Preparation And Properties Of Graphene/Copper Composites

Graphene, a novel two-dimensional atomic crystal composed of sp2-bondedcarbon atoms, is found to the strongest material ever measured. Despite a large amountof progress has been made for the past few years, it’s demonstrated that the mostimmediate application for graphene is probably its use in composite materials.Graphene-based materials ever reported were mainly focused on graphene/polymercomposites: the strength and other properties of the polymer matrix were remarkablyincreased as the enforcing filler of graphene. However, the strengthening effect ofgraphene in metal matrix was rarely covered. Here, four methods for preparinggraphene/copper composites are designed to study whether graphene could be able tostrengthen metal matrix or not and the performance of composites by reference tosynthesis routes of carbon-based composites reported in recent years.In this thesis, these four preparation methods above are named as Ball-Millingmethod, MMLM method, HHR method and MP method, respectively. Atomic forcemicroscopy, zeta-potential analyzer, Raman spectroscopy, X-ray diffraction, X-rayphotoelectron spectrum, Auger electron spectroscopy, optical microscope, scanningelectron microscope, transmission electron microscope, material testing machine,resistivity testing machine together with potentiostat are used to study the surfacemorphology, phase structure, mechanical properties, conductivity performances andelectrochemical behaviors of the starting graphene oxide and graphene/coppercomposites fabricated by these four different methods.Results show the graphene oxide sheets used in our experiments are flat withthickness of²nm, which are in two-dimensional graphene category. Graphenehomogenously dispersed in the matrix displays a remarkable strength enhancing ability,which is superior to any other reinforcements widely used at present. At only2.3volume fraction of graphene filler, the highest compressive yield strength ofgraphene/copper composite could be501MPa, about3.34times higher than the coppermatrix.Among these four synthesis routes, Ball-Milling method caused graveagglomeration and coalescent of graphene oxide sheets. The graphene/coppercomposites fabricated via this method show poor mechanical properties, withcompressive yield strengths of70.22MPa and334.44MPa. MMLM method is superior in fabricating composites with lower volume fraction of graphene. The compressiveyield strength of composites with only0.6vol%graphene addition prepared by thismethod is410.89MPa. However, with an increased volume fraction of graphene oxide,it’s more difficult to distribute them homogenously in matrix with a trend of worseningstrengthening efficiency, which even decreases the strengths of composites. Thegraphene/copper composites prepared by HHR method show poor performances with acompressive yield strength of191.20MPa. MP method could distribute graphene oxidesheets more homogenously in the matrix comparing with the three preparation methodsabove. The graphene/copper composites processed by MP method show the bestmechanical properties, with compressive yield strengths of439.47MPa,462.07MPa,501.26MPa and394.58MPa, respectively.The resistivities of composites prepared by these four methods above are in therange of2.96to5.43×10^-8/m, being somewhat higher than that of pure copper. Thecorrosion potentials of these composites are in the range of-206to-293mV, indicatingthat not only does graphene not reduce the matrix’s resistance to corrosion, butimprove the corrosion resistance of composites.