Materials Transactions Online

Materials Transactions, Vol.61 No.10 (2020) pp.1967-1973
© 2020 The Japan Institute of Metals and Materials

Yttriothermic Reduction of TiO2 in Molten Salts

Takara Tanaka1, 2, Takanari Ouchi1 and Toru H. Okabe1

1Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505, Japan
2Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan

A new reduction process for producing titanium (Ti) with an ultra-low oxygen concentration directly from TiO2, employing yttrium (Y) as the reductant, was developed in this study. Several methods for the direct reduction of TiO2 have been proposed to lower the cost of production of Ti. However, none of them have yet been applied industrially. In addition, Y has never been used as a reductant for reducing TiO2 although its reducing ability is the highest among the reductants capable of reducing TiO2 to Ti with low oxygen concentration. In this study, the reduction reactions of TiO2 using Y/Y2O3 equilibrium and Y/YOCl/YCl3 equilibrium, employing various molten salts as solvents, were investigated. TiO2 pellets and metallic Ti pieces were placed in several types of solvents along with sufficient Y and heated at 1300 K for 86 ks. When YCl3 or CaCl2 was used as the solvent, the TiO2 pellets were reduced to metallic Ti. The oxygen concentrations in the Ti pieces after heating in YCl3 and CaCl2 were 90 ± 40 mass ppm O and 350 ± 60 mass ppm O, respectively. However, when NaCl or KCl was used as the solvent, a small amount of metallic Ti and a large amount of complex oxides were obtained. It is considered that the reduction reaction did not proceed sufficiently owing to the low solubility of the oxide ions in molten salts. It was experimentally demonstrated that Ti with an ultra-low oxygen concentration (100 mass ppm O or less) can be directly produced from TiO2 by using Y as the reductant in an appropriate solvent. This method is expected to lead to the development of a new industrial process for the production of Ti with an ultra-low oxygen concentration directly from its ore.


(Received 2020/04/14; Accepted 2020/07/30; Published 2020/09/25)

Keywords: direct reduction, molten salt, thermodynamics, yttrium, titanium dioxide, titanium

PDF(member)PDF (member) PDF(organization)PDF (organization) Order DocumentOrder Document Table of ContentsTable of Contents


  1. Kubaschewski O. and Dench W.A.: J. Inst. Met. 82 (1953-1954) 87-91.
  2. K.L. Komarek and M. Silver: Proc. IAEA Symp., (Thermodynamics of Nuclear Materials, 1962) pp. 749-774.
  3. T.H. Okabe, K.T. Jacob and Y. Waseda: Purification Process and Characterization of Ultra High Purity Metals, (Springer, Berlin, Heidelberg, 2002) pp. 3-37.
  4. Okabe T.H., Zheng C. and Taninouchi Y.: Metall. Mater. Trans. B 49 (2018) 1056-1066.
  5. Okabe T.H., Taninouchi Y. and Zheng C.: Metall. Mater. Trans. B 49 (2018) 3107-3117.
  6. I. Barin: Thermochemical Data of Pure Substance, 3rd ed., (Wiley-VCH, Weinheim, Germany, 1995).
  7. O. Knacke, O. Kubaschewski and K. Hesselmann: Thermochemical Properties of Inorganic Substances, 2nd ed., (Springer-Verlag, Berlin, Germany, 1991).
  8. Patrikeev Y.B., Novikov G.I. and Badovskii V.V.: Russian J. Phys. Chem. 47 (1973) 284.
  9. Okabe T.H., Suzuki R.O., Oishi T. and Ono K.: Mater. Trans., JIM 32 (1991) 485-488.
  10. Zheng C., Ouchi T., Iizuka A., Taninouchi Y. and Okabe T.H.: Metall. Mater. Trans. B 50 (2019) 622-631.
  11. T.H. Okabe: Extractive Metallurgy of Titanium, 1st ed., ed. by Z.Z. Fang, F.H. Froes and Y. Zhang, (Elsevier, Amsterdam, 2019) pp. 131-164.
  12. Zheng C., Ouchi T., Kong L., Taninouchi Y. and Okabe T.H.: Metall. Mater. Trans. B 50 (2019) 1652-1661.
  13. Kong L., Ouchi T. and Okabe T.H.: Mater. Trans. 60 (2019) 2059-2068.
  14. Kong L., Ouchi T., Zheng C. and Okabe T.H.: J. Electrochem. Soc. 166 (2019) E429-E437.
  15. Iizuka A., Ouchi T. and Okabe T.H.: Metall. Mater. Trans. B 51 (2020) 433-442.
  16. Tanaka T., Ouchi T. and Okabe T.H.: Metall. Mater. Trans. B 51 (2020) 1485-1494.
  17. Iizuka A., Ouchi T. and Okabe T.: Mater. Trans. 61 (2020) 758-765.
  18. Perkin F.M. and Pratt L.: Trans. Faraday Soc. 3 (1908) 179-186.
  19. Hasegawa M.: J. Jpn. Inst. Met. A 14 (1950) 23-26.
  20. Sibert M.E. and Steinberg M.A.: J. Met. 8 (1956) 1162-1168.
  21. Henrie T.A.: High Temperature Refractory Metals 34 (1968) 139-154.
  22. Oki T. and Inoue H.: Mem. Fac. Eng., Nagoya Univ. 19 (1967) 164-166.
  23. Hayes F.H., Bomberger H.B., Froes F.H., Kaufman L. and Burte H.M.: JOM 36(6) (1984) 70-76.
  24. Ono K. and Miyazaki S.: J. Japan Inst. Metals 49 (1985) 871-875.
  25. Ono K., Ogawa M., Okabe T.H. and Suzuki R.O.: Tetsu-to-Hagané 76 (1990) 568-575.
  26. T.H. Okabe: PhD thesis, Kyoto University, (1993) pp. 1-209.
  27. Okabe T.H., Oda T. and Mitsuda Y.: J. Alloy. Compd. 364 (2004) 156-163.
  28. Park I., Abiko T. and Okabe T.H.: J. Phys. Chem. Solids 66 (2005) 410-413.
  29. D.J. Fray, T.W. Farthing and G.Z. Chen: International Patent, WO1999064638A1 (1999).
  30. Chen G.Z., Fray D.J. and Farthing T.W.: Nature 407 (2000) 361-364.
  31. Fray D.J.: JOM 53(10) (2001) 27-31.
  32. Ono K. and Suzuki R.O.: Materia Japan 41 (2002) 28-31.
  33. Ono K. and Suzuki R.O.: JOM 54(2) (2002) 59-61.
  34. R.O. Suzuki and K. Ono: Electrochem. Soc., Proc., 2002-19, (2002) pp. 810-821.
  35. D.W. Rostron: US patent 2834667 (1958).
  36. J.M.J. Paixao, F.T.D. Almeida and M.J.D.F. Mourao: UK patent GB2158102A (1985).
  37. Maeda M., Yahata T., Mitugi K. and Ikeda T.: Mater. Trans., JIM 34 (1993) 599-603.
  38. Nersisyan H.H., Lee J.H. and Won C.W.: Mater. Res. Bull. 38 (2003) 1135-1146.
  39. Zhang Y., Fang Z.Z., Xia Y., Sun P., Devener B.V., Free M., Lefler H. and Zheng S.: Chem. Eng. J. 308 (2017) 299-310.
  40. Xia Y., Fang Z.Z., Zhang Y., Lefler H., Zhang T., Sun P. and Huang Z.: Mater. Trans. 58 (2017) 355-360.
  41. Vogel R.: Ferrum 14 (1917) 177-197.
  42. Gong W., Li D., Chen Z., Zheng F., Liu Y., Du Y. and Huang B.: Calphad 33 (2009) 624-627.
  43. J.L. Murray: Binary Alloy Phase Diagrams, II Ed., ed. by T.B. Massalski, (ASM International, Materials Park, OH, 1990) Vol. 3, pp. 3497-3499.
  44. Wyckoff R.W.G.: Crystal Structures 1 (1963) 239-444.
  45. Wyckoff R.W.G.: Crystal Structures 1 (1963) 7-83.
  46. Baldinozzi G., Berar J.F. and Calvarin G.: Mater. Sci. Forum 278-281 (1998) 680-685.
  47. Wenz D.J., Johnson I. and Wolson R.D.: J. Chem. Eng. Data 14 (1969) 250-252.
  48. T’en F.N. and Morozov I.S.: Russ. J. Inorg. Chem. 14 (1969) 1179-1183.
  49. Smirnov M.V. and Tkacheva O.Y.: Electrochim. Acta 37 (1992) 2681-2690.


© 2020 The Japan Institute of Metals and Materials
Comments to us :