Direct observation by in situ transmission electron microscopy of the behaviour of IF-MoS2 nanoparticles during sliding tests: influence of the crystal structure
Résumé
Direct observation of the behaviour of individual inorganic fullerenes (IF)-MoS2 nanoparticles in a sliding interface is essential for the understanding of the influence of the intrinsic characteristics of the nanoparticles on their lubrication mechanisms, when they are used as additives in lubricant oil. In this work, in situ transmission electron microscopy sliding tests were performed on two different types of MoS2 nanoparticles synthesised by two different methods. It is shown that the IF-MoS2 nanoparticles having perfect structure with a high crystalline order and without defects are able to roll and to slide under the combined effect of pressure and shear stress, whereas the IF-MoS2 nanoparticles containing many defects exfoliate immediately in the same conditions to deliver MoS2 layers covering the mating surfaces. A link between these results, the lubrication mechanisms of the nanoparticles and their tribological properties at the macro-scale was established, proving that the lubrication mechanisms of fullerenes depend on their intrinsic characteristics.