AFM applications for analysis of fullerene-like nanoparticles

In the past few years, inorganic fullerene-like WS2 and MOS2 nanoparticles (IF) with structures closely related to (nested) carbon fullerenes and nanotubes have been synthesized. Preliminary friction experiments with IF added to oil showed lubricating properties superior to those of layered commercially available WS2 and MOS2 solid lubricant powders in a definite range of operating conditions. The analysis of the IF nanoparticles showed that most, if not all pristine nanoparticles were closed and hollow, having nearly spherical shape the average size of which was close to 120 nm for IF-WS2, and about 50 nm for IF-MoS2- It was found that these nanoparticles are capable of withstanding a severe hydrostatic pressure, caused by compression. Detailed structural studies revealed a deformation of the IF nanoparticles and breakage of their outer shells under compression. The surface topography of the samples before and after the friction tests was studied with scanning probe microscope (SPM) DI Dimension 3100. Friction and wear of steel and ceramic pairs lubricated with oil+ IF lubricant have been studied. On the base of atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoemission spectroscopy (XPS) analysis it was concluded that the islands of destroyed IF nanoparticles could provide improved tribological properties of the contact under severe contact conditions.