Study On Friction Characteristics Of Molybdenum Disulfide And Its Composites Under External Electric Field

The molybdenum disulfide?MoS₂?film material is an excellent low-dimensional nano material with excellent electrical and mechanical properties.MoS₂ is also often used as a lubricating additive in large mechanical equipment due to its excellent lubricating properties.In this paper,the mechanical properties such as friction and adhesion of MoS₂ film are studied from the microscopic point of view.The friction characteristics of composites doped with MoS₂ are studied from a macroscopic perspective.First,we prepared a stepped MoS₂ film by mechanical stripping method with different thicknesses?single layer,double layer,few layers,etc.?.The PDMS film was secondarily transferred onto a conductive substrate,wherein the structure of the substrate was 100 nm of Au/300 nm of SiO₂/Si.The Au substrate was connected to the internal power supply of the atomic force microscope?AFM?by wires,and the positive and negative voltages were applied through the conductive probe and the Au substrate to study the influence of the normal electric field on the surface morphology,friction and adhesion of the MoS₂ film.It was found that both friction and adhesion increase with increasing voltage,independent of the positive and negative directions of the voltage.The result of adhesion is the same as the friction.The MoS₂ film can withstand a lower voltage limit in the 100 nm scale electric friction test.The wear and tear characteristics of MoS₂ were studied by applying positive and negative voltages to the substrate,and it was found that the voltage would reduce the wear rate.However,the voltage is too large to destroy the surface of the sample.The surface potential and phase diagrams of the samples were analyzed using a scanning Kelvin microscope.The case of charge accumulation occurs.Raman analysis also showed an oxidation reaction in the damaged area.In further macroscopic friction experiments,a MoS₂-copper-zinc composite was prepared by powder metallurgy.Through the reciprocating friction of the ball disc,the friction properties of the composite material using umt-5 to study the friction properties of MoS₂ have significantly improved the friction properties of the composite.The electric field increases the coefficient of friction?COF?and wear rate of the composite.The morphology and element composition and distribution of the wear scars were analyzed by SEM and EDAX.It was found that the Fe element was found in the area of the S element.The results indicate that FeS_x was generated.The increase in voltage will promote the reaction of the steel ball with the S element.The FeS film is formed on the surface of the steel ball,and the increase of the COF is effectively suppressed.Further in the XPS analysis,copper was found to be oxidized in the 9 wt%MoS₂ composite.This is because the MoS₂ content is too high and S will corrode Cu,resulting in an increase in the COF and wear rate.Among them,when the concentration of MoS₂ is 3wt%,the friction performance of the composite is the best.