Direct electrolytic preparation of chromium metal in CaCl_2-NaCl eutectic salt

The electro-reduction of chromium oxide（Cr2O3） was investigated in an equimolar mixture of CaCl2-NaCl molten salt at 800℃ for developing a more efficient process for chromium preparation. Cyclic voltammetry and potentiostatic electrolysis were used to study the electro-reduction of the Cr2O3-loaded metallic cavity electrode. In addition, a number of parameters affecting the rate and extent of Cr2O3 electrolysis were considered to better understand the electrolysis process. The results demonstrate that CaCl2-NaCl molten salt is applicable for preparing Cr directly from Cr2O3 and the electrolysis parameters exert great influence on the cathode product. Under optimal experimental conditions, nodular Cr with an oxygen content of 0.5%（mass fraction） was obtained without any chromium carbides detected by XRD. Furthermore, the relatively high solubility of CaO and quite rapid crystal growth result in the formation of large platelet CaCr2O4, and the addition of NaCl to CaCl2 results in several variations on the electrolysis process and the product morphology from pure CaCl2 molten salt.

CaCl_2-NaCl熔盐中Fe^(3＋)电化学行为的循环伏安分析

利用ZrO_2(Y_2O_3)固体电解质管集成构建Pt,O_2(air)|ZrO_2作为参比电极的电化学电池,采用循环伏安法在1273、1323、1373、1393K温度下对溶解0.5%Fe2O3的CaCl2-NaCl共晶熔盐中Fe^(3+)的电化学行为进行研究,分析了Fe^(3+)在Pt电极上的还原机理,并计算了电极反应交换电子数、Fe^(3+)扩散系数与Fe^(3+)扩散活化能等电化学参数。结果表明,在实验温度范围内,熔盐中Fe^(3+)在Pt电极上还原为Fe的反应是一步还原并受扩散控制的可逆过程;随着温度升高,Fe^(3+)扩散系数增大,Fe^(3+)扩散活化能为97.91kJ·mol-1。另外,本实验测得的Fe^(3+)扩散系数与文献值基本相符,因此,可以认为利用该电化学电池装置研究溶解有Fe2O3的CaCl2-NaCl溶盐的电化学行为是可行的。

影响CaCl_(2)-NaCl熔盐电脱氧法制备金属Zr的工艺条件

将氧化物转化为金属是熔盐电解精炼干法后处理氧化物乏燃料流程的关键步骤之一。在等摩尔CaCl_(2)-NaCl混合熔盐体系中,以石墨棒为阳极,采用高温烧结后的ZrO_(2)模拟UO_(2)开展了电脱氧制备金属Zr的FFC剑桥工艺条件优化。研究了工艺条件(槽电压、电解时间、烧结温度和电解温度等)对电脱氧制备Zr的影响。采用场发射扫描电子显微镜(SEM)和X射线衍射(XRD)分别分析了电解前后ZrO_(2)阴极的微观结构和物相组成。优化后的工艺条件为:电压3.4 V、电解时间12 h、烧结温度900℃和电解温度722℃。同时,研究结果表明,ZrO_(2)电脱氧还原为Zr时,存在中间产物CaZrO_(3)和ZrO。