Effect of Particle Concentration on Tribological Properties of ZnO Nanofluids

In this research, oleic acid surface-modified ZnO nanoparticles were successfully dispersed into 60SN base oil. The distribution of ZnO nanoparticles in the lubricant was tested by transmission electron microscopy. The friction and wear properties of nanofluids were evaluated with a four-ball tester, and the morphologies of wear scars were measured by a scanning electron microscope (SEM) and a surface profiler. Results show that oleic acid can improve the stability of ZnO nanoparticles in the lubricant; oil-based nanofluids with ZnO nanoparticles could remarkably reduce friction and wear. When the amount of oleic acid added was 8 wt% and ZnO nanoparticles was 0.5 wt%, the coefficient of friction and average diameter of the wear scars were minimum and the fluid exhibited better friction-reducing and antiwear properties.