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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.

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.

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.

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)

This paper describes the fabrication process of CoPt nandot arrays on a glass disk substrate with a CoZrNb underlayer as a soft magnetic underlayer (SUL) by using an electrochemical process, and also the analysis on the magnetic properties of these fabricated CoPt nanodot arrays. We formed nano-patterned substrates by UV-nanoimprint lithography (UV-NIL) on the glass disk substrate. CoPt was electrodeposited into the nano-patterned substrates optimizing the electrodeposition condition and bath composition as well as a Cu intermediate layer. The construction of the nanodot arrays were CoPt nanodot arrays (20 nm)/Cu (5 nm)/CoZrNb (100 nm)/Cr (5 nm)/Glass disk. Magnetic signals were clearly observed on the dc magnetized state and multi domain were observed in each nanodot on the ac magnetized state by magnetic force microscopy (MFM). The perpendicular coercivity of the CoPt nanodot arrays was 430 kA/m. These results showed electrochemical process can be used for the manufacture of magnetic recording media.

To increase the areal density of hard disk drives (HDDs), discrete track media (DTM) and bit-patterned media (BPM) are being extensively studied. In the DTM and BPM, it is essential to isolate data tracks or bits. Unlike isolating the data tracks or bits using the conventional procedure involving physical etching, we attempted to isolate the tracks or bits with a soft guard band using an area-selective ion irradiation method. We prepared hard and soft (H/S) patterned films by nanoimprinting followed by ion irradiation. We confirmed the magnetic isolation of tracks and bits using magnetic force microscopy (MFM) images and magnetooptical Kerr effect (MOKE) signals. The results of an analysis of the magnetic properties of patterned coupled granular continuous (CGC) films with weak exchange coupling confirmed the validity of this novel approach for the fabrication of DTM and BPM.

The liquid metal battery (LMB) is attractive due to its simple construction, its circumvention of solid-state failure mechanisms and resultantly long lifetimes, and its particularly low levelized cost of energy. Here, we provide a study of a unique binary electrolyte, NaOH-NaI, in order to pursue a low-cost and low-temperature sodium-based liquid metal battery (LMB) for grid-scale electricity storage. Thermodynamic studies have confirmed a low eutectic melting temperature (220°C) as well as provided data to complete the phase diagram of this system. X-ray diffraction has further supported the existence of a recently discovered compound, Na[subscript 7](OH)[subscript 5]I[subscript 2], as well as offered initial evidence toward a NaI-rich compound displaying Pm-3m symmetry. These phase equilibrium data have then been used to optimize parameters from a two-sublattice thermodynamic solution model to provide a starting point for study of higher order systems. Further, a detailed electrochemical study has identified the voltage window and related oxidation/reduction reactions and found greatly improved stability of the pure sodium electrode against the electrolyte. Finally, an Na|NaOH-NaI|Pb-Bi proof-of-concept cell was assembled. This cell achieved over 100 cycles and displayed leakage currents below 0.40 mA/cm[superscript 2]. These results highlight an exciting class of low-melting molten salt electrolytes that may enable low cost grid-scale storage., United States. Advanced Research Projects Agency-Energy (Award DE-AR0000047), TOTAL (Firm), MIT Tata Center for Technology and Design

The electrochemical behavior of a ternary eutectic mixture of sodium amide (NaNH2), sodium hydroxide (NaOH) and sodium iodide (NaI) was investigated to elucidate its validity as an electrolyte for sodium-based liquid metal batteries. The liquid metal battery consists of two metals with different electronegativity separated by molten salt. The self-segregating nature of the three layers allows for easy assembly and scalability. Moreover, the all-liquid design allows the batteries to operate at high current densities with negligible losses because of the high conductivity of molten salts and fast transport properties in the liquid state. Sodium-based liquid metal batteries are particularly attractive due to the low cost of sodium metal (Na) and its low melting temperature (98°C). However, due to the high melting temperature of sodium halide salt (Tm > 500°C), the early efforts to build a sodium-based liquid metal battery faced the obstacle of high self-discharge and short life cycle.1 In our previous work, using a eutectic NaOH-NaI salt (Tm: 223°C), we demonstrated a Na||Bi-Pb cell operated at lower temperature ~250°C with small self-discharge. In order to further decrease operating temperature to less than 200 °C, in this work, we investigated a ternary eutectic 52%NaNH2,38%NaOH and 10%NaI (Tm: 127°C) 2. By using a three-electrode setup consisting of a liquid Na in β"-Al2O3 as a reference electrode, and tungsten wires as counter and working electrodes, cyclic voltammetry was performed at different scan rates (50, 100, and 200 mVs-1) and at 180 °C operating temperature. The electrochemical window of the ternary electrolyte was identified as 1.3 V with the sodium deposition as the cathodic limit and the oxidation of NH2 - anions to form N2H4gas as the anodic limit. Bismuth-lead (Bi-Pb) alloy is a candidate for positive electrode due to its low eutectic point (125 °C). Known thermodynamic properties of Na-Bi-Pb3 and previous work4 indicate that the operating voltage of the Na||Bi-Pb cell is expected to be within the electrochemical window of NaNH2-NaOH-NaI electrolyte. In this work, we focused on the discharge behavior of positive electrode, corresponding to the alloying process of Na in Bi-Pb alloy, in the ternary electrolyte. Using a similar three electrode setup utilizing liquid Na in β"-Al2O3 reference electrode, eutectic Bi-Pb working electrodes and a Na-Bi-Pb counter electrode, we obtained the voltage-time trace during alloying process and prepared the samples at varying Na concentration and current densities at 180°C operating temperature. The samples were quenched at target concentration of Na and cross-sectioned samples were analyzed using energy dispersive x-ray spectroscopy and scanning electron microscopy. We found that the Na preferentially alloys with Bi due to its stronger interaction than that with Pb (Pb works as diluent) and forms intermetallic, such as Na3Bi, similar to Li-Sb-Pb system 5 and Ca-Sb-Pb system.6 A smooth voltage profile on discharging to 10 at% of Na in the Bi-Pb electrode at 100 mAcm-2suggests potential feasibility of the ternary electrolyte for the sodium-based liquid metal batteries. References [1] A. D. Cairns, E.J. , Crouthamel, C.E. , Fischer, A.K. , Foster, M.S. , Hesson, J.C. , Johnson, C.E. , Shimotake, H. , Tevebaugh, “Galvanic cells with fused electrolytes,”, ANL-7316, Argonne National Laboratory, Chicago, 1967. [2] L. Heredy, “Fusible alkali-metal salt electrolyte,” US 3,472,745, 1969. [3] A. Petric, A. D. Pelton, M. L. Saboungi, W. F. Calaway, P. J. Tumidajski, A. Petric, J. C. Thompson, R. N. Singh, F. Sommer, B. P. Alblas, W. Van Der Lugt, M. Revere, M. P. Tosi, S. Tamaki, T. Ishiguro, and S. Takeda, “Dilute solutions of sodium in molten bismuth and tin : EMF measurements and interpretation,” J. Phys. F Met. Phys., 1983. [4] B. L. Spatocco, T. Ouchi, G. Lambotte, P. J. Burke, and D. R. Sadoway, “Low-Temperature Molten Salt Electrolytes for Membrane-Free Sodium Metal Batteries,” J. Electrochem. Soc., vol. 162, no. 14, pp. A2729–A2736, 2015. [5] K. Wang, K. Jiang, B. Chung, T. Ouchi, P. J. Burke, D. a. Boysen, D. J. Bradwell, H. Kim, U. Muecke, and D. R. Sadoway, “Lithium–antimony–lead liquid metal battery for grid-level energy storage,” Nature, vol. 514, no. 7522, pp. 348–350, 2014. [6] S. Poizeau and D. R. Sadoway, “Application of the Molecular Interaction Volume Model (MIVM) to Calcium-Based Liquid Alloys of Systems Forming High-Melting Intermetallics,” J. Am. Chem. Soc., vol. 135, no. 22, pp. 8260–8265, Jun. 2013.

As part of a comprehensive effort to develop a low-cost, grid-scale electrochemical energy storage device with low material cost with long cycle life, corrosion of the positive current collector (PCC) in a Li||Sb-Pb liquid metal battery (LMB) was investigated. A LMB consists of a low-density liquid negative electrode, an intermediate-density molten salt electrolyte, and a high-density liquid positive electrode, which self-segregate into three distinct liquid layers due to their immiscibility and density differences [1]. During discharge of the Li||Sb-Pb system, a liquid Li negative electrode is oxidized to form Li+ which is conducted through the electrolyte to a liquid Sb-Pb positive electrode where the Li+ is electrochemically reduced to a neutral Li and alloys with the Sb-Pb. This process is reversed on charging. The Li||Sb-Pb cells operate with high round trip efficiency (> 98 %) and wide capability of current density (> 1 A cm-2) at 450°C [1]; however, there is concern about the high reactivities of active materials and their potential for corrosion of cell components. Herein, we focused on the PCC. The Li||Sb-Pb cell configured with graphite PCC exhibited no corrosion and small decay of capacity, but in order to reduce costs of materials and large-scale manufacturing, in this study, commonly available steels or stainless steels were selected for the investigation due to their low cost, affordable machinability, and flexibility. We began with an evaluation of the corrosion of the steels by pure liquid Sb-Pb alloy representing the fully charged state of the Li||Sb-Pb cell. To the best of our knowledge, there has been no systematic investigation of the corrosion of metals in liquid Sb-Pb alloy; accordingly, thermodynamic evaluation of metals composing steels and stainless steels, such as iron (Fe), nickel (Ni), and chromium (Cr), equilibrated with liquid Sb-Pb alloy was the first step. Based on survays of phase diagrams, it was confimed that many kinds of metals dissolve in liquid Sb, Pb, and their alloys, and Fe, Ni, and Cr form intermetallic compounds with antimony. To evaluate the formation of intermetallics, static corrosion testing of pure Fe, Ni, and Cr was carried out. Test coupons were immersed in the liquid Sb-Pb alloys at constant temperature (450 ± 0.5 °C) and under Ar atmosphere (O2< 0.1 ppm). The cross-sections at the interfaces between coupons and Sb-Pb alloys after 500 h immersion are shown in Fig. 1. The layers of Fe-Sb, Ni-Sb, and Cr-Sb intermetallic alloys were observed in Fig. 1. Thicknesses of the layers were arranged as Ni > Fe > Cr. In order to elucidate the effects of concentration of Fe, Ni, and Cr in steel and stainless steels, a low-carbon steel (1018), a FeNiCr-based stainless steel (SS301), and a FeCr-based stainless steel (SS430) were selected for the investigation. Static corrosion tests of 1018, SS301, and SS430 in the liquid Sb-Pb alloy were performed and cross sections of coupons after 500 h immersion are shown in Fig. 2. On 1018 and SS301, layers of Fe-Sb alloy and Fe-Ni-Cr-Sb alloy were formed, respectively, in contrast SS430 showed no layer, which may be due to the formation of a thin oxide layer. One of the typical methods to mitigate corrosion of stainless steels in liquid Bi-Pb alloys is controlling the oxygen concentration in the liquid metal to form oxide protective layers on the surface of the stainless steels [2]. To confirm the corrosion of the steels and stainless steels in an operating Li||Sb-Pb cells, test coupons placed as PCCs in the cells which were charged/discharged for 500 h are analyzed (Fig. 3). Obvious recession without the Fe-Sb layer was confirmed on 1018. Although the Fe-Cr-Ni-Sb layer was formed on SS301, some recession occurred. SS430 shows thin uniform Fe-Cr-Sb layer and no recession. During discharge, Li mainly alloys with Sb in the positive electrode to form Li-Sb-Pb alloys with low Pb concentration, and then the Li dealloys from the Li-Sb-Pb alloys on charging. These processes may destroy the layer of Fe-Sb and Fe-Cr-Ni-Sb alloys. Furthermore, Li dramatically reduces the partial pressure of oxygen in the system, and then oxide layers on the steel or stainless steel may not be stable. However, it was suggested in this study that Fe-Cr-Sb alloy is a stable intermetallic compounds during the charge/discharge processes. Therefore, SS430 is a candidate PCC for Li||Sb-Pb LMB. [1] H. Kim, et al., Chem. Rev., (2012). [2] J. Zhang, et al., J. Nucl. Mater., 373, 351–377 (2008). The authors are grateful for the financial support of the USDOE ARPA-E, TOTAL, Marubun Research Promotion Foundation, and Murata Overseas Scholarship Foundation.

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A fabrication process for CoPt nanodot arrays using an electrochemical approach was proposed. The nano-patterned substrates were formed using electron beam lithography (EBL) and UV nanoimprint lithography (UV-NIL). CoPt was electrodeposited into nano-patterned Si substrates. CoPt nandot arrays with 35 nm diameter and 50 nm pitch using EBL and 50 nm diameter and 100 nm pitch using UV-NIL were successfully fabricated. In addition, we attempted to apply 1 inch glass disk substrates with CoZrNb underlayer as soft magnetic underlayer (SUL). We focused on the surface condition of the underlayers to deposit CoPt with uniformity and high magnetic properties. As a result, CoPt nanodot arrays were successfully fabricated on a 1 inch glass disk substrate with SUL using thin Cu intermediate layers. From these results, it has been found that the combination of the UV-NIL and electrochemical processes is a candidate for the fabrication of ultra high-density magnetic recording media.