| Water-lubricated ceramic bearings have many excellent properties,such as high hardness,corrosion resistance,wear resistance and environmental-friendly property.Silicon nitride（Si3N4）is an ideal ceramic bearing material,since it can achieve extremely low friction coefficient under water lubrication.As a both economical and environmentally friendly material,silica（Si O2）nanoparticles have been found to play an important role in improving lubrication performance when used as lubricant oil additives.In this research,the object was water-lubricated silicon nitride ceramics.Silica nanoparticles were used as aqueous lubricant additives to explore the influence of nanoparticle parameters on the tribological properties.A variety of characterization analyses were adopted to establish the lubrication mechanisms of silica nanoparticles.In this study,silica nanoparticles with different particle sizes were synthesized by St（?）ber method.Different functional groups were linked to the nanoparticle surfaces by silane coupling agents.Silica nanoparticles were purified and transferred to deionized water through azeotropic distillation.Multiple characterization methods were adopted to investigate the preparation method of silica nanoparticles used as lubricant additives for water-lubricated ceramics.Tribological experiments were carried out using self-mated silicon nitride ball-on-disk friction pair.When silica nanoparticles were used as aqueous lubricant additives,it was found that silica nanoparticles can effectively reduce wear and friction in a short running-in period.In order to investigate the influence of nanoparticle parameters on the tribological properties,different functional groups,particle sizes and additive concentrations were tested respectively.Optimal lubrication parameters were explored.The 100 nm silica nanoparticles showed the best friction reduction property.The amino modified silica nanoparticles exhibited good lubrication performance under different loads and sliding speeds.In particular,under severe working conditions such as high load,amino modified silica nanoparticles can effectively reduce wear and lead to a great drop of friction coefficient,achieving superlubricity.With the increase of additive concentrations,the lubrication performance exhibited a trend of first increasing and then decreasing,so there existed an optimal concentration.Furthermore,compared with zinc oxide and titanium dioxide nanoparticles,silica nanoparticles got a distinct advantage over them when used as aqueous lubricant additives.The wear ceramic surfaces lubricated by amino modified silica nanoparticles aqueous lubricants were analyzed by a variety of characterization methods.Therefore,the lubrication mechanisms of silica nanoparticles on ceramic surfaces were constructed.The silica nanoparticles can be effectively adsorbed and deposited on the ceramic surface,greatly improving the antifriction and antiwear properties of lubricants via the synergic lubricating effect of filling mechanism,fill-forming mechanism and electric double layer.The research systematically explored the tribological properties of silica nanoparticles as aqueous lubricant additives under different friction conditions.The research findings will be of great significance for the application of silica nanoparticles lubricant additives and the development of ceramic water-lubrication technology. |
