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Dielectric Barrier (dielectric + barrier)
Selected AbstractsRecent Progress in Dielectric Barrier Discharges for Aerodynamic Flow ControlCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2007G. I. Font Abstract Plasma actuators are electrical devices that use an atmospheric pressure dielectric barrier discharge for flow control. They have been employed successfully to promote boundary layer attachment. Simulations have been carried out of a plasma actuator using Direct-Simulation-Monte-Carlo and Particle-in-Cell methods. This work summarizes some recent results including: 1) the method by which force is imparted by the actuator to the neutral flow, 2) the effect of electronegative gasses, such as oxygen, and 3) the effects on the neutral flow of the plasma force. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Rotational and Vibrational Temperature Measurements in a High-Pressure Cylindrical Dielectric Barrier Discharge (C-DBD)CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005N. Masoud Abstract The rotational (TR) and vibrational (Tv) temperatures of N2 molecules were measured in a high-pressure cylindrical dielectric barrier discharge (C-DBD) source in Ne with trace amounts (0.02 %) of N2 and dry air excited by radio-frequency (rf) power. Both TR and Tv of the N2 molecules in the C 3,u state were determined from an emission spectroscopic analysis the 2nd positive system (C 3,u , B3,g). Gas temperatures were inferred from the measured rotational temperatures. As a function of pressure, the rotational temperature is essentially constant at about 360 K in the range from 200 Torr to 600 Torr (at 30W rf power) and increases slightly with increasing rf power at constant pressure. As one would expect, vibrational temperature measurements revealed significantly higher temperatures. The vibrational temperature decreases with pressure from 3030 K at 200 Torr to 2270 K at 600 Torr (at 30 W rf power). As a function of rf power, the vibrational temperature increases from 2520 K at 20 W to 2940 K at 60 W (at 400 Torr). Both TR and Tv also show a dependence on the excitation frequency at the two frequencies that we studied, 400 kHz and 13.56 MHz. Adding trace amounts of air instead of N2 to the Ne in the discharge resulted in higher TR and Tv values and in a different pressure dependence of the rotational and vibrational temperatures. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Silver-Loaded Cotton/Polyester Fabric Modified by Dielectric Barrier Discharge TreatmentPLASMA PROCESSES AND POLYMERS, Issue 1 2009Mirjana Kosti Abstract The preparation of antimicrobial silver-loaded cotton/polyester fabrics has been carried out by DBD surface activation followed by silver sorption from aqueous silver nitrate solution. A series of DBD fabric treatments was performed in order to determine the most suitable experimental conditions for the fabric surface activation. The capillarity, silver ion uptake, and copper number were used to assess the surface changes on the fabrics. An effective process has been developed to obtain antimicrobial silver-loaded Co/PES fabrics. The antimicrobial activity of the silver-loaded fabrics against different pathogens was evaluated in vitro. The quantity of bonded silver ions is enough to develop desirable antimicrobial activity in the Co/PES fabrics. [source] Atmospheric Cold Plasmas for Synthesizing Nanocrystalline Anatase TiO2 using Dielectric Barrier DischargesPLASMA PROCESSES AND POLYMERS, Issue 5 2007Long-Hui Nie Abstract Nanocrystalline anatase TiO2 has been successfully synthesized using TiCl4 and O2 as precursors by atmospheric cold plasmas generated by dielectric barrier discharges (DBD) without extra heating or thermal treatment. For the TiO2 powders synthesized by DBD plasma at an energy density of 5.9 kJ,·,L,1, XRD and TEM analyses revealed that the nanocrystallite size is about 10,15 nm. Only a single crystalline structure of anatase was observed performing XRD, HRTEM and SAED measurements. It was found that the particle size decreased with increasing the discharge power, and that the chlorine contamination dramatically decreased when using high discharge power levels. [source] Recent Progress in Dielectric Barrier Discharges for Aerodynamic Flow ControlCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-2 2007G. I. Font Abstract Plasma actuators are electrical devices that use an atmospheric pressure dielectric barrier discharge for flow control. They have been employed successfully to promote boundary layer attachment. Simulations have been carried out of a plasma actuator using Direct-Simulation-Monte-Carlo and Particle-in-Cell methods. This work summarizes some recent results including: 1) the method by which force is imparted by the actuator to the neutral flow, 2) the effect of electronegative gasses, such as oxygen, and 3) the effects on the neutral flow of the plasma force. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Rotational and Vibrational Temperature Measurements in a High-Pressure Cylindrical Dielectric Barrier Discharge (C-DBD)CONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005N. Masoud Abstract The rotational (TR) and vibrational (Tv) temperatures of N2 molecules were measured in a high-pressure cylindrical dielectric barrier discharge (C-DBD) source in Ne with trace amounts (0.02 %) of N2 and dry air excited by radio-frequency (rf) power. Both TR and Tv of the N2 molecules in the C 3,u state were determined from an emission spectroscopic analysis the 2nd positive system (C 3,u , B3,g). Gas temperatures were inferred from the measured rotational temperatures. As a function of pressure, the rotational temperature is essentially constant at about 360 K in the range from 200 Torr to 600 Torr (at 30W rf power) and increases slightly with increasing rf power at constant pressure. As one would expect, vibrational temperature measurements revealed significantly higher temperatures. The vibrational temperature decreases with pressure from 3030 K at 200 Torr to 2270 K at 600 Torr (at 30 W rf power). As a function of rf power, the vibrational temperature increases from 2520 K at 20 W to 2940 K at 60 W (at 400 Torr). Both TR and Tv also show a dependence on the excitation frequency at the two frequencies that we studied, 400 kHz and 13.56 MHz. Adding trace amounts of air instead of N2 to the Ne in the discharge resulted in higher TR and Tv values and in a different pressure dependence of the rotational and vibrational temperatures. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of relative gas humidity on the inactivation efficiency of a low temperature gas plasmaJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008P. Muranyi Abstract Aims:, To investigate the effect of relative gas humidity on the inactivation efficiency of a cascaded dielectric barrier discharge (CDBD) in air against Aspergillus niger and Bacillus subtilis spores on PET foils. Methods and Results:, The inactivation kinetics as a function of treatment time were determined using synthetic air with different relative humidity as the process gas. Spores of A. niger and B. subtilis respectively were evenly sprayed on PET foils for use as bioindicators. In the case of A. niger, increased spore mortality was found at a high relative gas humidity of 70% (approx. 2 log10). This effect was more evident at prolonged treatment times. In contrast, B. subtilis showed slightly poorer inactivation at high gas humidity. Conclusions:, Water molecules in the process gas significantly affect the inactivation efficiency of CDBD in air. Significance and Impact of the Study:, Modifying simple process parameters such as the relative gas humidity can be used to optimize plasma treatment to improve inactivation of resistant micro-organisms such as conidiospores of A. niger. [source] Development of ambient sampling chemi/chemical ion source with dielectric barrier dischargeJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2010Lee Chuin Chen Abstract The development of a new configuration of chemical ionization (CI)-based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub-ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high-voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non-volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non-proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. [source] Pulsed dielectric barrier discharge reactor for diesel particulate matter removalAICHE JOURNAL, Issue 8 2004S. Yao Abstract A dielectric barrier discharge (DBD) reactor, driven by a pulsed corona surface discharge (PCSD), was developed for the removal of particulate matter (PM) in an undiluted exhaust gas of a diesel engine. The DBD reactor consisted mainly of alumina (Al2O3) plates and metal meshes covered on the surfaces of Al2O3 plates. The PCSD was carried out with a pulse power supply at atmospheric pressure and the temperature of exhaust gases. The energy efficiency for PM removal was 26.5 ,g/J at maximum and 1 ,g/J with 42% PM removal. The construction of the DBD reactor that promoted PM deposition on Al2O3 surfaces improved energy efficiency. The constants in PM removal model were given. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1901,1907, 2004 [source] Diesel particulate matter and NOx removals using a pulsed corona surface dischargeAICHE JOURNAL, Issue 3 2004S. Yao Abstract A pulsed corona surface discharge (PCSD) system was established for particulate matter (PM) and NOx removals from a diesel engine. The PCSD was carried out with a dielectric barrier discharge (DBD) reactor and a pulse power supply at atmospheric pressure and room temperature. The DBD reactor consisted mainly of an alumina (Al2O3) tube and a stainless steel rod (cathode) inserted in the alumina tube, and an aluminum coil (anode) wound on the outside surface of the Al2O3 tube. Pulse voltage was applied to the outside Al coil and stainless steel rod. PM was removed at a rate of 89% at maximum with 40% NOx removal. Relations of pulse voltage and frequency to PM and NOx removals were investigated. PM was oxidized by NO2 and other kinds of active oxygen species, such as O and O3 from plasma discharges. A surface adsorption/desorption and PM oxidation model of PM removal was established. The kinetic equations and their constants were given. © 2004 American Institute of Chemical Engineers AIChE J, 50:715,721, 2004 [source] UV laser ablation and plasma treatment of wooden surfaces , a comparing investigationLASER PHYSICS LETTERS, Issue 8 2006N. Mertens Abstract Using UV short-wavelength laser irradiation, the layer of mechanically damaged cells on wooden surfaces can be removed. Four excimer lasers (157 nm, 193 nm, 248 nm, 308 nm) were used to compare the ablation of wooden surfaces by different UV wavelengths. The ablation depth was measured by using optical microscopy. LV-SEM was applied to determine the appearance and quality of the laser ablation. In addition to the ablation process the laser can be used also to influence the surface energy. As the same effect can be achieved by plasma treatment of wooden surfaces, both methods were compared. The comparison was made by means of the water droplet test. The plasma treatment was carried out at atmospheric pressure as a dielectric barrier discharge. Two types of wood were determined: beech and thermowood beech. Thermowood is a heat treated lumber product especially made for outdoor applications. It was examined, whether the thermal treatment of wood influences the characteristic changes of the laser ablation and the plasma treatment. With the researched wavelengths, homogeneous ablation is possible. The absorption time can be reduced both with laser ablation and plasma treatment, whereas plasma treatment causes a stronger effect. A combined treatment improves the effect additionally. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Functionalization of Copper Surfaces by Plasma Treatments to Improve Adhesion of Epoxy ResinsPLASMA PROCESSES AND POLYMERS, Issue S1 2009Juliano Nestor Borges Abstract Adhesion of epoxy resins on copper foils for printed circuit board (PCB) applications is improved by nearly a factor of 5, using surface cleaning and deposition of a 15-nm-thick film in a low-pressure remote plasma-enhanced chemical vapor deposition process. The cleaning pretreatment, using an N2,O2 oxidizing gas mixture with moderate heating (343 K), gives the best results. This pretreatment removes the carbonaceous contaminants present on the topmost surface of the sample and slightly oxidizes the copper into CuO. This oxide is then reduced during the deposition treatment, presumably by reaction with the aminopropyltrimethoxysilane (APTMS) precursor. The surface roughness is unchanged after treatment, thereby showing that the improvement of the copper/epoxy adhesion is only due to the chemistry of the plasma coating. Applying these results to dielectric barrier discharges allows us to achieve the same level of adhesion, which, therefore, does not depend on the process. [source] Atmospheric Pressure Plasma Deposition of Adhesion Promotion Layers on AluminiumPLASMA PROCESSES AND POLYMERS, Issue S1 2009Philipp Bringmann Abstract The paper presents investigations on the deposition of plasma polymerised films at atmospheric pressure as a pretreatment for painting and adhesive bonding of aircraft aluminium structures. Two different plasma jet sources are employed, one based on a controlled arc discharge and air as process gas, and another based on a dielectric barrier discharge (DBD) and He as plasma gas. The organosilicon precursors HMDSO, TEOS and OMCTS are used with both plasma sources. Deposition in the arc discharge plasma jet leads to almost carbon-free silica coatings, whereas coatings deposited with the DBD jet source contain a high amount of carbon, varying with precursor type. The obtained results of corrosion investigations and adhesion tests are promising, as some representative aircraft industry requirements could be achieved. However, the investigations show a strong dependency on the used precursor and type of polymer (paint or adhesive) applied on the plasma polymerised film. [source] Treatment of Carbon Tetrafluoride with Gas DischargesPLASMA PROCESSES AND POLYMERS, Issue 7-8 2007Gerhard J. Pietsch Abstract Waste gases from semiconductor industry contain perfluorocarbons, which cause global warming and therefore should be removed. There are several possibilities to do this, for example the treatment of the gas by thermal and non-thermal plasmas, as well as by heating. In model gases containing up to 10,000 ppm CF4, destruction removal efficiencies of nearly 100% have been reached at atmospheric pressure using dielectric barrier and arc discharges. In order to reach high values, the dissociation products of CF4 must be bonded by reaction partners such as SiO2, CaO or H2O. [source] Atmospheric Cold Plasmas for Synthesizing Nanocrystalline Anatase TiO2 using Dielectric Barrier DischargesPLASMA PROCESSES AND POLYMERS, Issue 5 2007Long-Hui Nie Abstract Nanocrystalline anatase TiO2 has been successfully synthesized using TiCl4 and O2 as precursors by atmospheric cold plasmas generated by dielectric barrier discharges (DBD) without extra heating or thermal treatment. For the TiO2 powders synthesized by DBD plasma at an energy density of 5.9 kJ,·,L,1, XRD and TEM analyses revealed that the nanocrystallite size is about 10,15 nm. Only a single crystalline structure of anatase was observed performing XRD, HRTEM and SAED measurements. It was found that the particle size decreased with increasing the discharge power, and that the chlorine contamination dramatically decreased when using high discharge power levels. [source] Atmospheric Pressure Plasma Treatment of Glass Fibre Composite for Adhesion ImprovementPLASMA PROCESSES AND POLYMERS, Issue S1 2007Yukihiro Kusano Abstract Glass-fibre-reinforced polyester composite plates were treated with an atmospheric pressure dielectric barrier discharge. Synthetic air was used as the treatment gas. The water contact angle dropped markedly from 84 to 22° after a 2-s treatment, and decreased to 0° when the composite plates were treated for more than 30 s. X-Ray photoelectron spectroscopic analysis showed that the contents of aluminium and oxygen on the surface increased with the plasma treatment. The adhesion strength of the 2-s treated surface was comparable to or higher than that achieved by conventional mechanical surface roughening. It decreased when the surfaces were treated for 5 and 15 s, but recovered for 30-s treatment. [source] Surface Modification of Al2O3 -Cr Ceramic by Non-isothermal N2 Plasma Treatment at Atmospheric PressurePLASMA PROCESSES AND POLYMERS, Issue S1 2007Andrzej R. Olszyna Abstract Al2O3/Cr composite ceramic was ion-nitrided in N2 under atmospheric pressure. The plasma was generated by two different systems: an ac high voltage corona discharge, and an ac high voltage concentric dielectric barrier discharge. An analysis of the plasma light emission revealed the presence of N ions (upto 50%) and confirmed the non-isothermal state of the plasma. The treated surface of the high melting sinter was smoothened when its components were nitrided so that Cr is transformed into Cr2N and Al2O3 is transformed into AlN. [source] Deposition of SiO, -Like Thin Films from a Mixture of HMDSO and Oxygen by Low Pressure and DBD Discharges to Improve the Corrosion Behaviour of SteelPLASMA PROCESSES AND POLYMERS, Issue S1 2007Camille Petit-Etienne Abstract Hexamethyldisiloxane was used to deposit silicon dioxide thin films using a low frequency plasma reactor at low pressure as well as a dielectric barrier discharge (DBD) at atmospheric pressure. FT-IR, XPS, EIS, SEM and ellipsometry were used to analyse the samples. The results show that, at low pressure, the deposited films which are smooth, continuous and dense present a polymer-like structure. By carrying out the film deposition after an oxygen plasma pretreatment step, a further improvement in the protective properties is achieved, which is observed in the case of SiO, coatings with 13.56 MHz RF generators.1 At atmospheric pressure, the deposited films present an inorganic character deposited in open air and a polymer-like one deposited under a controlled nitrogen atmosphere in our DBD reactor. The latter also allows continuous films which present the best anti-corrosive properties (which have been studied for the first time for anti-corrosive properties) when they contain some carbon incorporated. [source] Direct olive oil analysis by low-temperature plasma (LTP) ambient ionization mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2009Juan F. García-Reyes A fast, reagentless, and direct method is presented for the mass spectrometric analysis of olive oil without any sample pretreatment whatsoever. An ambient ionization technique, the low-temperature plasma (LTP) probe, based on dielectric barrier discharge, is used to detect both minor and trace components (free fatty acids, phenolics and volatiles) in raw untreated olive oil. The method allows the measurement of free fatty acids (the main quality control parameter used to grade olive oil according to quality classes), selected bioactive phenolic compounds, and volatiles. The advantages and limitations of the direct analysis of extremely complex mixtures by the ambient ionization/tandem mass spectrometry combination are discussed and illustrated. The data presage the possible large-scale application of direct mass spectrometric analysis methods in the characterization of olive oil and other foodstuffs. Copyright © 2009 John Wiley & Sons, Ltd. [source] DBD regeneration of GAC loaded with acid orange 7ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Guang-Zhou Qu Abstract Activated carbon (AC) has been widely used as adsorbent in various industrial applications, such as purification of water in sewage facilities and filtration of air in toxicity-treating factories. However, after exhaustion, AC should be regenerated and reused because of the limited resources for AC production and additional secondary pollution of spent-carbon dumped into water or soil. In this study, a process for regenerating AC based on high active species (O3, ·OH, HO2, O2, ·RO, etc.) generated by dielectric barrier discharge (DBD) oxidation was proposed. The regeneration of granular-activated carbon (GAC) exhausted with azo dye acid orange 7 was investigated to assay this method. The influences of the parameters, such as treatment time, electric field and gas kind, on the readsorption rate were studied systematically. The results of structural properties of GAC analyses showed that the surface area, the micropore area, external surface area, micropore volume and total volume of GAC after three cycles DBD treatment decreased to different extent. The adsorption isotherms indicated that the regeneration efficiency was about 81% after three times DBD plasma regeneration cycles, which confirmed the reuse feasibility of the regenerated GAC. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||