Electrochemical Behaviour Of Heavy Rare Earth (Lu、Yb)and The Preparation Of Associative Alloys

The electrochemical behaviour of Lu(III)、Yb(III) ions and mechanism ofelectro-deposition were investigated by transient electrochemical methods such ascyclic voltammetry, chronoamperometry open-circuit chronopotentiometry in moltensalts system. Moreover, the obtained Mg–Li–Lu, Al–Li–Lu, Al–Lu–Yb alloysinvestigated by galvanostatic electrolysis were characterized by XRD, SEM andICP-AES.First,the electrochemical behavior of Lu(III) ions was investigated in the melts ofLiCl–KCl and LiCl–KCl–MgCl2molten salts on Mo electrode.The results show thatthe electrochemical reduction of Lu(III) occurre in one reaction step with an exchangeof three electrons. The diffusion coefficient of Lu(III) ions in LiCl–KCl melts systemwas calculated by cyclic voltammetry, chronopotentiometry and chronoamperometry.Lu(III) ion diffusion activation energy was calculated by arrhenius equation. A typicalcyclic voltammetry with different scan rates in LiCl–KCl melts system show thatcathodic/anodic reaction of Lu(III) and Mg(II) ions are quasi-reversible andirreversible respectively. The co-electrodeposition mechanism of Mg, Li and Lu wasstudied on a Mo electrode in LiCl–KCl–MgCl2–LuCl3melts, which indicates thatwhen the current desity is lower than-0.47A.cm-2the electrochemical codeposition ofMg, Li and Lu metal occurre Mg–Li–Lu alloys.The microstructure of the Mg–Li–Lualloy prepared by galvanostatic electrolysis was characterized by scanning electronmicroscopy (SEM).Then,the electrochemical behaviour of Lu(III) ion was explored in the LiCl–KCleutectic mixture on molybdenum and aluminium electrodes, respectively the resultsindicate that the deposition potential value on aluminium electrode was more positivethan the one on inert electrode. Lu(III) appear underpotential deposition (referred to asUPD) and the UPD decrease gradually with the increasing of Lu(III)concentration.The phase composition and microstructure characteristics of alloyspreprared via the constant potential electrolysis were observed.The electrochemicalbehaviour of Al(III)、 Lu(III)、 Li(I) ions was investigated in the melts ofLiCl–KCl–AlCl3–Lu2O3, which indicate that when the current densities are lower than-0.31A.cm-2or the applied potential more negative than–2.30V(vs.Ag/AgCl) the electrochemical codeposition of Al, Li and Lu metal occurred.Last, the electrochemical behaviour of Yb(III) and Lu(III) ions in the LiCl–KCleutectic molten salts and Al(III)、 Lu(III)、 Yb(III) ions were studied in theNaCl–KCl–YbCl3–LuCl3–AlF3eutectic molten salts.The Al–Lu–Yb alloys wereobtained by galvanostatic electrolysis. ICP results show that the composition ofAl–Lu–Yb alloys could be adjusted by controlling electrolytic time.