Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 67 , Issue 10
Showing 1-14 articles out of 14 articles from the selected issue
  • Yoshiro SAKAI, Masanobu MATSUGUCHI
    1999 Volume 67 Issue 10 Pages 950-956
    Published: October 05, 1999
    Released: November 15, 2019

    Most of the humidity sensors practically used are based on the change in electrical properties of polymers or ceramics with humidity. They are either resistive-type or capacitive-type sensors. Various chemical modifications of polymeric materials have been utilized to improve the properties of sensors such as sensitivity, hysteresis, long-term stability, durability in unfavorable atmospheres such as dewdrops or vapors of volatile organic compounds (VOC), etc. This paper overviews the novel methods of chemical modification which have been proposed by the authors.

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Technical Papers
  • Masayuki ITAGAKI, Naotake HASEBE, Kunihiro WATANABE
    1999 Volume 67 Issue 10 Pages 960-967
    Published: October 05, 1999
    Released: November 15, 2019

    The anodic dissolution mechanism of Fe-Ni alloy was investigated by an electrochemical impedance spectroscopy (EIS). The Fe (II) and Ni(II) dissolved from Fe-Ni alloy electrode were detected simultaneously during the polarization curve measurement by a channel flow electrode system. The preferential dissolution of Fe (II) was observed at low anodic potentials, and the dissolution rate of Fe(II) was controlled by Ni content significantly. Nyquist plot of electrochemical impedance of Fe-Ni alloy electrode shows an inductive semicircle and negative resistance. These unique loci were explained by the formation of adsorbed intermediates Fe(I)ad and Ni(I)ad. The numerical simulation was performed for the experimental results of polarization curves, dissolution currents of Fe (II) and Ni(II) and electrochemical impedance responses. The dissolution mechanism was discussed on the basis of the kinetic parameters obtained by the simulation.

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  • Koh-ichi MARUYAMA, Hiroo NUMATA, Takashi SATO, Osamu NITTONO, Izumi OH ...
    1999 Volume 67 Issue 10 Pages 968-973
    Published: October 05, 1999
    Released: November 15, 2019

    Deposition behavior of electroless Co-B and Co-Fe-B were investigated with respect to the structural and magnetic properties of deposits, using the amorphous ribbon substrates. The catalytic activity sequence of amorphous ribbon electrode for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath without containing the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of substrates. The linearly step of the deposition rate was obtained against the deposition time. And also, the initial deposition potential may determine the structural and magnetic properties of the deposit with thickness of μm order.

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  • Akio TANAKA, Hiroki TAMURA, Ryusaburo FURUICHI
    1999 Volume 67 Issue 10 Pages 974-978
    Published: October 05, 1999
    Released: November 15, 2019

    Lambda-manganese dioxide (λ-MnO2), a spinel-type oxide, has lattice vacancies with a size equal to that of lithium ions, and incorporates lithium ions selectively from aqueous solutions. Oxide surfaces in water are hydroxylated by hydration, and the surface hydroxyl groups adsorb ions non-selectively by ion exchange, interfering with the selective incorporation of lithium ions. In this investigation, the surface hydroxyl groups on λ- MnO2 were determined by the Grignard method as a measure of ion-exchange capacity. The surface hydroxyl site densities obtained were compared with the calculated value for the closest packing of hydroxyl groups, and the formation of hydroxyl groups was explained by neutralization of surface oxide ions by water.

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Technological Report
  • Mitsushi UENO, Hiroyuki OGURA, Tamotsu SHIROGAMI
    1999 Volume 67 Issue 10 Pages 979-984
    Published: October 05, 1999
    Released: November 15, 2019

    Cell voltage shifts with change in partial pressure of oxygen gas in a cathode chamber of a phosphoric acid fuel cell being operated at 197°C and ambient conditions were investigated. An experimental equation on influence of the average oxygen partial pressure on the cell voltage was obtained as shown, ΔV =(0.09+ bi) log(P(O2)/P(O2)*), whereΔV represents the amounts of shifted cell voltage by unit of (V), i is the generating current density (A/cm2), P(O2) is partial pressure (atm) of reacting oxygen gas, P(O2)* is standard partial pressure (atm) of reacting oxygen gas, and b is a constant for the cell. Validity of the equation was confirmed for pressurized operated cell, such as the pressure range up to 7 atm of the air. Also, an experimental equation on influence of gas utilization on the cell voltage shifts was derived as, ΔV=(0.09+bi) log {(P(O2)(ent)/P(O2)*)[2−(s/100)(1−P(O2)(ent)/P] /[2(1 + sP(O2)(ent)/100P] }, where ΔV represents an amount of the cell voltage change, P(O2)(ent) P) is a partial pressure (atm) of oxygen at the entrance of the cathode, s is a rate (%) of gas utilization at the cathode reaction, and P is the operating pressure (atm). Then, description of gas utilization rate is proved very important for presentation of cell performances.

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Special Articles
Chemistry of Supercritical Condition and Its Application to Electrochemical Reactions
Techniques in Electrochemical Measurements