Electrochemical Behaviour Of Dy(?) And Ho(?) And The Prepatation Of Dy-Ni,Ho-Ni And Mg-Li-Dy-Ho Alloys In Molten Salts

The electrochemical prepapration and mechanism of Dy-Ni, Ho-Ni and Mg-Li-Dy-Ho intermetallic alloys were studied in molten salts. The electrochemical behaviors of Dy??? and Ho??? ions were investigated on inert W and reactive Ni electrodes in LiCl-KCl-Dy?Ho?Cl3 molten salts. The electrochemical co-deposition mechanism of Dy??? and Ho??? ions on a reactive Ni electrode was discussed. And then the Dy-Ni and Ho-Ni intermetallic alloys were prepaprated. The electrochemical behavior of LiCl-KCl-MgCl2-DyCl3-HoCl3 molten salts was investigated on an inert W. The co-deposition mechanism of Mg???, Dy??? and Ho??? was discussed and the Mg-Li-Dy-Ho alloys were prepaprated by galvanostatic electrolysis.?1? At 773 K,the electrochemical behaviour of Dy??? ions in LiCl-KCl-DyCl3?2.50×10-4 mol·cm-3? melts on inert W and reactive Ni electrodes were investigated. The electrochemical reduction of Dy??? ions process was determined to exchange three electrons process, the reduction of Dy??? ions was reversible process when the scan rate was less than 30 mV·s-1 and was controlled by mass transfer. The diffusion coefficient of Dy??? was calculated to be 0.18×10-5 cm2·s-1. Cyclic voltammograms on a Ni electrode show that dysprosium and nickel can form three Dy-Ni intermetallic compounds. The three Dy-Ni intermetallic compounds obtained by potentiostatic electrolysis at -1.6 V, -1.8 V and -2.0 V were analyzed by XRD and SEM/EDS.The analysis results fonfirmed the formation of DyNi5?Dy2Ni7 and DyNi2. The Gibbs free energies of formation of DyNi5,Dy2Ni7 and DyNi2 were calculated by OCP.?2? At 1023 K,the electrochemical behaviour of Ho??? ions in LiCl-KCl-HoCl3?2.50×10-4 mol·cm-3? melt on inert W and reactive Ni electrodes were investigated. The electrochemical reduction of Ho??? ions process was determined to exchange three electrons process. The reduction of Ho??? ions was reversible process when the scan rate is less than 50 mV·s-1 and was controlled by mass transference. The diffusion coefficient of Ho??? was calculated to be 0.19×10-5 cm2·s-1. Cyclic voltammograms on a Ni electrode show that holmium and nickel can form three Ho-Ni intermetallic compounds. They were obtained by potentiostatic electrolysis with different time at -1.8 V and -2.2 V, respectively. Then the three alloy samples were analyzed by XRD and SEM/EDS, which confirmed the formation of Ho2Ni17, HoNi5 and HoNi2. The Gibbs free energies of formation of Ho2Ni17, HoNi5 and HoNi2 were calculated by OCP.?3? At 1023 K,the electrochemical behaviour of LiCl-KCl-MgCl2-DyCl3-HoCl3 melts on an inert W electrode was investigated. The Dy???, Ho??? and Mg??? can occur co-deposition when the cathode current density was less than -0.22 A?0.68 A·cm-1? or cathode potential was more negative than -2.4 V. The Mg-Li-Dy-Ho alloys were prepaprated by galvanostatic electrolysis. The effects of electrolytic time, electrolytic temperature and current intensity on the current efficiency and of electrolytic temperature, current intensity and the addition amount of MgCl2 on alloy composition were studied. The current efficiency can reach a maximum ?72.6%?while the cathode current intensity reaches 2.5 A at 973 K for 2 h. With the concentration of MgCl2 increasing in LiCl-KCl-MgCl2-DyCl3-HoCl3 melts, the content of magnesium increases,while the content of lithium decreased significantly in the Mg-Li-Dy-Ho alloy. The XRD results showed that ?-Li, Mg₂Dy, Mg₂Ho and a-Mg phases coexisted in Mg-Li-Dy-Ho alloys. The SEM/EDS results showed the rare earth elements uniformly distribute in the Mg-Li-Dy-Ho alloys.