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This study presents an approach to enhance the performance of lubricating oils through the environmentally friendly synthesis of cerium oxide (CeO2) nanoparticles using Moringa oleifera leaf extract. These biosynthesized nanoparticles were thoroughly characterized for their structural and thermal stability by utilizing X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The CeO2 nanolubricants, prepared at various concentrations, displayed significant improvements in viscosity, stability, and thermal conductivity. Specifically, the 0.15 wt% concentration achieved the best performance, reducing viscosity to 9.79 pascal-second (Pa·s) at 80 °C while exhibiting excellent dispersion and minimal sedimentation over time. The thermal conductivity tests revealed a notable 43% increase in heat transfer efficiency at higher nanoparticle concentrations. Tribological tests conducted using a tribometer demonstrated significant improvements in the lubrication properties. The nanolubricant with a 0.15 wt% concentration of CeO2 nanoparticles achieved the lowest friction coefficient, showing an approximate 26% reduction compared to the base oil, along with a notable decrease in wear rate. This study demonstrates the potential of biosynthesized CeO2 nanoparticles as effective, sustainable additives in lubricating oils, providing improved thermal, rheological, and tribological properties and marking a significant step toward eco-friendly lubrication solutions.

This Research aimed to improve the tribological properties of commercially available lubricating oil (5W-40) by incorporating CuO nanoplatelets (NPs) synthesized using a simple and cost-effective sonochemical method. To evaluate the performance of the nanolubricant, a reciprocating tribometer was indigenously designed and developed to measure the coefficient of friction (COF) and wear tracks between two AISI 1045 steel surfaces. The CuO NPs were characterized using XRD to confirm their purity and phase, while SEM and FE-TEM were utilized to study their morphology and composition. Raman spectroscopy was used to reveal three distinct Raman active peaks of CuO at 283, 330, and 616 cm−1. Zeta potential measurements demonstrated good dispersion quality, with a value of 92.0 mV for 0.1% concentration. SEM and FE-TEM analysis of the nanolubricant showed the formation of a tribo-film over the CuO NPs and adding 0.1% CuO NPs reduced COF by 32%. These findings suggest that incorporating synthesized CuO NPs in commercially available lubricating oil can enhance its tribological properties, leading to improved machine efficiency and lifespan, as well as reduced energy demand. Overall, the study demonstrates the potential benefits of using CuO nanoplatelets as an additive in lubricating oil, which could have significant implications for the development of more efficient nanolubricants.