Study On Surface Metallization And Deposition Kinetics Of Carbon Fiber

Carbon fiber has been widely used due to its high specific strength,high specific modulus,low density,high temperature resistance,radiation resistance,fatigue resistance,well electrical and thermal conductivity,small thermal expansion coefficient and excellent performance.It is now often used as a reinforcing phase resin,metal,ceramics,concrete and other materials to form composite materials.Metal-based carbon fiber composite material not only inherits the carbon fiber's high specific strength,high specific modulus and good toughness,excellent performance,but also maintains the characteristics of the base metal.It is becoming an important research area in recent years,broadly applying to aerospace,bio-materials and civilian industry area.However the wettability between carbon fiber and metal matrix is poor.When the composite material is subjected to a certain load,it is likely to make the carbon fiber detached.Therefore,it is the key issue to improve the adhesion of carbon fiber and the matrix metal between the metal-based carbon fiber composite materials.This dissertation studied electroplating nickel,copper and nickel-copper on carbon fiber surface.Orthogonal test and single factor experiments were applied to determine the optimum conditions of three kinds of coatings.Through the thermodynamic and kinetic perspective,the formation and reaction mechanism of various coatings was analyzed.The main research results are listed as follows:?1?The optimum technique of electroplating nickel on carbon fiber surface is: nickel sulfate 200 g/L,nickel chloride,60 g/L,boric acid 40 g/L,sodium lauryl sulfate 0.1 g/L;a current density of 0.56 A/dm2,plating time 6min,temperature of 50?.The time of plating affects the growth rate of carbon fibers most,followed by the current density,the concentration of boric acid,and finally nickel sulfate concentration.Bath temperature changes will cause the changes on the morphology of the coating,but the impact on the coating thickness is not significant.The thickness of layer is a linear relationship with the current density is and the time.When the current density and plating time increased,the coating thickness is gradually increased;when the current density increases,the surface of the coating appears as cell structure,and the degree of roughness increases.The reaction series of Ni²⁺ concentration and H₃BO₃ concentration were a=-0.0886 and b=0.0304 of nickel-plated carbon fiber,reaction activation energy Ea=4023.31 J/mol.?2?The optimum technique of electroplating copper on carbon fiber surface is: copper sulfate 200 g / L,sulfuric acid 60 g/L,potassium nitrate,30 g/L,brightener 0.1 g/L;voltage of 2.5V,plating time 7min.The Plating time deeply affects on the growth rate of carbon fibers,followed by the voltage,then the concentration of copper sulfate,sulfuric acid concentration.The reaction series of Cu²⁺ concentration and H⁺ concentration were a=0.4609 and b=-0.1935 of nickel-plated carbon fiber,reaction activation energy Ea=5545.44 J/mol.?3?The layer surface is smooth,flat,and the coating thickness is uniform if Ni-Cu complex electroplating on carbon fiber.When the thickness is less than 1.56 ?m,coating adhesion meet the requirements,which is ideal for coating.With the increase of the thickness of the nickel layer,the deposition rate of the copper layer also increases.