CaCl2的水解反应对固态SiO2显微特征的影响

利用扫描电镜(SEM)和能谱仪(EDS)等手段,并结合热力学理论计算,研究了浸泡在1173 K温度下脱水不完全的CaCl2熔盐中的固态SiO2圆柱样显微特征变化及其原因,初步分析了CaCl2盐的水解反应对固态SiO2电解特性的影响.结果表明,未严格脱水操作的CaCl2盐很容易高温水解,生成的CaO在熔体中的活度只要不低于0.001,即可与SiO2逐级形成CaO·SiO2(CS)、3CaO·2SiO2(C3 S2)和2CaO·SiO2(C2 S)等多种硅酸盐,导致圆柱体外表面的形貌、结构发生较大变化;圆柱体内部渗透进入的熔盐中CaO含量低,形貌变化较小.外表面硅酸盐层的存在使仅内置阴极集流体的固态Si O 2圆柱体电解还原速度减慢和难度增加.

Effect of CaCl2 hydrolysis on micro-characteristics of solid SiO2

By using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), combined with thermodynamic theory calculation, the changes of the microstructure characteristics of solid SiO₂ cylinders immersed in CaCl₂ melt with incomplete dehydration at 1 173 K and their causes were studied. The effect of hydrolysis reaction of CaCl₂ salt on electrolysis characteristics of the solid SiO₂ was preliminarily analyzed. The results show that the CaCl₂ salt without strict dehydration operation is easy to hydrolyze at high temperatures. As long as the activity of the generated CaO in the melt is not less than 0.001, it can react with the SiO₂ to form a variety of silicates, such as monocalcium silicate (CS), tricalcium disilicate (C₃S₂) and dicalcium silicate (C₂S), step by step, which leads to a large change in the morphology and structure of the surface of the SiO₂ cylinder; the internal morphology changes little because of the low CaO content in the melt penetrated into the SiO₂ cylinder. The silicate layer on the surface may slow down the reaction rate and increase the difficulty of the reduction in the solid SiO₂ cylinder with only built-in cathode current collector.