A study of the electrochemical behavior of the Ti(IV)/Ti(III) redox couple in the NaCl-KCl-NaF-K2TiF6 melt in order to optimize the electrorefining of titanium and synthesis of alloys based on this metal

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The electrochemical behavior of the Ti(IV)/Ti(III) redox couple in the CsCl-CsF(10 wt.%)-K2TiF6 melt was studied by cyclic voltammetry. The diffusion coefficients of the Ti(IV) complexes were calculated using the Randles-Sevcik equation. The standard rate constants of charge transfer for the Ti(IV)/Ti(III) redox couple in the CsCl-CsF(10 wt.%)-K2TiF6 melt without and with additions of alkaline earth metal cations (Mg2+, Ca2+, Sr2+, Ba2+) were determined. It was found that the rate constants of charge transfer increase with increasing ionic potential of the addition, reaching a maximum value for complexes with outer-sphere cations of magnesium, and this dependence is rectilinear. The activation energies of the charge transfer process in melts with additions of alkaline earth metal cations were calculated and these values are significantly lower than the activation energy of the initial system CsCl-CsF(10 wt %)-K2TiF6. The kinetic parameters of the Ti(IV)/Ti(III) redox couple in chloride-fluoride melts with different second coordination sphere composition of the complexes were compared.

mentioning

confidence: 99%

mentioning

confidence: 99%

Charge Transfer Kinetics of the Ti(IV)/Ti(III) Redox Couple in the Cesium Chloride-Cesium Fluoride Melt with Addition of Alkaline Earth Metal Cations

Vetrova¹,

Kuznetsov²

2023

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“…The electrochemical behavior of titanium in chloride and chloride-fluoride melts was the goal of numerous studies. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In works [5][6][7][8][9][10][11] the electrochemical properties of TiCl 4 were studied in NaCl-KCl, 6,8 KCl-LiCl, 5,7,9 LiCl-CsCl 8 and NaCl-CsCl 10 melt. It was shown 5,8 that the electroreduction of Ti(IV) chloride complexes to the metal occurs in three stages: Ti(IV) → Ti(III) → Ti(II) → Ti.…”

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confidence: 99%

Electrochemical Behavior of Titanium Complexes in the KCl-KF Melt with Additions of Alkaline Earth Metal Cations

Vetrova

Kuznetsov

2021

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The charge transfer kinetics for the Ti(IV)/Ti(III) redox couple in the KCl-KF(10 wt.%)-K2TiF6 melt was studied. The standard rate constants of charge transfer (k s ) for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt were calculated. The temperature dependence of the standard rate constants of charge transfer was described by the empirical equation: logk s = (2.01 ± 0.40) – (4178 ± 810)/Т. The activation energy of charge transfer was equal to (80 ± 15) kJ mol–1. Influence of strongly polarizing cations (Mg2+, Ca2+, Sr2+ and Ва2+) on the charge transfer kinetics was studied. It was determined the linear dependence of k s on the ionic potential of alkaline earth metal cations. Values of activation energy of charge transfer for systems with strongly polarizing cations were considerably less than activation energy of the initial system and decrease in case of ionic potential increasing.

“…4 Nevertheless, to obtain high-purity titanium a necessary step is the process of its purification from various impurities. 5 An effective method of purifying titanium is electrorefining in molten salts. 6 In turn, to optimize the process of electrolytic titanium refining, complete information about the transport and kinetic properties of titanium complexes in various molten salts is necessary.…”

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confidence: 99%

“…7 In this regard, studies of the electrochemical behavior of titanium complexes are of undoubted interest. [5][6][7][8][9][10][11][12][13][14][15][16][17][18] At the same time, the presence of alkaline earth metal cations in molten alkali metal halides leads to significant changes in the kinetic and transport properties of titanium containing melts. [19][20][21] To monitor such changes, it is advisable to use quantum-chemical simulations.…”

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confidence: 99%

Study of the Electron Transfer in Titanium Containing Melts by Electrochemical and Quantum-Chemical Methods

Stulov

Vetrova

Kremenetsky

et al. 2021

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The electron transfer mechanism in a titanium containing system was investigated by electrochemical and quantum-chemical methods. The kinetics of charge transfer for the Ti(IV)/Ti(III) redox couple in the (NaCl–KCl)equimol–NaF (10 wt%)-K2TiF6 melt with addition of Ca2+ cations was studied by cyclic voltammetry. The standard rate constants of charge transfer (k s ) were calculated by Nicholson’s method. The increase values of the k s reaching the maximum at mole ratio Ca2+/Ti(IV) equals 1:1 was found. Values of activation energy for system with Ca2+ cations are considerably less than activation energies of the system without Ca2+ cations. The quantum-chemical calculations were performed using the Firefly quantum-chemical package by methods of the density functional theory. Structures with a high probability of the electron transfer from the cathode to the titanium complex were found. Using the Frontier molecular orbital method made it possible with a small amount of computer time to determine the structure of the transition state of the TiF6 2− complex. The calculated activation energy of the electron transfer was in a good agreement with experimentally determined value.