Tribological properties of dispersions based on reduced graphene oxide sheets and trimethylolpropane trioleate or PAO 40 oils

The main goal of this work is to study the tribological properties of nanolubricants formed by trimethylolpropane trioleate (TMPTO) or a polyalphaolefin (PAO 40) base oils with reduced graphene oxide sheets (rGO). This reduction was carried out in order to have a good stability of the nanoadditives in the fluids. For this aim, rGO nanopowders were prepared by thermal reduction of graphene oxide (GO) powders using KOH/ethanol as reducing agent. Tribological behavior of nanolubricants based on TMPTO and on PAO 40 oils with 0.05, 0.10, 0.25 and 0.50 wt% of rGO was evaluated. The tribological tests were carried out with a tribometer operating in ball on disk configuration and rotational mode under a working load of 20 N at room temperature. In order to analyze the wear track through the width, depth and cross-section area of the scar, a 3D optical profilometer was used. The best antifriction performance was found for 0.25 wt% rGO nanodispersions, with a 24% and a 20% enhancement for the PAO 40 and the TMPTO base oils, respectively. Moreover, for this last nanodispersion, a reduction of 24% in the wear track width was obtained.This work was supported by both the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF) programme through ENE2014-55489-C2-1-R and ENE2017-86425-C2-2-R projects. Moreover, this work was funded by the Xunta de Galicia (GRC ED431C 2016/001). The three last funders also financed the acquisition of the 3D Optical Profile Sensofar S Neox (UNST15-DE-3156). JMLR acknowledges Xunta de Galicia for a Principia contract. FG is grateful for financial support from the Xunta de Galicia (Centro Singular de Investigación de Galicia accreditation 2016–2019, ED431G/09) and the European Union (ERDF). Authors would like to thank the use of RIAIDT-USC analytical facilities.S