Electrochemical Behavior Of Sm³⁺ In Fluoride Molten Salt System And Alloy Preparation

Molten salt electrolysis of the rare earth oxide dissolved in the fluoride molten salt system and directly converting it into rare earth or rare earth alloy is a method with good application prospects.In the traditional preparation process of rare earth metals and rare earth master alloys,most of them are thermal reduction methods,which are complicated in steps,cannot be produced continuously,and have low efficiency and high cost.Therefore,the large-scale industrial production of rare earth master alloys by molten salt electrolysis is of great significance.The work of this paper mainly includes the following three parts:First,the electrochemical behavior of Sm³⁺in the Sm F₃-Li F-Sm₂O₃ molten salt system is systematically studied by using the cathode alloying method,through cyclic voltammetry,square wave voltammetry,and timing.Potential and other electrochemical detection methods are used to study the reduction process and mechanism of samarium ions,and to judge the reversibility of the reaction process.It is proved that the reduction process of Sm(III)electrode is controlled by diffusion,and the Sm(III)ions are in the molten salt system through Sander equation.The diffusion coefficient is calculated.Subsequently,the inert W electrode was replaced with active Cu and Ni electrodes,and the corresponding samarium master alloy reduction potential and mechanism were studied.The second part of this thesis adopts the K₃Al F₆-Sm₂O₃ molten salt system to electrolytically prepare aluminum-samarium alloy by co-electrodeposition,and study the electrode reaction process by cyclic voltammetry and square wave voltammetry.The reversibility of the reaction was judged according to the electrochemical detection results,the electron transfer number was calculated,and the diffusion coefficient of Sm(III)in the system was calculated by the increase of the peak current at different sweep speeds.Based on the investigation of electrochemical behavior,the Al-Sm master alloy was prepared by constant potential electrolysis,and the alloy was analyzed by XRD,SEM and EDS.In the third part of this thesis,the first two molten salt systems are mixed,and the liquid cathode electrolysis method is used.The new low-temperature molten salt system electrolytic aluminum-samarium alloy is scaled up to simulate the industrialized electrolytic aluminum-samarium intermediate alloy.By adjusting the ratio of molten salt,electrolysis temperature,current size and electrolysis time,the key influencing factors and optimal process conditions of the electrolysis process under this system are explored.The two aluminum-samarium alloy products with different samarium content were compared and analyzed,and the phase composition and micro morphology of the alloy were observed by XRD,SEM and EDS,and the alloy phase transformation process and the alloy's characteristics during the process of increasing samarium content were investigated.Structural changes.