Extraction Of Yb On Zn Cathode And Preparation Of Zn-Yb Alloys

Alloy plays an indispensable role in modern technology.Alloys are often seen in our life and used in many areas.Magnesium alloy,aluminum alloy and zinc alloy are widely used in mechanical,automotive,aerospace and electronic fields.However,the low hardness and low elastic modulus limit the further application of Mg,A1 and Zn alloys.Rare earth elements as additives in the alloy can greatly improve the performance of the alloy.This paper takes the rare earth Yb as the research object,studied the co-deposition process of Yb???and Zn???ions in the LiCl-KCl molten salt system at W electrode and electrochemical behavior and reduction process of Yb???on the liquid Zn electrode.Yb was extracted from molten salt by molten salt electrolysis and Zn-Yb alloys were prepared.The alloy samples were characterized and analyzed by XRD,SEM and EDS.1.In the LiCl-KCl molten salt system at W electrode at 813 K,firstly,the electrochemical behavior of Yb???was studied by cyclic voltammetry and square wave voltammetry.Then cyclic voltammogram,square wave voltammogram,open circuit transient curve,chronopotentiometry were used to study the deposition mechanism of Yb???in the LiCl-KCl-YbCl₃ molten salt system on liquid Zn electrode.At W electrode,research shows that the process Yb???reduced to metal Yb after two step electron transfer.But the reduction potential of Yb????Yb?0?is more negative than Li???,so the signal of Yb????Yb?0?could not be observed in the potential window.In the LiCl-KCl molten salt system,this paper only calculated the data of Yb????Yb???process.Yb???reduced to Yb???is a reversible reaction,and controlled by diffusion.The diffusion coefficient of Yb???was 1.12×10-5 cm2·s-.The Gibbs free energy and activity coefficient of YbCl₃ were calculated by cyclic voltammetry.On liquid Zn electrode,when the electrode potential is-1.72 V and-1.90 V,two kinds of alloys precipitation peak occur.Underpotential deposition of Yb???on liquid Zn electrode can be measured and two kinds of intermetallic compounds were obtained.Zn-Yb alloys were obtained by galvanostatic electrolysis.XRD,SEM and EDS were employed to analyse the morphology and composition of the alloy.2.Electrochemical research methods like cyclic voltammogram and square wave voltammogram were applied to study the electrochemical behavior of Zn???and Yb???ions in LiCl-KCl molten salt system.By comparison with the phase diagram,the whole deposition potentials of Zn-Yb intermetallic compound were detected.Via potentiostatic electrolysis,Yb was extracted by co-deposition of Zn???and Yb???ions.And the extraction efficiency closed to 99.49%was calculated.YbZn₂,YbZn₁₁ and Yb₃Zn₁₁ were prepared by galvanostatic electrolysis from LiCl-KCl-ZnCl₂-YbCl₃ molten salt system and analysed by XRD,SEM and EDS.3.At 813 K,in LiCl-KCl-ZnCl₂ molten salt system,the electrochemical behavior of Yb₂O₃ was studied by different electrochemical test methods.Experiment shows that the solubility of Yb₂O₃ is low in LiCl-KCl-ZnCl₂ molten salt system.The Zn-Yb alloy peaks are very weak.This phenomenon proves that the efficiency of chlorination ZnCl₂ to Yb₂O₃ is weak.Then XRD,SEM and EDS were employed to analyse the Zn-Yb alloys prepared by galvanostatic electrolysis.The analysis results also show that the content of element Yb in the alloys is very low.