共查询到20条相似文献，搜索用时 35 毫秒
1.
Bing QI 《等离子体科学和技术》2019,21(8):85402-52
In this study, the density of metastable He2* in an atmospheric-pressure plasma jet operating in helium with 0.001% nitrogen has been measured using an auxiliary measuring electrode technique. In the glow discharge mode, waveforms from two grounding electrodes, including one main discharge electrode and one auxiliary electrode, are captured. The isolated current peak formed by Penning ionization in waveforms from the auxiliary measuring electrode is identified to calculate the density of metastable He2*. In our discharge environment, the helium metastable densities along the jet axis direction are between 2.26× 1013 and 1.74× 1013 cm-3, which is in good agreement with the results measured by other techniques. This measurement technique can be conveniently applied to the diagnosis of metastableHe2* in an atmospheric-pressure plasma jet array. 相似文献
2.
To understand the self sustained propagation of the plasma jet/bullet in air under atmospheric pressure, the ignition of the plasma jet/bullet, the plasma jet/bullet ignition point in the plasma pencil, the formation time and the formation criteria from a dielectric barrier configured plasma pencil were investigated in this study. The results were confirmed by comparing these results with the plasma jet ignition process in the plasma pencil without a dielectric barrier. Electrical, optical, and imaging techniques were used to study the formation of the plasma jet from the ignition of discharge in a double dielectric barrier configured plasma pencil. The investigation results show that the plasma jet forms at the outlet of the plasma pencil as a donut shaped discharge front because of the electric field line along the outlet’s surface. It is shown that the required time for the formation of the plasma jet changes with the input voltage of the discharge. The input power calculation for the gap discharge and for the whole system shows that 56% of the average input power is used by the first gap discharge. The estimated electron density inside the gap discharge is in the order of 1011cm-3 . If helium is used as a feeding gas, a minimum 1.48×10-8C charge is required per pulse in the gap discharge to generate a plasma jet. 相似文献
3.
In this study, the effects of the fluid cooling and electric field line deformation were investigatedin a dielectric barrier discharge (DBD) plasma source. The DBD plasma jet is improved bycovering the ground electrode and a power electrode with insulating oil. We obtained positiveresults as insulating oil prevents arc formation, while it improved the supplied power and plasmajet length, and increased radical production. Radical production of this nonthermal plasma jet isstudied with polyvinyl alcohol–potassium iodide liquid. 相似文献
4.
Ashraf FARAHAT 《等离子体科学和技术》2015,17(10):853-861
Plasma-neutral gas dynamics is computationally investigated in a miniaturized microthruster that encloses Ar and contains dielectric material sandwiched between two metal plates using a two-dimensional plasma mode. Spatial and temporal plasma properties are investigated by solving the Poisson equation with the conservation equations of charged and excited neutral plasma species using the COMSOL Multiphysics 4.2b. The microthruster property is found to depend on the secondary electron emission coefficient. The electrohydrodynamic force(EHD) is calculated and found to be significant in the sheath area near the dielectric layer and is found to affect gas flow dynamics including the Ar excimer formation and density. The effects of pressure and secondary emission coefficient are discussed. The plasma characteristics are affected by small changes in the secondary electron emission coefficient, which could result from the dielectric erosion and aging, and is found to affect the electrohydrodynamic force produced when the microthruster is used to produce thrust for a small spacecraft. 相似文献
5.
An atmospheric pressure dielectric barrier discharge (DBD) plasma jet generator using air flow as the feedstock gas was applied to decontaminate the chemical agent surrogates on the surface of aluminum, stainless steel or iron plate painted with alkyd or PVC. The experimental results of material decontamination show that the residual chemical agent on the material is lower than the permissible value of the National Military Standard of China. In order to test the corrosion effect of the plasma jet on different material surfaces in the decontamination process, corrosion tests for the materials of polymethyl methacrylate, neoprene, polyvinyl chloride (PVC), polyethylene (PE), phenolic resin, iron plate painted with alkyd, stainless steel, aluminum, etc. were carried out, and relevant parameters were examined, including etiolation index, chromatism, loss of gloss, corrosion form, etc. The results show that the plasma jet is slightly corrosive for part of the materials, but their performances are not affected. A portable calculator, computer display, mainboard, circuit board of radiogram, and a hygrometer could work normally after being treated by the plasma jet. 相似文献
6.
Zhi SU 《等离子体科学和技术》2022,24(6):65501
An array of 30 plasma synthetic jet actuators (PSJAs) is deployed using a modified multichannel discharge circuit to suppress the flow separation over a straight-wing model. The lift and drag of the wing model are measured by a force balance, and the velocity fields over the suction surface are captured by a particle imaging velocimetry system. Results show that the flow separation of the straight wing originates from the middle of the model and expands towards the wingtips as the angle of attack increases. The flow separation can be suppressed effectively by the PSJAs array. The best flow control effect is achieved at a dimensionless discharge frequency of F+ = 1, with the peak lift coefficient increased by 10.5% and the stall angle postponed by 2°. To further optimize the power consumption of the PSJAs, the influence of the density of PSJAs on the flow control effect is investigated. A threshold of the density exits (with the spanwise spacing of PSJAs being 0.2 times of the chord length in the current research), below which the flow control effect starts to deteriorate remarkably. In addition, for comparison purposes, a dielectric barrier discharge (DBD) plasma actuator is installed at the same location of the PSJAs. At the same power consumption, 4.9% increase of the peak lift coefficient is achieved by DBD, while that achieved by PSJAs reaches 5.6%. 相似文献
7.
Jiyuan YAN Guishu LIANG Hongliang LIAN Yanze SONG Haoou RUAN Qijun DUAN Qing XIE 《等离子体科学和技术》2021,23(11):115501-95
This work treats the Al2O3-ER sample surface using dielectric barrier discharge fluorination(DBD-F),DBD silicon deposition(DBD-Si),atmospheric-pressure plasma jet fluorination(APPJ-F)and APPJ silicon deposition(APPJ-Si).By comparing the surface morphology,chemical components and electrical parameters,the diverse mechanisms of different plasma modification methods used to improve flashover performance are revealed.The results show that the flashover voltage of the DBD-F samples is the largest(increased by 21.2％at most),while the APPJ-F method has the worst promotion effect.The flashover voltage of the APPJ-Si samples decreases sharply when treatment time exceeds 180 s,but the promotion effect outperforms the DBD-Si method during a short modified time.For the mechanism explanation,firstly,plasma fluorination improves the surface roughness and introduces shallow traps by etching the surface and grafting fluorine-containing groups,while plasma silicon deposition reduces the surface roughness and introduces a large number of shallow traps by coating SiOx film.Furthermore,the reaction of the DBD method is more violent,while the homogeneity of the APPJ modification is better.These characteristics influence the effects of fluorination and silicon deposition.Finally,increasing the surface roughness and introducing shallow traps accelerates surface charge dissipation and inhibits flashover,but too many shallow traps greatly increase the dissipated rate and facilitate surface flashover instead. 相似文献
8.
Rui LIU 《等离子体科学和技术》2019,21(5):54001-13
The oxygen plasma reactor based on dielectric barrier discharge principle can produce a high concentration of reactive oxygen species, which can cooperate with hydraulic cavitation gas–liquid mixer to realize the application of advanced oxidation technology in water treatment. In this technology, the work pressure of the oxygen plasma reactor is decreased by the vacuum suction effect generated in the snap-back section of the gas–liquid mixed container. In this paper, the characteristics of single micro-discharge at different pressures were investigated with the methods of discharge image, electrical characteristics and spectral diagnosis, in order to analyze the electrical characteristics and reactive oxygen species generation efficiency of oxygen plasma reactor at the pressure range from 60 kPa to 100 kPa. The study indicated that, when the pressure decreases, the duty ratio of ionization in the discharge gap and number of electrons with high energy increases, leading to a rise in reactive oxygen species production. When the oxygen reaches the maximum ionization, the concentration of reactive oxygen species is the highest. Then, the discharge intensity continues to increase, producing more heat, which will decompose the ozone and lower the production of reactive oxygen species. The oxygen plasma reactor has an optimum working pressure at different input powers, which makes the oxygen plasma reactor the most efficient in generating reactive oxygen species. 相似文献
9.
Polyethylene（PE） films are treated using an atmospheric pressure plasma jet（APPJ） with He or He/O2 gas for different periods of time.The influence of gas type on the plasma-polymer interactions is studied.The surface contact angle of the PE film can be effectively lowered to 58° after 20 s of He/O2 plasma treatment and then remains almost unchanged for longer treatment durations,while,for He plasma treatment,the film surface contact angle drops gradually to 47° when the time reaches 120 s.Atomic force microscopy（AFM） results show that the root mean square（RMS） roughness was significantly higher for the He/O2 plasma treated samples than for the He plasma treated counterparts,and the surface topography of the He/O2plasma treated PE films displays evenly distributed dome-shaped small protuberances.Chemical composition analysis reveals that the He plasma treated samples have a higher oxygen content but a clearly lower percentage of-COO than the comparable He/O2 treated samples,suggesting that differences exist in the mode of incorporating oxygen between the two gas condition plasma treatments.Electron spin resonance（ESR） results show that the free radical concentrations of the He plasma treated samples were clearly higher than those of the He/O2 plasma treated ones with other conditions unchanged. 相似文献
10.
In this study, argon and nitrogen were used as the discharge gases in radio-frequency （RF： 13.56 MHz） powered dielectric barrier atmospheric plasma. It was noticed that in single dielectric barrier discharge （DBD） with nitrogen as the discharge gas, or in argon plasma with a high applied power, micro-filament channels were easily formed. The channels in these two kinds of discharge were both constrictive on the bare metallic electrode and expansive on the opposite electrode covered with a quartz layer. The number of micro-channels was increased along with the input power, which caused the change in the I-V curve shape, i.e., the current kept increasing and the voltage fluctuated within a confined range. With double dielectric layers, however, no micro-channels appeared in the ICCD images, and the I-V curve demonstrated a totally different shape. It was assumed that micro-filaments exhibited a restraining effect on the discharge voltage. The mechanism of this restraining effect was explored in this work. 相似文献
11.
The sterilizing effect of the non-equilibrium atmospheric pressure plasma jet by applying it to the Bacillus subtilis spores is invesigated. A stable glow discharge in argon or helium gas fed with active gas （oxygen）, was generated in the coaxial cylindrical reactor powered by the radio-frequency power supply at atmospheric pressure. The experimental results indicated that the efficiency of killing spores by making use of an Ar/O2 plasma jet was much better than with a He/O2 plasma jet. The decimal reduction value of Ar/O2 and He/O2 plasma jets under the same experimental conditions was 4.5 seconds and 125 seconds, respectively. It was found that there exists an optimum oxygen concentration for a certain input power, at which the sterilization efficiency reaches a maximum value. It is believed that the oxygen radicals are generated most efficiently under this optimum condition. 相似文献
12.
陈思乐;任鑫柳;陈兆权;徐笑娟;程涛;李平;张冠军;卢新培 《等离子体科学和技术》2023,25(11):115401-115401
Atmospheric fluorocarbon plasma plays an important role in the surface modification of insulating materials like polymers. The existing fluorocarbon plasma is usually generated by dielectric barrier discharge, which has a low concentration of reactive species and may cause insufficient surface fluorination. This work attempts to develop an atmospheric fluorocarbon plasma jet using a coaxial transmission line resonator by microwave discharge with locally enhanced electric field and high density. The gas temperature is reduced by pulse modulation technology. Three kinds of working gases, pure CF4, Ar/CF4 and He/CF4, are utilized to generate the atmospheric microwave fluorocarbon plasma jet. The discharge images, optical emission spectra, electron densities and gas temperatures are studied experimentally. The results show that the Ar/CF4 plasma jet has the best comprehensive performance, such as strong discharge intensity and controllable gas temperature. The electron density of the Ar/CF4 plasma jet has a magnitude of 1020 m−3, indicating a higher density than that of the frequently used dielectric barrier discharge. With the other conditions unchanged, the gas temperature at the end of the Ar/CF4 plasma jet can be reduced from 410.2 to 347.3 K by decreasing the duty cycle of the modulated pulse from 0.5 to 0.1. Thence, the microwave Ar/CF4 plasma jet is considered to be a promising fluorocarbon plasma source for surface fluorination of polymers. 相似文献
13.
A supported TiO2/γ-Al2O3 photocatalyst has been prepared by γ-Al2O3 pellet-filled dielectric barrier discharges induced plasma CVD at atmospheric pressure and room temperature.The TiO2/γ-Al2O3 photocatalyst exhibits higher photocatalytic activity than Degussa P25, and much higher photocatalytic activity than that prepared by thermal CVD. 相似文献
14.
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 O3 were 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. 相似文献
15.
A supported TiO2/γ-A12O3 photocatalyst has been prepared by γ-Al2O3 pellet-filled dielectric barrier discharges induced plasma CVD at atmospheric pressure and room temperature. The TiO2/γ-Al203 photocatalyst exhibits higher photocatalytic activity than Degussa P25, and much higher photocatalytic activity than that prepared by thermal CVD. 相似文献
16.
An atmospheric non-thermal plasma jet was developed for sterilizing the Staphylococcus aureus (S. aureus). The plasma jet was generated by dielectric barrier discharge (DBD), which was characterized by electrical and optical diagnostics. The survival curves of the bacteria showed that the plasma jet could effectively inactivate 10 6 cells of S. aureus within 120 seconds and the sterilizing efficiency depended critically on the discharge parameter of the applied voltage. It was further confirmed by scanning electron microscopy (SEM) that the cell morphology was seriously damaged by the plasma treatment. The plasma sterilization mechanism of S. aureus was attributed to the active species of OH, N 2 + and O, which were generated abundantly in the plasma jet and characterized by OES. Our findings suggest a convenient and low-cost way for sterilization and inactivation of bacteria. 相似文献
17.
The Ar atmospheric pressure plasma was found to be an excellent laboratorial source for green aurora emission. However, the characteristic and production mechanism of the green aurora emission of the Ar atmospheric pressure plasma are still not clear. In this work, an Ar plasma in a long glass tube which emits intense green aurora light is investigated. With the long glass tube, it can be concluded that the green aurora emission in the Ar plasma is not owing to the mixture of Ar plasma plume with the surrounding air. It is also found that the green aurora emission often appeared beyond the active electrode when the active electrode is placed at the downstream of the gas flow. The green emission disappears when the traces amount of O2 or N2 (about 0.05%–0.07%) is added to Ar. This is because the O2 molecules deactivate the upper state O(1S), which results in the decrease of the green emission. On the other hand, when N2 is added, Ar metastable atoms are quenched by N2, which results in the decrease of O atoms and eventually leads to the decrease of the green emission intensity. The intensity of the green aurora emission increases when the driving voltage frequency increases from 1 to 10 kHz. More importantly, it is found that the green aurora emission is not affected when a grounded stainless steel needle is in contact with the plasma plume. Thus, the green emission is not driven electrically. All these findings are helpful for the understanding of the physics and its applications of atmospheric pressure plasma jet in space physics, laser physics and other application areas. 相似文献
18.
《等离子体科学和技术》2016,18(5):494-499
An atmospheric-pressure dielectric barrier discharge(DBD) gas-liquid cold plasma was employed to synthesize Cu-doped TiO_2 nanoparticles in an aqueous solution with the assistance of[C_2MIM]BF_4 ionic liquid(IL) and using air as the working gas.The influences of the discharge voltage,IL and the amount of copper nitrite were investigated.X-ray diffraction,N_2adsorption-desorption measurements and UV-Vis spectroscopy were adopted to characterize the samples.The results showed that the specific surface area of TiO_2 was promoted with Cu-doping(from 57.6 m~2·g~(-1) to 106.2 m~2·g~(-1) with 3%Cu-doping),and the content of anatase was increased.Besides,the band gap energy of TiO_2 with Cu-doping decreased according to the UV-Vis spectroscopy test.The 3%Cu-IL-TiO_2 samples showed the highest efficiency in degrading methylene blue(MB) dye solutions under simulated sunlight with an apparent rate constant of 0.0223 min~(-1),which was 1.2 times higher than that of non-doped samples.According to the characterization results,the reasons for the high photocatalytic activity were discussed. 相似文献
19.
Desheng ZHOU 《等离子体科学和技术》2018,20(12):125402-125402
Dielectric barrier discharge has widely used in airflow control, ignition and combustion, and other applications; the influence of airflow on dielectric barrier discharge is of extensive concern. Previous studies demonstrate that the discharge becomes more uniform and the discharge intensity decreases with increasing of airflow velocity. In this study, we adopt a discharge cell construction with upstream and downstream structure and study the discharge states and intensities. The experimental results demonstrate that within a specific range of airflow speed, the upstream discharge intensity is decreased, and the downstream discharge intensity is enhanced. The physical basis for this phenomenon is proposed as follows: Within a pulse interval time, some particles, such as charged and metastable particles produced by the upstream discharge, could be transported to the downstream region. The concentration of particles in the downstream region is increased, and these particles play a pre-ionization role in the downstream discharge, the intensity of the downstream discharge is enhanced. Further, factors such as the pulse frequency and the distance between electrodes are discussed in detail, along with the conditions for enhancing downstream discharge intensity. 相似文献
20.
This work reports the experimental results on the characteristics of radio frequency dielectric barrier N2 /Ar discharges.Depending on the nitrogen content in the feed gas and the input power,the discharge can operate in two diferent modes: a homogeneous glow discharge and a constricted discharge.With increasing input power,the number of discharge columns increases.The discharge columns have starlike structures and exhibit symmetric self-organized arrangement.Optical emission spectroscopy was performed to estimate the plasma temperature.Spatially resolved gas temperature measurements,determined from NO emission rotational spectroscopy were taken across the 4.4 mm gap filled by the discharge.Gas temperature in the middle of the gas gap is lower than that close to the electrodes. 相似文献
