氟盐-氧化物体系熔盐电解制备Dy-Cu中间合金基础理论研究

Dy-Cu alloy has strong magnetic susceptibility and promising application prospects as magnetostrictive or magnetic refrigeration materials. Currently, the main preparing methods of Dy-Cu alloy are mixed melting metal and thermal reduction. Molten salt electrolysis is another method for preparing of rare earth alloy with its inherent advantages, but the research is rarely reported in terms of Dy-Cu alloy. The purpose of this project is prepared for Dy-Cu master alloy by molten salt electrolysis in fluoride salt-oxide system. The basic physical and chemical properties of DyF3-(Li/Na)F-Dy2O3-Cu2O molten system such as the fusibility, density, conductivity, especially the solubility of Cu2O and Dy2O3 are been determined. The potential scan, step and pulse, the impedance electrochemical technologies and basic principle of electrochemical with computer analytic techniques to reveal the electrode polarization rule, the electrode process and mechanism of alloying, and alloy diffusion coefficient, diffusion activation energy, the control steps of electrode reaction of Dy(III) and Cu(I) ion in the melt. Exploring the calculation model of current efficiency, optimizing internal and external electrolytic conditions, studying the dissolution losses of Dy-Cu liquid metal and Secondary interactions mechanism in the molten salt system through constant voltage or constant current electrolysis. The purpose of the investigation is providing the theoretical basis of preparing Dy-Cu master alloy by molten salt electrolysis in fluoride salt-oxide system.

Dy-Cu合金具有较强的初始磁化率，在磁致伸缩、磁致冷方面具有非常广阔的应用前景。目前，制备Dy-Cu合金主要是对掺法、金属热还原法，熔盐法电解是制备稀土合金另一方法，具有其固有优越性，但在制备Dy-Cu合金方面少有报导。本项目拟采用氟盐-氧化物体系熔盐电解制备Dy-Cu中间合金，对DyF3-(Li、Na)F体系的熔度、密度、电导率基本熔盐物理化学性质，尤其对Dy2O3和Cu2O的溶解机制进行研究；运用电位扫描、阶跃与脉冲、阻抗等电化学技术及计算机解析和揭示电极极化规律、Dy(III)及Cu(I)离子的电极过程及合金化机理，Dy(III)、Cu(I)离子在熔体及合金中扩散系数、扩散活化能以及电极反应的控制步骤。通过恒压或恒流电解，探索电流效率的计算模型、内外部电解条件的优化及液态Dy-Cu金属在体系中的溶解损失及二次作用机理，为氟盐-氧化物体系电解制备Dy-Cu合金的应用建立理论基础。

Dy-Cu合金具有较强的初始磁化率，在磁致伸缩、磁致冷方面具有非常广阔的应用前景，但其主流制备方法存在合金易烧损、成分偏析严重等缺点。基于熔盐电解固有优越性，本项目提出在LiF-DyF3-Dy2O3-Cu2O体系中熔盐电解制备 Dy-Cu 合金新方法，在制备Dy-Cu中间合金的同时，对LiF-DyF3、LiF-DyF3-Dy2O3、LiF-DyF3-Cu2O体系的密度、电导率、粘度基本物理化学性质，尤其对Dy2O3和Cu2O的溶解机制进行了深入的研究，得出了电解制备Dy-Cu合金的电解质体系的基本物理化学参数，揭示 Dy2O3、Cu2O在氟盐介质中溶解度的变化规律及溶解机理，解决了如何提高 Dy2O3在氟盐体系中溶解度的问题。此外，运用电化学技术解析和揭示Dy(III)及Cu(I)离子的电极过程及合金化机理，Dy(III)、Cu(I)离子在熔体及合金中扩散系数、扩散活化能以及电极反应的控制步骤，发现电解过程中Cu(I)在熔盐中会氧化为Cu(II)再参与合金化，Dy(III)在阴极上合金化过程为一步还原，反应受扩散控制。在上述研究的基础上，探讨了电解内、外部条件对电流效率、Dy-Cu合金的表面形貌影响，确定了电解工艺条件及成分调控的最佳技术参数，为氟盐-氧化物体系电解制备Dy-Cu合金的应用建立理论基础。