Effect Of Graphene Powder On Microstructure And Properties Of Metal Matrix Graphene Composites

The metal-matrix graphene composite material,with excellent comprehensive performance and broad industrial application prospects,is still in the initial stage of research.In this paper,GNPs/Cu composites,GNPs/Al composites and GNPs/Mg composites were prepared by mechanical alloying and Field Actived and Pressure Assited Synthesis?FAPAS?.The microstructures of these three groups of metal-matrix graphene composites were characterized by optical microscopy?OM?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.Thermal conductivity,electrical conductivity,mechanical properties and corrosion resistance of three groups of metal-matrix graphene composites is tested by thermal conductivity detector,conductivity detector,Vickers hardness tester,microcomputer controlled electronic universal testing machine and electrochemical workstation.The influence mechanism of different graphene content on the microstructure and properties of metal-matrix graphene composites was investigated.The main conclusions are as follows:?1?Formation of Cu C₈by Cu and finite diffusion of Cu atoms on Cu?111?plane,which improves the interfacial bonding strength of GNPs/Cu composites.When the amount of graphene is added by 0.5wt.%,it can be effectively dispersed in the Cu matrix,and promote the movement of phonons and electrons at the grain boundary of Cu matrix.The thermal conductivity and conductivity of GNPs/Cu composites increase by 2.9%and 4.4%respectively.Due to the small particle size of graphene,the addition of graphene can effectively compensate the defects such as pores generated during the sintering process,improve the interfacial bonding strength between graphene and Cu matrix,and increase the strength and hardness of GNPs/Cu composites by 40%and 17.6%respectively.Graphene can change the electrochemical activation energy at the grain boundary of Cu matrix,forming a dense film layer to reduce the corrosion of the corrosion solution to the matrix material,and the corrosion resistance of GNPs/Cu composite material is improved by 28%.When the graphene content exceeds 0.5wt.%,graphene agglomeration occurs at the grain boundary of Cu matrix,which increases the defect concentration at the interface of GNPs/Cu composite and reduces the performance of GNPs/Cu composite.?2?By optimizing the sintering process,the formation of the compound Al₄C₃in the GNPs/Al composite is effectively inhibited,and the interfacial bonding strength between the graphene and the Al matrix is improved.When the amount of graphene is added by 0.5wt.%,it can be uniformly dispersed at the grain boundary of Al matrix.Since graphene has good interfacial wettability with Al matrix,it promotes the movement of phonons in the matrix material and reduces thermal resistance of the interface of materials,forming a conductive network on the surface of GNPs/Al composites,increasing the mobility and mean free path of electrons,and increasing the thermal conductivity and electrical conductivity of GNPs/Al composites by 7.1%and 4%respectively.Graphene can change the crystal structure of the Al matrix material,forming a lattice distortion stress field around the graphene.This stress field interacts with the dislocation stress field,hindering the dislocation motion,and increasing the strength and hardness of the GNPs/Al composite by 30.6%and 44%respectively.Graphene can also reduce the dielectric loss of the interface capacitance of the matrix material,form a dense and flat film layer on the surface of the Al matrix material,improve the charge transfer resistance of the GNPs/Al composite material,and reduce the dispersion effect of the material surface in the electrochemical corrosion process,which can increase the corrosion resistance of GNPs/Al composites by 31%.When the graphene content exceeds 0.5%wt.%,the graphene agglomerated at the grain boundary of the matrix reduces the interfacial bonding strength of the composite material,which results in a decline in the performance of GNPs/Al composites.?3?A high differential charge density and a strong hybrid and covalent interaction between the C atom and the Mg atom can reduce the preparation defects of the matrix material and improve the interfacial bonding strength of the GNPs/Mg composite,which can improve the dislocation density of the matrix material,increase the resistance of the grain boundary to dislocation movement during deformation,reduce the potential difference between the electrodes by etching the current,and enhance the electrochemical reaction resistance of the electrode surface of the GNPs/Mg composite material,consequently,passivate the surface of the composite.When the graphene content is 0.1%wt.%,the thermal conductivity and electrical conductivity of GNPs/Mg composites increase by 2.3%and 14.6%respectively,the hardness and strength by 10%and25%respectively,and the corrosion resistance by 89.1%.With the graphene content increasing,the defect concentration of the interface increases,and the interfacial bonding strength of the composite is lowered,resulting in a decrease in the performance of the GNPs/Mg composite.