TANSO
Online ISSN : 1884-5495
Print ISSN : 0371-5345
ISSN-L : 0371-5345
Volume 2014, Issue 261
Displaying 1-8 of 8 articles from this issue
Preface
Research Papers
  • Motohide Hata, Yoshimasa Amano, Masami Aikawa, Motoi Machida, Fumio Im ...
    Article type: Research Paper
    2014 Volume 2014 Issue 261 Pages 2-7
    Published: January 15, 2014
    Released on J-STAGE: February 15, 2014
    JOURNAL FREE ACCESS
    Mesoporous activated carbons (ACs) were prepared from bamboo by phosphoric acid activation, and the optimum activation conditions such as impregnation ratio (H3PO4/bamboo ratio) and activation temperature were examined. The pore structure of the ACs was determined by N2 adsorption-desorption isotherms. The results showed that the AC prepared using an impregnation ratio of 3 g/g and an activation temperature of 500 °C had the highest mesopore volume of 0.93 cm3/g. For further development of pores in AC, alkali pretreatment of the bamboo by soaking in aqueous sodium hydroxide was conducted and the pretreated bamboo was then activated with phosphoric acid under the optimum conditions. The influences of alkali pretreatment on the components of the raw material and the pore structure of the AC were examined, and the properties of bamboo before and after alkali pretreatment were also evaluated by thermogravimetric analysis and scanning electron microscopy. As a result, the possibility of the elution of hemicellulose and lignin from bamboo by alkali pretreatment was suggested. The AC prepared from alkali-pretreated bamboo had a mesopore volume of as high as 1.50 cm3/g, suggesting that the elution of hemicellulose and lignin from the raw material contributes to the development of mesopores by phosphoric acid activation.
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  • Satoshi Iwasaki, Takahiro Hasegawa, Tomoko Fukuhara, Jun Maruyama
    Article type: Research Paper
    2014 Volume 2014 Issue 261 Pages 8-13
    Published: January 15, 2014
    Released on J-STAGE: February 15, 2014
    JOURNAL FREE ACCESS
    Saw-dust of Japanese cypress, which was often used as a raw material of activated carbon, impregnated with an aqueous solution of halide or organic acid salt was carbonized and the porosities of the carbonized samples were measured. When saw-dust impregnated with potassium or sodium iodide or bromide was carbonized at 800 °C, chemical activation occurred and the carbonized sample had a larger specific surface area than one prepared by normal carbonization without using inorganic compounds. However, no chemical activation was found in the case of magnesium halides and other metal chlorides. In experiments using acetates, potassium caused stronger chemical activation than sodium or magnesium. It was also found that chemical activation did not occur in carbonization at 600 °C and that the chemical activation occurred at a higher carbonization temperature than the melting point of the inorganic compound used. It is therefore believed that the reactivity of the inorganic compound, such as its corrosion of the carbonaceous solid, is intensified by using a higher carbonization temperature than its melting point in order to promote the chemical activation.
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  • Koji Tamada, Kazuto Arimatsu, Akihiko Matsumoto, Tsutomu Takeichi
    Article type: Research Paper
    2014 Volume 2014 Issue 261 Pages 14-18
    Published: January 15, 2014
    Released on J-STAGE: February 15, 2014
    JOURNAL FREE ACCESS
    Carbon films were prepared by the heat-treatment of polyimide (PI) films at different temperatures between 400 °C and 900 °C. Heat-treatment was carried out by two methods (one-step and step-wise methods). In the one-step method, the temperature was increased directly to the pyrolysis temperature. In the step-wise method, the temperature was increased to the pyrolysis temperature in steps of 100 °C. The micropore surface area of the carbon films obtained was estimated from the αs-plots of the nitrogen-adsorption isotherms at -196 °C. In the one-step method, the micropore surface areas of the carbon films heat-treated at 800 °C and 900 °C were 400 m2 g-1 and 600 m2 g-1, respectively. Micropores were not formed for the carbon films heat-treated at 700 °C in the one-step method. On the other hand, in the step-wise method, the micropore surface areas of the carbon films heat-treated at 700 °C, 800 °C and 900 °C were 340 m2 g-1, 440 m2 g-1 and 230 m2 g-1, respectively. These results suggested that heat treatment method largely affects the micropore structure of the carbon films derived from PI.
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Series Lecture
Recent Doctoral Thesis
  • Yoshiaki Sato
    Article type: Recent Doctoral Thesis
    2014 Volume 2014 Issue 261 Pages 29-31
    Published: January 15, 2014
    Released on J-STAGE: February 15, 2014
    JOURNAL RESTRICTED ACCESS
    This thesis is devoted for exploration on various host–guest interactions between graphene and adsorbed molecules, in particular concentrating on oxygen as guest adsorbed molecule which serves not only as electron acceptor but also as molecular magnet with triplet spin (S=1). Through the systematic experimental investigation, it is revealed that oxygen adsorption quite differently affects the electron transport on graphene depending on temperature; at room temperature the charge-transfer doping effect by weakly chemisorbed oxygen is dominant, whereas magnetic interaction between spins of physisorbed oxygen molecules and graphene manifests itself in the low temperature regime below 10 K, leading to anomalous oscillations of magnetoresistance. Furthermore, it is clarified that the oxygen adsorption accompanied with charge-transfer doping significantly depends on the electron/hole concentration of graphene, resulting in unconventional adsorption kinetics as well as modification of adsorption states that can be arbitrarily tuned by application of the external electric field. A phenomenological adsorption kinetics model is proposed on the basis of the electrochemistry in which charge transfer process between graphene and the adsorbed molecules should go through an activation barrier dependent on the Fermi level. Notably, the observed characteristics of adsorption are successfully explained by this model. The consistency between the theoretical model and experiments is also kept in the realistic case of graphene device, on which charge inhomogeneity exists on graphene due to potential fluctuation induced by the supporting substrate of the device or due to charge transfer between metal electrodes and graphene. This thesis contributes novel and interdisciplinary aspects on the surface chemistry and condensed-matter physics in low dimension, imparting strategies to control the electronic properties of graphene by regulation of molecular adsorption.
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