No abstract

Developing polymer self‐lubricating composites is of great significance for reducing mechanical friction and wear. In this study, a hybrid of graphitic carbon nitride (g‐C3N4) nanosheets anchored carbon fiber (CF) was constructed through one‐step calcination method to enhance the tribological performance of polyimide (PI). The presence of g‐C3N4 improved the interfacial interaction of CF/PI composite by endowing CF surface with active sites and rough microstructure. Tribological test results demonstrated that CF/g‐C3N4/PI composite had outstanding antifriction and wear resistance, with friction coefficient and wear rate of 0.209 and 2.23 × 10−7 mm3/Nm, which were reduced by 21% and 73.52% compared to pure PI, respectively. This was mainly attributed to the enhanced interfacial interaction, which was conducive to the stress transferring from PI to CF/g‐C3N4 in sliding process. At the same time, the g‐C3N4 nanosheets could give the composite excellent self‐lubrication property by promoting the formation of transfer film. More importantly, the as‐proposed CF/g‐C3N4/PI composite still maintained good self‐lubricating performance in different sliding environment, with a friction coefficient of 0.132 in water environment and 0.049 in oil environment, suggesting it had a broad prospect in polymer self‐lubricating composite. In addition, the corresponding mechanism was discussed based on the analysis of worn surface of the composite and counterpart.

Polymer self‐lubricating composite coatings have been widely used on the surface of machinery to extend the life of the moving systems/parts by controlling friction and wear. In this work, epoxy nanocomposite coating with the thickness of about 60 μm was fabricated with addition of hexagonal boron nitride nanosheets (BNNSs)/CeO2 nanohybrid for enhancement in antifriction and wear resistance. The active BNNSs were first obtained by exfoliating h‐BN with alkaline solution, and then the rare earth oxide of CeO2 nanoparticles were immobilized on the surface of BNNSs through hydrothermal method. The microstructure morphology and chemical composition of as‐proposed BNNSs/CeO2 were characterized by field emission scanning electron microscopy, HRTEM, Fourier transform infrared spectroscopy, RS, X‐ray diffraction, and X‐ray photoelectron spectroscopy. And the tribological behaviors of epoxy nanocomposite coatings containing BNNSs, CeO2, and BNNSs/CeO2 were investigated comparatively using ball‐on disc friction tester (MPX‐3). And the 440C stainless‐steel ball with diameter of 8 mm was used as the counterface material. Tribological tests showed that epoxy‐BNNSs/CeO2 had the best friction and wear reduction properties, and the lowest coefficient of friction and wear rate of epoxy‐based composite coating were achieved when the content of BNNSs/CeO2 was 0.5 wt%, with 84.9% and 96.3% reduction, respectively. Moreover, the effect of sliding conditions on the tribological performance of epoxy‐BNNSs/CeO2 was investigated. The corresponding enhancing mechanisms of BNNSs/CeO2 were discussed as well.

Improving the tribological performance of carbon fabric (CF)/polymer composites is vitally significant for developing high-performance lubricating materials. We propose the combination of interfacial modification and use of a lubricant additive to enhance the antifriction and anti-wear properties of CF/phenolic (PF) composites. And the tribological properties of CF/PF composites were characterized using ball-on-disc friction and wear tester. First, ZnO nanorods were densely and uniformly grown on the carbon fiber surface using POSS as a "bridge molecule" to make fiber with a rough micro-nano microstructure and active functional groups; this was conducive to enhancing the interlaminar shear strength (ILSS) and wear resistance of CF/PF. Then, graphite (Gr) was further introduced as a lubrication additive into the modified CF-POSS-ZnO/PF to increase the friction-reducing capacity. The corresponding modified composite with 5 wt% Gr demonstrated outstanding tribological performance. The coefficient of friction and wear rate decreased by 55.37% and 93.36%, respectively, compared to those of CF/PF. Moreover, it still retained outstanding friction and wear properties in the sliding process with high loads and speeds. The synergistic mechanism of interfacial modification and lubricant additive on the tribological performance of CF/PF are discussed systematically on the basis of the analysis of the ILSS, fracture surface microstructures, and worn surfaces of the composites. This work might shed new light on the design and development of high antifriction and anti-wear CF/polymer composites.