layer and effectively improved the wettability of the C/Cu system. The contact angle decreased from 124° to 21°. Compared to composites without Fe doping, the C/Cu-Fe composites exhibit significantly higher compressive and flexural strengths, as well as electrical resistivity reaching six times better than the industry standard requirement. Microstructure analysis indicates that the continuous tight Fe3C interlayer with moderate thickness at the C/Cu interface has a bridge effect on the interfacial bonding enhancement. [ABSTRACT FROM AUTHOR]

Carbon/copper composites are widely used in collector brushes, pantograph sliders, collector shoes and other fields due to their excellent mechanical friction, wear, thermal conductivity and electrical conductivity. However, the interfacial bonding force of composites is weak because of the natural non-wetting of copper and carbon graphite matrix, which restricts its comprehensive mechanical and electrical properties. In this paper, the nickel element was doped and introduced in the preparation process of the carbon graphite matrix, and the carbon/copper composites were further prepared by the pressure impregnation method. The results showed that the modified carbon matrix doped with nickel was denser, and the nickel element could evenly distribute in the carbon matrix. The porosity of the modified carbon/copper composites was significantly reduced and the interfacial bonding method was changed from the original simple mechanical interlock to solid solution bonding so that the interfacial state was obviously improved. The effect of nickel content on the mechanical and electrical properties of composites was systematically studied. It was found that when the nickel content was 3 wt%, the compressive strength and flexural strength were increased by nearly 52% and 58%, and the electrical conductivity was increased by nearly 35%. [ABSTRACT FROM AUTHOR]