Design And Synthesis Of Magnetic Ionic Liquids And Their Tribological Properties Under External Magnetic Field

Magnetic lubricants are important materials used for addressing special lubrication and sealing problems.Currently,magnetic lubricants composed of magnetic particles dispersed in a lubricating base fluid a stability,low?no?vapor pressure,and the ability to be enriched and effectively recycled.Under the action of external magnetic field,it can be fully filled with lubricating surface to achieve continuous lubrication,which solves the problems of agglomeration,sedimentation and phase separation of magnetic particles in traditional magnetic lubricants.This is of great significance for solving the lubrication and sealing problems of moving parts of mechanical equipment under certain working conditions.?1?Five kinds of magnetic ionic liquids[P_4,4,4,14]₅[Dy?SCN?₈],[Hmim]₅[Dy?SCN?₈],P_4,4,4,14FeCl₄,HmimFeCl₄ and[P_4,4,4,14][Dy?hfacac?₄]were designed and synthesized.The structure,rheological properties,thermal stability and adsorption properties of magnetic ionic liquids were characterized by Fourier transform infrared spectrometer,synchronous thermal analyzer and rotational rheometer and so on.The results show that the[P_4,4,4,14]₅[Dy?SCN?₈]magnetic ionic liquid has the best thermal stability.When the mass loss of 5 wt%,the corresponding temperature is 347.2?.Magnetic ionic liquids[P_4,4,4,14]₅[Dy?SCN?₈]have the highest viscosity and shear stress within the set shear rate range?0.01Pa·s to 100Pa·s?.When cations are the same,the adsorbability of the selected three anions can be[Dy?SCN?₈]^5->[Dy?hfacac?₄]^—>FeCl₄^—.When anions are the same,the adsorption performance of P_4,4,4,14+is better than that of Hmin+.?2?The tribological properties of magnetic ionic liquid under magnetic field control were investigated.The effects of different cations and anions on the tribological properties of magnetic ionic liquids were compared,and the tribological properties of magnetic ionic liquids were compared with those of traditional magnetic lubricant.It is found that the magnetic ionic liquid,as a magnetic lubricant,has better tribological properties than the magnetic fluid of traditional magnetic lubrication materials under different sliding frequencies and loads.When cations are the same,[Dy?hfacac?₄]^—is not as good as[Dy?SCN?₈]^5-and FeCl₄^—.When the anions are the same,P_4,4,4,14+cations have better anti-friction and anti-wear performance than Hmim+cations.In addition,through the analysis of friction mechanism of different ionic liquids,it is found that ionic liquids[P_4,4,4,14]₅[Dy?SCN?₈]and ionic liquids[Hmim]₅[Dy?SCN?₈]have good and stable shear viscosity and excellent adsorption performance,which can form Physical adsorption lubrication film and friction chemical reaction film on the surface of friction pair,thus greatly reducing friction and wear.The anionic FeCl₄^—contained in ionic liquid P_4,4,4,14FeCl₄ and ionic liquid HmimFeCl₄ are prone to form corrosion on the surface of friction pairs in the air environment,thus aggravating the friction and wear during the friction experiment.Ionic liquid[P_4,4,4,14][Dy?hfacac?₄]has a small amount of adsorption on the friction surface,and the adsorption is not strong.Therefore,it has a large friction coefficient when it is used as a magnetic lubricant.?3?The tribological properties of[P_4,4,4,14]₅[Dy?SCN?₈],[Hmim]₅[Dy?SCN?₈]and magnetic fluid used as magnetic lubricants for steel-steel friction pairs under severe conditions in wide temperature range were studied.The results show that ionic liquids have better antifriction and antiwear properties than magnetic fluid at different experimental temperatures and loads.At low temperature,when the magnetic fluid is used as lubricant,no effective boundary lubrication film is formed on the surface of the wear scar.Ionic liquids form boundary lubrication films consisting of an adsorption film and a chemical reaction film.At high temperature,a boundary lubrication film consisting of Fe₃O₄ and a small amount of organic compound is formed by magnetic fluid.At the same time,due to the accumulation of Fe₃O₄ in the friction zone during the friction process,the large particles formed intensify the wear on the surface of the steel tribopair.The ionic liquids generate tribochemical reactions during the rubbing process,forming boundary lubricating film composed of Dy₂O₃,FeS,FeSO₄,nitrogen?phosphorus?-containing organic compounds and other organic compounds on the surface of the wear scar in a wide temperature range and reduces the friction and wear of steel-steel friction pairs.