Abstract:By using cyclic and linear sweep voltammetry, the electrochemical deposition behaviors of Mg²⁺ and B³⁺ in fluorides molten salts of KF-MgF₂ and KF-KBF₄ at 880 °C were investigated, respectively. The results show that the electrochemical reduction of Mg²⁺ is a one-step reaction as Mg²⁺+2e⁻→Mg in KF-1%MgF₂ molten salt, and the electrochemical reduction of B³⁺ is also a one-step reaction as B³⁺+3e⁻→B in KF-KBF₄ (1%, 2% KBF₄) molten salts. Both the cathodic reduction reactions of Mg²⁺ and B³⁺ are controlled by diffusion process. The diffusion coefficients of Mg^{2+ ­}in KF-MgF₂ molten salts and B³⁺ in KF-KBF₄ molten salts are 6.8×10^{−7 cm2}/s and 7.85×10^{−7 cm2}/s, respectively. Moreover, the electrochemical synthesis of MgB₂ by co-deposition of Mg and B was carried out in the KF-MgF₂-KBF₄ (molar ratio of 6:1:2) molten salt at 750 °C. The X-ray diffraction analysis indicates that MgB₂ can be deposited on graphite cathode in the KF-MgF₂-KBF₄ molten salt at 750 °C.

Key words: magnesium diboride; electro-deposition; fluoride molten salts; diffusion coefficient