Study on the Reaction Between Anodic Gas and Nd in Neodymium Oxide Molten Salt Electrolysis

Neodymium oxide molten salt electrolysis in fluoride systems is the principal method of obtaining Nd and its alloys. However, the quality and performance of the Nd produced are limited by its carbon content, which is generated by the reaction of the anodic gas with Nd during the electrolytic process. In the present study, we investigated the mechanism and controlling factors of this reaction using a series of simulative experiments in which CO was pumped through a Ti tube at certain flow rates into a molten salt system containing a NdF 3 –LiF electrolyte and liquid Nd. The factors considered were the distance from the bottom of the Ti tube to the surface of the molten Nd (L), the temperature, and the electrolyte composition and viscosity. Our results demonstrate that the reaction between CO gas and Nd results in an increase in the carbon content of the Nd. Furthermore, we have established conditions that minimize this increasing carbon content, i.e ., L = 35 mm in NdF 3 85 pct–LiF 15 pct electrolyte at 1323 K. The side dissolution of Nd 2 O 3 and Nd occurs in this electrolyte system, converting the initial NdF 3 –LiF electrolyte system into an NdF 3 –LiF–NdOF–NdF 2 electrolyte system. Furthermore, our study revealed that the viscosity of the NdF 3 –LiF–(Nd 2 O 3 –NdF 2 ) electrolyte system in the temperature from 1323 to 1373 K is between 0.010 and 0.040 Pa s, which is moderately low, and that the addition of Nd 2 O 3 and NdF 2 increases the viscosity of the NdF 3 –LiF electrolyte system.