Electrochemistry of Titanium in Molten 2AlCl3 ‐ NaCl

Stafford, Gery R.; Moffat, Thomas P.

doi:10.1149/1.2049976

Cited by 38 publications

(45 citation statements)

References 10 publications

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“…This behavior is a common feature of overpotential alloy deposition in chloroaluminate melts and was observed during the electrodeposition of Al-Cr 20,21 Al-Mn, 23,44 Al-Mo, 45 and Al-Ti. 24,25,39,46 The finding that plating solutions containing Zr͑IV͒ lead to alloys with higher Zr content than plating solutions containing equal concentrations of Zr͑II͒ may be reconciled by considering the diffusion coefficient data in Table I. Because the concentration-dependent diffusion coefficient for Zr͑II͒ is only a small fraction of that for Zr͑IV͒, the observed inefficiency of Zr͑II͒ for plating Al-Zr alloys must be directly related to the mass-transport limitations imposed by the diminutive diffusion coefficient of the latter species.…”

Section: Resultsmentioning

confidence: 99%

“…For Ti͑II͒, this phenomenon is attributed to polymerization of the Ti͑II͒ species as ͓Ti͑AlCl 4 ) 2 ] m , with m increasing as the Ti͑II͒ concentration is increased. 25,39,42,43 Given the overall similarity of the chemistry of Ti͑II͒ and Zr͑II͒, polymerization of Zr͑II͒ is also expected. The observed concentration dependence of E 1/2 for the first Zr͑II͒ oxidation waves, but not the second waves, in Fig.…”

Section: Resultsmentioning

confidence: 99%

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Electrodeposition of Al-Zr Alloys from Lewis Acidic Aluminum Chloride-1-Ethyl-3-methylimidazolium Chloride Melt

Tsuda

Hussey

Stafford

et al. 2004

J. Electrochem. Soc.

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The electrochemistry of Zr͑IV͒ and Zr͑II͒ and the electrodeposition of Al-Zr alloys were examined in the Lewis acidic 66.7-33.3 mol % aluminum chloride-1-ethyl-3-methylimidazolium chloride molten salt at 353 K. The electrochemical reduction of Zr͑IV͒ to Zr͑II͒ is complicated by the precipitation of ZrCl 3 ; however, solutions of Zr͑II͒ can be prepared by reducing Zr͑IV͒ with Al wire. Al-Zr alloys can be electrodeposited from plating baths containing either Zr͑IV͒ or Zr͑II͒, but for a given concentration and current density, baths containing Zr͑IV͒ lead to Al-Zr alloys with the higher Zr content. This result was traced to the diminutive concentration-dependent diffusion coefficient for Zr͑II͒. It was possible to prepare Al-Zr alloys containing up to ϳ17% atomic fraction ͑atom %͒ Zr. The structure of these deposits depended on the Zr content. Alloys containing less than 5 atom % Zr could be indexed to a disordered face-centered cubic structure similar to pure Al, whereas alloys containing ϳ17 atom % Zr were completely amorphous ͑metallic glass͒. The chloride pitting potentials of alloys with more than 8 atom % Zr were approximately ϩ0.3 V relative to pure Al.The maximum solubility of zirconium in face-centered cubic ͑fcc͒ aluminum is 0.08% atomic fraction ͑atom %͒. This occurs at the peritectic transformation point at 660.5°C. At room temperature, zirconium has negligible solubility in aluminum. 1 However like most aluminum-transition metal alloys, supersaturated solid solutions greatly exceeding the equilibrium solubility can be obtained by nonequilibrium processing methods. For example, solid solutions containing up to 3.0 atom % zirconium have been produced by rapid solidification 2-6 and vapor deposition. 7 The Al-Zr solid solution, although metastable, shows good thermal stability up to ϳ400-450°C. This observation is consistent with the general trend that the thermal stability of the solid solution is related to the melting point of the alloying addition; i.e., the higher the melting point, the more stable the solid solution. 8 The thermal decomposition of the supersaturated solid solution results in the nucleation of a metastable Al 3 Zr phase having an ordered cubic L1 2 structure (Cu 3 Au-type͒ 5,6,9-13 and eventually the equilibrium Al 3 Zr phase having a tetragonal structure. These two phases, cubic Al 3 Zr and tetragonal Al 3 Zr, have also been observed in supersaturated Al-Zr solid solutions produced by rapid quenching. 14 The properties of aluminum and its alloys are significantly altered by the addition of zirconium. The rapid solidification of binary Al-Zr alloys with more than 0.15 atom % zirconium produces considerable grain refinement, 15,16 resulting in aluminum grain sizes typically less than 10 m. The general explanation for this phenomenon is that L1 2 Al 3 Zr acts as a low-energy nucleation site for fcc Al due to the similar crystal structures. Rapid quenching is required to ensure that the Al 3 Zr solidifies with the metastable L1 2 structure rather than the equilibrium tetragonal structure...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Electrodeposition of Al-Zr Alloys from Lewis Acidic Aluminum Chloride-1-Ethyl-3-methylimidazolium Chloride Melt

Tsuda

Hussey

Stafford

et al. 2004

J. Electrochem. Soc.

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“…Ti (IV) first reduced to Ti (III) and then subsequently reduced to Ti (II). However, other studies [9,10,12] showed that, when the concentration of Ti (III), i.e., b-TiCl 3 , exceeded the solubility limit, then Ti (III) was passivated on the electrode surface and was also precipitated. This passive film blocks the electrodes and prevents oxidation and reduction.…”

Section: Introductionmentioning

confidence: 99%

“…The electrochemical behavior of titanium in Lewis acidic chloroaluminate melt was investigated. [10][11][12][13][14][15] The electrochemistry of TiCl 4 in strongly Lewis acid molten salt (AlCl 3 -EtMelmCl) at room temperature was reported by Carlin et al [13] It was found that the reduction of tetravalent titanium Ti (IV) occurs in two one-electron steps. Ti (IV) first reduced to Ti (III) and then subsequently reduced to Ti (II).…”

Section: Introductionmentioning

confidence: 99%

Low-Temperature Production of Ti-Al Alloys Using Ionic Liquid Electrolytes: Effect of Process Variables on Current Density, Current Efficiency, and Deposit Morphology

Pradhan

Reddy

Lahiri

2009

Metall Mater Trans B

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Application of novel low-temperature ionic liquid electrolytes for the extraction of Ti-Al alloys was investigated. The study was focused on the production of Ti-Al alloys from AlCl 3 -1-butyl-3-methyl imidazolium chloride (BmimCl) (molar ratio of AlCl 3 and BmimCl is 2:1) at different temperatures between 70°C and 125°C ± 3°C. The Ti-Al alloys were deposited on titanium sheet (>99.9 wt pct) cathodes at various voltages between 1.5 and 3.0 V. Titanium sheet was used as the anode and its dissolution served the source of Ti ion in the electrolyte. Morphology and composition of deposited Ti-Al alloys were investigated using a scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS) and an inductively coupled plasmaoptical emission spectrometer (ICP-OES). The phase analysis was carried out using X-ray diffraction (XRD). This study was focused to determine the effect of process variables such as applied voltage and temperature on cathode current density, current efficiency, composition, and morphology of Ti-Al alloys. The Ti-Al alloys containing about 13 to 25 atom pct Ti were produced with a current efficiency of about 79 to 87 pct. This study shows that uniform and fine particle size with high titanium content Ti-Al alloy was obtained in the voltage range of 1.5 to 2.0 V and temperature between 70°C to 100°C.

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“…A three-step reduction of Ti 4+ to metal, Ti 4+ → Ti 3+ → Ti 2+ → Ti, is well known as the reduction mechanism [2][3][4][5][6][7][8][9]. The current efficiency was low, while sludge formation occurred.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical dissolution behavior of conductive TiCxO1–x solid solutions

Jiao

Ning

Huang

et al. 2010

Pure and Applied Chemistry

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Conductive TiC x O 1-x solid solutions were prepared by carbothermic reduction of titanium dioxide. Studies were focused on the possibility of electrochemically dissolving TiC x O 1-x in NaCl-KCl molten salt. The tail-gas from the anode was monitored during the electrolysis. It was discovered that carbon monoxide (CO) or carbon dioxide (CO 2 ) gases were generated, with the process being dependent upon the consumption of the TiC x O 1-x solid solution anode materials. Furthermore, a series of electrochemical methods was used to investigate the valence state of titanium ions dissolved into molten salt when electrolyzing TiC x O 1-x solid solutions. A significant result was that titanium ion species dissolved from the TiC x O 1-x solid solutions, and this is changed between Ti 2+ and Ti 3+ depending on the electrochemically dissolving potentials. The significant result discovered in this paper will be potentially beneficial in the preparation of high-purity titanium by electrorefining TiC x O 1-x solid solutions.

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Electrochemistry of Titanium in Molten 2AlCl3 ‐ NaCl

Cited by 38 publications

References 10 publications

Electrodeposition of Al-Zr Alloys from Lewis Acidic Aluminum Chloride-1-Ethyl-3-methylimidazolium Chloride Melt

Electrodeposition of Al-Zr Alloys from Lewis Acidic Aluminum Chloride-1-Ethyl-3-methylimidazolium Chloride Melt

Low-Temperature Production of Ti-Al Alloys Using Ionic Liquid Electrolytes: Effect of Process Variables on Current Density, Current Efficiency, and Deposit Morphology

Electrochemical dissolution behavior of conductive TiCxO1–x solid solutions

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