Abstract:

The transport properties of NdF₃-LiF molten salt, such as electrical conductivity and viscosity, significantly impact the electrolytic preparation process of rare earth metal neodymium and the technical economic indicators such as energy consumption in electrolytic production. In this study, molecular dynamics simulations (at 1323 K) were employed to investigate the effect of NdF₃ content on the local structure and transport properties of NdF₃-LiF molten salt. The results indicated that as the content of NdF₃ increased, [NdF₉]^6- and [NdF₈]^5- transformed into [NdF₇]^4- and [NdF₆]^3-. The proportions of bridge fluorine and end fluorine in the fluorine ion connection type increases, among which the proportion of bridge fluorine increases more. In the connection modes of [NdF₈]^5- polyhedrons, the proportion of common vertices decreases, and the proportion of common edges and common faces increases. The order of ion diffusion ability was: Li⁺> F^-> Nd³⁺. As the molar content of NdF₃ increased from 20% to 55%, the viscosity of the molten salt increased from 3.31 mPa·s to 7.43 mPa·s, and the electrical conductivity decreased from 4.84 S·cm^-1 to 1.78 S·cm^-1. This study clarified the transport properties of NdF₃-LiF molten salt and revealed the fundamental reasons for their changes, providing scientific guidance for the low-carbon, green, and efficient preparation of rare earth metal neodymium.

Key words: viscosity, electrolyte, molecular simulation, local structure, transport properties, conductivity, molten salt electrolysis, rare earth metals

摘要：

NdF₃-LiF熔盐的输运性质（如电导率、黏度）对稀土金属钕的电解制备过程及电解生产的电能消耗等技术经济指标影响很大。本研究采用分子动力学模拟，在温度为1323 K的条件下研究了NdF₃含量对NdF₃-LiF熔盐局域结构和输运性质的影响。结果表明，NdF₃含量增加时，[NdF₉]^6-和[NdF₈]^5-向[NdF₇]^4-和[NdF₆]^3-转变；氟离子连接类型中桥氟和端氟的占比均增加，其中桥氟占比上升幅度更大；[NdF₈]^5-多面体间的连接方式中，共顶角占比下降，共棱和共面的占比增加；离子的扩散能力排序为：Li⁺ > F^- > Nd³⁺。随着NdF₃摩尔含量从20%增加到55%，熔盐黏度从3.31 mPa·s增加到7.43 mPa·s，电导率由4.84 S·cm^-1降低到1.78 S·cm^-1。本研究明确了NdF₃-LiF熔盐的输运性质，并揭示了其变化的本质原因，为稀土金属钕的低碳、绿色、高效制备提供了科学指导。

关键词: 黏度, 电解质, 分子模拟, 局域结构, 输运性质, 电导率, 熔盐电解, 稀土金属