| Copper and its alloys have good electrical conductivity,thermal conductivity and corrosion resistance,so they are widely used in aerospace,automotive,mechanical and electrical fields.However,their loading capacity and wear resistance is poor.With the development of science and technology and industrial production,it is urgent to improve the wear resistance of copper and its alloy.At present,graphene(GNS)as a new self-lubricating component,has been widely studied.It has excellent electrical conductivity,thermal conductivity and mechanical properties,so it is ideal strengthening phase for improving friction reduction,wear resistance and mechanical properties of copper matrix composites.However,graphene is very easy to agglomerate and is not wetted with copper matrix,so it is difficult to disperse uniformly in copper matrix.In this paper,graphene is coated with nickel to enhance the binding force between graphene and copper and make it dispersed in copper matrix uniformly.The effects of different nickel/graphene(Ni@GNS)contents on the tribological properties of copper matrix composites were studied.;The surface polishing of nickel/graphene-copper matrix composites(Ni@GNS/Cu)was prepared by electropolishing technology.It was found that the tribological properties of copper matrix composites modified by self-supporting graphene nanosheets were further improved and their application fields were expanded;A novel three-dimensional graphene nano-film with excellent tribological properties was prepared on metal surface by one-step hydrothermal method.Tribological properties of three-dimensional interconnected graphene were studied.The main contents of this paper are as follows:(1)Ni@GNS/Cu self-lubricating composites were prepared by vacuum hot-pressing sintering with Ni@GNS as reinforcing phase which surface of GNS is coated with nickel nanoparticles.The tribological properties of the composites under different loads and Ni@GNS content were studied.It was found that the friction coefficient was the lowest and the wear resistance was the best when the content of Ni@GNS reached 2 wt.%.Ni@GNS/Cu composites have better friction and wear resistance than graphene/copper composites(GNS/Cu).This is mainly because Ni@GNS/Cu composites can form stable carbon-rich lubrication film at the friction interface,and the introduction of nickel improves the bonding force between GNS and copper matrix and the hardness of the composites.(2)A special self-supporting graphene nanosheet structure was prepared on the surface of Ni@GNS/Cu composite by electrochemical polishing.One part of the graphene nanosheet was exposed to the surface of copper matrix,while the other part was firmly embedded in the matrix.Self-supporting graphene nanosheets with good continuity and coverage can be obtained by optimizing the electrochemical dissolution time.This process is simple and convenient.In the case of less graphene content in Ni@GNS/Cu composite(Ni@GNS=1 wt.),electrochemical polishing process can achieve a better lubrication state,which has better wear resistance and longer service life than that of the original composite prepared by hot pressing sintering.(3)GNS has great potential as solid lubricants,but they usually have short service life and low load capacity,which limits their application in engineering.Three-dimensional graphene nanosheet(3D-GNSF)coatings were prepared on copper substrate by one-step hydrothermal method.It is a three-dimensional interconnected structure formed by two-dimensional graphene nanosheets.The morphology,composition and structure of 3D-GNSF were analyzed and studied by X-ray photoelectron spectroscopy,X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The results show that the unique structure of 3D-GNSF can quickly generate a compact and stable sliding interface between the matrix and the friction pair,which makes 3D-GNSF a solid lubricant with low friction,good durability and high loading capacity. |
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