240th ECS Meeting (Hirokazu Konishi)

The electrochemical formation of Dy-Ni alloys was investigated in a molten CsCl-DyCl3 system at 973 K under a dry Ar gas atmosphere. Open-circuit potentiometry was performed with a Ni electrode after depositing Dy metal at 0.13 V(vs. Cs+/Cs) for 60 s. Five potential plateaus were observed at 0.34 V, 0.44 V, 0.54 V, 0.79 V and 0.91 V, which were considered to correspond to the potentials of two-phase coexisting states of different Dy–Ni alloys. Potentiostatic electrolysis was conducted at 0.31 V for 4 h and 0.41 V for 1 h using Ni plate electrodes, and XRD analysis indicated the formation of DyNi and DyNi2, respectively. After the formation of DyNi2 on the Ni plate electrodes, potentiostatic electrolysis were also conducted at 075 V and 0.85 V for 1 h. The formed DyNi2 was transformed to Dy2Ni7 and DyNi5 at 0.75 V, while DyNi5 was formed at 0.85 V.

Cathodic processes of neodymium(iii) in LiF–NdF3–Nd2O3 melts

In this paper, cyclic voltammetry and square wave voltammetry are applied to characterize the cathode processes of neodymium ions on a W electrode in LiF–NdF3 melts with or without the metal Nd. The results indicate that neodymium ions in the LiF–NdF3 (2 wt%) melt are reduced in two steps, i.e. Nd3+ → Nd2+ and Nd2+ → Nd0, corresponding to starting reduction potentials of 0.35 V vs. Li+/Li and 0.1 V vs. Li+/Li, respectively. The Nd3+ → Nd2+ process is controlled by mass transfer and the Nd2+ → Nd0 process is controlled by both an interfacial step and mass transfer. But in the LiF–NdF3 melt with excess metal Nd equilibrium, the kinetics of the above two processes are controlled by mass transfer. After potentiostatic electrolysis at 0.35 V in the LiF–NdF3–Nd2O3 melt NdF2 is formed on the Mo cathode, and metallic Nd is obtained by potentiostatic electrolysis at 0.1 V in the LiF–NdF3–Nd2O3–Nd melt, which validates the above electrochemical reduction results.