Tribological and rheological properties of the lubricant containing hybrid graphene nanosheets (GNs)/titanium dioxide (TiO 2 ) nanoparticles as an additive on calcium grease

The tribological and rheological properties of hybridized nanocomposite of graphene nanosheets (GNs)/titanium dioxide (TiO2) nanoparticles (NPs) as grease additives were investigated under different concentrations (0.5, 1, 2, and 3 wt.%), different loads, and different temperature. Friction reduction and anti-wear of grease having hybridized nanocomposite were measured by using a pin-on-disk tester. The rheological properties and the thermal conductivity of the modified grease were evaluated using a Brookfield rheometer and KD2 thermal analyzer. The morphology and composition of nano additives and nano grease were analyzed by HRTEM and XRD. The results show that the hybridized nano grease has better friction-reduction and anti-wear which are enhanced by about 46.7 and 43.9%, respectively, if compared to the base grease. The rheological behavior of the hybrid nano grease is generally enhanced with an increase in the concentration. On the other hand, thermal conductivity is directly proportional to an increase in the concentration of hybrid nanoparticles.