Characteristics Of Defects Of Graphene Heterostructures And Its Interfacial Properties Of Multiple Composite Structure

The heterostructure can be formed by the combination of graphene and one or more of two-dimensional materials.Heterostructures can not only overcome the inherent limitations of each material,but also achieve new properties through their proper combination.However,by van der Waals force stacking,covalent bond splicing and domain-like heterostructures,defects are prone to occur.The existence of these externally introduced defects and intrinsic defects affect the mechanical,thermal and electrical properties of graphene and its heterostructures.Therefore,how to recognize the characteristics of these defects and how to use and control them is very important.Graphene has a special two-dimensional planar honeycomb structure and excellent performance,and is regarded as an ideal reinforcement for metal matrix composites.In particular,the structural diversity and interconvertible characteristics of graphene provide a rich way for the configuration design of metal-based nanomaterials.In this paper,through the combination of theoretical analysis and computer simulation,the graphene/boron nitride heterostructure and its defect mechanical and thermal properties are studied.On this basis,through experiments and molecular dynamics simulation,the design ideas of"internal configuration"and"external multi configuration"of nano materials are proposed,which can be used as an effective means to control the interface structure,load transfer and mechanical properties of metal materials.It is helpful for us to understand the physical mechanism of low-dimensional structure and property correlation,realize multiple structural forms,and even explore new uses.According to the writing order of this article,the research content can be organized into the following five aspects:Multi-physics coupling effect of defect in graphene/hexagonal boron nitride planar heterojunction:"study on non-steady-state structures"induced by local stresses caused by defects.The effects of size and geometry on the mechanical properties of graphene/hexagonal boron nitride planar heterojunction are discussed.The effect of external field(heat flow direction,strain field and temperature field)and internal field(defect number,defect geometry and interface connection method)coupling on the heat transfer of graphene/hexagonal boron nitride planar heterojunction was studied.The results show phonon transmission is less affected by compression deformation under the action of force-heat-defect coupling,while phonon transmission of heterostructure is more affected under tensile deformation,its surface fold disappears basically,and the bond length and bond angle of defective graphene/h-BN planar heterostructure will change.The non-harmonic interaction of the atoms in the composite system is strengthened,causing the softening of high-frequency phonons.As a result,the reduction of thermal transport at the interface of heterostructures will be.The"quasi three dimensional defect effect"of graphene/boron nitride vertical-stacked structure is due to the effect of the built-in distorted stress field induced by sp~3 interlayer bond and intrinsic defect.From the point of view of interface binding energy,the influence of interface connection mode on the stable shape of vertical-stacked structure is analyzed.The effects of defects,sp~3 bond and interface connection on the mechanical and thermal properties of vertical-stacked structures are studied.The results show that when sp~3 bond is introduced,the van der Waals structure gradually changes to"quasi three dimensional"structure.The effect of interlayer sp~3 bond is similar to defect.sp~3 bond makes the peak height of phonon state density of the original structure decrease and move to low frequency.When interlayer sp~3 bond and defect couple,it is easy to cause the phenomenon of stress concentration,which results in the change of bond length and bond angle,and makes the thermal transmission capacity and mechanical properties of graphene/hexagonal boron nitride vertical-stacked structure decrease.An ion irradiation model was established to control the properties of graphene and graphene/boron nitride heterojunction from the atomic scale.The"internal configuration design"was proposed to study the mechanical properties,defect evolution and enhancement mechanism of graphene boron nitride/copper(enhanced layered structure)under the coupling of stress field,temperature field and defect field(induced by ion irradiation).The results show that after irradiation damage,there are a lot of vacancy defects,which will produce more incomplete bonds.When the defect(caused by ion irradiation)and sp~3 bond coexist,the atom is easier to overcome the binding energy and lose stability from the inherent equilibrium position.The"external multiple configuration design"was proposed to construct graphene boron nitride/copper coated layered structure,and the influence and regulation of defects on the mechanical properties of the coated layered structure were studied.In order to give full play to the synergistic effect and achieve the complementation of performance and structural advantages,it provides theoretical basis and reference.BN-Gr-BN planar heterojunction and single crystal copper have a good synergistic effect.Through the interface interaction,the tensile load was successfully transferred from the copper-based interface to the BN-Gr-BN planar heterostructure.The BN-Gr-BN planar heterojunction is the main stress-bearing carrier,which largely shares the tensile stress of the whole system and reduces the phenomenon of local stress concentration.On the basis of diversified configuration design and control,the spark plasma sintering(SPS)and in-situ chemical vapor deposition(CVD)are applied to prepare the graphene/copper composites(Cu/Gr).The effect of Gr-Cu powder on microstructure and mechanical properties of composites is fully discussed.The strengthening effect of different nano-materials on copper(Cu)matrix was studied to profound investigate the strengthening mechanism of graphene(Gr).The failure mode of Cu/Gr system is different from that pull-out mode(single-wall tubes/copper)and inner-wall invalid mode(multi-wall tubes/copper).Load transfer,GND,grain refinement and Orowan strengthening together construct the strengthening mechanism of Gr reinforce agent.The difference of the strengthening efficiency between the configurations of carbon nanoparticles can be explained by the configuration dislocation strengthening and the configuration loading transfer.