Pulse Peak Voltage Research Articles

Evaluating arc spray process parameters to synthesize highly spherical TiO 2 nanoparticles

This work characterizes the metal nanoparticle fabrication process using in situ nanoparticle measurement to obtain the desired geometric sphericity of nanoparticles. Without process characterization and control, the sphericity of prepared TiO 2 nanoparticles varied widely by up to 10% or more of the particle diameter. Therefore, an in situ particle sampling method was employed to collect on-line prepared particles and the particle contours were obtained by FE-SEM. They were analyzed using an image processing approach that had been developed to quantify the sphericity of TiO 2 nanoparticles. Experimental results indicate that the discharge energy parameters, including the operating temperature, vacuum pressure, pulsed peak voltage, pulsed peak current, the pulse on-time and the pulse off-time influence the particles’ sphericity. The improved process parameters enhance the average sphericity of the prepared TiO 2 particles by up to 40%.

Magnetically insulation of the ion diode used for high-intensity pulsed ion beam

The effect of magnetic field on the characteristics of high-intensity pulsed ion beam (HIPIB) is investigated on the magnetically insulated mode of external-magnetic field MID in a TEMP-6 type HIPIB apparatus. Without magnetic field, the perveance P ( P = I( t)/[ V( t)] 3/2) increases rapidly after the plasma production in the ion diode, indicating the short of the diode caused by the plasma fast moving in the diode. As the magnetic field increases from 1.1 B crit to 1.7 B crit , the perveance P increases slowly, and the diode current decreases with increasing ion current density, extracted ion current and production efficiency of ion beam due to the effectively suppressed plasma flow in the diode. The ion current density of 350 A/cm 2, diode current of 37 kA and the production efficiency of ion beam of about 30% are obtained with the magnetic field at 1.7 B crit . The perveance P increases more slowly with the magnetic field increasing to 2 B crit , and the ion current density falls to 190 A/cm 2 with the decreased diode current of 24 kA, and the decreased extracted ion current of 7 kA, whereas the production efficiency of ion beam is similar to that of 1.7 B crit caused by excessively inhibited flow of the plasma in the diode. The magnetic field of 1.7 B crit of the external-magnetic field MID in the TEMP-6 type HIPIB apparatus leads to the most efficient output of HIPIB with ion current density of about 350 A/cm 2, diode current of 37 kA, extracted ion current of 11 kA, and the production efficiency of ion beam of about 30% at a peak pulse voltage of 420 kV and an accelerating voltage of 350 kV with a pulse width of 70 ns (full width at half maximum) for surface modification of materials.

Temporal development and chemical efficiency of positive streamers in a large scale wire-plate reactor as a function of voltage waveform parameters

In this paper a large-scale pulsed corona system is described in which pulse parameters such as pulse rise-time, peak voltage, pulse width and energy per pulse can be varied. The chemical efficiency of the system is determined by measuring ozone production. The temporal and spatial development of the discharge streamers is recorded using an ICCD camera with a shortest exposure time of 5 ns. The camera can be triggered at any moment starting from the time the voltage pulse arrives on the reactor, with an accuracy of less than 1 ns. Measurements were performed on an industrial size wire-plate reactor. The influence of pulse parameters like pulse voltage, DC bias voltage, rise-time and pulse repetition rate on plasma generation was monitored. It was observed that for higher peak voltages, an increase could be seen in the primary streamer velocity, the growth of the primary streamer diameter, the light intensity and the number of streamers per unit length of corona wire. No significant separate influence of DC bias voltage level was observed as long as the total reactor voltage (pulse + DC bias) remained constant and the DC bias voltage remained below the DC corona onset. For those situations in which the plasma appearance changed (e.g. different streamer velocity, diameter, intensity), a change in ozone production was also observed. The best chemical yields were obtained for low voltage (55 kV), low energetic pulses (0.4 J/pulse): 60 g (kWh)−1. For high voltage (86 kV), high energetic pulses (2.3 J/pulse) the yield decreased to approximately 45 g (kWh)−1, still a high value for ozone production in ambient air (RH 42%). The pulse repetition rate has no influence on plasma generation and on chemical efficiency up to 400 pulses per second.

Optical Study of Radicals (OH, O, H, N) in a Needle-plate Negative Pulsed Streamer Corona Discharge

Optical emission spectroscopy has been applied to study the OH radicals and O, H, and N active atoms produced by a high-voltage negative pulsed streamer corona discharge of N2 and H2O mixture gas in a needle-plate reactor at one atmosphere. The relative vibrational populations and the vibrational temperature of N2(C, v′) were determined. The effects of pulsed peak voltage, pulsed repetition rate, and the addition of O2 on the relative populations of OH(A2Σ) radicals, O(3p5P), Hα (3P), and N(3p4P) active atoms were investigated. It was found that the relative populations of those radicals increase with increasing pulsed peak voltage and pulsed repetition rate. The relative population of OH(A2Σ) radicals decreases with increasing O2 flow rate, while the relative populations of O (3p5P), Hα (3P), and N (3p4P) active atoms exhibit a maximum over the studied range of the O2 flow rate. The involved physicochemical processes have also been discussed.

Optical study of radicals (OH, O, H, N) in a needle-plate bi-directional pulsed corona discharge

In this study, analysis of optical emission spectra are used for the detection of OH (A2Σ) radicals and O (3p5P), Hα (3P) and N (3p4P) active atoms produced by the high-voltage bi-directional pulsed corona discharge of N2 and H2O mixture gas in a needle-plate reactor at one atmosphere. The relative vibrational populations and the vibrational temperature of N2 (C, v') are determined. The effects of pulse peak voltage, pulse repetition rate and the added O2 flow rate on the relative populations of OH (A2Σ) radicals and O (3p5P), Hα (3P) and N (3p4P) active atoms are investigated. It is found that when pulse peak voltage and pulse repetition rate are increased, the relative populations of those excited states radicals rise correspondingly. The relative population of OH (A2Σ) radicals decreases with increasing the flow rate of oxygen. The relative populations of O (3p5P), Hα (3P) and N (3p4P) active atoms increase with the flow rate of oxygen at first and exhibit a maximum value at about 30 ml/min. When the flow rate of oxygen is increased further, the relative populations of those excited states active atoms decrease correspondingly. The main involved physicochemical processes also have been discussed.

Degradation of phenol in water using a gas–liquid phase pulsed discharge plasma reactor

In this paper, a gas–liquid phase pulsed discharge plasma reactor was used to dispose phenol in aqueous solutions. The effect of pulsed peak voltage and energy, solution conductivity, solution pH, and additive gas varieties on degradation efficiency of phenol was reviewed in the research. The observed results showed that degradation efficiency of phenol increased with the increase of pulsed peak voltage, discharge energy and treatment time. The degradation efficiency of phenol with the oxygen additive was higher than that with the argon additive. The degradation efficiency was higher in the basic solution.

Short-Pulse Discharge for Simultaneous Pursuit of Energy and Volume-Efficient NOx Removal

Concerning NOx removal (deNOx) by pulsed corona discharge, the methods of decreasing pulse width and peak voltage are effective in improving the energy efficiency. Since the latter has no technical barrier, the former should be more effective for practical application. In this study, an experimental comparison between the effects of these methods is presented. As a result, decreasing pulse width has an equal or greater effect than decreasing peak voltage on energy cost of deNOx. Therefore, it is possible to improve energy efficiency by decreasing pulse width while maintaining the processing amount per reactor volume by increasing peak voltage.

Decoloration of azo dye by a multi-needle-to-plate high-voltage pulsed corona discharge system in water

The decoloration efficiency of azo dye (Acid Orange 7, AO7) using a multi-needle-to-plate high-voltage pulsed corona discharge system was investigated in this paper. The effect of several parameters, including peak pulse voltage and pulse frequency of the discharge system, initial pH and electrical conductivity of the dye solution, mode of needle electrode distribution and gas flow rate on the decoloration rate of the dye wastewater was reviewed. The results obtained show that the pulsed discharge system with a multi-needle-to-plate electrode could dispose azo dye wastewater efficiently. The decoloration rate increased with an increase in applied peak pulse voltage and pulse frequency. Decoloration was more efficient in the acidic solution, and the decoloration rate displayed no marked change under solutions of differing electrical conductivity. For the case in which we example the effect of gas flow rate on the decoloration efficiency of Acid Orange solution, we found that better decoloration efficiency occurred using the seven-needle-to-plate discharge system, which had more discharge anodes.

Optical study of OH radical in a wire-plate pulsed corona discharge

In this study, the emission spectra of OH (A 2Σ → X 2Π, 0–0) emitted from the high-voltage pulsed corona discharge (HVPCD) of N 2 and H 2O mixture gas and humid air in a wire-plate reactor were successfully recorded against a severe electromagnetic interference coming from HVPCD at one atmosphere. The relative vibrational populations and the vibrational temperature of N 2 (C, v′) were determined. The emission spectra of the Δ v = + 1 (1–0, 2–1, 3–2, 4–3) vibration transition band of N 2 (C 3Π u → B 3Π g) is simulated through gauss distribution. The emission intensity of OH (A 2Σ → X 2Π, 0–0) has been exactly gotten by subtracting the emission intensity of the Δ v = + 1 vibration transition band of N 2 (C 3Π u → B 3Π g) from the overlapping spectra. The relative population of OH (A 2Σ) has been obtained by the emission intensity of OH (A 2Σ → X 2Π, 0–0) and Einstein's transition probability. The influences of pulsed peak voltage and pulse repetition rate on the relative population of OH (A 2Σ) radicals in N 2 and H 2O mixture gas and humid air are investigated separately. It is found that the relative population of OH (A 2Σ) rises linearly with increasing the applied peak voltage and the pulse repetition rate. When the oxygen is added in N 2 and H 2O mixture gas, the relative population of OH (A 2Σ) radicals decreases exponentially with increasing the added oxygen. The main involved physicochemical processes have also been discussed.

Comparison of unidirectional and bi-directional pulse driven corona discharge reactors for decomposition of hazardous gases

It is well known that both positive and negative pulse driven corona discharge reactors are effective in the decomposition of hazardous exhaust and flue gases. It is also reported in the literature that sinusoidal voltage driven reactors also have some advantages. The authors investigated earlier the effect of bi-directional pulses on corona reactors for freons. The action of bi-directional pulses is that fast rising pulses occur with the same pulse shape alternately both in the positive and negative directions. In this paper the comparison of these methods is made. The effects of the positive, negative and bi-directional pulses on a 120 cm long cylindrical reactor with the internal diameter of 6 cm were tested. The pulse peak voltage was varied between 10 and 35 kV in both directions. The width of the pulse was in the interval of 300–500 ns, the rise time was 35–50 ns. The gases investigated were nitrous oxide and sulphur dioxide. During the experiments, the voltage and the discharge current were measured, and the energy was calculated. In most cases, the result was that the positive sign pulse was the most effective, but the advantage of the negative pulse and the bi-directional pulse were also justified in some cases.

Pulse Voltage Trimming Method (PVTM) of Polymer Thick Film Resistors

In order to realise a non-cut trimming method without damage to the resistor surface of thick film resistors for electronic devices, a pulse voltage trimming method (PVTM) has been developed. This trimming method having resistance adjustments are due to pulse peak voltage and the number of pulse group. TCR and current noise of trimming resistor are considerably improved by this trimming technique and there is no loss in power handling capacity of the trimmed resistors. These advantageous features are observed by the increased number of conductive paths in the trimmed resistors. Further this method appears to be highly suitable for trimming of embedded resistors as the technique does not call for any heating or bombardment by an abrasive etc. and just involves the application of voltage between the terminals of resistor.

Experiment and Analysis on the Treatment of Gaseous Benzene Using Pulsed Corona Discharge Plasma

An experiment and analysis on removal of gaseous benzene by pulse corona induced-plasma is presented in this article. Important parameters effecting removal efficiency have been investigated, such as pulse peak voltage, pulse frequency, gas inlet concentration, gas flow rate and reactor temperature. The result shows that the removal efficiency increases with the increase in pulse peak voltage, pulse frequency and reactor temperature, but decreases in the rise of gas inlet concentration and gas flow rate. On the condition of Vp = 36 kV, f = 80 Hz, C = 1440 mg/m3 and Q = 640 ml/min, the largest removal efficiency is 98%. Finally, the reacted products are qualitatively analysed and the reaction processes are deduced in combination with plasma-chemistry theory.

Characterization and Optimization of Arc Spray Process Parameters for Synthesis of TiO<SUB>2</SUB> Nanoparticles

This article presents the process characterization and optimization of the nanoparticle fabrication process known as the Submerged Arc Spray Nanoparticle Synthesis System (SANSS) by using a developed on-line nanoparticle measurement system and Taguchi method. Without process characterization and optimization, preliminary experimental results indicated that the average secondary diameter of prepared nanoparticles, widely ranging from 45 to 350 nm, are significantly influenced by the process parameters, such as operating pressure, temperature, electrical current and type of dielectric liquids employed. To improve this, an on-line particle sizing system was developed and deployed to measure the particle dimension and analyze the nanoparticle synthesis process. Experiments based on Taguchi method were then conducted to investigate the optimum process parameters for producing nanoparticles with improved properties, such as particle size and uniformity. The experimental results revealed that the pulsed peak voltage and the pulsed peak current have the most significant effect on decreasing the secondary particle size of the TiO2 nanoparticles and that the on-time duration and off-time duration also play an important predominant effect. Using the optimized process parameters, the average secondary diameter of prepared TiO2 particles was reduced from 160 to 65 nm and the range of particle size disparity was narrowed from 300 to 170 nm. The primary particle size observed from TEM results also confirmed a significant reduction of the averaged TiO2 nanoparticle diameter and size disparity.

Electrical aging of molybdenum field emitters

As an approach to improve the stability and reliability of molybdenum field emitters with rough surfaces and impurities at tip apex, electrical aging was studied on the basis of the important tip heating mechanism, Nottingham heating, in dc and pulse mode. The effects of electric field in dc mode were investigated using single tips to avoid the averaging effect commonly arising in arrays. The fluctuations of emission currents were remarkably reduced after the exposure to high electric field (∼100 MV/cm). It was responsible for surface migration and impurity desorption at tip apex achieved under high electric field. Since the continuous exposure to high electric field can bring undesirable effects such as tip failures, electrical aging in pulse mode was also investigated. As the peak voltage of pulse was increased, the fluctuation of emission current was rapidly reduced. From the electrical aging experiments for a 0.7 in. field emission display (FED), it was proven that the poor uniformity of FED could be considerably improved by electrical aging.

Collection efficiency of ultrafine particles by an electrostatic precipitator under DC and pulse operating modes

High particle collection efficiency in terms of particle weight volume mg/m/sup 3/ is well achieved by a conventional electrostatic precipitator (ESP). However, the collection efficiencies in terms of number density for the ultrafine (particle size between 0.01 to 0.1 /spl mu/m) or submicron particles by a conventional ESP are still relatively low. Therefore, it is necessary to improve the collection efficiency for ultrafine particles. In this work, attempts have been made to improve the ultrafine particle collection efficiency using the short pulse energizations. The present version of ESP consists of three sets of wire plate type electrodes. For ESP under DC operation modes, experimental results show that the collection efficiency for DC applied voltage decreases with increasing dust loading when particle density is larger than 2.5/spl times/10/sup 10/ part/m/sup 3/. For ESP under pulse operating modes, the particle collection efficiency increases with increasing pulse peak voltage until 25 kV then decreases with increasing pulse peak voltage. The ultrafine particle collection efficiency based on particle density by DC energizations is much higher compared with pulse energizations without DC bias may be due to the reentrainments of ultrafine particles.

Simple voltage generator for producing well-defined nanosecond pulses of amplitudes in excess of 1 kV

A 50 /spl Omega/ charged coaxial line generator has been developed to produce extremely well-defined single-shot voltage pulses of amplitudes in excess of 1 kV, which are free from overshoot and ringing. The width of the pulses is adjustable from 0.7 ns to 250 ns with estimated rise-times as low as 105 ps. When driving a matched 50 /spl Omega/ load, the amplitude of the first reflected pulse replica is of less than 0.5% of the peak voltage of the main pulse.

A study on the decomposition of volatile organic compounds by pulse corona

In view of the application of gas cleaning technology by electrical discharge, the authors investigated the effect of characteristics of pulse corona on the gas decomposition. It was shown that pulse rise time, pulse peak voltage and pulse frequency greatly influence the decomposition of the gases. Pulse rise times less than about 100 nano sec, pulse peak voltages more than about 25 kV and pulse frequencies more than 60 pulse/sec are required for effective gas decompositions (nearly 100 % decomposition). Gas residence time more than about 2 min (flow rate less than about 0.4 cm/sec) is also necesarry for effective decomposition of the gases.

Narrow pulse formation using nonlinear LC ladder networks

Abstract Soliton propagation in a nonlinear lossy LC ladder network has been studied. We propose a quadratic polynomial expression to model the C-V characteristic of the nonlinear capacitor of the LC ladder network. This fits the experimental C-V data better over a wider range of the applied voltage, compared with the conventionally used formulae. Using this C-V expression, the Korteweg-de Vries (KdV) equation with a loss term has been obtained. This nonlinear equation has been solved by employing a novel technique that is based on Fourier series analysis. We have investigated the effects of bias voltage on the soliton pulse width and peak voltage and found a good agreement between the theoretical and experimental results.

Effects of initial polarity on defibrillation threshold with biphasic pulses.

Previous studies have shown that the polarity of epicardial patches significantly affects the defibrillation efficacy of monophasic shocks. However, whether this improvement can be extended to different pulsing methods and lead systems, such as biphasic shocks using endocardial defibrillating electrodes, is unknown. Twenty consecutive patients undergoing testing and permanent implant using an Endotak lead system with a biphasic device were included in the study. In each patient the defibrillation threshold was determined delivering biphasic pulses with the distal coil as the cathode and the proximal coil as the anode during the positive phase and with the polarity reversed. The initial electrode polarity tested was chosen randomly. The defibrillation threshold was defined as the lowest pulse amplitude that effectively terminated ventricular fibrillation induced with 60-Hz alternating current. For each biphasic pulse peak voltage, pulse duration, resistance, and stored energy were recorded. Of the 20 patients, 12 (60%) had lower defibrillation threshold when the proximal coil was negative, whereas only 2 patients had a lower defibrillation threshold when the distal coil was negative. In four patients a subcutaneous patch would have been required if only the biphasic pulse with the distal coil as negative had been tested. The mean stored defibrillation threshold energy was lower with the configuration using the proximal coil as cathode (16.3 +/- 8.8 J vs 21.5 +/- 11 J; P < 0.01). Change in the initial polarity of biphasic shocks may influence defibrillation efficacy and should, therefore, be assessed in each patient to achieve a more satisfactory safety margin and minimize the use of more invasive lead configurations.

New trimming technology of a thick film resistor by the pulse voltage method

To realize a noncut trimming method without any damage to the resistor surface of thick-film resistors for electronic devices, a pulse voltage trimming method (PVTM) has been developed for resistors of less than 0.5 mm/sup 2/. This trimming method combines coarse and fine adjustments which are, respectively, due to pulse peak voltage and the number of pulse groups. The PVTM ensures resistance accuracy with an error of less than 1%. High-frequency characteristics and current noise of the trimmed resistors are considerably improved by this trimming technique, and there is no loss in the power handling capability for the trimmed resistors. These advantageous features are obtained by the increased number of conductive paths in the trimmed resistors. >