Anti-wear behavior of 1-octanethiol and tween-80 capped ZnO nanoparticles as lubricating oil additives

1-Octanethiol (OT) and tween-80 (TW) coated zinc oxide nanoparticles (OT-ZnO and OT/TW-ZnO NPs) were prepared and investigated as potential lubricant additives in a 5W-30 commercial engine oil to minimize wear. It was observed that the synthesized OT-ZnO NPs exhibited a moderate dispersity in a base oil, while the TW-loaded OT/TW-ZnO NP exhibited better colloidal stability and lubrication performance. Wear reduction was observed with an average value of 17% and 22% compared to the 5W-30 oil when 0.025 (wt.%) OT-ZnO and 0.050 (wt.%) OT/TW-ZnO NPs were used as additives. SEM images revealed that the synthesized OT-ZnO NPs were nearly spherical with a size of about 87 nm, while OT/TW-ZnO NPs were flower-like shaped with an average particle size of 819 nm. According to EDX analysis, the test metals showed the presence of OT-ZnO and OT/TW-ZnO NPs on the worn surface at a minimum content (wt.%) of 0.58 and 0.35, respectively.