Tribological properties of graphene-modified with ionic liquids and carbon quantum dots/ bismaleimide composites

In order to improve the tribological properties of graphene reinforced polymer composites, ionic liquids (IL) and carbon quantum dots (CQDs) were deposited on the reduced graphene oxide (rGO) nanosheets surface to ameliorate the compatibility between graphene and bismaleimide (BMI) matrix, as well as the stability of their self-lubricating transfer films. Their tribological properties were evaluated, and the wear mechanism was studied by means of surface/interface analysis, respectively. It could be found that CQDs/IL/rGO could improve the stability of the friction coefficient and decrease the volume wear rate of their BMI composites. When the filler amount was only 0.6 wt%, the friction coefficient and volume wear rate of CQDs/IL/rGO/BMI composites decreased by 41.2% and 94.7% compared with the neat BMI, respectively. Also, the CQDs/IL/rGO/BMI composites exhibited the lowest friction coefficient fluctuations and volume wear rate than those of other composites. Because of the synergistic effects of the CQDs, IL and rGO, uniform, continuous and steady self-lubricating transfer film could be formed during the friction process, thus significantly improving the anti-friction and wear-resistance properties of CQDs/IL/rGO/BMI composites. More importantly, the unique combinations of advantages of each functional component can also be applied in many other fields, such as catalysis, chemical sensors, etc.