Microstructural characterization and tribological behavior analysis on triethanolamine functionalized reduced graphene oxide

Abstract

Abstract A facile and modified hydrothermal method was reported for the simultaneous reduction and functionalization of graphene oxide without any reductant. The lubrication mechanisms of nanomaterials were analyzed based on tribological experiments and molecular dynamic simulation. Tribological studies indicated that triethanolamine functionalized graphene oxide exhibited excellent friction-reducing performance and the optimal concentration was 0.15 wt.%, while 0.25 wt.% of triethanolamine functionalized graphene oxide showed best wear resistance in the pin-on-disk experiment. An anti-wear and friction-reducing coefficient τ was proposed to evaluate the tribological properties of lubricants for a uniform standard. Molecular dynamics simulation results revealed the influence of different functional groups on the anti-wear and friction-reducing performance. The sliding distance between graphene oxide layers with COOH functional groups was the longest, it was conducive to reduce the friction coefficient but decrease the wear life. The order of diffusion coefficients of graphene oxide containing different functional groups was DCOOH (4.02 × 10–11 m2 s−1) > DC-OH (1.42 × 10–11 m2 s−1) > DC–O–C (5.24 × 10–12 m2 s−1). It was proposed and verified that the structure of graphene oxide could be optimized by grafting triethanolamine molecules on the C–O–C functional groups to ameliorate the tribological properties.