Preparation And Current-carrying Properties Of Nitrogen-doped Graphene/Copper Composite Conductor

With the rapid development of modern electronics,the demand for high power and high-efficiency power transmission is increasing.In order to meet the requirements of a wide range of applications in power systems and the gradual miniaturization of micro-electronic devices,there is an urgent need for conductive materials with high current-carrying capacity.At present,the study focus of high current-carrying conductors focuses on the composite of carbon-based nanomaterials(graphene,carbon nanotubes,etc.)and copper metal.It not only combines the advantages of high conductivity and low cost of copper metal materials,but also makes use of the characteristics of carbon-based nanomaterials such as high electron mobility,high thermal stability and high chemical stability.Therefore,this thesis aims at high current carrying graphene/copper composite material,uses silk fibroin protein solution as carbon source which was prepared by a natural,green and pollution-free silk,and evenly coats the surface of different forms of copper(copper film,copper wire,copper foil)by spinning technology.Microwave plasma technology was used to realize nitrogen-doped graphitization and effective composite with copper.The specific research contents are as follows:(1)The preparation process and characterization technology of nitrogen-doped graphene composite with different forms of copper metal were studied.Firstly,a certain concentration of silk protein solution was obtained through the preparation process of degumming,silk dissolving,dialysis and centrifugation.Secondly,silk protein solution was studied with different metal matrix composite technology,using the template method,electron beam evaporation and electrochemical polishing technology obtained meet performance test requirements of copper film and copper foil substrate,the spiral belt of technology implements the silk fibroin solution with different copper matrix composite,using microwave plasma technology to realize the nitrogen doped graphene/copper composite material synthesis;Finally,the characterization methods of current-carrying density and temperature distribution of composite materials were studied,and the influence of input pulse current duty ratio on current-carrying density was discussed.A set of reliable characterization techniques was proposed,which will provide a valuable reference for conducting current-carrying test.(2)The microstructure and electrical properties of nitrogen-doped graphene/copper film composites were studied.Firstly,the effect of sample size on the current-carrying density of composites was studied.It was found that the current-carrying density decreased with the increase of sample length,increased with the increase of sample width,and decreased with the increase of sample thickness.Secondly,by comparing the current-carrying characteristics of in-situ copper film,microwave plasma treated copper film and nitrogen-doped graphene/copper film,it is concluded that microwave plasma treatment is helpful to improve the current-carrying characteristics of copper matrix,and the copper film with nitrogen-doped graphene has the best current-carrying characteristics.Finally,by comparing the temperature distribution of samples,it is concluded that microwave plasma treatment is helpful to improve the high temperature resistance of copper matrix,and the copper film with nitrogen-doped graphene has the best high temperature resistance.(3)The microstructure and electrical properties of nitrogen-doped graphene/copper wire composites were studied.Firstly,the effect of different microwave power on the current-carrying density of composites was studied.It was found that the current-carrying density increased with the increase of microwave power.Secondly,the effects of different sample sizes,microwave plasma treatment and nitrogen-doped graphene composite on the current-carrying density of the composites were studied,and the conclusion was consistent with that of nitrogen-doped graphene/copper film composites.Then,the influence of the mass ratio of nitrogen-doped graphene on the current-carrying performance of the composite was studied.It was found that the higher the thickness of nitrogen-doped graphene was,the better the current-carrying performance of the composite was under the premise of good continuity.Finally,by comparing the surface temperature distribution of the three samples,it is found that the nitrogen-doped graphene/copper wire composite sample has a good high temperature resistance(681℃).(4)The microstructure and electrical properties of nitrogen-doped graphene/copper foil composites were studied.Firstly,in this paper,the copper foil produced by industry was electrochemically polished.By adjusting the current density and polishing time,the optimum reaction conditions were found,that is,the current density was 2 A/cm~2,the polishing time was 90 s,and the surface roughness was as low as 13.5 nm with hydrophilic copper surface.Secondly,the effect of electrochemical polishing on the current-carrying performance of nitrogen-doped graphene/copper foil composite conductors was studied.It was found that the current-carrying performance of the sample was greatly improved after electrochemical polishing.Then,the effect of sample size on the current-carrying density of the composite was studied.It was found that the current-carrying density decreased with the increase of sample length,which was different from that of the copper film.Finally,by comparing the temperature distribution of high-purity copper foil and nitrogen-doped graphene/copper foil,it is found that nitrogen-doped graphene/copper foil has better high-temperature resistance.