Improving tribological performance of lubricating oil using functionalized nanodiamonds as an additive material

Abstract

This study exposed the effect of detonated nanodiamonds modified by polyvinylpyrrolidone PVP as a surface stabilizer on the tribological and thermal properties of engine oil. These commercial DNDs were dispersed in the oil at low concentrations, only 0.001 wt% to 0.005 wt%, taking advantage of their high surface area and unique carbon structure to improve lubrication performance. The presence of functional groups and crystalline characteristics for DNDs was confirmed by FTIR and XRD analyses respectively, while SEM imaging coupled with 3D optical profilometry gave information on both surface morphology and wear profile. Zeta potential measurements indicated a significant increase in dispersion stability, with values changing from 14.3 mV to −27.4 mV, ensuring long-term suspension and preventing aggregation of the nanoparticles. Tribological testing showed a substantial reduction in surface roughness, with treated samples exhibiting surface roughness approximately six times lower than those observed with base oil. The mass wear rate was reduced after using nano-lubricant 0.005 wt% by 260%. The thermal stability of the lubricant also improved, as reflected by a 2.2% increase in flashpoints. Furthermore, kinematic and dynamic viscosities increased by 10.87% and 4.95%, respectively, suggesting an improvement in oil film strength and load-bearing capacity. The synergistic effects of DND dispersion, surface interaction, and film formation contributed to reduced friction, enhanced wear resistance, and better thermal management. These findings support the potential of PVP-modified DNDs as effective nanoscale additives for extending engine life and improving lubrication efficiency under demanding operating conditions.