Wetting Of Various Carbon Materials By Cu-xCe Alloys And Graphite By Cu-xSn-yCr Alloys

Copper/carbon composite is one kind of materials of copper as a matrix with carbonaceous materials as reinforcements(such as diamond,graphite,carbon fiber,carbon nanotubes,graphene,etc.).The introduction of carbonaceous materials into the matrix can significantly improve the strength,high temperature resistance,wear resistance and corrosion resistance of copper/carbon composites.These composites have the extensive application in the fields of aerospace,rail transit,and electronics industry.Since the copper/carbon composites have been manufactured,the interface between the copper matrix and carbonaceous materials arose attention by many scholars.There is eager for obtaining good compatibility of copper to carbonaceous materials in industry field.However,even at the large extent over-heated temperature,liquid Cu cannot react with graphite,and their interface is difficult to satisfy the requirements of industrial production.Therefore,it is necessary to study the wetting mechanism between copper-based alloys and carbonaceous materials,and further understand their interface structural characteristics,try to improve the wettability of copper-based alloys on carbonaceous materials,so as to optimize the production of copper/carbon composites.The research results may provide some important information for the development of high-performance copper/carbon composites.In this work,the modified sessile drop method was employed to study wettability,SEM,EDS,XRD,OM and other detection and analysis methods,combined with the theoretical analysis of interfacial thermodynamics and spreading kinetic models are used to probe the Cu-xSn-yCr alloys on the graphite surface.The wettability and spreading dynamics of Cu-x Ce alloys on the different carbon materials surface.The microstructural characteristics of the interface,spreading mechanism and spreading dynamics were analyzed,and the main results are as following:(1)The perfect wetting of Ce on the graphite plate is achieved due to the penetration of Ce into the pores.In addition,the dissolution of graphite in Ce reduces the surface tension of the liquid,and then penetrates until it is completely consumed by Ce to form Ce-containing carbides.There is no continuous reaction layer on the Ce/CVD-diamond interface,and the decomposition reaction of WC is the main reason for the lower final contact angle(24°).In the Ce/Bucky Paper(NWCNTs)system,the high crystalline stability of the NWCNTs tube wall led to a relatively large contact angle.In Ce/graphite paper and Cu-Ce/graphite plate,Ce reacted with carbon at the interface.The special structure of graphite paper makes Ce react with graphite completely,and the droplets are transformed into solids in the final stage.Addition of more than 20 at.%Ce to Cu alloy can improve the wettability,significantly.The reduction of surface tension caused by the reaction products at the interface and Ce in the Cu-Ce alloy led to the improvement of the final wettability.(2)In the Cu-xSn-yCr/graphite system,a small amount of Cr(0.5?2 at.%)participates in the interfacial reaction and precipitates wettable Cr-C compounds to promote wettability,effectively.Among them,Sn as a surface active element reducing the surface tension of molten ternary alloys effectively.With the increasing of Sn concentration(from 10 at.%to 80 at.%),the main precipitation phase at the interface will undergo a transition from Cr₇C₃to Cr₃C₂,resulting in a slight deterioration of wettability.There exists a critical transition concentration for the main precipitation phase at interface caued by the Sn concentration,is about 35 at.%.All the spreading processes in the Cu-xSn-yCr/graphite systems can be described by a diffusion-controlled spreading dynamic model.When the Sn concentration is lower than the critical concentration(35 at.%),Cr is transferred from the melt to the vicinity of the triple line through the Sn segregation layer on the surface of the droplet,further enhanced the material transport to form a precursor film near the triple junction.Conversely,when the Sn concentration is higher than the critical concentration(35at.%),the Cr transport channel through the droplet surface was disappeared,and thus no precursor film can be formed.(3)Temperature(800-1100?)have a significant effect for the precipitation of interfacical compounds in Cu-20Sn-2Cr/graphite system,and there exists a critical transition temperature between 800? and 900?.At 800?,the interfacial dominated precipitation is Cr₃C₂,and the spreading kinetics conforms to the linear spreading behavior,which is controlled by the interfacial reaction kinetics.When the temperature is higher than 900?(including 900?),the interfacial dominated precipitation is Cr₇C₃,which accord with the thermodynamics of interfacial equilibrium.Among these systems,the wettability of Cu-20Sn-2Cr/Cr_xC_yconfirms that the interfacial reaction products determined the wettability theory,the spreading kinetics is controlled by the diffusion behavior of the active component Cr to the triple line.In summary,the results enrich the basic theory of wetting and spreading of copper-based alloys and carbonaceous materials.Moreover,it may provide a theoretical guidance significance for the manufacturing of high-performance copper/carbon composites.