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We report the crystal structure and physical properties of Sr2-xLaxIrO4 synthesized by mechanical alloying. The magnetic transition temperature T-N and electrical resistivity decreased with increasing La doping, consistent with previous studies involving single-crystalline samples. We also identified the relationship between T-N and tetragonal distortion (c/a) in this system. This result suggests that the magnetism of the Sr214 system is strongly correlated with its crystal structure. Zero-field muon spin rotation/relaxation studies revealed that short-range antiferromagnetic ordering is realized in Sr1.9La0.1IrO4; also, the spin-glass state is stabilized in the low-temperature region. The Ir moment estimated from the longitudinal field mu SR results is 0.045 mu(B), ten times smaller than that of Sr2IrO4 (similar to 0.4 mu(B)), indicating that electrons are introduced into the Ir atoms.

At J-PARC MUSE (Muon Science Establishment), one graphite target was installed in the proton beam line on the way to the neutron source, from which four sets of the secondary lines were designed to be extracted and extended into two experimental halls (toward the west wing, one decay-surface muon channel (D-Line) and the axial focusing muon channel (U-Line), and towards the east wing one surface muon channel (S-Line) and one fundamental muon channel (H-Line). MUSE has been suffering from many troubles such as the giant earthquake, fire, twice water leakage from the neutron target. Although the proton beam intensity was restricted lower than 200 kW, we have been having a rather stable operation at the MUSE since February, 2016. In this paper, the latest situation on the MUSE is reported.

The electronic structure of interstitial hydrogen in a compound semiconductor FeS$_2$ (naturally $n$-type) is inferred from a muon study. An implanted muon (Mu, a pseudo-hydrogen) forms electronically different defect centers discerned by the hyperfine parameter ($\omega_{\rm hf}$). A body of evidence indicates that one muon is situated at the center of an iron-cornered tetrahedron with nearly isotropic $\omega_{\rm hf}$ (Mu$_{\rm p}$), and that the other exists as a diamagnetic state (Mu$_{\rm d}$, $\omega_{\rm hf}\simeq 0$). Their response to thermal agitation indicates that the Mu$_{\rm d}$ center accompanies a shallow level (donor or acceptor) understood by effective mass model while the electronic structure of Mu$_{\rm p}$ center is more isolated from host than Mu$_{\rm d}$ to form a deeper donor level. These observations suggest that interstitial hydrogen also serves as an electronically active impurity in FeS$_2$. Based on earlier reports on the hydrogen diffusion in FeS$_2$, possibility of fast diffusion for Mu$_{\rm p}$ leading to formation of a complex defect state (Mu$^*_{\rm d}$, $T\le 100$ K) or to motional narrowing state (Mu$^*_{\rm p}$, $T\ge 150$ K) is also discussed., Comment: 6 pages, 5 figures

In this study, a novel chlorination technique for metallic titanium (Ti) was devised in order to establish a recycling process that uses both Ti metal scrap and iron chloride (FeClx) waste, and its feasibility was demonstrated. Direct reaction between Ti and FeClx has drawbacks such as slow kinetics of Ti chlorination and high volatilization of FeClx. To overcome these, the authors proposed a chlorination technique utilizing a reaction mediator in molten salt. Based on thermodynamic analyses of lanthanoid chlorides, some fundamental experiments were carried out with samarium trichloride (SmCl3) as a reaction mediator. It was experimentally demonstrated that SmCl3 in molten magnesium chloride (MgCl2) can smoothly chlorinate Ti metal into gaseous titanium tetrachloride (TiCl4), and the by-product SmCl2 in the molten salt can be regenerated into SmCl3 by FeCl2. Thus, SmCl3 in a molten salt works efficiently as a reaction mediator, and the newly proposed chlorination technique has the potential to make the Ti recycling process more efficient and environmentally friendly. [doi:10.2320/matertrans.M-M2014838]

K3Cu3AlO2(SO4)4 is a highly one-dimensional spin-1/2 inequilateral diamond-chain antiferromagnet. Spinon continuum and spin-singlet dimer excitations are observed in the inelastic neutron scattering spectra, which is in excellent agreement with a theoretical prediction: a dimer-monomer composite structure, where the dimer is caused by strong antiferromagnetic (AFM) coupling and the monomer forms an almost isolated quantum AFM chain controlling low-energy excitations. Moreover, muon spin rotation/relaxation spectroscopy shows no long-range ordering down to 90 mK, which is roughly three orders of magnitude lower than the exchange interaction of the quantum AFM chain. K3Cu3AlO2(SO4)4 is, thus, regarded as a compound that exhibits a Tomonaga-Luttinger spin liquid behavior at low temperatures close to the ground state.

We have successfully synthesized the single crystal of $\mathrm{A}{\mathrm{g}}_{2}\mathrm{P}{\mathrm{d}}_{3}\mathrm{S}$, which exhibits superconductivity with the transition temperature of ${T}_{\mathrm{c}}=2.25\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. $\mathrm{A}{\mathrm{g}}_{2}\mathrm{P}{\mathrm{d}}_{3}\mathrm{S}$ crystallizes in the space group $P{4}_{1}32$ with the filled $\ensuremath{\beta}\ensuremath{-}\mathrm{Mn}$ structure, which has no inversion symmetry. The value of the Ginzburg-Landau parameter ${\ensuremath{\kappa}}_{\mathrm{GL}}$ indicates that $\mathrm{A}{\mathrm{g}}_{2}\mathrm{P}{\mathrm{d}}_{3}\mathrm{S}$ is a type-II superconductor. $\mathrm{\ensuremath{\Delta}}C({T}_{\mathrm{c}})/{\ensuremath{\gamma}}_{\mathrm{n}}{T}_{\mathrm{c}}=1.50$ and $2\mathrm{\ensuremath{\Delta}}/{k}_{B}{T}_{\mathrm{c}}=3.48$ from the heat-capacity analyses indicate that $\mathrm{A}{\mathrm{g}}_{2}\mathrm{P}{\mathrm{d}}_{3}\mathrm{S}$ is a weak-coupling Bardeen-Cooper-Schrieffer (BCS) superconductor with an isotropic superconducting gap. On the other hand, the violation of the Werthamer-Helfand-Hohenberg curve in the $H\ensuremath{-}T$ phase diagram implies $\mathrm{A}{\mathrm{g}}_{2}\mathrm{P}{\mathrm{d}}_{3}\mathrm{S}$ is not a typical BCS superconductor.

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.

Thermodynamic study of the chlorination reactions of oxides such as titanium oxides and iron oxides at elevated temperatures was carried out in order to consider the removal of iron from titanium ore using selective chlorination method. In particular, various chlorination reactions were analyzed by utilizing chemical potential diagrams, and the applicability and usefulness of this thermodynamic study for analyzing the selective chlorination of titanium ore were demonstrated. Furthermore, chlorination reactions using various types of chlorinating agents were discussed from different viewpoints. It was shown that the selective chlorination of iron from titanium ore by HCl gas is thermodynamically feasible and efficient for upgrading titanium ore. Further, thermodynamic analysis showed that under certain conditions, TiCl4 can be used as a chlorinating agent for the iron in the ore, and iron can be removed by evaporation directly from the ore as chloride gas. The results presented in this study provide useful information for developing a process for upgrading low-grade titanium ore for use as a titanium smelting feed through a dry method.

We report on the local electronic structure of interstitial muon (Mu) as pseudo-hydrogen in In-Ga-Zn oxide (IGZO) semiconductor studied by muon spin rotation/relaxation ($\mu$SR) experiment. In polycrystalline (c-) IGZO, it is inferred that Mu is in a diamagnetic state, where the $\mu$SR time spectra under zero external field is perfectly described by the Gaussian Kubo-Toyabe relaxation function with the linewidth $\Delta$ serving as a sensitive measure for the random local fields from In/Ga nuclear magnetic moments. The magnitude of $\Delta$ combined with the density functional theory calculations for H (to mimic Mu) suggests that Mu occupies Zn-O bond-center site (Mu$_{\rm BC}$) similar to the case in crystalline ZnO. This implies that the diamagnetic state in c-IGZO corresponds to Mu$_{\rm BC}^+$, thus serving as an electron donor. In amorphous (a-) IGZO, the local Mu structure in as-deposited films is nearly identical with that in c-IGZO, suggesting Mu$_{\rm BC}^+$ for the electronic state. In contrast, the diamagnetic signal in heavily hydrogenated a-IGZO films exhibits the Lorentzian Kubo-Toyabe relaxation, implying that Mu accompanies more inhomogeneous distribution of the neighboring nuclear spins that may involve Mu$^-$H$^-$-complex state in an oxygen vacancy., Comment: 5 pages (in double column), 3 figures

High-purity Si used for photovoltaic applications, namely, solar-grade Si (SOG-Si), is commercially manufactured using the Siemens process. Although the present levels of supply satisfy the demand, there can potentially be a shortage of SOG-Si in the long term. To overcome the low productivity of the Siemens process, various types of SOG-Si production/purification processes have been developed as post-Siemens processes. Some processes are under development as new commercial processes. These processes can be classified into the following three categories: (1) hydrogen reduction and/or thermal decomposition of silane-based gases in improved Siemens-based processes, (2) metallothermic reduction of silicon halides by Zn or Al, and (3) upgrading metallurgical-grade Si by employing metallurgical purification methods. This paper presents a review of various types of SOG-Si production processes, particularly those based on the hydrogen reduction and/or thermal decomposition of halides and silane-based gases. These processes are classified on the basis of Si compounds used and the reaction types; further, the features of these processes are also analyzed. Future prospects for the development of new high-purity Si production process are also presented.

For the production of high-grade titanium dioxide (TiO2) directly from titanium ore (Ti ore), a fundamental study on the development of a novel carbo-selective-chlorination method using titanium tetrachloride (TiCl4) as a chlorinating agent was carried out. In order to selectively remove iron directly from low-grade Ti ore (mainly FeTiO3), Ti ore and carbon powder were set in a gas-tight quartz tube that was then placed in a horizontal furnace to react with TiCl4 at 1100K. In the experiments, various types of Ti ores produced in different countries were reacted with TiCl4 for durations from 4 to 6h. Under certain conditions, the iron in the titanium ore was removed as iron chloride (FeCl2), and 98% TiO2 was obtained after the experiments. The effectiveness of TiCl4 as a chlorinating agent for the carbo-selective-chlorination of iron oxide was verified in this study. Thus, it was demonstrated that the carbo-selective-chlorination is feasible for the selective removal of iron directly from low-grade titanium ore containing 51% TiO2 to produce high-grade TiO2 feed in a single step. [doi:10.2320/matertrans.M-M2013843]

With the aim of minimizing the loss of platinum into slags by controlling the slag composition during the high-temperature recycling process, the effects of representative slag components, namely, Al2O3, MgO, Fe2O3, and CuOx, on the dissolution behavior of platinum into Na2O­SiO2-based slags were investigated. The solubility of platinum in the slags was measured by equilibrating the Na2O­SiO2-based slags with pure solid platinum at 1473K in air. The dissolution of platinum in the slags was found to be suppressed by the addition of Al2O3, MgO, and Fe2O3 .A l2O3 and Fe2O3 behaved as acidic oxides, whereas MgO behaved as a diluent and decreased the solubility of platinum in the slags. CuOx behaved as a weakly basic oxide and slightly enhanced the dissolution of platinum into the slags. The correlation between the platinate capacity of the slag, which is a parameter proposed in this paper, and the optical basicity enabled the content of platinum in slags at 1473K to be estimated from the slag composition. [doi:10.2320/matertrans.M2014042]

Platinum group metals (PGMs), which have high melting temperatures and high chemical durability, are widely used as catalysts and electronic materials. It is important to develop their recycling processes in order to create a sustainable utilisation of the PGM resources. In high-temperature extractive processes with slag treatment, however, some elements are not recovered, probably because of oxidation. In the author's research group, the mechanism of PGM dissolution into slags was investigated to clarify suitable conditions for the recycling process. Solubilities of PGMs, such as Pt, Ru and Rh, into various compositions of slag were measured together with their temperature dependencies. By reviewing the results, the dissolution mechanism of each element is discussed in the present paper.

The magnetic states in the novel K2NiF4-type quasi-2-D spin-orbit-induced Mott insulator Ba2IrO4 was studied using magnetic susceptibility, muon spin rotation (µSR), and high-pressure resistivity measurements. In Ba2IrO4, a Neel ordered state was found to be stabilized at temperatures below TN (Neel temperature) ∼ 240 K. The critical exponent β ∼ 0.18 suggests a quasi-2-D Heisenberg antiferromagnetic state on the IrO2 planar square lattice. The magnetic moment is significantly reduced to ∼0.34 µB/Ir-atom, probably due to a low-dimensional quantum spin fluctuation with a large magnetic intra-plane correlation |J|. A non-Fermi liquid-like behavior with carrier scattering due to the spin fluctuation was observed in the metallic state under high pressures of more than 13.8 GPa.

To develop a simple and effective process for upgrading low-grade titanium ore (ilmenite, mainly FeTiO3), a new selective chlorination process based on the use of calcium chloride (CaCl2) as the chlorine source was investigated in this study. Titanium ore and a titanium ore/CaCl2 mixture were placed in two separate crucibles inside a gas-tight quartz tube that was then positioned in a horizontal furnace. In the experiments, the titanium ore in the two crucibles reacted with either HCl produced from CaCl2 or CaCl2 itself at 1100 K (827 °C), leading to the selective removal of the iron present in the titanium ore as iron chlorides [FeClx(l,g) (x = 2, 3)]. Various kinds of titanium ores produced in different countries were used as feedstock, and the influence of the particle size and atmosphere on the selective chlorination was investigated. Under certain conditions, titanium dioxide (TiO2) with purity of about 97 pct was directly obtained in a single step from titanium ore containing 51 pct TiO2. Thus, selective chlorination is a feasible method for producing high purity titanium dioxide from low-grade titanium ore.

Among platinum group metals (PGMs), Pt, Pd, and Rh are the essential constituents of automotive catalysts. Recovery of PGMs from catalyst scrap is important, but it is difficult because PGMs are chemically stable and are present as minor components in the scrap. In this study, the authors investigated the reaction between PGMs and FeCl2 vapor in order to develop a novel method for the separation and concentration of PGMs directly from catalyst scrap. The wire samples of Pt, Pd, and Rh were reacted with FeCl2 vapor in a steel vessel maintained at 1200 K. After the heat treatment, the surfaces of PGM wires were alloyed with Fe, and these samples became magnetized. The results obtained in this study suggest that a FeCl2 vapor treatment followed by magnetic separation can be utilized as an effective technique for the separation of PGMs directly from catalyst scrap.

To understand the behavior of rhodium during its recovery process, the dissolution behaviors of rhodium in Na2O-SiO2 and in CaO-SiO2 slags at temperatures ranging from 1423 K to 1623 K (from 1150 °C to 1350 °C) and from 1773 K to 1873 K (from 1500 °C to 1600 °C), respectively, in an oxidizing atmosphere were investigated. The solubility of rhodium in the slags was found to increase with increasing oxygen partial pressure, temperature, and the basic oxide content. The correlation between the solubility of rhodium and the oxygen partial pressure suggested that rhodium dissolved into the slags as RhO1.5. The dissolution of rhodium was slightly endothermic: the enthalpy change of the dissolution of solid rhodium was determined to be 50 ± 10 kJ/mol for the 50(mass pct)Na2O-50SiO2; and 188 ± 94 kJ/mol for the 56(mass pct)CaO-44SiO2 slag systems. The increase in the solubility of rhodium with the basic oxide content indicated that rhodium exhibits acidic behavior in slags. The correlation between the solubility of rhodium and the sulfide capacity of the slags suggested that the ionic species of rhodium in slags is the rhodate ion, RhO 2 − . The rhodate capacity of the slags was defined, and its application to estimate the possible rhodium content in various slag systems was proposed.

Aiming to optimize rhodium recovery in the high temperature recycling process by minimizing rhodium loss into slags in an oxidizing atmosphere by controlling slag composition, the effects of representative slag components, such as Al2O3, MgO, and CuOx, on the dissolution behavior of rhodium into the Na2O-SiO2 slags was investigated. The solubility of rhodium was measured by equilibrating the sodium silicate based slags with pure solid rhodium at 1473 K in air. Considering that rhodium dissolved into slags as RhO1.5, the effect of the oxide addition on the activity coefficient of RhO1.5 in slags was determined. The dissolution of rhodium in slags was suppressed by the addition of Al2O3 and MgO, where Al2O3 behaved as an acidic oxide and MgO behaved as a diluent of slag basicity at a fixed Na2O/SiO2 ratio of 0.97. The content of copper in solid rhodium equilibrated with the CuOx bearing slags slightly increased with increasing content of CuOx, and CuOx was found to slightly enhance the dissolution of rhodium. Rhodate capacity of all slag systems increased with increasing optical basicity, suggesting that the correlation between rhodate capacity and the optical basicity enables the estimation of the content of rhodium in slags of which thermodynamic properties of rhodium are not clarified.

A selective chlorination process using magnesium chloride (MgCl2) as chlorinating agent was investigated with the aim of developing a process for removing iron directly from ilmenite, which is a low-grade titanium ore known as FeTiO3. Two crucibles, one consisting of titanium ore and the other consisting of a mixture of titanium ore and MgCl2, were placed in a gas-tight quartz tube, and then both crucibles were heated to 1000K. In some experiments, H2O vapor was introduced in the quartz tube. HCl gas produced from the MgCl2/titanium ore mixture reacted with the iron present in the titanium ore placed in the other crucible to produce TiO2. Iron present in the titanium ore of the titanium ore/MgCl2 mixture reacted with MgCl2, and MgTiO3 and MgO were obtained. Iron in the titanium ore present in both crucibles was removed as FeCl2 (l,g). In these experiments, the effects of the particle size of the titanium ore and the atmosphere on selective chlorination were investigated. In addition, titanium ores produced in Vietnam, Australia and China were used as feedstocks. By the chlorination process, 97% TiO2 was obtained directly in one step from the low-grade titanium ore containing 51% TiO2 under certain conditions, thus demonstrating the feasibility of the selective chlorination process for producing high-purity titanium dioxide from low-grade titanium ore. [doi:10.2320/matertrans.M-M2013810]

It is commonly believed that the deoxidation of titanium (Ti), or the direct removal of oxygen (O) dissolved in metallic Ti, is practically impossible when magnesium (Mg) is used as the deoxidizing agent. In recent years, it has been experimentally demonstrated that O dissolved in Ti can be directly removed using MgCl2 molten salt electrolysis. By the electrochemical deoxidation technique, Ti wires containing 0.12 mass% O were deoxidized to less than 0.02 mass% O. In some cases, the concentration of O in the Ti wires was reduced to the level of 0.01 mass% O, which cannot be attained using the current Kroll process. The possible application of this deoxidation technique to practical industrial recycling processes is also discussed.

Background Previous studies have reported that patients undergoing oesophagectomy in high-volume hospitals experience lower mortality rates. However, there has been ongoing discussion regarding the validity of evidence for this association. The purpose of this study was to investigate the relationship between hospital volume and risk-adjusted mortality following oesophagectomy in Japan, using a nationwide web-based database. Methods The study included patients registered in the database as having undergone oesophagectomy with reconstruction between 2011 and 2013. Outcome measures were 30-day and operative mortality rates. Logistic regression analysis was used to adjust for hospital volume, surgeon volume and risk factors for mortality after oesophagectomy. Results A total of 16 556 oesophagectomies at 988 hospitals were included; the overall unadjusted 30-day and operative mortality rates were 1·1 and 3·0 per cent respectively. The unadjusted operative mortality rate in hospitals performing fewer than ten procedures per year (5·1 per cent) was more than three times higher than that in hospitals conducting 30 or more procedures annually (1·5 per cent). Multivariable models indicated that hospital volume had a significant effect on 30-day (odds ratio 0·88 per 10-patient increase; P = 0·012) and operative (odds ratio 0·86 per 10-patient increase; P < 0·001) mortality. Conclusion In Japan, high-volume hospitals had lower risk-adjusted 30-day and operative mortality rates following oesophagectomy compared with low-volume hospitals.

Platinum (Pt) is typically recovered by employing dissolution processes in aqueous solutions; however, these processes require a long processing time and considerable quantities of acids with strong oxidants owing to the high chemical stability of Pt. In order to develop an efficient dissolution process, we studied chlorination treatments for Pt prior to dissolution. Chlorination was carried out at 673 K to 873 K (400 °C to 600 °C) using copper(II) chloride (CuCl2) as a chlorine source. While pure Pt was insoluble in hydrochloric acid (HCl(aq)), the entire Pt component of the treated sample dissolved in HCl(aq) under certain conditions. Therefore, the proposed method can be used as a new, environmental friendly Pt recovery process.

The solubility and the dissolution mechanism of Ru in the CaO–SiO2 ,N a 2O–SiO2, and Na2O–SiO2–Al2O3 slag systems have been investigated in various conditions in order to understand the Ru dissolution behavior during pyrometallurgical recovery. The Ru solubility increases with an increase in the oxygen partial pressure and content of basic oxides; however it decreases with an increase in temperature. This implies that Ru dissolves in slag as an acidic oxide. The dissolution reaction is found to be Ru þ 3/4O2 þ 1/2O2� ¼ RuO2 � and � H � ¼� 130 � 20 kJ/mol. From the dissolution behavior, Ru loss into the slag during Ru recovery by Cu smelting has been estimated to be about 50 ppmw. [doi:10.2320/matertrans.M-M2011821]

Various types of processes for solargrade silicon (SOG-Si) production/purification have been developed with the aim of overcoming the low productivity of the Siemens process. These processes can be divided into three groups: decomposition and/or hydrogen reduction of silane gases by improving the currently used commercial processes; purification of metallurgical-grade silicon using metallurgical purification methods; and metallothermic reduction of silicon halides by metal reductants such as zinc and aluminum. This paper reviews the features of various SOG-Si production processes, particularly the processes based on metallothermic reduction, by classifying them according to the types of reductants and the silicon compounds used. Prospects for development of new processes for producing high-purity silicon are presented.

To develop a new production process for solar-grade Si, a fundamental study on halidothermic reduction based on the subhalide reduction of SiCl4 by Al subchloride reductant was carried out at 1273 K (1000 °C). Aluminum subchloride reductant was produced by reacting AlCl3 vapor with metallic Al. Silicon tetrachloride was reduced to Si in a gas-phase reaction by vapors of Al subchloride reductant. Silicon deposits produced in the halidothermic reduction were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray fluorescence (XRF). The Al content in the Si deposits was no more than 0.5 at pct. The Si deposits have a fibrous or hexagonal columnar morphology with diameters ranging from 100 nm to several tens of microns. The reaction was discussed by comparison with the results of the conventional aluminothermic reduction of SiCl4. Moreover, the halidothermic reduction reactions were analyzed from thermodynamical viewpoints. This study demonstrates the feasibility of a halidothermic reduction for producing solar-grade Si with high productivity.

A fundamental study was conducted on a new process for producing vanadium (V) metal by the preform reduction process (PRP) based on metallothermic reduction of vanadium pentoxide (V 2 O 5 ). Feed preforms with good mechanical strength even at elevated temperatures were prepared by adding either CaO or MgO to V 2 O 5 feed powder because V 2 O 5 has a low melting point of 963 K; thus complex oxides (Ca x V y O z , Mg x V y O z ) with high melting point at more than 1273 K were obtained. Reduction experiments were conducted by using either Ca or Mg vapor at 1273 K for 6 h. V metal with a purity of more than 99% was successfully obtained when using Mg as a reductant. The feasibility of producing V metal by the PRP will be discussed on the basis of fundamental experiments.

High purity silicon used for photovoltaic application, namely solar grade silicon (SOG-Si), has been commercially supplied mainly from the off-grade high purity silicon manufactured by the Siemens process. However, recent and rapid growth in solar cell production induces a serious shortage of SOG-Si. With an aim of resolving low productivity of the Siemens process, various types of SOG-Si production/purification processes have been invented as a post-Siemens process. Some processes are currently under development aiming at establishment of commercial process. These processes can be classified into the following three technologies: (1) decomposition and/or hydrogen reduction of silane gases by improving the current commercial Siemens-based processes, (2) metallothermic reduction of silicon halide compounds by zinc or aluminum, and (3) upgrading metallurgical-grade silicon by employing metallurgical purification methods. This paper reviews the features of the SOG-Si production processes, particularly the processes based on the metallothermic reduction. These metallothermic reduction processes are classified from the viewpoint of the reductant types and silicon compounds. The future prospect for the development of new high purity silicon production process is presented.

The abundance of vanadium (V) in the earth's crust is 150 ppm; this is significantly larger than the abundance of nickel, zinc, or copper which are classified as common metals. However, V metal belongs to a set of “less-common metals” or “rare metals” because of the small production volume. This fact is partly due to its low concentration in its natural ores and the uneven distribution of its minerals. V metal is commercially produced by the aluminothermic reduction (ATR) of vanadium pentoxide (V2O5). The reduction product of the ATR process is a vanadium-aluminum (V-Al) alloy containing approximately 20 mass% of aluminum. Further purification process is required for obtaining pure V metal, used for the fabrication of functional materials such as hydrogen storage alloys. At this stage, an effective production process of pure V metal has not been established. Therefore, there is a strong requirement for the development of a simple and efficient process for the direct production of high-purity V metal and its alloy. This paper reviews various types of processes for producing V metal and its alloys. These reduction processes are classified on the basis of the V compounds and reaction types, and their features are reviewed. Lastly, the future prospects for the development of new processes for the production of high-purity V metal are presented.

An emulsion-counter hybrid experiment (KEK E176) was carried out to search for double strangeness systems such as double- Λ hypernuclei and H -dibaryons. More than 10% of Ξ − hyperons produced in the (K − , K + ) reaction were brought to rest in the nuclear emulsion. We have obtained 98 candidate events of nuclear capture at rest of Ξ − hyperons which are described in this report. Among those, four events were identified as sequential weak decay of double- Λ hypernuclei. The binding energies of Ξ − -( 12 C, 14 N and 16 O) states have been estimated for two events which emit twin single- Λ hypernuclei back to back from the capture point. The Σ − p decay vertex of an H -dibaryon was searched for near the capture point and no evidence was observed. Upper limits for the branching ratio of H emission are 5–10% for a lifetime less than 0.1 ns at the 90% confidence level. The trapping probabilities of single and double strangeness to a nuclear fragment following Ξ − capture at rest have been studied.

In order to develop a new production process for Al–Sc alloys, a fundamental study on the electrolysis in CaCl2–Sc2O3 melts was conducted using a small-scale laboratory cell. Al–Sc alloys were electrochemically produced by cathodically polarizing an Al liquid electrode in CaCl2–Sc2O3 melts at 1173 K. Metallic-colored spherical samples were produced by the electrolysis and were analyzed by XRD, EPMA, XRF, and ICP–AES. The electrolyzed samples consisted of Al and Al3Sc phases. The purity of the obtained Al–Sc alloys was greater than 99 mass%, and the calcium content was less than 0.65 mass%. This study demonstrates the feasibility of Al–Sc alloy production directly from Sc2O3 by electrochemical methods.

In this study, a new method for producing Si, called "halidothermic reduction", was investigated with the purpose of producing solar-grade silicon (SOG-Si); by this method, SiCl 4 was reduced by gaseous subhalide used as the reductant. Si was produced by reacting SiCl 4 with Al subhalides, which were produced by reacting AlCl 3 with metallic Al. Fibrous Si with diameters ranging from submicrons to several tens of micrometers was deposited as a result of halidothermic reduction of SiCl 4 by an Al subchloride (AlCl x ) reductant at 1273 K. The size of Si deposits and the reaction rate were increased by simultaneously supplying AlCl 3 and SiCl 4 vapors to a reaction tube holding Al metal. The impurity level of the obtained Si was found to be lower than the detection limit of X-ray fluorescence. Halidothermic reduction is suitable for producing high-purity Si since all reactants and byproducts exist in the vapor phase. Further, this process has high productivity since the overall reaction is a highly scalable metallothermic reduction reaction.

To develop a novel recycling process for titanium (Ti) metal scrap by utilizing chloride wastes generated from the Kroll process or any other process, some fundamental studies on the reactions between Ti and iron chlorides (FeCl x ) were carried out. Prior to the experiments, thermodynamic analyses on the Ti–Fe–Cl–O system were carried out to enable a discussion on the feasibility of the recycling of Ti metal scrap by FeCl x . Based on the thermodynamic analyses, a metallic Ti sample placed in a quartz tube filled with argon (Ar) gas was reacted with iron chloride (FeCl 2 ) gas at elevated temperatures (900–1200 K), and the reaction product was analyzed. During the experiment, the formation of TiCl 4 gas was visually observed. Black residue containing metallic Fe and Ti was obtained after the experiment, and the reaction ratio of Ti reached 99% under certain experimental conditions. The reaction ratio of Ti and the reaction speed were largely dependant on the morphology of the starting material and could be improved by increasing the reaction temperature over the range of 900–1200 K. The results show that metallic Ti can be recovered in the form of TiCl 4 by utilizing FeCl 2 , and the reaction products of TiCl 4 and Fe can easily be recovered separately.

A fundamental study was conducted on a new process for producing scandium (Sc) metal or aluminium–scandium (Al–Sc) alloy by the calciothermic reduction of scandium oxide (Sc2O3). In this study, aluminium (Al) and calcium chloride (CaCl2) were used as the collector metal and flux for the reduction respectively. A mixture of Sc2O3, Al and CaCl2 in a tantalum crucible was placed inside a stainless steel reaction container, and the feed mixture was reacted with calcium (Ca) vapour at 1273 K for 6 h. After the reduction experiment, the reaction product (CaO), CaCl2 flux and excess Ca reductant were removed from the obtained alloy sample by leaching with an aqueous solution. The formation of Al3Sc in the Al matrix phase of the alloy was confirmed by X-ray diffraction and electron microprobe analysis. This result indicates that Sc2O3 was successfully reduced to metallic Sc and alloyed in situ to form liquid Al–Sc alloy during the reduction. When Al was not used in the reduction experiment, a complex oxid...

In order to establish a new high-speed/(semi-)continuous titanium production process based on the magnesiothermic reduction of titanium subchlorides (subhalide reduction process), a novel synthetic process for obtaining titanium subchlorides (TiCl x , x = 2, 3) by the reaction of titanium tetrachloride (TiCl 4 ) with titanium metal at 1273 K was investigated. It was demonstrated that the efficiency of the TiCl x formation improved drastically when molten salts were used as the reaction medium as compared with that of the synthesis by employing the direct reaction of TiCl 4 gas with solid titanium. The feasibility of the enrichment process of TiCl x in molten salt was also demonstrated. The method for producing the titanium subchlorides investigated in this study can be applied to the new high-speed production process of titanium.

A new niobium (Nb) powder production process based on the reduction of electrochemically dissolved niobium ions (Nbn+) by dysprosium divalent ions (Dy2+) in the NaCl–KCl–MgCl2–DyCl2 molten salt was investigated. Nbn+ ions – feed material – were continuously supplied into the molten salt by the anodic dissolution of a Nb rod. They were subsequently reduced in situ by Dy2+ ions – reductant – in the salt to produce Nb powder. The Dy3+ ions generated were reduced to Dy2+ ions by electrochemical or magnesiothermic reduction at the cathode (liquid Mg–Ag alloy). Fine and uniform Nb powder with a purity of around 99 mass% was successfully obtained under a specific condition. Further, it was found that the reaction time had a small influence on the particle size of the powder. A possible reaction pathway of the reduction of Nbn+ ions by Dy2+ ions in the molten salt was discussed with the aid of an isothermal chemical potential diagram of the Nb–Dy–Cl system at 1000 K.