Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 70 , Issue 4
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Technical Papers
  • Xiaoge WANG, Nobuyoshi NAKAGAWA, Kunio KATO
    2002 Volume 70 Issue 4 Pages 252-257
    Published: April 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    To improve anode performance for a Solid Oxide Fuel Cell (SOFC) at medium temperature (923-1073 K), an interlayer of samaria doped ceria (SDC) is inserted between the Ni anode and the YSZ (Yttria Stabilized Zirconia) electrolyte by RF magnetron sputtering. Great reduction in anode overpotential with the interlayer is confirmed using both ac impedance and dc current interruption. The anodic interfacial conductivity, which is obtained from the complex impedance plot measured under equilibrium potential can be increased by two orders of magnitude by inserting a 2∼3 µm-thick SDC layer. This study proposes an appropriate model for the anodic reaction at this kind of multi-layer anode and discusses the mechanism for performance improvement due to insertion of the SDC interlayer. The results suggest that the SDC mixed conductivity helps to create more active reaction sites within a certain thickness in the SDC layer.

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  • Shinya WATANABE, Izumi KUBO
    2002 Volume 70 Issue 4 Pages 258-263
    Published: April 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Fructose biosensor based on D-Fructose dehydrogenase (FDH) was developed with use of tris (1,10-phenanthroline) cobalt (II) complex (Co(phen)32+) as a redox mediator. Co(phen)32+ could be prepared easily and was oxidized reversibly at low potential. For the immobilization of FDH, a gold electrode was modified through chemisorption of cystamine. FDH was covalently bound to self-assembled monolayer of cystamine by cross-linking amino groups of cystamine and FDH molecule using glutaraldehyde. With use of Co(phen)32+ as a redox mediator, the catalytic current of the FDH-modified gold electrode increased by the addition of D-fructose. In the immobilization procedure, 0.2 mg/ml of FDH resulted in the largest catalytic response among other concentration of FDH. The best sensitivity of the sensor was obtained at pH 7.0 and 35°C. The calibration curve exhibits a linear relationship between 10 and 110 µM with a correlation coefficient of 0.971 and the relative standard deviation of 0.57% (n = 3).

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  • Yoshiyuki MIWA, Hiromori TSUTSUMI, Tsutomu OISHI
    2002 Volume 70 Issue 4 Pages 264-269
    Published: April 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    New types of polymer electrolytes were prepared by cationic ring-opening copolymerization of bis-oxetane (R-O-(CH2CH2O)m-R, R = 3-ethyl-3-methylene oxetane unit, DDOE (m = 2), TrDOE (m = 3), TeDOE (m = 4)) and mono-oxetane (R-O-(CH2CH2O)n-CH3, TrMOE (n = 3), NoMOE (n = 9), DoMOE (n = 12)) with lithium salts as a catalyst, and were characterized by differential scanning calorimetry (DSC) and alternating impedance spectroscopy. The poly(oxetane)-based electrolytes had cross-linked networks with oligo(ethylene oxide) and 2-ethyltrimethylene oxide main chains and methoxyoligo(ethylene oxide) side chains. The polymer electrolytes prepared with LiBF4 revealed high conductivity, compared to those done with LiPF6 or LiN(C2F5SO2)2. The conductivities of the poly(oxetane)-LiBF4 complexes depended on the mono-oxetane content and the length of oligo(ethylene oxide) in the mono- and bis-oxetanes. The oligo(ethylene oxide) side chains in the complexes acted as efficient plasticizing agents, particularly using NoMOE or DoMOE. Maximum conductivities of the polymer electrolytes with LiBF4([Li]/[O] = 0.045) revealed 9.1 × 10−6 (TrMOE/DDOE mole ratio = 3.0) and 1.0 × 10−4 S cm−1 (NoMOE/DDOE = 1.72 and DoMOE/DDOE = 1.29).

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Note
  • Osamu YAGI
    2002 Volume 70 Issue 4 Pages 270-273
    Published: April 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A sol-gel method was used for manufacturing silica glass. A new method involved making a bulk by hardening a slurry of silica powder with a methoxysilane-derived binder. The bulk manufactured by this method was successfully dried and sintered to produce the silica glass. The significant results of this method are as follows: (1) the amount of reaction water in synthesizing the binder was less than the amount with which the methoxy group in the methoxysilane was completely hydrolyzed and poly-condensed, (2) the methoxy group partially survived in the binder and (3) this survival caused the binder to be flexible. When an oligomer of tetramethoxysilane was used as a starting material, the optimum amount of water for the bulk manufacturing is 2.3 equivalents. The bulk manufactured by this method was dried and sintered to form the purified silica glass without the generation of cracks.

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