This chapter investigates the tribological properties of tungsten disulfide (WS2) coatings or IF-WS2 coatings in an ultrahigh vacuum and at different temperatures. Friction experiments were performed in an analytical ultrahigh vacuum tribometer consisting of a linear reciprocating pin-on-flat configuration installed directly inside an ultrahigh vacuum chamber. A pure and stoichiometric MoS2 coating that contains below 1% oxygen could exhibit an extraordinarily low friction coefficient. However, the WS2 coating prepared for the experiment was considered to have a significant percentage of oxygen. Therefore, the result indicates that even a disulfide film without special preparation could achieve a superlow friction at cryogenic temperatures. Inorganic fullerenes exhibited better tribological properties than the lamellar structure when they were used as additives to lubricating base oils under boundary lubrication or mixed lubrication. The lubrication performance was based on an exfoliation mechanism of the IF into MS2 single sheets. The sheets generated could then be in incommensurate conditions.
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