Fe-Doped SnO₂ Rods as a Sustainable Lubricant Additive for Enhanced Tribological Performance: Optimal Selection Using Bootstrap Procedures

This study explores the effect of dispersion of Fe-doped SnO2 rods and SnO2 rod-based additives in transformer oil for lubricant applications. A notable reduction in friction and wear is achieved at a low weight percentage ∼0.025 wt % of additives along with oleic acid and oleyl amine as dispersants. Coefficient of friction, wear scar diameter, roughness, and wear depth for base oil are reduced by ∼32%, ∼15%, ∼73%, and ∼78%, respectively, by the addition of SnO2 rods. Surface functionalization with Fe ions further helps to significantly decrease these properties up to ∼40%, ∼43%, ∼77%, and 89%, respectively. A marginal reduction of ∼4%, ∼4%, ∼21%, and ∼10%, respectively, is observed when only dispersants are added. This is attributed to the complete filling of asperities and the polishing effect. The synergistic effect of Fe-doped SnO2 rods and organic dispersants induces low shear strength tribo-sintered patchy film formation on the tribo-contacts, thereby contributing to considerable enhancement in the lubrication behavior. High dispersion stability of the lubricants is observed. The results of robust bootstrap tests for analyzing the tribological data agree with the experimental outcomes. Ordering of materials and concentrations has helped in the selection of optimal lubricants. This work will stimulate the use of novel Fe–SnO2 based additives for efficient energy applications.