Friction and Wear Characteristics of Oil-Based ZnO Nanofluids

Nanofluids have been an active area of research for almost two decades due to their enhanced thermal conductivity compared to base fluids, but the study of nanofluids for tribological purposes has been slow, with problems encountered in dispersing and stabilizing nanoparticles in lubricants. In this research, the tribological properties of nanofluids were studied through experimental investigation by dispersing ZnO nanoparticles into paraffinic mineral oil. Nanoparticles were dispersed using an ultrasonic homogenizer. Oleic acid was used as the surfactant for the improved dispersibility and stability of nanofluids. A universal microtribometer with a ball-on-disk configuration was used to evaluate the friction properties between the moving mechanical components in the presence of nanofluids. The wear track was measured using a surface profiler, and the material deposition onto the sliding interface was analyzed using X-ray photoelectron spectroscopy. The effects of the surfactant, ultrasonication time, particle concentration, applied load, sliding velocity, and surface roughness on the friction and wear performance of nanofluids were investigated. The results showed that oil-based nanofluids with ZnO nanoparticles reduced friction and wear under certain conditions, and the application of oleic acid as a dispersant contributed to reducing friction to some extent and also improved the dispersibility and stability of the nanofluids.