In situ synthesis of Mn₃O₄/graphene nanocomposite and its application as a lubrication additive at high temperatures

Graphene-based nanoadditives are widely used in the field of lubrication due to their two-dimensional (2D) structure and excellent mechanical properties. However, researches on the high-temperature performances and rheological properties of graphene-based lubricant are still insufficient. In this study, Mn₃O₄/graphene (Mn₃O₄#G) nanocomposite is synthesized in situ by hydrothermal method, and it is used as nanoadditive in lithium grease. When the concentration of Mn₃O₄#G is 0.03 wt%, the coefficient of friction (COF) and wear scar depth can be reduced by 35% and 76% (100 °C, 150 N), respectively. In addition, when the temperature is 120 °C, the grease with 0.03 wt% Mn₃O₄#G can still achieve stable lubrication performance. On the contrary, pure grease (P.G) has already failed to lubricate at the temperature of 80 °C. According to the computational fluid dynamics (CFD) results, the shear thinning phenomenon of the grease can be observed. And the central suction effect occurring in the friction area will be conducive for the nanoadditives to enter the friction contact area.