Study On The Influence Of Ionic Liquids On The Dispersibility And Lubricity Of Graphene Lubricants

Friction is inevitable in daily life and industrial production.New nano-lubricating materials with anti-friction,anti-wear and repair functions have become a hot spot in the field of friction and lubrication in recent years.If graphene lubricating oil is used instead of traditional lubricating oil to lubricate the machine tool,it will significantly reduce the wear and heat generation of the machine tool due to friction,further reduce the thermal deformation of the equipment,and improve the machining accuracy and work efficiency of the machine tool.However,due to the unique benzene six ring structure,graphene has strong van der Waals forces between atoms,making it difficult to be interrupted and easy to agglomerate,resulting in poor solubility of graphene in base oil,not only difficult to play graphene itself Excellent performance,and will cause damage to the machine tool and environmental pollution.In this study,ionic liquid was used as a graphene lubricant modifier to construct an ionic liquid/graphene lubricant system to solve the problem of poor graphene dispersion,and to study its dispersion stability and tribological behavior.The main research contents are as follows:（1）Using MS simulation software to calculate the van der Waals force,root mean square shift and dispersion between graphene and n-hexadecane(C₁₆H₃₄)in graphene lubricants under different ionic liquids by combining molecular dynamics and quantum chemistry The electronic properties of the interaction system between ionic liquid and graphene reveal the microscopic dispersion mechanism of ionic liquid in graphene lubricant.The results show that imidazole-based ionic liquids easily formΠ-Πinteractions with the surface of the graphene sheet due to its cyclic structure,thereby transferring electrons to the graphene surface,and dispersing the graphene through electrostatic mutual repulsion.（2）Verify the conclusions obtained by simulation through experiments,The ionic liquid was added to the graphene lubricating oil,and by investigating the ionic liquid concentration,type,ultrasonic conditions and other factors,it was found that the dispersion stability of the imidazole-based ionic liquid/graphene lubricating oil with an ultrasonic time of 60 min and an ultrasonic power of 600 w Compared with graphene lubricants,it is significantly improved.（3）Using MS simulation software to explore the effects of different types of ionic liquid/graphene lubricants by analyzing the van der Waals energy,shear stress,solid film thickness,and temperature distribution on the film thickness between the lubricant and the friction pair Adsorption on Si₃N₄-GCr₁₅friction pair.The results show that after adding ionic liquid,the adsorption energy of the lubricating body on the surface of silicon nitride and bearing steel increases.In addition,the thickness of the solid film formed by the imidazole ionic liquid/graphene lubricating oil and the van der Waals force between the friction pair are higher than those of the quaternary phosphonium salt ionic liquid.The imidazole ionic liquid has lower shear stress with the upper and lower walls.It shows that ionic liquid can improve the tribological properties of graphene lubricants.（4）In order to further explore the relationship between the dispersion stability of the ionic liquid/graphene lubricant and the lubricating effect,this paper will conduct the friction and wear tests of the ionic liquid/graphene lubricant after ultrasonic dispersion under different speed and load conditions.The friction coefficient is used to characterize the lubricating effect of the ionic liquid/graphene lubricant under various ultrasonic conditions.The results show that due to the dispersion of the ionic liquid,the graphene lubricant forms a dense and uniform lubricant film adsorbed on the surface of the friction pair,thereby reducing the friction coefficient,and the imidazole ionic liquid/graphene lubricant has a better lubricating effect.Compared with graphene lubricants,the friction coefficient is reduced by about 30%.The addition of ionic liquids to graphene lubricants not only improves the problem of graphene’s easy agglomeration,but also effectively improves the lubricating properties of graphene lubricants due to its self-lubricating properties.Although the research on ionic liquids is still in its infancy in the field of tribology,ionic liquids will surely become the most promising new composite lubricating material together with graphene by virtue of their excellent properties.