Performance evaluation of nano-enhanced coconut oil as sustainable lubricant

Abstract

Lubricants are used to reduce friction between contacting surfaces, especially involving mechanical parts. There has been considerable effort to develop a lubricant that will aid sustainable process and efficient performance. Because of their environmental friendliness, biodegradability, less toxic, and good lubricity, vegetable oils are considered a better substitute for mineral oils. However, their thermal and oxidative stability of vegetable needs to be improved for efficient lubrication. This research is aimed at developing and performance evaluation of vegetable oil-based nanolubricants with maghemite nanoparticles at different volume concentrations for sustainable lubrication. Maghemite nanolubricants were prepared by dispersion of the maghemite (γFe2O3) nanoparticles into vegetable oil at a different level of inclusions (0.1, 0.2, and 0.3 vol.%). The result indicated an improvement in the thermophysical properties of the nanolubricants with increased concentration, while an increase in temperature decreases their enhancement. The kinematic viscosity of coconut oil is enhanced with an increase of volume fractions that enable them to form a protective thin film under higher temperature operation. At the temperature of 80 °C, an increase of 30.68% was observed in the viscosity of nanolubricant over the pure base oil. The highest thermal conductivity enhancement over the base fluid is 7.33%, corresponding to a ratio of 1.079 times improved performance at a concentration of 0.3 vol.% inclusion over the pure base oil. The tribological properties showed that the wear scar diameter and coefficient of friction decrease with an increase of concentration. Thus making the addition of maghemite nanaoparticles in biolubricants a promising nanolubricant for sustainable machining.