Dielectric Barrier Discharge Tube Research Articles

CO2 decomposition using the coaxial dielectric barrier discharge: effect of additive gas and double outer electrodes

This work has studied CO2 decomposition through the dielectric barrier discharge (DBD). The configuration of the DBD reactor was performed as a coaxial DBD tube. The dielectric barrier was made of a quartz tube with 1 mm thickness, while an outer electrode was made of a copper flat sheet wrapping around a quartz tube. The coaxial axis was made of stainless steel rod to be an inner electrode. The power source was applied by the alternative current (AC) high voltage with 7.8 kHz of frequency to both electrodes of the plasma reactor. The experiment was conducted on various conditions such as a mixed gas ratio, discharge gap, applied voltage, outer electrode length, two outer electrodes, and gas flow rate. The results showed that CO2 conversion was decreased when CO2 concentration increased. Similarly, the increase of gas flow rate also caused the decrease of CO2 conversion. Whilst the increase of an applied voltage causes the CO2 conversion clearly increased. Similarly, the CO2:Ar ratio of 60%:40% achieved 30% of CO2 conversion. Furthermore, the high percentage of CO2 conversion of 47.2% has been obtained from a 1.3 mm discharge gap with 40 ml/min of gas flow rate.

In situ preconcentration of lead by dielectric barrier discharge and its application to high sensitivity surface water analysis

A novel dielectric barrier discharge (DBD) reactor was utilized to in situ enrich and atomize lead in gas phase. The structure of DBD reactor was optimized to broaden the acidity window of plumbane generation from 1% to 3.5%, bringing better analytical stability and practicability deriving from hydride generation process. For the first time DBD proved effective in lead preconcentration and broadening the acidity window of plumbane generation. Pb can be trapped quantitatively (~100%) on the quartz surface of DBD tube under O2-containing atmosphere and released (~100%) under H2-containing atmosphere. The absolute detection limit (LOD) for Pb was 4.1 pg (injection volume = 1.2 mL), and the linear (R2 > 0.999) range was 0.05–100 μg/L. The results were in good agreement with those of certified reference materials (CRMs), and spiked recoveries for surface water samples were 99–104% with 2–8% RSD. By gas phase analyte enrichment, the proposed method reduced absolute LOD by 10 times. It was deduced that plumbane was changed to lead oxide species trapped on the quartz tube surface and then released, and transported in form of atoms to the detection zone.

High Sensitivity Analysis of Selenium by Ultraviolet Vapor Generation Combined with Microplasma Gas Phase Enrichment and the Mechanism Study.

Ultraviolet vapor generation (UVG), as an environmental/user-friendly and efficient sampling approach, was first combined with the gas phase enrichment of Se by dielectric barrier discharge (DBD) microplasma. Volatile Se species from UVG, being much more complicated than conventional hydrides, can be trapped quantitatively (∼100%) on the quartz surface of DBD tube under O2-containing atmosphere and released (∼100%) under H2-containing atmosphere. The absolute detection limit (LOD) for Se was 4 pg (injection volume = 1.2 mL), and the linear (R2 > 0.995) range was 0.05-50 μg/L. The results were in good agreement with those of certified reference materials (CRMs) of water and soil samples, and spiked recoveries for real samples were 90-102% with 1-10% relative standard deviations (RSDs). By gas phase analyte enrichment, the proposed method improved analytical sensitivity (peak height) by 16 times. The mechanism was deduced that dominating SeCO species besides H2Se generating from UVG were all trapped on the DBD quartz tube surface as SeO2 or selenite and then released/transported as atoms to the detection zone. The combination of UVG and DBD can facilitate the green uses, miniaturization, and portability revealing its promising potential in field elemental analysis.

A compact nanosecond pulse generator for DBD tube characterization.

High voltage pulses of very short duration and fast rise time are required for generating uniform and diffuse plasma under various operating conditions. Dielectric Barrier Discharge (DBD) has been generated by high voltage pulses of short duration and fast rise time to produce diffuse plasma in the discharge gap. The high voltage pulse power generators have been chosen according to the requirement for the DBD applications. In this paper, a compact solid-state unipolar pulse generator has been constructed for characterization of DBD plasma. This pulsar is designed to provide repetitive pulses of 315 ns pulse width, pulse amplitude up to 5 kV, and frequency variation up to 10 kHz. The amplitude of the output pulse depends on the dc input voltage. The output frequency has been varied by changing the trigger pulse frequency. The pulsar is capable of generating pulses of positive or negative polarity by changing the polarity of pulse transformer's secondary. Uniform and stable homogeneous dielectric barrier discharge plasma has been produced successfully in a xenon DBD tube at 400-mbar pressure using the developed high voltage pulse generator.

Acetic Acid Decomposition in a Coaxial Dielectric Barrier Discharge Tube with Mist Flow

Non-thermal plasmas can be used for water treatment system because they allow free radical generation without heating. Advanced oxidation processes using non-thermal plasmas have been developed to decompose persistent organic pollutants. In this study, a water treatment method that involves spraying a solution into a coaxial dielectric barrier discharge (DBD) tube using an air, argon or oxygen carrier gas was investigated. The alumina DBD tube had an inner high-voltage electrode and an outer ground electrode. Acetic acid was used as the decomposition target because acetic acid is a known persistent organic material. An acetic acid solution, diluted 10,000 times in purified water, was atomized by an ultrasonic atomizer unit and introduced into the DBD tube. The residence time of the droplets sprayed into the discharge area was almost 7 ms. Acetic acid was effectively decomposed and the decomposition ratio reached almost 80 % when Ar was employed as the carrier gas. This is due to the very fine droplets in the sprayed mist having a large specific surface area and OH radicals being able to react directly in solution. Furthermore, the results suggest that the chemical processes involved in acetic acid decomposition can be controlled by varying the carrier gas composition.

Ultraviolet-B radiation enhancement in dielectric barrier discharge based xenon chloride exciplex source by air

A single barrier dielectric barrier discharge tube of quartz with multi-strip Titanium-Gold (Ti-Au) coatings have been developed and utilized for ultraviolet-B (UV-B) radiation production peaking at wavelength 308 nm. The observed radiation at this wavelength has been examined for the mixtures of the Xenon together with chlorine and air admixtures. The gas mixture composition, chlorine gas content, total gas pressure, and air pressure dependency of the UV intensity, has been analyzed. It is found that the larger concentration of Cl2 deteriorates the performance of the developed source and around 2% Cl2 in this source produced optimum results. Furthermore, an addition of air in the xenon and chlorine working gas environment leads to achieve same intensity of UV-B light but at lower working gas pressure where significant amount of gas is air.

Analysis of Power in an Argon Filled Pulsed Dielectric Barrier Discharge

In this paper an argon filled coaxial dielectric barrier discharge (DBD) has been studied to understand the detail of power transfer from a unipolar square pulse to plasma during discharge. A dielectric barrier discharge based diffuse pulse discharge and its electrical characteristics are investigated. A quartz coaxial DBD tube filled at different pressures is used in the experiment. A unipolar pulse voltage of different peak voltages and frequencies has been applied to the discharge electrodes for the generation of microdischarges. Two current pulses are used for two consecutive discharges per applied voltage pulse. The second discharge, which occurs at the falling flank of the voltage pulse, is induced by the charges stored on the dielectric barrier during the first discharge. It has been deduced that the power supplied to ignite the first discharge is partly stored to ignite the second discharge when the applied voltage decays. This process ultimately leads to much improved power transfer to the plasma. The knowledge obtained from dynamic processes of the DBDs in the discharge gap explains quantitatively the mechanism of ignition, development and extinction of the DBDs.

Effects of Temperature and Flow Rates of Ozone Generator on the DBD by Varying Various Electrical Parameters

This study rationale a high voltage power supply which varies of (O-5) kV with the variable frequency of 50 Hz-5 kHz. The power supply is used in the dielectric barrier discharge tube for the ionization process to yield concentration of ozone.This setup points the development of small and high efficient ozone generators using corona discharge method. Ozone generation was carried out by varying parameters including voltage, frequency, flow rate and temperature to yield high concentration of ozone. The feeding gas composition greatly affected the ozone generation rate, which was increased in order of ambient air to dry air. With increase in temperature, ozone concentration is increased while ozone generation rate is enhanced. In the experiments, a maximum ozone concentration of approximately 83 ppm is obtained, the peak value of applied voltage of about 5kV and gap of electrode is 4.3mm respectively. Dry air is used as feeding gas with residence time of 10.58 sec.

プラズマチューブ内における微粒子の撹拌および搬送特性

The innovative technology is proposed for micro particle mixing and transportation in a plasma tube using electrostatic force coupled with plasma actuation on the inner surface of a tube. This Plasma tube (Dielectric Barrier Discharge tube) is composed of a pair of spiral electrodes both inside and outside of the tube for the generation of DBD. The fundamental characteristics of a plasma tube such as discharge characteristics and induced flow velocity were clarified experimentally. Furthermore, three dimensional electrical potential distribution as well as particle trajectory inside the plasma tube was shown by computational simulation.

Analysis of Discharge Parameters in Xenon-Filled Coaxial DBD Tube

In this paper, a xenon-filled coaxial dielectric barrier discharge (DBD) has been studied to understand the high-pressure nonequilibrium nonthermal plasma discharge. A quartz coaxial DBD tube (ID: 6 mm, OD: 12 mm) at 400-mbar xenon-filled pressure has been used in the experiment. A unipolar pulselike voltage up to a-6-kV peak working at 30 kHz has been applied to the discharge electrodes for the generation of microdischarges. A single discharge is observed per applied voltage pulse. Visual images of the discharge and electrical waveform confirm the diffused-type discharges. The knowledge obtained by dynamic processes of DBDs in the discharge gap explains quantitatively the mechanism that is obtained in the ignition, development, and extinction of DBDs. The behavior of different discharge parameters has also been analyzed. From the experimental results and equivalent electrical circuit, the dynamic nature of equivalent capacitance has been reported. The relative intensity analysis of the Xe peak in the optical emission spectra (172 nm) has also been carried out for different supplied powers, and it is found that the radiation power has increased with supplied power.

Development of double cylindrical dielectric barrier discharge ion source

This paper deals with the dielectric barrier discharge (DBD) ion source composed of the outer cylindrical dielectric tube and the inner grounded metallic tube electrode. The sample gas is supplied through the inner ceramic tube. In this ion source, the DBD plasma is localized in the DBD tube so that the sample gases can be ionized just outside of the ceramic tube by the DBD excited helium gas without being exposed in the plasma jet. Besides, ambient air does not take part in the ionization of the sample vapor because ionization takes place inside the DBD ion source. Thus, this method is totally free from contaminants in ambient air. It was found that this ion source is capable of soft, high-sensitivity, and reproducible ionization. Application of this technique to the analysis of methamphetamine, carbaryl and basil leaf was given.

Development of a Remote-from-Plasma Dielectric Barrier Discharge Ion Source and Its Application to Explosives

The design of a new type of dielectric barrier discharge (DBD) ion source for ambient ionization is described. In this ion source, the DBD plasma is confined in the DBD tube so that the sample gases can be ionized just outside of the discharge tube by DBD excited helium gas without being exposed to the plasma jet. The findings indicate that the ion source is capable of the soft and high-sensitive ionization of explosives.

Discharge characteristics of dielectric barrier discharge (DBD) based VUV/UV sources

Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using coaxial and planar geometry of DBD (gas gap: 1–3 mm) made of quartz with N2/Ar/Xe gas at different pressures. A proper ultra high vacuum system and gas filing system has been made for the processing & characterization of DBD tubes. A RF generator (20-100 kHz, 0-2.4 kV peak) is used for discharges in DBD tube. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. The discharge characteristics have been analyzed by V-I characteristics & Lissajous figure and found that the spatial discharge processes varies strongly according to the applied voltage waveform, pressure of filled gas and geometry of tube.

Gaseous Electrical Discharge-Induced Degradation of Organic Compound in Wastewater: UV Irradiation and Ozonation Effect

AbstractThis study investigated the degradation of an organic compound (an azo dye, Acid Red 4) in a synthetic wastewater by using dielectric barrier discharge (DBD) tube comprised of a hollow quartz cylinder and a coaxial copper rod. The DBD tube was immersed in the wastewater that was connected to the ground electrode. When AC high voltage was applied to the copper electrode, the electrical discharge occurred inside the quartz cylinder to produce ultraviolet (UV) light and reactive species such as ozone. The photocatalytic degradation of the organic compound with the UV emitted from the DBD tube was carried out in the presence of aluminum meshes coated with titanium oxide. The system further comprised a gas diffuser that distributed the ozone-containing gas produced in the DBD tube into the wastewater, such that the organic compound were degraded by reacting with ozone. The contributions of the photocatalysis and the ozonation to the degradation were separately assessed, and then combined effect on the degradation was examined. The results clearly revealed that the present system capable of degrading the organic compound in two ways (DBD-induced photocatalysis and ozonation) was very effective for the treatment of the wastewater.