Improvement of the lubrication properties of grease with Mn3O4/graphene (Mn3O4#G) nanocomposite additive

Abstract

Although grease can effectively lubricate machines, lubrication failure may occur under high speed and heavy load conditions. In this study, Mn3O4/graphene nanocomposites (Mn3O4#G) were synthetized using a hydrothermal method as lubricant additives. The lubrication properties of compound grease with Mn3O4#G nanocomposite additive under heavy contact loads of 600–900 N (3.95–4.59 GPa) were investigated. First, the nanocomposites were dispersed into L-XBCEA 0 lithium grease via successive electromagnetic stirring, ultrasound vibration, and three-roll milling. Compound grease with additives of commercial graphene (Com#G) was also investigated for comparison. Tribological test results revealed that the trace amounts of Mn3O4#G (as low as 0.02 wt%) could reduce the coefficient of friction (COF) of grease significantly. When the concentration of Mn3O4#G was 0.1 wt%, the COF and wear depth were 43.5% and 86.1%, lower than those of pure graphene, respectively. In addition, under the effect of friction, the microstructure of graphene in Mn3O4#G nanocomposites tends to be ordered and normalized. Furthermore, most of the Mn3O4 transformed into Mn2O3 owing to the high temperature generated from friction. Using the Ar gas cluster ion beam sputtering method, the thickness of the tribofilm was estimated to be 25–34 nm. Finally, the improvement of the lubrication properties was attributed to the synergistic effect of the adsorbed tribofilm, i.e., the graphene island effect and the filling effect of Mn3O4#G.

Friction and Wear Behaviors of Fe-19Cr-15Mn-0.66N Steel at High Temperature

“…Among them, Mn has a stronger affinity with O compared to Fe, so the oxides of Mn, i.e., MnO and Mn 2 O 3 , are more abundant [23,24]. The latter, in particular, is generated in large quantities and is beneficial for lubrication during friction [55]. In addition, at 500 • C, Fe 2 O 3 is easily transformed into Fe 3 O 4 , which has lower hardness than Fe 2 O 3 , and also plays a certain protective effect [24,56].…”

Study on Frictional Properties of Fine Powder Materials

“…The choice of the type of additives depends on the technical condition of the engine and operating conditions [7,8].…”

“…Many scientific organizations are currently investigating the tribological properties of oils and lubricating systems [1][2][3][4][5]. The compositions of additives to oils are continuously improved and their properties are enhanced [6][7][8][9][10]. Some studies are aimed at developing new environmentally friendly materials [11][12][13][14].…”

Shear-Induced Interfacial Structural Conversion Triggers Macroscale Superlubricity: From Black Phosphorus Nanoflakes to Phosphorus Oxide

“…1 Aiming to address these problems, researchers have made great efforts to develop advanced lubricants to reduce both energy dissipation and wear, while also enhancing durability. 2 The concept of superlubricity, first proposed in 1990, 3 refers to the condition with a sliding coefficient of friction (COF) in the order of 0.001, which can significantly suppress the energy dissipation and wear loss simultaneously. Superlubricity can be achieved using solid coatings such as diamond-like carbon under various environments.…”