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Herein, molybdenum disulfide (MoS2) and tungsten disulfide (WS2) quantum dots (QDs) are prepared by a facile and green technique, and characterized by microscopy and spectroscopy. The resulting products display exceptional stability in polyalkylene glycol (PAG) base oil, and are used for the first time as friction reducing and antiwear additives in PAG for steel/steel contact. Tribological measurements indicate that the stable dispersion consisting of PAG mixed with MoS2/WS2 QDs exhibits significant tribological properties compared with pure PAG and PAG containing MoS2/WS2 QDs nanosheets under different loads at elevated temperatures. The excellent tribological behaviors of MoS2/WS2 QDs are attributed to the formation of a boundary lubrication film, which can be generated not only by the physical entrapment of MoS2/WS2 QDs at the ball‐disk contact surfaces, but also by tribochemical reaction between MoS2/WS2 and the iron atoms/iron oxide species.

Red phosphorus (P) was covalently attached to graphene nanosheets (Gr) using high-energy ball-milling under a nitrogen atmosphere.

Nanosized MoS2 on graphene was firstly investigated in the lubrication field and exhibited excellent tribological performance in perfluoroalkylpolyether under high vacuum.

Herein, MoS 2 nanosheets (MoS 2 ) densely modified with n-octadecyl mercaptan (NOM) are used as effective friction-reducing and antiwear additives. A facile and green strategy is employed to prepare the organic−inorganic hybrid nanosheets (MoS 2 −NOM) by mussel-inspired chemistry combining with the Michael addition reaction. When MoS 2 −NOM nanosheets are added in poly-α-olefin (PAO) 10, they form a homogeneous and stable dispersion compared to the unmodified MoS 2 . Tribological measurements show that the dispersion of PAO 10 containing 1 wt % MoS 2 −NOM displays dramatic reductions in the friction coefficient (∼53%) and wear volume (∼92%). The exceptional tribological behaviors of MoS 2 −NOM are ascribed to the formation of a boundary protection film during tribochemical reactions. Further investigations display that the addition of 1 wt % MoS 2 −NOM can efficiently improve the maximum load-carrying capacity and the high-temperature lubricating property of PAO 10 base oil, which is likely due to the formation of n-octadecyl thioether on the surface of MoS 2 after the modification of MoS 2 −polydopamine (PDA) with NOM via Michael addition.

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Despite excellent tribological behaviors of ionic liquids (ILs) as lubricating oils, their friction-reducing and anti-wear properties must be improved when they are used under severe conditions. There are only a few reports exploring additives for ILs. Here, MoS 2 and WS 2 quantum dots (QDs, with particle size less than 10 nm) are prepared via a facile green technique, and they are dispersed in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm]PF 6 ), forming homogeneous dispersions exhibiting long-term stabilities. Tribological test results indicate that the addition of MoS 2 and WS 2 QDs in the IL can significantly enhance the friction-reducing and anti-wear abilities of the neat IL under a constant load of 500 N and a temperature of 150 °C . The exceptional tribological properties of these additives in the IL are ascribed to the formation of protective films, which are produced not only by the physical absorption of MoS 2 and WS 2 QDs at the steel/steel contact surfaces, but also by the tribochemical reaction between MoS 2 or WS 2 and the iron atoms/iron oxide species.

The tribological performances of perfluoroalkylpolyethers (PFPE) with graphene (Gr), WS2, and the mixture of Gr and WS2 (Gr + WS2) before and after ultraviolet (UV), atomic oxygen (AO), and proton (Pr) irradiations were investigated. The composition and structure of PFPE, Gr, WS2, and Gr + WS2 were also analyzed to understand the effects of irradiation on the tribological behaviors of PFPE with additives. The results indicated that serious deterioration and degradation of PFPE took place and Gr was transformed to amorphous carbon after Pr irradiation, and surface oxidation of WS2 occurred under the irradiations of AO and Pr. Moreover, compared to PFPE and PFPE additized with Gr and WS2, PFPE with the addition of Gr + WS2 exhibited excellent friction and wear reduction before and after UV and AO irradiations. Graphical Abstract