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《光谱学与光谱分析》2020,(8)
大气压辉光放电的产生摆脱了真空装置的束缚,且其中富含活性粒子,因此大气压辉光放电在材料表面改性,生物医学,污染物处理等方面都具有良好的应用前景。在其应用研究中,含氧活性粒子如OH自由基和O原子等具有重要作用,但目前关于氧原子浓度随工作气体中氧气含量的变化尚不清楚。利用直流电压激励针-网放电装置,以氩氧混合气体作为工作气体,在去离子水中产生了弥散的大气压等离子体。放电照片显示放电中包含明显的阳极辉区、负辉区以及位于它们之间的正柱区,这些特征区域的存在表明放电处于辉光放电机制。光电测量结果表明,气隙电压和发光信号随时间均是恒定的,即放电是时间连续的无脉冲形式。其中,气隙电压随放电电流的增大先减小而后维持不变,即放电的伏安特性曲线在小电流时具有负斜率,在大电流时处于稳压阶段,因此该水下放电在小电流时为亚辉光放电机制,在大电流时为正常辉光放电机制。通过采集250~900 nm范围内的放电发射光谱,发现谱线主要集中在680~900 nm范围内,这部分光谱由ArⅠ和OⅠ(777.4和844.0 nm)组成。此外,还在波长308 nm处观测到微弱的OH谱线。光谱测量结果发现, ArⅠ(如750.4和763.5 nm)的谱线强度随工作气体中氧气含量的增加而单调地减小。与之不同的是OⅠ的谱线强度随工作气体中氧气含量的增加先增大,在氧气含量为1.5%时达到其最大值,之后随氧气含量的增加而减小。为了分析OⅠ的谱线强度随工作气体中氧气含量的变化关系,通过光线化强度法(777.4 nm/750.4 nm)研究了氧原子浓度随工作气体中氧气含量的变化关系。结果表明氧原子浓度随氧气含量的变化趋势与OⅠ谱线强度的变化趋势一致,即随工作气体中氧气含量的增加表现为先增大后减小,其最大值出现在氧气含量为1.5%时。最后,基于氧原子的产生机制和氧分子对电子的吸附作用对上述实验现象进行了定性的解释。这些研究结果对于大气压辉光放电的应用具有重要意义。 相似文献
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张连珠 《核聚变与等离子体物理》2003,(2)
在氮直流辉光放电等离子体中采用快电子和离子(N+2,N+)混合的蒙特卡罗模型,模拟研究了e+N2→N+ N+N+2e e和N+2+N2→N++N+N2过程中粒子(N+,N)产生率的轴向分布随放电参数(工作气压、放电电压和温度)的变化规律。结果表明:两种离解过程中氮活性粒子(N+,N)的产生率都随气压和电压的增加而增大,随放电气体温度的升高而降低;但N+2-N2离解碰撞主要发生在阴极附近。电压较高时,阴极处的离子N+主要由N+2-N2离解过程产生;电压较低时,N+2-N2离解过程可忽略。中性原子N主要由电子碰撞离解过程产生。 相似文献
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氮直流辉光放电活性粒子(N^+,N)的产生率 总被引:1,自引:1,他引:0
张连珠 《核聚变与等离子体物理》2003,23(2):113-118
在氮直流辉光放电等离子体中采用快电子和离子(N2^ ,N^ )混合的蒙特卡罗模型,模拟研究了e N2→N^ /N N 2和N2^ N2→N^ N N2过程中粒子(N^ ,N)产生率的轴向分布随放电参数(工作气压、放电电压和温度)的变化规律。结果表明:两种离解过程中氮活性粒子(N^ ,N)的产生率都随气压和电压的增加而增大,随放电气体温度的升高而降低;但N2^ —H2离解碰撞主要发生在阴极附近。电压较高时,阴极处的离子N^ 主要由N2^ —N2离解过程产生;电压较低时,N2^ —N2离解过程可忽略。中性原子N主要由电子碰撞离解过程产生。 相似文献
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氧气是石墨电极气体开关中必不可少的组分,用于氧化石墨电极在高温电弧冲击下形成的石墨蒸汽,防止熄弧后石墨蒸汽凝华成固体粉末给开关带来绝缘危害。为提高石墨蒸汽的氧化比例,研究了背景气体组分和氧气浓度对石墨氧化反应的影响,选取3种气体N2,Ar,He作为背景气体,研究不同气氛电弧的氧化反应特征;在传统的类空气气体(80%的N2+20%的O2)的基础上,提高氧气浓度至40%和60%,研究氧气浓度对碳质氧化比例的改善作用。基于不同气体组分的热力学参数和输运系数,通过电弧磁流体动力学计算模型得到开关温度特征,将电弧与电极界面的热流强度作为石墨电极质量损失速率的评估依据。实验结果表明,随着氧气浓度的升高,石墨蒸汽的氧化比例逐步提高,但当氧气浓度高于40%时,存在电弧引燃石墨电极的风险。当氧气浓度恒定20%时,以Ar作为背景气体时石墨电极质量损失速率较小,且碳蒸汽在电弧中氧化更加充分。因此,相比于传统的开关气体介质,将背景气体替换为Ar或将氧气浓度提高至约40%均能提升碳氧反应效率,降低开关中的杂质残余量。 相似文献
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《物理学报》2021,(17)
利用机械剥离和高温减薄方法制备了厚度约为5 nm的GeSe纳米片,并通过设计实验装置测试了GeSe纳米片在不同浓度氧气(O_2)和丁烷(C_4H_(10))气体中的电导性能.结果表明,随着氧气浓度的增加, GeSe纳米片在相同电压下所测得的电流增大,而在丁烷气体中所测得的电流减小.通过第一性原理计算发现,O_2分子从GeSe获得电子.气体浓度越大, P型半导体GeSe主要载流子空穴的浓度也越大,从而电导率增大.当GeSe吸附丁烷气体时,随着丁烷气体浓度的增加,相同电压下电导率减小.其原因可归结为GeSe薄膜器件在加工过程中从空气中吸附了O_2分子,由于薄膜中存在较高密度的Se空位,导致O_2的高密度吸附.从而导致在吸附还原性气体时,丁烷气体易失电子.即电子从丁烷气体分子中转移到GeSe薄膜表面与空穴中和,降低了GeSe薄膜中的载流子空穴浓度,从而降低电导率.本文的研究有助于GeSe纳米片在氧气和丁烷气中的光电器件应用. 相似文献
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采用零维等离子体动力学模型,计算了不同约化场强条件下N2/O2放电等离子体的演化特性.结果表明,平均电子能量与约化场强有着近似的线性关系,在约化场强为100 Td时,平均电子能量约为2.6 eV、最大电子能量达35 eV;约化场强是影响电子能量函数分布的主要因素.气体放电过程结束后,振动激发态氮分子的粒子数浓度不再变化,电子激发态的氮分子、原子和氧原子的粒子数浓度达到一峰值后开始降低;放电结束后的氧原子通过复合反应生成臭氧.约化场强升高,由于低能电子减少的影响,振动激发态氮分子的粒子数浓度降低,当约化场强由50 Td增加75 Td,100 Td时,粒子数浓度由3.83×1011 cm-3降至1.98×1011 cm-3和1.77×1011 cm-3,其他粒子浓度则相应增大.
关键词:
等离子体
约化场强
粒子演化
数值模拟 相似文献
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利用可调谐二极管激光吸收光谱技术对低气压氩气介质阻挡放电等离子体进行诊断,重点考察了Ar亚稳态1s_5和1s_3的数密度和气体温度随放电电压,气压,流量,极板间距,以及随N_2配比的变化情况。实验基于朗伯-比尔(Lambert-Beer)定律,通过计算吸收谱线的吸收峰面积求取Ar亚稳态的数密度,同时对谱线进行Voigt拟合得到多普勒展宽,进而求出气体温度。Ar亚稳态主要由电子碰撞产生,但同时电子也会碰撞亚稳态发生猝灭作用,从而使数密度减少;气体温度则与等离子体的实际功率、电子的状态以及粒子之间的碰撞有关。实验结果表明在本实验条件范围内,Ar亚稳态数密度和气体温度随放电电压和流量的增大都先增大,之后逐渐趋于平缓,但两者随流量的变化幅度都较之随放电电压的小,增长较缓慢。随气压的升高,Ar亚稳态数密度和气体温度先增加并达到一个极大值,而之后逐渐降低。实验数据表明,气压对谱线展宽有较明显的影响作用。适当增大极板间距,Ar亚稳态数密度明显降低,但气体温度却有所升高。N_2的加入对亚稳态有很强的猝灭作用,0.5%的N_2就会使数密度下降50%,但随着N_2浓度的进一步增大,其数密度不再明显降低。 相似文献
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Two theories, explaining the time dependence of the negative corona discharge current in air, are confronted with new experimental results. The influence of the ozone concentration on the discharge current was experimentally confirmed in dry air and in mixtures of nitrogen with oxygen. Assuming that only the dissociative electron attachment to ozone molecule is a process being responsible for a reduction of the electron component in the total mean discharge current, the mean value of the electron attachment rate constant k = (3 - 5.5) × 10?9 cm?3 s?1 was derived from the measured dependence of the discharge current on the ozone concentration. The calculated value of the rate constant k corresponds to the dissociative attachment of electron to ozone molecule via process e + O3 → products (O? or O?2 negative ions). 相似文献
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Nilsson J.O. Eninger J.E. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(1):73-82
The pulsed volume discharge is an alternative for the efficient generation of ozone in compact systems. This paper presents a parameter study of the reactions in this kind of homogeneous discharge by using a numerical model which solves plasma chemical kinetic rate and energy equations. Simulations are performed for 10-9-10-5 s single pulses and oxygen gas density in the range 10<300 K and normalized electric field of 1000 decreased. The maximum concentration is 3% at 10 amagat and 100 K. The results on ozone accumulation in multiple pulse discharges are presented. In contrast to the single pulse case, higher efficiency is achieved at lower gas density. This scaling can be explained by losses due to ion currents 相似文献
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In the present paper, an analytical approach is proposed to determine the radial distributions of electric field, electrons, ion densities and temperature of a DC corona discharge in wire-to-cylinder geometry, using oxygen as feed gas. The current–voltage (CV) characteristic measured in experiments is used as an input in the calculation. The objective of this work is to provide approximated analytical solutions of the corona discharge with low computational cost, which can be useful in different technological applications, such as the generation of ozone or the decomposition of pollutant gases. The predictions of the analytical model are compared with the results obtained from a much more complete numerical simulation. 相似文献
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Planar dielectric barrier discharge (DBD) has been designed for ozone synthesis using oxygen as working gas. Applied voltage,
gas flow rate and gap space between electrodes have been found to be an important parameters affecting ozone concentration.
Electrical characterization of the discharge cell including onset voltage, consumed power, and current voltage wave form have
been studied. A maximum ozone concentration of 29 g/m3 and maximum efficiency of 14g/kWmin have been obtained for the designed system. 相似文献
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大气压液体电极放电在生物医疗、化学降解、环境保护等众多方面具有广泛的应用前景,引起了研究者的关注.本文利用直流电压激励棒-水电极装置,在6 mm气隙间产生了大气压辉光放电.研究发现,随着电流的增大,放电由锥状转变成柱状,且此过程中水面上放电环的直径先增大后减小.利用高速照相机对放电进行研究,发现锥状放电是由单个放电丝旋转形成的.通过测量放电的伏安特性,表明放电处于正常辉光机理.利用光谱学方法,研究了不同电流下的振动温度、转动温度和谱线强度比I_(391.4)/I_(337.1),发现它们均随电流的增加而增大.根据气体放电理论,分析和解释了放电丝的运动机理,并对水面上放电环直径随电流的变化关系进行了解释.这些结果对于大气压液体电极放电的理论研究和实际应用均具有一定参考价值. 相似文献
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The inhibition effect of methylene chloride CH2Cl2, chloroform CHCl3 and carbon tetrachloride CCl4 on the ozone generation process from oxygen by negative corona discharge was experimentally investigated. The experiments were performed in a system of coaxial cylindrical electrodes at total gas pressure of 900 mbar and ambient temperature of gaseous mixtures. The rate of ozone generation as well as ozone concentration apparently decreases with a rising number of substituted chlorine atoms in the methane molecule at constant specific energy consumption dissipated in the discharge and at constant concentration of gaseous impurities in oxygen. In addition to experimental results, the paper presents theoretical considerations aimed at identifying the main process responsible for inhibition of ozone generation. The consumption of considerable fraction of oxygen atoms by CH
x
Cl
y–1 radicals formed in discharge, is likely the most important mechanism responsible for the deleterious effect of such compounds on the efficiency of ozone production. 相似文献
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臭氧作为一种强氧化剂和杀菌剂,在污染物降解,食品加工,杀菌消毒,医疗卫生等方面有着非常广泛的应用。大气压介质阻挡放电是一种极为高效的产生臭氧的方法,利用平行平板介质阻挡放电装置,采用交流高压激励,产生了大气压空气非平衡态等离子体。通过测量其电压和发光信号,发现在电压的正、负半周期均存在着许多随机的放电脉冲,并且其脉宽均在几十到几百纳秒之间,这表明其机制是流光放电。放电的光学发射谱包含氮分子的第二正带系(C 3Π-B 3Π)和第一正带系(B 3П-A 3П),氮分子离子的第一负带系(B 2Σ-X 2Σ),以及氧原子谱线(715.7和799.5 nm)。由于流光放电在紫外区域(200~300 nm)没有明显的发射谱线,但臭氧在此区域存在吸收峰,因此可以利用此区域的紫外吸收光谱测量放电产生的臭氧浓度。吸收光谱法可以有效的监测其臭氧浓度的变化情况,其优势在于操作简单,对实验环境要求低,可在放电条件下使用,并且可以连续监测臭氧浓度变化。基于此,通过Beer-Lambert定律计算了臭氧浓度随实验参数的变化,结果发现随外加电压幅值和驱动频率的增加,臭氧浓度升高。这些结果对于大气压介质阻挡放电的工业应用具有重要价值。 相似文献
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R. A. Akhmedzhanov A. L. Vikharev A. M. Gorbachev O. A. Ivanov A. L. Kolysko 《Technical Physics》1997,42(3):260-268
Results are presented from an investigation of the dynamics of ozone formation in a freely localized discharge generated by
a periodic train of 3-cm nanostructured microwave pulses in oxygen and air at a pressure p=3–30 Torr. Conditions for the efficient generation of ozone in air with the minimum production of nitrogen oxides are demonstrated
experimentally. It is shown that when the microwave pulse repetition frequency is high, heating of the gas and the buildup
of nitrogen oxides in the discharge in air reduce the ozone formation efficiency while under prolonged exposure the ozone
formed initially is destroyed. The energy cost of forming ozone in oxygen and air is determined as a function of the microwave
pulse length and repetition frequency and the gas pressure. The lowest energy cost of forming a single ozone molecule in these
experiments is 16 eV per molecule for a discharge in air and 4 eV per molecule in oxygen. It was observed that circulating
the gas through the discharge zone enhances th ozone formation efficiency. It is shown that there are optimal conditions for
ozone formation as a function of the reduced electric field in the plasma.
Zh. Tekh. Fiz. 67, 9–18 (March 1997) 相似文献
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Jiří Kracík 《Czechoslovak Journal of Physics》1958,8(3):341-347
If a variable periodic or non-periodic electric current passes through a gas discharge there is a certain phase difference between this current and the corresponding voltage on the electrodes. The magnitude of this phase difference is dependent both on the conditions existing inside the discharge and on the external electric circuit. It is obvious that apart from the shape of the tube and the type and pressure of the neutral gas, the behaviour of the discharge will be determined by the concentration and temperature of the electrons and by the following external conditions: the voltage of the source and the character of its dependence, and the stabilising resistance or impedance. In this paper a theoretical study is made of the change in temperature and concentration of electrons at a glow discharge, stabilised by ohmic resistance, as a function of the change in voltage of the source.The author wishes to thank Prof. J. B. Slavík, director of the department of physics of the Electrotechnical Faculty, for making this work possible. 相似文献