Interface Structure Characteristics And Deformation Behavior Of Graphene/Cu Composites

Graphene/metal are endowed with lightweight,good strength and toughness,fine thermal and electrical conductivity,high wear resistance and so on because graphene has excellent tensile properties,good thermal and electrical conductivity,large specific surface area,light weight,etc.That is to say,graphene as a functional monomer gives some excellent physical and chemical properties to graphene/metal composites,which make graphene/metal composites have various functional characteristics and broad application prospects in aerospace,mechanical equipment,electronics,electric power and other fields.However,tensile properties of graphene/metal composites are unsatisfactory.Graphene/metal composites have poor stability and low damage tolerance,especially in complex and serious service environment.Tensile properties of composites are closely related to concentration,dispersibility or size distribution of graphene and interfacial interaction between graphene and metal matrix.The current research progresses indicate that agglomeration of graphene and poor interfacial bonding ability are the main factors restricting the development of graphene/metal composites.Graphene owns complicated interface structures and unique interaction mechanism between dislocation and interface during deformation process in comparison with traditional ceramic reinforcement phases due to unique two-dimensional lamellar structure.So it is crucial to make a profound study of interface structure between graphene and metal matrix in order to obtain graphene/metal composites with outstanding tensile properties.It is difficult to understand interaction mechanism between graphene and metal,especially the micro-action mechanism for interfacial region during stretching in graphene/metal by via of present characterization methods due to low addition（a small amount can work）and small size of graphene.Performance evolution law and failure mechanism of composites under different service conditions can be carried out at multi-level through first-principles from the perspective of nano,micro,meso and macro in order to improve performance and optimum design of interfacial structures.In this paper,interfacial structure and its change law during stretching have been discussed using first-principles calculations.Interfacial models of graphene/metal composites are constructed in this article.In addition,interfacial characteristics and effects of heteroatoms Ni,Ti,Mn,Al or Si as well as defect state of graphene on interfacial bonding capability as well as deformation mechanism of graphene/metal composites are all studied at the atomic level.The main research results are as follows:（1）Graphene/Cu models are established to study the influence of stretching directions on the interfacial bonding properties.High strength of graphene can be fully exerted stretching parallel to graphene.But different deformation ability between graphene and Cu leads to their deformation inconsistency.Perpendicular to graphene,poor interfacial bonding ability results in cracks growth rapidly at the interface.Therefore,it is necessary to enhance the interfacial bonding ability in improving composites’tensile properties.（2）Interface bonding ability of graphene/Cu are calculated by studying types of heteroatoms（Ni,Ti,Mn,Al and Si）and their substitution states.It is found that both Ti and Mn-doped Cu matrix significantly improve the interfacial bonding ability and tensile properties of graphene/Cu.In A₁A₂A’₁A’₂type（some Cu atoms at the interface are replaced by heteroatoms）,Ti/Mn/Ni and C atoms in graphene form large numbers of stable chemical bonds or carbides with high strength.In particular,strength of new chemical bonds or carbide formed by Mn and C is higher than that force between Cu layers.Therefore,tensile strength and elongation of graphene/Cu increased by 377%and 364%via Mn-doped and fracture occurs in Cu matrix stretching perpendicular to graphene.On the contrary,Al and Si tend to weaken the interfacial bonding ability.（3）Single vacancy defect are introduced into graphene to study tensile properties of graphene/Cu composites using simulation calculation.The results show that single vacancy defect in graphene can enhance the interfacial bonding ability between Cu matrix and graphene,especially the adsorption and binding ability between Cu atoms perpendicular to single vacancy defect and graphene.（4）Combined with previous experimental results,electrodeposition process of graphene/Cu and the effect of graphene on the electrocrystallization behavior of composites are analyzed.It is found that graphene as the second phase can promote adsorption and deposition of Cu²⁺in electroplating solution,reducing the nucleation barrier,promoting nucleation rate and refine grains around graphene resulting in interfacial microstructure and structure characteristics changed.Meanwhile,materials properties are affected as well.The above results reveal that the influence of types of heteroatoms and their doping states,defect state of graphene and external electric field on microstructure,interface properties and deformation behavior of graphene/metal,which is helpful to understand the deformation mechanism of graphene/metal composites.From the experimental point of view,it provides a theoretical basis in improving the interface structure and mechanical properties of graphene/metal composites.