Preparation And Tribological Properties Of Graphene-based Solid Lubricants

In recent years,the construction of binary nanocomposites can significantly improve the shortcomings of the single functional material,which has become a hot topic in the field of material science.In tribology,a number of nano-lubricants or lubricating additives are prepared by nano-composite technologies with some nanoparticles?such as transition metal sulfides,rare earth oxides?and auxiliary reinforced materials?such as graphene?,which can well meet the requirements of friction-reducing and wear-resistant about mechanical equipment in extreme environment?high load,high vacuum,high temperature,low temperature and so on?.It shows excellent tribological properties.Among them,graphene?RGO?has become one of the most widely used materials in the research of composite materials because of its ultra-thin,two-dimensional structure and excellent comprehensive properties.On this basis,The research in this paper aims at solve the problems that traditional lubricating materials are easily aggregated,their friction-reducing and wear-resistant abilities are reduced in the extreme environment.A new type of solid nano lubricating material is constructed by the strengthening material of graphene,which friction-reducing and wear-resistant performance and mechanism are studied.The details are as follows:1.the RGO/ZnS nanocomposites were prepared by one-step hydrothermal method with the nucleated and adsorbed of Zn²⁺and S^2-on the surface of graphene.The microstructure of the experimental products was proved by X ray diffraction,scanning electron microscopy,high resolution transmission electron microscopy and Raman spectroscopy.The diameter of the ZnS nanoparticles on the graphene sheet was around 30nm,and the composite process was discussed.The tribological properties of RGO/ZnS nanomaterials were investigated with the medium of epoxy.The experimental results show that compared with pure epoxy resin and ZnS/epoxy coating,the RGO/ZnS coating has better friction-reducing and wear-resistant abilities.Besides,we explored the effect of a certain range load changes on the tribological properties of RGO/ZnS nanomaterials.The results showed that with the load increase,the wear rate of the coating increased correspondingly,and the friction coefficient first decreased and then increased.Finally,we have researched the friction-reducing and wear-resistant mechanisms of ZnS and RGO/ZnS nanocomposite.2.The RGO/MoS₂ nanocomposites were prepared by the hydrothermal method with the control of surface activity,and the morphology and structure of the samples were characterized by a variety of means.The friction and wear properties of MoS₂and RGO/MoS₂ nanocomposites in the vacuum environment were studied by adding it to the epoxy resin.The experimental results show that the structural damage of pure MoS₂ in vacuum can lead to the decrease of friction-reducing and wear-resistant abilities,which is not suitable for a long time work in vacuum.Compared with pure MoS₂,RGO/MoS₂ nanocomposites have lower friction coefficient and smaller wear amount,and the working time of friction-reducing and wear-resistant about RGO/MoS₂ is greatly improved than pure MoS₂.Finally,we discussed the mechanism of friction reduction and wear resistance of RGO/MoS₂ in vacuum.3.By decomposing Ce?NO₃?₃ in the hydrothermal environment and adding graphene oxide,the RGO/CeO₂ nanocomposites were prepared.The phase and morphology of the prepared samples were characterized by a variety of specific testing methods.The characterization results show that CeO₂ nanoparticles are evenly distributed on the surface of graphene nanoscale with the size of dozens of nanometers.The addition of RGO can effectively reduce the tendency of adsorption and aggregation between CeO₂ nanoparticles.At the same time,we added RGO/CeO₂nanocomposites to the epoxy resin for a series of tribological properties study.It is obtained from the experimental results that the RGO/CeO₂ nanocomposites have good lubrication ability?the friction coefficient is about 0.08?,and it has good friction-reducing and wear-resistant abilities.There are few reports on the tribology of rare earth metal oxides,but rare earth oxide as a very important resource,it is of great practical significance to explore many aspects of its properties.The study of the tribological properties of CeO₂ can widen the application field of rare earth oxide,and also give some reference value for the development of other new solid lubricating materials.