Molecular Dynamics Simulations of Nanolubricant Films of Alkali Glasses under Sliding Asperity Contacts

In this paper, the tribological performance of two alkali glass lubricants (sodium phosphate and sodium silicate) at the nanoscale were compared in a reactive molecular dynamics simulation. The obtained results reveal that there was a layering structure of sodium on an atomic smooth as well as a nanorough iron oxide surface. The peak of the Na profile on the smooth surface was larger than that found on the rough one, and phosphate glass produced a larger atomic layering degree of Na density profile than silicate. Moreover, sodium phosphate glass has a better tribological performance than that of silicate lubricant based on shear stress and wear of asperities. It was also found that the asperities were deformed, flattened, and stretched out during the sliding contacts. The density profiles of asperities revealed three separate atomic regimes with a different density of asperities atoms. At the nanoscale level, sodium silicate glass resulted in more wear than sodium phosphate.