Cathodic electrochemical behavior in Na_3AlF_6-Al_2O_3-LiF-based melts at tungsten electrode with various cryolite ratios  

作　　者：Shao-Hu Tao Yue-Zhong Di Jian-Ping Peng Ke-Jia Liu Ying-Long Li Nai-Xiang Feng 

机构地区：[1]School of Metallurgy and Materials, Northeastern University

出　　处：《Rare Metals》2018年第1期40-46,共7页稀有金属（英文版）

基　　金：financially supported by the National Basic Research Program of China(No.2013CB632606-1);the National Natural Science Foundation of China(No.51204044)

摘　　要：The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiometry, and open-circuit chronopotentiometry. The results show that the formation process of Al-W intermetallic compound is controlled by both diffusion and charge transfer when the cryolite ratio is below 2.5, and is completely controlled by diffusion when cryolite ratio is above2.5. The deposition process of metal aluminum is completely charge-transfer controlled. Sodium vapor releases along with the deposition of metal aluminum as crylite ratio increases, which leads to a great influence on current efficiency. When the cryolite ratio is lower than 2.0, the critical cathodic current density of deposited aluminum at tungsten electrode is about 150 mA·cm^（-2）,but the current density is above 200 mA·cm^（-2） under other experimental conditions. A higher cryolite ratio can cause a higher cathodic overvoltage. The relative content of Al layer is higher with the decrease of cryolite ratio, and Al layer easily strips into the molten salt when the cryolite ratio is higher than 2.5.The cathodic behavior at tungsten electrode in Na3AlF6-Al2O3-LiF-based melt with various cryolite ratios was investigated by means of potentiodynamic cathodic polarization, potentiostatic electrolysis, chronopotentiometry, and open-circuit chronopotentiometry. The results show that the formation process of Al-W intermetallic compound is controlled by both diffusion and charge transfer when the cryolite ratio is below 2.5, and is completely controlled by diffusion when cryolite ratio is above2.5. The deposition process of metal aluminum is completely charge-transfer controlled. Sodium vapor releases along with the deposition of metal aluminum as crylite ratio increases, which leads to a great influence on current efficiency. When the cryolite ratio is lower than 2.0, the critical cathodic current density of deposited aluminum at tungsten electrode is about 150 mA·cm^（-2）,but the current density is above 200 mA·cm^（-2） under other experimental conditions. A higher cryolite ratio can cause a higher cathodic overvoltage. The relative content of Al layer is higher with the decrease of cryolite ratio, and Al layer easily strips into the molten salt when the cryolite ratio is higher than 2.5.

关 键 词：LiF Cryolite ratio Aluminum electrolysis Cathodic electrochemistry 

分 类 号：TF821[冶金工程—有色金属冶金]