Kilogram-Scale Synthesis of Carbon Dots for Superior Friction-Reducing and Antiwear Additive

Low cost, high performance and environmentally friendly lubricants are needed for modern industrial development. Here, the high-yield carbon dots (CDs) were rapidly prepared by the aldol condensation reaction. The size of the CDs was less than 10 nm, with discrete and quasi-spherical morphology. There were also a large number of oxygen-containing functional groups on the surface of the CDs. The CDs showed good dispersion in the rich source of distilled water and the degradable sunflower oil. Under the condition of water-based lubrication, the friction coefficient of 0.1 wt% CDs decreased by 75% under 3 N load, forming boundary lubrication between the ball and the disk. Under sunflower oil lubrication condition, the friction coefficient of 0.05 wt% CDs decreased by 50% when the load was 2 N, and mixed lubrication was formed between the ball and the plate. The high-efficiency lubrication of CDs is attributed to its small size and quasi-spherical structure, which makes it easy for CDs to enter the friction gap to form a friction transfer film. This work combines CDs with liquid molecules to achieve in large-scale lubrication under contact pressure and provides great potential for tribological applications