Role of nano-sized materials as lubricant additives in friction and wear reduction: A review

Nanoparticles acting as additives to improve the tribological performance of base fluids have attracted much attention in the last several decades to lower wear loss, reduce the frictional force, enhance the service performance and extend the service life of sliding components. Different nanoparticles with various concentrations, mixing methodologies, surfactants and surface modifications have been frequently studied for in-depth understanding. The present research reviews the applications of nanoparticles as lubricant additives and their tribological properties. The common nano-sized materials, production processes, classifications of surfactants, surface modifications, friction reduction and anti-wear behavior of various nanolubricants are summarized. The potential mechanisms which can result in excellent tribological properties of nanolubricants are discussed. The limitations and challenges in applications and commercialization of nanolubricants are introduced. Finally, the recommendations for the development and the directions of future studies related to nanolubricants are provided. The information reported in the present work can be utilized as references in the development of high-performance nanolubricants and specific applications of nanolubricants in mechanical systems.