Ultralow-friction and wear properties of IF-WS₂ under boundary lubrication

Tested in boundary lubrication, inorganic fullerene-like WS₂ nanoparticles used as additives in oil present interesting friction reducing and anti-wear properties. A dispersion with only 1 wt% of particles leads, from a contact pressure of 0.83 GPa, to a drastic decrease of the friction coefficient below 0.04 and to very low wear. High resolution transmission electron microscopy (HRTEM), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman Spectroscopy and video imaging were used to explain the lubrication mechanisms. A structural modification of fullerene-like nanoparticles into sheets during the friction test was evidenced to be the main effect at the origin of these properties.