Thermodynamic Analysis of Deoxidation of Titanium Through the Formation of Rare-Earth Oxyfluorides

Okabe, Toru H.; Taninouchi, Yu Ki; Zheng, Chenyi

doi:10.1007/s11663-018-1386-5

Cited by 31 publications

(10 citation statements)

References 39 publications

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“…5) This can be explained as follows: The HoCl 3 was first produced in the system by the reaction shown in eq. (15). The Ti samples were then mixed with Mg and MgCl 2 HoCl 3 flux (or HoCl 3 flux) ( Table 4).…”

Section: Resultsmentioning

confidence: 99%

“…Ca, Y, and Ho) as deoxidants is also possible. As shown in Table 1, 5,9,14,15) Ca, Y, and Ho are candidates for use as deoxidants. For example, at 1173 K, the calculated deoxidation limit of Ca/CaO equilibrium is 320 mass ppm O, and that of Y/Y 2 O 3 and Ho/Ho 2 O 3 equilibrium are 130 mass ppm O and 260 mass ppm O, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…4,43) As shown in Fig. 1(e), the formation of oxyhalides of some rare earth elements in molten halide fluxes can be Table 1 Calculated partial pressure of O 2 and the theoretical O level in ¢-Ti under various equilibrium conditions at 1173 K. 5,9,14,15) Table 2 Solubility of oxide (MO x ) in molten chloride (MCl 2 ) at different temperatures, C MOx (mol%). 31,38) Fig .…”

Section: Introductionmentioning

confidence: 99%

“…Table 3 lists the standard Gibbs energies of formation (¦G°f ,i ) of some compounds in MOCl (M = Ho, Y, La, Mg, and Ca) systems used in this study. 14,15,51,52) The standard Gibbs energy of O dissolution in ¢-Ti (¦G°1 ,Ti ) was also listed. 19) The reliability of the reported thermodynamic data for rare earth compounds is often low, especially for MOCl because of the limited research on the MOCl.…”

Section: Introductionmentioning

confidence: 99%

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Direct Deoxidation of Ti by Mg in MgCl2–HoCl3 Flux

2019

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A new method for removing the dissolved oxygen (O) in titanium (Ti) is developed, wherein magnesium chlorideholmium chloride (MgCl 2 HoCl 3) and Mg are used as a flux and a reducing agent, respectively. Through the thermodynamic assessment using a p O2 p Cl2 diagram as well as the experimental results, the deoxidation of Ti to a level below 1000 mass ppm O (and even 500 mass ppm O) via the formation reaction of holmium oxychloride (HoOCl), O (in Ti) + Mg + HoCl 3 ¼ HoOCl + MgCl 2 , was confirmed. The deoxidation limit decreases with the increase of the activity of HoCl 3 in the MgCl 2 HoCl 3 flux. One advantage of this method is that the activity of the deoxidized product, a MgO , in the system can be effectively maintained at a low level by the formation of HoOCl. The EpO 2¹ diagram of the MOCl system (M = Ho, Mg) constructed in this study indicates that the electrochemical deoxidation of Ti scraps in MgCl 2 HoCl 3 system will be more effective because the a MgO can be further decreased via the formation of HoOCl, and/or the electrochemical oxidation of oxide ions on the carbon anode. This new deoxidation technique using rare-earth-containing MgCl 2 flux can be applied to the recycling of Ti scraps in the future.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Direct Deoxidation of Ti by Mg in MgCl2–HoCl3 Flux

2019

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“…Figure 2 shows the oxygen concentration in Ti, [O] Ti , in the equilibrium of several metals and their oxides or oxychlorides as a function of temperature calculated using available thermodynamic data [4,19]. In our recent studies, based on thermodynamic estimations, we proposed that Ti with an extra-low oxygen concentration can be obtained using RE halides as a flux by forming rare-earth oxyhalides (REOXs; X: F, Cl) owing to their high thermodynamic stabilities [8,9]. For instance, when Ti is deoxidized using yttrium (Y) as the deoxidant in an yttrium chloride (YCl 3 ) flux, the system is in Y/YOCl/YCl 3 equilibrium.…”

Section: Introductionmentioning

confidence: 99%

Development of Method for Direct Deoxidation of Titanium using Mixtures of Magnesium Chloride and Rare-Earth Chlorides

et al. 2020

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To decrease the cost of Ti sponge, Ti scrap is added during the remelting process to produce an ingot. However, the use of Ti scrap as an additive during this process is limited because Ti scrap is contaminated by oxygen (O) and iron (Fe), which are not removable during the remelting process. Here we introduce a new electrochemical deoxidation process for Ti scrap using a mixture of magnesium chloride (MgCl2) and rare-earth chlorides (RECl3, RE: Y and Ho) as a flux. Ti and carbon were used as the cathode and anode, respectively. Mg is deposited on the Ti cathode and reduces the oxygen in the Ti to oxide ions (O2). The activity of the generated O2” in the system, aQi-, is maintained at a low level through the formation of rare-earth oxy chloride (REOCl), and is further decreased by the formation of carbon oxides on the anode. During this process, the concentration of oxygen in the Ti is effectively decreased to 100 mass ppm in the MgCl2-YCl3 flux at 1,200 K. This new deoxidation method is considered applicable to the recycling process of Ti scrap containing large amounts of oxygen.

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Recycling of Critical Metals

Okabe

Ouchi

2019

The Minerals, Metals &Amp; Materials Series

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Thermodynamic Analysis of Deoxidation of Titanium Through the Formation of Rare-Earth Oxyfluorides

Cited by 31 publications

References 39 publications

Direct Deoxidation of Ti by Mg in MgCl<sub>2</sub>–HoCl<sub>3</sub> Flux

Direct Deoxidation of Ti by Mg in MgCl<sub>2</sub>–HoCl<sub>3</sub> Flux

Development of Method for Direct Deoxidation of Titanium using Mixtures of Magnesium Chloride and Rare-Earth Chlorides

Recycling of Critical Metals

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