Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 16    No. 5    October 2006

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Electrochemical formation of holmium-copper alloys on copper cathode in molten KCl-HoCl3
SU Yu-zhi(苏育志)1, YANG Qi-qin(杨绮琴)2, LIU Guan-kun(刘冠昆)2

1. School of Chemistry and Chemical Engineering, Guangzhou University, 
Guangzhou 510006, China;
2. School of Chemistry and Chemical Engineering, Zhongshan University, 
Guangzhou 510275, China

Abstract: Cyclic voltammetry, open circuit potential—time curve after potentiostatic electrolysis and potential step chronoamperometry were used to investigate the electrochemical formation processes of holmium-copper alloys on copper cathode in molten HoCl3-KCl. Intermetallic compounds HoCu5, HoCu4, HoCu2 and HoCu are formed in sequence and then the metallic Ho is deposited when Ho3+ is reduced on copper electrode in molten KCl-HoCl3 at 1 066 K. The first charge-transfer reaction is reversible. The structure of holmium-copper alloy film deposited on copper electrode by potentiostatic electrolysis was characterized by X-ray diffraction. The standard free energies of formation for the intermetallic compounds HoCu5, HoCu4, HoCu2 and HoCu are −95.5, −92.6, −73.8 and −44.0 kJ/mol, respectively. The diffusion coefficient and diffusion activation energy of Ho atom in the alloy are estimated to be 10−10−10−11 cm2/s and 75.35 kJ/mol, respectively, from the chronoamperometry data.

 

Key words: holmium-copper alloy; electrochemical formation; free energy of formation; diffusion coefficient

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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