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DC Voltage (dc + voltage)

Distribution by Scientific Domains

Physics and Astronomy	42%
Engineering	28%

Selected Abstracts

Space Charge Measurement in MgO/LDPE Nanocomposite up to Breakdown under DC Ramp Voltage

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2010
Yoshinobu Murakami Member
Abstract To understand the basic electric properties of nanosized magnesium oxide (MgO)/low-density polyethylene (LDPE) nanocomposites under an applied DC voltage, the DC breakdown strength and space charge up to the breakdown under a DC ramp voltage were investigated. Compared to that of the LDPE sample, the sample containing a MgO nanofiller (hereafter, called a nanocomposite) had a higher DC breakdown strength. In the case of the LDPE sample, the homo charges, which contained a large negative charge and a small positive charge, were only observed near the electrodes just prior to breakdown. However, in the case of the nanocomposite sample, the positive charge increased as the average field increased until the average field reached a certain value. After that, the positive charge decreased as the average field increased until breakdown occurred. The field enhancement rate (=maximum field/average field) of the nanocomposite sample increased with the average field, until it became saturated. After peaking, the field enhancement rate of the nanocomposite sample decreased as the average field increased. These observations suggest that, instead of the MgO nanofiller suppressing the electronic avalanche, it suppresses the conduction current, which was determined by the space charge, leading to the higher DC breakdown strength. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Grafted 2D Assembly of Colloidal Metal Nanoparticles for Application as a Variable Capacitor,

ADVANCED MATERIALS, Issue 13 2007
N. Lidgi-Guigui
A combination of sputtering and colloidal chemistry is employed to prepare [Co/Al2O3//Ru nanoparticles//Al2O3/Co] junctions (see figure). These junctions are applied as variable capacitors relying on Coulomb blockades in a 2D assembly of nanoparticles. AC measurements show a significant capacitance variation as a function of applied DC voltage with a maximum of relative variation value that is proportional to the particle density embedded in the dielectric layer and is in good agreement with the theoretical model. [source]

In situ investigation of the non-linear optical crystal rubidium titanyl arsenate, RbTiOAsO4, under applied electric field using X-ray imaging

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2007
P. A. Thomas
Recent work on the non-linear optical single-crystal rubidium titanyl arsenate (RbTiOAsO4, RTA) has shown that it exhibits behaviour consistent with a ferroelectric semiconductor under large applied electric fields, with the development of a non-uniform field in the near-surface region. To confirm aspects of the proposed model, the behaviour of 001 slices of initially single-domain RTA, patterned with periodic Ag electrodes of spacing 38,µm, as for periodic poling in non-linear optics, were investigated using synchrotron X-ray section topography with the electric field applied in situ while under X-ray illumination at the ID19 topography beamline of the ESRF, Grenoble. The results of white-beam section topography as both a function of crystal to film distance, and under DC voltage are reported, confirming that there is a bending of the planes in the near-surface region. The strain in the near-surface region was examined directly using high-resolution monochromatic X-ray section topography. This revealed an extensive strain of 3,(±1) × 10,4 at 1,kV, indicating that the electrostrictive coefficient, ,3333, in RTA is positive in sign. [source]

Highly (001)-textured WS2,x films prepared by reactive radio frequency magnetron sputtering

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 14 2004
K. Ellmer
Abstract Highly (001)-oriented WS2,x films were grown onto oxidized silicon substrates by reactive magnetron sputtering from a metallic tungsten target in argon-hydrogen sulfide mixtures. The best films with respect to the van-der-Waals orientation, i.e. with the (001) planes parallel to the substrate surface, were grown by excitation of the plasma with radio frequency of 27.12 MHz. These films exhibit the largest grains and the lowest film strain. It is shown that this effect is not due to the lower deposition rate at this high excitation frequency. Instead it was found that the lower DC voltage at the sputtering target is advantageous for the film growth since the bombardment of the growing film by highly energetic particles is avoided by this type of plasma excitation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Laser-assisted electron emission from CVD nano-graphite films

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 13 2006
D. A. Lyashenko
Abstract We demonstrate that irradiation with nano-second light pulses results in significant enhancement of the electron emission from nano-graphite films. The observed emission current density is as high as 10 A/cm2 at applied field of 2 V/µm. The duration of the emission pulse depends on the applied DC voltage and laser intensity. However, in our experimental conditions, the temporal profile of the electron pulse nearly reproduces that of the incident laser pulse. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Understanding the partial discharge activity of conducting particles in GIS under DC voltages using the UHF technique

EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2010
R. Sarathi
Abstract The major cause of failure of DC-GIS is due to presence of foreign particles causing partial discharges in the insulation structure. The particle movement in gas insulated system (GIS) radiates electromagnetic waves and the bandwidth of the signal lies in the range 1,2,GHz. Increase in applied DC voltage/pressure has not altered the frequency content of the ultra high frequency (UHF) signal generated due to partial discharge formed by particle movement. The UHF sensor could recognize the breakdown of sulfur-hexa-fluoride (SF6) gas under DC and Lightning impulse voltages and the frequency content of the signal captured by the UHF sensor lies up to 500,MHz. Mounting UHF sensor in GIS could allow one to classify internal partial discharges from breakdown, at the time of testing/during operation. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Self-sustained current oscillations in a multi-quantum-well spin polarized structure with normal contacts

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2008
R. Escobedo
Abstract Self-sustained current oscillations (SSCO) are found in a nonlinear electron spin dynamics model of a n-doped dc voltage biased semiconductor II,VI multi-quantum well structure (MQWS) having one or more of its wells doped with Mn. Provided one well is doped with magnetic impurities, spin polarized current can be obtained even if normal contacts have been attached to this nanostructure. Under certain conditions, the system exhibits static electric field domains and stationary current or moving domains and time-dependent oscillatory current. We have found SSCO for nanostructures with four or more QWs. The presence of SSCO depends on the spin-splitting induced by both, the exchange interaction and the external magnetic field. We also calculate the minimal doping density needed to have SSCO, and a bound above which SSCO disappear. This range is crucial to design a device behaving as a spin polarized current oscillator. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]