Papers by Author: Toshihiro Tanaka

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Authors: Iwao Katayama, Toshihiro Tanaka, Shin-ichi Akai, Kisao Yamazaki, Takamichi Iida
Abstract: Activity of tin in liquid Sn-Ag-Bi alloys was derived by EMF measurement of galvanic cell with fused salts electrolyte in the temperature range of 700 to 900K in the whole composition range. Activity of tin at 900K shows very small positive deviation from Raoult’s low for Sn-Bi alloys. Activity of ternary alloys was measured along three pseudo binary systems of Sn-(Ag,Bi) (where xAg/xBi =1/3,1/1 and 3/1). Its concentration dependence is very complex. From the iso-activity curves in the ternary system excess free energy of mixing is derived using Darken’s method for Gibbs-Duhem equation
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Authors: Toshihiro Tanaka, Soichiro Maeda, Nobuyuki Takahira, Nobumitsu Hirai, Joon Ho Lee
Abstract: We have tried to develop the following new material processing for the production of value-added materials from by-products such as kish-graphite, Fe & Cu mixed scraps etc. in steelmaking processes : 1) Production of PdCl2 graphite intercalation compound (PdCl2-GIC) in hydrothermal conditions to create nano-particles encapsulated in kish-graphite. 2) Application of “unusual wetting” of liquid Cu on surface-oxidized Fe to produce composite materials between Cu and ceramics.
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Authors: Masashi Nakamoto, Joon Ho Lee, Toshihiro Tanaka
Abstract: Aiming to design new lubricants in the large strain addition strip process for ultrafine-grained steels, we tested the possibility of using waste slag, which is generated largely from iron and steelmaking processes, municipal waste treatments and so on. We then focused our attention on the slag containing water as the new lubricant. Slag satisfies the requirement of biting the workpiece stably, which cannot be achieved with conventional lubricants, because slag is stable as a solid phase of high hardness at the biting temperature in the strip process (100~200oC). In addition, slag contains water under hydrothermal conditions to provide lubricating effects by lowering glass transition temperature. In the present study, the effect of additive components (Al2O3, B2O3, CaO, MgO, K2O, Li2O and V2O5) on the glass transition temperature of a SiO2-Na2O-based slag containing water was examined. The glass transition temperature of the slag containing water is 150~300 oC, which is lower than that of original slag. It was also found that the glass transition temperature depends on the additive components to the slag.
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Authors: Takeshi Yoshikawa, Shinsuke Sato, Toshihiro Tanaka
Abstract: In order to prepare the functional porous glasses, fabrication of foaming glass materials was achieved utilizing the hydrothermal treatment. In the present paper, SiO2-Na2O-B2O3 glass was hydrated by the hydrothermal hot pressing of the glass powder mixed with pure water under the condition of loading pressure of 40 MPa and heating up to 523K. The hydrothermally treated glass contained 10.8 mass% of water. By heating up to 473 K, it started to foam by releasing water and the porous structure was obtained. The minimum apparent density was obtained to be 0.25 g /cm3 after the heat treatment at 673 K for 300 s. It was clarified that the prepared hydrated glass with the hydrothermal treatment would be promising for fabricating the porous glass materials by firing at low temperature.
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Authors: Nobumitsu Hirai, Tatsuya Tooyama, Toshihiro Tanaka
Abstract: Potential dependence of the friction force between an atomically-flat terrace of Au(100) single crystal and a tip attached to a silicon nitride cantilever of electrochemical atomic force microscope (EC-AFM) have been investigated qualitatively in 0.05 M H2SO4 aqueous solution. It is found that the friction force gains when the potential increases in the potential range between −400 mV and 400 mV vs Hg/Hg2SO4 electrode.
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Authors: Masanori Suzuki, Toshihiro Tanaka
Abstract: Hydrothermal treatment has been conducted to create porous glass or ceramics as value-added materials for the recycling of slag and glass. Under hydrothermal conditions, slag and glass react with a high pressurized H2O and hydrate glass phase containing plenty of H2O is formed to connect raw materials particles to make ceramic materials. The hydrothermal process takes advantages of energy costs, because it can be operated at a low temperature compared to conventional sintering processes. Since the hydrothermal process uses H2O to fabricate ceramic materials, it can be regarded as energy-saving, eco-friendly, and spontaneous materials processing. In the present study, we introduce some applications of hydrothermal treatments to slag / glass to produce functional porous ceramic materials.
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Authors: Takeshi Yoshikawa, Sakiko Kawanishi, Kazuki Morita, Toshihiro Tanaka
Abstract: This paper describes the solution growth of SiC by a temperature difference method using an Fe-Si solvent. Crystal growth of SiC from an Fe-40 mol%Si solvent onto a seed wafer of 6H-SiC or 4H-SiC was carried out at 1623 – 1723 K under induction heating. Homo-epitaxial growth on both 6H-SiC and 4H-SiC was identified by Raman spectroscopy, and the SiC growth rate was found to be 90 – 260 μm/h. Experiments were also conducted under resistance heating at 1623 K using conditions which suppressed natural convection. Convective mass transfer in the solution was found to be important for rapid growth of SiC.
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Authors: Joon Ho Lee, Hiromichi Ishimura, Toshihiro Tanaka
Abstract: The contact angle in microscopic size is considered not always to be equal to that in macroscopic size. Recently, the authors [1] have investigated the contact angle of liquid Au on solid Al2O3 by using a micro-scale wetting method. In that research, however, it was very difficult to get clear information of the contact area. Therefore, the measurements showed considerably large scatter. In this study, a new method with a confocal scanning laser microscope utilizing He-Ne laser beam of 632.8nm and 1.5mW was employed to determine the contact angle in microscopic size. A small piece of gold particle was placed on a solid Al2O3 single crystal substrate which was polished to have the roughness of less than 0.1nm. With flowing a highly purified Ar gas, the sample was heated to 1373K. When the sample was melted to form a liquid drop of spherical shape, the height and width of the gold drop was measured by the confocal scanning laser microscope. The contact angle was then evaluated from the relationship between the height and width of the drop. [1] By applying this method, the contact angle of liquid Au of 100 µm in radius on solid Al2O3 single crystal of (0001) facet was estimated to be 134 ± 3o. This result is almost the same as that (133~134o) by using the micro-scale wetting method.
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Authors: Toshihiro Tanaka
Abstract: The authors have evaluated the surface properties as well as phase diagrams of alloys on the basis of thermodynamic databases. Extending these techniques, we developed a new system to estimate phase equilibria of metals and alloys in small particle systems. The present paper describes our trial to evaluate the phase diagrams of binary alloys in nano-sized particle systems through thermodynamic databases.
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Authors: Nobuyuki Takahira, Takeshi Yoshikawa, Toshihiro Tanaka
Abstract: Unusual wetting behavior of liquid Cu was found on a surface-oxidized iron substrate in reducing atmosphere. Liquid Cu wetted and spread very widely on the iron substrate when a droplet was attached with the substrate in Ar-10%H2 after the surface oxidation of the substrate. The oxidationreduction process fabricates a porous layer at the surface of the iron substrate. The pores in the porous iron layer are 3-dimensionally interconnected. Thus, liquid metals, which are contacted with the reduced iron samples, penetrate into these pores by capillary force to cause the unusual wetting behavior. It has been already confirmed that liquid Ag, Sn, In and Bi show this phenomenon onto surface-porous iron samples as well as liquid Cu. This unusual wetting behavior of a liquid metal has been correlated to the normal contact angle of the liquid metal on a flat iron substrate.
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