Formation mechanism of bright and dark concentric-ring pattern in dielectric barrier discharge

In this work,a bright and dark concentric-ring pattern is reported in a dielectric barrier discharge for the first time.The spatiotemporal dynamics of the bright and dark concentric-ring pattern are investigated with an intensified charge-coupled device and photomultiplier tubes.The results indicate that the bright and dark concentric-ring pattern is composed of three concentric-ring sublattices.These are bright concentric-ring structures,dark concentric-ring structures and wider concentric-ring structures,respectively.The bright concentric-ring structures and dark concentricring structures are alternately distributed.The bright concentric-ring structures are located at the centre of the wider concentric-ring structures.The wider concentric-ring structures first form from the outer edge and gradually develop to the centre.The essence of all three concentric-ring structures is the individual discharge filaments.The optical emission spectra of different sublattices are acquired and analysed.It is found that the plasma parameters of the three concentricring sublattices are different.Finally,the formation mechanism of the bright and dark concentricring pattern is discussed.

NaCl aqueous solution as a novel electrode in a dielectric barrier discharge reactor for highly efficient ozone generation

Ozone(O_(3)) generated by a dielectric barrier discharge(DBD) is widely used in various industrial processes. In this study, NaCl aqueous solution was used as a novel electric power transmission electrode in a DBD reactor(instead of a traditional metal electrode) for highly efficient ozone generation. The results demonstrated that a high O_(3) yield of 242 g k Wh^(-1) with a concentration of 14.6 g m^(-3)O_(3) was achieved. The power transmission mechanism works because NaCl aqueous solution behaves as a capacitor when an alternating pulse voltage below 8 k Hz is used.Compared with the resistance of the discharge barrier and discharge space, the resistance of NaCl aqueous solution can be ignored, which ensures that O_(3) is generated efficiently. It is expected that O_(3) generation using NaCl aqueous solution as a novel electrode in a DBD reactor could be an alternative technology with good application prospects.

Degradation of sulfamethoxazole in water by dielectric barrier discharge plasma jet:influencing parameters,degradation pathway,toxicity evaluation

Sulfamethoxazole(SMX)is an antibiotic and widely present in aquatic environments,so it presents a serious threat to human health and sustainable development.A dielectric barrier discharge(DBD)plasma jet was utilized to degrade aqueous SMX,and the effects of various operating parameters(working gas,discharge power,etc)on SMX degradation performance were studied.The experimental results showed that the DBD plasma jet can obtain a relatively high degradation efficiency for SMX when the discharge power is high with an oxygen atmosphere,the initial concentration of SMX is low,and the aqueous solution is under acidic conditions.The reactive species produced in the liquid phase were detected,and OH radicals and O3were found to play a significant role in the degradation of SMX.Moreover,the process of SMX degradation could be better fitted by the quasi-first-order reaction kinetic equation.The analysis of the SMX degradation process indicated that SMX was gradually decomposed and 4-amino benzene sulfonic acid,benzene sulfonamide,4-nitro SMX,and phenylsulfinyl acid were detected,and thus three possible degradation pathways were finally proposed.The mineralization degree of SMX reached 90.04%after plasma treatment for 20 min,and the toxicity of the solution fluctuated with the discharge time but eventually decreased.

Surface Modification of Fluororubber Using Atmospheric Pressure Dielectric Barrier Discharge(DBD)

Fluoride rubber F2311 film, an alternating copolymer of CF2-CFC1 （CTFE） and CH2-CF2 （VF2） components, was treated by atmospheric pressure dielectric barrier discharge （DBD） in air. The surface structure, topography and surface chemistry of the treated F2311 films were characterized by contact angle measurement, atomic force microscopy （AFM）, and X-ray photoelectron spectroscopy （XPS）, respectively. The experimental results showed that a short time air plasma treatment led to morphological, wettability and chemical changes in the F2311 films. The surface hydrophilicity increased greatly after the plasma treatment, the static water contact angle decreased from 98.6° to 32°, and oxygen containing groups （C=O, O-C=O, etc. ） were introduced. Atomic force microscopy revealed that plasma produced by DBD etched F2311 films obviously. The roughness of the samples increased remarkably with the formation of peaks and valleys on the treated surfaces. The increased surface wettability may be correlated with both the introduction of hydrophilic groups due to air plasma oxidation of the surface and the change in surface morphology etched by DBD.

Toluene removal characteristics by a superimposed wire-plate dielectric barrier discharge plasma reactor

A superimposed wire-plate dielectric barrier discharge reactor was used to remove toluene in this study. The effects of oxygen content, gas flow rate, gas initial concentration and with/without catalyst on toluene decomposition were investigated. It was found that an optimal toluene removal was achieved when the oxygen content was about 5%. Under this condition, the highest toluene removal efficiency of 80.8% was achieved when the gas concentration was 80 mg/m^3. The toluene removal efficiency decreased with the increase of the gas flow rate and the initial concentration of toluene. In addition, the ozone concentration decreased with the increase of the initial concentration of toluene. It suggested that combining DBD （dielectric barrier discharge） with Co3O4/Al2O3/foam nickel catalyst in-situ could improve the toluene removal efficiency and suppress ozone formation. Products analysis showed that the main products were CO and CO2 when oxygen was more than 5%.

Discoloration of Congo Red by Rod-Plate Dielectric Barrier Discharge Processes at Atmospheric Pressure

A dielectric barrier discharge （DBD） reactor with a rod-plate electrode configuration was used for the oxidative decomposition of Congo red dye in an aqueous solution. Plasma was generated in the gas space above the water interface under atmospheric pressure. Discharge characteristics were analyzed by voltage-current waveforms. Effects of applied voltage, initial conductivity, and initial concentration were also analyzed. Congo red discoloration increased with increased applied voltage and decreased conductivity. The initial conductivity significantly influenced the Congo red discoloration. Under the same conditions, the highest discoloration rate was obtained at 25 mg/L. The presence of ferrous ions in the solutions had a substantial positive effect on Fenton dye degradation and flocculation. At an applied voltage of 20 kV, about 100% of dye was degraded after 4 min of Fe^2＋/DBD treatment. Results showed that adding a certain dosage of hydrogen peroxide to the wastewater could enhance the discoloration rate. Possible pathways of Congo red discoloration by DBD plasma were proposed based on GC/MS, FTIR, and UV-vis spectroscopy analyses.

Degradation of Aniline Wastewater Using Dielectric Barrier Discharges at Atmospheric Pressure

Aniline is a toxic water pollutant detected in drinking water and surface water, and this chemical is harmful to both human and aquatic life. A dielectric barrier discharge （DBD） reactor was designed in this study to investigate the treatment of aniline in aqueous solution. Discharge characteristics were assessed by measuring voltage and current waveforms, capturing light emission images, and obtaining optical emission spectra. The effects of several parameters were analyzed, including treatment distance, discharge power, DBD treatment time, initial pH of aniline solutions, and addition of sodium carbonate and hydrogen peroxide to the treatment. Aniline degradation increased with increasing discharge power. Under the same conditions, higher degradation was obtained at a treatment distance of 0 mm than at other treatment distances. At a discharge power of 21.5 W, 84.32% of aniline was removed after 10 rain of DBD treatment. Initial pH significantly influenced aniline degradation. Adding a certain dosage of sodium carbonate and hydrogen peroxide to the wastewater can accelerate the degradation rate of aniline. Possible degradation pathways of aniline by DBD plasmas were proposed based on the analytical data of GC/MS and TOC.

Experimental Study on Inactivation of Bacterial Endotoxin by Using Dielectric Barrier Discharge

The low-temperature plasma （LTP） generated by dielectric barrier discharge （DBD） was used to sterilize the E.coli endotoxin, which is usually difficult to kill by traditional methods. Three different concentrations of bacterial endotoxin （1 EU/mL, 0.5 EU/mL and 0.25 EU/mL） were treated by LTP for different time （20 s, 40 s and 60 s）. Tachypleus amebocyte lysate （TAL） method was employed to detect the concentration variation of bacterial endotoxin before and af- ter the plasma treatment, and endotoxic shock mice model was used to evaluate the inactivation effects of LTP on endotoxin for further study. Experimental results demonstrated that, DBD plasma can inactivate the bacterial endotoxin quickly and effectively, and when the LTP treatment time was increased, the concentrations of bacterial endotoxin decreased gradually （after 60 s plasma treatment, its inactivation effect was beyond the Chinese pharmacopoeia standard）, and the average survival time of mice gradually extended. The possible inactivation mechanisms are proposed to be related to reactive oxygen species （ROSs）.

Preparation of Copper Nanoparticles Using Dielectric Barrier Discharge at Atmospheric Pressure and its Mechanism

Dielectric barrier discharge （DBD） cold plasma at atmospheric pressure was used for preparation of copper nanoparticles by reduction of copper oxide （CuO）. Power X-ray diffraction （XRD） was used to characterize the structure of the copper oxide samples treated by DBD plasma. Influences of H2 content and the treating time on the reduction of copper oxide by DBD plasma were investigated. The results show that the reduction ratio of copper oxide was increased initially and then decreased with increasing H2 content, and the highest reduction ratio was achieved at 20% H2 content. Moreover, the copper oxide samples were gradually reduced by DBD plasma into copper nanoparticles with the increase in treating time. However, the average reduction rate was decreased as a result of the diffusion of the active hydrogen species. Optical emission spectra （OES） were observed during the reduction of the copper oxide samples by DBD plasma, and the reduction mechanism was explored accordingly. Instead of high-energy electrons, atomic hydrogen （H） radicals, and the heating effect, excited-state hydrogen molecules are suspected to be one kind of important reducing agents. Atmospheric-pressure DBD cold plasma is proved to be an efficient method for preparing copper nanoparticles.

Surface Treatment of Polypropylene Films Using Dielectric Barrier Discharge with Magnetic Field

Atmospheric pressure non-thermal plasma is of interest for industrial applications. In this study, polypropylene （PP） films are modified by a dielectric barrier discharge （DBD） with a non-uniform magnetic field in air at atmospheric pressure. The surface properties of the PP films before and after a DBD treatment are studied by using contact angle measurement, atomic force microscopy （AFM） and X-ray photoelectron spectroscopy （XPS）. The effect of treatment time on the surface modification with and without a magnetic field is investigated. It is found that the hydrophilic improvement depends on the treatment time and magnetic field. It is also found that surface roughness and oxygen-containing groups are introduced onto the PP film surface after the DBD treatment. Surface roughness and oxygen-containing polar functional groups of the PP films increase with the magnetic induction density. The functional groups are identified as C-O, C=O and O-C=O by using XPS analysis. It is concluded that the hydrophilic improvement of PP films treated with a magnetic field is due to a greater surface roughness and more oxygen-containing groups.

Study on the Microsecond Pulse Homogeneous Dielectric Barrier Discharges in Atmospheric Air and Its Influencing Factors

The homogeneous dielectric barrier discharge （DBD） in atmospheric air between two symmetric-columnar copper electrodes with epoxy plates as the dielectric barriers is generated using a us pulse high voltage power supply. The discharge characteristics are studied by measurement of its electrical discharge parameters and observation of its light emission phenom- ena, and the main discharge parameters of the homogenous DBD, such as discharge current and average discharge power, are calculated. Results show that the discharge generated is a homogeneous one with one larger single current pulse of about 2 #s duration appearing in each voltage pulse, and its light emission is radially homogeneous and covers the entire surface of the two elec- trodes. The influences of applied voltage amplitude, air gap distance and barrier thickness on the transition of discharge modes are studied. With the increase of air gap distance, the discharge will transit from homogeneous mode to filamentary mode. The higher the thickness of dielectric barriers, the larger the air gap distance for generating the homogeneous discharge mode. The average discharge power increases non-linearly with increasing applied voltage amplitude, and decreases non-linearly with the increase of air gap distance and barrier thickness. In order to generate stable and homogeneous DBD with high discharge power, thin barriers distance should be used, and higher applied voltage amplitude should be applied to small air gap.

Destruction of Gaseous Styrene with a Low-Temperature Plasma Induced by a Tubular Multilayer Dielectric Barrier Discharge

The destruction of gaseous styrene was studied using a low-temperature plasma induced by tubular multilayer dielectric barrier discharge（DBD）.The results indicate that the applied voltage,gas flow rate,inlet styrene concentration and reactor configuration play important roles in styrene removal efficiency （ηstyrene） and energy yield（EY）.Values of ηstyrene and EY reached 96%and 15567 mg/kWh when the applied voltage,gas flow rate,inlet styrene concentration and layers of quartz tubes were set at 10.8 kV,5.0 m/s,229 mg/m^3 and 5 layers,respectively.A qualitative analysis of the byproducts and a detailed discussion of the reaction mechanism are also presented.The results could facilitate industrial applications of the new DBD reactor for waste gas treatment.

Three Discharge Modes of Dielectric Barrier Discharge in a Two-phase Mixture

两相体介质阻挡放电（dielectric barrier discharge in atwo-phase mixture,TPM-DBD）是在大气压下产生低温等离子体的重要方法,因具有很高的能量密度而被广泛应用在污染治理中。为研究介质颗粒的填充方式对TPM-DBD的影响,以γ-Al2O3作为填充介质颗粒,将数码相机与体视显微镜连体拍摄放电显微照片。结果发现,随着电压变化,TPM-DBD由3种依次串联发生的放电构成。电压较低时,首先在颗粒与极板间发生剩余间隙放电;随着电压增加,颗粒沿面放电串联发生;电压继续增加,孔隙放电串联发生。当颗粒间距较大时,在颗粒的远域出现典型的丝状放电,而近域内出现可能为汤森放电的放电＂暗区＂。外电场的数值计算结果初步说明了上述现象,电场畸变是其主要原因。研究结果为调节TPM-DBD的放电形式,进而高效率应用提供了较好的支持。

Simulation Study on Multi-Pulse Phenomena of Atmospheric Pressure Argon Dielectric Barrier Discharge

In this paper, a one-dimensional discharge model is employed to study multi-pulse phenomena in Ar dielectric barrier discharge （DBD） under atmospheric pressure. The finiteelement method is employed to solve the model. The influences of applied voltage amplitude and frequency as well as gas gap distance on the variation of multi discharge pulses are investigated and discussed. The simulation results show that, both the intensity of discharge current and the number of discharge pulses increase with the amplitude of applied voltage, and narrower gas gap is more favorable for the formation of multi pulses. It is revealed that Ar DBDs behave in glow discharge mode when the applied voltage and gas gap distance vary from 2 kV to 6 kV and from 1 mm to 3 mm, respectively. With the frequency decreasing from 250 Hz to 125 Hz, the intensity of discharge current weakens and the number of discharge pulses increases, and the discharges behave in the typical Townsend discharge mode.

Improving Hydrophobicity of Glass Surface Using Dielectric Barrier Discharge Treatment in Atmospheric Air

Non-thermal plasmas under atmospheric pressure are of great interest in industrial applications, especially in material surface treatment. In this paper, the treatment of a glass surface for improving hydrophobicity using the non-thermal plasma generated by dielectric barrier discharge （DBD） at atmospheric pressure in ambient air is conducted, and the surface properties of the glass before and after the DBD treatment are studied by using contact angle measurement, surface resistance measurement and wet flashover voltage tests. The effects of the applied voltage and time duration of DBD on the surface modification are studied, and the optimal conditions for the treatment are obtained. It is found that a layer of hydrophobic coating is formed on the glass surface after spraying a thin layer of silicone oil and undergoing the DBD treatment, and the improvement of hydrophobicity depends on DBD voltage and treating time. It seems that there exists an optimum treating time for a certain applied voltage of DBD during the surface treatment, The test results of thermal aging and chemical aging show that the hydrophobic layer has quite stable characteristics. The interaction mechanism between the DBD plasma and the glass surface is discussed. It is concluded that CHa and large molecule radicals can react with the radicals in the glass surface to replace OH, and the hydrophobicity of the glass surface is improved accordingly.

Optimization of Dielectric Barrier Discharge Process for Decolorization of Reactive Blue 19 by Means of Response Surface Methodology

The decolorization of reactive blue 19(RB-19)as a model dye from aqueous solutions has been studied by means of the dielectric barrier discharge(DBD)process.The independent parameters of input power,initial dye concentration and initial pH value were evaluated respectively.Experimental data were optimized by means of a 33 factorial design and response surface methodology(RSM).The dye was quickly removed during the treatment,yielding 96.9%of decolorization efficiency under optimized conditions.Therefore,the total organic carbon(TOC)and chemical oxygen demand(CODcr)results indicated that only the chromophore was destroyed rather than completed oxidation.This was confirmed with UV-vis and tertiary butanol assessments during the DBD treatment.

Surface Dielectric Barrier Discharge

This project is concerned with surface dielectric barrier discharge(DBD),which involve designing the configuration of discharge and experiment,collecting and analysis data from experiment and simulation.Therefore,this report includes the objective of the project and general information of background.It also briefly introduces the history and theory of dielectric barrier discharge.For the experiment how to design the discharge implement and why.Then it will show the experiment in different configurations,and the analysis data collected in experiment also explain the data for finding out the properties of surface dielectric barrier discharge and what the difference between surface discharge and vertical discharge are.High frequency power supplied will be used for viewing the phenomenon of discharge.Compare the spectrums of discharge on dielectric and air discharge.Finally,it is the main conclusions and introduction of the difference of surface dielectric barrier discharge and vertical discharge.There are some conclusions.Discharge voltage increase linearly with applied voltage.Discharge power increase non-linearly with the discharge voltage.The gap of high voltage electrodes will not affect discharge voltage and discharge power.Discharge power increases with the frequency of power supply.Discharge area will expand when the applied voltage increases.

DBD等离子体协同MnFe_(2)O_(4)降解氢氯噻嗪性能研究

文章研究介质阻挡放电(dielectric barrier discharge,DBD)等离子体协同MnFe_(2)O_(4)对常用药物氢氯噻嗪(hydrochlorothiazide,HCTZ)在水中的降解性能。通过溶剂热法制备磁性锰铁氧体MnFe_(2)O_(4)作为非均相芬顿催化剂,采用X射线衍射(X-ray diffraction,XRD)、X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)和扫描电子显微镜(scanning electron microscope,SEM)分析手段对其结构进行表征。利用HCTZ模拟目标废水,分别研究不同的HCTZ初始质量浓度、溶液初始pH值、电源输入功率和MnFe_(2)O_(4)投放剂量等因素对体系降解性能的影响,结果显示随着药物初始质量浓度的提高会使降解效率持续下降,不断提升放电功率将更利于HCTZ的降解,且碱性环境会对处理过程产生抑制效应。同时研究发现,DBD/MnFe_(2)O_(4)体系下的最佳MnFe_(2)O_(4)投放剂量是50 mg,并且经5次循环使用后,体系仍能在25 min内将99%的HCTZ去除,表现出良好的重复使用性能。

DBD协同NiO/α-Mn_(3)O_(4)催化降解气态邻氯甲苯

为提高介质阻挡放电(DBD)对氯代挥发性有机化合物(CVOCs)的处理效果,采用共沉淀法制备了NiO/α-Mn_(3)O_(4)复合催化剂,并协同DBD催化降解气态邻氯甲苯。通过X射线衍射仪、扫描电子显微镜以及比表面积与孔径分析仪对催化剂进行表征并探究了气体流速、外施电压、初始浓度和相对湿度等工艺参数对邻氯甲苯降解效率和能量产率的影响。结果表明:当Ni/Mn摩尔比为0.3,煅烧温度为400℃时,NiO/α-Mn_(3)O_(4)复合催化剂的催化性能最佳。邻氯甲苯的初始浓度为140 mg/m^(3),外施电压为8 kV,气体流速为0.9 m^(3)/h和相对湿度为65%时,邻氯甲苯的降解效率和矿化率较单独的DBD系统分别提高了33.9%和13.1%,O_(3)浓度和NO_(2)浓度分别降低了48.2 mg/m^(3)和12.3 mg/m^(3),CO_(2)选择性提高了12%。

A Study of the Aging of a-Al_2O_3 Dielectric Material in DBD Plasma

The performance of dielectric material is a key factor against a long time action in dielectric barrier discharge （DBD） plasma. In this study, the aging of the Al2O3 dielectric material was studied by the Atomic Force Microscope （AFM）, X-ray Photoelectron spectrum （XPS） and Auger electron spectrum （AES） methods. The results showerd that the performance of the dielectric does not descend after an 1000 h aging experiment. Therefore the thin dielectric layers of α-Al2O3 porcelain with a purity above 99% can sustain a long time action of DBD plasma and form gas ionization discharges steadily.