钕电解氟化物体系熔化温度及高温物相的研究

Melting Temperature and High-temperature Phase Research on Fluoride System of Neodymium Electrolysis

为了提高钕熔盐电解的效率,对钕电解的二元体系NdF3-LiF及三元体系NdF3-LiF-Nd2O3熔盐加热到1100℃、急冷法制备分析样品,同时在电解槽中取熔盐,用急冷法制样,使用DSC-TG测定熔盐在加热过程中重量及热量变化,使用XRD、TEM分析急冷熔盐的样品组成和结构。研究表明,NdF3-LiF二元体系及NdF3-LiF-Nd2O3三元体系的共熔温度分别为723℃和725℃,共熔相的数量随着LiF的质量而增加,随Nd2O3质量增加及Nd2O3加入而降低,熔化温度随LiF含量降低而升高,随Nd2O3质量增加先降低而后升高,电解槽中熔盐的共融温度及熔化温度在712℃及970℃,实验样品在约900℃开始出现熔盐的挥发,电解槽中的样品几乎没有熔盐挥发;二元系及三元体系样品中分别含有NdF3、LiF和NdF3、LiF、Nd OF、NdF2,三元系样品中加入的Nd2O3在高温完全熔解,生成Nd OF、NdF2,电解槽中的样品含有未熔解的Nd2O3。通过实验初步确定了钕电解熔盐随着熔盐成分变化、熔盐熔化温度的变化及Nd2O3的熔解状况,确定了电解槽熔盐中存在Nd2O3及挥发组分含量偏低,对现场工艺改进及控制具有一定的指导作用。

In order to improve the efficiency of the neodymium molten salt electrolysis,NdF3-LiF and NdF3-LiF-Nd2O3 specimens were prepared by being heated to 1100 ℃ and quenched. Specimens of molten salt in the electrolytic cell were also prepared by being quenched. Weight and heat changes of specimens were studied by DSC-TG in the heating process,the composition and structure were studied by XRD and TEM. The results showed that eutectic temperature of NdF3-LiF binary system and NdF3-LiF-Nd2O3 ternary system was 723 ℃,725 ℃. The number of the eutectic phases increased with the increasing of LiF but decreased with the increasing of Nd2O3. The melting temperature increased as LiF content decreased but decreased first and then increased with the increasing of Nd2O3. The eutectic temperature and melting temperature of the specimens of molten salt in the electrolytic cell were 712 ℃ and 970 ℃,respectively. The molten salt of the test samples began to volatilized at 900 ℃,while that in the electrolytic cell hardly volatilized. NdF3-LiF specimens prepared by rapid quenching method contained NdF3,LiF,while NdF3-LiF-Nd2O3 contained NdF3,LiF,Nd OF and NdF2. Nd2O3 in NdF3-LiF-Nd2O3 was melted completely at high temperature,which generated Nd OF and NdF2. And the unmolten Nd2O3 was found in the electrolytic cell.The experiment preliminarily determines that the melting temperature of the molten salt and fusion status of the Nd2O3 change with the molten salt composition changing,and Nd2O3 exists in molten salt specimens in the electrolytic cell due to the decrease of the volatile content. The research has a certain guiding role for the process improvement and site control.