title: The influence of fluoride ions on the equilibrium between titanium ions and titanium metal in fused alkali chloride melts.
abstract: KF is employed as a source of fluoride ions added to the melt to disclose the influence of fluoride on the disproportionation reactions of titanium ions, 3Ti(2+) = 2Ti(3+) + Ti, and 4Ti(3+) = 3Ti(4+) + Ti. The results reveal that the equilibrium transferred to the right direction for the first reaction and the apparent equilibrium constant increased sharply, mainly because of the formation of coordination compounds: TiFi(3-i). The accurate values of the equilibrium constants referring to the formation reactions of Ti(3+) + iF(-) = TiFi(3-i) (i = 1-6) in NaCl-KCl melt at 1023 K were evaluated with a best fit least squares method. It is also revealed that the stable states of the coordination compounds are TiF(2+), TiF2(+), TiF4(-) and TiF6(3-). Moreover, the Gibbs free energies for complex formation were estimated. Ti(2+) was undetectable when the concentration of fluoride ion was high enough. The equilibrium constant for the formation reaction, Ti(4-) + 6F(-) = TiF6(2-), was evaluated. The equilibrium constant, Kc2, for the disproportionation reaction 4Ti(3+) = 3Ti(4+) + Ti, in chloride melt was determined as 0.015.
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
authors.forename: Jianxun
authors.initials: J
authors.lastname: Song
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
authors.forename: Qiuyu
authors.initials: Q
authors.lastname: Wang
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing, 100083, China.
authors.forename: Shuqiang
authors.initials: S
authors.lastname: Jiao
authors.affiliation: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing, 100083, China and Department of Metallurgy, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan. hzhu@material.tohoku.ac.jp.
authors.forename: Hongmin
authors.initials: H
authors.lastname: Zhu