Electrodeposition of Mg-Li-Al-La Alloys on Inert Cathode in Molten LiCl-KCl Eutectic Salt
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RARE earths and their alloys have been widely applied to the development of various functional materials because of their eximious properties.[1–3] Lanthanum and its alloys with Al and Mg exhibit interesting magnetic, glass refractive, hydrogen storage, and improved mechanical properties.[4–6] At present, the combination of thermoreduction, melting for mixing, and metal casting is used in the industrial production of Mg-Li-Al-La alloys, which has many demerits such as a complicated preparation process, intermittent production, serious metals loss, and large energy consumption. Molten electrolysis, however, may offer a novel method in industrial production. Molten salt has been widely accepted in scientific research and industrial production for its unique performance of high solvency, good conductivity, and nonaqueous medium. At present, much progress on molten salt has been made in scientific research. Molten
WEI HAN, Professor, YI SUN, Ph.D. Graduate, TAO JIANG, Postgraduate, and MILIN ZHANG, Professor, are with the Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, P.R. China. QIONG CHEN, Postgraduate, is with China Nuclear Power Operation Technology Corporation, Ltd., Wuhan 430223, Hubei Province, P.R. China and the Department of Equipment Research and Design, Research Institute of Nuclear Power Operation, Wuhan 430223, Hubei Province, P.R. China. Contact e-mail: [email protected] Manuscript submitted May 21, 2011. Article published online September 13, 2011. METALLURGICAL AND MATERIALS TRANSACTIONS B
salt reduction or electrolysis has been used as the commercial production of aluminum, magnesium, sodium, potassium, lithium, beryllium, and several other active metals like lanthanides and actinides, as any other method is not techno-economically feasible.[7] Molten LiCl-KCl salt has been often studied for its lower melting temperature. The eutectic point (59 pct LiCl41 pct KCl, mol pct) is 625 K (352 C).[8] Chen, Smolinski, and Nohira, and their colleagues,[9–14] have studied the preparation or the electrochemical formation process of some alloys by using the molten LiCl-KCl eutectic salt. Castrillejo et al.[15–19] have investigated the electrochemical behavior of some metallic ions on active cathode in the LiCl-KCl eutectic salt. In this article, we report the electrochemical formation of Mg-Li-Al-La from La2O3 on inert cathode in LiCl-KCl(45:55, wt pct) melts at 853 K (580 C). For studying the electrodeposition mechanism, we used a graphite anode and inert cathodes (W and Mo) to do some electrochemical tests in the argon atmosphere. To simulate industrial production, we used an Al rod as the anode for preparation of Mg-Li-Al-La alloys without inert gas protection. Because of the existence of MgCl2, liquid Mg-Li alloy could form on the solid cathode in the electrolysis. The liquid Mg-Li alloy integrating the solid Al-La grew up to be liquid quaternary Mg-Li-Al-La alloy
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