Electrodeposition of magnesium–lithium–dysprosium ternary alloys with controlled components from dysprosium oxide assisted by magnesium chloride in molten chlorides

Abstract

In the work, Gibbs energy showed that MgCl2 can chloridize Dy2O3 and release Dy(III) ions in the LiCl–KCl–MgCl2–Dy2O3 melts. Dy(III) ions were observed by cyclic voltammetry, square wave voltammetry in melts. X-ray diffraction (XRD) pattern of melts indicated that Dy2O3 was chlorinated by MgCl2 and formed DyCl3. XRD pattern of non-dissolved residue, which was left after the melts were washed with water to remove the soluble salt, showed that the new compounds (i.e., DyOCl, MgO, and Dy(OH)3) were produced. The concentration of Dy(III) reached a maximum when the concentration of Mg(II) ions exceeded 8 × 10−4 mol cm−3 in melts by inductive coupled plasma atomic emission spectrometer analyses of melts. Galvanostatic electrolysis was conducted to extract Dy element from LiCl–KCl–MgCl2–Dy2O3 melts by forming Mg–Li–Dy alloys. The components of Dy and Li in alloys were controlled within a small range by the concentration of MgCl2 in melts, current density, and additions of Dy2O3. XRD patterns of alloys indicated that Mg3Dy phase was formed. Scanning electron microscope images with energy-dispersive X-ray spectroscopy showed that Dy elements were mainly distributed in the grain boundary. Grain size was refined, due to a more content of Dy elements in alloys by optical microscopy images.