Mechanism of Dy and Nd Ions Electrochemical Coreduction with Ni, Co, and Fe Ions in Chloride Melts.

The present paper is devoted to the study of the processes of the mechanism of electrochemical coreduction of Dy and Nd ions with Ni, Co, and Fe ions in the equimolar NaCl-KCl melt at 973 K and characterization of the synthesized samples. The performed voltammetry analysis of the electrochemical coreduction processes elucidated a significant difference in the values of the extraction potentials of the studied metals. This melt testifies that intermetallic compounds of Dy and Nd with Ni, Co, and Fe may be synthesized in the kinetic regime. The intermetallic phases of Dy and Nd with Ni, Co, and Fe are found to be formed along with the phases of metallic Ni, Co, and Fe either during electrolysis at the cathode current densities exceeding the limiting diffusion current of Ni, Co, and Fe ions or in the potentiostatic regime at the potentials of the corresponding voltammetry curves. Therefore, the following interrelated key parameters affecting the electrochemical synthesis of Dy and Nd intermetallic compounds with Ni, Co, and Fe were determined: (i) composition of the electrolyte, i.e., concentrations of FeCl, CoCl, NiCl, DyCl, and NdCl; (ii) cathode current density or electrolysis potential and (iii) electrolysis time. The obtained samples were characterized by micro-X-ray diffraction analysis, cyclic voltammetry, and scanning electron microscopy methods.