Pulsed Electric Discharge Research Articles

Characterization of Si atomic transitions using pulsed electric discharge and resonance-enhanced multiphoton ionization techniques

A pulsed high-voltage electric discharge jet coupled with mass-selective REMPI was used to characterize Si atomic transitions with increased sensitivity.

Destruction of humic substances by pulsed electrical discharge

Currently, the water recourses in the territory of Tomsk region are groundwater which is limited to the high concentration of iron and manganese ions and organic substances. These impurities present in water in different forms such as soluble salts ant the colloid forms. Therefore, the present work is a part of a continuations researcher of the processes in natural waters containing humic substances at the influence of pulsed electrical discharges in a layer of iron pellets. It is shown that the main stage of water purification process of humic substances during treatment by pulsed electric discharge in the layer of iron granules is a difficult process including several stages such as formation of iron oxyhydroxide colloid particles, sorption and coagulation with humic macromolecules substances, growth of particle dispersed phase and precipitation. The reason for the formation and coagulation of the dispersed phase is a different state of charge of the colloid particles (zeta potentials of (Fe (OH)3) is +8 mV, zeta potentials of (Humic substances) is -70 mV. The most intense permanganate oxidation reduction to the maximum permissible concentration occurs at the processing time equal to 10 seconds. The contact time of active erosion products with sodium humate is established and it equals to 1 hour. The value of permanganate oxidation achieves maximum permissible concentration during this time and iron concentration in solution achieves maximum permissible concentration after filtration.

Generating of spatial formations composed of carbon atoms as fullerenes and nanotubes type by applying of pulsed electrical discharges to the formation of graphite films on metallic surfaces

The present paper presents the results of experimental researchings concerning the technology for obtaining the graphite films on metallic surfaces by applying the method of electric pulsed discharges (DEI). It was established that the efficiency for the graphite film obtaining is according with the conecting mode for the workpiece subjected to treatment of electric pulsed discharges to the polarity of the electric pulse generator. Thin pellicles obtained after the electric pulsed discharges treatment, contain mostly carbon, but after of detailed and special analysis (termogravimetric analyses, electronic microscopy SEM and chemical analyses), it was found that different chemical forms of carbon other of graphite are generated. They are spatial formations made of carbon atoms the type of fullerenes and carbon nanotubes. This occurance explains the special functional properties of graphite films and that is to encapsulate small molecules such as N 2 in the case of fullerenes, or organic molecules in case of nanotubes with single wall.

Development of Marx generator type pulsed power system with MOSFETs and underwater pulsed electric discharge

We have developed a ten stages Marx generator type pulsed power system with MOSFETs. The operation principle of the circuit has been clarified, and the experimental results have confirmed the operation of the developed circuit. In the case of ten stages system, the repetitive operation is verified at the frequency of 1 kHz, and the output voltage of 9.4 kV was obtained. The current was calculated as 36 A, and increasing of the current flowed in the system was achieved. The experiment of the underwater pulsed electrical discharge is performed, and the occurrence of the underwater pulsed electric discharge was confirmed.

Surface vitrification of alloys by pulsed electrical discharge treatment

Abstract Pulsed electrical discharge (PED) treatment was applied as a novel method to synthesize amorphous or amorphous/crystalline composite layers on the surfaces of Zr-, Fe-, Ti- and Al-based crystalline alloys. The formation of amorphous or amorphous/crystalline composite layers was investigated in terms of the significant disparity in glass-forming ability of the alloys. The influences of PED processing parameters on the surface glass formation of Zr 55 Al 10 Ni 5 Cu 30 alloy were further discussed and the PED-treated alloy exhibited a gradient structure: amorphous surface, amorphous/crystalline composite region and crystalline substrate from surface to inside. Besides, effects of processing parameters on the microhardness and corrosion behavior of the treated Zr 55 Al 10 Ni 5 Cu 30 alloy were investigated and the results revealed that the PED treatment could improve the microhardness and corrosion resistance of the crystalline substrate alloy. This PED treatment is a promising method to synthesize amorphous or amorphous/crystalline composite layers for novel mechanical, physical or chemical applications.

Niobium superconducting rf cavity fabrication by electrohydraulic forming

Superconducting rf (SRF) cavities are traditionally fabricated from superconducting material sheets or made of copper coated with superconducting material, followed by trim machining and electron-beam welding. An alternative technique to traditional shaping methods, such as deep-drawing and spinning, is electrohydraulic forming (EHF). In EHF, half-cells are obtained through ultrahigh-speed deformation of blank sheets, using shockwaves induced in water by a pulsed electrical discharge. With respect to traditional methods, such a highly dynamic process can yield interesting results in terms of effectiveness, repeatability, final shape precision, higher formability, and reduced springback. In this paper, the first results of EHF on high purity niobium are presented and discussed. The simulations performed in order to master the multiphysics phenomena of EHF and to adjust its process parameters are presented. The microstructures of niobium half-cells produced by EHF and by spinning have been compared in terms of damage created in the material during the forming operation. The damage was assessed through hardness measurements, residual resistivity ratio (RRR) measurements, and electron backscattered diffraction analyses. It was found that EHF does not worsen the damage of the material during forming and instead, some areas of the half-cell have shown lower damage compared to spinning. Moreover, EHF is particularly advantageous to reduce the forming time, preserve roughness, and to meet the final required shape accuracy.

Effect of Physicochemical Characteristics of Diamond Micropowders on the Effectiveness of Their Separation in Magnetic Field

The paper examines the effect of chemical and pulsed high-voltage electric discharge treatment of synthetic diamond micropowders on their mechanical and physicochemical properties, magnetic fraction composition, and separation characteristic, as well as effectiveness of their distribution in the magnetic field. It is shown that treatment with molten sodium hydroxide slightly decreases the specific surface area of the powder, and pulsed high-voltage electric discharge treatment increases its specific surface area and activates its energy state, improving the effectiveness of powder distribution in the magnetic field.

Cobalt Containing Polyimide Films Treated by Nanosecond Pulsed Electrical Discharges in Water

This paper describes the effect of nanosecond pulsed electrical discharges generated in distilled water on cobalt-modified fluorinated polyimide (PI) films derived from hexafluoroisopropylidendiphthalic dianhydride and 4,4’-diamino-3,3’-dimethyl diphenylmethane. The PI films have been characterized by dielectric spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction (XRD) measurements. The relative permittivity of the PI films increased after treatment by water plasma. The XRD analysis has shown a slight increase of the degree of intermolecular ordering and stronger $\pi $ – $\pi $ interactions with the increase of the plasma treatment time. Application of nanosecond high-voltage pulses has induced an increase in concentration of CF3 groups at the polymer surface. A decrease of the cobalt and chlorine fractions, due to their migration into water, and an increase of aliphatic C–C bonds at the film surface may be responsible for the relative permittivity modification after exposure to water plasma.

Application of Electro-Discharge Blasting Technology for Destruction of Oversized Rocks and Rock Massive Splitting off

The investigation of possibilities of the plasma blasting technology is considered. The method is based on the initiation of a pulsed electric discharge inside the solid dielectric material. The expanding plasma channel generates a shock wave which in the vicinity of the channel (1–2 mm) transforms into the elastic wave with an expressed region of tensile tangential stresses that in turn stimulate the radial crack nucleation. The efficiency of solid destruction at shock-wave action strongly depends on the pulse parameters. The high-current pulse must fulfil the requirements to such parameters: the high-rate of rising edge (0.1–10 ms) and pulse duration (≥ 200–300 ms). The experimental results have shown that the optimal ratio of the borehole depth is 0.6–0.7 from the oversize rock height. For splitting rock massive off the borehole depth should be at least 2 and not more than 5 electro-explosive cartridge lengths and distance between the boreholes should be equal to 1–2 of the boreholes depths. On the basis of the experimental results the recommendations for the electro-discharge destruction and splitting off oversized rocks are presented.

Detection and removal of impurities in nitric oxide generated from air by pulsed electrical discharge

Inhalation of nitric oxide (NO) produces selective pulmonary vasodilation without dilating the systemic circulation. However, the current NO/N2 cylinder delivery system is cumbersome and expensive. We developed a lightweight, portable, and economical device to generate NO from air by pulsed electrical discharge. The objective of this study was to investigate and optimize the purity and safety of NO generated by this device. By using low temperature streamer discharges in the plasma generator, we produced therapeutic levels of NO with very low levels of nitrogen dioxide (NO2) and ozone. Despite the low temperature, spark generation eroded the surface of the electrodes, contaminating the gas stream with metal particles. During prolonged NO generation there was gradual loss of the iridium high-voltage tip (−90 μg/day) and the platinum-nickel ground electrode (−55 μg/day). Metal particles released from the electrodes were trapped by a high-efficiency particulate air (HEPA) filter. Quadrupole mass spectroscopy measurements of effluent gas during plasma NO generation showed that a single HEPA filter removed all of the metal particles. Mice were exposed to breathing 50 parts per million of electrically generated NO in air for 28 days with only a scavenger and no HEPA filter; the mice did not develop pulmonary inflammation or structural changes and iridium and platinum particles were not detected in the lungs of these mice. In conclusion, an electric plasma generator produced therapeutic levels of NO from air; scavenging and filtration effectively eliminated metallic impurities from the effluent gas.

Pulsed electrical discharge in conductive solution

Electrical discharge in a conductive solution of isopropyl alcohol in tap water (330 S cm−1) has been studied experimentally applying high voltage millisecond pulses (rise time ∼0.4 , amplitude up to 15 kV, positive polarity) to a pin anode electrode. Dynamic current–voltage characteristics synchronized with high-speed images of the discharge were studied. The discharge was found to develop from high electric field region in the anode vicinity where initial conductive current with density ∼100 A cm−2 results in fast heating and massive nucleation of vapor bubbles. Discharges in nucleated bubbles then produce a highly conductive plasma region and facilitate overheating instability development with subsequent formation of a thermally ionized plasma channel. The measured plasma channel propagation speed was 3–15 m s−1. A proposed thermal model of plasma channel development explains the low observed plasma channel propagation speed.

Pulsed ultrasonic assisted electrical discharge machining for finishing operations

Electrical Discharge Machining (EDM) is a non-conventional machining process specially suitable for manufacturing hard-to-machine materials or geometrically complex parts. Many investigations have been presented combining EDM with ultrasonic (US) vibration of the electrode, but most of them have been intended to enhance the material removal rate of the process. In this paper US assisted EDM process has been used in order to improve the surface roughness in a finishing operation. For that purpose a copper rod tool electrode and a 1.2344 tempered alloy steel workpiece have been used. A pulsed US assisted EDM mode (PUEDM) has been developed and compared with the current EDM process and EDM assisted with continuous US vibration (UEDM). The results show that PUEDM process can improve the surface roughness and homogeneity of the machined surfaces in finishing EDM operations.

Investigating Characteristics of the Static Tri-Switches Tactile Probing Structure for Micro-Coordinate Measuring Machine (CMM)

This paper describes the fabrication of a series of micro ball-ended stylus tips by applying micro-EDM (Electrical Discharge Machining) and OPED (One Pulse Electrical Discharge) processes, followed by a manual assembly process of a static tri-switches tactile structure on a micro-CMM (Coordinate Measuring Machine). This paper further proves that the essential performance of the proposed system meets an acceptable benchmark among peer micro-CMM systems with a low cost. The system also adjusts for ambient temperature and humidity as the ordinary lab environmental conditions. For demonstration, several experiments used a randomly selected glass stylus with the diameters of stem and sphere of 0.07 mm and 0.12 mm, respectively. By leveraging research guidelines and common practice, this paper further investigates the probing relationship between measurement accuracy and its associated critical characteristics, namely triggering scenarios and geometric feature probing validation. The experimental results show that repeated detections in the uncertainty, in vertical and horizontal directions of the same point, achieved as small as 0.11 μm and 0.29 μm, respectively. This customized tri-switches tactile probing structure was also capable of measuring geometric features of micro-components, such as the inner profile and depth of a micro-hole. Finally, extensions of the proposed approach to pursue higher accuracy measurement are discussed.

Electron spectra of WO molecule. New electron state 3Π

The electron spectrum of the tungsten monooxide molecule is observed in the 550–800 nm region using intracavity laser absorption spectroscopy. The WO molecules are produced in a pulsed electric discharge through the mixture of tungsten hexacarbonyl vapors. The spectrum is recorded using a diffraction spectrometer (resolving power of 240000). The bands in the 16400–15500 cm–1 region are assigned to the 3Π0–X3Σ+ component of the 3Π0–X3Σ+–3XΣ+ electron transition. The rotational analysis of the 0-0 and 1-0 bands is carried out and the rotational constants for the ground X″3Σ and the exited 3Π0 states are computed: В′ = 0.385738 cm–1, B″ = 0.415538 cm–1.

An experimental and theoretical study of the Ã(2)A(″)Π-X̃(2)A(') band system of the jet-cooled HBBr/DBBr free radical.

The electronic spectra of the HBBr and DBBr free radicals have been studied in depth. These species were prepared in a pulsed electric discharge jet using a precursor mixture of BBr3 vapor and H2 or D2 in high pressure argon. Transitions to the electronic excited state of the jet-cooled radicals were probed with laser-induced fluorescence and the ground state energy levels were measured from the single vibronic level emission spectra. HBBr has an extensive band system in the red which involves a linear-bent transition between the two Renner-Teller components of what would be a (2)Π state at linearity. We have used high level ab initio theory to calculate potential energy surfaces for the bent (2)A' ground state and the linear Ã(2)A(″)Π excited state and we have determined the ro-vibronic energy levels variationally, including spin orbit effects. The correspondence between the computed and experimentally observed transition frequencies, upper state level symmetries, and H and B isotope shifts was used to make reliable assignments. We have shown that the ground state barriers to linearity, which range from 10 000 cm(-1) in HBF to 2700 cm(-1) in BH2, are inversely related to the energy of the first excited (2)Σ ((2)A') electronic state. This suggests that a vibronic coupling mechanism is responsible for the nonlinear equilibrium geometries of the ground states of the HBX free radicals.

Analysis of a gas-liquid film plasma reactor for organic compound oxidation

A pulsed electrical discharge plasma formed in a tubular reactor with flowing argon carrier gas and a liquid water film was analyzed using methylene blue as a liquid phase hydroxyl radical scavenger and simultaneous measurements of hydrogen peroxide formation. The effects of liquid flow rate, liquid conductivity, concentration of dye, and the addition of ferrous ion on dye decoloration and degradation were determined. Higher liquid flow rates and concentrations of dye resulted in less decoloration percentages and hydrogen peroxide formation due to initial liquid conductivity effects and lower residence times in the reactor. The highest decoloration energy yield of dye found in these studies was 5.2g/kWh when using the higher liquid flow rate and adding the catalyst. The non-homogeneous nature of the plasma discharge favors the production of hydrogen peroxide in the plasma-liquid interface over the chemical oxidation of the organic in the bulk liquid phase and post-plasma reactions with the Fenton catalyst lead to complete utilization of the plasma-formed hydrogen peroxide.

Influences of Pulsed Electric Fields on the Gene Expression of Pathogenic Bacteria

SUMMARYIn the biological and medical fields, sterilization using pulsed electric fields or discharges and electroporation have been studied actively in recent years. It is clear that a pulsed electric field has some sort of effect on an organism. At present, however, it is not sufficiently clear what effect occurs and how the mechanism of a pulsed electric field acts on the organism. The effects of pulsed electric fields on ribonucleic acid (RNA) expression in biological cells were studied with the objective of elucidating the bioelectric mechanism. A pulsed electric field was applied to Vibrio parahaemolyticus, a pathogenic bacteria, and the expression of RNAs, specifically thermostable direct hemolysin (TDH), VP1680, and VP1699, which represent pathogenic agents, were analyzed using the polymerase chain reaction (PCR) method. The level of expression of VP1680 increased when a pulsed electric field was applied, and the effect was at a peak when the electric field strength was 14 kV/cm. The electric field strength barely affected the expression of TDH and VP1699. It was found that the effects of the electric field were different among the RNAs. The expression level varied with time when expression was analyzed. These results suggest the possibility of selective control of gene expression by using pulsed electric fields and possible new applications such as the development of functional foods.

Pulsed electric discharge treatment of uranium leaching solutions: A method for accelerated extraction

Depletion of uranium ore deposits is leading to a need for more efficient uranium extraction techniques. In this study, gas-phase electric discharge is applied to an aqueous leaching solution dispersed between electrodes as a technique for enhancing acidic extraction of uranium. Application of the electric discharge treatment resulted in a 1.5 to 2.0 times increase in the leaching rate and an improvement in uranium recovery of 4%. The enhanced extraction method was found to involve oxidation of ferrous ions in the acidic aqueous solution by nitrogen-containing ions generated in the spark discharge channels.

Development of a web application for estimate the total charge in an electric discharge

This research seeks to implement a web application to estimate the total charge in an electric discharge from the experimental parameters established in reactors such as the JUPITER-MOSMET [1-5], used to perform surface modifications of metallic and nonmetallic species in solids substrates by hybrid discharges pulsed of high voltage and electric arc at low pressures [6-13]. Estimate the total charge generated in an electric discharge will allow to know the approximate value of the dose of ions implanted in the material surface [14-15], which are of great importance in each one of the experiments performed in the plasma laboratory of the Universidad Industrial de Santander (UIS), where the reactor is installed. Currently there are no applications developed to ease the process optimization and estimate the total charge generated in a pulsed electric discharge.

Removal of Iron Colloid Substances from Aqueous Solutions Using Pulsed Corona Discharge

Pulsed electric discharge has been used for the removal of iron colloid substances from aqueous solutions. The residual concentration of organic substances in aqueous solution depends on the pulse repetition rate. The maximum decrease in organic substances concentration was observed at the pulse repetition rate of 800 pps. Comparison of the results obtained for iron colloid solutions containing humic substances and solutions of humic subtances with no colloids shows that the highest removal efficiency of organic substances was obtained when no iron and silicon ions were present in the solution. The results of our experiments suggest that pulsed electric discharge treatment for the removal of organic substances from natural waters is more efficient at an after-treatment stage, after precipitation of colloid substances.