Preparation And Properties Of Three-dimensional Graphene Network Reinforced Copper Matrix Composites

Owing high thermal conductivity,high electrical conductivity and some other advantages,copper and copper based alloys have been widely applied for hundreds of years.However,their shortages of low strength and poor high temperature performance are unable to meet the requirements of current industrial production.Graphene is a novel type of reinforcement,which has been widely studied in the field of metal matrix composites.Usually,the reduced graphene oxide(rGO)was mostly investigated.Thus the graphene-reinforced copper-based composites always possess good mechanical properties,but poor thermal and electrical performances due to the massive structure-defects and oxygen-containing functionalities of rGO.The poor dispersibility of the graphene in the composite is another problem that needs to be solved.Copper foam is a novel type of foam-like network with porous three-dimensional structure.It is also a frequently-used substrate for acquiring high-quality graphene by chemical vapor deposition(CVD)method.In this paper,a new type of three-dimensional graphene network was well prepared using Copper foam substrate.In this way,we could solve the problem of poor–quality growth and poor dispersibility of graphene at the same time.In this paper,the CVD preparation process of graphene was well studied.The optimum parameters of the CVD process were as follows.deposition temperature 1000 ?;deposition time 12 min;deposition gas flow rate(hydrogen: argon)= 10 sccm: 90 sccm.The obtained three-dimensional graphene network was identified to be very thin with few defects and a perfect hexagonal graphite lattice structure with good crystallinity.A self-supporting three-dimensional graphene scaffold was well prepared using the optimum CVD process.In this way,we successfully fabricated a new type of three-dimensional free-standing graphene skeleton with intact porous skeleton.Spark plasma sintering(SPS)technique was adopted for preparing three-dimensional graphene-reinforced copper matrix composites.The obtained composites were firstly investigated using optical microscopy,and the agglomeration of graphene was not found.The surfaces of the composites were observed by scanning electron microscopy(SEM).Results showed that the three-dimensional graphene network remained during the sintering process.Additionally,the graphene skeleton refined the copper grains obviously.Compared with pure copper,the tensile yield strength of the obtained composite improves by 160 MPa,the tensile strength of the obtained composite increases by 48.6 MPa,the compression yield strength of the obtained composite improves by 193 MPa;the linear thermal expansion coefficient of the obtained composite reduces by 1.3×10-6 /oC.The international quenched copper standard(IACS)of the obtained composite is as high as 73.8%.Moreover,the thermal conductivity of the obtained composite increased by 2.2%,respectively.In addition,the elastic modulus and hardness of the obtained composite increases by 6.3% and 4.3% respectively.Furthermore,the evaporation treatment was carried out for studying its effect on the wetting of copper on the surface of graphene.Results showed that the wetting contact angle of Ag-Cu brazing alloy on the graphene surface decreased after the evaporation treatment.Moreover,the spreading surface of the brazing alloy is larger after the coating treatment.Results show that the evaporation treatment promoted the wetting of copper on the surface of graphene and improved the bonding between graphene and copper.The mechanical properties of the obtained composite prepared after the evaporation treatment was further improved.Furthermore,its conductivity reached 43.74 S/m and its IACS value reached 77.2%.Moreover,tts thermal conductivity reached 281.5 W/mk which was 4.6% higher than that of pure copper and 1.7% higher than that of the composite without evaporation treatment.The average coefficient of thermal expansion of the composite after evaporation treatment was 15.4 × 10-6/oC,which was 14.4% lower than that of pure copper and 7.7% lower than that of the composite without evaporation treatment.Additionally,the density of the composite material is lower than that of pure copper.