Electrochemical synthesis of Ni-Sn alloys in molten LiCl-KCl

The electrochemical formation of Ni-Sn was investigated in molten LiCl-KCl in the temperature range 380-580 degrees C. Before, an electrochemical study of the Ni2+/Ni-0, Sn4+/Sn2+ and Sn2+/Sn-0 redox couples was performed by cyclic voltametry and chronopotentiometry in a wide temperature range. It had been pointed out that in the case of the Sn4+/Sn2+ redox couple, an insoluble compound is probably formed for T < 460 degrees C. For higher temperature, this compound becomes soluble and then, the shape of the cyclic voltammogram is analogue to the one usually observed when a diffusion-controlled process is involved. The diffusion coefficient values of Ni2+ and Sn2+ ions were determined. For instance, D-Ni(II) and D-sn(II) values deduced from chronopotentiometry were about 2.1 x 10(-5) and 2.7 x 10(-5) cm(2) s(-1) at 440 degrees C, respectively. Then, Ni-Sn alloys have been formed in potentiostatic mode. The electrochemical route proposed in this paper leads to the formation of crystallized alloys with a well-defined composition depending on the operating conditions. (c) 2008 Elsevier Ltd. All rights reserved.