Study On The Structure And Properties Of Electrodeposition Nickel-base Electromagnetic Shielding Coating With Rare Earth Joined

Amorphous nickel-base electromagnetic shielding coatings were obtained by the technique of electrodeposition in this paper.The effect of different technological conditions on the speed of plating and the surface quality was studied. The results showed that the speed of metallic ion depositing descends,but adhesion of the coating and matrix, throwing power of the bath and the surface quality of coating were improved diversely on the condition of a small amount of lanthanum and cerium doped in plating bath. The optimism Ni-P-La and Ni-P-Ce plating bath composition and operating conditions of such technology were presented. Electrochemical characteristic of different plating baths was observed and analysed. The result shows that the double-eletrolic structure of electrode surface was changed, polarizability was increased, peak current of cyclic voltammetry curves was reduced, the surface quality of coatings was changed at the same time, due to a small amount of RE doped in plating baths.The effects of RE on the chemical composition, crystal structure and surface morphology of electro- deposition Ni-P alloy coatings were analysed by means of plasma transmitting spectrograph, electron energy spectrometer, X-ray diffractometer, transmission electron microscopy and scan electron microscopy. The results showed that chemical composition of nickel and phosphorous was changed, microcrystalline structure of Ni-P alloy was transformed into amorphous structure of Ni-P-RE alloy after rare earth entered into the coating. Heavy RE(Dy,Y) promotes amorphous ability better than light RE(La,Ce). Surface of amorphous Ni-P-RE alloy is molecule dimension plane, while surface of microcrystalline Ni-P alloy is microcosmic unsmooth from AFM diagrams of coatings. Corrosion resistance of coating with RE under the salt spray was investigated. Erosion velocity of coatings in NaCl,HCl,H2SO4,NaOH solution were compared, corrosive resistant of Ni-P-RE alloys was improved with an appropriate amount of RE added.Ce promotes corrosive resistant of Ni-P alloy coatings batter than La. Electromagnetic shielding effectiveness of the samples under the different concentration of rare earth or the different condition was tested with the network analyzer. Electromagnetic shielding effectiveness of monolayer and coatings package the wave-proof sleeve (double layer)was compared.Theresults show that Ni-P-La alloy coating exhibits moderate shielding effectiveness (from 45 to 70dB) when the frequency is between 10 and 350MHz and erodibility of the salt spray has a little influence of electromagnetic shielding effectiveness. A small amount of rare earth doped in plating bath can enhance 1 ~ 5dB of electromagnetic shielding effectiveness, electromagnetic shielding effectiveness of double layer is from 60 to 85dB.