Preparation And Sliding Wear Properties Of Shale-core Alumina @Graphene Composite Nanoparticles Reinforced Copper Matrix Composites

Copper based self-lubricating materials are widely used in electronics,machinery,aerospace and other fields because of their excelent lubrication performance and wear resistance.With the development of science and technology,higher requirements are put forward for its tribological properties of copper-based composite materials.Copper based self-lubricating material is composed of lubrication component,wear-resisting component and copper base.The two-dimensional lubrication component is layered structure,and the friction film can be formed in the process of friction and wear,thus forming the friction layer with low shear strength,which has the effect of reducing friction.The wear-resistant components have high hardness and specific strength and play a wear-resistant role in the process of friction and wear.At the same time,shell-core structure materials have potential application value in the future production of self-lubricating materials due to their special structure and component adjustable advantages.Therefore,this paper proposes a strategy of assembling graphene lubrication components and alumina as wear-resistant components into a shell core structure（labeled as Al₂O₃@GO）,which is then introduced into the copper matrix to prepare copper-based self-lubricating materials（labeled as Cu-Al₂O₃@RGO）.The main research contents of this thesis are as follows:1.Preparation and characterization analysis of alumina@graphene@copper composite powder:The surface of alumina nanoparticles was modified by 3-aminopropyl triethoxy silane（APTES）,and then the GO and the modified alumina nanoparticles were assembled into Al₂O₃@GO shell core structure by stirring.Finally,the alumina@graphene@copper oxide composite powder was synthesized by the reaction of Al₂O₃@GO shell core structure with copper acetate by molecular mixing method.The composite powder was passed into Ar/H₂ gas mixture and reacted at 450℃for 3 hours.After reduction,the alumina@graphene@copper composite powder was obtained（labeled as Al₂O₃@RGO@Cu）.The modified alumina,Al₂O₃@GO shell core structure,Al₂O₃@GO@Cu O and Al₂O₃@RGO@Cu were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）and energy dispersive spectroscopy（EDS）,Fourier transform infrared spectroscopy（FTIR）and Raman spectroscopy Characterize and analyze.The experimental results show that the surface modification effect of alumina nanoparticles modified by APTES at 60℃and 90%anhydrous ethanol for 6 h is the best,without destroying the structure and reducing the self-agglomeration size of nanoparticles,and the modification process is the best.The modified nano alumina and GO were assembled into shell core structure by chemical bond,and the dispersion stability was improved.2.Copper-based self-lubricating materials were prepared by cold pressing and hot pressing sintering of Al₂O₃@RGO@Cu composite powder（labeled as Cu-Al₂O₃@RGO）.Hot pressing sintering process:sintering temperature of 900℃,holding time of 1 h and 2.0t pressure under solid phase sintering.The copper matrix composites（labeled as Cu-（Al₂O₃+RGO））with alumina and graphene distributed independently on the copper matrix were prepared by the same method.The tribological tests of two kinds of copper matrix composites were carried out in the loading range of 10-40 N and the velocity range of 200-600 rmp.The wear morphology of the two kinds of composites was observed and analyzed by SEM and laser confocal（3D measurement）microscope,and the friction and wear mechanism was proposed.The experimental results show that the shell core structure of aluminum oxide and graphene can improve the density and hardness of copper matrix composites and facilitate the formation of a continuous protective friction layer on the wear surface under high load and high speed conditions.Therefore,Cu-Al₂O₃@RGO has lower friction coefficient and wear rate than Cu-（Al₂O₃+RGO）composites in the range of 10-40 N load and 200-600 rmp dry friction.It is proved that Al₂O₃@RGO shell core structure is introduced into the copper matrix to prepare the composite material with excelent wear and friction reduction properties.The copper-based self-lubricating material prepared by this method has a potential application prospect in prolonging the service life of the workpiece and working under high load and high speed harsh environment.