Compositions,Microstructures And Properties Of Nanocrystalline NdFeB Films Prepared By Electrodeposition

Rare-earth alloy film has become a new research hot spot because of its excellent magnetic recording,magnetic storage and high magnetic energy.It is an urgent problem for us to prepare a rare earth alloy film with excellent magnetic properties and corrosion resistance by a relatively mild and low energy consumption preparation technology.At present,there are many ways to prepare rare earth alloy magnetic films,such as vacuum deposition,electrodeposition,and so on.In this work,we focused on the influence of the main processing parameters(bath composition,plating conditions,etc.)on the compositions,structures and properties(magnetic properties and corrosion resistance)of NdFeB magnetic films prepared by electrodeposition.we have achieved the experimental results as following:NdFeB films were prepared by electrodeposition in aqueous solution,firstly,the single factor experiment was applied to determine the optimum process conditions of NdFeB films,including pH,bath temperature,current density and electrodeposition time.The optimal process conditions were shown as: the pH was about 3.30,the bath temperature was 50 °C,the current density was 1 A/dm2 and the electrodeposition time was 20 min.Secondly,the electrodeposition process of NdFe B films was determined by orthogonal experiment of bath components.And the optimal composition of the bath component were shown as: the NdCl3,FeCl2,NH4 Cl,HBO3,citric acid and glycine were 8 g/L,22 g/L,25 g/L,20 g/L,20 g/L and 20 g/L,respectively.The coating materials were characterized by SEM,Tafel and XRD technology.The results showed that by using this method,the prepared film had a nanocrystalline structure.Compared with the NdFeB material prepared by conventional sintering,the corrosion resistance,corrosion potential and corrosion current had been further improved,which can be used as a good soft magnetic film.NdFeB films were prepared by electrodeposition under the ultrasonic condition,the effects of pH,electrodeposition time,current density and ultrasonic frequency on the composition,structure and properties of NdFeB films were investigated.The optimal conditions were shown as: pH was 2.4,current density was 2 A/dm2,electroplating time was 10 min,ultrasonic frequency was 45 kHz.The compositions and microstructures of the coating were characterized by SEM,EDS and XRD.The results showed that the films prepared by this method had a nanocrystalline structure,the crystallinity of the prepared samples had greatly improved than those prepared under non-ultrasonic condition,the content of rare earth Nd was obviously increased.The coercivity of the films decreased to 8.05 Oe,the saturation magnetization increased to 68.67 emu/g,and the soft magnetic properties were improved obviously.The corrosion behavior of NdFeB films in 3.0 % neutral NaCl solution was investigated by using the Tafel technique and the electrochemical impedance spectroscopy(EIS)technique.NdFeB prepared in the ultrasonic condition had been more positive corrosion potential and the smaller corrosion current.In addition,EIS complex plane diagram presented two time constant characteristics,the interface resistance Rc and charge transfer resistance Rt had a greater degree of increase,indicating that the corrosion resistance of the film was further improved.