Study On The Synergistic Anti-wear Properties Of Magnesium Silicate Hydroxide Nanoparticles And ZDDP

Tribology is a science and technology for studying friction,wear and lubrication between surfaces of relative motion.Meanwhile,reducing friction and wear has always been an eternal research topic all over the world.Lubricant additives such as zinc dithiophosphate(ZDDP)have been around for more than 50 years and still is the most important anti-friction and anti-wear additives.ZDDP forms slick,highly protective films on rubbing surfaces,but they can poison catalysts and cause environmental pollution Therefore,it is of great significance to find a new type of "green" lubricant anti-wear additive which can replace or partly replace ZDDP.Synthetic magnesium silicate hydroxide(MSH)nano-particles have excellent tribological properties as anti-wear additives owing to its unique layered structure.This article will study the synergistic tribological properties of MSH and ZDDP.Firstly,hydrothermal synthesis method was used to synthesize MSH nano-particles at reaction temperature of 200?,rotational speed of 450r/min,and reaction time of 12h.After that,the structures and morphologies of these nanoparticles were characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD)patterns.Secondly,the tribological properties of MSH nano-particles as lubricant additives under different experimental conditions were studied.The dispersity of MSH nano-particles in PAO base oil were studied by static precipitation method under different disperants.The tribological tests were carried out by a four-ball friction and wear tester to obtain MSH with optimal stability and tribological properties.On this basis,the effects of the weight percentage of dispersant and additives on the tribological properties of MSH under different applying loads and rotational speeds were investigated.Finally,the tribological properties of the traditional anti-wear additive ZDDP were tested and compared with synthetic MSH nano-particles as additives in PAO base oil under certain conditions.Besides,the tribological properties of ZDDP compounded with the MSH as co-additives in the base oil were studied.The effects of the addition of ZDDP and the amount of dispersant on the tribological properties of the co-tribological properties were investigated.By means of SEM and X-ray energy dispersive spectrometry(EDS),the morphologies and elemental analyses of the worn surfaces were executed,meanwhile,the anti-wear mechanisms were preliminarily explored.Results showed that the type of dispersants have significant effects on the dispersity and tribological properties of synthetic MSH nano-particles.The dispersity of nanoscale MSH can be greatly improved by a modification of a dispersant on the surface,meanwhile,the friction-reduce stability and anti-wear behavior were greatly improved in the process of friction.With the increase of weight percentage of dispersant,the wear scar diameter of samples lubricated in oil added MSH decreased first and then increases.The change of the amount of MSH nano powder in oil has no significant influence on the size of the wear scar diameter,and it has a better anti-wear property at conditions of high speed and high load,high speed and low load,medium speed and high load.Compared with ZDDP,nano-powder and Span80 have lower friction coefficient and higher stability in base oil PAO10,resulting in reduced wear.ZDDP and MSH nano-particles have excellent friction-reduce and anti-wear performances,and the worn surfaces are relatively smoother than that lubricated in pure base oil attributing to a tribofilm containing Fe,C,O,Mg,Si,P,S,Zn and other elements formed on the rubbing surfaces.