Tribological Properties of Graphene in PAO Base Oil

To improve the dispersibility of graphene in lubricating oil, a high molecular weight succinimide (dispersant A) was used as dispersant to assist the graphene to disperse into PAO4 base oil steadily. The dispersibility was characterized by UV-Vis spectroscopy, and the tribological properties of graphene/PAO4 dispersion were investigated by UMT-3 Tribological Tester and ContourGT-K 3D Profiler. Scanning electron microscopy (SEM), energy spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to observe and evaluate the morphology and elemental composition of the wear scar surface, respectively. The results show that dispersant A can effectively improve the dispersibility of graphene in PAO4. When dispersant A is used, the relative concentration of graphene/PAO4 laid aside for one week is 0.667, which is 7.8 times that of the disperse system without dispersant A. Graphene, as a lubricating oil additive, can significantly reduce the friction and wear. When 0.8 mg/mL of graphene and 0.2% of dispersant A are added, the running-in period decreases from 670 s to 250 s, and the wear volume reduced by 55%.