Types Of Electrode Systems Research Articles

Hybrid of sub-1 nm single-dispersed polyoxometalate and reduced graphene oxide as advanced anodes for durable sodium-ion batteries

Polyoxometalates (POMs) are widely thought as promising choices for sodium-ion batteries (SIBs) because of their refined molecular structures and excellent reversible multielectron charge-discharge behaviors. Nevertheless, the POMs anion clusters could dissolve in the electrolyte when attacked by solvent molecules, thus reducing active sites and affecting the actual performance of these POMs-based electrodes. Herein, we report the development of a new type of electrode system that produces single-dispersed POMs molecular cluster/polydopamine/reduced graphene oxide composites ({PMo12}/PDA@rGO) through a self-assembly method. PDA acts as the role of “killing two birds with one stone”. It not only works as the linker to promote the formation of stable and uniform monodisperse {PMo12} clusters on the rGO surface, but also prevents the POMs from desorbing and dissolving upon deep cycling test. As a consequence, when used as the anode material for SIBs, the obtained {PMo12}/PDA@rGO exhibits an admirable long-term cycling performance, for instance, it holds a high Na-storage capacity of 277.5 mAh g−1 with an average Coulomb efficiency up to 99.89 % over 2000 cycles at 1 A g−1. This work offers versatile possibilities for designing POMs-based composites and provides new insight into developing single dispersed POMs for advanced SIBs.

Experimental study of the effect of the simultaneous treatment of the melt with different currents on the quality indicators of castings

The purpose of the work is to obtain results that would confirm the effectiveness and perspective of using the method of simultaneous treatment of a liquid alloy based on Al with different types of currents in foundry technologies. As it is known the different types of current passing through the melt (alternating, constant, pulsed) are differ from each other by their different functional capabilities. The each types of currents generate electromagnetic fields with different amplitude-frequency characteristics and distribution, which determine the sphere of influence. The work proposed to use an innovative principle of simultaneous passing of at least two currents with different electrical characteristics through the melt and with different variants of electrode systems. This method made it possible to affect more effectively on the structure and properties of the melt and, in turn, improve the service characteristics of the casting. In the work, two series of experiments were performed with the application of melt treatment with three types of currents and three types of electrode systems in different combinations. Ingot alloys of the Al-Si system was treated: AK7 (GOST 1583-93), chemical composition: Si (7.3 %); Fe (0.5 %); Cu (0.5 %); Mn (0.07 %); Mg (0.07 %); Zn (0.2 %); Pb (0.01 %), Al base; and non-standard pre-eutectic silumin additionally doped with certain components (Si (8 %); Fe (0.79 %); Cu (1.98 %); Mn (0.1 %); Mg (0.27 %); Zn (0.44 %), Al base). In contrast to the treatment of one type of current, an increase the mechanical properties of castings and an effective modification of the elements of the solid state structure were achieved. Thus, for the first grade of alloy, σВ was increased by 13 %, and δ — by 1.5 times. Also after simultaneous treatment with different types of currents with defined modes, the value of Ψ was recorded at the level of 4.4 %. For the AK7 alloy, this indicator is not even specified by the standard. For the second grade of alloy, after simultaneous treatment with different types of currents, significant grinding of intermetallics to sizes from 8 μm to 11 μm was observed, while compared to the original sample, there is practically no segregation of the intermetallic component by size. The structure of the treated samples is distinguished by the grinding of silicon particles in the eutectic. The total energy consumption, under certain conditions, for both brands of alloys was reduced by 3 times. The main mechanism of a positive change in the crystallization ability of the melt is formation of electromagnetic fields superposition with more powerful thermoforce effect in the treatment object by passing different types of currents simultaneously than when using one type of current.

МОДЕЛЮВАННЯ РОЗПОДІЛУ ЕЛЕКТРИЧНОГО ПОЛЯ В МЕТАЛЕВОМУ РОЗПЛАВІ МЕТОДОМ РОЗБИТТЯ ПРОВІДНИКА НА ЕЛЕМЕНТАРНІ КОМІРКИ

Purpose. To show the functional possibilities of the method of dividing massive conductors into elementary cells and matrix 2D, 3D formalization of electric field characteristics in a metal melt during its electric current treatment. For foundry production technologies, the processes generated in the metal melt during its conductive electric current treatment (CECT) are studied. Methodology. Along with the material science aspects of the problem with the help of numerical simulation is the search for optimal parameters of the melt load. The finite element method (FEM) is used for this purpose. Originality. The tasks to be solved are not classic. This imposes problems on the choice of problem statement and methodological principles of calculations. Therefore, it is important to find another productive flexible numerical modeling method. This is especially important in the development of systems for the implementation of controlled conductive electric current treatment of liquid metals. The paper proposes to apply the known method of dividing massive conductors into elementary cells (M-C), which must be adapted to the CECT conditions in foundry production. At the same time, using this method in combination with FEM, it is possible to deepen the scientific achievements of CEСЕ and obtain validation and verification of the results of solutions. Results. A number of problems have been solved that show different possibilities of modeling with using of the M-C method. The results of using M-K method allows to relatively accurately reproduce the distribution of the base electric field in the metal melt during its treatment with electric current. The ensuring the validation and verification of obtained results, in combination with, for example, M-C and FEM methods can significantly influence the expansion of scientific work on the thermoforce influence of the melt. The obtained results, which be compatible with FEM data, describe the characteristics of basic electric field in the melt in 2D and 3D formats. It is shown that the 2D format enables to determine possible trends in the distribution of field characteristics for different types of currents and types of electrode systems. 3D format has greater functionality, but its productive application requires the improvement of computational algorithms in the matrix formalization of field characteristics in metal melts weighting several hundred kilograms. Figures 7, references 11.

Phase-resolved partial discharge analysis of different types of electrode systems using machine learning classification

Partial discharge (PD) measurement is a diagnostic technique used for electrical insulating systems. The establishment of a highly accurate PD diagnostic technique has become necessary in recent years. Therefore, in this study, we analyzed a phase-resolved PD signal using machine learning classification for different types of experimental electrode systems. A polyethylene sheet was used as the sample, and PD was generated by applying a high AC voltage to four different types of electrodes. The number of PD pulses was counted from the raw data as preprocessing to calculate the feature value for the machine learning. The PD generation rate was defined for each phase angle section. Four types of machine learning algorithms were adopted for the classification of the electrode system: k-NN (k-nearest neighbor algorithm), logistic regression, decision tree, and random forest. The best accuracy was obtained by using the random forest algorithm (0.97), and it was found that k-NN also demonstrated good performance. The parameter dependencies were also evaluated for each algorithm. Based on the results generated by the random forest, it became clear that there were phase angle sections that were of high importance. The reason for the result was discussed from the perspective of (i) the difference due to the electrical circuit parameters (modified abc-model) and (ii) the stochastic fluctuation of PD signal.

Radiation in the Optical and UHF Range Emitted by Partial Discharges

This paper presents the results of analysis of a solid dielectric’s influence on the phenomena associated with the signals emitted by surface partial discharges. Three types of electrode systems were tested, in which solid dielectrics made of pressboard, Teflon, and glass were used. The emission of such signals as radio waves in the Ultra high frequency (UHF) range and optical radiation was analyzed. The measurements were carried out in the insulation systems most commonly used in electrical power equipment, i.e., mineral oil and air. UHF and optical spectrophotometry methods were used to register the emitted signals. The obtained results indicate that the type of material from which the dielectric solid is made may have a potential impact on some ranges of emitted electromagnetic waves during the surface electrical discharges. The research topic undertaken is important in issues associated with high-voltage insulation systems and in particular with surface discharges, which are often the cause of their damage.

Measurement and analysis of partial discharges in SF6 gas under HVDC

With the rapid development of high voltage direct current (HVDC) technology and the requirements of smart grids, there is a new challenge of monitoring and diagnosing the insulation performance of related power facilities. This paper dealt with the measurements and analysis of partial discharges in SF6 gas under HVDC in terms of discharge inception voltage (DIV), discharge magnitude and pulse count, as well as the statistical characteristics extracted from discharge distribution and density functions. Five types of electrode systems were fabricated to simulate typical insulation defects in gas-insulated switchgear. All these systems were filled with SF6 gas in ranges from 0.1 to 0.5MPa. The measurement system was developed based on the real time operating system by LabVIEW. The results revealed that identification of the defects in gas-insulated equipment operated under HVDC can be realized by analyzing the statistical characteristics extracted from the discharge distribution and density functions.

Flowable Electrodes: A Review of the Material Aspects of Capacitive Suspension Electrodes for Grid Energy Storage and Desalination Applications

In the past couple of years flowable electrodes have emerged as a possible avenue for achieving high charge capacity in large scale infrastructure applications across the globe (grid energy storage [1-4] and water desalination[5-6]). Flowable electrodes or suspension electrodes are a new type of electrode system where the active materials is directly combined with an electrolytic medium. The electrolyte is gravimetrically the majority component and aids in the physical transport of the active material for charge storage (ion adsorption). The ability to continuously flow (replenish) active (solid) material through a polarization cell allows for continuous charge storage. At Drexel, our focus has been on the development of capacitive suspension electrode (CSE) systems that utilize electrostatic charge storage mechanisms as means for charge storage. A key difference between suspension (flowing) electrodes and film electrodes is the thickness of the electrodes. Suspension electrodes, targeted for large scale applications, are at least an order magnitude thicker than film electrodes. Thus, as the capacitance decreases with electrode thickness the energy density (E=1/2CV2) also suffers [7]. To address this challenge, we have examined an array of active materials (metal oxides/highly porous carbon spheres) and electrolytes (redox-active, aqueous, organic) in order to understand the key aspects that govern efficient charge and ion transport in suspension electrodes. This poster will review the fundamental physical and kinetic considerations that must be examined in order to achieve high performing flowable electrodes. Furthermore, we will highlight the key material differences when developing active materials for flowable electrodes for grid energy storage applications and desalination applications.

Metal plating removal from insulator substrate using pulsed arc discharge

Removal technique of metal materials from a metal plating insulator substrate using a pulsed arc discharge was proposed and its fundamental characteristics were investigated. The metal plating substrate with three metal-layers structure (cupper, nickel and gold layers) is used as the sample substrate. Repetitive pulsed arc discharge plasma is generated using three types of electrode systems. Effects of the electrode systems on the metal plating removal from the insulator substrate were investigated. The metal plating was removed by the pulsed arc discharge between the electrode and substrate surface. A part of the gold layer, which is the topmost metal layer on the insulator substrate is vaporized and removed by the repetitive pulsed arc discharges.

Frequency Spectrum Analysis of Electromagnetic Waves Radiated by Electric Discharges

In this paper, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic study to develop an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series arc discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and an arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetic anechoic chamber, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 kHz-30 MHz, an ultra log periodic antenna with a frequency bandwidth of 30 MHz-2 GHz, and an EMI test receiver with a frequency bandwidth of 3 Hz-3 GHz. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 kHz-400 MHz, depending on the defects, while commonly found between 150 kHz and 10 MHz. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closedswitchboards is 150 kHz-10 MHz.

Measurements and analysis of the acoustic signals produced by partial discharges in insulation oil

Abstract This paper focuses on the frequency analysis of acoustic signals produced by partial discharges (PDs) in insulation oil and the positioning of the PD occurrence for application in the diagnosis of oil-insulated transformers. Three types of electrode systems; the needle–plane, the plane–plane, and the wire–wire structures were assembled to simulate the partial discharge in insulation oil. A low-noise amplifier and a de-coupler were designed to detect the acoustic signal with high-sensitivity. The frequency ranges of the acoustic signal were 60–270 kHz in the needle–plane electrode system, 45–250 kHz in the plane–plane electrode system, and 50–180 kHz in the wire–wire electrode system. Their peak frequencies were 145 kHz, 118 kHz and 121 kHz, respectively. The position of the PD occurrence was calculated from the time difference of arrival (TOA) using three acoustic emission (AE) sensors. The position was found within a 1% error in the experimental set-up.

Internal defibrillation with minimal skeletal muscle activation: A new paradigm toward painless defibrillation

Shock-induced pain produces substantial morbidity in recipients of implantable cardioverter-defibrillators (ICDs). This pain likely derives from activation of skeletal muscle and associated nerves in the chest and abdomen. In an effort to develop a painless defibrillation system, we designed an electrode arrangement that incorporates a conductive sock placed around the heart to confine the electric shock field to cardiac tissue. The purpose of this study was to test whether cardiac defibrillation could be achieved without skeletal muscle activation using a novel electrode system. Eight adult mongrel dogs were studied. Force of skeletal muscle contraction was measured by strain gauges attached to the forelimbs during delivery of internal shocks ranging in energy from 0.1 to 31 J. Biphasic shocks were delivered (1) between a right ventricular coil and a subcutaneous dummy can (standard configuration), and (2) between a left ventricular coil and an epicardial electrode sock. Internal and external defibrillation thresholds (DFTs) were determined for each electrode configuration. Shock-induced muscle contraction force was significantly lower using the sock electrode than with standard ICD electrodes at every shock energy level tested (P < .0001). Internal DFT was similar between electrode configurations (sock electrode: 8.6 +/- 4.2 J; standard: 11.0 +/- 6.3 J, P = .4), but muscle contraction force at DFT was greatly reduced with the new electrode system (1.8 +/- 2.0 kg vs 10.6 +/- 2.1 kg, P < .0001). The sock electrode rendered external defibrillation impossible, however, even at 360 J. Skeletal muscle activation induced by ICD shocks can be greatly reduced using an electrode system that confines the electric shock field to the heart. Refinement of this strategy may allow for delivery of painless shocks by ICDs. Further development is needed to overcome implant complexity and the higher external DFT with this type of electrode system.

A Compact Source of Subgigawatt Subnanosecond Pulses

The system comprises a nanosecond solid-state opening switch (SOS) generator that charges resonantly a short pulse-forming line (PFL) through a decoupling inductor, one or two pulse-compression stages based on high-pressure gas spark gaps (SGs), a matched load and several built-in voltage and current probes. Weighing less than 50 kg, the pulser provides up to 160-kV subnanosecond pulses at a 37.5-/spl Omega/ load at a repetition rate of up to 300 Hz. The pulsewidth can be regulated from 2 ns down to 300 ps without SG depressurization. The rise- and fall times are 180 and 100 ps, respectively. Alternatively, unipolar or bipolar output can be provided. The latter was formed by a synchronous operation of SGs located at the beginning and at the end of a PFL; thus, an active conversion of unipolar to bipolar output was realized. The load peak-to-peak voltage was almost two times as high as the amplitude of the unipolar pulse. In the active converter, a virtually identical electrical field stress across the switching SGs was achieved, which alone provided its stable operation. Circuit analysis accounting for distributed character of the components and numerous parasitic parameters is presented. Voltage and current measurement means were developed and time-domain calibrated. Waveforms probed at different locations of the pulser system, from the SOS generator to the load, are presented. The experimental results are in fair agreement with PSpice simulations used for the hardware design. Life test of a one-stage compressor with two types of electrode systems was performed, and the results are reported. The pulser was tested with a TEM horn antenna. The effective potential (field multiplied by distance) of this radiation source is 640 kV in far field.

TiO 2 phytate films as hosts and conduits for cytochrome c electrochemistry

Cytochrome c is accumulated into a film of TiO 2 nanoparticles and phytate by adsorption from an aqueous solution into the mesoporous structure. Stable voltammetric responses and high concentrations of redox protein within the TiO 2 phytate layer can be achieved. Two types of electrode systems are reported with (i) the modified TiO 2 phytate film between electrode and aqueous solution phase and (ii) the modified TiO 2 phytate film buried under a porous gold electrode (‘porotrode’). The electrical conductivity of TiO 2 phytate films is measured and compared in the dry and in the wet state. Although in the dry state essentially insulating, the TiO 2 phytate film turns into an electrical conductor (with approximately 4 Ω cm specific resistivity assuming ohmic behaviour) when immersed in aqueous 0.1 M phosphate buffer solution at pH 7. The redox protein cytochrome c is therefore directly connected to the electrode via diffusion and migration of electrons in the three dimensional mesoporous TiO 2 phytate host structure. Electron transfer from cytochrome c to TiO 2 is proposed to be the rate-determining step for this conduction mechanism.

Electrochemical Reaction in a High Gravity Field Vertical to an Electrode Surface-Analysis of Diffusion Process with a Gravity Electrode

With a new type of electrode system that utilizes the radial component of the centrifugal force instead of the real gravity force, the effect of the promoted gravity field on the diffusion process of ions was examined. First, the diffusion equation was derived in the case when the gravity field is imposed vertically onto an electrode surface. Then, it was theoretically clarified that numerous minute convection cells with sizes of the order of the diffusion layer thickness appear through a self-organization process from a top-heavy distribution of fluid density arising from the electrode reactions. The equation predicted that the diffusion current density is proportional to the 1/3rd order of the gravity acceleration and the 1st order of the difference between the bulk and surface concentrations. Then, we attempted to confirm this prediction by using the redox reaction of a ferricyanide–ferrocyanide system, and found that all of the experimental results exhibits good agreement with the predictions. Finally, the dependences of the diffusion coefficients of ferrocyanide and ferricyanide ions on the enhanced gravity fields were measured. However, for the gravity fields up to 650g, it was concluded that no remarkable dependence of the diffusion coefficient on the gravity is observed.

Physical and chemical modifications of high-voltage pulse sterilization

Pulse sterilization, which is a method of inactivation of cells by high-voltage pulsed electric field, can cause the destruction of cell membrane and cell death. Because the generated heat is relatively low, this method has the advantage of sterilizing contaminants in liquid foods without denaturation of some physiological compounds such as proteins, vitamins, etc. In this research, the effects of the shape of treatment chamber and the addition of bactericides on pulse sterilization were studied. Three types of electrode systems (a needle-plate electrode system, and a plate-plate electrode with and without edge systems) were used in this research. At an applied voltage of 12 kV, the most efficient sterilization was achieved when the needle-plate system was used. Pulse sterilization of Saccharomyces cerevisiae was carried out in treatment chambers with and without insulating plates between the electrodes. These insulating plates were Plexiglas plates with some holes. When an applied voltage was 10 kV, an insulating plate with nine holes which is 1.5 mm in diameter (the minimum size in our experiments) had better sterilization efficiency because the holes between the electrodes concentrated the electric field. Sterilization of Salmonella typhimurium was carried out under controlled temperature with and without pulsed electric field. The survival ratios at 50 °C with and without pulsed electric field were 10 −4 and 10 −1, respectively. Temperature dependence of pulse sterilization was also observed when S. cerevisiae and Escherichia coli were used as the subjects. Pulse sterilization of E. coli was carried out with and without ozone and H2O2 as bactericides. Although a lower concentration of these bactericides could not cause cell death, pulse sterilization with bactericides was more effective than pulse sterilization alone. The bactericides caused cell membrane wounding that resulted in easier pulse sterilization. Because no residual bactericides were detected in the sample liquid after treatment, pulse sterilization with bactericides appears to be possible in the food industry.

Improvement of the Corona Discharge in Dry Air in Order to Obtain Ozone With Maximum Efficiency

An ozone production system based on a corona discharge in dry air is described. The ozone generator has a novel type of electrode system, theoretically optimized, and with double discharge surfaces. A specially designed high voltage supply was used, which generates the required pulses according to a time program calculated to increase energy efficiency. The described experimental system was found to have a reduced power consumption per gram of ozone produced and also greater ozone production per electrode area than other systems that use a classical arrangement of electrodes.

Solid Sampling Approach in Inductively Coupled Plasma Atomic Emission Spectrometry for the Determination of Four Lanthanides With High Sensitivity

A solid sampling technique was developed for the ICP-AES determination of ultra-trace amounts of lanthanides chemically separated from U/Pu fuel materials. An essentially dc arc approach of using a buffer–carrier mixture of graphite–AgCl (4+1) was adopted to facilitate volatilization of the lanthanides. A 20 µl volume of lanthanide solution is loaded on 20 mg of carrier–buffer mixture placed in the crater of a Scribner–Mullin type of electrode system, evaporated under an IR lamp and introduced into the running argon plasma using a modified plasma torch assembly. The near total introduction of sample vapour into the plasma allows the determination of Dy and Eu at the 0.4 ng level and Gd and Sm can be determined at the 1 and 2 ng levels, respectively, with a precision of 10% RSD. The method is free from interferences due to the presence of concomitant lanthanides and common metals and has a significantly high tolerance to the presence of refractory U–Pu matrices.

Effects of sheath potential of source plasma on characteristics of low energy beam extraction

In order to obtain a high brightness ion beam from a plasma ion source in the low energy region (150 eV), the effects of sheath potential on the ion beam characteristics such as beam divergence and brightness have been studied experimentally. A bucket-type ion source (magnetic multicusp ion source) with an accel–decel triode extraction system is used for the experiment. Bias voltage between a discharge chamber and a positive (plasma) electrode is applied for sheath potential control. Two types of electrode systems have been examined, such as straight hole aperture (S type) and recessed hole aperture (R type), and have found that the effects of the bias voltage on the beam characteristics depend on the type of aperture and the deceleration voltage. For an S-type system, the application of bias voltage improves the beam performance in a low deceleration voltage (−600 V), but not in a high deceleration voltage (−1600 V). For an R-type system, almost no improvement is observed in all deceleration voltages. Although the highest brightness is obtained in a deceleration voltage of −1600 V without the application of bias voltage in the S-type system, the significant fraction of the intersecting beam to the electrodes is present in this case.

Analysis of Space Charge in Insulating Materials under Non-Uniform Electric Fields

A simple technique to calculate the charges induced on electrodes by space charges distributed in a dielectric is presented. The technique is based on Green's theorem and does not depend on the type of electrode system. A needle-plane electrode system is analyzed and the charges induced on each electrode are calculated. Experimental results of thermally stimulated current measurements usinig a needle-plane electrode system have been analyzed and the mean location of trapped charge has been determined.

Calculation of the performance chart for Roots-type pumps: H Hamacher, Rep DLR-FB-69-88, Dec 1969, 118 pages ( in German) ( Sci Tech Aerospace Reps, 8 (12), 2216, N70-26326)

One of the important requirements when optimizing ionization gauge sensitivity is that the most efficient use be made of the ionizing electrons. Recent designs of extractor gauge retain the cylindrical grid structure, external electron emitting filament and coaxial screen cylinder currently used in the Bayard-Alpert gauge. The motion of electrons in this type of electrode system is described and the dependence of gauge sensitivity on the resulting trajectories is analyzed.The relationship is illustrated between the average number of electron passes through the grid region and the electron capture probability of the grid, showing the advantage of a high grid transparency. Computer aided design techniques have been employed to study the influence of electrode spacing and potentials on the path lengths of electrons. The results of this study are presented and show that a considerable variation in gauge sensitivity can occur, depending on the extent to which the electrons are focused into diametric paths across the grid region. Experimental results are given which illustrate this effect and show how the grid to screen potentials required for optimum sensitivity depend on both filament to grid potential and spacing.