First Principles Study On The Interface Modification And Mechanical Properties Of Graphene/Copper Composites

The weak interface bonding of graphene/copper(Gr/Cu)composites limits the strengthening effect of graphene,and the interface doping with transition metal elements(TM = Ti,Cr,Ni,Co)has been experimentally proved to be an effective pathway to solve this problem.However,due to the limitations of experimental characterization methods,it is difficult to further study the microscopic modification mechanism.In this paper,the microscopic influencing mechanism of TM doping on the interface interaction and mechanical properties of Gr/Cu was investigated,and a quantitative relationship between interface bonding and mechanical properties was established by the first-principles calculations,which could be served as a favorable support for the experimental design of graphene/copper composites.The sandwich model with graphene embedded in Cu matrix was adopted here to simulate the TM-doped interfaces,and the advantages of sandwich model over simple model were verified by electronic structure analysis.It is revealed that the introduction of TM doping elements can significantly improve the work of separation,following the order of Ti-doped > Cr-doped > Ni-doped ≈ Co-doped > clean,which relates to the electronegativity difference between TM and Cu elements based on the analysis of the interface electronic structure.The mechanical properties of the clean and TM-doped interfaces were studied by the rigid stretching and the relaxed stretching.Within the rigid scheme,the theoretical tensile strengths of different interfaces are positively correlated with the work of separation,following the order of Ti-doped > Cr-doped > Ni-doped ≈ Co-doped > clean.While in the relaxed stretching,the release of internal stress during the relaxation reduces the theoretical tensile strength of various interfaces compared with that in the rigid tensile strength,especially for the Cr-doped interface.Then,the tensile fracture mechanism was analyzed based on the variation of charge density and interfacial spacing at different strains,and it was found that the electronegativity is also a main factor affecting the mechanical properties.Furthermore,a fitting function containing the element electronegativity was applied to determine the quantitative relationship between the interface bonding and mechanical properties,which quantitatively explained the important effect of electronegativity on the interface bonding and mechanical properties of Gr/Cu composites.Then,this quantitative relationship was extended to rare earth elements doped systems(Sc,Y,La),and it is verified that this quantitative relationship is widely applicable in Gr/Cu system.