Ultra-fast and stable dispersion of graphene oxide in lubricant oil toward excellent tribological property

Graphene oxide (GO) nanocomposite lubricants have been verified with excellent anti-wear and anti-friction properties. However, the rapid transfer of hydrophilic GO nanosheets into hydrophobic lubricants still faces great challenges. In this work, a series of nanocomposite lubricants were successfully fabricated by a simple phase transfer process without complex chemical modification. With the assistance of ethanol and oleylamine, the GO nanosheets initially dispersed in the water phase could be quickly transferred to the mineral oil within 20 s after hand-shaking the immiscible two-phase system. Moreover, the phase-transferred GO nanosheets were greatly stable in the mineral oil for at least seven days. The tribological properties of the GO nanocomposite lubricants had been studied by a macroscopic ball-on-disk friction test. The tribological behavior of the obtained nanocomposite lubricants showed that when 0.1 mg/mL GO was dispersed into mineral oil, the minimum average friction coefficient was 0.140, which was 72% lower than that of mineral oil. The universality of the phase transfer process was verified by the reduced GO nanosheets. This physical phase transfer method must be simple, effective, and environment-friendly to prepare nanocomposite lubricants.