常压介质阻挡放电等离子体发射光谱的检测分析

以常压介质阻挡放电等离子体作为研究对象,在常温常压条件下使用介质阻挡放电光谱诊断装置,得到N2第二正系跃迁和Ar原子发射谱线。通过对放电光谱的检测分析,可以察知常压介质阻挡放电等离子体的特性,并可运用同一元素谱线的相对强度来诊断电子激发温度等物理参量,以达到对材料表面改性过程的实时监控,工作的结果对常压介质阻挡放电及其在材料改性的应用中具有重要的意义。     

Influence of ambient gas and its pressure on the laser-induced breakdown spectroscopy and the surface morphology of laser-ablated Cd

The ablation of Cd has been performed by employing Q-switched Nd: YAG 10 ns laser pulses with a central wavelength of 1064 nm for a pulsed energy of 200 mJ under various ambient environments of argon, air and helium. The optical emission spectroscopy of Cd plasma has been studied under different filling pressures of shield gases ranging from 5 torr to 760 torr using LIBS spectrometer system. The effect of different gases and their pressures on the intensity of spectral emission, electron temperature and density of the laser-produced plasma has been investigated. SEM analysis has been performed to investigate the dependence of surface morphological changes of an irradiated target on the nature and pressure of an ambient gas. A strong correlation has revealed the vital role of electron temperature and density of laser-induced plasma for the surface modification of Cd. These results strongly indicate that the nature and pressure of the ambient atmosphere is one of the controlling factors of the plasma characteristics, as well as the factors related to the laser energy absorption for surface modification.     

A study on the antimicrobial efficacy of RF oxygen plasma and neem extract treated cotton fabrics

The paper deals with a thorough investigation on the antimicrobial activity of RF oxygen plasma and Azadirachtin (neem extract) treated cotton fabric. The hydrophilicity of cotton fabric was found to improve when treated with RF oxygen plasma. The process parameters such as electrode gap, time of exposure and oxygen pressure have been varied to study their effect on improving the hydrophilicity of the cotton fabric. The static immersion test has been carried out to assess the hydrophilicity of the oxygen plasma treated samples and the process parameters were optimized based on these test results. The formation of carbonyl group during surface modification in the plasma treated sample was analysed using FTIR studies. The surface morphology has been studied using SEM micrographs.The antimicrobial activity was imparted to the RF oxygen plasma treated samples using methanolic extract of neem leaves containing Azadirachtin. The antimicrobial activity of these samples has been analysed and compared with the activity of the cotton fabric treated with neem extract alone. The investigation reveals that the surface modification due to RF oxygen plasma was found to increase the hydrophilicity and hence the antimicrobial activity of the cotton fabric when treated with Azadirachtin.     

Cold plasma-induced modification of the dyeing properties of poly(ethylene terephthalate) fibers

Surface modification of poly(ethylene terephthalate) (PET) fabrics induced by air radiofrequency (RF) plasma treatment has been investigated systematically as a function of plasma device parameters, to identify the plasma-polymer surface interactions prevailing under different operating conditions and leading to an increased color depth upon dyeing. Some tests have also been performed employing chemically inert argon as a feedstock gas. The dyeing properties of plasma-treated fibers were correlated to their topographical characteristics, determined by AFM analysis, and to their chemical surface composition, determined by XPS analysis, while the plasma-originated UV radiation was found to have no relevant effects in PET surface modification. The relative importance of plasma-induced surface processes, such as etching and grafting of polar species, is discussed in relation to their role in modifying PET dyeing properties.     

常压介质阻挡放电间隙的选择及其在材料表面改性中的应用

使用自制介质阻挡放电装置，分析了常压等离子体放电电流和放电功率与放电间隙的变化关系，提出了“放电临界间隙”的概念，并应用该装置对PBT熔喷非织造布进行表面改性，讨论了放电间隙和放电气体等因素对改性效果的影响．     

脉冲偏压上升沿特性对等离子体浸没离子注入鞘层扩展动力学的影响

等离子体浸没离子注入(PIII)是用于材料表面改性的一种廉价高效、非视线的技术.采用等离子体粒子模型，通过假设电子密度服从Boltzmann分布，求解Poisson方程和Newton方程，跟踪离子在等离子体鞘层中的运动形态及特性并进行统计分析，研究了不同上升速率和形状的6种波形上升沿对鞘层时空演化、离子注入能量和剂量的影响.结果表明，在PIII过程中，脉冲上升沿影响了等离子体鞘层的扩展，且不同波形诱导的鞘层厚度间存在最大差值.电场强度在鞘层的外边缘区域存在陡降区，离子的运动为非匀加速过程.可以通过调整脉冲 关键词： 等离子体浸没离子注入 鞘层 粒子模型 上升沿     

Surface modification of medical PVC by remote oxygen plasma

Surface modification of medical PVC by remote oxygen plasma has been studied: surface structure and performance of treated material are analyzed by weight loss rate, contact angle measurement and XPS. With the increase of sample distance from the plasma source, weight loss rate drops, electrons and ions and etching action are restrained; and C=O groups are found in the treated PVC surface. The surface wettability of PVC film can be improved by remote low-temperature plasma and the radical reaction is intensified.     

常压介质阻挡放电等离子体发射光谱诊断及其在材料表面改性中的应用

使用介质阻挡放电光谱诊断装置,分析了常压等离子体放电电流与放电间隙的变化关系,提出了“放电临界间隙”的概念,记录和比较了空气和氩气常压介质阻挡放电等离子体发射光谱,并运用同一元素谱线的相对强度来诊断电子温度等物理参量,以达到对材料表面改性过程的实时监控。工作的结果对常压介质阻挡放电及其在材料改性中的应用具有重要的意义。     

Influence of electron saturation of Tamm levels on the field-emission properties of silicon crystals

It has been shown that the plasma-chemical modification of the morphology and composition of the surface phase influences the emissivity of silicon crystals. It has been found that the saturation of Tamm states with electrons during the preparation of atomically clean silicon surfaces, along with stabilizing passivation of surface atoms in a highly ionized microwave plasma using Halon 14, decreases a threshold electric field at which field emission begins more than twofold and increases the maximal density of the field emission current by more than an order of magnitude compared with wafers covered by native oxide or subjected to ion physical etching in argon. Physicochemical mechanisms responsible for the modification of the silicon surface and the field-emission properties of silicon have been considered.     

Laser-Induced Phase Transition in a Monolayer of Polymer Particles Levitating in a Low-Pressure Gas-Discharge Plasma

We report on the results of analysis of the mean kinetic energy and the pair correlation function of polymer particles in a plasma–dust structure under the action of laser radiation. We have observed experimentally the crystal–liquid phase transition in the monolayer of particles levitating in the near-electrode layer of a capacitive high-frequency discharge. The coupling parameter of the dust system has been estimated. The results of analysis of the modification of the polymer dust particle surface after holding in the plasma are considered. We propose an explanation of the phase transition taking into account the role of the photophoretic force in the motion of macroparticles. The effect of the photophoretic force is associated with the modification of the dust particle surface in the plasma, as a result of which the particles can effectively absorb laser radiation.     

Surface modification of polyimide films using unipolar nanosecond-pulse DBD in atmospheric air

DBD-induced surface modification is very versatile to increase the adhesion or hydrophilicity of polymer films. In this paper, the DBD is produced by repetitive unipolar nanosecond pulses with a rise time of 15 ns and a full width at half maximum of about 30 ns. The power densities of the homogeneous and filamentary DBDs during plasma treatment are 158 and 192 mW/m², respectively, which are significantly less than that using ac DBD processing, and the corresponding plasma dose is also mild compared to AC DBD treatment. Surface treatment of polyimide films using the homogeneous and filamentary DBDs is studied and compared. The change of chemical and physical modification of the surface before and after plasma processing has been evaluated. It can be found that both surface morphology and chemical composition are modified, and the modification includes the rise of hydrophilicity, surface oxidation and the enhancement of surface roughness. Furthermore, the homogeneous DBD is more effective for surface processing than the filamentary DBD, which can be attributed to the fact that the homogeneous DBD can modify the surface more uniformly and introduce more polar functional groups.     

常压射流等离子体发射光谱研究

使用改进介质阻挡放电装置生成常压射流等离子体,采用光纤光栅光谱仪在300～1 000 nm范围记录了不同放电电压的氩气发射光谱,并比较了空气和氩气常压介质阻挡放电等离子体发射光谱,分析发现氩气发射光谱中的谱线都是氩原子的发射谱线,表明常压射流装置产生的等离子体全部为氩等离子体,而无其他空气成分参与放电。为测量电子激发温度,选用相距较近的763.51和772.42 nm两条光谱线对电子温度进行分析,结果表明电子激发温度的范围在0.1～0.3 eV,而且它还随着放电电压的增加而增加。初步使用“红外测温仪”测量被处理材料表面温度,结果发现材料表面的温度也随着放电电压的增加而增加,范围在50～100 ℃,材料表面温度的变化趋势可以近似表征等离子体宏观温度变化趋势。通过分析常压射流等离子体的温度特性,探讨了常压射流等离子体温度对材料改性研究的意义。     

Surface modification of a granular activated carbon by dielectric barrier discharge plasma and its effects on pentachlorophenol adsorption

The surface properties of a granular activated carbon (GAC) were modified by dielectric barrier discharge (DBD) plasma to enhance its adsorption capacity to pentachlorophenol (PCP). Surface characteristics and adsorption capacity of GAC before and after DBD plasma modification were investigated. Results showed that the surface of GAC after plasma modification, especially N₂ plasma, became smoother and the particulates on virgin GAC's surface were eliminated due to deposit effect of plasma. The N₂ plasma modification reduced the specific surface area and surface oxygen-containing functional groups of GAC. In contrast, O₂ plasma modification increased the specific surface area and introduced oxygen-containing groups.     

Investigation on the effect of RF air plasma and neem leaf extract treatment on the surface modification and antimicrobial activity of cotton fabric

A thorough investigation on the antimicrobial activity of RF air plasma and azadirachtin (neem leaf extract) treated cotton fabric has been dealt with in this paper. The cotton fabric was given a RF air plasma treatment to improve its hydrophilicity. The process parameters such as electrode gap, time of exposure and RF power have been varied to study their effect in improving the hydrophilicity of the cotton fabric and they were optimized based on the static immersion test results. The neem leaf extract (azadirachtin) was applied on fabric samples to impart antimicrobial activity. The antimicrobial efficacy of the samples have been analysed and compared with the efficacy of the cotton fabric treated with the antimicrobial finish alone. The investigation reveals that the RF air plasma has modified the surface of the fabric, which in turn increased the antimicrobial activity of the fabric when treated with azadirachtin. The surface modification due to RF air plasma treatment has been analysed by comparing the FTIR spectra of the untreated and plasma treated samples. The molecular interaction between the fabric, azadirachtin and citric acid which was used as a cross linking agent to increase the durability of the antimicrobial finish has also been analysed using FTIR spectra.     

直流辉光放电冷等离子体在高分子材料表面改性上的应用

报道了利用直流辉放光电正柱区产生冷气离子体对高分子材料进行表面改性的工作,阐述了它在纺织材料和非极性塑料制品表面改性上的应用,讨论了高分子材料等离子体表面改性的机理和等离子体参数的选择。     

Hydrogen plasma modification of metal/GaAs interface

GaAs surface modification caused by room-temperature atomic hydrogen treatment in an RF plasma system operated in the reactive ion etching (RIE) mode has been studied by electrical characterization of subsequently fabricated Au/GaAs Schottky barriers. Unlike with reported results for plasma hydrogenation at higher temperatures, the Schottky barrier height on n-GaAs is found to decrease slightly. More interestingly, a pronounced increase in the effective barrier height is seen for p-GaAs. Dopant deactivation close to the surface is also observed for both conductivity types.     

等离子体表面梯度硅沉积对环氧树脂电气性能的影响

环氧树脂作为常见的绝缘材料,在高压直流电场作用下易在其表面积累电荷,发生电场畸变,导致材料绝缘性能下降,影响电力系统运行可靠性。为改善气固界面的电荷特性和绝缘性能,在大气压等离子体射流技术的基础上,对环氧树脂表面进行等离子体梯度硅沉积处理。对改性前后环氧树脂表面理化特性、表面电导率、表面电荷消散和沿面耐压特性进行了多参数测量。实验结果表明,梯度改性对材料表面的物理形貌和化学组分均有明显影响,不同区域的电导率实现了梯度分布,加快了表面电荷消散速度,表面陷阱能级变浅;梯度改性后的样品沿面闪络电压提升幅度可达30.16%。通过等离子体表面梯度硅沉积处理能够改善环氧树脂表面电气性能,在高压直流设备的绝缘设计方面具有广阔的应用前景。     

Modification of the texture of a polymer material surface in dust plasma

We have analyzed the modification of the texture of polymer particle surface in a dust plasma. Monodisperse spherical melamine formaldehyde particles were injected into the glow discharge plasma in neon. At a certain discharge current and gas pressure in the discharge tube, the particles were suspended in dust-plasma traps and experienced the action of the plasma of 5–25 min. Then, the particles were extracted and the collected material was studied using the scanning electron microscope. Among the results, a change in the diameter and roughness of the surface depending on the residence time of particles in the dust plasma was established. It was found that the absolute deviation of all points of the surface profile averaged over the evaluation length were in the nanometer range. The time of complete degradation of particles in the experimental conditions has been established.

     

Insights into sticking of radicals on surfaces for smart plasma nano-processing

In reactive plasma processing, species produced in the plasma reach the surface of a substrate and cause etching, deposition and surface modification through surface reactions. These reactions are characterized by the densities and energies of species incident on the surfaces. In order to realize nano-scale plasma processing, important species for plasma processing have been identified and characterized, and their behavior, not only in the gas phase, but also on the surface, have been clarified and controlled. One of the most critical parameters for insights into surface reaction kinetics of radicals is sticking and surface loss probability. On the basis of radical densities measured by various methods, the sticking and surface reaction loss probabilities have been compiled, and they enable the quantitative understanding of the kinetics of radicals on the surface in the plasma. In this article, the sticking and surface reaction loss probabilities measured thus far are reviewed focusing on fluorocarbon gas, silane gas and methane gas based plasma processes. The establishment of a smart plasma process and the development of an autonomous production device with control of radicals on the basis of insights into the surface reactions for nano-scale plasma processing are presented.     

ADBD plasma surface treatment of PES fabric sheets

Plasma treatment of textile fabrics is investigated as an alternative to the environmentally hazardous wet chemical fabric treatment and pretreatment processes. Plasma treatment usually results in modification of the uppermost atomic layers of a material surface and leaves the bulk characteristics unaffected. It may result in desirable surface modifications, e.g. surface etching, surface activation, cross-linking, chain scission and oxidation. Presented paper contains results of the applicability study of the atmospheric pressure dielectric discharge (ADBD), i.e. dielectric barrier discharge sustaining in air at atmospheric pressure and ambient temperature for synchronous treatment of several sheets of fabric. For tests sheets of polyester fabric were used. Effectivity of the modification process was determined with hydrophilicity measurements evaluated by means of the drop test. Hydrophilicity of individual sheets of fabric has distinctly increased after plasma treatment. Plasma induced surface changes of textiles were also proven by identification of new functional groups at the modified polyester fabric surface. Existence of new functional groups was detected by ESCA scans. For verification of surface changes we also applied high-resolution microphotography. It has shown distinct variation of the textile surface after plasma treatment. Important aspect for practical application of the plasma treatment is the modification effect time-stability, i.e. time stability of acquired surface changes of the fabric. The recovery of hydrophobicity was fastest in first days after treatment, later gradually diminished until reached almost original untreated state.