Morphology Evolution of ZnO Submicroparticles Induced by Laser Irradiation and Their Enhanced Tribology Properties by Compositing with Al₂O₃ Nanoparticles

In this paper, ZnO submicrospheres are prepared by a simple laser‐stimulated surface tension energy release strategy, which is a very convenient method for growing inorganic oxide spheres with high melting points. The detailed morphology evolution of ZnO particles is investigated by changing the laser fluence. The formation of spherical morphology is due to the particle spherizing and/or coalescence as a result of surface area minimum and release of surface tension energy when particles are heated by laser irradiation. ZnO submicrospheres can effectively reduce the friction coefficients when used as lubricating oil additives, which exhibit a clear morphology‐dependent property. But the wear becomes worse due to its small hardness. However, the compositing ZnO submicrospheres with Al₂O₃ nanoparticles as the lubricating oil additives can notably improve both the friction‐reduction and anti‐wear properties. The surface analysis of the thrust rings suggests that rolling friction becomes dominant instead of sliding friction and these composite particles squeezed into the grooves on the rubbing surfaces can reduce wear.