Formation and phase control of Dy alloy films by electrochemical implantation and displantation

The electrochemical formation of Dy-Ni alloys was studied in a molten LiCl- KCl-DyCl3 (0.50 mol %) system at 700 K. Potentiostatic electrolysis of a Ni electrode at 0.55 (vs. Li+/Li), 0.62, and 0.70 V for 2 h resulted ill form ations of the coherent and minute DyNi2 films having thickness of about 60m 30, and 20 mum. respectively. The growth rates of the DyNi2 films were ext remely high, when considering conventional solid phase diffusion. Moreover. the growth rate was dependent on the applied potentials, i.e., higher at m ore negative potentials. Thus, the DyNi2 formation was regarded as a kind o f electrochemical implantation, which was found by the authors previously. The formed DyNi2 electrodes could be transformed to other phases, i.e., DyN i3, Dy2Ni7, DyNi5, and Ni, by electrochemical displantation. The several tr ansformation reactions and the corresponding equilibrium potential were cla rified. The minute DyNi2 films were changed to porous films at more positiv e potentials during the transformation reaction. (C) 2001 The Electrochemic al Society. [DOI: 10.1149/1.1379031] All rights reserved.