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For this article, oleic acid surface-modified zeolitic imidazolate framework-8/graphene oxide (OA-ZIF-8/GO) nanocomposites were prepared by a facile in situ synthetic method. The as-prepared composite samples were analyzed and characterized by means of transmission electron microscope (TEM), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TG). The tribological behaviors of the OA-ZIF-8/GO with different GO contents as the lubricating oil additives were investigated comparatively using a four-ball tribological machine. The results showed that compared with the base oil, the OA-ZIF-8/GO with different GO contents when added to the base oil can all reduce friction and wear. The oil sample with 1.0 wt% of OA-ZIF-8/GO (53%) nanocomposite had the lowest friction coefficient and wear scar diameter. The reduction of friction coefficient and wear scar diameter is attributed to a stable protective film formed on the worn surface via physical deposition and a complicated tribochemical reaction. The study provides a strategy for fabricating graphene-based nanocomposites that were used for lubricating oil additives. [ABSTRACT FROM AUTHOR]

Oils and grease have beneficial effects on moving parts such as connecting rod, gears, shafts, and engine to reduce wear and friction. The properties of lubricants such as tribological and rheological properties are an important role in oils and grease characterization. Nano additives on lubricant oils play an important role in anti-wear; reduce the coefficient of friction and enhance the rheological properties. The Tribological and rheological behavior of base oil 15W50 which have different concentrations of multi-wall Carbon Nanotubes (MWCNTs) (0.5, 1, 1.5, and 2 wt%), and constant amount of graphene nanosheets (GNSs) (0.5 wt%) were investigated. This research is the first one in studying the effect of hybrid nano additives of (MWCNTs) and (GNs) on the tribological and rheological properties of lubricant oils. Tribological characterization was carried out on four ball testing model under different loads (200, 400, 600, and 800 N). The kinematic viscosity, flash point, pour point, and thermal conductivity of nanofluid added 15W50 lubricant are estimated and compared with base oil. The results showed that nano additives improve the wear scar and coefficient of friction by 78% and 48%, respectively. The flash point, thermal conductivity, kinematic viscosity, and pour point, were improved by 15%, 77%, 76.8%, and 20%, respectively compared with the base oil. The hybrid addition of CNTs/GNs nanoparticles enhanced the properties of 15W50 engine oil. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to evaluate carbon spheres as a green lubricant additive in 5W30 engine oil to reduce friction and wear. Carbon spheres with a diameter of ∼400 nm are synthesized from glucose by using a hydrothermal process. Lubrication is studied using a ball-on-disk tribometer by measuring the friction coefficient and wear in the boundary lubrication regimes. The worn surfaces were analyzed by Raman spectroscopy. Carbon spheres are found to be stably dispersed at 0.5 wt% concentration in base oil. The experiments revealed that carbon spheres are effective in reducing both friction and wear when lubricating by using base oil. Raman results show that the enhanced tribological performance is owing to a carbon-rich boundary film, the formation of which is attributed to the deposit of carbon particles during the sliding process. [ABSTRACT FROM AUTHOR]