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Current Oscillations (current + oscillation)

Distribution by Scientific Domains

Physics and Astronomy	50%

Selected Abstracts

Spontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic Conditions

ADVANCED FUNCTIONAL MATERIALS, Issue 1 2010
Woo Lee
Abstract Nanoporous anodic aluminum oxide is prepared by hard anodization of aluminum under potentiostatic conditions using 0.3,M H2C2O4. Under unstirred electrolyte condition, spontaneous current oscillations are observed. The amplitude and period of these current oscillations are observed to increase with anodization time. As a consequence of the oscillatory behavior, the resulting anodic alumina exhibits modulated pore structures, in which the diameter contrast and the length of pore modulation increase with the amplitude and the period of current oscillations, respectively, and the current peak profile determines the internal geometry of oxide nanopores. The mechanism responsible for the oscillatory behavior is suggested to be a diffusion-controlled anodic oxidation of aluminum. [source]

Monte Carlo simulation of electrochemical oscillations in the electropolishing regime

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005
E. Foca
Abstract Current oscillations, and for the first time, voltage oscillations too, which occur at the Si electrode in a HF electrolyte in the electropolishing regime, are quantitatively calculated using Monte Carlo simulations based on the current burst model. Results obtained for relatively large areas comprise stable, unstable and damped oscillations, the formation of synchronized domains, and the influence of external voltage modulations, always in conjunction with all other parameters like oxide thickness and roughness behavior, or electrode capacitance. The results show good quantitative agreement in all respects with the experiments. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Spectroscopic Diagnostics of Pulsed arc Plasmas for Particle Generation

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2008
K. Behringer
Abstract Pulsed arc plasmas were diagnosed by means of emission spectroscopy. A capacitor was discharged through argon and hydrogen leading to a few cycles of damped current oscillation with ,120 ,s period and 5-12 kA maximum current. Spectroscopic measurements in the visible range were carried out in order to characterise the electron temperature and density in the arc channel as well as electron and gas temperatures in the afterglow plasmas. Spectra were integrated over 10 ,s time windows and shifted in time from pulse to pulse. The plasmas also contained substantial fractions of electrode material (brass), namely copper and zinc. The electron density was measured in the conventional way from the broadening of H, or from the Ar I Stark width. In the arc channel, it ranged from about 3 · 1022 to 2 · 1023 m,3. The broadening of Zn II lines could also be used. Ratios of Ar I to Ar II and of Zn I to Zn II line intensities were analysed for the electron temperature. Line pairs were found which lay conveniently close in one frame of the spectrometer allowing automatic on-line analysis without relying on reproducibility. Atomic physics models including opacity were developed for Ar II and Zn II in order to check the existence of a Boltzmann distribution of their excited states. These calculations showed that the observed levels were in fact close to thermodynamic equilibrium, in particular, if the resonance lines were optically thick. Electron temperature measurements yielded values between 14000 K and 21000 K. The gas temperature in the afterglow, where particles should have formed, was derived from the rotational and vibrational temperatures of C2 molecular bands. Ratios between Cu I line intensities yielded the electron temperatures. Both were found to be a few 1000 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Spontaneous Current Oscillations during Hard Anodization of Aluminum under Potentiostatic Conditions

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]

Stress induced one-dimensional model for current oscillations at the Si/electrolyte contact

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2009
Jürgen Grzanna
Abstract A cellular automata is introduced to model the locally resolved oxide thickness, the stress, and the etching rate dynamics at the silicon electrolyte contact along a macroscopically long line (1 mm). Short- and long-range interaction mechanisms are considered to achieve current oscillations. Extended chronoamperometric oscillations are obtained but finally, the oscillations become increasingly damped for the case of a locally acting stress and a locally varying etching rate. The additional incorporation of a small oscillating and long-range interacting nominal etching rate into the model leads to sustained oscillations. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A study of the relation between current oscillations and pitting

CHINESE JOURNAL OF CHEMISTRY, Issue 10 2003
Hou-Yi Ma
Abstract Anodic polarization behaviors of iron in pure H2SO4 and three mixed acidic solutions, H2SO4 + NaCl, H2SO4 + NaNO3 and H2SO4+ NaCl + NaNO3, were investigated. The potentiodynamic sweep curves showed that the current densities rose and dropped irregularly in H2SO4 + NaCl solution at the more anodic potentials since the iron surface suffered pitting attack in the solution, but the pitting corrosion was inhibited effectively in the presence of nitrate ions. The surface morphological measurements indicated that pits appeared on the iron surface in H2SO4 + NaCl solution and only a few unobvious corrosion spots were observed in H2SO4 + NaCl + NaNO3 solution after the iron electrode was potentiostatically polarized at 1.3 V. The oscillatory properties of iron are associated with the susceptibility of the iron to pitting. In H2SO4 + NaCl solution, the regular potentiostatic current oscillations gradually evolved into the irregular current fluctuations due to occurrence of the pitting; whereas in H2SO4 + NaCl + NaNO3 solution, the current oscillations took place regularly, like the oscillatory behavior in the pure H2SO4 solution. Thus, when the higher the oscillatory frequency, the more irregular oscillatory process and the more sensitive to pitting iron occurred. [source]