Mathematical modeling of the influence of non-catalytic dissociation / recombination of water molecules in the desalination channel on electric convection

The article formulates a two-dimensional mathematical model of non-stationary transport of 1: 1 electrolyte in a potentiodynamic mode, taking into account electroconvection and non-catalytic dissociation / recombination reaction of water molecules in electromembrane systems, which are considered as the desalting channel of an electrodialysis device. The model is described by a system of coupled Navier-Stokes and Nernst-Planck-Poisson equations taking into account the electric force and physically justified boundary conditions. The article establishes the basic laws of mass transport, taking into account the dissociation / recombination of water molecules. It was shown for the first time that a double electric layer of hydrogen and hydroxyl ions arises in the recombination region. It is shown that between the region of recombination and quasi-equilibrium regions of space charge there are regions of electroneutrality and equilibrium with an almost linear distribution of concentrations. It was found that even under prelimiting, but close enough to the limiting current, modes, non-catalytic dissociation of water molecules in the quasi-equilibrium region of space charge occurs so intensely that the concentration of hydrogen and hydroxyl ions becomes comparable to the concentration of potassium and chlorine ions. At overlimiting current densities, due to the appearance of an extended space charge region and intense dissociation of water molecules in this region, as well as an increase in the electric double layer in the recombination region, the space charge and the dissociation / recombination reaction of water molecules significantly affect each other. In turn, this has a decisive effect on electroconvection and, accordingly, on the transport of salt ions.

Impedance spectroscopy of capacitor systems based on saccharide-derived porous carbon materials.

The electrochemical processes in capacitor systems based on porous carbon materials (PCMs) derived from glucose, lactose, and saccharose at activation temperature of 800 and 1000°C are explored using impedance spectroscopy method. An equivalent electric circuit, which allows modeling of the impedance spectra in the frequency range from 10-2 to 105 Hz, is proposed, and a physical interpretation of each element of the electrical circuit is presented. It is set that in capacitor systems on the basis of the explored materials the accumulation of capacitance occurs due to the formation of a double electric layer at the electrode/electrolyte boundary, and Faradaic processes are minimized. The specific capacity of supercapacitors based on PCMs obtained at 800°C is 91-154 F/g due to the developed microporous structure of materials.

A Potential-Induced Transformation in the Double Electrical Layer on the Rhenium Electrode in Alkali Chloride Melts

Structural transformations in the adsorption layer caused by an electric potential are investigated using the experimental data on the capacitance of a double electric layer for a rhenium electrode in molten sodium, potassium and cesium chlorides at 1093 K. Likening the double electric layer to a flat capacitor, as well as the effective length of the shielding of the electrode charge and changes in the charge sign depending on the applied potential are estimated. It is found that near the minimum potential of the capacitance curve, the shielding length decreases proportionally to the square of the potential due to the deformation of the double layer. The deformation reaches critical values at the potentials of −0.65, −0.38 and −0.40 V for the Re|NaCl, Re|KCl and Re|CsCl systems respectively, and decreases sharply at more positive potentials. The analysis of the dependence of the charge density on the electrode revealed the effect of shielding of potential-induced rhenium cations by salt phase anions. The strong Raman-active Re–Cl stretching mode was observed at 292 cm−1. This can be explained by the transfer of anions across the interface resulting in the formation of ordered layers of ion associations (possibly, ReXn(n − 1)−) on a positively charged surface.

Modeling and investigating of the influence of surface roughness on the strength of electrically conductive fiber

In the framework of the model of locally inhomogeneous electrically conductive nonferromagnetic solid, the near-surface inhomogeneity in a solid cylinder is investigated. It is shown that such inhomogeneity is characterized by three characteristic sizes associated with the structural inhomogeneity of the material, the roughness of the real surface and the electronic subsystem. The charge distribution features a double electric layer. The size effect of fiber strength and its dependence on geometric inhomogeneity parameters of the surface are studied.

Application of the STRESS TEST Method for Quality Control of Electrolytic Capacitors and Capacitors with a Double Electric Layer

В статье рассматривается проблема подтверждения длительной безотказности современного конденсаторостроения в короткие сроки, а именно, оксидно-электролитических алюминиевых конденсаторов, танталовых объемно-пористых конденсаторов и конденсаторов с двойным электрическим слоем. Особое внимание уделяется эксплуатационным параметрам конденсаторов - емкости и эквивалентному последовательному сопротивлению. Проведено исследование длительной безотказности оксидно-электролитических алюминиевых конденсаторов (3000 ч), танталовых объемно-пористых конденсаторов (24 000 ч) и конденсаторов с двойным электрическим слоем (600 ч), получены статистические данные распределения емкости и эквивалентного последовательного сопротивления. Для уменьшения времени испытаний на длительную безотказность был использован ускоренный метод испытаний на надежность стресс-теста. Анализ результатов испытаний конденсаторов на длительную безотказность и методом «Стресс-тест» показал, что применение метода «Стресс-тест» допустимо при испытании объемно-пористых танталовых конденсаторов и оксидно-электролитических алюминиевых конденсаторов, так как прослеживается аналогичный характер изменения электрических параметров, как после проведения испытаний на длительную безотказность. Однако применение метода «Стресс-тест» для конденсаторов с двойным электрическим слоем не представляется возможным в связи с отличной структурой и требует дополнительного подбора режимов проведения испытаний.

Hydrodynamic Aspects of High-Voltage Infiltration Nanogenerator

The hydrodynamic aspects of functioning of a high-voltage infiltration nanogenerator employing the potential energy of a liquid entering a glass filter are discussed. This energy transforms into the electric energy due to the formation of a double electric layer owing to the triboeleсtrization effect during infiltration of the dielectric liquid through the porous structure. To solve the emerged problems, in the equations of a hydrodynamic flow along the infiltration path two local effective parameters were introduced: a mechanic density and dynamic viscosity. The working equations for the motion of the liquid were derived; their solutions for the velocity and the flow rate determining the electric characteristics of a nano-generator, the electric charge and potential as well as their physical relationships were obtained.

Adsorption Characteristics of Stone-Bentonite Mixtures towards Zn: Equilibrium and Kinetic Tests

In the treatment of industrial polluted sites and the construction of landfill sites, anti-pollution barriers are usually used to prevent the diffusion of pollutants. In this paper, the adsorption characteristics of Zn ions by the rock-bentonite anti-pollution barrier were observed by means of static equilibrium and dynamic adsorption tests. The experimental results showed that the adsorption of Zn by stone chips—bentonite was close to the nonlinear Freundlich and Langmuir models. When the concentration of Zn ion is constant, the adsorption capacity increases with the increase in temperature. At a certain temperature, the adsorption removal rate decreases with the increase in concentration. Further study found that the adsorption of Zn from mixed soil was mainly an ion exchange process, and the adsorption mode of Zn from mixed soil was controlled by both intra-particle diffusion and membrane diffusion. Zeta potential, X-ray diffraction (XRD) and The Fourier Transform Infrared spectroscopy (FTIR) showed that with the increase in concentration, the mixed soil adsorbed more metal ions, and the thickness of the double electric layer decreased. Moreover, the adsorption of Zn2+ by bentonite was mainly interlayer adsorption and ion exchange. As an anti-pollution barrier material, the mixed soil of stone chips -bentonite can prevent the diffusion of pollutants, which has certain reference significance for engineering construction.

ABOUT THE REASONS FOR THE CHANGE IN THE MECHANICAL PROPERTIES OF PAPER ASHLESS FILTERS DURING THEIR PROCESSING IN A UNIPOLAR CORONA DISCHARGE

The article presents the study results of the structure and properties of paper ashless filters "Blue tape". It is shown that the "Blue tape" filter paper has a fairly high density with a relatively small number and size of voids (pores) between the fibers. When processing filters in the corona discharge field, an increase in their mechanical properties by 3.5–6% is observed, this is mainly due to the strengthening of the interfiber bond forces. The implementation of increased electrostatic bonding forces in the sheet structure leads to an increase in the resistance to the external tensile force necessary to break the paper filter. The observed dependences are associated with the orientation and ordering of the pulp and paper material structural elements, with an increase in the potential of the double electric layer on the fibers surface under the charge action carriers injected into the paper volume from the corona discharge and with the formation of a hetero charge due to the orientation of the polar cellulose groups and macromolecule segments during electreting. This is confirmed by the increase in the ζ – potential of the fibers of filters during processing in a negative corona discharge - it was found that the zeta – potential value of electret ashless filters is 18% higher than for the initial ones. The achieved results of increasing the ashless filters physico- mechanical properties will increase the efficiency of their use.

The Relation Between Ejection Mechanism and Ion Abundance in the Electric Double Layer of Drops

The composition of outer drop layers has been associated with distinct chemical reactivity. We use atomistic modeling to examine how the composition of the surface excess charge layer (SECL) is related to the ejection mechanisms of ions. Even though the drop disintegration is inherently a non-equilibrium process we find that the equilibrium ion distribution in SECL predicts the ions that are ejected. The escape of the ions in aqueous drops takes place from conical protrusions that are global drop deformations and their appearance is independent of the location of a single ion. Our results are consistent with the equilibrium partition model, which associates the mass spectrum with the distribution of analytes in the drop’s double electric layer. We present evidence that atomistic simulations of minute nano-drops cannot distinguish Rayleigh fission from the ion evaporation mechanism.

Effect of electro-kinetic processes on filtration of fluids and gas in porous medium

The paper reviews the fluid and gas flow in the porous medium considering electro-kinetic phenomena – electro-phoresis and electro-osmosis, as well as the charges associated with them. These phenomena are due to the double electric layer on the border of division of disperse system phases. Electro-kinetic phenomena are follows: electro-phoresis, electro-osmosis, flow potential (Quincke effect) and sedimentation potential (Dorn effect). The formulas for the motion of fluid and gas in porous medium considering the properties of porous medium and saturating them fluids, as well as the interaction between them, which is described with electro-kinematic phenomena, have been obtained. Obtained formulas have been evaluated via the results of laboratory researches.