Application of Magnetohydrodynamic Effect to the Analysis of Electrochemical Reactions 2．Diffusion Process in MHD Forced Flow of Electrolyte Solutions

Aogaki, Ryoichi; Fueki, Kazuo; Mukaibô, Takashi

doi:10.5796/kogyobutsurikagaku.43.509

Cited by 99 publications

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“…For studying the mass transport in the MHD flow, MHD impedance technique has been developed by Olivier et al 21 22 , which is based on the frequency response of limiting currents observed in the presence of sinusoidally excited magnetic fields. An application of the MHD flow in a parallel magnetic field led to the development of MHD-pumping electrode cells called MHD electrode (Aogaki et al ) 23 , where the concentration distribution, modeled by the classical convective diffusion equation, reduces to the simple form of the limiting diffusion current i L = kB 1/3 , where k is a constant, and B is the applied magnetic flux density. In a viscous flow in a narrow channel 24 , i L is proportional to B 1/2 .…”

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confidence: 99%

Lifetime of Ionic Vacancy Created in Redox Electrode Reaction Measured by Cyclotron MHD Electrode

Sugiyama

Morimoto²,

Osaka

et al. 2016

Sci Rep

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The lifetimes of ionic vacancies created in ferricyanide-ferrocyanide redox reaction have been first measured by means of cyclotron magnetohydrodynamic electrode, which is composed of coaxial cylinders partly exposed as electrodes and placed vertically in an electrolytic solution under a vertical magnetic field, so that induced Lorentz force makes ionic vacancies circulate together with the solution along the circumferences. At low magnetic fields, due to low velocities, ionic vacancies once created become extinct on the way of returning, whereas at high magnetic fields, in enhanced velocities, they can come back to their initial birthplaces. Detecting the difference between these two states, we can measure the lifetime of ionic vacancy. As a result, the lifetimes of ionic vacancies created in the oxidation and reduction are the same, and the intrinsic lifetime is 1.25 s, and the formation time of nanobubble from the collision of ionic vacancies is 6.5 ms.

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confidence: 99%

Lifetime of Ionic Vacancy Created in Redox Electrode Reaction Measured by Cyclotron MHD Electrode

Sugiyama

Morimoto²,

Osaka

et al. 2016

Sci Rep

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“…Although the dawn of magnetoelectrolysis was Faraday's unsuccessful attempt in 1832 to detect a potential difference across the river Thames due to its flow in the Earth's magnetic field 17 , most of the results have been generated since the 1970s. Several works emphasize the effect of a magnetic field on mass transport and explain the effect by two different forces: The Lorentz force 11,13,[18][19][20][21][22][23][24][25] and the Kelvin (or field gradient) force 12,[26][27][28] . The former is due to the interaction of the magnetic field with the electric currents flowing in the electrolyte, while the latter depends on the magnetic properties of the electrodes and the species dissolved in the electrolyte.…”

Section: Magnetic Forces In Electrochemical Systemsmentioning

confidence: 99%

Effect of a Uniform Magnetic Field on Corrosion of Ni-Al Bronze in 3.5 wt% NaCl

Krogstad¹,

Johnsen²,

Coey

2017

Corrosion

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Following the observation of enhanced corrosion of parts of a seawaterimmersed permanent magnet motor made from Ni-Al bronze, a laboratory study of the effect of uniform magnetic field on the corrosion of this alloy in a 3.5 wt% NaCl solution has been carried out. The results have been compared with measurements of enhanced convection with a rotating disc electrode. The largest effect of the magnetic field was an enhancement of the anodic current density of 52 % in a field of 800 mT. This enhancement was equivalent to that due to gentle stirring with the rotating disc electrode with diameter 10 mm at 20 rpm. The increase in corrosion current varied with the magnitude of both the magnetic field and the initial corrosion current, and increased with both. The effect can be explained in terms of the Lorentz force, and modelling was performed to quantify the flow induced in the electrolyte by this force.

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“…Lorentz force induces a solution flow called MHD flow promoting mass transport of ions. For the MHD flow in a parallel magnetic field, MHD-pumping electrode cell called MHD electrode (MHDE) was developed 22 – 24 , where the velocity and concentration distribution reduce to the simple equations of the velocity and diffusion current, which provides excellent agreement between theory and experimental result 16 . A notable advantage of this type of electrode lies in the practical possibility of using very small cells without mechanical means.…”

Section: Introductionmentioning

confidence: 99%

Excess heat production in the redox couple reaction of ferricyanide and ferrocyanide

Sugiyama

Miura

Oshikiri

et al. 2020

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In order to establish the universality of the excess heat production in electrochemical reaction, under a high magnetic field, as one of the most fundamental electrochemical reactions, the case of ferricyanide-ferrocyanide redox reaction was examined, where ionic vacancies with ± 1 unit charge were collided by means of magnetohydrodynamic (MHD) flow. As a result, from the pair annihilation of the vacancies with opposite signs, beyond 7 T, excess heat production up to 25 kJ·mol−1 in average at 15 T was observed, which was attributed to the liberation of the solvation energy stored in a pair of the vacancy cores with a 0.32 nm radius, i.e., 112 kJ·mol−1. Difference between the observed and expected energies comes from the small collision efficiency of 0.22 due to small radius of the vacancy core. Ionic vacancy initially created as a by-product of electrode reaction is unstable in solution phase, stabilized by releasing solvation energy. Ionic vacancy utilizes the energy to enlarge the core and stores the energy in it. As a result, solvated ionic vacancy consists of a polarized free space of the enlarged core surrounded by oppositely charged ionic cloud. The accuracy and precision of the measured values were ascertained by in situ standard additive method.

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Application of Magnetohydrodynamic Effect to the Analysis of Electrochemical Reactions 2．Diffusion Process in MHD Forced Flow of Electrolyte Solutions

Cited by 99 publications

References 0 publications

Lifetime of Ionic Vacancy Created in Redox Electrode Reaction Measured by Cyclotron MHD Electrode

Lifetime of Ionic Vacancy Created in Redox Electrode Reaction Measured by Cyclotron MHD Electrode

Effect of a Uniform Magnetic Field on Corrosion of Ni-Al Bronze in 3.5 wt% NaCl

Excess heat production in the redox couple reaction of ferricyanide and ferrocyanide

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