Concentric Cylindrical Electrodes Research Articles

The effect of the electrodes shape in water electrolysis on the production of hydrogen

This article presents a comparative study of the production of hydrogen by the electrolysis of water using two forms of electrodes; cylindrical and flat. The objective of this comparison is to select the best type of electrolyzer to produce hydrogen for the same volume of water and the same operating voltage. An analytical study and experimental tests were carried out on a cylindrical electrolyser consisting of two concentric cylindrical electrodes separated by a variable thickness e (3.5 mm, 4 mm, 5.5 mm, 8.5 mm and 9 mm), then a flat electrolyser consisting of two flat electrodes spaced by a distance d (2 mm, 4 mm, 6 mm, 10 mm and 15 mm). For each cylindrical electrolyser there corresponds a single electrolyser with flat electrodes. The preliminary study revealed that the production of hydrogen in an electrolyzer is significantly affected by the distance separating the two electrodes and their shapes. Indeed, the comparative electrolysis results show that in each case the electrolyzer with cylindrical electrodes clearly prevails over its counterpart with flat electrodes for the same operating conditions and for the same quantity of water injected into the electrolysis.

Conical face-field electrostatic energy analyzers for investigating nanomaterials

The paper presents numerically calculated models of new electrostatic energy analyzers based on a conical face-field, which is restricted by concentric cylindrical (inner) and truncated-cone (outer) electrodes and two flat boundaries, perpendicular to the axis of symmetry. The calculated analyzers show good enough as energy resolution as well the acceptance characteristics, simple design ( without fringing fields) and provide wide abilities for analyzing surfaces of remote objects of different shape and size. Remote sensing allows use in various applications when is desirable to use a set of methods without mutual interference, what is useful tool's characteristic for investigating nanostructures.

Modelling the Role of the Inner Electrode Radius on the Oxygen Negative Corona Discharge in Coaxial Electrode Geometry

The charge species plays a vital role in changing the field in direct current discharge (DC). This article introduces a numerical modeling in one dimension of the inner electrode diameter of oxygen-fed negative corona discharge in coaxial electrodes geometry. The properties of negative corona plasma in a concentric cylindrical electrodes (wire-cylinder) were simulated by COMSOL Multiphysics software. Various diameters of negative corona electrode, namely 0.01, 0.025, 0.05, 0.075, and 0.125 mm, were applied, ​​where the diameter of the outer cylindrical electrode was taken as 15 mm. The model was run at atmospheric pressure and the applied negative voltage was -10 KV. Moreover, oxygen gas was used to fill the inter-electrodes distance. Furthermore, the spatial distribution of electrons, positive ions, and negative ions as a function of the diameter of negative electrode of the negative corona discharge were investigated. The study also tested the effects of the electrode diameter of the negative corona discharge on ozone generation. The observed decrease in ozone density with the increase in negative electrode diameter was reasonable and consistent with other results provided by researchers in this field.

Numerical investigation of instability and transition to chaos in electro-convection of dielectric liquids between concentric cylinders

The two-dimensional (2D) electro-convection (EC) flow of dielectric liquids between two concentric cylindrical electrodes driven by unipolar injection of ions is investigated numerically. The finite volume method is used to resolve the spatiotemporal distributions of the flow field, electric field, and charge density. The flow transition routes from steady laminar to chaotic flow states are studied in various scenarios where the mobility parameter M of the dielectric liquids varies from 5 to 200. The dynamic characteristics and bifurcation routes of the EC flow depend on the electric Rayleigh number T, a ratio of the electric force to viscous force, and the mobility parameter M. For increasing T, three different transition routes from a convective steady-state to chaos via different intermediate states are observed. The flow states have been quantified by the power spectral density distribution and phase space trajectory of the velocity. The fractal dimensions and Lyapunov exponents are calculated to identify the chaotic flow. The increase in the mobility parameter M leads to a shorter and more direct route with fewer intermediate states when bifurcating to chaos. In addition, the power scale of charge transport that is defined by the electric Nusselt number Ne and T is discussed when the EC flow develops into electro-turbulence.

Feasibility of electrochemical regeneration of activated carbon used in drinking water treatment plant. Reactor configuration design at a pilot scale

This work evaluates the feasibility of electrochemical regeneration of granular activated carbon used in drinking water treatment plants as a real alternative to thermal regeneration. Two pilot-plant-scale reactors, with a capacity of 10−15 kg, have been designed using two different configurations, parallel plate electrodes and concentric cylindrical electrodes. The optimization of the anode material has also been studied and Pt/Ti, RuO2/Ti and IrO2/Ti have been used. After the regeneration and, thus, recovery of the porosity the samples were tested in the adsorption of bisphenol A. In the electrochemical regeneration, recovery of the porosity of spent activated carbon until 100 % and 96 % with respect to the pristine activated carbon using Pt/Ti anode after 3 h of treatment, has been achieved. The regeneration process produces a small increase in the number of surface oxygen groups. No important differences have been observed among the tested anodes and RuO2/Ti and IrO2/Ti can be an economic alternative to Pt/Ti. Bisphenol A adsorption kinetics was slower in regenerated activated carbons probably due to the formation of surface oxygen groups. However, the adsorption capacity was similar in the regenerated samples and the pristine one.

Applying Conformal Mapping to Derive Analytical Solutions of Space-Charge-Limited Current Density for Various Geometries

While exact analytic solutions for space-charge-limited currents (SCLCs) are well-established for parallel plate geometries, they have only recently been derived for concentric cylindrical and spherical geometries using variational calculus (VC). However, actual diode systems and slow-wave structures are usually more complicated, making SCLC calculations more difficult. In this article, we apply conformal mapping to derive the analytical solutions for SCLC for various complicated geometries exhibiting curvilinear flow. We first replicate the exact solution of SCLC for concentric cylindrical electrodes from VC using conformal mapping to transform from the Child-Langmuir (CL) law for a planar geometry. We then derive SCLC in other geometries using conformal transformations to either the planar or the concentric cylinder solution. Because the SCLC calculated using such conformal mappings depends only on the CL law, this may permit future incorporation of relativistic or quantum corrections to determine the appropriate relationships for more complicated geometries.

Simulation of electromagnetic parameters in a laboratory installation

The paper devoted to the numerical simulation of electromagnetic and heat transfer processes in laboratory installation with two concentric cylindrical electrodes and liquid metal. The electromagnetic and temperature fields of laboratory installation are presented. The results obtained for the laboratory installation can be used in the metallurgical industry for the simulation and optimization of electrometallurgical furnaces.

An electrostatic in-line charge-state purification system for multicharged ions in the kiloelectronvolt energy range.

The performance of a newly built omega type electrostatic analyzer designed to act as an in-line charge-state purification system for ions in the kiloelectronvolt energy range is reported. The analyzer consists of a set of four consecutive electrostatic 140° concentric cylindrical electrodes enclosed by Matsuda electrodes. This setup was recently tested and validated using O5+, Ar9+, and Xe20+ ion beams at an energy of 14 qkeV at the ARIBE facility. A resolving power of 10.5 and a transmission of 100% of the desired charge state are measured allowing a good purification of incoming ion beams with charge states up to 10+ and a fairly good purification for charge states at least up to 20+. In comparison with other in-line solutions such as the Wien filter, our system has the advantage of being purely electrostatic and therefore lacking common drawbacks as, for example, hysteresis.

Magneto-Dendrite Effect: Copper Electrodeposition under High Magnetic Field

Ionic vacancy is a by-product in electrochemical reaction, composed of polarized free space of the order of 0.1 nm with a 1 s lifetime, and playing key roles in nano-electrochemical processes. However, its chemical nature has not yet been clarified. In copper electrodeposition under a high magnetic field of 15 T, using a new electrode system called cyclotron magnetohydrodynamic (MHD) electrode (CMHDE) composed of a pair of concentric cylindrical electrodes, we have found an extraordinary dendritic growth with a drastic positive potential shift from hydrogen-gas evolution potential. Dendritic deposition is characterized by the co-deposition of hydrogen molecule, but such a positive potential shift makes hydrogen-gas evolution impossible. However, in the high magnetic field, instead of flat deposit, remarkable dendritic growth emerged. By examining the chemical nature of ionic vacancy, it was concluded that ionic vacancy works on the dendrite formation with the extraordinary potential shift.

Flow electrification characteristics of oil-pressboard insulation under ac superimposed on DC electric field

Converter transformer plays an important role in the HVDC transmission system. The valve side insulation in converter transformer withstands AC superimposed DC electric field during operation. In order to investigate the flow electrification characteristics of oil-paper insulation under the AC superimposed DC electric field, an oil-paper tube model with concentric cylindrical electrode geometry was built in laboratory. Experiment study on flow electrification under DC electric field was carried using the closed oil circulating system, and the influence rule and mechanism of amplitude of AC superimposed DC electric field, the DC component ratio and oil flow velocity on the flow electrification was analyzed. The experiment results demonstrated that influences of oil flow velocity and amplitude of applied voltage on streaming currents were related to temperature. At low temperature the streaming currents increased linearly with flow velocity and amplitude of applied voltage. Increase the DC component ratio enhanced the streaming currents. At high temperature the streaming currents increased exponentially with flow velocity and showed peak effect with amplitude of applied voltage. The peak point voltage decreased with the DC component ratio. The theoretical analysis based on the experiment results demonstrated that ions generation speed at the oil-paper interface depended on the dissipation speed of positive and negative ions. Saturation of negative ions migration current in the paper and leakage current at the outer electrode lead to peak effect of streaming currents. Changing of temperature can influence the flow electrification characteristics by affecting the ions migration speed and the electric field distribution in the insulation.

Linear stability of a circular Couette flow under a radial thermoelectric body force

The stability of the circular Couette flow of a dielectric fluid is analyzed by a linear perturbation theory. The fluid is confined between two concentric cylindrical electrodes of infinite length with only the inner one rotating. A temperature difference and an alternating electric tension are applied to the electrodes to produce a radial dielectrophoretic body force that can induce convection in the fluid. We examine the effects of superposition of this thermoelectric force with the centrifugal force including its thermal variation. The Earth's gravity is neglected to focus on the situations of a vanishing Grashof number such as microgravity conditions. Depending on the electric field strength and of the temperature difference, critical modes are either axisymmetric or nonaxisymmetric, occurring in either stationary or oscillatory states. An energetic analysis is performed to determine the dominant destabilizing mechanism. When the inner cylinder is hotter than the outer one, the circular Couette flow is destabilized by the centrifugal force for weak and moderate electric fields. The critical mode is steady axisymmetric, except for weak fields within a certain range of the Prandtl number and of the radius ratio of the cylinders, where the mode is oscillatory and axisymmetric. The frequency of this oscillatory mode is correlated with a Brunt-Väisälä frequency due to the stratification of both the density and the electric permittivity of the fluid. Under strong electric fields, the destabilization by the dielectrophoretic force is dominant, leading to oscillatory nonaxisymmetric critical modes with a frequency scaled by the frequency of the inner-cylinder rotation. When the outer cylinder is hotter than the inner one, the instability is again driven by the centrifugal force. The critical mode is axisymmetric and either steady under weak electric fields or oscillatory under strong electric fields. The frequency of the oscillatory mode is also correlated with the Brunt-Väisälä frequency.

Numerical simulation of the electro-convective onset and complex flows of dielectric liquid in an annulus

We conducted a numerical study on the onset of electro-convection as well as the complex flow phenomena of dielectric liquid subjected to unipolar autonomous charge injection in the annular gap between two concentric circular cylindrical electrodes. The Nernst-Planck equations governing the charge density transport, the Poisson equation for the electric potential and the Navier-Stokes equations for the fluid flow are solved numerically using the finite volume method. The developed code is validated by comparing the critical stability parameter values for the onset of electro-convection with those obtained from the linear stability analysis. We identify in a parameter space the stable hydrostatic state and the electro-convection state. The electro-convection is again divided into three regimes: stationary, oscillatory and chaotic. For inner cylinder radius ri ≥ 1.0, we observed an increase in the number of charged plumes and vortex pairs with stability parameter T before the electro-convection becomes chaotic. For outer injection, although the onset of electroconvection starts at T higher than the inner injection, the onset of chaotic motion occurs at lower T.

Constraints on the Fe–S melt connectivity in mantle silicates from electrical impedance measurements

The connectivity of FeS melts in olivine and in a fertile peridotite matrix has been addressed through in situ electric impedance spectroscopy (IS) measurements at 1 GPa. A first series of experiments used sintered powder samples of a fertile peridotite xenolith mixed with 5–15 vol.% Fe 70S 30 of eutectic composition. The sheared high-T garnet peridotite with Mg# ∼ 0.90 is composed of 60 vol.% olivine, 15% orthopyroxene, 5.3% clinopyroxene and 19% garnet, the powder grain size was 20–30 μm, similar to the one employed by Yoshino et al. (2003). For a second series, San Carlos olivine aggregates were used as solid matrix and 10–20 vol.% of eutectic Fe 70S 30 were added. For these, the average grain size was 3 μm, much smaller than in the experiments by Yoshino et al. (2003). The powder mixtures of peridotite + Fe 70S 30 and olivine aggregates + Fe 70S 30 were first annealed for 2–5 days in a conventional piston cylinder at 1 GPa and 950–970 °C. The electrical conductivity of samples has been measured using the impedance spectroscopy method in a BN–graphite–CaF 2 pressure cell with concentric cylindrical electrodes made from Mo- or Re-foil (the estimated oxygen fugacity was close to the IW-buffer). The results indicate that up to 15 vol.% of Fe 70S 30 the melt phase does not built a stable interconnected network in a peridotite matrix, as was recently indicated by Walte et al. (2007). The percolation threshold for a stable FeS network in olivine matrix lies at 17.5 vol.%, much higher the 6 vol.% found by Yoshino et al. (2003). Our result is in line with the high dihedral angles of typically 70–100° for Fe–S melts in mantle materials. The higher interconnectivity threshold of this study, as compared to previous studies (Yoshino et al., 2003, 2004; Roberts et al., 2007) is a result of our smaller starting grain sizes (for olivine) in combination with much longer run durations. Both these experimental conditions result in enhanced grain growth and thus to a higher degree of textural equilibration, leading to the occurrence of the time depending pinging off of Fe–S melt films in our texturally more mature experiments.

임펄스전압에 의한 동심원통형 전극계에서 토양 이온화특성 분석

본 논문은 뇌임펄스전압에 의한 토양의 이온화 현상과 모델접지시스템의 과도적 특성에 관련된 파라미터에 관한것으로 건조 모래와 습한 모래에 대한 이온화 특성을 치수가 다른 동심원통형 전극계의 실험 용기를 이용하여 연구하였다. 결과로써, 높은 임펄스전압이 인가된 모래의 비선형 전기적 특성은 이온화 과정에 의해 발생하였다. 모래의 과도임피던스는 수분의 함유량과 인가임펄스전압의 크기에 의존하며, 수분의 함유량과 인가전압의 크기의 증가에 따라 접지임피던스는 감소하였다. 본 연구결과는 뇌서지에 대하여 우수한 성능을 가지는 접지시스템의 설계에 유용한 정보가 될 것이다.

Fast slit-beam extraction and chopping for neutron generator

High-intensity fast white neutron pulses are needed for pulsed fast neutron transmission spectroscopy (PFNTS). A compact tritium–tritium fusion reaction neutron generator with an integrated ion beam chopping system has been designed, simulated, and tested for PFNTS. The design consists of a toroidal plasma chamber with 20 extraction slits, concentric cylindrical electrodes, chopper plates, and a central titanium-coated beam target. The total ion beam current is 1A. The beam chopping is done at 30keV energy with a parallel-plate deflector integrated with an Einzel lens. Beam pulses with 5ns width can be achieved with a 15ns rise/fall time ±1500V sweep on the chopper plates. The neutrons are produced at 120keV energy. A three-dimensional simulation code based on Vlasov iteration was developed for simulating the ion optics of this system. The results with this code were found to be consistent with other simulation codes. So far we have measured 50ns ion beam pulses from the system.

Surface modification of polymer fibre by the new atmospheric pressure cold plasma jet

A new cold plasma jet has been developed for surface modification of materials at atmospheric pressure. This new cold plasma jet generator is composed of two concentric cylindrical all-metal tube electrodes. The argon is fed into the inner-grounded electrode, the outer electrode is connected to the high-voltage power supply and covered with a layer of dielectric, and then a stable cold plasma jet is formed and blown out into air. The plasma gas temperature is only 25–30 °C. Preliminary results are presented on the modification of polypropylene (PP) and polyethylene terephthalate (PET) fibres by this cold plasma jet. The water contact angle of these materials is found to decrease after plasma treatment and it will recover a little in two months. The chemical changes on the surface of polymers are studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) is used to study the changes in surface feature of polymers due to plasma treatment. The hydrophilicity and surface structure of these materials after plasma treatment are discussed. The results show that such a plasma jet is effective.

High-gradient electric field system for the dielectrophoretic separation of cells

A high-gradient electric field strength system, consisting of a chamber created from two concentric cylindrical electrodes and filled with glass beads, was constructed for the study of the dielectrophoretic separation of cells. The glass beads distort the electric field patterns and generate sites of high electric field gradients, which can capture cells by dielectrophoresis. In order to experimentally determine the efficacy of the system, yeast cells were injected into a constant flow through the system, and the number of cells trapped measured. The effects of changes in voltage, bead size and the size of the inner and outer electrodes on the trapping efficiency of the dielectrophoretic separation system were investigated. In addition, simulation and electric field analysis were carried out using FEMLAB. Results indicate that the trapping of cells occurs by a combination of mechanical trapping and dielectrophoresis. Analysis of the results allow predictions to be made for the optimum values of the voltage, bead size and size of inner and outer electrode for any high-gradient system, in order to generate sufficient electric field gradient for dielectrophoretic cell collection whilst reducing non-specific mechanical trapping.

Comparison of experimental and calculated peak shapes for three cylindrical geometry FAIMS prototypes of differing electrode diameters

High-field asymmetric waveform ion mobility spectrometry (FAIMS) separates ions at atmospheric pressure and room temperature based on the difference of the mobility of ions in strong electric fields and weak electric fields. This field-dependent mobility of an ion is reflected in the compensation voltage (CV) at which the ion is transmitted through FAIMS, at a given asymmetric waveform dispersion voltage (DV). Experimental CV, relative peak ion intensity, and peak width data were compared for three FAIMS prototypes with concentric cylindrical electrodes having inner/outer electrode radii of: (1) 0.4/0.6 cm, (2) 0.8/1.0 cm, and (3) 1.2/1.4 cm. The annular analyzer space was 0.2 cm wide in each case. A finite-difference numerical computation method is described for evaluation of peak shapes and widths in a CV spectrum collected using cylindrical geometry FAIMS devices. Simulation of the radial distribution of the ion density in the FAIMS analyzer is based upon calculation of diffusion, electric fields, and the electric fields introduced by coulombic ion-ion repulsion. Excellent agreement between experimental and calculated peak shapes were obtained for electrodes of wide diameter and for ions transmitted at low CV.

Polarization between concentric cylindrical electrodes

We consider an asymmetric electrolyte between two cylindrical concentric electrodes that are uncharged in the absence of an applied voltage difference. We calculate the dielectric response of this capacitor to an alternating voltage difference. The problem is solved using both classical boundary conditions and the new boundary conditions using excess densities to describe the charge build-up near the condensator plates as given in a previous article (C. Chassagne, D. Bedeaux and G.J.M. Koper, Colloid Surf. A 210 (2002) 137.). We verify that both boundary conditions give the same results. The advantage of the new boundary conditions lies in the possibility to extend in the future the analysis to real electrodes including reactions and specific ion adsorption. A comparison of the model predictions, involving no adjustable parameters with experimental dielectric spectroscopy data, is performed and excellent agreement is found.

Transient approach to steady state of discharge phenomena in corona device

The discharge phenomena in corona device was simulated with a transient approach up to the dynamic steady state. The proposed transient approach requires neither Kaptsov's assumption nor roughness factor. As a simple numerical example, the corona discharge between two concentric cylindrical electrodes was analyzed for two different applied voltages in the one-dimensional model. The results were presented and compared with those of the conventional method. To our knowledge, this is the first work that attempts to simulate the corona discharge up to the steady state with a complete transient approach.