Copper oxide nano-particles as friction-reduction and anti-wear additives in lubricating oil

Lubricants based on hydrocarbon-type mixtures do not satisfy all requirements of OEMs (Original equipment manufacturers) for modern applications. The usual solution is the addition of small amounts of certain additive compounds that render significant improvements in base oil properties such as oxidative degradation, tribological performance and other characteristics. This study examined the tribological behavior of copper oxide nanoparticles as additives in mineral based multi-grade engine oil. All tests were performed under varying loads and concentrations of nanoparticles in lubricating oil. The friction and wear experiments were performed using pin on disc tribotester. The results demonstrated that nanoparticle additives can effectively improve the engine oil lubricating properties. This is because nanoparticles enter the friction zone along with the flow of lubricant. They convert sliding friction into rolling friction, thus reducing the effective friction coefficient. This work also included an analysis of worn surface morphology by scanning electron microscopy. This surface examination revealed that nanoparticle additives resulted in smoother worn surfaces. From the viscosity test it can be inferred that viscosity of engine oil contains CuO nanoparticles is a function of nanoparticles concentration. Stribeck curves are used to reveal the lubrication regimes where the CuO nano-particles are most effective. It was found that the addition of CuO nanoparticles to the base oil results in up to 50% reduction in coefficient of friction in the mixed lubricant regime.