External Electric Field Strength Research Articles

Effects of promoter and dedoping process on electrorheological response of polyaniline-graft-chitosan copolymer

In this study, electrorheological (ER) properties of biodegradable and conducting polyaniline-graft-chitosan (PAni-g-CS) copolymer particles were investigated. For this purpose, PAni and PAni-g-CS particles were synthesized by using in situ oxidative radicalic polymerization method. At first, PAni and PAni-g-CS/silicone oil (SO) ER suspensions (15% V/V) were subjected to external electric field and they exhibited low ER activity. When the external electric field strengths ([Formula: see text] were increased, both the suspensions showed electrical breakdown. Therefore, virgin PAni and PAni-g-CS were first subjected to dedoping process by treating with 1.0 M NaOH(aq) and non-ionic surfactant Triton X-100 (T-X) surfactant to enhance the expected ER activity and prevent the electrical breakdown. But we observed that the addition of T-X as promoter had no significant effect on the ER activity. On the other hand, electric filed-induced viscosities of both the suspensions were observed to enhance after the dedoping (DD) process and electrical breakdown prohibited. After the DD process, DD PAni-g-CS/SO ER system exhibited the highest electric field-induced viscosity by reaching 400[Formula: see text]Pa[Formula: see text]⋅[Formula: see text]s at [Formula: see text][Formula: see text]kV/mm. The highest ER efficiency was also obtained for DD PAni-g-CS/SO system at 15% (V/V) as 79. Additionally, typical shear thinning non-Newtonian viscoelastic behavior was observed under externally applied E. The conduction model of DD PAni-g-CS/SO system was determined to well fit the conduction model by showing a slope of [Formula: see text] calculated from the E vb. yield stress graph. In conclusion, conducting and biodegradable-dedoped PAni-g-CS particles would be a good candidate for potential ER applications as dry-based ER materials having high colloidal stability of 76%.

Proton Transport, Electroosmotic Drag and Oxygen Permeation in Polytetrafluoroethylene Reinforced Ionomer Membranes and Their Effects on Fuel Cell Performance

Abstract With the increasing need for high power density of proton exchange membrane fuel cells, new composite membranes have been explored for superior proton transport and gas impermeability. These membranes’ physicochemical properties usually deviate from existing empirical formulas, which are poorly understood, especially when mechanical deformation occurs. This poor understanding hinders development of novelty membranes and their fuel cell applications. Here, using polytetrafluoroethylene reinforced ionomer membrane as an example, we conducted extensive water absorption experiments to determine hydration levels at different water activities. Molecular dynamics simulations and electrochemical impedance spectroscopy were used to investigate the impacts of hydration level, external electric field strength, and tensile deformation on proton transport and electroosmotic drag coefficient, as well as the impact of hydration level and free volume ratio on oxygen permeability. We proposed mathematical correlations for these impacts and incorporated them into a single-cell voltage model to analyze their effects on fuel cell performance. Results show that an increase in the electric field strength alters the proton transport pattern, but has minimal impact on the electro-osmosis coefficient. The oxygen permeability coefficient of a deformed membrane with a free volume ratio of 28.57% is more than two orders of magnitude higher than that of a non-deformed membrane. The electro-osmatic drag coefficient imposes a larger influence on fuel cell performance than oxygen permeability

Rearrangement of the Conformations of Polyampholitic Macromolecules on the Surface of a Charged Spherical Metal Nanoparticle in an Alternating Electric Field: Molecular Dynamic Simulation

The rearrangement of the conformational structure of polyampholytic polypeptides on the surface of a charged spherical gold nanoparticle with its polarity intermittently changing over time was studied using molecular dynamics modeling. The angular distributions of the polypeptide atoms, as well as the radial distributions of the macrochain atomic density in the equatorial region of the nanoparticle with differentiation according to the types of links, were calculated. The polyampholyte shell acquired an annular shape, and the resulting macromolecular ring was located around the charged nanoparticle perpendicularly to the vector of the external electric field strength. With an increase in the charge of the nanoparticle, the ring belt was ordered according to the types of macrochain links, forming concentric annular layers. The diameter of the macromolecular ring depended on the law of distribution of charged units in the macrochain. At elevated temperatures the annular macromolecular ring was deformed at the moments of the highest polarization of the nanoparticle.

Effects of Oxygen Flow during Fabrication by Magnetron Sputtering on Structure and Performance of Zr-Doped HfO2 Thin Films.

Oxygen defects in Hafnium Oxide (HfO2)-based ferroelectric thin films not only are related to the cause of ferroelectricity but also affect the ferroelectric properties of the thin films. This paper, therefore, focuses on the fabrication of Zr:HfO2 thin films by RF (Radio Frequency) magnetron sputtering with Zr-doped HfO2 as the target and examines how oxygen flow impacts the oxygen vacancies and electrical properties thereof. Additionally, TiN thin-film electrodes were prepared by direct current (DC) magnetron reactive sputtering using nitrogen as the reaction gas, the influences of the substrate temperature on the film deposition rate and crystal phase structure were investigated, and the resultant thin-film electrodes with the lowest resistivity were obtained. Furthermore, the ferroelectric hysteresis loop and leakage current density of metal-insulator-metal (MIM) ferroelectric capacitors formed by annealing the 30 nm thick deposited Zr:HfO2 sandwiched between the top and bottom TiN electrodes were measured. The results demonstrate that varying oxygen flow has a considerable effect on oxygen vacancies and the Zr doping concentration of deposited Zr:HfO2 ferroelectric thin films. When the oxygen flow is set to 40 sccm (standard cubic centimeters per minute) and an external electric field strength of 2 mV/cm is applied, the remnant polarization reaches 18 μC/cm2, with a decrease in the leakage current density of 105-6 orders of magnitude.

Numerical Study of Free-Surface Electro-Hydrodynamic Wave Turbulence

Direct numerical simulation of threedimensional chaotic motion of a dielectric liquid with a free surface under the action of external horizontal electric field is carried out. The numerical model takes into account the effects of surface tension, viscosity, and external isotropic random forcing acting at large scales. A transition from dispersive capillary wave turbulence to quasi-isotropic nondispersive EHD surface turbulence with increase of the external electric field strength is numerically observed for the first time. At the regime of developed EHD wave turbulence, the total electrical energy is found to be much greater than the energy of capillary waves, i.e., electrohydrodynamic effects play a dominant role. At the same time, anisotropic effects are detected that lead to the generation of capillary wave packets traveling perpendicular to the external field direction. Despite the revealed anisotropy, the calculated spectrum of EHD wave turbulence is in very good agreement with the analytical spectrum obtained on the basis of dimensional analysis of weak turbulence spectra.

Electric Field‐Induced Phase Transition on HPX6 (X = C, Si, Ge, Sn) Monolayers

Herein, the electronic, thermoelectric, and optical properties of semimetallic HPX6 (X = C, Si, Ge, Sn) monolayers are systematically studied under the influence of external electric field in the framework of density functional theory. A band tuning has been achieved in these structures by the application of an external electric field of appropriate strength. It is predicted that Dirac cone splitting is nearly proportional to the external electric field strength. The modulation of electric properties induced by external field can alter the position of chemical potential in the band diagram and brings significant improvement in thermoelectric responses. The application of an external electric field significantly modulates the optical properties. The electric field‐induced HPX6 system provides better thermoelectric and optical response for nanodevice applications.

Influence of the Electric Field on the Properties of Hydrogenated Graphene

Graphene is currently considered as one of the most promising materials for the creation of new semiconductor devices for various frequency ranges . The influence of an external electric field on the properties of the band diagram of the graphene material , which is a modification of graphene using hydrogen atoms , was studied by simulating from the first principles ( ab initio method ). It was found that an external electric field applied to the graphene structure leads to a substantial change in its band diagrams , which is associated with a change in their type . At small values of external electric field strength , approximately up to 0.3 a.u . (1 a.u . ≈ 51.4 1010 V/m), we observe graphane zone diagrams with straight minimal gap for Г valley between conduction and valence zones . With further increase in external electric field strength the zone diagrams show indirect minimal gap . With even higher values of external electric field strength , which exceed 0.8 a.u ., graphane band diagrams take on a form peculiar to metallic structures . These dependences and the resulting graphene parameters could be the basis for new heterostructure devices containing layers of graphene and other semiconductor materials .

Time evolution of electron distributions to bimodal steady states for electrons dilutely dispersed in theinert gases Ar, Kr, and Xe with deep Ramsauer Townsend minima in themomentum transfer cross section

The current paper considers the thermalization of an ensemble of electrons under the influence of an external electric field and dilutely dispersed in one of the inert gas moderators, Argon, Krypton or Xenon for which the electron momentum transfer cross sections have deep Ramsauer-Townsend minima. As a consequence, the steady state electron distribution functions are bimodal over a small range of external electric field strengths. The current work is directed towards the time evolution of the electron distribution function determined from the numerical solution of the Fokker-Planck equation. The kinetic theory of electrons dilutely dispersed in a heat bath of atoms at temperature T b has a very long history. The solution of the Fokker-Planck equation can be expressed as a sum of exponentials of the form where λ n are the eigenvalues of the Fokker-Planck operator. Alternatively, a finite difference algorithm is used to solve the time dependent Fokker-Planck equation to give the time dependent electron energy distribution function. We demonstrate the evolution of the initial Maxwellian into a nonequilibrium bimodal distribution which cannot be rationalized with either the Gibbs-Boltzmann entropy or the Tsallis nonextensive entropy. Instead, the time dependent approach of an initial Maxwellian to the bimodal distribution is described in terms of the Kullback-Leibler entropy. We also demonstrate the inapplicability of the Boltzmann entropy nor the Tsallis entropy for a model system with a power law momentum transfer cross section of the form, σ(x) = σ 0/x p , where is the reduced speed. This model with p = 2 is also employed to demonstrate a steady-state Kappa distribution which features prominently in space physics and other fields. For p > 2, we show distribution functions that increase without bound analogous to runaway electrons. The steady nonequilibrium distributions are interpreted as solutions of a Pearson ordinary differential equation.

About switching of polarization in a thin ferroelectric film

By using the Ginzburg–Landau theory in the nonlinear case, the shape of the inverse domain nucleus in a thin ferroelectric film in a weak electric field is determined. The dependencies of the critical size of the inverse domain nucleus on the film thickness, the strength of external electric field, the temperature and the parameter [Formula: see text], which determines the polarization pinning at the film planes, are calculated. We have established that when the parameter [Formula: see text] increases above a certain critical value, which depends on film thickness and external field strength, the polarization switches uniformly without domain formation. In the framework of Zeldovich theory of nucleation, the average repolarization velocity has been determined as a function of the film thickness, the external field strength and the parameter [Formula: see text].

Heat transfer and electro-osmotic analysis on peristaltic pumping of a fractional second-grade fluid through a cylindrical tube

Most of the earlier studies intended on the peristaltic pumping of non-Newtonian fluids via channels/tubes to better know the flow activities of flowing systems. The extant effort is modeled to examine the peristaltic motion of the viscoelastic fluid through a cylindrical tube to characterize the rheological features of blood in the vascular system by incorporating the electro-osmotic phenomenon. Caputo’s definition provides analytical solutions to the dilemma. To evaluate the potential function, the Debye–Huckel linearization approximation is utilized. The long-wavelength [Formula: see text] and low Reynolds number approximations [Formula: see text] are used to simplify the simultaneous equations. The effects of physical constraints depicting the flow phenomena are obtained and conferred via graphs. The impact of several regulatory elements is deliberated and exposed in a succession of figures. The significant outcome of the result is that the pressure gradient is consistently enhanced as the external electric field strength increases. It is also observed that the growing applied electric field strength can control the negative value of the pressure gradient. This work is relevant to the electrophoresis in hematology, electrohydrodynamic therapy, and biometric electro-osmotic pumps. The present results provide a significant baseline for experiment analyses and more general models of microvascular blood flow.

Tunable Schottky barrier of WSi2N4/graphene heterostructure via interface distance and external electric field

Improving the electric transport of field-effect transistors based on heterostructure (HTS) is a stern challenge by the reduction of the interfacial barrier. Herein, the electronic properties of WSi2N4/graphene HTS with different interface distance or external electric field are researched in detail using the first-principles approach. The result shows that a stable vdW HTS can be produced between WSi2N4 and graphene. In the interface, the tunable range of Schottky barrier height by external electric field exceeds that by interface distance, although both of two prominent approaches can modulate the energy band structures of WSi2N4/graphene HTSs. The transformation of Schottky contact from p-type to n-type, eventually into Ohmic contact can appear under external electric field. Predictably, the positive external electric field strength of 0.55 V·Å−1 can generate the largest carrier concentration 2.73 × 1013 cm−2 of graphene in the HTS. Verifiably, the redistribution of interface charge density determines the Schottky barrier height and contact type in the HTS. These findings present the potential of WSi2N4/graphene HTS as high sensitive Schottky field-effect transistors.

Frustrated amino functional group coupling with electric field makes CO2 activation easier.

New models associated with frustrated geometry and an external electric field (EEF) were designed to qualitatively and quantitatively explore CO2 activation through density functional calculations. We investigated the influence on CO2 of the microenvironments of methylamine (CH3NH2) positioned at different heights above a Cu (111) surface in the presence and absence of an electric field. The results demonstrate that at an approximate distance of 4 ± 1 Å between N and the metal surface, neither lower nor higher, under an EEF over 0.4 V Å-1, there is a remarkable synergistic effect between the chemical interaction and EEF that activates CO2, and also lowers the required EEF strength. This is in contrast to the separate factors or any other combinations of them which do not achieve the synergistic effect. In addition, when H in was replaced by F, the O-C-O angle of CO2 is not affected. This phenomenon further illustrates that the synergistic effect is very sensitive to the nucleophilicity of NH2. Various other chemical groups and substrates were investigated, and PHCH3 also displays a distinctive chemisorption CO2 state. The substrate also plays a significant role, except that Au cannot generate a similar effect. Furthermore, constraining or facilitating CO2 activation strongly depends on the distance between the chemical group and the substrate. Appropriate combinations of the three factors related to the substrate Cu, the chemical group CH3NH2 and the EEF provide new protocols to make CO2 activation easier and controllable.

An ab-initio perspective on the electronic and optical characteristics of MoSe2 nanosheet: Role of external electric field

The presence of an external electric field has a large influence on the properties of low-dimensional materials. Here, we examine the change of the band gap (Eg), the optical absorption coefficient (OAC), the refractive index (RI), and the optical conductivity of a monolayer MoSe2 (ML) with respect to the variation in the external electric field strength. Our results, based on a density-functional theory (DFT) calculation, exhibit an increase in the band gap when the electric field is turned on. However, we are witnessing a remarkable decrease in Eg for electric field strengths exceeding ±0.7VÅ−1. Further, we obtained a great correlation between the external electric field and the OAC. On the other hand, we have established that the light polarization perpendicular to the plane of the ML-MoSe2 shifts the position of the OAC peak to shorter wavelengths, and leads to a split of OAC peak located at 110nm. We have also achieved that the external electric field reduces the optical conductivity of the ML-MoSe2 in the UV region. That effect is found to be more pronounced when the MoSe2 nanosheet is subjected to a 001-polarized incident light and positive field strengths. However, the presence of an external electric field generally improves the optical conductivity in the visible region. Lastly, in the case of 001-polarization of the incident wave, we found that the RI shrinks in the UV region when the electric field is turned on. By contrast, the application of an external electric field tends to improve the refractive index in the visible region.

Electrical Phenomena on Fully Airborne Vertical Electric Antennas in Extreme Weather Conditions

This is a conference extension of the paper ‘Investigation on the mature storm cloud’s electric field using long airborne antennas’. The use of vertical antennas (including the VEDs—Vertical Electric Dipoles), lifted up by aerostats to high altitudes without being anchored to the ground, presents numerous advantages in comparison with large terrestrial VLF (Very Low Frequency) antenna structures. A slow-moving floating-earth conductor—a vertical wire antenna—is subjected to intense electrification mechanisms in the atmosphere and inside the cloud layers, producing additional risks for the transmitter and the flight train itself. The electrical potential achieved in this process is, therefore, compared with the flashover voltages over the antenna’s upper fixing point, defining the voltage margins at which the VLF transmitter is able to operate. The electrification processes are also compared to the model based on experimental data on the occurrence of corona discharges over a long, vertical wire traversing a storm cloud layer. The external electric field strength (around the antenna wire) is calculated and compared with older experimental data for storm clouds for various locations, showing the correctness of the proposed analytical electrification model, and, therefore, expanding it with the loss of the electric charge via corona.

Corona Resistance Mechanism of Nano-Modified Polyimide.

In this paper, the effect of field strength on the corona-resistant lifespan of a composite film and the effect of doping on the dielectric properties of the composite film were studied. The method for predicting corona-resistant lifespan under working electric field strength is discussed. Scanning electron microscopy (SEM) was used to characterize the morphology and the structure of the composite film near the breakdown point after corona formation. Fourier transform infrared spectroscopy (FT-IR) was used to characterize the imidiated film, and a conductivity current test was used to calculate the electrical aging threshold of the film. The results showed that the introduction of nano-SiO2 particles could greatly improve the corona-resistant lifespan of the material. At 155 °C, when the applied external electric field strength was extrapolated to 20 kV/mm, the corona-resistant lifespan of the PI/nano-SiO2 three-layer composite film with 10 wt% nano-particle doping was 7472.61 h.

Generation of electric-field-induced anti-Stokes Raman scattering in the visible region (E-CARSv) from nitrogen in air

Electric-field-induced anti-Stokes Raman scattering in the visible region (E-CARSv) is a third-order nonlinear optical effect used for measuring electric field sensitively, especially at atmospheric or higher pressure. This study demonstrated E-CARSv generation from nitrogen molecules using a visible laser at 532 nm, a tunable infrared laser at approximately 4.3 μm, and an applied DC electric field. The results revealed that the square root of the signal intensity was proportional to the external electric field strength, which corresponded with the theoretical prediction. E-CARSv can be applied to a wide range of mediums containing nitrogen molecules, including plasmas generated in an open-air environment.

Structural properties of a chain of dust particles in a field of external forces.

This paper presents a numerical study of the structural parameters of a one-dimensional chain of three dust particles levitating in the near-electrode layer of an rf discharge or in the stratum of a dc discharge. The model considers the motion of dust particles under the action of gravity, external electric field, the Coulomb repulsion, and the electrostatic force from the space charge surrounding the dust particles. Particular attention is paid to the effect of plasma polarization around dust particles and the wake formation under the action of the external electric field. Calculations showed that the charge of the first dust particle in the chain and the total charge of the entire chain, as well as the length of the chain, grow linearly with the external electric field strength. Obtained data are in qualitative agreement with the experimental and numerical data presented in the literature. It was shown that for a certain large value of the external electric field, the charge of the third dust particle is the smallest of all the particles in the chain. It was found that with an increase in the mean value of the external electric field, the chain of dust particles is displaced as a whole in the direction opposite to the action of the electrostatic force on them.

Evaluation of the thermoelectric properties of a nanoscale device in the presence of an external electric field: Tight binding model

In this paper, we present a tight-binding model for investigating the thermoelectric properties of a molecular scale junction under an external electric field (EF). Such junction is made of a chain of benzene rings (oligophenylene) connected to similar metallic electrodes. Using the Landauer formalism within the framework of Green's function method, electrical transport properties, including the Seebeck coefficient (S), the electrical conductivity (Ge), the thermal conductivity (K), and the figure of merit (ZT), are numerically calculated. It is shown that all thermoelectric characteristics are depended on the external EF strength and change the thermoelectric performance in the organic molecule. As a result, at room temperature T=300 K and zero EF, the maximum value of ZT is about 0.8, reaching almost 1.2 when EF=0.4 V/Å.

Determining dielectric properties of nematic liquid crystals at microwave frequencies using inverted microstrip lines

ABSTRACT In this paper, we have investigated the dielectric properties of nematic liquid crystals (NLCs) by measuring the resonant frequencies of inverted microstrip lines (IMSLs) of NLC being the substrate material at the microwave frequency band. The designed IMSL devices consist of a cavity for NLC mixture between the inverted microstrip line and the ground plane. The anisotropy values of the NLCs were determined by observing the change of the resonant frequency when the strength of external electric fields applied on the NLCs varied. The experiments demonstrated that the effective dielectric constant of the NLC can be manipulated by the proposed devices via external bias voltage for tuning. The accuracy of the method for determining the dielectric constants of JC-M-LC-E7 (JC-E7) and QYPD-036 LCs was analysed with several prototypes based on two separate designs. The high accuracy of 91% in permittivity determination was demonstrated, and the design and fabrication techniques are beneficial for making microwave components of high tunability.

Orientation Polarization Spectroscopy-Toward an Atomistic Understanding of Dielectric Relaxation Processes.

The theory of orientation polarization and dielectric relaxation was developed by P. Debye more than 100 years ago. It is based on approximating a molecule by a sphere having one or more dipole moments. By that the detailed intra- and intermolecular interactions are explicitly not taken into consideration. In this article, the principal limitations of the Debye approximation are discussed. Taking advantage of the molecular specificity of the infrared (IR) spectral range, measurements of the specific IR absorption of the stretching vibration υ(OH) (at 3370 cm−1) and the asymmetric υas(CH2) (at 2862.9 cm−1) are performed in dependence on the frequency and the strength of external electric fields and at varying temperature. The observed effects are interpreted as caused by orientation polarization of the OH and the adjacent CH2 moieties.