Fabrication Of Cu@gr@ Ceramic Multilayer Core-shell Structure And Strengthened Copper Matrix Composites

As a two-dimensional layered material,graphene has excellent physical and mechanical properties,and has broad application prospects in composite materials as a reinforcing phase.At present,there are many domestic and foreign researches on graphene as a reinforcing phase-reinforced copper-based composite material.However,graphene has a large surface area and is prone to agglomeration in metal materials,result in full play to the advantages of graphene.The core-shell structure currently developed is widely used in the fields of catalysis,photonic crystals,medical treatment,electrochemical energy storage,etc.due to its special coating structure and the performance characteristics of both the core and the outer shell.It has become a research hotspot in recent years.As a reinforcing phase used to strengthen copper-based composite materials.But,there are few research reports about graphene-containing core-shell structure reinforced copper matrix composites.Based on this,this article uses chemical vapor deposition and thermal electroless plating to prepare multilayer core-shell particles,and coats the middle layer of the core-shell structure with graphene.The Cu@Gr@ceramic reinforced copper-based composite material was prepared by powder metallurgy.The micro structure and mechanical properties of Cu@Gr@SiO₂ and Cu@Gr@Al₂O₃ reinforced copper-based composite materials were observed and analyzed,respectively.Exploring the influence of different Cu@Gr@ceramic content on the mechanical properties of copper matrix,the main conclusions are as follows:(1)Using spherical alumina and silica with an average particle size of 1?5 ?m as the core of the core-shell structure,the graphene-coated silica and alumina(Gr@ceramics)were successfully prepared by chemical vapor deposition.Double-layer core-shell structure.The graphene is evenly coated on the surface of the ceramic particles,and there is no phenomenon of graphene wrinkles.Then,the multi-layer core-shell structure of copper-coated Gr@ceramic was successfully prepared by the method of thermal electroless plating.The dense copper shell completely covers the double-layer core-shell structure,and the surface roughness of the particles is significantly increased.There are no gaps between the multi-layer core-shell structure interface,which is a dense spherical shape.The number of graphene layers is 8 to 15 layers,and the thickness of the copper shell layer is about 0.1 ?m to 0.3 ?m.(2)After mixing Cu@Gr@ceramic particles and copper powder,powder metallurgy is used to press into a billet at a pressure of 300 MPa,and then sintered at 850? to prepare a core-multilayer core-shell structure-reinforced copper-based composite material.When the content of core-shell structure is 5wt%,the agglomeration of core-shell particles appears in local area.With the increase of the content of core-shell particles,the properties of copper matrix composites first increase and then decrease.(3)When the content of Cu@Gr@SiO₂ is 2%,the dispersion of the reinforcing particles in the copper matrix is ideal,the density of the composite material reaches 94.65%,the conductivity is 83.1%IACS,the hardness is 56.8 HV,and the compressive strength is 395 MPa,the tensile strength is 140.11 MPa.When the content of Cu@Gr@Al₂O₃ is 1%,the dispersion of the reinforcing particles in the copper matrix is ideal,the density of the composite material reaches 91.79%,the conductivity is 73.7%IACS,the hardness is 47.5 HV,and the compressive strength is 398 MPa.(4)The reinforcement mechanism of core-shell particle reinforced copper matrix composites is dislocation strengthening.SiO₂ and Al₂O₃ are high melting point hard phases.The difference in thermal expansion coefficient with graphene and metallic copper matrix causes dislocations to increase,thereby improving the mechanics of the material.The fracture mechanism is ductile fracture.The existence of the core-shell structure provides the nucleation source of micropores,which will break away from the matrix under stress to form micropores.