Some experimental data on a gas discharge between a flowing electrolyte and a metal electrode

Experimental data on a gas discharge obtained for comparatively high currents (4–11 A), powers (5–15 kW), and current density at a liquid cathode (0.8–1.0 A/cm²) are presented. As the electrolyte, a solution of sodium salt in distilled water was used. The losses on the liquid cathode were significantly diminished by decreasing its electric resistance. Regimes in which the thermal efficiency of a discharge apparatus is equal to ∼80% have been determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 109–115, May–June, 2006.     

Some particularities of development of high frequency capacitive discharge between a drop-jet electrolytic electrode and a flow-type electolytic cell

Particular results of the development and burning of the high frequency capacitive discharge (HFCD) between a drop-jet electrolytic electrode and a flow-type electric cell are presented. Significant current and voltage pulsations taking place after the electric breakdown in the process of the HFCD burning confirm the multichannel shape of the discharge burning at atmospheric pressure. Three modes of HFCD burning between the combinations of the drop-jet electrolyte and the surface of the flow-type electrolyte have been specified. An HFCD with glowing luminescence and “streamer discharges” at the copper tube surface when the electrolyte jet is fed under the pressure of 3 × 10³ Pa has been discovered.     

Needle electrode erosion in water plasma discharge

Various active species are formed by a pulsed electrohydraulic discharge. Analyses of optical emission spectra, hydrogen peroxide production and erosion of needle electrodes in the pulsed discharge in water with a pulse energy of ≈ 10 mJ were investigated in dependence on the type of plasma discharge (unbridged and bridged), the electrode material (tungsten and stainless steel) and the electrical conductivity of the solution (500, 750, 1000 and 1250 μS/cm). It was found that the OH radical emission line intensity was strongly intensified in the case of unbridged discharge mode independently on the electrode material or on solution conductivity. Hydrogen peroxide production did not depend on the electrode material and was not correlated with OH radical emission line intensity. Lower erosion rate was measured for tungsten electrodes with further decrease in the case of unbridged discharge mode of operation. Stainless steel electrodes reveal opposite characteristics. Smooth crater-like morphology was found for stainless steel and finer surface structures with protrusions for the tungsten with a smaller average crater diameter, shorter protrusion size and distribution for unbridged discharge mode of operation.     

Some phenomena during electric discharge ignition in long tubes

Phenomena in slow nonlinear ionization waves are propagated under the action of changes in the electrode potential in discharge tubes. It is well known that the motion of such waves is accompanied by potential redistribution along the tube with a substantial role of charging its walls. The experimentally observed independence of the ionization wave velocity on the induction of the applied longitudinal magnetic field is discussed. In the case of the strong magnetization of electron motion, the radial current on walls is admittedly connected with the loss of axial symmetry in the ionization front. The cause of this may be the development of the ionization instability of discharges in crossed E, B fields. Evaluations of the average number of ionizations induced by one electron in the zone of the potential jump before its drift on the wall are given at the negative polarity of the ionization wave for helium in the pressure range of 33–840 Pa.     

Peculiarities of electric discharge between jet anode and metal cathode

We present the results of a DC electric discharge experimental study between a jet anode and copper cathode at atmospheric pressure. We found the essential influence of the jet anode flow nonuniform character on the discharge development for different power supply regimes. Discharge burning peculiarities are revealed in the jet regime at different power supply voltages with small fluctuation in the milli-, micro-, and nanosecond ranges of the time sweep. We also determined temperatures at the copper cathode surface and its atomization. By means of the Fourier transformation, we reveal the frequency spectrum of the discharge current oscillations.     

Formation of zinc oxide nanoparticles during electric discharge in water

A method for obtaining nanodimensional structures of zinc oxide (ZnO) by means of electric discharge in water is described. Data on the phase composition and luminescent properties of the synthesized ZnO powder deposited from a colloidal solution onto single crystal silicon surface are presented. It is shown that the partial concentrations of zinc in the oxide and metallic phases in the colloidal solution depend on the supply of oxygen to the zone of the chemical reaction. Optimum conditions for the discharge synthesis of nanodimensional powder with an almost 100% ZnO content have been found.     

Electrodynamics of a low-pressure electrode microwave discharge

Results are given of self-consistent two-dimensional simulation of self-sustained steady electrode microwave discharge in a chamber at the end of central conductor of a coaxial line. The discharge parameters are calculated in the diffusion mode in hydrogen at pressures of 0.5, 2, and 8 torr and incident power of 30–200 W. The dependence of matching between the discharge chamber and delivery path on the geometric dimensions of the chamber is investigated in the presence of plasma. It is demonstrated that the length of central electrode is the key factor affecting the structure of plasma formation and its matching with the pumping wave. The maxima and minima of matching alternate when the central electrode is elongated by quarter wave. The maxima and minima of matching for the case of low pressure (< 2 torr) are shifted by λ/4 relative to those for high pressure (> 2 torr). The problem of maximal energy input to the discharge region at the end of antenna-type electrode is analyzed. It is demonstrated that a restriction exists on the maximal energy input to such a discharge (and, accordingly, on the size of plasma formation). These restrictions are associated either with the runaway of discharge toward the generator or with the ignition of discharge in the region of entry of antenna into the chamber.     

Mass exchange between a solid sphere and a liquid in crossed electric and magnetic fields

The results of an experimental investigation of the effect of the magnitude and direction of the ponderomotive force [j×B] on the coefficient of mass transfer from an electrically nonconducting sphere to a liquid are described.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 31, No. 6, pp. 1013–1016, December, 1976.     

Prominent peculiarities of X-ray diffraction of solid helium

Since³He and⁴He atoms are the lightest stable mono-atoms with atomic number 2, they cause a variety of macroscopic quantum effects, including large zero point vibrations in liquid and solid phases. Some quantities relevant to X-ray diffraction of solid helium, i.e., the atomic-scattering factor, mass-absorption coefficient, the reciprocal of which is the characteristic length defined by absorption and the extinction distance etc., show either larger or smaller values by approximately two orders of magnitude compared with 3d transition metals. An incidental disappearance of Laue spots due to the downward X-ray diffraction of solid helium (2_B = 90°) could be explained by two factors. One is that the fraction of recoil-free emission is weakened by the great ratio of the huge recoil energy to the phonon energy through the zero-point energy in the Debye-Waller parameter. The other is that the great difference in the linear scatterer density in downward diffraction from that in forward diffraction results from the irradiation of a line-focus X-ray beam to take section topographs weakens the downward X-ray diffraction. The dislocation line of solid helium could not be observed with sharp contrast. Considering the two-orders higher magnitude of the extinction distances and the high dislocation density of more than 2.6· 10⁵cm^–2, dynamical X-ray diffraction seems to lose validity.     

Comparisons of discharge characteristics of a dielectric barrier discharge with different electrode structures

In order to analyze the homogeneous discharge of air dielectric barrier discharge (DBD) under ambient conditions, three different electrode structures are used in the paper. They are aluminum plane electrode, stainless mesh electrode and pure water electrode. The electrical characteristics are obtained and compared by using Lissajous figures, the waveforms of applied voltage and discharge current and the light emission images. The results show that the discharges of the different electrode structures are all filamentary discharges mode in ambient air and the discharge intensity of pure water electrode is much weaker than the other two electrodes.     

An electrode microwave discharge in a static field

The effect of an external static electric field on an electrode microwave discharge in nitrogen is investigated at pressures of 1 to 5 Torr and incident power of 20 to 170 W. It is demonstrated that the current-voltage characteristics (CVC) of the discharge with respect to direct current are nonlinear; the nonlinearity defining the CVC is the plasma layer at the surface of the discharge chamber. Qualitative agreement is obtained between the measured CVC and those calculated using the self-consistent one-dimensional quasi-static model of microwave discharge in a system of electrodes with spherical symmetry. It is demonstrated that the applied dc voltage affects only slightly the discharge characteristics; however, it enables one to control flows of charged particles to the surface of the discharge chamber.     

Some features of the hydrodynamic characteristics of a high-voltage electric discharge in a liquid with a two-pulse power deposition law

An analysis is made of the external hydrodynamic problem of an underwater electric discharge with a two-pulse power deposition law in the channel. As a result of an analytic solution of the problem, it is shown that the pressure function at the channel wall is a series of pulses of decaying amplitude, while the pressure function for a fixed point in the wave field is a series of increasing pulses. Pis’ma Zh. Tekh. Fiz. 23, 58–61 (May 12, 1997)     

Experimental investigations into electric discharge grinding and ultrasonic vibration-assisted electric discharge grinding of Inconel 601

The paper presents experimental investigations into electric discharge grinding (EDG) and ultrasonic vibration-assisted electric discharge grinding (UVAEDG) of Inconel 601. The process parameters selected for both processes were duty cycle, discharge current, pulse on time, grinding wheel speed, work speed, and speed ratio to study their influence on responses like surface roughness (R_a) and material removal rate (MRR). It was found that duty cycle, wheel speed, work speed, discharge current, speed ratio, and pulse duration significantly influenced MRR and R_a. It was inferred that MRR increased with increase in duty cycle, wheel speed, current, work speed, and pulse duration in both EDG and UVAEDG processes. It was also inferred that R_a increased with rise in duty factor, pulse on time, and discharge current in EDG and UVAEDG processes.     

Some peculiarities of the asymmetric Graetz problem

A numerical simulation and an analysis of the steady state forced convection heat transfer with plane laminar flow confined by two parallel plates that are kept at constant but different temperatures are presented. We name this heat transfer configuration shortly the asymmetric Graetz problem. The essential features of the asymmetric in comparison to the symmetric Graetz problem are the reversal of the heat flux and the jump of the Nusselt number from positive to negative region at the plate having the temperature closer to the fluid inlet temperature. These phenomena occur at different axial positions, which depend on the thermal asymmetry and the fluid inlet conditions. The numerical results agree excellently with an analytical solution obtained in terms of Kummer confluent hypergeometric function and Hermite polynomials.     

Effects of electrode materials on freezing of supercooled water in electric freeze control

In order to clarify effects of electric charge on freezing of supercooled water, experiments were carried out with various kinds of electrodes in supercooled water. Water sample was kept in a test tube and cooled down at a constant cooling rate. When the water sample was maintained under a supercooling state, an electric charge was applied to the water sample with a small electric current. The degree of supercooling was measured continuously. Then the degree of supercooling at freezing was determined. Six kinds of materials were used for electrodes. Those materials were Aluminum, Copper, Argentum, Aurum, Platinum and Carbon. It was found that the effects of electric charge were distinct according to the material used for electrodes. The degree of supercooling at freezing was the lowest in the case of Aluminum. On the other hand, the highest value of the degree of supercooling at freezing was obtained in the case of carbon. The reason for the difference in the degree of supercooling at freezing by six materials was discussed.     

液氮温区固-液复合绝缘气体小桥对沿面放电的影响

采用IEC脉冲电流法(IEC60270标准)对液氮温区超导复合绝缘沿面放电现象及其影响因素进行了研究。在六面屏蔽的局部放电实验室内,研究了不同放电条件对放电起始电压、放电量、击穿电压等的影响,进而研究了其作用机理,并用有限元方法开展了相关计算。实验数据表明,不同放电条件明显影响放电重复率、平均放电量、最大放电量等,放电产生的气泡越容易逸出,放电越严重;液氮的流动使放电起始电压有一定的升高,但对最终击穿电压影响不大;在放电通道上施加阻挡之后可明显提高最终的闪络击穿电压。     

Some peculiarities of heat exchange in porous media

Results are presented of investigations of the heat-exchange intensity in a porous material as a function of the coolant properties.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 4, pp. 588–591, April, 1971.     

Some peculiarities of fracture of nanocrystalline nitride and boride films

Fracture surfaces including those through indentations on different nanocrystalline boride/nitride films were investigated by FE-SEM, conventional SEM, and AFM. TiB₂, TiN, Ti(B,N), AlN, and (Ti,Al)N films have been obtained by non-reactive r.f. magnetron sputtering. Deformation was realized by cleavage fracture and under a Vickers indentor. Two types of film fracture connected with homogeneous and inhomogeneous deformation are described and discussed. The analogy between the inhomogeneous deformation films image and the river pattern in the case of conventional ceramics is also pointed out.