Study On Preparation Of Nickel Coated Carbon Fibers And Its Orientation Under The Magnetic Field

Carbon fiber(CF) is a kind of conventional both reinforcing and functional fillers. It possesses such advantages as high modulus, high strength, good thermal and electrical conductivity, low density and thermal expansivity. However, it has the disadvantages as low adhesion between CFs and matrix in composites due to the smooth surface of CFs and the lack of polar groups on CFs as well as poor electro and magnetic property than that of metals. Surface modification of CFs is effective to improve the performance of CFs and widening their application. Electroless plating nickel on CFs can greatly enhance the surface property of CFs, which endue CFs with metal-like thermal, electrical and magnetic properties and such characteristic as high strength and low density can be kept as well.Firstly, nickel coated carbon fibers (NiCF) with different and uniform thickness of coating were prepared by electroless plating method. Orthogonal experiment was carried out to optimize the formula for plating solution and process. Then the optimal plating solution formula and process conditions were obtained after trials and error of factors for plating, that's,35g/L nickel sulfate,30g/L sodium hypophosphite, 10g/L sodium citrate,2mg/L thiocarbamide, pH=9～10, plating temperature=60℃. X-ray diffraction(XRD), optical microscope(OM) and scanning electron microscope(SEM) were utilized to investigate the effect of such factors as reducing agent, complexing agent, plating time, plating temperature, pH, dispersion and desizing on nickel plating. Resistivity of nickel coated carbon fibers is about 0.5×10-5Ω·cm.Then, home-made NiCFs used as fillers and poly(vinyl alcohol) (PVA) as polymer matrix were compounded by sol-gel method with DMSO/H2O as mixing solvent, further orientated NiCF/PVA composites by magnetic field were prepared. Besides, the relationship between viscosity of PVA solution, time and temperature was examined by a great lot of experiments to determine the optimal experimental conditions for orientation of NiCF in the magnetic field. SEM, XRD, OM and electrical conductivity test were performed to explore the orientation of NiCF in magnetic field. The results demonstrated that orientated NiCF/PVA composites were realized by magnetic field, which were anisotropic conductivity.