First Principles Study On The Bonding Strength And Electrical Properties Of Cu,Ni Coated Graphene

Graphene is a kind of honeycomb hexagonal periodic structure composed of single-layer carbon atoms,which makes it have excellent electrical and thermal properties.At the same time,the tensile strength and Young’s modulus of graphene are very high,leading to potential applications in many fields,such as sensors,composites,solar cells,transistors and so on.During the process of studying graphene,the agglomeration problem caused by the surface properties greatly limits the excellent properties of graphene.In this project,metals are coated on the surface of graphene to prevent graphene from agglomeration.We hope to obtain the composite powders with excellent properties of both metal and graphene.At the same time,we use the first principles simulation method to study the related properties.Based on the improved Hummer method,graphene oxide was prepared by in-situ co-reduction method.We studied the change of the phase structure and morphology and the influence on mechanical and electrical properties of graphene after coating the metal.At the same time,according to the experimental results,we established the corresponding model and calculated the electronic structure,Young’s modulus,electron mobility,binding energy,charge transferring and bonding between metal and graphene.The results show that:1.Based on graphene oxide prepared by Hummers method and ascorbic acid as reducing agent,we prepared graphene,copper-coated graphene and nickel-coated graphene composite powders.Graphene is a kind of single-layer tulle-like powder.The copper-coated graphene comp osite powder appeared copper particles in the surface of graphene and the particles size ranged from 10nm to 60 nm.The particles size of Ni coated on graphene ranged from tens to hundreds of nanometers,and it had agglomeration phenomenon.2.We tested the mechanical and electrical properties of three kinds of powders,and the young’s moduli of graphene,copper-coated graphene and nickel-coated graphene were(1.06±0.02)TPa,(1.03±03)TPa and(0.98±0.02)TPa,and the conductivities were 250 s/cm,0.0398 s/cm and 0.0008 s/cm.3.The interface models of graphene,Cu(111)/graphene and Ni(111)/graphene were established by Materials Studio software.The results showed that graphene was a zero band gap structure,and it was mainly contributed by 2p electrons of C atom.The interface model did not change the zero band gap structure of graphene,but changed the main contribution electron from 2p electron of C atom to 3d electron of metal atom.4.The binding energy between copper and graphene is about 1.5 eV,and that between nickel and graphene is about 4 eV;.At the same time,we calculated the mechanical and electrical properties of three models.The results showed that the Young’s moduli were almost the same,the electron mobilities and conductivities were decrease greatly compared with graphene,which were consistent with the experimental results.5.The results of charge density difference diagram and population analysis showed that there was no new bonding mode between metal and graphene,but charge transferred between carbon atoms and metal atoms,and the cooperation of C-C bonding and metal covalent bonding are both enhanced.