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In the field of tribology, graphene has become a potential candidate material for lubricating oil and lubricant additives at multiple scales due to their high thermal conductivity and impermeability. In order to further improve the anti-wear and anti-friction properties of graphene, Ni/polydopamine-functionalized graphene composites (Ni/pDA/GR) were successfully prepared by a wet chemical reduction method. In this paper, The GR, pDA/GR, Ni/GR and Ni/pDA/GR were added into the base oil as lubricant additives respectively to explore their lubrication properties. The results showed that the friction coefficient of Ni/pDA/GR group is the lowest, which is about 15 % lower than base oil. Ni/pDA/GR also exhibited good wear resistance in wear tests. At the same time, the optimal concentration of the composite is 0.1 wt% in base oil, and the optimal lubrication load is 5 N. [Display omitted] • Polydopamine was used to modify graphene which is facile and environmental. • Spherical Ni NPs can improve the load-bearing capacity of base oil. • The composite can improve the anti-wear and anti-friction performance of base oil. • We report a facile method to prepare metal-nanomaterial composites. [ABSTRACT FROM AUTHOR]

MoS 2 nanoparticles have been extensively applied as lubricating additives enhancing tribological behavior of base oils over the past decades. But how MoS 2 nanoparticles specially behave in formulated engine oil is still poorly understood, and even some contradictory conclusions have been obtained. Herein, ultrathin MoS 2 nanosheets were synthesized through a chemical method and their friction-reducing and antiwear capabilities in formulated engine oil was investigated. In addition, the tribofilm formation, interface structure and friction mechanism were studied in terms of the surface characterization and chemical analysis. The research contributed to comprehending the lubrication mechanism of MoS 2 nanoparticles within formulated engine oil. • The ultrathin shape of MoS 2 nanosheets with 1–4 layer were fabricated. • Ultrathin MoS 2 nanosheets showed positive tribological response in formulated engine oil. • Ultrathin MoS 2 nanosheets restrained the oxidation of substrate at high temperature. • A tribofilm with embedment of MoS 2 nanosheets was formed to protect rubbing surfaces. [ABSTRACT FROM AUTHOR]

Natural serpentine powders are applicable as additives for various lubricating oils. However, no uniform theories explain their tribological performance, lubrication, and wear mechanism, especially their self-repairing mechanism. Herein, the influence of different nano serpentine powders (NSPs) contents in liquid paraffin on the friction and wear characteristics of steel balls and the self-repairing process of NSPs on the worn surface were studied. Results show that the optimal amount of NSPs was 0.5 wt %. Relative to those of the base oil, the friction coefficients and wear spot diameters were reduced by 22.8% and 34.2%, respectively. Moreover, the long-term tribological test shows that the wear scar diameter decreased slightly after 3 h, reaching the state of dynamic balance between wear and repair. The outstanding tribological performance should be attributed to the formed bilayer tribofilm, the first layer of which contains nanoparticles surrounded by lubricants and the second layer of which contains nanoparticles compacted onto the surface of the steel ball. [ABSTRACT FROM AUTHOR]