Effect Of Carbon Fiber And Coating Modification On Properties Of Copper-plated Carbon Fiber

Owing to their high strength and modulus,and low expansion coefficient and density,carbon fibers(CFs)are extensively used in aerospace,transportation,construction,sports and medical equipment,and other fields.Furthermore,conductive or electromagnetic-shielding materials prepared using CFs and their composites are lightweight,exhibit high strengths,and can replace conventional metal-based materials.However,because the resistivity of CFs is much higher than those of metals,the material conductivity and electromagnetic shielding are poor,which hinders the further application of this kind of material.Copper plating on carbon fiber surface is an effective way to improve the electrical conductivity of carbon fiber.However,in the current research on copper plating,most scholars usually focus on the exploration of copper plating process,but there are few studies on the influence of carbon fiber performance on copper plating,and the copper layer obtained by electroplating is of poor quality,and the resistivity of carbon fiber electroplating is still high.In order to solve the above problems,this paper carried out the following research:on the basis of carbon fiber electroplating copper,annealing was used to improve the quality of the coating,an the influence of annealing on the electrical conductivity and mechanical properties of copper-plated carbon fiber was studied;Different carbon fibers were used for copper plating,and the influence of carbon fiber properties on carbon fiber copper plating was analyzed;A layer of nickel was deposited before electroplating copper on carbon fiber.The effects of nickel precoating on electrical conductivity and mechanical properties of copper-plated carbon fiber were studied.In this paper,X-Ray Diffraction Analysis,X-ray photoelectron spectroscopy,Scanning Element Microscope,and other measurement methods were used to analyze the structure of copper coated carbon fiber,and the influence of grain boundaries on the electron transport characteristics of copper metal was simulated based on density functional tight binding and non-equilibrium Green’s function method.The main conclusions reached are as follows:(1)After copper coating was prepared on the surface of carbon fiber by electroplating,the conductivity of carbon fiber increased from 0.598× 103 S/cm without copper plating to 1.07×103 S/cm.However,the copper layer is rougher and not dense enough.After annealing for 20 min,the conductivity of the copper-coated carbon fiber increases greatly.When the annealing temperature reaches 600℃,the conductivity increases from 1.07×103 S/cm to 84.2×103 S/cm.At the same time,the mechanical properties of copper-coated carbon fiber are also improved after annealing.The strength and modulus of copper-coated carbon fiber increase from 2.14 GPa and 123.58 GPa in unannealed condition to 2.98 GPa and 147.22 GPa at 600℃,which increase by 39%and 19%,respectively.The improved conductivity of copper-plated carbon fiber after annealing is due to the less surface defects of the copper layer and the growth of the grain.The existence of grain boundaries can reduce the probability of electron transmission and the current through the system,and reduce the uniformity of atomic potential distribution in the central region of the structure,which hinders the transmission of electrons.(2)Binding force between copper coating and carbon fiber was related to the degree of graphitization of carbon fiber,and the proportion of carbon atoms with sp2 hybrid structure in carbon fiber decreased with the increase of the degree of structural disorder of carbon fiber.The interface bonding ability between carbon fiber and copper coating increases gradually,the coating shedding rate decreases,and the electrical resistivity of copper-coated carbon fiber decreases with the decrease of the graphitization degree of carbon fiber.After annealing,the electrical conductivity of different coppered carbon fibers is greatly improved,and the coating shedding rate is significantly reduced.This is because the defects of the copper layer are reduced after annealing,and the coating quality is greatly improved,which makes the coating form a firm ring tightly on the fiber surface and increase the conduction path of electrons.(3)Pre-nickel plating can effectively improve the electrical conductivity and mechanical properties of copper-plated carbon fibers.The electrical conductivity of the directly copper plated carbon fibers and pre nickel plated and copper plated carbon fibers are 1.07×103 S/cm and 4.75×103 S/cm,respectively,and the tensile strength is 2.14 GPa and 2.73 GPa,respectively.Increased by 343.92%and 27.57%respectively.The reason for the improvement is that the preplated nickel layer improves the interfacial bonding property between the copper layer and the carbon fiber.After annealing,the electrical and mechanical properties of the carbon fiber can be further improved,and the electrical conductivity and tensile strength can reach 49.81×103 S/cm and 2.78 GPa,respectively,which are 948.63%and 1.83%higher than those of the sample without annealing,respectively.The reason for the improvement is still that annealing improves the quality of the coating.