scholarly journals Steady-State Conduction Current Performance for Multilayer Polyimide/SiO2 Films

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 640 ◽  
Author(s):  
Muhammad Shoaib Bhutta ◽  
Shakeel Akram ◽  
Pengfei Meng ◽  
Jerome Castellon ◽  
Serge Agnel ◽  
...  
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Dielectric Strength ◽  
High Electric Field ◽  
Nanocomposite Films ◽  
Conduction Current ◽  
Different Temperatures ◽  
Insulation Systems ◽  
Lower Temperature

The steady-state electrical conduction current for single and multilayer polyimide (PI) nanocomposite films was observed at the low and high electric field for different temperatures. Experimental data were fitted to conduction models to investigate the dominant conduction mechanism in these films. In most films, space charge limited current (SCLC) and Poole–Frenkel current displayed dominant conduction. At a high electric field, the ohmic conduction was replaced by current–voltage dependency. Higher conduction current was observed for nanocomposite films at a lower temperature, but it declined at a higher temperature. PI nanocomposite multilayer films showed a huge reduction in the conduction current at higher electric fields and temperatures. The conclusions derived in this study would provide the empirical basis and early breakdown phenomenon explanation when performing dielectric strength and partial discharge measurements of PI-based nanocomposite insulation systems of electric motors.

Numerical study of electric field effects on the deformation of two-dimensional liquid drops in simple shear flow at arbitrary Reynolds number

2009 ◽  
Vol 626 ◽  
pp. 367-393 ◽  
Author(s):  
STEFAN MÄHLMANN ◽  
DEMETRIOS T. PAPAGEORGIOU
Keyword(s):  
Steady State ◽  
Shear Flow ◽  
Electric Field ◽  
Electric Fields ◽  
Simple Shear ◽  
Simple Shear Flow ◽  
Physical Parameters ◽  
Shear Stresses ◽  
Two Dimensional ◽  
Liquid Drops

The effect of an electric field on a periodic array of two-dimensional liquid drops suspended in simple shear flow is studied numerically. The shear is produced by moving the parallel walls of the channel containing the fluids at equal speeds but in opposite directions and an electric field is generated by imposing a constant voltage difference across the channel walls. The level set method is adapted to electrohydrodynamics problems that include a background flow in order to compute the effects of permittivity and conductivity differences between the two phases on the dynamics and drop configurations. The electric field introduces additional interfacial stresses at the drop interface and we perform extensive computations to assess the combined effects of electric fields, surface tension and inertia. Our computations for perfect dielectric systems indicate that the electric field increases the drop deformation to generate elongated drops at steady state, and at the same time alters the drop orientation by increasing alignment with the vertical, which is the direction of the underlying electric field. These phenomena are observed for a range of values of Reynolds and capillary numbers. Computations using the leaky dielectric model also indicate that for certain combinations of electric properties the drop can undergo enhanced alignment with the vertical or the horizontal, as compared to perfect dielectric systems. For cases of enhanced elongation and alignment with the vertical, the flow positions the droplets closer to the channel walls where they cause larger wall shear stresses. We also establish that a sufficiently strong electric field can be used to destabilize the flow in the sense that steady-state droplets that can exist in its absence for a set of physical parameters, become increasingly and indefinitely elongated until additional mechanisms can lead to rupture. It is suggested that electric fields can be used to enhance such phenomena.

scholarly journals Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

2016 ◽  
Vol 34 (1) ◽  
pp. 55-65 ◽  
Author(s):  
A. D. M. Walker ◽  
G. J. Sofko
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Field Line ◽  
Geomagnetic Field ◽  
Geomagnetic Field Models ◽  
Spatial Derivatives ◽  
Field Lines ◽  
The Magnetic Field

Abstract. When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the position of a satellite. Such mapping is relatively easy in a dipole field although the appropriate formulae are not easily accessible. They are derived and reviewed here with some examples. It is not possible to derive such formulae in more realistic geomagnetic field models. A new method is described in this paper for accurate mapping of electric fields along field lines, which can be used for any field model in which the magnetic field and its spatial derivatives can be computed. From the spatial derivatives of the magnetic field three first order differential equations are derived for the components of the normalized element of separation of two closely spaced field lines. These can be integrated along with the magnetic field tracing equations and Faraday's law used to obtain the electric field as a function of distance measured along the magnetic field line. The method is tested in a simple model consisting of a dipole field plus a magnetotail model. The method is shown to be accurate, convenient, and suitable for use with more realistic geomagnetic field models.

Properties of Space Charge Distributions and Conduction Current in XLPE and LDPE under DC High Electric Field

2016 ◽  
Vol 198 (3) ◽  
pp. 19-26 ◽  
Author(s):  
TSUYOSHI KATO ◽  
RYO ONOZAWA ◽  
HIROAKI MIYAKE ◽  
YASUHIRO TANAKA ◽  
TATSUO TAKADA
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
High Electric Field ◽  
Conduction Current ◽  
Charge Distributions

scholarly journals Influence of Different Solvents and High-Electric-Field Cycling on Morphology and Ferroelectric Behavior of Poly(Vinylidene Fluoride-Hexafluoropropylene) Films

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3884
Author(s):  
Till Mälzer ◽  
Lena Mathies ◽  
Tino Band ◽  
Robert Gorgas ◽  
Hartmut S. Leipner
Keyword(s):  
Phase Composition ◽  
Electric Field ◽  
Surface Structure ◽  
Electric Fields ◽  
Vinylidene Fluoride ◽  
High Electric Field ◽  
Crystal Phase ◽  
Shielding Effect ◽  
Ferroelectric Behavior ◽  
Field Cycling

P(VdF-HFP) films are fabricated via a solution casting doctor blade method using high (HVS) and low (LVS) volatile solvents, respectively. The structural properties and the ferroelectric behavior are investigated. The surface structure and crystal phase composition are found to be strongly dependent on the type of solvent. LVS leads to a rougher copolymer surface structure with large spherulites and a lower crystallinity in contrast with HVS. The crystalline phase of copolymer films fabricated with HVS consists almost exclusively of α-phase domains, whereas films from LVS solution show a large proportion of γ-phase domains, as concluded from Raman and X-ray diffraction spectra. Virgin films show no ferroelectric (FE) switching polarization at electric field amplitudes below 180 MV/m, independent of the solvent type, observed in bipolar dielectric displacement—electric field measurements. After applying electric fields of above 180 MV/m, a FE behavior emerges, which is significantly stronger for LVS films. In a repeated measurement, FE polarization switching already occurs at lower fields. A shielding effect may be related to this observation. Additionally, Raman bands of polar γ-phase increase by high-electric-field cycling for the LVS sample. The solvent used and the resulting crystal phase composition of the virgin sample is crucial for the copolymer behavior during bipolar electrical cycling.

Monte Carlo Analysis of Effect of Alloy Scattering on Electron Transport in Wurtzite Zn1-xMgxO

2013 ◽  
Vol 873 ◽  
pp. 861-864
Author(s):  
Lin Lin Hu ◽  
Ping Wang ◽  
Tao Shang ◽  
Jiu Xu Song
Keyword(s):  
Monte Carlo ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Drift Velocity ◽  
Monte Carlo Model ◽  
Monte Carlo Analysis ◽  
Alloy Scattering ◽  
Ensemble Monte Carlo ◽  
Velocity Decrease

Steady-state and transient electron characteristics of wurtzite Zn1xMgxO are studied in detail. An ensemble Monte Carlo model is established considering alloy scattering. From the steady-state characteristics, it is found that alloy scattering makes the drift velocity decrease at different electric fields. For 10% Mg, the transient peak drift velocity decreases from 2.48×107cm/s to 2.13×107cm/s at 2000 kV/cm. While for 20% Mg, a higher electric field is needed for the onset of the overshoot, which corresponds to the larger peak electric field in the steady-state velocity-field characteristics.

Properties of Space Charge Distributions and Conduction Current in XLPE and LDPE under DC High Electric Field

2015 ◽  
Vol 135 (2) ◽  
pp. 75-81 ◽  
Author(s):  
Tsuyoshi Kato ◽  
Ryo Onozawa ◽  
Hiroaki Miyake ◽  
Yasuhiro Tanaka ◽  
Tatsuo Takada
Keyword(s):  
Electric Field ◽  
Space Charge ◽  
High Electric Field ◽  
Conduction Current ◽  
Charge Distributions

scholarly journals Cell Fragmentation and Permeabilization by a 1 ns Pulse Driven Triple-Point Electrode

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Enbo Yang ◽  
Joy Li ◽  
Michael Cho ◽  
Shu Xiao
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Triple Point ◽  
Tungsten Wire ◽  
Low Voltage ◽  
Pulsed Electric Fields ◽  
High Electric Field ◽  
Bubble Collapse ◽  
Principal Mechanism ◽  
Point Electrode

Ultrashort electric pulses (ns-ps) are useful in gaining understanding as to how pulsed electric fields act upon biological cells, but the electric field intensity to induce biological responses is typically higher than longer pulses and therefore a high voltage ultrashort pulse generator is required. To deliver 1 ns pulses with sufficient electric field but at a relatively low voltage, we used a glass-encapsulated tungsten wire triple-point electrode (TPE) at the interface among glass, tungsten wire, and water when it is immersed in water. A high electric field (2 MV/cm) can be created when pulses are applied. However, such a high electric field was found to cause bubble emission and temperature rise in the water near the electrode. They can be attributed to Joule heating near the electrode. Adherent cells on a cover slip treated by the combination of these stimuli showed two major effects: (1) cells in a crater (<100 μm from electrode) were fragmented and the debris was blown away. The principal mechanism for the damage is presumed to be shear forces due to bubble collapse; and (2) cells in the periphery of the crater were permeabilized, which was due to the combination of bubble movement and microstreaming as well as pulsed electric fields. These results show that ultrashort electric fields assisted by microbubbles can cause significant cell response and therefore a triple-point electrode is a useful ablation tool for applications that require submillimeter precision.

Formaldehyde diffusion within crystalline and amorphous cellulose at different temperatures and electric fields: A molecular dynamics study

2017 ◽  
Vol 28 (2) ◽  
pp. 175-185 ◽  
Author(s):  
Bo Xu ◽  
Zhenqian Chen
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Molecular Dynamics Simulation ◽  
Electric Field ◽  
Electric Fields ◽  
Amorphous Region ◽  
Dynamics Simulation ◽  
Amorphous Cellulose ◽  
Different Temperatures ◽  
The Relationship

To provide a microcosmic theoretical support for the reduction of formaldehyde in building material, the diffusion process was investigated by molecular dynamics simulation. In addition, the diffusion model of formaldehyde molecules in crystalline and amorphous cellulose was built, and diffusion coefficients at different temperatures and electric fields were studied. The simulation temperature was from 293 to 393 K and electric field was from 0 to 400 kV/m. Diffusion coefficient increased with greater temperature and electric field both in crystalline and amorphous region. However, the diffusion coefficient in amorphous region could be ignored for it was two orders of magnitude lower than diffusion coefficient in crystalline region. The relationship between diffusion coefficient and temperature, and the relationship between diffusion coefficient and electric field were obtained by simulation, verified by the experiment. Temperature was shown to have a significant contribution to formaldehyde diffusion than electric field. Compared with experimental studies, the molecular dynamics simulation could only analyse the diffusion coefficient qualitatively because of the difference between micro-scale and macro-scale.

scholarly journals Ionization and Attachment Coefficients in C4F7N Gas Measured by the Steady-State Townsend Method

2019 ◽  
Vol 9 (18) ◽  
pp. 3686 ◽  
Author(s):  
Zhaoyu Qin ◽  
Yunxiang Long ◽  
Zhenyu Shen ◽  
Cheng Chen ◽  
Liping Guo ◽  
...  
Keyword(s):  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Room Temperature ◽  
Ionization Coefficient ◽  
Ionization Coefficients ◽  
Insulation Performance ◽  
Attachment Coefficient ◽  
Good Agreement ◽  
Effective Ionization

The normalized Townsend first ionization coefficient α/N and normalized attachment coefficient η/N in pure C4F7N were measured by using the steady-state Townsend (SST) method for a range of reduced electric fields E/N from 750 to 1150 Td at room temperature (20 °C). Meanwhile, the effective ionization coefficients are obtained. All SST experimental results show good agreement with pulsed Townsend (PT) experiment results. Comparisons of the critical electric fields of C4F7N with SF6 and other alternative gases such as c-C4F8 and CF3I indicate that C4F7N has a better insulation performance with a much higher normalized critical electric field at 959.19 Td.

Transient kinetics of formation of anodic oxide films on tantalum in dilute sulphuric acid

1961 ◽  
Vol 263 (1314) ◽  
pp. 395-406 ◽  
Keyword(s):  
Activation Energy ◽  
Steady State ◽  
Electric Field ◽  
Ionic Current ◽  
High Electric Field ◽  
Experimental Result ◽  
Cascade Process ◽  
Initial State ◽  
Frenkel Defects ◽  
Mobile Ions

When a high electric field is suddenly applied to a film in which the concentration of Frenkel defects is initially much lower than would be set up at this field in the steady state, the ionic current (which is supposed to be proportional to the concentration of Frenkel defects) builds up slowly at first and then more rapidly (approximately as d i /d t = ki 2 , where k increases with the field) before stabilizing at the steady-state value. This is in contradiction with the theory that Frenkel defects are produced directly by the high electric field which assists the movement of ions from lattice sites into interstitial sites. According to this theory, d i /d t should be greatest at t = 0. The experimental result suggests that mobile ions are produced by a cascade process in which moving ions eject ions from lattice sites into interstitial sites. Experiments in which the electric field in the oxide film is suddenly changed and the ionic current is measured before the concentration of mobile ions has time to change are expected to give f ' 2 ( E ), where the ionic current is determined (for a given concentration of ions) by a Boltzmann factor with activation energy W 2 reduced by the field by an amount f 2 ( E ). The results were consistent with f 2 ( E ) = q ( α 2 E — β 2 E 2 ) where q = charge on ion, α 2 = 2.23 Å and β 2 = 0.106 Å/10 6 V cm -1 . Experiments in which fields were suddenly applied at different temperatures to films in the same initial state gave an estimate of the activation energy for ionic mobility W 2 as 1.28 ± 0.1eV.

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