Preparation And Mechanical Properties Of Graphene/Copper Composite With Layered Structure

Owing to its advantages of high conductivity,high toughness and high thermal conductivity,copper has a wide range of applications in the fields of lithium-ion battery negative collector and electronic packaging lead frame,but its low strength limits its application in the above fields.Copper-based composite materials have excellent mechanical,which can replace copper in many fields.As an excellent reinforcement,graphene has been extensively studied in copper-based composites.The graphene of traditional graphene/copper composites was usually a randomly distributed structure.This structure usually leads to a decrease in the toughness and plasticity while increasing the strength of the composite material,and the increase in the amount of graphene inevitably leads to agglomeration,resulting in a decrease in strength and toughness.The appearance of a layered structure provides effective solution.In this paper,layered graphene/copper composites with comprehensive strength and toughness were prepared by layer-by-layer electrodeposition process.The morphology,structure characterization and stretching performance test of the layered graphene/copper composite material were carried out by scanning electron microscope(SEM),transmission electron microscope(TEM),X-ray photoelectron spectrometer(XPS)and micro-mechanical tensile testing machine.The effects of the electrodeposition time and the number of graphene layers on the mechanical properties of the composite were discussed.Combined with molecular dynamics simulation,the strengthening and toughening mechanism of the laminated composite and the effects of the interfacial bonding strength and graphene continuity on the mechanical properties of the composite were studied.The results show that the layered distribution of graphene in the copper matrix was realized by the layered electrodeposition process,and the content of ordered graphene was gradually increased without agglomeration by increasing the number of layers.With the increase of electrodeposition time,the distribution continuity and stacked degree of graphene gradually increase,and the strength of the composite material increases firstly and then decreases.Combined with the molecular dynamic simulation,the increase of the continuity of graphene distribution increases the dislocation density and stress in the copper matrix,and the deformation resistance of the copper matrix and the strength of the composites increase accordingly.However,the interfacial bonding strength between multilayer stacked graphene and copper matrix is weak,and obvious interfacial holes and interlamellar shear of graphene will be formed during the tensile process,which leads to the decrease of the strength of the composite.As the number of layers increased,the graphene content in the composites increased and the strength was improved while maintaining the same toughness as that of pure copper.Molecular dynamics simulations show that graphene restricts the dislocation movement between layers,which results in dislocation packing effect and improves the strength of the composite.At the same time,the presence of layered graphene improves the toughness of the composites through the "confining effect" on the crack tip.In addition,the effects of high interfacial bond strength and graphene continuity on the mechanical properties of the composites were investigated by molecular dynamics simulation.High interfacial bond strength improves the stress transfer efficiency,which is conducive to the improvement of the strength of graphene/copper composites and the passivation of crack tip.Continuous graphene provides ultra-high enhancement,but with reduced elongation,and can be used in applications where high strength materials are required.