熔盐电脱氧法中氧离子在氯化钙熔盐中的 扩散动力学研究

本文以分子模拟为基础,构建了O2-/CaCl2的全原子模型,以Born-Mayer-Huggins（BMH）势函数对体系进行描述,研究了O2-在CaCl2熔盐的扩散动力学行为。结果表明：1073 K时O2-扩散系数为2.01×10-5 cm2/s,与F.D.Ferro经验公式的计算值一致;同时发现温度与O2-的扩散系数呈正相关关系,拟合得到O2-在CaCl2熔盐中的扩散活化能为15.6 kJ/mol。在微观结构方面,由于静电吸引的作用,熔盐中Ca2+会在O2-周围形成正电配位层,并束缚了O2-的扩散;O2-从形成的Ca2+配位层中逸出需要越过的能垒约为1.7 J。本文不仅揭示了O2-在CaCl2的动力学行为,也为计算机模拟指导研究改良熔盐配方提供研究基础。

Study on the diffusion of oxygen ions in calcium chloride molten salt

In this paper, full-atom models of O2-/CaCl2 were constructed and the systems were described by Born-Mayer-Huggins (BMH) potential function to investigate the dynamic behavior of O2- in CaCl2 molten salt based on molecular simulations. The calculated diffusion coefficient at 1073 K is about 2.01 × 10-5 cm2/s, which is consistent with the reported value of F.D.Ferro"s literature. At the same time, the diffusion coefficient of O2- is closely related to temperatures. When the temperature is increased from 1073 K to 1473 K, the diffusion coefficient is 5.66 × 10-5 cm2/s. The activation energy for diffusion of O2- in CaCl2 molten salt is 15.6 kJ/mol by fitting diffusion coefficients at various temperatures. In terms of the microstructure, Ca2+ can form a positive coordination layer to inhibit the diffusion of O2- due to the electrostatic attraction. Further calculations found that the energy barrier that O2- needs to escape from the Ca2+ coordination layer is about 1.7 J. This article not only reveals the dynamic behaviors of O2- in CaCl2, but also provides guide to research and improvement of molten salt compounds.