Range Of Electric Field Strengths Research Articles

Electrorheological behavior of low filled suspensions of highly anisometric montmorillonite particles

ABSTRACTThe electrorheological (ER) behavior of modified montmorillonite (MMT) suspensions in polydimethylsiloxane is studied. As established by rotational viscometry, the samples with a dispersed phase concentration from 1 to 8 wt % reveal viscous Newtonian behavior and dramatically change their properties to elastic when electric field is applied. The rheological characteristics of the suspensions over 0–7 kV mm−1 range of electric field strengths are also studied. Novel X‐ray diffraction method is developed to evaluate the suspension of the filler in a siloxane medium and to calculate the degree of its exfoliation. The dependence of exfoliation degree, dielectric, and ER characteristics on the type of modifier in the MMT structure is considered. Based on the obtained data, a new model of system behavior with the various types of fillers is proposed and the prospects of utilizing MMT as a filler for ER fluids are demonstrated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47678.

Electroporation of Ishikawa cells: analysis by flow cytometry.

Electroporation facilitates loading of cells with molecules and substances that are normally membrane impermeable. Flow cytometry is used in this study to examine the effects of the application of electroporation-level monopolar electric field pulses of varying electrical field strength on Ishikawa endometrial adenocarcinoma cells. Analysis of the fluorescence versus forward scatter plots corroborates the well-recognised threshold and cell size dependence characteristics of electroporation, but also shows the progression of cell lysis and generation of particulate material. Two 500 µs monopolar rectangular pulses ranging from 1.0 × 105 to 2.5 × 105 V/m were used to electroporate the cells. Electroporation yields (fraction of viable cells exhibiting significant propidium iodide uptake) ranged from 0 to 97%, with viability ranging between 78 and 34% over the electric field strength range tested. The higher electric field strength pulses not only reduced cell viability, but also generated a substantial amount of sub-cellular sized particulate material indicating cells have been physically disrupted enough to create these particles.

Field-dependent electric conductivities of silicone rubbers deduced from measured currents and surface potential decay characteristics

Measurements of DC electric conductivities of four types of silicone rubber-based polymers for use in high voltage insulation systems of power components are reported. The field dependences of the conductivities obtained by two different techniques, namely by utilizing steady-state currents through materials’ samples placed between metallic electrodes and by employing surface potential decay characteristics in an open circuit configuration, are compared and discussed. It is shown that the surface potential decay technique allows for a wider range of electric field strength and reduces the time span of the measurements.

Yield and Reliability of Nanocrystalline Graphene Field-Effect Gas Sensors

For the development of next-generation gas sensors with higher sensitivity, selectivity, responsivity and cost-effectiveness, carbon-based materials are a major research topic. Graphene, as a two-dimensional nanomaterial with a high surface-to-volume ratio and outstanding electronic properties, offers a good choice as a sensing layer [1]. However, for the successful application of reasonably priced graphene-based gas sensors a high fabrication yield and long-term stability are essential key requirements. Nevertheless, only few studies on the yield and reliability of graphene-based devices do exist [2]. Transfer-free nanocrystalline graphene field-effect transistors (ncGFETs), which are sensitive towards various toxic gases, including ammonia (NH3), nitrogen dioxide (NO2) and carbon monoxide (CO) can be fabricated by the use of our CMOS-compatible in situ catalytic chemical vapor deposition (CCVD) process. By this method we have fabricated hundreds of devices on oxidized two inch silicon wafers. In this contribution we report results on process yield and reliability, obtained from backgate input characteristics of 524 devices fabricated on a single two inch wafer. Electrical characterization has been performed using a Keithley SCS 4200 semiconductor parameter analyzer. The characterized ncGFETs exhibit nominal device widths of 20 µm and lengths of 3 µm and have been parameterized at a drain-to-source bias of VDS = -300 mV. The measurements reveal that 81.68 % of the fabricated ncGFETs show typical ambipolar behavior as is known from graphene devices (fig. 1). A field-effect (FE), defined via current on/off ratio, of at least 2 is observed for all of the devices within a backgate electric field strength range of ±2.4 MV/cm. Beyond that, in these devices larger field-effects are observed with 59.81 % exceeding a field-effect of 10 to 15 (10 ≤ FE < 15), 24.3% between 15 and 20 (15 ≤ FE < 20) and 7.25% larger than 20 (FE ≥ 20) (fig. 2). Due to the differences in the strength of the field-effect, material variations of our nanocrystalline graphene are expected. Moreover, by means of a statistical evaluation of the shift of the charge neutrality point the different doping levels of our devices are investigated. Furthermore, the ncGFETs show hysteresis effects that are enhanced by exposure to atmospheric environment and other gases, but are reduced in vacuum. Using the Pulsed Time-Domain Measurement (PTDM) technique [3] the surface charge trap density, which induces the hysteresis, is determined for various cases and its influence on the electrical and sensing characteristics of our device will be discussed. In addition, results on accelerated stress tests at high electrical fields and elevated temperatures will be presented as a first attempt to investigate the degradation and reliability of ncGFETs. [1] F. Schedin, A. K. Geim, S. V. Morozov, E. W. Hill, P. Blake, M. I. Katsnelson and K. S. Novoselov, Nat Mater, 6, 652 (2007). [2] A. D. Smith, S. Wagner, S. Kataria, B. G. Malm, M. C. Lemme and M. Ostling, Ieee T Electron Dev, 64, 3919 (2017). [3] R. S. Park, M. M. Shulaker, G. Hills, L. Suriyasena Liyanage, S. Lee, A. Tang, S. Mitra and H. S. Wong, ACS Nano, 10, 4599 (2016). Figure 1

Controlling Protein Orientation in Vacuum Using Electric Fields.

Single-particle imaging using X-ray free-electron lasers is an emerging technique that could provide high-resolution structures of macromolecules in the gas phase. One of the largest difficulties in realizing this goal is the unknown orientation of the individual sample molecules at the time of exposure. Preorientation of the molecules has been identified as a possible solution to this problem. Using molecular dynamics simulations, we identify a range of electric field strengths where proteins become oriented without losing their structure. For a number of experimentally relevant cases we show that structure determination is possible only when orientation information is included in the orientation-recovery process. We conclude that nondestructive field orientation of intact proteins is feasible and that it enables a range of new structural investigations with single-particle imaging.

Modeling SiO2 leakage currents caused by electrical overloads

A two-component model for the formation of leakage currents in SiO2 in a strong electric field is proposed. In the model, agreement is found between the theoretical and experimental values of leakage currents in a wide range of electric field strength and the size of charge transferred.

Analysis of the static yield stress for giant electrorheological fluids

Cheng et al. (2010)'s experimental results for the static yield stress of giant electrorheological (GER) fluids over the full range of electric field strengths were reanalyzed by applying Seo’s scaling function which could include both the polarization and the conductivity models. The Seo’s scaling function could correctly fit the yield stress behavior of GER suspensions behavior after if a proper normalization of the yield stress data was taken which collapse them onto a single curve. The model predictions were also contrasted with recently proposed Choi et al.’s scaling function to rouse the attention for a proper consideration of the GER fluid mechanisms.

High-resolution study of the yellow excitons inCu2Osubject to an electric field

We have used high resolution transmission spectroscopy to study the exciton level spectrum in Cu$_2$O subject to a longitudinal external electric field, i.e., in the geometry where the transmitted light is propagating along the field direction. Different experimental configurations given by the field orientation relative to the crystal and the light polarization have been explored. We focus on the range of small principal quantum numbers $n \leq 7$. The number of exciton states belonging to a particular principal quantum number increases with $n$, leading to an enhanced complexity of the spectra. Still, in particular for $n = 3 \ldots 5$ a spectral separation of the different lines is feasible and identification as well as assignment of the dominant state character are possible. We find a strong dependence of the spectra on the chosen light propagation direction and polarization configuration, reflecting the inadequacy of the hydrogen model for describing the excitons. With increasing the field excitonic states with different parity become mixed, leading to optical activation of states that are dark in zero field. As compared with atoms, due to the reduced Rydberg energy states with different $n$ can be brought into resonance in the accessible electric field strength range. When this occurs, we observe mostly crossing of levels within the experimental accuracy showing that the electron and hole motion remains regular. The observed features are well described by detailed calculations accounting for the spin-orbit coupling, the cubic anisotropy effects, and the symmetry-imposed optical selection rules.

Single-step electrical field strength screening to determine electroporation induced transmembrane transport parameters

The design of effective electroporation protocols for molecular delivery applications requires the determination of transport parameters including diffusion coefficient, membrane resealing, and critical electric field strength for electroporation. The use of existing technologies to determine these parameters is time-consuming and labor-intensive, and often results in large inconsistencies in parameter estimation due to variations in the protocols and setups. In this work, we suggest using a set of concentric electrodes to screen a full range of electric field strengths in a single test to determine the electroporation-induced transmembrane transport parameters. Using Calcein as a fluorescent probe, we developed analytical methodology to determine the transport parameters based on the electroporation-induced pattern of fluorescence loss from cells. A monolayer of normal human dermal fibroblast (NHDF) cells were pre-loaded with Calcein and electroporated with an applied voltage of 750V with 10 and 50 square pulses with 50μs duration. Using our analytical model, the critical electric field strength for electroporation was found for the 10 and 50 pulses experiments. An inverse correlation between the field strength and the molecular transport time decay constant, and a direct correlation between field strength and the membrane permeability were observed. The results of this work can simplify the development of electroporation-assisted technologies for research and therapies.

Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation.

Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media.

Impact Ionization Coefficients in 4H-SiC Toward Ultrahigh-Voltage Power Devices

A temperature dependence of impact ionization coefficients in 4H-SiC was studied in a wide range of electric field toward the accurate designing of ultrahigh-voltage devices. The photomultiplication measurement was conducted for various photodiodes with different multiplication layer structures to obtain multiplication factors and ionization coefficients in a wide range of electric field strength. Especially, using multiplication layer structure with low doping concentration, the hole impact ionization coefficient was extracted at low electric field of 1 MV/cm. In high-temperature measurement, the hole ionization coefficient decreased with the increase of temperature, as observed in other semiconductor materials. For the electron ionization coefficient, however, its temperature dependence was very small and values obtained at room temperature could be used, at least up to 150 °C.

Piezoelectric effect on the intrinsic dissipation in oscillating gallium nitride nanobelts

The intrinsic dissipation in oscillating gallium nitride (GaN) nanobelts subject to an electric field has been examined using molecular-dynamics simulations. Owing to the piezoelectric effect of GaN nanobelts, their quality factor is greatly influenced by the electric field and can be improved by over 10 times across a range of electric-field strengths. In addition, the temperature dependence of the quality factor is also significantly affected by the applied electric field. Some possible explanations as to how the piezoelectric effect influences the intrinsic energy loss are proposed based on the classical thermoelastic dissipation theory.

Innovative approach to determine the effect of pulsed electric fields on the microstructure of whole potato tubers: Use of cell viability, microscopic images and ionic leakage measurements

The aim of this study was to gain an in-depth understanding of the effect of pulsed electric fields (PEF) on the microstructure of potato tubers. The effect of peeling prior to PEF was also studied. Whole potato tubers were subjected to PEF at a constant frequency of 50Hz, over a range of electric field strengths (0.2 to 1.1kV/cm) and energy levels (1 to 10kJ/kg). To determine the uniformity of the PEF effect across the potato tuber, cell viability was assessed using tetrazolium salt staining. To evaluate the effectiveness of PEF processing the leakage of ionic species from the tubers was measured using atomic absorption spectrophotometry and FESEM-EDS analysis. In addition the influence of PEF on cell disruption and microstructural damage was assessed using scanning electron microscopy (Cryo-SEM). As the electric field strength and energy increased potassium ion leakage and electrical conductivity of the medium increased. The orientation of the tuber towards the electrodes and the presence of the skin greatly affected the impact of PEF on cell disruption and viability. At electric field strengths of 0.3kV/cm and above, potato cells located in the pith (inner medulla) showed more damage and had a higher proportion of cell death compared to cells located in the outer medulla. This is the first study to provide visual evidence that the application of electric fields to solid, living foods, such as potato tubers, results in an uneven distribution of cell damage and death owing to the presence of vascular bundles and cells that vary in their resistance to electric fields.

Principle of radial transport in low temperature annular plasmas

Radial transport in low temperature annular plasmas is investigated theoretically in this paper. The electrons are assumed to be in quasi-equilibrium due to their high temperature and light inertial mass. The ions are not in equilibrium and their transport is analyzed in three different situations: a low electric field (LEF) model, an intermediate electric field (IEF) model, and a high electric field (HEF) model. The universal IEF model smoothly connects the LEF and HEF models at their respective electric field strength limits and gives more accurate results of the ion mobility coefficient and effective ion temperature over the entire electric field strength range. Annular modelling is applied to an argon plasma and numerical results of the density peak position, the annular boundary loss coefficient and the electron temperature are given as functions of the annular geometry ratio and Paschen number.

Graphene oxide/poly(2-methylaniline) composite particle suspension and its electro-response

Graphene oxide (GO)/poly(2-methylaniline) (P2MAN) composite particles were prepared by chemical oxidation polymerization and adopted as an electrorheological (ER) material. Because of its electrical conductivity originating from both semi-conducting P2MAN and GO, it could be tuned finely using P2MAN for ER applications. The morphology and chemical structure of the composite were examined by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The ER properties of the GO/P2MAN composite particles dispersed in silicone oil were examined with and without an applied electric field. The fibrillation phenomenon of this GO/P2MAN-based electro-responsive fluid was also observed by optical microscopy under an electric field. The flow curves and dynamic modulus of the GO/P2MAN suspension were measured by rotational rheometry under a range of electric field strengths, exhibiting typical ER characteristics and a slope of the dynamic yield stress of 1.5. GO appeared to improve the compatibility of the composite particles within the medium, which resulted in improved sedimentation stability compared to that of the P2MAN-based ER fluid.

Monte-Carlo study of electron noise in compensated InSb

The results of Monte Carlo simulations of the electron noise in lightly doped and strongly compensated n-type InSb are presented. The strong electron scattering by ionized impurities is established to change essentially the electron distribution function, spectral density of velocity fluctuations and the dependence of noise temperature on the electric field strength. It is found that the electron noise temperature in strongly compensated InSb with low electron density at liquid nitrogen temperature is close to the lattice temperature in a wide range of electric field strength in which the electron gas cooling effect takes place. The increase of electron density is shown to weaken the electron gas cooling effect due to more intensive electron–electron collisions stimulating delocalization of electrons from the bottom of the conduction band. A satisfactory agreement between calculations and available experimental data is obtained.

Monte-Carlo simulation of microwave noise in n-type InSb

Numerical Monte Carlo calculations of the electron noise temperature dependence on the electric field strength in n-type InSb are presented. It is established that hot electron noise temperature in strongly compensated InSb increases with the increase of electron density due to more intensive electron–electron scattering stimulating delocalization of electrons from the bottom of the conduction band. For low electron density, when the electron–electron scattering is negligibly small, the electron noise temperature is found to become close to the lattice temperature in a wide range of electric field strength in which the electron gas cooling effect takes place. Satisfactory agreement between calculations of the electron noise temperature and available experimental data has been obtained.

An analytical approach for calculating energy spectra of relativistic runaway electron avalanches in air

AbstractSimplified equations describing the transport and energy spectrum of runaway electrons are derived from the basic kinematics of the continuity equations. These equations are useful in modeling the energy distribution of energetic electrons in strong electric fields, such as those found inside thunderstorms. Dwyer and Babich (2011) investigated the generation of low‐energy electrons in relativistic runaway electron avalanches. The paper also developed simple analytical expressions to describe the detailed physics of Monte Carlo simulations of relativistic runaway electrons in air. In the current work, the energy spectra of the runaway electron population are studied in detail. Dependence of electron avalanche development on properties such as the avalanche length, radiation length, and the effective Møller scattering efficiency factor are discussed in detail. To describe the shapes of the electron energy spectra for a wide range of electric field strengths, the diffusion term responsible for random deviation of electron energy ionization loss from the mean value is added to the kinetic equation. We find that the diffusion in energy space helps maintain an exponential energy spectrum for electric fields that approach the runaway electron threshold field.

The isolated head model of the plasma bullet/streamer propagation: electric field-velocity relation

A model of the isolated streamer head based on Meek's criterion of the avalanche to streamer transition is applied for description of the plasma bullet propagation in a helium/air admixture. According to the model previously proposed by Kulikovsky for streamers in air, along with the knowledge of one of three parameters: electric field, ionization integral or the width of the space charge layer, the other two parameters could be determined. Furthermore, using the streamer current or radius, it is possible to determine the electric field-streamer velocity functional dependence. Obtained results showed satisfactory agreement with both the results of the fluid model from the literature and the experimental results of plasma jet studies. Finally, for the sake of comparison, streamer velocity dependence on the electric field strength range of 10–250 kV cm−1 is determined for helium, argon and air.

The resistivity of oil and oil-impregnated pressboard varies with temperature and electric field strength

The mineral insulating oil and pressboard are important insulation dielectrics in AC-DC converter transformers. Thus, it is very significant to understand the dielectric properties of the oil and oil-impregnated pressboard. In this paper, the influences of the temperature, field strength and aging on the resistivity of oil and oil-impregnated pressboard have been investigated. Samples used in the experiments are new oil, aged oil, pressboard immersed in new oil and aged oil respectively. The measuring device of resistivity was full of oil and isolated from outside. All samples were measured at temperature range of 25-80 °C under the electric field strength range of 2-10 kV/mm for oil and 3-30 kV/mm for oil-impregnated pressboard. The results showed that the resistivity of oil-impregnated pressboard decreased along with the increase of field strength and temperature. For all oil specimens and pressboard immersed in aged oil, the resistivity decreasing rate (|∂1gρ / E∂|) along with electric field strength showed a downtrend with the increase of temperature; while, for pressboard immersed in new oil, the decreasing rate showed an uptrend with the increase of temperature. For oil, the resistivity reduction rate with aging (r) decreased along with the increase of field strength and temperature. For pressboard immersed in oil, the reduction rate with aging (r) showed an uptrend with the increase of temperature.