Sedimentation of IF-WS2 aggregates and a reproducibility of the tribological data

Inorganic fullerene-like (IF) solid lubricant nanoparticles and nanotubes with extremely useful mechanical and tribological characteristics have been realized, offering a plethora of new applications for these nanomaterials. The IF nanoparticles were found to be in the aggregated state. It is expected that the size of the aggregates and their distribution determine the penetration and entrapping of IF nanopowder into the interface. The main goal of the present work is to elucidate the effect of the mixing time of IF-WS2 nanomaterial in the oil on the size of the IF aggregates and their influence on the friction and wear. The fraction of small aggregates increases and that of the large aggregates decreases with longer mixing time. Consequently, the spread of the tribological results diminishes with the lengthening of the mixing time. The reproducibility of the friction results for the pairs lubricated with oil + IF nanoparticles is determined by distribution of the IF aggregates in the lubricant and the size of the solid lubricant aggregates. (c) 2006 Elsevier Ltd. All rights reserved.