Enhancing Tribological Properties of Lubricated Contacts via Synergistic Interactions of Green Silica Nanoparticles and ZDDP

Zinc dialkyl dithiophosphate (ZDDP) anti-wear lubricant additive contributes to significant harmful emissions and its replacement has become a priority. In this study, green silica nanoparticles were synthesized and optimized for concentration to serve as hybrid additives alongside ZDDP in lubricants, aiming to mitigate environmental concerns. A combination of 0.5 wt.% silica nanoparticles, 0.5 wt.% oleic acid, and 0.75 wt.% ZDDP demonstrated notable improvements, reducing ZDDP usage by ~25% while achieving significant tribological enhancements. At room temperature, friction decreased by ~60%, and wear reduced by ~70%, while at 100 °C, friction decreased by ~80%, and wear reduced by ~96%. Advanced characterization techniques such as FESEM with EDS mappings, EPMA, and TOF-SIMS were employed to elucidate the underlying mechanisms for surface protection.