Graphene Oxide Tribofilms Enhance the Scratch Resistance of Silica Glasses

Scratch-induced surface damages in glasses can significantly reduce the integrity of the glass components, leading to their eventual failure. Here, it is shown that the interfacial friction and wear on glasses during sliding in a liquid environment can be significantly reduced using aqueous graphene oxide (GO) dispersion. To this extent, the tribological generation of a GO-derived film from its aqueous dispersion during reciprocating sliding of a spherical sapphire probe over fused silica glass is demonstrated. The formation of dense GO tribofilm on the scratch track is confirmed by micro-Raman spectroscopy and atomic force microscopy analyses. Interestingly, the lubricious GO tribofilm is observed to reduce the frictional forces by about 80% compared to pure water. This reduced friction, in turn, limits the shear-induced tensile stresses in the wake of sliding contact, thereby minimizing the density of partial Hertzian cone cracks. Optical micrographs confirm the clear differences in the crack density and severity of sliding with and without the presence of the tribofilm. Furthermore, the effect of frictional forces on the wear and cracking behavior is established theoretically to supplement the understanding of friction’s role in determining the surface damages occurring during scratching. Overall, it is shown that the scratch resistance of glass surfaces in aqueous conditions could be significantly enhanced through a hitherto unknown tribofilm generation mechanism, thereby providing a fillip toward increasing the service life of glasses.