| 1. |
- Bozhko, Igor, et al.
(author)
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Corona discharge to water surface and its transition to a spark
- 2011
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In: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 36:5, s. 1228-1233
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Journal article (peer-reviewed)abstract
- Impulse corona discharge in atmospheric air to the surface of a water layer with different electric conductivities isstudied. The discharge was initiated from a corona electrode consisting of a metallic disk with evenly distributed corona needles.The dependences of the magnitudes of the measured impulse currents on the polarity of the corona electrode as well as the parameters of the gas gap and liquid layer were obtained. An equivalent electric circuit of the discharge system was proposed,allowing for explanations of the regularities in the measured currents and also the role of the water layer as a factor affecting the transition of the corona discharge to a spark.
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| 2. |
- Bozhko, Igor, et al.
(author)
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Determination of Energy of a Pulsed Dielectric Barrier Discharge and Method for Increasing Its Efficiency
- 2017
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In: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 45:12, s. 3064-3069
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Journal article (peer-reviewed)abstract
- A methodology for accurate determination of energy released in a unipolar impulse dielectric barrier discharge is proposed and verified utilizing experimental data. In theexperiments, the discharge was initiated in air under atmospheric pressure in a coaxial chamber with glass dielectric barrier located on the cathode by applying voltage pulses with the slew rate of ∼3e11 V/s. It is shown that the energy released in the discharge is defined by the charge accumulated on the dielectric barrier before application of a successive voltage pulse and the magnitude of the remaining barrier voltage is dependent on many factors, in particular, repetition frequency of the discharge pulses, conditions and material of the barrier, impedance of the external electrical circuit, etc. It is demonstrated that the effective discharging of the barrier can be achieved by introducing a magnetic switch, which is essentially a nonlinear inductance connected in parallel to the discharge gap. The use of the switch allows for increasing the discharge efficiency in ∼30% and provides a way for correct evaluations of its energy.
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| 3. |
- Bozhko, Igor, et al.
(author)
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Modes of Impulse Barrier Discharge to Water Surface in Atmospheric Air
- 2020
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In: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 48:1, s. 156-162
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Journal article (peer-reviewed)abstract
- The possibilities of creating a homogeneous discharge in air of atmospheric pressure between a flat metallicelectrode covered by a dielectric barrier and water surface are demonstrated. In the experiments, the discharge was initiated in the gas gaps by applying unipolar voltage pulses with fronts of ∼15 ns and duration of ∼100 ns. It was found that the discharge mode was affected by the pulse repetition rate. Its critical magnitude corresponding to the appearance of a homogeneous discharge was reduced from 500 to 50 s−1 if the length of the air gap was increased from 1 to 4 mm. The lifetime of a homogeneous discharge mode was affected by the total duration of the discharge. Thus, it was about several tens of seconds at a pulse repetition frequency of 100 s−1 and it reduced at increased frequencies. It is suggested that the transition from homogeneous to inhomogeneous modes is associated with local overheating of the gas due to significant energy dissipation in the discharge volume.
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| 4. |
- Lubben, Olaf, et al.
(author)
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Self-assembly of Fe nanocluster arrays on templated surfaces
- 2012
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In: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 111:7
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Journal article (peer-reviewed)abstract
- The growth of Fe nanoclusters on the Ge(001) and MoO2/Mo(110) surfaces has been studied using low-temperature scanning tunneling microscopy (STM) and X-ray magnetic circular dichroism (XMCD). STM results indicate that at low coverage Fe atoms self-assemble on both surfaces into well-separated nanoclusters, which nucleate at equivalent surface sites. Their size, shape, and the observed spatial separation are dictated by the substrate and depend on preparation conditions. Annealing the Fe nanoclusters on Ge(001) at 420 K leads to the formation of linear nanocluster arrays, which follow the Ge dimer rows of the substrate, due to cluster mobility at such temperature. In turn, linear Fe nanocluster arrays are formed on the MoO2/Mo(110) surface at room temperature at a surface coverage greater than 0.5 monolayer. This is due to the more pronounced row pattern of the MoO2/Mo(110) surface compared to Ge(001). These nanocluster arrays follow the direction of the oxide rows of the strained MoO2/Mo(110) surface. The Fe nanoclusters formed on both surfaces show a superparamagnetic behavior as measured by XMCD. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676207]
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| 5. |
- Serdyuk, Yuriy, 1963, et al.
(author)
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Electrical breakdown in nonuniformly heated gases and the upper temperature limit of the applicability of Paschen’s law
- 2000
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In: High Temperature. - 1608-3156 .- 0018-151X. ; 38:3, s. 335-343
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Journal article (peer-reviewed)abstract
- The electrical breakdown of nonuniformly heated gas-discharge gaps with a uniform electric field at temperatures of 1200–3600 K is studied experimentally. It is found that the thermionic emission from the cathode has an effect on the breakdown parameters. This effect starts manifesting itself at the critical density of the emission currentJcr ∽ 10−8 A/cm2 attained in experiments with a tungsten cathode at a temperatureTCT ∼ 1700 K. The increase of the cathode temperature to -2200 K results in a decrease of the breakdown voltageUbr by more than an order of magnitude due to the thermionic emission. The heating of the anode to a temperature of up to 3600 K does not result in a decrease of the breakdown voltage below the values defined by the gas density. In this case, the decrease of the values ofUbr is due only to the change of the gas density distribution along the gap length and obeys the generalized law of similarity. The existence of a critical temperatureTT is predicted, above which one should expect a drastic decrease of the breakdown voltage due to the thermal ionization of gas. The value ofTT depends on the configuration of the thermal field between the electrodes and the type of gas. In the thermal fields typical of our experimental conditions involving the heating of one of the electrodes, the critical temperature for xenon is about 4700 K. The studies were carried out in argon, krypton, and xenon.
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| 6. |
- Walls, B., et al.
(author)
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Nanodomain structure of single crystalline nickel oxide
- 2021
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In: Scientific Reports. - : Nature Portfolio. - 2045-2322. ; 11:1
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Journal article (peer-reviewed)abstract
- In this work we present a comprehensive study of the domain structure of a nickel oxide single crystal grown by floating zone melting and suggest a correlation between point defects and the observed domain structure. The properties and structure of domains dictate the dynamics of resistive switching, water splitting and gas sensing, to name but a few. Investigating the correlation between point defects and domain structure can provide a deeper understanding of their formation and structure, which potentially allows one to tailor domain structure and the dynamics of the aforementioned applications. A range of inhomogeneities are observed by diffraction and microscopy techniques. X-ray and low-energy electron diffraction reveal domains on the submicron- and nanometer-scales, respectively. In turn, these domains are visualised by atomic force and scanning tunneling microscopy (STM), respectively. A comprehensive transmission electron microscopy (TEM) study reveals inhomogeneities ranging from domains of varying size, misorientation of domains, variation of the lattice constant and bending of lattice planes. X-ray photoelectron spectroscopy and electron energy-loss spectroscopy indicate the crystal is Ni deficient. Density functional theory calculations-considering the spatial and electronic disturbance induced by the favourable nickel vacancy-reveal a nanoscale distortion comparable to STM and TEM observations. The different inhomogeneities are understood in terms of the structural relaxation induced by ordering of nickel vacancies, which is predicted to be favourable.
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