In this study, the nanocomposites of MoS₂ nanoparticles (NPs) grown on carbon nanotubes (MoS₂@CNT), graphene (MoS₂@Gr), and fullerene C60 (MoS₂@C60) were synthesized, characterized, and evaluated for potential use as lubricant additives. By using the benefit of the synergistic effect between MoS₂ and carbon nanomaterials (CNMs), these nanocomposites can be well dispersed in polyalkylene glycol (PAG) base oil and show superior stability compared with pure MoS₂ NPs. Moreover, the dispersions of MoS₂@CNT, MoS₂@Gr, and MoS₂@C60 added in PAG have noticeably improved friction reducing and antiwear (AW) behaviors at elevated temperature for comparison with that of PAG and PAG containing CNT, Gr, C60, and MoS₂ NPs, respectively. The enhanced lubricating properties of these nanocomposites were also elucidated by exploring the tribofilm formed on the disc.

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, MoS₂ and WS₂ 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]PF₆), forming homogeneous dispersions exhibiting long-term stabilities. Tribological test results indicate that the addition of MoS₂ and WS₂ 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 ℃. 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 MoS₂ and WS₂ QDs at the steel/steel contact surfaces, but also by the tribochemical reaction between MoS₂ or WS₂ and the iron atoms/iron oxide species.