Preparation And Characterization Of The Copper-Graphene Composite Film By Electrodeposition Process

Graphene,two-dimensional structure consisting of carbon atoms,was found by English scientists in 2004.Its discovery makes up for the blank of carbon system in the two-dimensional structure,It becomes a hot topic research and attracts a great of attention.Graphene is a single layer hexagonally arranged carbon atoms.It possesses high thermal conductivity,electrical conductivity and outstanding mechanical properties.In the composite materials field,seeking materials with excellent property is an eternal theme.The appearance of graphene attracts a lot of interest.The researchers are trying to embed graphene into the composites as a reinforcing materials.In recent years,the copper matrix composite materials has been developed very quickly due to its excellent properties.So,the study of copper-graphene composite is of profound significance.In the reported literatures,as main methods of preparing copper-graphene composite,graphene oxide was generally used as the precursor of reinforcement to electrodeposit composite films,followed by the reduction of graphene oxide to graphene.The results showed that the mechanical strength of composites was improved obviously,but the thermal conductivity and electrical conductivity decreased.This was attributed to the defect of graphene oxide resulting from its inadequate reduction.Therefore,copper-graphene composites with good properties need to be developed.In this paper,the graphene-Cu composite film was prepared by electrodeposition from copper sulfate system and citrate acid system,respectively.It avoided the heat treatment in the following process.Firstly,graphene prepared by CVD was chosen as the precursor of composite materials.The optimal concentration of the surfactants was determined through dispersing test.Then,the electrodeposition process of graphene-Cu composite was carried out systematically.Electrodeposition parameters of graphene-Cu composite were optimized,including concentration of graphene,power supply and stirring way.Next,Raman spectrum was used to determine the existence of graphene in the prepared copper-graphene composites.The microstructure and morphology of copper-graphene composites were characterized by SEM and TEM technology.Finally,the samples for testing electrical conductivity,thermal conductivity and mechanical properties were prepared by micromachining process.The experimental results showed that,for copper sulfate system,the electrodeposition assisted by pulse supply and ultrasonic stirring could obtain compact composites when the graphene concentration in the electrolyte was high.The thermal conductivity of the copper-graphene composite was 515.5W/mK,which was higher than that of metallurgical copper?398W/mK?.The electrical resistivity of copper-graphene composite was 1.66×10^-8?m,which was lower than that of electrolytic copper(1.75×10^-8?m).And the mechanical property of composites had also been improved at the cost of the decreased elongation.The Young modules,yield strength and breaking strength was 81.0GPa,237.8MPa and382.4MPa,respectively.For citrate acid system,it was found that pulse supply?J=2mA/cm²,ton/toff=0.1ms/0.9ms?was beneficial to prepare homogeneous composite.In this case,the electrical resistivity of copper-graphene composite was 6.54×10^-8?m,which decreased one order of magnitude compared to that of electrolytic copper(8.46×10^-7?m)prepared in the same condition.This indicated that graphene could effectively reduce the resistivity of electodeposited Cu.As a whole,the performances of electodeposited pure Cu were improved including thermal conductivity,electrical conductivity and mechanical strength by embedding graphene into copper matrix.