Electrochemistry
Online ISSN : 2186-2451
Print ISSN : 1344-3542
ISSN-L : 1344-3542
Volume 70 , Issue 5
Showing 1-15 articles out of 15 articles from the selected issue
Vision
Communication
  • Nobuaki MIYAMOTO, Yuichi TAKADA, Shiho MIURA
    2002 Volume 70 Issue 5 Pages 308-310
    Published: May 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Manganese dioxides were prepared from heating manganese(II) acetate and ammonium peroxiodisulfate at 80-200°C for 1 h. The yield of manganese dioxide decreased with the heating temperature (>100°C). After heating at 375°C for 5 h in air, the formation of α-MnO2 and β-MnO2 phases was confirmed by X-ray diffraction. The specific surface areas of the products heated at 375°C were 160-180 m2 g−1. When the products were used as the cathode materials of lithium / manganese oxide cells, the discharge capacities of these cells were 281-287 mAh g−1, which were higher than that of the cell using electrolytic manganese dioxide (210 mAh g−1). It was found that the product obtained by heating at 100°C is hopeful to be used as a cathode material.

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Technical Papers
  • Susumu ARAI, Masanobu KUMAGAI, Norio KANEKO, Naoyuki SHINOHARA
    2002 Volume 70 Issue 5 Pages 311-315
    Published: May 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    Electroless Sn-Ag alloy plating by the displacement reaction was investigated. A new bath containing potassium pyrophosphate, potassium iodide, metal salts, and thiourea was used. First, examinations of electroless Sn plating and electroless Ag plating were carried out, and then electroless Sn-Ag alloy plating was investigated. Anodic and cathodic polarizations were conducted to clarify the deposition mechanism. Sn-Ag alloy films with a range of Ag concentrations from 24 to 52 at.% were obtained. The surface morphology of the films became smoother with decreasing Ag content. The Sn-Ag alloy films consisted of the β-Sn phase and the ε (Ag3Sn) phase.

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  • Yuriy A. TARASENKO, Svitlana A. KOPYL, Vladimir F. LAPKO, Anatoliy A. ...
    2002 Volume 70 Issue 5 Pages 316-321
    Published: May 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    When the grains of an activated carbon (AC) came to contact with deaerated aqueous solution of tetrachloropalladate ions (TCPI), their surface was covered by a thin porous layer of metallic Pd. The deposited Pd remained unchanged for a long time on the grains. In the aerated solution of the same composition two different processes were observed. The first was deposition of a similar layer of metallic Pd on the external surface of the grains, followed by expansion and vanishing of a Pd-containing layer from the surface of the grains into their cores. The second was gradual fixation of Pd atoms on the external and the internal surface of the AC grains by mechanisms other than reduction of TCPI, likely by mechanisms of ion-exchange. The observed two processes were discussed with regards to the chemisorbed oxygen atoms on the external and the internal surface of the AC, which caused change of electrode potential as well as acquisition of ion-exchange ability.

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  • Norio NAKAYAMA
    2002 Volume 70 Issue 5 Pages 322-328
    Published: May 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The inhibitory effects of uracil and its derivatives on the corrosion of a steel used for reinforcement of concrete were investigated by polarization measurements in a saturated Ca(OH)2 solution containing 0.53 mol/dm3 NaCl at pH 12.5, which is a simulated concrete-pore solution, during short-term (7-day) experiments. The inhibition mechanisms were also investigated by surface analyses (FT-IR and XPS). Uracil, 5-nitrouracil, and 5-aminouracil inhibited the corrosion of steel. 5-Aminouracil was the most effective; its inhibition efficiency was more than 98% at concentrations higher than 5.0 × 10−2 mol/dm3 in the solution. 5-Aminouracil was adsorbed onto steel surfaces in accordance with the Langmuir adsorption isotherm. In a NaOH solution containing 0.53 mol/dm3 NaCl at the same pH (12.5), 5-aminouracil did not exhibit any inhibitory effects, which suggests that calcium cations in the solution are indispensable for the inhibitory effect. The FT-IR spectra implied that 5-aminouracil was adsorbed onto iron oxides on the steel surfaces through the formation of a coordination bond with the amino group at position 5 and a coordination or a covalent bond with the carbon at position 6 of the pyrimidine ring. The XPS analysis showed that 5-aminouracil was adsorbed onto the steel surfaces along with calcium.

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Technological Report
  • Shigeo AOYAGI, Masahki MATSUDAIRA, Takahiro SUZUKI, Hajime KATANO, Shi ...
    2002 Volume 70 Issue 5 Pages 329-333
    Published: May 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    A four-electrode electrolytic cell for ion-transfer voltammetry was designed, in which a stationary oil/water interface can be renewed by pouring an aqueous solution from a reservoir. A new four-electrode potentiostat was also developed in order to achieve ideal iR compensation with a positive-feedback circuit. Performance evaluation of the four-electrode system was made through cyclic voltammetric, chronopotentiometric, and normal-pulse voltammetric measurements for the transfer of tetramethylammonium ion at the nitrobenzene/water interface. The developed potentiostat was found to show a proper response, even when nearly 100% (at least 95%) iR compensation was achieved. A low-pass filter mounted in the potentiostat was successfully employed to reduce noise in current signal.

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Note
  • Yukio SASAKI, Hayato MIURA, Kazuhiro TOMINAGA, Noritoshi NANBU
    2002 Volume 70 Issue 5 Pages 334-336
    Published: May 05, 2002
    Released: September 10, 2019
    JOURNALS OPEN ACCESS

    The electrolytic conductivity and charge-discharge characteristics of the lithium electrode were examined in ternary solvent systems made up of an ethylene carbonate (EC)-dimethyl carbonate (DMC) equimolar binary mixture with 3-methylsydnone (3-MSD) and 3-ethylsydnone (3-ESD). The electrolytes used were LiClO4, LiPF6, LiBF4, LiCF3SO3, LiN(CF3SO2)2, and LiN(C2F5SO2)2. The order of the decrease in conductivity of the ternary solvent electrolytes at a mol ratio 0.5 of 3-MSD and 3-ESD was LiPF6>LiClO4>LiN(CF3SO2)2>LiN(C2F5SO2)2>LiBF4>LiCF3SO3. The 1 mol dm3 LiN(CF3SO2)2 and LiN(C2F5SO2)2 electrolytes with large anions showed moderate conductivities of higher than 6-7 mS cm−1 at a mol ratio 0.5 of 3-MSD and 3-ESD. Addition of 3-MSD and 3-ESD to the EC-DMC equimolar binary mixtures containing LiClO4, LiBF4, LiCF3SO3, and LiN(CF3SO2)2 is effective for raising lithium electrode cycling efficiency. We found by using scanning electron microscope (SEM) that the cycling efficiency is dependent on the dendrite formation and the morphology of the film formed on the Ni (working) electrode.

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