Equilibrium between titanium ions and high-purity titanium electrorefining in a NaCl-KCl melt

Abstract

TiCl _x (x = 2.17) was prepared by using titanium sponge to reduce the concentration of TiCl₄ in a NaCl-KCl melt under negative pressure. The as-prepared NaCl-KCl-TiCl _x melt was employed as the electrolyte, and two parallel crude titanium plates and one high-purity titanium plate were used as the anode and cathode, respectively. A series of electrochemical tests were performed to investigate the influence of electrolytic parameters on the current efficiency and quality of cathodic products. The results indicated that the quality of cathodic products was related to the current efficiency, which is significantly dependent on the current density and the initial concentration of titanium ions. The significance of this study is the attainment of high-purity titanium with a low oxygen content of 30 × 10⁻⁶.

Keywords

titanium / electrodeposition / ionic equilibrium / high purity materials / oxygen concentration

References

[1] Suresh A. High-purity Titanium Sputtering Target and Method of Making, 2005

[2] Yoshimura Y, Inoha Y. Method for Obtaining High Purity Titanium, 1993

[3] Lam RKF. High purity titanium refining by iodide purification. Symposium on Titanium Extraction and Processing, Indianapolis, 1997 3

[4] Spadafora F P, Yu KO. Method of Melting Titanium and Other Metals and Alloys by Plasma ARC or Electron Beam, 2002

[5] Okabe TH, Naksmura M, Oishi T, Ono K. Electrochemical deoxidation of titanium. Mater. Trans. B, 1993, 24(3): 449.

[6] Rosenberg H, Winters N, Xu Y. Apparatus for Producing Titanium Crystal and Titanium, 2000

[7] Wurm JG, Gravel L, Potvin RJA. The mechanism of titanium production by electrolysis of fused halide baths containing titanium salts. J. Electrochem. Soc., 1957, 104(5): 301.

[8] Reid WE. The mechanism of electrolytic deposition of titanium from fused-salt media. J. Electrochem. Soc., 1961, 108(4): 393.

[9] Ning XH, Asheim H, Ren HF, Jiao SQ, Zhu HM. Preparation of titanium deposit in chloride melts. Metall. Mater. Trans. B, 2011, 42(6): 1181.

[10] Ferry DM, Picard GS, Trémillon BL. Pulse and AC impedance studies of the electrochemical systems of titanium in LiCl-KCl eutectic melt at 743 K. J. Electrochem. Soc., 1988, 135(6): 1443.

[11] Lantelme F, Kuroda K, Barhoun A. Electrochemical and thermodynamic properties of titanium chloride solutions in various alkali chloride mixtures. Electrochm. Acta, 1998, 44(2-3): 421.

[12] Chassaing E, Basile F, Lorthioir G. Electrochemical behaviour of the titanium chlorides in various alkali chloride baths. J. Appl. Electrochem., 1979, 68(2): 153

[13] Straumanis ME, Shih ST, Schlechten AW. The mechanism of deposition of titanium coatings from fused salt baths. J. Electrochem. Soc., 1957, 104(1): 17.

[14] Komarek K, Herasymenko P. Equilibria between titanium metal and solutions of titanium dichloride in fused magnesium chloride. J. Electrochem. Soc., 1958, 105(4): 210.

[15] Norman FHB, Wurm JG. Some new fluoride complexes of trivalent titanium. Can. J. Chem., 1958, 36(4): 615.

[16] Clayton FR, Mamantov G, Manning DL. Electrochemical studies of titanium in molten fluorides. J. Electrochem. Soc., 1973, 120(9): 1193.

[17] Robin A, De Lepinay J. Determination of the apparent standard potential of the Ti/Ti(III) system in the LiF-NaF-KF eutectic using voltammetry, chronopotentiometry and open-circuit potentiometry. Electrochm. Acta, 1991, 36(5–6): 1009.

[18] Robin A. Behavior of titanium electrocoatings on nickel in fluoride melts. Mater. Lett., 1998, 34(3–6): 196.

[19] Robin A. Influence of temperature on the reduction mechanism of Ti(III) ions on iron in the LiF-NaF-KF eutectic melt and on the electrochemical behavior of the resultant titanium coatings. Mater. Chem. Phys., 2005, 89(2–3): 438.

[20] Ene N, Zuca S. Role of free F-anions in the electrorefining of titanium in molten alkali halide mixtures. J. Appl. Electrochem., 1995, 25(7): 671.

[21] Sequeira CAC. Chronopotentiometric study of titanium in molten NaCl + KCl + K₂TiF₆. J. Electroanal. Ghem. Interfacial Electrochem., 1988, 239(1–2): 203.

[22] Chen GS, Okido M, Oki T. Electrochemical studies of titanium in fluoride-chloride molten salts. J. Appl. Electrochem., 1988, 18(1): 80.

[23] Wang QY, Song JX, Hu GJ, Zhu XB, Hou JG, Jiao SQ, Zhu HM. The equilibrium between titanium ions and titanium metal in NaCl-KCl equimolar molten salt. Metall. Mater. Trans. B, 2013, 44(4): 906.

[24] Sekimoto H, Nose Y, Uda T, Sugimura H. Quantitative analysis of titanium ions in the equilibrium with metallic titanium in NaCl-KCl equimolar molten salt. Mater. Trans., 2010, 51(11): 2121.

[25] Song JX, Hu GJ, Wang QY, Zhu XB, Jiao SQ, Zhu HM. Preparation of high-purity titanium by electrorefining in NaCl-KCl melt. The 4th Asian Conference on Molten Salts and Ionic Liquids, Sendai, 2012 120