Preparation And Properties Of Graphene/Silver Matrix Composites

In the field of Aeronautics and Astronautics, electrical contact materials with highelectrical conductivity, thermal conductivity, wear resistance and strength are oftenadopted for the power or dynamic signal transmission. With the advance of applicationrequirements, the strength and wear-resistance of the electrical contact materials need tobe further developed without reduction of the electrical conductivity. Graphene hasgood excellent thermal, electrical and mechanical performance. In this paper, wedescribe the graphene/silver based electric contact materials with self-lubricatingproperties.Graphene was synthesized via redox process in order to obtain graphene reinforcedsilver-based electrical contact materials. Meanwhile, silver nanoparticles were loadedonto the surfaces of graphene by using reduction method. Then the graphene/silvernanoparticles composite powder was prepared and the effect of process parameters onthe silver particle size distribution was studied. At last, graphene/silver based electriccontact materials were prepared with powder metallurgy method. And thecomprehensive performance of graphene reinforced silver matrix composite wasinvestigated. The morphology, microstructure and component element of graphene andgraphene/silver nanoparticles composite powder were characterized by X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy(TEM) and Raman spectroscopy. Compared with the traditional graphite/silver matrixcomposites, the metallographical structure of graphene/silver matrix composites wasobserved. The electrical conductivity, hardness and bending performance were alsoexamined. The following conclusions could be drawn:(1) Graphene powder is successfully prepared by redox process. The as-preparedgraphene is about3～4single layer.(2) Results show that the morphology of graphene/silver nanoparticles compositepowder could be significantly influenced by the Ag+concentration. When Ag+concentration is low (CAg+≤1.176×10-2mol/l), well-dispersed Ag nanoparticles withthe size of25～50nm are deposited onto graphene nanosheets. With the enhancementof the silver ion concentration, silver particle size becomes larger, and parts of theparticles begin to reunite. The excessive reductive agent can also cause thisphenomenon. In addition, citric acid did not show the dispersion effect. Comprehensive analysis shows that when0.1g graphene oxide was added into50ml deionized water(the concentration of silver ion is1.176×10-2mol/l), Ag particle could be uniformlydistributed onto the surface of graphene with10ml hydrazine hydrate.(3) Graphite/silver matrix composite and graphene/silver matrix composites wereprepared by powder metallurgy method. Graphene/silver matrix composites show betterelectrical and mechanical performance. The hardness could be increased by145.9%,while wearing capacity is reduced by about85.9%with the fact that the conductivityremains unchanged.The innovations of this research are as follows:(1)3to4layers of graphene with sheet piling and winding structure was successfullysynthesized by simple and easy experiment process.(2) Graphene/silver nanoparticles were prepared by reduction method, whichovercomes the reunion effect of graphene layers and provides excellent raw materialsfor graphene/silver matrix composites.(3) Graphene/silver matrix composites were obtained with more excellentperformance than carbon/silver matrix composites.