Simulation of field-assisted ion exchange inglass regarding the space-charge density andpseudo-mixed-alkali effect

2021 ◽  
Author(s):  
Daniel Schaeffer ◽  
Daniel Klenkert ◽  
Julian Stauch ◽  
Felix Brand ◽  
Wolfgang Foss ◽  
...  
Keyword(s):  
Ion Exchange ◽  
Charge Density ◽  
Space Charge ◽  
Space Charge Density ◽  
Mixed Alkali ◽  
Mixed Alkali Effect

scholarly journals 1D Mathematical Modelling of Non-Stationary Ion Transfer in the Diffusion Layer Adjacent to an Ion-Exchange Membrane in Galvanostatic Mode

Membranes ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 84 ◽  
Author(s):  
Aminat Uzdenova ◽  
Anna Kovalenko ◽  
Makhamet Urtenov ◽  
Victor Nikonenko
Keyword(s):  
Ion Exchange ◽  
Charge Density ◽  
Space Charge ◽  
Diffusion Layer ◽  
Current Density ◽  
Space Charge Density ◽  
Ion Exchange Membrane ◽  
Quasi Equilibrium ◽  
Ion Transfer ◽  
Exchange Membrane

The use of the Nernst–Planck and Poisson (NPP) equations allows computation of the space charge density near solution/electrode or solution/ion-exchange membrane interface. This is important in modelling ion transfer, especially when taking into account electroconvective transport. The most solutions in literature use the condition setting a potential difference in the system (potentiostatic or potentiodynamic mode). However, very often in practice and experiment (such as chronopotentiometry and voltammetry), the galvanostatic/galvanodynamic mode is applied. In this study, a depleted stagnant diffusion layer adjacent to an ion-exchange membrane is considered. In this article, a new boundary condition is proposed, which sets a total current density, i, via an equation expressing the potential gradient as an explicit function of i. The numerical solution of the problem is compared with an approximate solution, which is obtained by a combination of numerical solution in one part of the diffusion layer (including the electroneutral region and the extended space charge region, zone (I) with an analytical solution in the other part (the quasi-equilibrium electric double layer (EDL), zone (II). It is shown that this approach (called the “zonal” model) allows reducing the computational complexity of the problem tens of times without significant loss of accuracy. An additional simplification is introduced by neglecting the thickness of the quasi-equilibrium EDL in comparison to the diffusion layer thickness (the “simplified” model). For the first time, the distributions of concentrations, space charge density and current density along the distance to an ion-exchange membrane surface are computed as functions of time in galvanostatic mode. The calculation of the transition time, τ, for an ion-exchange membrane agree with an experiment from literature. It is suggested that rapid changes of space charge density, and current density with time and distance, could lead to lateral electroosmotic flows delaying depletion of near-surface solution and increasing τ.

scholarly journals Reconstructing the electrical structure of dust storms from locally observed electric field data

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Huan Zhang ◽  
You-He Zhou
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Space Charge ◽  
Charge Separation ◽  
Field Data ◽  
Space Charge Density ◽  
Dust Storms ◽  
Dust Particles ◽  
Electrical Structure ◽  
Separation Mechanisms

Abstract While the electrification of dust storms is known to substantially affect the lifting and transport of dust particles, the electrical structure of dust storms and its underlying charge separation mechanisms are largely unclear. Here we present an inversion method, which is based on the Tikhonov regularization for inverting the electric field data collected in a near-ground observation array, to reconstruct the space-charge density and electric field in dust storms. After verifying the stability, robustness, and accuracy of the inversion procedure, we find that the reconstructed space-charge density exhibits a universal three-dimensional mosaic pattern of oppositely charged regions, probably due to the charge separation by turbulence. Furthermore, there are significant linear relationships between the reconstructed space-charge densities and measured PM10 dust concentrations at each measurement point, suggesting a multi-point large-scale charge equilibrium phenomenon in dust storms. These findings refine our understanding of charge separation mechanisms and particle transport in dust storms.

Bond metallicity of materials from real space charge density distributions

2009 ◽  
Vol 471 (1-3) ◽  
pp. 174-177 ◽  
Author(s):  
S. Jenkins ◽  
P.W. Ayers ◽  
S.R. Kirk ◽  
P. Mori-Sánchez ◽  
A. Martín Pendás
Keyword(s):  
Charge Density ◽  
Space Charge ◽  
Real Space ◽  
Space Charge Density ◽  
Density Distributions

scholarly journals Studies of an artificially generated electrode effect at ground level

1996 ◽  
Vol 14 (10) ◽  
pp. 1095-1101 ◽  
Author(s):  
E. A. Mareev ◽  
S. Israelsson ◽  
E. Knudsen ◽  
A. V. Kalinin ◽  
M. M. Novozhenov
Keyword(s):  
Wind Speed ◽  
Charge Density ◽  
Space Charge ◽  
Turbulent Mixing ◽  
Ground Surface ◽  
Ground Level ◽  
Space Charge Density ◽  
Experimental Conditions ◽  
Electrical Field Strength ◽  
Electrode Effect

Abstract. The outdoor experiments, using a metallic grid above the ground surface, have yielded well-defined vertical profiles of the space-charge density. The profiles showed strong evidence for the existence of an electrode effect, which could be named the artificial electrode effect and can serve as a very useful and well-controlled model for the study of atmospheric electric processes in the atmospheric surface layer. The build-up or break-down of an electrode-effect layer occurred in a time of the order of 10 s under the experimental conditions realized. The artificially generated electrode effect is dependent on the electrical field strength supplied, wind speed, turbulent mixing and ion mobilities. Wind speed and ion mobility seem to be the dominant factors, defining space-charge density profiles. A theoretical model for the artificial electrode effect has been developed, taking into account turbulent mixing of charged particles in the air flow with the logarithmic profile of the wind velocity. The numerical analysis of the boundary value problem for the two-dimensional equations for the light ion concentrations has been performed. The model presented shows a qualitative agreement of calculated space-charge profiles with measured ones, and explains the dependence of the artificial electrode effect on the dominant control parameters. The limiting conditions for the developed theory are discussed.

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