Study On Electrodeposited Of NdFeB Permanent Thin Films And Related Properties

In recent years,preparation and development of magnetic materials with integrated magnetic properties(high remanent magnetization,low coercivity and high magnetic saturation induction)becomes one of the key techniques links in the development of microelectronic system which tends to high energy,microscopic and green energy saving.So far,compared with AlNiCo,FeCrCo,and other traditional permanent magnet ferrite permanent magnetic materials,NdFeB materials has the higher remanence,lower coercivity,maximum energy product and also excellent mechanical properties,high density and other advantages.Meanwhile,NdFeB has became the most widely used permanent magnetic material which applied to electronics,precision equipment,engineering preparation,transportation,aerospace and other fields.However,due to the very low deposition potential of rare earth element Nd in NdFeB the formation of the Nd rich phase,it is easy to be oxidized and invalid.Especially in the complex corrosive environment(atmosphere or solution),the surface will rough up easily because of various forms of micro cell formation.All these reasons affected the rapid decline in the mechanical properties and magnetic materials integrated,which greatly hinder the development and application of this materials.Focus on the above problems,this paper carried out research work into two parts.the first part:the cyclic voltammetry technique was used to prepare the nano structure NdFeB thin films on the copper as matrix.On the basis of above,cyclic voltammetry(CV)and electrochemical impedance(Electrochemical impedance spectroscopy,EIS)and electrochemical polarization(Tafel)combined with electrochemical methods such as scanning electron microscopy(SEM),X ray diffraction(XRD)and magnetic vibration scan(VSM)were used to research the internal relationship between the reaction mechanism,the surface morphology and electrochemical,magnetic energy performance of the thin film.The second part is the research on the corrosion behavior of NdFeB thin films prepared by optimization process in 3.5wt.%NaCl solution by using electrochemical noise(Electrochemical Noise EN)and EIS to discuss its evolution process of and corrosion mechanism.The following conclusions are obtained:1.Orthogonal test with four factors and four levels were designed to preliminary study the prepartion peocess of nano-structured NdFeB thin films.And on this basis,the single factor optimization of the main process parameters were obtained:the main salt concentration of NdCl3 was 12g/L,the concentration of FeCl2 was 40g/L,H3BO3 concentration was 36g/L,two complexing agents of glycine and ammonium chloride concentration were both 30g/L,C12H25SO4Na was 0.1g/L,ascorbic acid was 1.2g/L,pH was 2.5 and experiment temperature on 25 degrees,scanning 8 laps,potential window interval for-0.9 VSCE?-1.6 VSCE,scanning speed of 20mV/s.2.The structure,morphology,magnetic properties and electrochemical properties were studied which prepared by the optimized process conditions on NdFeB thin films.The experimental results indicated that NdFeB films electrodeposited by cyclic voltammetry has overall nano-structured,smooth surface and high density.In addition,the formation of films have followed the diffusion of 3D under the control of "instantaneous nucleation/growth mechanism when the cathodic overpotential.3.The corrosion behavior of nanostructured NdFeB thin films in neutral 3.5wt.%NaCl solution was studied.The results showed that:(1)The corrosion potential of the polarization curve was about 200mV,and the corrosion resistance was improved compared to the sintering method.(2)The electrochemical impedance spectroscopy showed that with the prolongation of corrosion time,electrical capacitance arc radius in Nyquist part tended to shrinking.Meanwhile,Rp and Rt also declined,showed that the erosion by anion Cl-.At the same time,the rapid dissolution of the Nd phase also causes the overall failure rate of the material to be self accelerating.(3)The wavelet analysis of energy distribution on the corrosion process of NdFeB thin film in 3.5wt.%NaCl medium can better explain the initial pitting corrosion and subsequent intergranular corrosion with D1 to D8 cell accounted for the proportion of the energy.