Osamu Takeda

Thermodynamic Analysis of Contamination by Alloying Elements in Aluminum Recycling

In previous studies on the physical chemistry of pyrometallurgical processing of aluminum scrap, only a limited number of thermodynamic parameters, such as the Gibbs free energy change of impurity reactions and the variation of activity of an impurity in molten aluminum, were taken into account. In contrast, in this study we thermodynamically evaluated the quantitative removal limit of impurities during the remelting of aluminum scrap; all relevant parameters, such as the total pressure, the activity coefficient of the target impurity, the temperature, the oxygen partial pressure, and the activity coefficient of oxidation product, were considered. For 45 elements that usually occur in aluminum products, the distribution ratios among the metal, slag, and gas phases in the aluminum remelting process were obtained. Our results show that, except for elements such as Mg and Zn, most of the impurities occurred as troublesome tramp elements that are difficult to remove, and our results also indicate that the extent to which the process parameters such as oxygen partial pressure, temperature, and flux composition can be changed in aluminum production is quite limited compared to that for iron and copper production, owing to aluminums relatively low melting point and strong affinity for oxygen. Therefore, the control of impurities in the disassembly process and the quality of scrap play important roles in suppressing contamination in aluminum recycling.

Thermodynamic analysis for the controllability of elements in the recycling process of metals.

This study presents the results of chemical thermodynamic analysis on the distribution of elements in the smelting process of metallic materials to examine the controllability of impurities in the pyrometallurgical technique. The results of the present work can give an answer against the frequently given question; Which impurity element can be removable in metallurgical process? or How far can the impurity level be controlled?. The proposed method was applied to estimate the distribution of 29 elements for a copper converter and 26 elements for a steel-making process and shows the distribution tendency of elements among the gas, slag, and metal phases as well as clarifying which metals can be recovered or removed from secondary resources in metallurgical processes. The effects of temperature, oxygen partial pressure, and slag composition on the distribution ratio of elements were also evaluated, and the removal limit or controllability of impurity in these two processes was presented. This study results in thermodynamic features of various elements in the pyrometallurgical process and also shows, even by varying process parameters such as temperature and oxygen partial pressure, no drastic improvement of removal efficiency should be expected, except for lead and tin in copper.

Evaluation of Ti-Cr-Cu alloys for dental applications

This study examined the characteristics of as-cast Ti-Cr(7–19%)-Cu(3–7%) (all percentages in this article are mass%) alloys to evaluate their suitability for dental applications; studies on the alloy structures and mechanical properties, grindability, and corrosion behavior were included in the investigation. The alloys were centrifugally cast and bench-cooled in investment molds. The x-ray diffractometry of the as-cast alloys bench-cooled in the molds indicated the following phases: α+β+ω in the 7% Cr and 7% Cr+3% Cu; β+ω in the 13%Cr; and β in the 13%Cr+3% Cu through the 19%Cr+3% Cu alloys. The strengths of the binary β Ti-Cr and ternary β Ti-Cr-Cu alloys with 13 and 19% Cr were approximately two times higher than those of CP Ti. The alloy ductility was dependent on the chemical composition and thus, the microstructure. The 7% Cr alloys were extremely brittle and hard due to the ω phase, but the ductility was restored in the 13 and 19% Cr alloys. The hardness (HV) of the cast 13 and 19% Cr alloys was approximately 300–350 compared with a value of 200 for CP Ti. The grindability of the cast alloys was examined using a rotating SiC wheel at speeds (circumferential) of 500 and 1250 m/min. At the higher speed, the grindability of the 13 and 19% Cr alloys increased with the Cu content. The grindability of the 13% Cr alloy with 7% Cu was similar to that of CP Ti. Evaluation of the corrosion behavior in an artificial saliva revealed that the alloys are like many other titanium alloys within the normal intraoral oxidation potential. The wear resistance testing of these alloys also showed favorable results.

Novel autoimmune phenomena induced in vivo by a new DNA binding protein Nuc: a study on MRL/n mice

We previously purified a 55 kDa protein that preferentially expands anti-DNA antibody production both in vitro and in vivo across the H-2 barrier from culture supernatants of KML1-7 cells, cloned from a lupus-prone MRL/lpr mouse. By using the purified protein, termed nucleobindin (Nuc), we cloned cDNA and produced recombinant(r) Nuc in Escherichia coli. To elucidate the function of rNuc in vivo, we initially injected intraperitoneally 5 micrograms of rNuc without adjuvant into female MRL/n mice at 8 weeks of age and continued injection twice a week. As early as 5 weeks after administration, all mice treated showed an increase in IgG anti-double stranded (ds) DNA antibodies accompanied by IgG hypergammaglobulinemia (HG). Of particular interest was that these mice also produced anti-U1RNP antibodies and rheumatoid factor (RF) of IgG class, but not anti-Sm antibodies. Histopathologically, hypercellularity with occasional crescents in the glomeruli was observed, but evidence for lupus nephritis was lacking, indicating that some factors other than Nuc are necessary for the development of a lupus syndrome observed in MRL/lpr mice. Similar administration of lipopolysaccharide into MRL/n mice failed to induce autoantibodies except for a slight increase in serum IgG, suggesting that these autoimmune responses are not due simply to polyclonal B-cell activation. The presence of rNuc will give us a clue for further understanding of autoimmunity.

Thermodynamic criteria for the removal of impurities from end-of-life magnesium alloys by evaporation and flux treatment

Abstract In this paper, the possibility of removing impurities during magnesium recycling with pyrometallurgical techniques has been evaluated by using a thermodynamic analysis. For 25 different elements that are likely to be contained in industrial magnesium alloys, the equilibrium distribution ratios between the metal, slag and gas phases in the magnesium remelting process were calculated assuming binary systems of magnesium and an impurity element. It was found that calcium, gadolinium, lithium, ytterbium and yttrium can be removed from the remelted end-of-life (EoL) magnesium products by oxidization. Calcium, cerium, gadolinium, lanthanum, lithium, plutonium, sodium, strontium and yttrium can be removed by chlorination with a salt flux. However, the other elements contained in magnesium alloy scrap are scarcely removed and this may contribute toward future contamination problems. The third technological option for the recycling of EoL magnesium products is magnesium recovery by a distillation process. Based on thermodynamic considerations, it is predicted that high-purity magnesium can be recovered through distillation because of its high vapor pressure, yet there is a limit on recoverability that depends on the equilibrium vapor pressure of the alloying elements and the large energy consumption. Therefore, the sustainable recycling of EoL magnesium products should be an important consideration in the design of advanced magnesium alloys or the development of new refining processes.

Induction of autoantibodies in normal mice by injection of nucleobindin and natural occurrence of antibodies against nucleobindin in autoimmune MRL/lpr/lpr mice

Our previous works have shown that nucleobindin (Nuc) or recombinant (r) Nuc not only augments anti-DNA antibody production in vitro but also accelerates autoimmune response in vivo in MRL/+/+ (MRL/n) mice which are the substrain of autoimmune MRL/lpr/lpr (MRL/l) mice. To investigate whether rNuc can induce autoimmune response similarly in naive mice, we carried out intraperitoneal (i.p.) injection of rNuc (5 micrograms) without adjuvant into 8-week-old female BALB/c mice and continued injection twice a week for 12 weeks. About 5 weeks after the first injection, all the mice began to show IgG hypergammaglobulinemia (HG) followed by elevation of a number of autoantibodies of the IgG class such as anti-double-stranded (ds) DNA, anti-U1 ribonuclear protein (RNP), anti-ssB(La) and anti-Fc antibodies (RF), but not by anti-Sm antibodies. However, the IgG anti-dsDNA antibody response and histopathological changes in the kidney of these BALB/c mice were not so noticeable as those in MRL/n mice induced by rNuc in our previous experiment. In contrast, the IgG anti-rNuc antibody response of normal BALB/c mice induced by rNuc was stronger than that of MRL/n mice induced by rNuc. Since the titers of each autoantibody of BALB/c mice induced by rNuc were not always associated with the level of IgG HG, and either IgG HG or IgG autoantibodies could not be induced by control administration of extracts (5 micrograms) of Escherichia coli with or without harboring plasmid alone, polyclonal B cell activation (PBA) appeared not to be the mechanism of this autoimmunity.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrowinning of Lithium from Molten Salt Containing LiOH for Hydrogen Storage and Transportation

Introduction Hydrogen is expected to contribute in energy saving by the improvement of energy efficiency with use of fuel cell and in reduction of environment burden matters such as CO2 and NOx. However, an effective supply system of hydrogen has not yet been established at this stage. The authors have investigated the system for storage and transportation of hydrogen by using lithium hydride (LiH) as a storage medium [1]. The schematic illustration of the system is shown in Fig. 1. In this system, LiH is synthesized by the reaction of lithium metal with hydrogen gas (H2) produced by conventional methods, e.g. steam reforming of natural gas (hydrogenation process). LiH has great hydrogen storage capacity and is chemically stable at ambient temperatures and pressures. LiH transported from supplier to user is reacted with water, and H2 gas corresponding to 25% of mass of LiH is then released with following reaction: LiH(s) + H2O(l) = H2(g) + LiOH(s) (hydrolysis process). LiOH formed after H2 generation is returned to supplier in which lithium is reproduced by molten salt electrolysis (electrolysis process). The regeneration of lithium metal from LiOH by electrolysis is the most important process in the system, and its fundamental investigation was carried out in this study.

Production of Tantalum Fine Powder by Reduction of Tantalum Chloride with Zinc

Tantalum (Ta) capacitor are mainly used on the mobile devices due to its excellent characteristic such as high capacity per unit volume and high stability. Performance of the tantalum capacitor has close connection to the size and form of the tantalum powder, and these characteristic have been improved by the studies of reduction condition. Tantalum powder is produced industrially by sodiothermic reduction of K2TaF7 in the molten salt consitsting of KCl-NaCl-NaF (Hunter process) This process contains problems such as high reaction temperature and discharge wastes including fluorine. It is also mentioned that it is technically-difficult to reduce the diameter of powder by this process furthermore, therefore a new process is expected to improve the performance of tantalum capacitor. The authors proposed a new process for the production of fine tantalum powder. The process is based on the reduction of TaCl5 by metalic zinc (Zn). The authors previously studied to produce fine powder by the reduction of TaCl5 vapor with Zn vapor, represented by the equation of TaCl5 (g) + 5/2Zn (g) = Ta (s) + 5/2ZnCl2 (g). In the previous study, it was successful to obtain a fine powder which primary particle was smaller than 1μm. However, gas phase reaction is poor in reaction efficiency and is difficult to control the deposition region. For industrialization of the process, it is necessary to improve the reaction efficiency and to facilitate the collection of product. Therefore, the authors propose to use molten salt as a reaction medium, and to inject the vaporized reactant into the molten salt with a carrier gas in this study. By using molten salt as a reaction medium, the reaction efficiency improves due to extend residence time, moreover deposition region can be limited in the molten salt and it can be easier to collect the product. The reaction apparatus used in this study is shown in Fig.1. Reaction apparatus is consist of two reactant vaporized part and one reaction part. TaCl5 (4.4g) and Zn (6.9g) were contained in the vaporized part and molten mixture of NaCl-LiCl (91.4g) was contained in the reaction part made of quartz. These setups were separately heated under purified Ar, the vaporized reactant was injected into the molten salt with a carrier gas (rate of carrier gas : 20ml/min ) after the salt has melted. Temperature of TaCl5 vaporized part was about 500K (pTaCl5 =0.086 MPa ) and that of Zn vaporized part was about 1000K (pZn = 0.012MPa ). The reaction temperature was about 1000K and reaction time was 30min. The setups were cooled in the furnace under Ar after the reaction. The solidified salt and residual Zn were removed in a distilled water and HCl aqueous solution. The sample powder was rinsed with distilled water and ethanol, and dried under vacuum. After the reaction, tantalum powder formed was stored in the molten salts, and deposition region was effectively limited, which served easy collection of the products. Fig.2 shows a representative TEM image of the tantalum powder obtained. As shown in the figure, Ta aggregation of primary particles with diameter of 10100nm was successfully obtained.