Barrier Discharge Type Research Articles

Dielectric Barrier Discharge for Solid Food Applications.

Atmospheric cold plasma (ACP) is a non-thermal technology whose ability to inactivate pathogenic microorganisms gives it great potential for use in the food industry as an alternative to traditional thermal methods. Multiple investigations have been reviewed in which the cold plasma is generated through a dielectric barrier discharge (DBD) type reactor, using the atmosphere of the food packaging as the working gas. The results are grouped into meats, fruits and vegetables, dairy and lastly cereals. Microbial decontamination is due to the action of the reactive species generated, which diffuse into the treated food. In some cases, the treatment has a negative impact on the quality. Before industrializing its use, alterations in colour, flavour and lipid oxidation, among others, must be reduced. Furthermore, scaling discharges up to larger regions without compromising the plasma homogeneity is still a significant difficulty. The combination of DBD with other non-thermal technologies (ultrasound, chemical compounds, magnetic field) improved both the safety and the quality of food products. DBD efficacy depends on both technological parameters (input power, gas composition and treatment time) and food intrinsic properties (surface roughness, moisture content and chemistry).

Investigation of the effect of cold atmospheric plasma on gliadins and glutenins extracted from wheat flour samples

Cold atmospheric plasma (CAP) is an emerging technique that has drawn noticeable interest from food scientists. The aim of this study was to examine the extent of CAP effects on wheat flour gliadin and glutenin proteins. Both wheat flour and previously prepared gliadin and glutenin extracts were subjected to CAP treatment. Surface dielectric barrier discharge (SDBD) type of CAP treatment was used for the treatment of wheat flour (4 min). Additionally, the SDBD treatment was also performed on previously prepared glutenin and gliadin extracts (1 min). Proteins were chromatographically separated and the total amount of proteins, the amount of proteins within the fractions, and their relative concentrations were determined. The treatment leads to a decrease in the total amount of proteins, compared to the untreated samples, which is indicative of the depolymerization of gluten proteins, thereby reducing the amounts of large-sized protein polymers, indicating they reduced immunoreactivity. Novelty impact statement Cold atmospheric plasma (CAP) has drawn noticeable interest as a novel non-thermal processing technology. Nevertheless, studies on the CAP potential to modify the immunoreactivity of wheat proteins are sparse. The molecular weight distribution of wheat protein polymers was altered after CAP treatment and the decrease in the amount of proteins was observed compared to the untreated samples. The results show that the amount of proteins within the fractions responsible for allergenicity decrease after CAP treatment, which indicates that the CAP technique can be used for reducing wheat proteins allergenicity.

Decomposition of indoor VOC pollutants using non-thermal plasma with gas recycling

Volatile organic compounds in the indoor environment of small businesses (painting workshops, hair salons, nail shops, printing shops, laundries etc.) may result in adverse health effects for both workers and customers. Similarly, VOCs identified in these small businesses are included in the list of ozone precursors that harm the environment. We used a non-thermal plasma reactor with gas recycling to study the decomposition of dilute concentrations of VOCs in air. The non-thermal plasma reactor was a surface dielectric barrier discharge (surface DBD) type, and the target gases were methyl ethyl ketone, toluene and n-hexane at concentrations of 20, 50 and 100 ppmv. Highest decomposition efficiency (97%) was achieved by treating n-hexane at 20 ppmv. Gas recycling had an almost negligible effect during pollutant treatment at varying recycling rates (0-50%). Increasing the input energy resulted in higher decomposition efficiency, but had an inverse effect on the energy yield of the system. Concentrations of CO2 and ozone increased linearly with the increase of energy input in the system. Consumption of ozone for other applications, such as water treatment or coupling the DBD system with an appropriate catalyst, may address this concern.

Photofragmentation laser-induced fluorescence of ozone: an in situ tool for precise mapping of ozone concentration in non-thermal plasmas

The absolute spatially resolved concentration of ozone has been determined in the near afterglow of a novel type of atmospheric multi-hollow barrier discharge using photofragmentation laser-induced fluorescence. The method consists of two steps: (i) photodissociation of O3 to O(3P) and O2(X3Σg−) with considerable vibrational excitation; (ii) predissociation laser-induced fluorescence of the molecular fragment via the O2 (B 3Σu−, v′ = 0 ← X 3Σg−, v″ = 6) transition. Both processes happen during the same laser pulse, requiring the same excitation wavelength (≈248 nm). The fluorescence signal has been calibrated by infrared absorption. The method allows in situ observation before the afterglow chemistry significantly affects the O3 concentration, and is capable of revealing inhomogeneous ozone distributions in the reactor.

A Convenient Method to Realize Large-Area APGD for Wool Surface Modification

In this paper, a method of realizing large-area atmospheric pressure glow discharge (APGD) plasma in ambient air was investigated. The dielectric barrier discharge (DBD) type was adopted, and the electrode arrangement of a tubular array was designed to achieve large-area APGD (about $1000 \times 60$ mm $^{2}$ ). Optical emission spectroscopy (OES) was used to identify active particles and calculate gas temperature. The results show that the seed electrons can react with N2, O2, and H2O in the air to produce N2 (C-B), N2+, OH, and O3. The gas temperature was calculated to be 410 K–514 K, which is suitable for low-added-value materials treatment. The homogeneity of the plasma temperature was also verified by an infrared camera. Furthermore, a prototype for the wool surface modification was also investigated. The scanning electron microscope (SEM) micrographs and wettability test were adopted, which shows that the plasma can damage the squamae of the natural wool to improve the wettability greatly without burning the wool fiber.

Influence of Cold Atmospheric Plasma on Acinetobacter baumannii


 baumannii is an aerobic gram negative coccobacilli, it is considered multidrug resistance pathogen (MDR) and causes several infections that are difficult to treat. This study is aims to employ physical methods in sterilization and inactivation of A. baumannii, as an alternative way to reduce the using of drugs and antibiotics.
 
 Cold Atmospheric Plasma was generated by one electrode at 20KV, 4 power supply and distance between electrode and sample was fixed on 1mm. A. baumannii (ATCC 19704 and HHR1) were exposed to Dielectric Barrier Discharge type of Cold Atmospheric Plasma (DBD-CAP) for several periods of time (15, 30, 45, and 60 sec.) . After sterilization test, several methods were done to analyze the effect of DBD-CAP on bacterial morphology, proteins and DNA. Change in morphology was assessed by cover slid method. Damaged DNA was investigated by PCR technique, and DNA sequencing. The impact of DBD-CAP on the entity of proteins was detected by SDS-PAGE. The observed inactivation of bacterial colony on agar plates has been quantified by measuring the inactivation diameter.
 The important conclusion that HHR1 more resistance to DBD-CAP than ATCC 17904 because it is more virulence than standard strain; thus, the growth of both strains is largely affected by plasma and this influence is increased by increasing the time of exposure, also the plasma affects the DNA especially on standard strain as it is explained in sequencing result, so it causes more deletion in DNA sequence. In addition, plasma also has been showed to damage proteins and morphology thus, the bacterial cells transform from cocco-bacillus to bacillus.

Influence of Cold Atmospheric Plasma on Acinetobacter baumannii


 baumannii is an aerobic gram negative coccobacilli, it is considered multidrug resistance pathogen (MDR) and causes several infections that are difficult to treat. This study is aims to employ physical methods in sterilization and inactivation of A. baumannii, as an alternative way to reduce the using of drugs and antibiotics.
 
 Cold Atmospheric Plasma was generated by one electrode at 20KV, 4 power supply and distance between electrode and sample was fixed on 1mm. A. baumannii (ATCC 19704 and HHR1) were exposed to Dielectric Barrier Discharge type of Cold Atmospheric Plasma (DBD-CAP) for several periods of time (15, 30, 45, and 60 sec.) . After sterilization test, several methods were done to analyze the effect of DBD-CAP on bacterial morphology, proteins and DNA. Change in morphology was assessed by cover slid method. Damaged DNA was investigated by PCR technique, and DNA sequencing. The impact of DBD-CAP on the entity of proteins was detected by SDS-PAGE. The observed inactivation of bacterial colony on agar plates has been quantified by measuring the inactivation diameter.
 The important conclusion that HHR1 more resistance to DBD-CAP than ATCC 17904 because it is more virulence than standard strain; thus, the growth of both strains is largely affected by plasma and this influence is increased by increasing the time of exposure, also the plasma affects the DNA especially on standard strain as it is explained in sequencing result, so it causes more deletion in DNA sequence. In addition, plasma also has been showed to damage proteins and morphology thus, the bacterial cells transform from cocco-bacillus to bacillus.

A Wide-Range Frequency Model for Dielectric Barrier Discharge Type Ozone Generators Powered by Series Resonant Inverters

Dielectric Barrier Discharge (DBD) type ozone generators (OGs) are widely used for industrial ozone generation. As OGs are typical non-linear load, different models are presented to analyze the characteristic of OGs and the models of OGs have proven to be an effective tool to design power supplies for OGs. However, most of the models are only applicable to nominal conditions and not suitable for a wide working range at present. Considering that almost all of the series resonant inverters use resonant tanks operating in resonance or near of it, the current through OGs can be substituted by a sinusoidal current source with variable amplitude and frequency. According to the concept, a wide-range frequency model composed of an equivalent resistance in series of an equivalent capacitance for OGs is proposed. Because the equivalent resistance and the equivalent capacitance are closely related to switching frequency of inverter and the current through OGs, the model can be used in the wide working range. Based on the model, the characteristic of OGs is analyzed and a methodology for power supplies is developed. Through a combination of the proposed model and the four limit parameters of ozone generators and power supplies in the methodology, the main circuit parameters of the power supply for maximizing the ability of OGs are obtained. To validate the wide-range frequency model and the design methodology, an ozone generation system powered by a 14-kW series resonant inverter is built. The differences between the experimental results and the analytical results show that the proposed model has satisfying accuracy in a wide working range. Compare to the conventional methodology for power supplies, the main circuit parameters of the power supply can be obtained conveniently regardless of the heavy-load condition and light-load condition of OGs.

Analysis and Experimentation of a New Half-Bridge High-Frequency Resonant Inverter for DBD Type Ozonizer

ABSTRACTThe peak voltage across the dielectric barrier discharge (DBD) type ozonizer is a key factor for ozone synthesis, and it is hard to be kept stable in widely used high-frequency resonant inverters within the entire working range. The soft switching conditions of power switches in these resonant inverters cannot always be satisfied within the entire working range, too. To address the two questions, a new half-bridge high-frequency resonant inverter is proposed in the paper, and the expressions that accurately describe the behavior of the inverter are derived by analyzing different operating modes. The simulation and experimental results show that the peak voltage across DBD type ozonizer is kept stable, moreover, zero current switching of power switches is realized within the entire working range.

Dielectric barrier discharge and jet type plasma surface modifications of hybrid polymeric poly (ε-caprolactone)/chitosan scaffolds.

In this study, dry air plasma jet and dielectric barrier discharge Ar + O2 or Ar + N2 plasma modifications and their effects on wettability, topography, functionality and biological efficiency of the hybrid polymeric poly (ε-caprolactone)/chitosan scaffolds were reported. The samples treated with Ar + O2 dielectric barrier discharge plasma (80 sccm O2 flow rate, 3-min treatment) or with dry air plasma jet (15-cm nozzle-sample distance, 13-min treatment) had the closest wettability (49.11 ± 1.83 and 53.60 ± 0.95, respectively) to the commercial tissue culture polystyrene used for cell cultivation. Scanning electron microscopy images and X-ray photoelectron spectrometry analysis showed increase in topographical roughness and OH/NH2 functionality, respectively. Increased fluid uptake capacity for the scaffolds treated with Ar + O2 dielectric barrier discharge plasma (73.60% ± 1.78) and dry air plasma jet (72.48% ± 0.75) were also noted. Finally, initial cell attachment as well as seven-day cell viability, growth and proliferation performances were found to be significantly better for both plasma treated scaffolds than for untreated scaffolds.

Regeneration of Sooty Surface Using Nanosecond Pulsed Dielectric Barrier Discharge

In this paper, the regeneration of sooty surface by using nanosecond pulsed surface dielectric barrier discharge type reactor is investigated experimentally. The goal is to characterize the regeneration process as a function of the applied voltage magnitude and pulse polarity. The reactor is composed of two electrodes separated by a dielectric and are arranged asymmetrically. The power supply system provides high voltage pulses with the following characteristics: voltage up to ±10 kV; rise and decay time less than 50 ns; and a frequency of 2 kHz. The main results show that the regeneration performance increases with the applied voltage magnitude and the duration of treatment. Furthermore, depending on the polarity and the magnitude of the applied voltage pulse, the cleaned surface area can be either more uniform along the active electrode (negative pulses) or extended on the dielectric surface (positive pulses). The regeneration mechanism remains not very well understood, but it seems that the soot particle size is reduced mainly due to the interaction with ozone molecules and oxygen radicals generated by the discharge.

Effect of nitrogen addition to ozone generation characteristics by diffuse and filamentary dielectric barrier discharges at atmospheric pressure

Ozone is widely used for gas treatment, advanced oxidation processes, microorganisms inactivation, etc. In this research, we investigated the effect of nitrogen addition to ozone generation characteristics by atmospheric pressure Townsend discharge (APTD) type and filamentary dielectric barrier discharge (DBD) type ozone generators. The result showed that the ozone generated by the filamentary DBD increases rapidly with the increase of O2 content, and is higher than that by the APTD. On the other hand, it is interesting that the ozone generated by the APTD gradually decreases with the increase of O2 content. In order to clarify why the characteristics of ozone generation by the two kinds of discharge modes showed different dependency to the N2 content, we analyzed the exhaust gas composition using FTIR spectroscopy and calculated the rate coefficients using BOLSIG+ code. As a result, we found that although O2 content decreased with increasing N2 content, additional O atoms produced by excited N2 molecules contribute to ozone generation in case of APTD.

상압 플라즈마를 이용한 무기박막의 화학기상 증착법에 대한 연구동향

School of Advanced Materials Science and Engineering, Sungkyunkwan University (SKKU), Suwon, Gyeonggi-do 16419, Korea(Received October 14, 2015 ; revised October 28, 2015 ; accepted October 30, 2015)AbstractIn recent years, the cleaning and activation technology of surfaces using atmospheric plasma as well asthe deposition technology for coating using atmospheric plasma have been demonstrated conclusively anddrawn increasing industrial attention. Especially, due to the simplicity, the technology using atmospheric plasmaenhanced chemical vapor deposition has been widely studied from many researchers. The plasma source typecommonly used as the stabilization of diffuse glow discharges for atmospheric pressure plasma enhancedchemical vapor deposition pressure is the dielectric barrier discharge. In this review paper, some kinds ofmodified dielectric barrier discharge type will be presented. And, the characteristics of silicon based compoundsuch as SiOx and SiNx deposited using atmospheric plasma enhanced chemical vapor system will be discussed.

Enhancing the surface properties of linen by non-thermal atmospheric air-plasma treatment

Abstract In this research, a diffuse coplanar surface barrier discharge (DCSBD) type plasma reactor was used for the surface modification of raw linen fabric. Changes in physical properties and chemical composition of the fiber surface as well as color of the fabric were measured as a function of time of the atmospheric air plasma treatment. Furthermore, ageing of the effects created on the fiber surface by plasma treatment was also characterized in a period of 0-14 days elapsed after the plasma treatment. Significant differences were found between the properties of the raw and plasma treated linen fabrics, including increase of wettability, wickability, surface energy and O/C ratio, and decrease of water contact angle and deterioration of the waxy outer layer of the fibers. Most of the parameters depended on the time of plasma treatment (0–180 s). O/C ratio increased steadily with the increase of duration of the plasma treatment, which was explained by destruction of the waxy surface layer, creation of polar groups and exposure of cellulosic components. Most of the properties tested were found to be stable during two weeks of storage after the plasma treatment, indicating that the surface ‘topography’ created by plasma remained almost unaltered and the recovery of the etched waxy coverage of the fiber did not occur.

Experimental Investigation of Tip Clearance Flow in a Transonic Compressor With and Without Plasma Actuators

Blade tip losses represent a major performance penalty in low aspect ratio transonic compressors. This paper reports on the experimental evaluation of the impact of tip clearance with and without plasma actuator flow control on performance of an U.S. Air Force-designed low aspect ratio, high radius ratio single-stage transonic compressor rig. The detailed stage performance measurements without flow control at three clearance levels, classified as small, medium, and large, are presented. At design-speed, increasing the clearance from small to medium resulted in a stage peak efficiency drop of almost six points with another four point drop in efficiency with the large clearance (LC). Comparison of the speed lines at high-speed show significantly lower pressure rise with increasing tip clearance, the compressor losing 8% stall margin (SM) with medium clearance (MC) and an additional 1% with the LC. Comparison of the stage exit radial profiles of total pressure and adiabatic efficiency at both part-speed and design-speed and with throttling are presented. Tip clearance flow-control was investigated using dielectric barrier discharge (DBD) type plasma actuators. The plasma actuators were placed on the casing wall upstream of the rotor leading edge and the compressor mapped from part-speed to high-speed at three clearances with both axial and skewed configurations at six different frequency levels. The plasma actuators did not impact steady state performance. A maximum SM improvement of 4% was recorded in this test series. The LC configuration benefited the most with the plasma actuators. Increased voltage provided more SM improvement. Plasma actuator power requirements were almost halved going from continuous operation to pulsed plasma. Most of the improvement with the plasma actuators is attributed to the reduction in unsteadiness of the tip clearance vortex near-stall resulting in additional reduction in flow prior to stall.

Active Control of a Backward Facing Step Flow With Plasma Actuators

Active control over a backward facing step flow is studied experimentally by means of plasma based devices. The Reynolds number based on the step height h is 1520. An electrohydrodynamic actuator (EHD), dielectric barrier discharge (DBD) type, is flush mounted to the step wall. The DBD configuration adds momentum locally, normal to the separated shear layer, thus producing strong modifications downstream. The actuation is periodic and its frequency and amplitude are scrutinized to characterize the flow behavior under forcing. Measures of velocity fields for these flows are obtained from particle image velocimetry (PIV). As reported by previous works, the reattachment length shows an important reduction for an optimum forcing frequency. This value closely matches the shear layer flow natural frequency. On the other hand, the flow is less sensitive to the forcing amplitude though the analysis allows us to optimize the actuation in order to save power consumption.

Atmospheric Pressure Plasma Treatment and Following Aging Effect of Chromium Surfaces

The results of atmospheric pressure plasma treatments using diffuse coplanar surface barrier discharge (type of surface dielectric barrier discharge) on chromium surfaces are reported. A significant increase of surface wettability was observed after short plasma exposition. A quantitative value of surface wettability, i.e. the surface free energy, changed from 29 mJ/m2 to over 80 mJ/m2. In time, a hydrophobic recovery of the plasma treated surfaces was observed. Careful study by surface free energy measurements and x-ray photoelectron spectroscopy was performed to be able explaining the effects of plasma treatment. Studied samples were treated in air, oxygen and nitrogen plasma and aged in air and vacuum. Main reasons for increased wettability and aging effect are surface cleaning and transformations in chromium oxide. Additionally, generation of surface nitrate groups was found on the chromium surface as a result of plasma treatment in humid air.

Promoted cell and material interaction on atmospheric pressure plasma treated titanium

Surface carbon contamination is a natural phenomenon. However, it interferes with cell–biomaterial interaction. In order to eliminate the interference, atmospheric pressure plasma treatment was employed. Dielectric barrier discharge treatment of titanium surface for less than 10min turned titanium super-hydrophilic. Adsorption of fibronectin which is the major cell adhesive protein increased after plasma treatment. Cell attachment parameters of osteoblast cells such as population, cell area, perimeter, Feret's diameter and cytoskeleton development were also enhanced. Cell proliferation increased on the plasma treated titanium. In conclusion, dielectric barrier discharge type atmospheric pressure plasma system is effective to modify titanium surface and the modified titanium promotes cell and material interactions.

Ozone Production Characteristics of Barrier Discharge Type Reactor Driven by Pulsed Power

Ozone Production Characteristics of Barrier Discharge Type Reactor Driven by Pulsed Power

A combined process of non-thermal plasma with sludge stabilization for the simultaneous reduction of odor and organic waste

Odor emissions and sludge disposals have become most challenging issues in many sludge treatment plants, and separate chemical oxidation processes have been commonly employed for these problems. It is, therefore, necessary to develop a combined process that simultaneously reduces the odor emissions and the amount of waste sludge. In this study, a non-thermal plasma reactor using a dielectric barrier discharge type was employed to treat a gas stream contaminated with 10 ppm(v) of H(2)S, and then the ozone-laden gas stream was supplied to a sludge stabilizer to reduce the organic constituents. The specific energy input to the plasma was varied to investigate the performance of the combined process. When the specific energy inputs were 200, 260, and 360 J/L, the rates of ozone generation from the plasma reactor were 0.036, 0.070, 0.144 g-O(3)/h, respectively. At these experimental conditions, the removal efficiencies of H(2)S were 60, 75, and >99%, and total chemical oxygen demand (TCOD) reduction efficiencies of 33, 61 and 67% were observed. In addition, a soluble organic fraction of the sludge increased at ratios of 1.9, 8.9, and 10.7%, respectively. Consequently, the combined process effectively and simultaneously reduced the odor compounds as well as the organic constituents and particles in the waste sludge.