Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 71 , Issue 5
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  • Yasushi UEBOU, Shigeto OKADA, Jun-ichi YAMAKI
    2003 Volume 71 Issue 5 Pages 308-312
    Published: May 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    Lithium and sodium insertions into pyrophosphates MP2O7 (M = Mo, W) were investigated electrochemically as possible cathodes for ion-transfer batteries. Lithium and sodium were reversibly incorporated in the 3D-framework of pyrophosphates MP2O7 (M = Mo, W) with liquid organic electrolytes at room temperature. The first discharge capacities were 95 mAhg−1 for A1.0MoP2O7 (A = Li, Na) and 295 mAhg−1 for A4.0WP2O7 (A = Li, Na), respectively. The guest (Li or Na) insertion into WP2O7 induced a transition to the amorphous phase, whereas the insertion into MoP2O7 proceeded topotactically with a smooth single phase reaction.

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  • Yusuke AYATO, Tatsuhiro OKADA, Yohtaro YAMAZAKI
    2003 Volume 71 Issue 5 Pages 313-317
    Published: May 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    A new polymer electrolyte fuel cell with a bipolar membrane was proposed with a view to increasing the performance of low temperature PEFCs. The bipolar membrane consists of an acid and a basic ion-exchange layers. The acid layer contacts to the anode and the basic layer contacts to the cathode. The observed open circuit voltage with the proposed cell was 0.882 V. The result implies that the modification of a bipolar membrane fuel cell may leads to a high performance fuel cell. It was observed that the OH ion conductivity with a basic ion-exchange membrane Neosepta was comparable to the conductivity of H+ in Nafion membrane. In the bipolar membrane, however, the measured conductivity was 1 order lower than that of Nafion membrane. This result would be caused by the existence of a resistance layer between the acid and the basic polymer layers. The polarization characteristics were measured by considering the MEA preparation methods. We achieved the polarization performance for the bipolar electrolyte fuel cell using screen-printing MEA preparation method. The highest power density was 0.026 W cm−2.

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  • Tetsuya IWAGISHI, Kumi SAWADA, Hiroaki YAMAMOTO, Koichiro KOYAMA, Hiro ...
    2003 Volume 71 Issue 5 Pages 318-321
    Published: May 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    The electrodepositon of Zn-Mg alloys was tried by potentiostatic electrolysis and cathodic polarization in Lewis basic 1-ethyl-3-methylimidazorium bromide (EMIB)-ZnBr2-MgBr2-ethylene glycol molten salts at 120°C. The molten salts used were prepared by chemical displacement of prescribed amounts of Zn in EMIB-ZnBr2-EG molten salts by Mg. The cathodic polariozation curves showed that EMI cation in the molten salt decomposed below −0.8 V (vs. Zn/EMIB-ZnBr2-EG (45 : 10 : 45 mol%)). Thus the potentiosatatic electrolysis was carried out at −0.6 V and grayish metallic-colored electrodeposits were obtained. The X-ray diffraction analysis showed the diffraction lines of Mg2Zn11 in addition to Zn, CuZn5 and the substrate Cu. This result indicates the Zn-Mg alloy plating can be done by using EMIB-ZnBr2-MgBr2-EG molten salts. The Mg content in the electrodeposit obtained from the EMIB-ZnBr2-MgBr2-EG (18 : 6 : 4 : 72 mol%) molten salt was 2.5 mol%. Corrosion resistance of Zn-2.5 mol% Mg alloy coating steel was about 13 times compare with that of Zn coating steel in the 5 mass% NaCl aqueous solution at 35 °C.

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  • Norio KANEKO, Yuki SHIRAYA, Susumu ARAI, Naoyuki SHINOHARA
    2003 Volume 71 Issue 5 Pages 322-326
    Published: May 05, 2003
    Released: August 30, 2019
    JOURNALS OPEN ACCESS

    Sn-Ag alloy electroplating for Pb-free solder from acid sulfate baths (2 M H2SO4 + 0.1 M SnSO4 + 0.002 M Ag2SO4 + 0.2 M thiourea) containing N,N-bis(polyoxyethylene)octadecylamine[C18H37N[(CH2CH2O)10H]2 : POOA-10] has been studied by means of various electrochemical methods, scanning electron microscopic observation, X-ray diffractometry, etc. Dendritic electrodeposits were obtained from acid sulfate bath in the absence of organic additives. On the other hand, granular crystals were observed on the whole surface by adding POOA-10. Sn-Ag alloy electrodeposits containing 2.0∼5.0 at%Ag were obtained from acid sulfate baths containing 1 mM POOA-10 under galvanostatic conditions (0.5∼7.0 A/dm2). Ag contents in electrodeposits gradually increased with increasing the current density. Sn-Ag alloy electrodeposits obtained from acid sulfate baths containing 1 mM POOA-10 consist of β-Sn phase and ε (Ag3Sn) phase, and its solidus temperature is 221°C. Wettability of electrodeposited Sn-Ag alloy films was not affected by Ag contents in deposits.

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