Expansion dynamics of atmospheric pressure helium plasma jet in ambient air

In this work, the expansion dynamics of a helium plasma jet in ambient air is examined. By using a fast imaging technique, the expansion of plasma jet from glass nozzle to air is captured which is in the form of plasma bullet propagating into the air. To understand the plasma bullet travel path from glass nozzle to plasma jet tip a drag force model is used. Moreover, the spatial variation of plasma density along the plasma jet length is estimated using drift velocity, plasma jet current and the cross-sectional area of the plasma jet. It is observed that the slight increase in plasma density is due to the combined effect of reduction of drift velocity, plasma jet current, and jet cross-sectional area. The obtained plasma density from glass nozzle to jet tip is in the range of (0.069-5.96) × 10¹² cm⁻³. The above parameters can be of the essence in biological and industrial applications.     

Indirect plasma inactivation by a low temperature atmospheric pressure plasma (LTAPP) system

The aim of this paper is to evaluate the inactivation effect of indirect low temperature plasma exposure at atmospheric pressure produced by the original Low Temperature Atmospheric Pressure Plasma (LTAPP) system. In this system, the low temperature plasma is generated using a high voltage power supply in oxygen at atmospheric pressure. The obtained survivor curves for Escherichia coli (G⁻), Bacillus subtilis (G⁺), Staphylococcus aureus (G⁺), Candida albicans (Yeast), and Saccharomyces cerevisiae (Yeast) showed that the LTAPP system could inactivate them. The optical microscope images of B. subtilis and S. cerevisiae treated have confirmed the inactivation effect of the LTAPP system.     

气体压强对纳秒激光诱导空气等离子体特性的影响

环境气体的压强对激光诱导等离子体特性有重要影响.基于发射光谱法开展了气体压强对纳秒激光诱导空气等离子体特性影响的研究,探讨了气体压强对空气等离子体发射光谱强度、电子温度和电子密度的影响.实验结果表明,在10-100 kPa空气压强条件下,空气等离子体发射光谱中的线状光谱和连续光谱依赖于气体压强变化,且原子谱线和离子谱线强度随气体压强的变化有明显差别.随着空气压强增大,激光击穿作用区域的空气密度增加,造成激光诱导击穿空气几率升高,从而等离子体辐射光谱强度增大.空气等离子体膨胀区域空气的约束作用,增加了等离子体内粒子间的碰撞几率以及能量交换几率,并且使离子-电子-原子的三体复合几率增加,因此造成原子谱线OⅠ777.2 nm与NⅠ821.6 nm谱线强度随着气体压强增大而增大,在80 kPa时谱线强度最高,随后谱线强度缓慢降低.而离子谱线N Ⅱ 500.5 nm谱线强度在40 kPa时达到最大值,气体压强大于40 kPa后,谱线强度随压强增加而逐渐降低.空气等离子体电子密度均随压强升高而增大,在80 kPa后增长速度变缓.等离子体电子温度在30 kPa时达到最大值,气体压强大于30 kPa后,等离子体电子温度逐渐降低.研究结果可为不同海拔高度的激光诱导空气等离子体特性的研究提供重要实验基础,为今后激光大气传输、大气组成分析提供重要的技术支持.     

Surface cleaning of metal wire by atmospheric pressure plasma

In this study, the possible application of atmospheric pressure dielectric barrier discharge plasma for the annealing of metallic wire is examined and presented. The main purpose of the current study is to examine the surface cleaning effect for a cylindrical object by atmospheric pressure plasma. The experimental setup consists of a gas tank, plasma reactor, and power supply with control panel. The gas assists in the generation of plasma. Copper wire was used as an experimental cylindrical object. This copper wire was irradiated with the plasma, and the cleaning effect was confirmed. The result showed that it is possible to remove the tarnish which exists on the copper wire surface. The experiment reveals that atmospheric pressure plasma is usable for the surface cleaning of metal wire. However, it is necessary to examine the method for preventing oxidization of the copper wire.     

常压双频驱动Ar/CCl4等离子体射流制备碳薄膜的研究

在大气压下双频Ar/CCl4 等离子体射流的驱动下,固定低频功率,通过改变射频功率在硅基底上制备了非晶态碳薄膜,并且通过程序进行相应的数值模拟计算。结果给出了不同功率下电子与离子的密度、温度、电场、电势、角度分布等参数对碳材料样品形貌的影响;样品变化趋势的预测及其原因的分析,以及与实验结果的对比。结果表明,对于双频大气压等离子体,射频可以独立控制等离子体的能量和反应强度,可以相对地控制产物。这为制备薄膜材料的形貌提供重要的实验基础。     

Measurement of optical signals as a plasma propagation in the atmospheric pressure plasma jet columns

The propagation of plasma jets with argon gas is characterized in terms of two factors, the effect of electric field distribution along the tube and the effect of voltage polarity, from the observed results of optical signals along the entire column of plasma. The optical signal of plasma propagates from the high electric-field region of high-voltage electrode toward the low field region of the open air-space, regardless of the polarity of the voltage. The optical intensity and the propagation velocity are higher for the positive voltage than for the negative voltage. Moreover, the length of plasma plume exited from the end of the glass tube into the open air is shorter for the negative voltage. When the optical intensity is strong enough, a secondary peak signal follows the primary peak. In the plasma column on the inside of the glass tube, the optical intensity and the propagation velocity depend on the strength of the electric field; they are both high at the high-field region of voltage terminal and decay toward the end of the tube. The velocity is as fast as 10⁴ m/s at the high-field region and slows down to 10³ m/s at the low-field region of the glass-tube end. However, the plasma accelerates drastically to be (10⁴–10⁵) m/s after exiting the glass tube toward open air, even though the electric field is a quite low and thus the optical signal decays low before fading out. The experimental observations present in this report are explained with the propagation of the plasma diffusion waves.     

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空气中的大气压辉光放电通常因放电易过渡到火花状态而难以产生。在静态大气压空气针-板等离子体发生器中，采用阻容耦合负反馈方法控制等离子体放电发展过程，成功地抑制了辉光放电向火花放电的过渡，产生了稳定的交流辉光放电。研究了电压、电极间距等参数变化对放电的影响。     

纳秒脉冲空气辉光放电等离子体及应用

采用基于半导体断路开关的纳秒脉冲高压电源,在两个金属电极之间产生放电区间为1 600 mm×100 mm×25 mm的常压辉光空气等离子体。等离子体发生器采用负高压针电极阵列与平板阳极结构,针电极的直径为1 mm,长度为20 mm,针电极之间的间隔为20 mm,针电极与平板零电位之间的距离为25 mm,在每个负高压针电极末端周围同时形成圆锥形辉光放电,在平板地电极则形成大面积辉光放电。采用电压探针测量了该新型等离子体的放电特性,结果表明：放电脉冲的上升时间为26 ns,最高脉冲输出峰值电压为27 kV;利用该辉光等离子体对幅宽为1 000 mm聚四氟乙烯薄膜进行了表面改性处理,处理后其表面接触角由原来的124°降到69°,亲水性能大为提高。     

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通过测量大气压介质阻挡放电等离子体辐射信号,建立偶极子辐射模型,利用快速傅立叶变换,计算了大气压介质阻挡放电等离子体中离子速度分布。计算结果表明,速度分布偏离麦克斯韦分布,并且随着放电过程的进行,离子速度及相对离子数进行有规律的变化。     

Photoemission study of fluorination atmospheric pressure plasma processes on EPDM: Influence of the carrier and fluorinating gas

Fluorination plasma treatments at atmospheric pressure were used to modify the surface composition of EPDM elastomer. In this study, two different precursors (CF₄ and SF₆) and two carrier gases (He and Ar) were used for the surface modification of EPDM elastomer. The surface modifications were studied by means of X-ray photoelectron spectroscopy. We have observed a strong influence of the gas selection on the extent of the surface modification induced with these treatments. In general terms, the use of CF₄ generates a higher concentration of fluorine in the elastomer surface. On the other hand, the use of He as carrier gas also increases the effectiveness of the modification process. The fluorine uptake varies between 2 and 13%, although the formation of fluorine-containing functional groups was detected when the amount of fluorine on the surface exceeded 7%. After all treatments, an important oxygen uptake was observed, with amounts three or four times higher than the untreated elastomer.     

大气压介质阻挡射流放电离子速度分布的测量

通过测量大气压介质阻挡放电等离子体辐射信号,建立偶极子辐射模型,利用快速傅立叶变换,计算了大气压介质阻挡放电等离子体中离子速度分布。计算结果表明,速度分布偏离麦克斯韦分布,并且随着放电过程的进行,离子速度及相对离子数进行有规律的变化。     

大气压等离子体针产生空气均匀放电特性研究

大气压空气放电由于脱离了真空装置,易于实现流水线生产,因而在工业上具有广泛的应用. 采用等离子体针装置在空气中产生了稳定的大气压均匀放电. 利用光谱法对等离子体的相关参数进行了空间分辨率测量,并通过光学方法对放电机理进行了研究. 结果表明,等离子体针产生的放电存在电晕放电和等离子体羽放电两种模式. 在稳定的等离子体羽放电模式中,发光分为强光区和弱光区. 弱光区放电的发展速度远大于强光区的发展速度,电子能量和电子密度均是弱光区比强光区大. 对均匀放电的气体温度和振动温度的研究表明,强光区放电遵循汤生击穿机理而弱光区为流光放电. 这些结果对大气压空气放电的工业应用具有重要意义. 关键词： 大气压均匀放电 等离子体针 发射光谱 放电机理     

Modification of surface properties of polyamide 6 films with atmospheric pressure plasma

To investigate the effect of the different plasma gases treatment on the surface modification of atmospheric pressure plasma, polyamide 6 films were treated using pure helium (He), He/O₂ and He/CF₄, respectively. Atomic force microscopy (AFM) showed rougher surface, while X-ray photoelectron spectroscopy (XPS) revealed increased oxygen and fluorine contents after the plasma treatments. The plasma treated samples had lower water contact angles and higher T-peel strength than that of the control. The addition of small amount of O₂ or CF₄ to He plasma increases the effectiveness of the plasma treatment in polymer surface modification in terms of surface roughness, surface hydrophilic groups, etching rate, water contact angle and bonding strength.     

激光雷达测量大气温度的傅里叶分析方法

 在对流层(小于12km），由于大气中气溶胶的存在，传统的利用大气中瑞利散射光谱测量大气温度的方法具有一定的局限性。借助傅里叶分析方法对不同高度的大气后向散射光谱通过碘吸收池所产生的不同透过率曲线进行处理，同时考虑了对流层中气溶胶的影响，可得到对流层中不同高度、不同大气后向散射比条件下的温度轮廓线。     

Cell viability and measurement of reactive species in gas- and liquid-phase exposed by a microwave-excited atmospheric pressure argon plasma jet

A microwave-excited atmospheric pressure plasma jet (ME-APPJ) was generated utilizing coaxial transmission line resonators with the resonance frequency of 788 MHz. We investigated the effects of the operating parameters such as input power and gas flow rate on the electron excitation temperature and electron density using optical emission spectroscopy. The amounts of various reactive species in the plasma-activated media (PAM) exposed by the ME-APPJ were estimated using colorimetric methods. The PAM was applied to A549 cultured cells and subsequently incubated for a given duration. The concentrations of NO₂⁻ and H₂O₂ in the PAM incubating A549 cells were monitored until 24 h. The reduced cell viability rate was observed on A549 cells incubated in the PAM. The concentrations of NO₂⁻ and H₂O₂ and the viability of A549 cells depended on the operating conditions of ME-APPJ. The cell viability rate exhibited a decrease with increasing power and decreasing gas flow rate. Correlation between the concentrations of gaseous reactive species in the plasma and in the PAM and the cell viability is discussed.     

大气压Ar射频容性放电模式转变的温度表征

在大气压条件下Ar气流中实现了容性射频放电α和γ两种模式及其转变与共存.由于放电处于开放大气环境中,放电发射光谱中清晰地存在 N₂C³Π_u→Β³Π_g跃迁产生的第二正带和OH自由基 Α²Σ→Χ²Π跃迁的(0,0)带光谱.为了获得放电区域的宏观温度,针对氮的第二正带(0,1),(1,2)两个谱带,自编了拟合程序,用温度拟合方法获得了氮分子的转动温度和振动温度,研究了转动温度随放电功率的变化趋势,得到了温度突变与放电模式转变的相关性.利用Lifbase的发射光谱模拟功能,进行了OH自由基Α²Σ→Χ²Π(0,0)带光谱的模拟,通过与实验光谱对比,得到了与N₂光谱拟合结果相符的OH转动温度,以及相似的随放电功率的变化趋势,这说明放电空间内的中性物种达到了热平衡状态.根据放电伏安特性变化,放电模式转变对应的转动温度变化趋势得到确认,并且与放电形态的照片符合. 关键词： 大气压等离子体 放电模式 转动温度     

Influence of air pressure on mechanical effect of laser plasma shock wave

The influence of air pressure on mechanical effect of laser plasma shock wave in a vacuum chamber produced by a Nd:YAG laser has been studied. The laser pulses with pulse width of 10ns and pulse energy of about 320mJ at 1.06$\mu $m wavelength is focused on the aluminium target mounted on a ballistic pendulum, and the air pressure in the chamber changes from $2.8\times 10^{3}$ to 1.01$\times $10$^{5 }$Pa. The experimental results show that the impulse coupling coefficient changes as the air pressure and the distance of the target from focus change. The mechanical effects of the plasma shock wave on the target are analysed at different distances from focus and the air pressure.     

Influence of air pressure on the performance of plasma synthetic jet actuator

Plasma synthetic jet actuator(PSJA) has a wide application prospect in the high-speed flow control field for its high jet velocity.In this paper,the influence of the air pressure on the performance of a two-electrode PSJA is investigated by the schlieren method in a large range from 7 k Pa to 100 k Pa.The energy consumed by the PSJA is roughly the same for all the pressure levels.Traces of the precursor shock wave velocity and the jet front velocity vary a lot for different pressures.The precursor shock wave velocity first decreases gradually and then remains at 345 m/s as the air pressure increases.The peak jet front velocity always appears at the first appearance of a jet,and it decreases gradually with the increase of the air pressure.A maximum precursor shock wave velocity of 520 m/s and a maximum jet front velocity of 440 m/s are observed at the pressure of 7 k Pa.The averaged jet velocity in one period ranges from 44 m/s to 54 m/s for all air pressures,and it drops with the rising of the air pressure.High velocities of the precursor shock wave and the jet front indicate that this type of PSJA can still be used to influence the high-speed flow field at 7 k Pa.     

Atmospheric pressure plasma treatment of wool fabric structures

Polyaniline-wool (PAN-WF), poly(3,4-ethylenedioxythiophene)-wool (PEDOT-WF), polypyrrole-wool (PPy-WF) fabrics were successfully prepared via atmospheric pressure plasma process. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR) and four-probe resistance measurements were used to study the properties of the plasma polymer coated wool fabrics. The effects of the addition of iodine doping on the morphology and electrical properties of the fabrics were examined. The lowest electrical resistance was measured to be 7.7 × 10³ Ω cm for PEDOT-I₂-WF sample after washing with water two times.     

激光等离子体温度时间演化特性

用脉冲CO2激光的10.6 μm光束击穿空气产生等离子体,使用光谱仪和ICCD采集等离子体辐射光谱,在局部热力学平衡近似下,利用相对谱线强度法对激光等离子体温度进行了计算。当激光器单脉冲能量为35 J时,选择NⅡ399.5 nm和NⅡ500.5 nm两条线状谱的相对谱线强度计算了不同延迟时间下等离子体温度。实验结果表明:在等离子体的不同位置,等离子体温度均随时间经历了明显的上升到饱和再到下降的过程,等离子体前沿的温度最先达到饱和,距离靶面最近的位置温度达到饱和所需时间最长。