Charge Accumulation Process Research Articles

Bio/inorganic nanohybrids L- aspartic acid: obtained, properties, applications

Using the developed technology, double-matrix structures of the hierarchical architecture GaSe <LAK> InSe <LAK> and C <LAK> were obtained. In the first two systems, significant increase in photosensitivity and visualization of the effect of photo-inductive response was recorded. New effect was revealed - oscillation of imaginary component of complex impedance of nanostructure GaSe<LAK> under lightning, which is most likely caused by the phenomenon of quantum-mechanical resonant tunneling. Also, this nanostructure is characterized by a high quality factor that is promising for its use in the manufacture of super-high capacity radio-frequency capacitors. Frequency dependence of dielectric permittivity of InSe <LAK> nanostructure is very interesting, namely its low-frequency oscillations, which may be caused by the processes of charge accumulation on the inter-phase limits and resonant tunneling in the N- barrier structure, formed as a result of nano-hybridization. The use of the synthesized structure C <LAK> as cathode material for Li+- intercalation current formation provided the value of specific capacity of 350 mAh/g, which is twice higher than the specific capacity of the known market cathode materials.

Time-dependent process of electric charge accumulation on a sphere in a viscous stream with the ion component

The problem of time-dependent charging of electrically insulated ideally-conducting bodies in a stream of an incompressible viscous medium with the ion component is considered. The following effects are included in the expression for the ion current: convective ion transfer with the velocity of the medium and the ion drift and diffusion in the electric field. In this formulation the problem of time-dependent charging of a sphere is formulated and solved. The role of the diffusion effects is clarified. The fields of hydrodynamic and electric parameters are found. The time dependences of the sphere charge and potential are obtained.

Research on the Charged Omni-Directional Spatial Electric Field Tester

The spatial electric field tester is mainly used for the measurement of high-altitude electrostatic field. The spatial electric field tester will be electrostatically charged during the period it is sent to a certain height by a micro-rocket. In order to study the charge characteristics, the paper analyzes the charging mechanism of the omni-directional spatial electric field tester and builds mathematics model for the friction charging, which is a main factor of the charging process. The numerical calculation and experimental research demonstrate that the friction introduces a slow charge accumulation process for the electric field instrument in the course of its campaign. Under the testing conditions in this paper, the charge amount is 10-11 C within the 6s duration. In order to improve the accuracy of the electric field measurement, a time-frequency analysis method can be adopted to remove the slow-varying electric field signal.

Resolving the subnanometric structure of ultrathin films of poly(3,4-ethylenedioxythiophene) on steel surfaces: a molecular modeling approach

Poly(3,4-ethylenedioxythiophene), abbreviated PEDOT, is one of the most outstanding electroactive polymers, whose applications cover a wide range of fields from biomedicine to electronic components. In this work the physicochemical properties of nanoconstructs obtained by growing PEDOT chains over steel surfaces are investigated. The structural features of such nanostructures, which had successfully been used to build supercapacitors, are investigated, revealing that the polymeric phase plays a key role in the charge accumulation process. The ultra-structure organization and dynamics of these constructs are explored by molecular simulations and the results are compared with the available experimental data. The outcome of this investigation has offered a detailed vision of the structural features that lead to an extraordinarily efficient charge accumulation. Atomistic models generated using stochastic methods had provided different distributions of polymer chains over a metallic surface. Molecular dynamics simulations performed on such models have demonstrated that the extraordinary capacity for charge accumulation stems from a thin balance between the electrostatic repulsion that polymer chains exercise to each other and the attraction that the counterions present in the electropolymerization exert on those oxidized PEDOT chains. This situation favors the aggregation of the PEDOT chains mediated by the perchlorate ions, which act over them as inter-chain cement and which leads to regular three dimensional organization of chains, regardless of their initial distribution over the metallic surface. At the same time, such inner proximity of the polymer chains when growing upwards forces the capture of perchlorate ions, acting as accumulated charges that could be further released if the PEDOT oxidation state is externally reversed.

Accumulation of spatial charge in the time projection chamber of a multipurpose detector

This article presents the results of a numerical simulation of the process of spatial positive charge accumulation in the Time Projection Chamber (TPC) of the multipurpose detector (MPD) at Nuclotron-based Ion Collider fAcility (NICA) at the Joint Institute for Nuclear Research (JINR). Based on the spatial distribution of the charges, the problem of calculating the potential of the electrostatic field created by these charges has been solved. The radial, angular, and axial distortions in the electron motions from the point of ionization to the readout planes are calculated.

Ion motion in salt water flowing under a transverse magnetic field

The problem of ion motion in an electrolyte solution flowing in a thin rectangular duct with velocity VE in the presence of a transverse magnetic field B0 is studied by means of classical mechanics and electrodynamics. Because of Lorentz force on the ions in the electrolyte solution, a so called Faraday voltage appears at the electrodes orthogonal to both the field B0 and the velocity VE. The dynamics of positive and negative ions (cations and anions, respectively) in this classical system is studied by taking into account the viscosity of the fluid and the process of charge accumulation on the opposite walls of the duct. Hydrogen production is seen to take place at one of the electrodes when salt water is taken as the flowing electrolyte.

Surface charge accumulation on cylindrical polymeric model insulators in air: simulation and measurement

The time characteristics of the surface charge accumulation process on cylindrical polymeric model insulators under dc stress were investigated in a partial discharge free, dry air environment. In order to simulate the influence of different dielectric and electric material properties on surface charge accumulation, a tool was developed which considers also the nonlinear behavior of the electric conduction mechanism within the gas volume. The results of simulation have been verified by measurements of the surface potential distribution along the samples at different ambient temperatures.

Analyzing photovoltaic effect of double-layer organic solar cells as a Maxwell-Wagner effect system by optical electric-field-induced second-harmonic generation measurement

By using time-resolved optical electric-field-induced second-harmonic generation measurement, we directly probed photo-voltage generation process in organic double-layer (pentacene/C60) solar cells. Results showed that photoillumination induced negative excess charge Qs = −3.6 × 10−9 C/cm2 at the pentacene/C60 interface, and the induced charge caused generation of the open-circuit voltage 0.26 V. Using an equivalent circuit based on a Maxwell-Wagner (MW) effect model well accounted for the excess charge accumulation process. The MW model analysis also well accounted for the open-circuit voltage, the short-circuit current, and the fill-factor of organic solar cells (OSCs). We concluded that the excess charges due to the MW effect give a significant effect on the photovoltaic effect of OSCs.

Analyzing carrier lifetime of double-layer organic solar cells by using optical electric-field-induced second-harmonic generation measurement

By using optical electric-field-induced second-harmonic generation (SHG) measurement, we directly probed charge accumulation and decay processes in double-layer [copper-phthalocyanine (CuPc)/C60] organic solar cells (OSCs). Results showed that negative excess charges accumulated at the CuPc/C60 interface under photoillumination and the charges decayed in a two-step process in dark. Analysis using the filtering method showed that 24% of the accumulated negative excess charges decayed with a lifetime τL1=5.3×10−5 s and the other 76% of charges decayed with a lifetime τL2=6.2×10−2 s. We conclude that analyzing SHG signal response provides a direct way to investigate carrier lifetime in multilayer OSCs.

Charge accumulation dynamics in organic thin film transistors

We have developed a transient current model to quantitatively describe the charge accumulation dynamics in organic thin film transistors. This model indicates that the charge accumulation process is faster at higher gate bias and/or higher field-effect mobility, and the experimental results are consistent with the theoretical expectations. A strong gate bias dependence of the field-effect mobility is observed, which suggests that the charge traps in the charge accumulation layer may limit the device performance not only at steady state but also at transient state.

Global lightning formation at a minimum and maximum of solar activity according to the observations of the Schumann resonance on the Kola Peninsula

On the basis of the two-component measurements of the atmospheric noise electromagnetic field on the Kola Peninsula, a change in the first Schumann resonance (SR-1) as an indicator of global lightning formation is studied depending on the level of galactic cosmic rays (GCRs). It is found that the effect of GCRs is most evident during five months: in January and from September to December; in this case the SR-1 intensity in 2001 was higher than the level of 2007 by a factor of 1.5 and more. This effect almost disappears when the regime of the Northern Hemisphere changes into the summer regime. It is assumed that an increase in the GCR intensity results in an increase in the lightning occurrence frequency; however, the probability that the power of each lightning stroke decreases owing to an early disruption of the charge separation and accumulation processes in a thundercloud increases; on the contrary, a decrease in the GCR intensity decreases lightning stroke occurrence frequency and simultaneously increases the probability of accumulating a higher energy by a thundercloud and increasing the lightning power to the maximum possible values.

Relaxation phenomena in (As2Se3)100 − x Bi x layers

The physical parameters, which describe the relaxation phenomena occurring in both the bulk and contact regions of the systems under investigation, have been calculated using experimental curves of isothermal relaxation of polarization current in thin films of modified (As2Se3)100 − xBix. The relation between the change in the internal structure of the studied materials and the processes of charge transfer and charge accumulation has been revealed. The results obtained have been discussed with invoking the relay-race mechanism of charge transfer.

Charge accumulation effects on time transition of partial discharge activity at GIS spacer defects

The partial discharge (PD) measurements are considered as the most important tool for condition monitoring of Gas Insulated Switchgears (GISs). However, if spacer surface is involved in PD activity, charge accumulation process greatly affects the time transition of PD characteristics. This paper investigates this effect considering the defect types of delamination at the electrode/spacer interface and metallic particles adhered to the spacer surface as the most serious defects that can lead to major failure. Two different electrode configurations were built to simulate the two defect types. The PD characteristics were measured and analyzed from immediately after voltage application up to several minutes where steady state characteristics have been obtained. As a result, it was found that the generation rate of PD pulses changed considerably with time for both defect types. This tendency of PD characteristics has been discussed considering the effect of charge accumulation. Comparing these effects for negative and positive PD enabled to clarify the similarities and differences in the charge accumulation effect for both defect types which can contribute to the defect type identification in GIS. It was found that the effects of charge accumulation on the electric field strength for the delamination defect case as well as on the ionization volume for the metallic particle case were the responsible parameters for the different PD tendencies.

Surface charge accumulation and partial discharge activity for small gaps of electrode/epoxy interface in sf6 gas

The electrical insulation reliability of solid spacers in gas insulated switchgears (GISs) is an important issue to achieve a safe operation of such equipment. Among different phenomena, charge accumulation represents the most important matter that can degrade the overall performance of these insulation systems. For this respect, this paper discusses the contribution of partial discharge (PD) activity by ac voltage application to charge accumulation in the small gap at the electrode/epoxy interface as one of the weakest points in GIS solid spacers. The partial discharge inception voltages for non-accumulated charge case (PDIV0) and after exposing to PD activity (PDIVn) are measured among different gap lengths, simulating delamination at the electrode/epoxy interface. The PD activity is generated using applied voltage with 1.2×PDIV0 for all gap lengths examined in this study (50~500 ?m). In these measurements, PDIV increased with increasing the number of PD pulses as a result of accumulated charges. The accumulated surface charge density is estimated using the boundary equations and is compared for the different gap lengths. The accumulated charge density was larger for the smaller gap lengths. Comparing PD parameters with accumulated charge density enabled us to identify that the number of negative and positive PD pulses is the main parameter that corresponds to charge accumulation process.

Investigation of the processes of charge transfer and charge accumulation in As2Se3 amorphous layers prepared by different methods

The influence of the method used for preparing As2Se3 amorphous layers on the processes of charge transfer and charge accumulation in these structures is studied. Different physical parameters, such as the contact capacitance, the width of the charge accumulation region, and the time of transit of charge carriers through the samples, which characterize the occurring electronic processes, are determined for the layers under investigation.

Charge storage characteristics of gold nanoparticles embedded in alumina matrix

The processes of charge accumulation in the nonvolatile memory metal-oxide- silicon capacitors with gold nanoparticles floating gate formed by the pulsed laser deposition method are investigated. The regularities of formation of alumina films with gold nanoparticles are the result of their deposition from the back flow of low-energy particles from the erosion torch. With removing from the torch axis, sizes of gold particles and the film thickness decreased. When recording the capacitance-voltage curves, the capture of a negative charge was observed. It was shown that the concentration of gold nanoparticles in alumina matrix and the thickness of nanocomposite films remarkably influenced on the stored charge. The observed flat band voltage shift was in the range 1 to 14 V. To explain the peculiarities of charge storage in the composite films, the electron transport through them was investigated.

On the hierarchy of the influences of porous and electronic structures of carbonaceous materials on parameters of molecular storage devices

Abstract The relation between porous structure, electronic properties of carbonaceous material and the capacitance of its interface with an electrolyte is discussed. It is shown that, in an electric double-layer, the contribution of pseudocapacitive charge accumulation is determined, mainly, by the position of Fermi level in the carbonaceous material and depends on thermodynamic parameters of ions in the electolytic solution. The sizes of the pores in which the processes of capacitive and pseudocapacitive charge accumulation dominate are determined. Theoretical analysis of the processes taking place on the nanoporous carbon|electrolyte interface has made it possible to recognize the intercalative nature of pseudocapacity and to find the criterion of its manifestation in the form of the formation of a continuous series of stable valency phases.

Simulation of microdischarges on an aircraft surface

New problems associated with charging of aircraft are considered. The first problem concerns the aircraft charging dynamics and the analysis of the steady-state and transient processes of charge accumulation on the aircraft surface. Possibilities of controlling the aircraft charge using the active charge compensation principle are demonstrated. The second problem concerns the development of microdischarges (discharges of low intensity) on a charged aircraft surface. The microdischarges develop in the presence of elements with disturbed electric contact with the remaining surface and lead (when sufficiently numerous) to interference with the operation of the aircraft’s radionavigation equipment. A method of simulating the electric charge growth on these elements under laboratory conditions by blowing over them a gasdynamic jet with a unipolar ion charge flowing out from a specially created source is proposed and justified theoretically. Microdischarge recording methods (time-base sweeps and spectra of the electric discharge current and acoustic signals), which make it possible rapidly to determine these elements (points of “ demetallization” of the aircraft structure), are developed. Data on microdischarges from both metal elements and the composite elements now widely used in aircraft structures are obtained.

Effect of morphology, proton irradiation and pre-stressing on the breakdown of LDPE

It is a well-known fact that the breakdown of low density polyethylene depends on the space charge accumulation in the polymer bulk. In turn, the process of a space charge accumulation is governed by a sub-microscopic structure of polymers, the contact conditions on the interface electrode/polymer and the charge carriers injection from electrodes. It is shown that the surface modification of the LDPE samples by proton irradiation allows the number of impulses to breakdown to be increased. One more way to increase the life time and the breakdown strength of LDPE is the so-called pre-stressing, i.e., preliminary polarization of LDPE under dc voltage. A larger increase in the number of impulses to breakdown is observed in the LDPE samples after simultaneous application of dc pre-stressing and modification of the LDPE surface layers by proton irradiation. This phenomenon is related to the homo-charge accumulation near the electrodes

Charge accumulation effects in quantum-well structures

The effect of accumulation of charges produced owing to the absorption of light in quantum-well structures under longitudinal electric fields is considered. It is shown that, in such two-dimensional structures, the charge accumulation process differs substantially from that in three-dimensional systems. The charge distributions in the structures are calculated for various electric fields and total numbers of accumulated charges. It is also shown that, at considerable amount of accumulated charges, the Fermi-type degeneracy begins to play an important part in the distributions of charges and potentials. Such accumulation of charges can result in nontrivial luminescence in which the processes of charge carrier generation and subsequent recombination can be essentially separated in time from each other. In addition, this luminescence is not masked by emission on the transitions involving the tails of the density of states in the band gap and by emission from the substrate.