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Titanium (Ti) is produced by a multi-step process from Ti ore composed of Ti oxide including chlorination process. However, the smelting cost is a major factor that leads to an increase in the cost of Ti. To lower the cost of Ti, the development of a new technique for the direct production of metallic Ti from an oxide feed material is highly desired. However, owing to the high affinity between Ti and oxygen (O) and the high solubility of O in Ti, it is extremely difficult to produce metallic Ti with low O concentration which meets the level required by the industry. In this study, we developed a new method for producing Ti with a low O concentration directly from TiO2 by using Mg as a reductant, assisted by a rare earth oxychloride formation reaction. The production of Ti with a low O concentration was demonstrated using a magnesiothermic reduction of TiO2 in MgCl2–LaCl3 molten salt via a reduction reaction involving LaOCl formation: (TiO2 (s) + 2 Mg (l) + 2 LaCl3 (l) = Ti (s) + 2 MgCl2 (l) + 2 LaOCl (s)). An electrochemical method that produces metallic Ti from TiO2 with no consumption of rare earth elements and Mg was designed based on the experiment results. This process is expected to replace the current smelting processes of Ti as well as numerous other rare metals produced from raw oxide materials and contribute significantly to a decrease in the price of rare metals.

This paper presents a brief review of the history of titanium smelting and the current trends in related research and development. Presently, both electrolytic and metallothermic reduction processes utilizing various feed materials such as titanium oxide are widely studied. However, many challenges remain to be addressed before realizing the practical application of smelting processes utilizing oxide feed. To make titanium a “common metal”, a new reduction process that is high speed, energy-efficient, low cost, and of low environmental impact is required. The current status of titanium recycling is likewise outlined, and the development of the recycling process is discussed. Low-grade titanium scraps heavily contaminated by oxygen and iron are currently used for producing additive alloys (ferro-titanium) in the steel industry. In the near future, if the demand for titanium metal increases dramatically, there could be an oversupply of low-grade titanium scraps in the market. Therefore, the development of anti-contamination and efficient removal processes for oxygen and iron is essential for the efficient utilization of titanium. The development of these technologies is vital for expanding the titanium industry through innovation in both titanium smelting and recycling technologies.

The development of a new titanium (Ti) smelting process is highly desired to decrease the cost of Ti metal. In this study, a new method to produce a low-oxygen-concentration Ti directly from TiO2 using La as the reductant was developed. First, deoxidation experiments of metallic Ti using La as the deoxidant were conducted, and the ability of La to deoxidize metallic Ti was demonstrated. The oxygen concentrations in Ti were approximately 3900 ± 400 mass ppm O and 120 ± 50 mass ppm O at La/La2O3 and La/LaOCl/LaCl3 equilibria, respectively, at 1200 K (927 °C). Then, TiO2 reduction experiments utilizing La as the reductant were conducted to produce low-oxygen-concentration Ti directly. TiO2 pellets and Ti pieces were held in LaCl3 molten salt with a sufficient amount of La at 1200 K (927 °C) for 86 ks. After the reaction, the TiO2 pellets were reduced to metallic Ti without reaction inhibition by the formation of intermediate products. The oxygen concentration of the Ti pieces, which were placed in the molten salt with the TiO2 pellets, was 100 ± 50 mass ppm O. These results indicate that low-oxygen-concentration Ti containing less than 200 mass ppm O could be produced directly from TiO2 by utilizing La as the reductant in LaCl3 molten salt at 1200 K (927 °C). This new method is expected to lead to the development of a new industrial process for the production of ultra-low-oxygen-content Ti from Ti ore without a chlorination process.

Deoxidation methods of titanium (Ti) scrap and Ti powder have become increasingly important in recent years. Some rare earth (RE) metals with strong deoxidizing capabilities, including Y, La, Ce, and Ho, are candidate agents for the development of a new deoxidation technology. In this study, a new method was developed to directly remove oxygen (O) from Ti using the Y/YOCl/YCl3 equilibrium. According to the calculation based on available thermodynamic data in the literature, the O concentration in β-Ti can be reduced to less than 10 ppm O at 1300 K (1027 °C) in the Y/YOCl/YCl3 equilibrium. To demonstrate the effectiveness of this method using the Y/YOCl/YCl3 equilibrium, the deoxidation limits of Ti samples using Y metal in YCl3 (l) or in YCl3-NaCl-KCl (l) at 1300 K (1027 °C) were experimentally investigated in this study. As a result, the O concentrations in the Ti samples were from 30 to 60 ppm O in YCl3 (l). This result revealed that Ti with extremely low O concentration can be reliably obtained using the RE/REOCl/RECl3 equilibrium for the first time. The establishment of this process will realize efficient recycling of Ti scrap and production of low O concentration Ti powder, which contribute to the large-scale use of Ti products.

A new electrochemical deoxidation process for Ti, where a mixture of magnesium chloride and yttrium chloride (MgCl2–YCl3) is used as flux, was developed. In the new process, Ti and carbon were used as the cathode and anode, respectively. By elucidating the system using an E-pO2− diagram and the experimental results, the reaction mechanism was proposed. Mg is deposited on the Ti cathode and reduces the oxygen in Ti to oxide ions (O2−). The activity of the generated O2−, $$a_{\text O^{2-}}$$ , in the system is effectively kept at a low level by the formation of yttrium oxychloride, and is further decreased by the electrochemical oxidation reaction on the anode. The process effectively deoxidizes Ti to the level of 100 mass ppm of oxygen concentration at 1200 K. In addition, the oxygen concentration in the Ti sample was maintained at the level of 500 mass ppm O even with the addition of O2− sources. Furthermore, a new concept of the industrial Ti-recycling process based on this new deoxidation process was depicted. The obtained results indicate that this new deoxidation technique can be applied in the recycling process of Ti scrap containing a large amount of oxygen.

To reduce the oxygen level in titanium (Ti) to less than 1000 mass ppm O, using magnesium as the deoxidant at 1300 K (1027 °C), the activity of the deoxidation product (MgO), i.e., aMgO, in the system must be reduced to less than 0.04, from a thermodynamic viewpoint. In this study, we developed a new deoxidation technique for Ti, by adding yttrium chloride (YCl3) to magnesium chloride (MgCl2) flux, which effectively decreases and maintains the aMgO in the system at a low level, via the formation of yttrium oxychloride (YOCl). Through thermodynamic assessment using a $$ p_{{{\text{O}}_{ 2} }} {\text{-}}p_{{{\text{Cl}}_{ 2} }} $$ diagram, as well as experiments, the deoxidation of Ti to an oxygen level below 1000 mass ppm O, via the reaction O (in Ti) + Mg + YCl3 → MgCl2 + YOCl, was confirmed. Furthermore, using the E-pO2− diagram of the M-O-Cl system (M = Y, Mg), the possibility of electrochemical deoxidation is discussed. In the MgCl2-YCl3 flux, Mg deposits on the Ti cathode and simultaneously deoxidizes it. The activity of the deoxidation product, MgO, decreases due to the formation of YOCl and/or the electrochemical oxidation of oxide ions on the carbon anode; thus, the deoxidation of Ti becomes feasible. This new deoxidation technique using rare-earth-containing MgCl2 flux can be applied to the recycling of Ti scraps, in the future.

The electrochemical behavior of Te2- ions was investigated in the LiCl-Li2Te binary on glassy carbon electrodes at 650 °C as a means to understand the fundamental thermodynamic and mass transport properties of Te2- ions. Cyclic voltammetry and constant-potential electrolysis confirmed an electrochemically reversible, two-electron soluble-insoluble reaction of Te2-/Te(l). The formal potential for the Te2-/Te(l) reaction was determined to be 1.744 V vs Li+/Li(l), and the diffusivity of Te2- ions was about 0.44-1.25 × 10-5 cm2 s-1. The low value for diffusivity relative to those of other cations in molten salts suggests the possibility of forming complex ions such as [Li8Te]6+ due to strong chemical interactions with Li+ ions in the electrolyte. The anodic polarization of Te(l) indicated that the formation of TeCl2(g) and the cathodic polarization of Te(l) involved the codeposition of Li metal into the Te(l). The results of this work provide essential knowledge in developing electrochemical processes for separation of tellurium as well as in mitigating the degradation reactions with structural materials.

In the realm of stationary energy storage, a plurality of candidate chemistries continues to vie for acceptance, among them the Na–NiCl2 displacement battery, which has eluded widespread adoption owing to the fragility of the β″-Al2O3 membrane. Here we report a porous electronically conductive membrane, which achieves chemical selectivity by preferred faradaic reaction instead of by regulated ionic conduction. Fitted with a porous membrane of TiN, a displacement cell comprising a liquid Pb positive electrode, a liquid Li–Pb negative electrode and a molten-salt electrolyte of PbCl2 dissolved in LiCl–KCl eutectic was cycled at a current density of 150 mA cm−2 at a temperature of 410 °C and exhibited a coulombic efficiency of 92% and a round-trip energy efficiency of 71%. As an indication of industrial scalability, we show comparable performance in a cell fitted with a faradaic membrane fashioned out of porous metal. Molten-salt batteries such as Na–NiCl2 are promising candidates for grid storage, but suffer from fragility of ion-selective ceramic membranes. Here the authors report the operation of a Li–Pb||PbCl2 battery fitted with a robust TiN mesh membrane that functions by protective faradaic reaction.

Corrosion in grid-scale energy storage devices adversely affects service lifetime and thus has a significant economic impact on their deployment. In this work, we investigate the corrosion of steel and stainless steels (SSs) as positive current collectors in the Li||Sb-Pb liquid metal battery. The erosion and formation of new phases on low-carbon steel, SS301, and SS430 were evaluated both in static conditions and under cell operating conditions. The cell performance is not adversely affected by the dissolution of iron or chromium but rather nickel. Furthermore, the in situ formation of a Fe-Cr-Sb layer helps mitigate the recession of SS430.

A new electrochemical deoxidation method is proposed for Ti, wherein a mixture of magnesium chloride and holmium chloride (MgCl2-HoCl3) is used as a flux. In the new process, Ti and C are used as the cathode and anode, respectively. Mg is deposited on the Ti cathode, which reduces the O in Ti to oxide ions (O2). The activity of the generated O2- (aO2-) in the system was effectively maintained at a low level by the formation of holmium oxychloride (HoOCl) and further decreased by the electrochemical oxidation reaction on the anode. By applying a voltage of 3.0 V between the cathode and anode at 1173 K, Ti was effectively deoxidized to approximately 1000 mass ppm O. Based on the results, in this study, an electrochemical cell, that simultaneously deoxidize Ti scrap or powders and recover HoOCl, is designed.

A novel method for removing the oxygen (O) in titanium (Ti) is proposed and developed, wherein holmium (Ho) and holmium chloride (HoCl3) are used as a deoxidant and flux, respectively. The reduction of O concentration in Ti to a level of below 200 mass ppm O (even reaching 110 mass ppm O) through the formation reaction of holmium oxychloride (HoOCl), i.e., O (in Ti) + 2/3 Ho + 1/3 HoCl3 → HoOCl, was confirmed. This result reveals that deoxidation of Ti using Ho in HoCl3 flux is effective, and low-O Ti can be obtained under Ho/HoOCl/HoCl3 equilibrium. This new deoxidation technique using Ho as a deoxidant can be applied to the refining of Ti scraps and the production of low-O content Ti powder in the future. The standard Gibbs energy of formation of HoOCl (ΔG°f,HoOCl) at 1300 K was experimentally determined to be – 744 ± 10 kJ mol−1. In addition, the value of ΔG°f,Ho2O3 was determined to be – 1503 ± 10 kJ mol−1, which is in good agreement with the reported data (– 1510 kJ mol−1). A potential diagram of the Ho–Cl–O system at 1300 K was newly drawn using the thermodynamic data determined through this study.

In modern high-tech products, rare metals play an increasingly pivotal role. To support the development of a highly sustainable society, where valuable natural resources are not wasted and most materials are recycled, new efficient, environment-friendly recycling technologies for rare metals are required. The authors have developed environment-friendly recycling technologies that efficiently extract rare metals and precious metals from scrap without generating harmful waste solutions (waste liquids) and exhaust gases. These technologies include (1) a technique for converting contaminated titanium scrap, which is expected to increase in the future, into high-quality titanium feed material; (2) a technology for extracting and separating rare metals, such as rhenium, directly from end-of-life turbine blades used in aircraft and power stations without generating any waste aqueous solutions; and (3) a method for efficiently concentrating and separating platinum group metals in automobile catalytic converters without using harmful acids or other chemicals. These technologies will help establish an environment-friendly rare metal recycling system.

Recycling of precious metals is becoming increasingly important as our living standards improve and electronic technologies advance. Conventional recycling processes involve multi-step hydrometallurgical treatments, in which precious metals are dissolved in aqueous solutions using a combination of strong complexing agents and oxidizing agents. However, these processes are time consuming and produce a large amount of hazardous liquid waste. Here, we present a new recycling process for Au, which is based on the direct anodic electrochemical deposition of anionic Au ions dissolved in a molten salt electrolyte. Moreover, this process is simple and does not generate harmful waste. In this process, Au is alloyed with Na to facilitate its dissolution in a molten mixture of NaCl–NaI. The existence of Au as an anionic species (Au n−) in the molten salt was proven and its anodic deposition (oxidation reaction) by application of an anodic current was demonstrated. During the anodic deposition of Au, Na is deposited on the cathode and can be recovered and reused in the process. It is expected that this electrodeposition technique to recycle Au from scrap metal could result in the development of a new environmentally friendly Au recycling process that does not generate hazardous waste.

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-YCl3flux at 1,200 K. This new deoxidation method is considered applicable to the recycling process of Ti scrap containing large amounts of oxygen.

The performance of a calcium-antimony (Ca-Sb) alloy serving as the positive electrode in a Ca∥Sb liquid metal battery was investigated in an electrochemical cell, Ca(in Bi) | LiCl-NaCl-CaCl[subscript 2] | Ca(in Sb). The equilibrium potential of the Ca-Sb electrode was found to lie on the interval, 1.2–0.95 V versus Ca, in good agreement with electromotive force (emf) measurements in the literature. During both alloying and dealloying of Ca at the Sb electrode, the charge transfer and mass transport at the interface are facile enough that the electrode potential varies linearly from 0.95 to 0.75 V vs Ca(s) as current density varies from 50 to 500 mA cm[superscript −2]. The discharge capacity of the Ca∥Sb cells increases as the operating temperature increases due to the higher solubility and diffusivity of Ca in Sb. The cell was successfully cycled with high coulombic efficiency (∼100%) and small fade rate (, United States. Advanced Research Projects Agency-Energy (Award DE-AR0000047), TOTAL (Firm), Marubun Research Promotion Foundation, Murata Overseas Scholarship Foundation

Calcium is an attractive electrode material for use in grid-scale electrochemical energy storage due to its low electronegativity, earth abundance, and low cost. The feasibility of combining a liquid Ca-Bi positive electrode with a molten salt electrolyte for use in liquid metal batteries at 500-700 degrees C was investigated. Exhibiting excellent reversibility up to current densities of 200 mA cm(-2), the calcium bismuth liquid alloy system is a promising positive electrode candidate for liquid metal batteries. The measurement of low self-discharge current suggests that the solubility of calcium metal in molten salt electrolytes can be sufficiently suppressed to yield high coulombic efficiencies >98%. The mechanisms giving rise to Ca-Bi electrode overpotentials were investigated in terms of associated charge transfer and mass transport resistances. The formation of low density Ca11Bi10 intermetallics at the electrode electrolyte interface limited the calcium deposition rate capability of the electrodes; however, the co-deposition of barium into bismuth from barium-containing molten salts suppressed Ca-Bi intermetallic formation thereby improving the discharge capacity. (C) 2013 Elsevier B.V. All rights reserved.

This paper described characterization of hydrazine adsorption on Cu surface with high-selectivity of component at right angle down to single molecular level using a plasmonic antenna enhancing Raman scattering. The antenna deposited by Cu with concentric pattern was designed by Finite Difference Time Domain (FDTD) calculation to enhance the electric field by focusing surface plasmon. By using this antenna, Raman peaks of adsorbed hydrazine on Cu was provided at 385 cm−1. Furthermore, these peaks were only observed at 1–2 nm from the antenna surface which meant that this approach had a potential to define the structure of adsorbed hydrazine just only on the plasmon antenna. The structure of adsorbed hydrazine was gauche-conformation. This data corresponded to the Density Functional Theory (DFT) of adsorption model of hydrazine on fcc-Cu (1 1 1) surface. These results suggest that this method creates a wide range of spin-off effects to the characterization of solid–liquid interface.

Calcium is an attractive material for the negative electrode in a rechargeable battery due to its low electronegativity (high cell voltage), double valence, earth abundance and low cost; however, the use of calcium has historically eluded researchers due to its high melting temperature, high reactivity and unfavorably high solubility in molten salts. Here we demonstrate a long-cycle-life calcium-metal-based rechargeable battery for grid-scale energy storage. By deploying a multi-cation binary electrolyte in concert with an alloyed negative electrode, calcium solubility in the electrolyte is suppressed and operating temperature is reduced. These chemical mitigation strategies also engage another element in energy storage reactions resulting in a multi-element battery. These initial results demonstrate how the synergistic effects of deploying multiple chemical mitigation strategies coupled with the relaxation of the requirement of a single itinerant ion can unlock calcium-based chemistries and produce a battery with enhanced performance., United States. Advanced Research Projects Agency-Energy, TOTAL (Firm)