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  • 1
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract An experimental study has been made of the limiting pulse current density for a periodic pulse reversal plating of copper on a rotating disc electrode from an acidic copper sulfate bath containing 0.05m CuSO4 and 0.5M H2SO4. The measurements were made over a range of the electrode rotational speeds of 400–2500 r.p.m., pulse periods of 1–100 ms, cathodic duty cycles of 0.25–0.9, and dimension-less anodic pulse reversal current densities of 0 to 50. The experimental limiting pulse current data were compared to the theoretical prediction of Chin's mass transfer model. A satisfactory agreement was obtained over the range of a dimensionless pulse period ofDT/δ 2=0.001−1; the root mean square deviation between the theory and 128 experimental data points was ±8.5%.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A transit time method on a rotating ring-disc electrode was used to simultaneously determine the diffusivity and solubility of oxygen in phosphoric acid. The method consisted of measuring the limiting current for the diffusion of dissolved oxygen on the central disc electrode, and a transit time for the diffusion of oxygen from the disc to the ring electrode. The diffusivity of oxygen was calculated from the measured transit time, electrode rotational speed and kinematic viscosity of the electrolyte without the need of its bulk concentration and the number of electrons transferred in the electrode reaction. Once the diffusivity was known, the solubility of oxygen in the bulk electrolyte was determined from the limiting current on the disc using the Levich equation. This work has demonstrated that the transit method is a swift and reproducible technique for the diffusivity measurement. The diffusivity and solubility of oxygen in phosphoric acid of a concentration range of 0.79–14.7m were determined at 23° C and an oxygen partial pressure of 1 atm. A set of empirical equations are presented to correlate the Stokes-Einstein constant,Dµ/T, and solubility of oxygen to the phosphoric acid concentration.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A study has been made of the transpassive dissolution of mild steel in sodium nitrate solution over a range of current densities from 2 to 100 A cm−2. The dissolution current efficiency and the anode potential free from the electrolyte IR component were measured in a flow cell; optical and scanning electron microscopy were then used to examine the sample surfaces after the dissolution tests. The results show that during the early stage of transpassive dissolution, the mild steel is covered with a compact, electronically conductive Fe3O4 film, and the current is consumed mainly in oxygen generation on the film/electrolyte interface. With increasing anode potential and current density, this film is gradually broken and the underlying metal surface becomes exposed to the electrolyte. At this stage, iron dissolution begins at a high rate. The film rupturing process is strongly dependent on nitrate concentration; the higher this is, the lower is the current density required to rupture the film.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract A mathematical model is presented for the optimization of the hydrogen-chlorine energy storage system. Numerical calculations have been made for a 20 MW plant being operated with a cycle of 10 h charge and 10h discharge. Optimal operating parameters, such as electrolyte concentration, cell temperature and current densities, are determined to minimize the investment of capital equipment.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied electrochemistry 18 (1988), S. 831-838 
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The corrosion of nickel under the influence of alternating current (a.c.) in pH 1–7 Na2SO4 solutions has been investigated with an alternating voltage (a.v.) modulation technique. The anodic polarization curves and pitting behaviour of nickel were examined with the superimposition of sinusoidal, square, and triangular a.v. over a range of a.v. magnitudes of 0–5000m V r.m.s., and a.v. frequencies of 20–5000 Hz. It was found that a.v. reduced the passive d.c. potential regime by increasing the critical current density prior to passivation and by shifting the active-passive transitional potential toward the positive direction. In acidic sulphate solutions, a.v. increased the current density in the passive regime in a way similar to the addition of chloride ions. A.v. destroyed the passivity and enhanced the pitting corrosion of nickel at both the passive and transpassive d.c. potentials. The passivity of nickel was destroyed regardless of the a.v. waveforms. Triangular a.v. caused the severest destruction of passivity; this was followed by sinusoidal and square wave a.v.
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  • 6
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The loss of hydroxyl ions by diffusion and back migration to the anolyte compartment is the major source of efficiency loss in a chlor-alkali diaphragm cell. The transfer rate of hydroxyl ions across the diaphragm depends on diaphragm properties and electrolyte flow rate inside the diaphragm. This work examines the concentration distribution of hydroxyl ions across the diaphragm in a laboratory cell. A numerical computation is carried out to optimize the diaphragm structure and current density based on the minimum production cost of chlorine. The optimum current density is found to be 50% lower than the present operating current density in the chlor-alkali industry.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Electroanalytical Chemistry 160 (1984), S. 79-102 
    ISSN: 0368-1874
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 30 (1984), S. 765-769 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental study has been made for laminar mass transfer to a rotating disk and a rotating hemispherical electrode when sinusoidal alternating current (AC) together with direct current (DC) are flowing across the electrode/electrolyte interface. A resistor-capacitor circuit was used to measure the phase shift between the applied AC and the resulting periodical concentration overpotential. The limiting AC current density corresponding to a zero instantaneous surface concentration was determined as a function of AC frequency and DC current density. The experimental data agreed with the theoretical calculations in a regime of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 1 and less than 200.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A film model is presented for the analysis of mass transfer to a rotating hemispherical electrode when sinusoidal alternating current (AC) together with direct current (DC) are flowing across the electrode surface. The concentration of a diffusing ion is separated into two independent components: a constant DC component and a periodic AC component. The DC concentration is obtained by solving the steady-state convective mass transport equation with the perturbation method. The periodic AC concentration distribution is analyzed by the solution to the one-dimensional transient diffusion equation based on the concept of Nernst diffusion layer. The limiting AC current densities corresponding to a zero surface concentration of a reactive ion are investigated for various DC current densities and AC frequencies. The resulting periodic concentration overpotential wave and its phase shift with respect to the applied AC are examined. A comparison with a previous rigorous model indicates that the film model is a good approximation to the mass transfer calculation in the regimes of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 2 and less than 0.01.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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