Netsu Sokutei
Online ISSN : 1884-1899
Print ISSN : 0386-2615
ISSN-L : 0386-2615
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Volume 40, Issue 2
Displaying 1-6 of 6 articles from this issue
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Review
  • Microwave Synthesis and Lithium Battery Property of SnO2 Nanocrystalline Ceramics
    Masashi Yoshinaga
    2013 Volume 40 Issue 2 Pages 51-57
    Published: April 25, 2013
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.40.2_51
    JOURNAL FREE ACCESS
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    Lithium-ion battery (LIB) has been used in various mobile devices. From now on, it is expected that LIBs become widely used as APU (Auxiliary Power Unit) for cars and airplanes. Thus, LIBs would require more high lithium storage capacity in future. In this paper, SnO2 with large theoretical capacity was explained. This active material has a problem of poor cyclability. In general, the volume change is moderated by utilizing smaller and more uniform particles for active materials. SnO2 nanoparticles by microwave heating is ultrafine. The sizes of primary particles were estimated to be around 5 nm by transmission electron microscopy and X-ray diffraction. The SnO2 nanoparticles worked as a rechargeable electrode material, and the initial capacity (cut-off voltage: 0.01 V) was 1670 mAh/g. Cyclic voltammetry, X-ray diffraction, and micro-Raman studies elucidated that lithium insertion-deinsertion reaction on the 1st cycle was caused by both redox and alloying-dealloying reactions of Sn, whereas the redox ability of the SnO2 nanoparticles was gradually lost during charge-discharge repetition.
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  • Application of Sonochemistry to Treatment of Water Pollutant
    Keiji Yasuda
    2013 Volume 40 Issue 2 Pages 58-64
    Published: April 25, 2013
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.40.2_58
    JOURNAL FREE ACCESS
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    In pure liquids and solutions, generation and collapse of bubbles caused by ultrasound result in extraordinary high local temperature and pressure. This phenomenon leads to physical and chemical effects called sonochemistry. Sonochemistry are attributed to high temperature and production of OH and H radicals that can decompose different kinds of water pollutant such as chlorinated organic materials, surfactants, polymers and germs. Among the technologies for wastewater treatment, the sonochemical method is very attractive because it is easy and safe to operate, and hardly produces its by-products. Development of a sonochemical reactor with high efficiency is necessary for its practical application. Calorimetry of water is used for evaluating the ultrasound power in the reactor. The sonochemical efficiency is defined as the ratio of number of reacted molecules to ultrasound energy. For small reactors, the sonochemical efficiency has maximum values in the frequency range from 200 to 600 kHz. On the other hand, for large reactors, the sonochemical efficiency depends on the dimensions of the reactor in addition to frequency. Liquid mixing and the superposition of two ultrasonic fields enhance sonochemical reactions. The combination of sonochemical and other oxidation methods is a promising technology of decomposing water pollutants.
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  • Influence of Defect Structure on the Thermal Conduction Characteristic of YSZ Polycrystalline
    Kazuya Sasaki
    2013 Volume 40 Issue 2 Pages 65-70
    Published: April 25, 2013
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.40.2_65
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    Based on author's research data obtained by using microstructure-controlled sintered dense yttria–stabilized zirconia (YSZ) pellets and porous YSZ pellets, influence of defect structure on the thermal conduction characteristic of dense YSZ polycrystalline and porous YSZ polycrystalline is explained. The difference in the specific heat capacity between 3YSZ (Y2O3/ZrO2 = 3/97 (mol)) and 8YSZ (Y2O3/ZrO2 = 8/92 (mol)) is discussed from the point of view of the number of lattice defects introduced to YSZ by doping Y2O3. Thermal diffusivity in a high temperature region and a low temperature region is explained separately, respectively. Contributions of phonon diffusion and photon heat radiation in YSZ grain and pore to temperature dependency of the thermal diffusivity of 3YSZ and 8YSZ are clarified. In order to interpret their contributions, porosity, pore size, and grain–boundary concentration are used as a key factor.
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  • Application of High-Sensitivity DSC for the Study of Thermotropic Liquid Crystalline Materials
    Yuji Sasaki, Kenji Aihara, Haruhiko Yao, Kenji Ema
    2013 Volume 40 Issue 2 Pages 71-77
    Published: April 25, 2013
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.40.2_71
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    We studied thermal behavior of thermotropic liquid crystal materials by a high-sensitivity differential scanning calorimetry. We report the results of precise heat capacity measurements on two types of materials: antiferroelectric liquid crystal and bent-core liquid crystal. In the former case, phase transitions in chiral smectic-C subphases were investigated. It was found that the transitions observed are intrinsically first order with a thermal hysteresis and little thermal fluctuation. The effect of the thermal fluctuation from the smectic-A – smectic-C*α transition on the smectic-C*α – smectic-C* transition was examined. For bent-core liquid crystal, our study focused on the thermal property of the B4 phase exhibiting a novel helical nanofilament structure. A distinctive thermal behavior characterizing the B4 structure was obtained upon cooling. Moreover we investigated a mixture system of bent-core and rodlike molecules involving a nanophase-separated structure due to the asymmetric viscoelastic properties of two components. We show that the technique plays a very powerful role for the study of liquid crystalline systems.
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  • Preparation and Microstructure of Novel Materials using Bacterial Cellulose Gel
    Toru Hoshi, Takashi Sawaguchi, Shoichiro Yano
    2013 Volume 40 Issue 2 Pages 78-85
    Published: April 25, 2013
    Released on J-STAGE: November 20, 2022
    DOIhttps://doi.org/10.11311/jscta.40.2_78
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    Bacterial cellulose (BC), which is produced by Acetobacter xylinum (A. xylinum) in culture, is made up of a three dimensional network of ribbon-shaped bundles of cellulose microfibrils. Recently, novel techniques to prepare shape-controlled BC hydrogels having various shapes such as tubular and hollow sphere have been reported, and are reviewed here. In order to reinforce these BC hydrogels, preparation of BC composites incorporated with hydrophilic polymers or inorganic materials are attempted. For instance, two methods such as so-called culture method and soaking method are adopted. In culture method, A. xylinum is incubated in medium containing dispersoids. In soaking method, BC hydrogel is immersed in e.g. silica sols, then silica particles diffuse into the BC hydrogel and lodge in the spaces between the ribbon-shaped fibrils. If we can use porous BC aerogel, preparation of the hybrids will be readily available. BC hydrogel has three dimensional network of ribbon-shaped fibrils, and pores between the fibrils are filled with water. When the BC hydrogel is dried by using supercritical CO2 fluid, then water in the pores is replaced with CO2 and BC aerogel can be obtained just maintaining the structure in BC hydrogel. In this paper, composite materials using BC aerogel is also reviewed.
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