Preparation And Tribological Properties Of Composite Nanoparticles As Lubricant Additives

The additives in traditional lubricating oil are mostly hydrocarbon compounds containing sulfur,phosphorus,chlorine and other substances.Such additives will release substances harmful to the environment while burning.Therefore,in order to achieve the objectives of environmental protection,energy conservation and emission reduction,people have begun to conduct in-depth research on nanomaterials,which has caused widespread attention in nanotribology.The composite nanoadditive can repair the worn surface through the synergistic effect between the particles to achieve the effect of reducing friction and wear.At the same time,the particles after wear will not have an impact on the environment.This paper proposes a composite particle with a soft shell-hard core structure to achieve excellent comprehensive performance of composite lubricating oil.Both ZnO and graphene as nanoadditives have excellent dispersion stability and anti-wear properties.As a framework,ZnO nanoparticles can support the formation of outer particles.As a flexible soft shell,graphene can form secondary adhesion after shedding,repair the worn surface and change the friction mode of the composite particles.The composite nanoadditive of soft shell-hard core structure has better dispersion stability and anti-friction and anti-wear performance than single additive.In order to realize the core-shell structure,this paper first prepared ZnO particles with four different morphologies such as prism-like,sheet-like,flower-like and rod-like by hydrothermal synthesis method.Using ZnO particles as the core,core-shell structure ZnO@graphene composite nanoparticles were prepared with surfactant PAH.Secondly,explored the dispersion stability and tribological properties of four morphology ZnO particles and core-shell structure ZnO@graphene particles.Through the sedimentation of nanoparticles in lubricating oil,the relative optimal concentration of the particles is obtained,and the stability of the lubricating oil under practical application is evaluated.Based on the comparison of the friction coefficient of the nanolubricant additive and the average wear scar diameter,the abrasion resistance of ZnO particles and core-shell structure ZnO@graphene composite particles was explored.The analysis of the surface morphology and composition of the wear scar after the lubricant wears reveals the anti-friction and anti-wear mechanism of the ZnO particles and the core-shell structure ZnO@graphene particles.In addition,explore the effect of temperature on the performance of ZnO@graphene and reveal the friction-reducing mechanism of ZnO@graphene under temperature conditions.The composite nanolubricant can show more stable comprehensive performance of lubricating oil in a wide temperature range closer to the actual service conditions.The developed core-shell composite nanoadditive constitutes a multi-component friction reduction and anti-wear synergistic lubricating oil system between physical deposition,secondary strengthening and chemical reaction,and has potential applications in mechanical equipment such as gearbox gear oil and other complex working conditions prospects.