Synthesis of hexadecylamine modified carbon dots and their friction-reducing and anti-wear performance in polyalphaolefin

Hexadecylamine modified carbon dots (CDs-HA) were synthesized by pyrolyzing citric acid in HA. The friction-reducing and anti-wear properties of CDs-HA as lubricant additives of polyalphaolefin (PAO4) were evaluated on the universal mechanical tester under the ball-on-disk linear reciprocating model and steel/steel contact. The concentration (c) and load both displayed great influences on the tribological properties of CDs-HA. At the load of 20 N and the optimum c of 1 wt%, the friction coefficient and wear volume of PAO4 reduced by 27.1% and 45.9%, respectively. In the load range of 20–100 N, the friction-reducing performance of CDs-HA remarkably decayed with increasing load, whereas their anti-wear property attenuated tenderly. The results of wear scar analyses demonstrated that the CDs-HA as additives not only participated in the formation of boundary lubrication films on the rubbing surfaces, but also should play the rolling, polishing and mending effects, and hence exhibited the outstanding friction-reducing and anti-wear performance.