Ion sputtering of cathode surface in a hollow cathode discharge

In this paper, ion sputtering of cathode material in a specific type of glow discharge—hollow cathode discharge (HCD)—is analyzed. To estimate both real sputtering yield and screening effect of the buffer gas, two different methods—combination of experimental and analytical approach (applicable for Ar buffer gas only) and use of Monte Carlo simulations—are used. The latter, which is introduced for the first time here, can be used for any buffer gas. Real sputtering yield S_k is estimated by Monte Carlo simulations for several commercial HCD lamps with Ne buffer gas: Ne-Li (0.046), Ne-As (0.862), Ne-Ca (0.337) and Ne-Cd (1.069).     

电池隔膜表面空心阴极等离子体接枝聚合研究

应用自制的空心阴极等离子体装置,引发丙烯酸在丙纶表面的接枝聚合,研究了等离子体接枝聚合作用机理,分析了等离子体接枝聚合各参数(放电功率、气体流量、丙烯酸蒸气流量、样品位置等)对聚合速率的影响。通过红外光谱、扫描电镜等对丙纶接枝聚合膜表面的化学组成和形态结构等进行了表征分析,证明了亲水基团的引入,改善了丙纶隔膜的亲水性能。     

Effect of the electrode material on the atmospheric plasma conversion of NO in air mixtures

Non-thermal atmospheric pressure plasma is widely used for conversion of hazardous gases. Results from different laboratories confirm importance of energy non-equilibrium in the plasma where dominant energy carriers are electrons and a dominant chemistry is based on formation and interactions of radicals. Because of rather high electric fields required for generation and sustaining of air discharges at atmospheric pressure many plasma systems were found rather to create a lot of NO instead of removing it. A widely supported way to clean NO and NO₂ from air mixtures is a plasma assisted catalytic reduction where the cold plasma is combined with the solid-state catalyst. In an ideal case the plasma acts as an oxidation catalyst where an atomic oxygen from air oxidizes NO to NO₂ and the solid-state catalysts are then capable to convert all NO₂ to N₂ and O₂. In most cases it is also necessary to involve auxiliary gases, e.g., propylene, to make the process efficient enough. This work introduces an original cold plasma system based on atmospheric hollow cathodes generated by a nanopulse DC power with controllable voltage and pulse frequency. The system was optimized in both the geometry and the applied power. However, the material of electrodes was found to be the most important factor affecting the plasma performance and consequently the chemical kinetics. A 100% conversion of NO to NO₂ was achieved with a graphite electrode, without using any auxiliary gas and without catalyst. Plasma performance and conversion efficiency are compared for several electrode materials.     

空心阴极等离子体放电结构的优化设计

 低温等离子体表面处理可以有效克服液相处理法存在的环境污染、耗能大和成本高的缺点,对材料表面进行清洗、活化和接枝处理,而设计一个合理的低温等离子体放电结构能够较好地改进表面处理的质量．通过建立CRFHCP空心阴极等离子体放电的数学模型,分析影响低温等离子体放电的关键因素,并设计了不同电极配置方式、样品位置和不同远区空心阴极结构的众多方案．通过接触角测定、表面能计算、SEM照片等方式,对不同方案下处理前后的疏水性PP薄膜形态结构进行表征分析．实验结果发现：远区径向喷嘴式空心阴极等离子体放电结构处理的薄膜表面比其他处理方式具有较小的接触角和较大的表面能．这表明采用优化设计的CRFHCP空心阴极等离子体放电结构,可以较其他结构更为有效地改善材料表面的亲水性能．     

Anwendung der Hohlkatodenplasmaquelle in der Vakuumtechnik

Various effective and simple constructed plasma sources can be developed by using the hollow cathode effect. The improve of the plasma efficiency is caused by the penetration of two or more glow regions of different parts of the cathode. The equatation p × d ∽ 1 mbar cm is a rule of thumb for the appearance of the hollow cathode effect. The hollow cathode arc discharge is caused by an additional thermal electron emission besides the effectes of the hollow cathode glow discharge. All this effects are the reason for the higher degree of ionization for a hollow cathode source in comparison with the most other plasma sources. Application of the hollow cathode glow discharge for surface finish are technics like plasmacleaning, electron beam ablation or gas flow sputtering. Latters are new technics which allow the development of new sources for the coating technology. The application of the hollow cathode are discharge is possible by using the thermal energy generated by the electron beam (electron beam heating, electron beam melting, and electron beam evaporation) and by using the different possibilities of coating technologies whith the hollow cathode arc source (plasma enhanced evaporation, plasma enhanced reactive PVD and plasma CVD).     

Measurement of total energy flux density at a substrate during TiOx thin film deposition by using a plasma jet system

The total energy flux density delivered to an electrically isolated substrate in a low-pressure pulsed DC hollow cathode plasma jet sputtering system during TiO₂ thin film deposition has been quantified. The plasma source was operated in constant average current mode and in a mixture of argon and oxygen or only in pure argon working gas. A titanium nozzle served as the hollow cathode. The total energy flux density measurements were made using a planar calorimeter probe. The main results from the calorimeter probe showed clearly that the total energy flux density at the electrically isolated substrate decreases significantly with duty cycle from 100% (DC mode) to 10% at a given pulsing frequency 2.5 kHz. A local maximum at duty cycle 60% for only pure argon operation has been observed. In addition, the voltage waveforms on the hollow cathode and before the ballast resistor have been saved for pulsed DC measurements for both pure argon and argon + oxygen mixture. A similar transient phenomenon on the cathode voltage and discharge current as observed recently in mid-frequency pulsed DC magnetron discharge has been discovered in the hollow cathode plasma jet sputtering system. We can conclude from these preliminary measurements that the main asset of the pulsed DC hollow cathode plasma jet discharge as distinct from the DC driving of the same plasma system lies in the possibility to reduce or to increase energy influx on the floating substrate within the change of duty cycle.     

Growth of carbon nanofibers and related structures by combined method of plasma enhanced chemical vapor deposition and aerosol synthesis

Growth of carbon nanofibers and nanotubes by combination of aerosol synthesis and plasma-enhanced catalytic chemical vapor deposition with alcohol as carbon precursor is presented. Only a hollow cathode glow discharge (HCGD) is used as gas activation process without any specific heating of the substrate. Specially designed hollow cathode enables the evaporation of catalyst directly on the substrate for catalytic growth. Product of physical vapor deposition process was examined by energy dispersive X-ray spectrometer (EDS). Spectroscopic features of the plasma were monitored by optical emission spectroscopy (OES). Carbon deposition was examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Catalytic nanofibers and multi-walled carbon nanotubes with outer diameters 20-60 nm have been observed.     

Active species characterization in RF remote oxygen plasma using actinometry OES and electrical probes

Actinometry optical emission spectroscopy (AOES), single cylindrical Langmuir probe and electrostatic planar probe were used to investigate the active species (electrons, ions and atomic oxygen) of remote oxygen plasma in an RF (13.56 MHz) hollow cathode discharge system, as a function of applied power and gas pressure. The electron density and electron temperature were determined from Langmuir probe. The atomic oxygen (AO) density was measured using argon actinometry method. Positive ion flux rate was estimated from the positive ion saturation current of the planar probe, and the combination of the planar and Langmuir probes enabled the determination of the negative ion fraction in the discharge. The explanation of the behavior of the different active plasma species was performed on the basis of the main kinetic reactions of oxygen plasma.     

空心阴极光谱法分析铁镍基高温合金杂质

采用ＨＣＤ－Ⅰ型空心阴极光源作为发射光谱的激发光源,以一套Ｋ３镍合金基标准做工艺曲线来分析铁镍基高温合金中的微量杂质元素砷,磅、锑、铅、锡、铊和银。该方法简便快速,并上有较低的检出限,较好的准确度和精密度。     

Characteristics of the nitrided layer formed on AISI 304 austenitic stainless steel by high temperature nitriding assisted hollow cathode discharge

A series of experiments have been conducted on AISI 304 stainless steel using a hollow cathode discharge assisted plasma nitriding apparatus. Specimens were nitrided at high temperatures (520–560 °C) in order to produce nitrogen expanded austenite phase within a short time. The nitrided specimen was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, potentiodynamic polarization and microhardness tester. The corrosion properties of nitrided samples were evaluated using anodic polarization tests in 3.5% NaCl solution. The nitrided layer was shown to consist of nitrogen expanded austenite and possibly a small amount of CrN precipitates and iron nitrides. The results indicated that rapid nitriding assisted hollow cathode discharge not only increased the surface hardness but also improved the corrosion resistance of the untreated substrate.     

Numerical analysis of geometry effects for target re-deposition during low pressure hollow cathode magnetron sputtering

During low pressure ionized metal physical vapor deposition (PVD) of Cu seed layer for microprocessor interconnects, the re-deposited Cu film on the hollow cathode magnetron (HCM) target may fall off and damage the Cu film on the wafer. An analytical view factor model based on the analogy between metal sputtering and diffuse thermal radiation was used to obtain re-deposition profiles for HCM targets in low pressure (below 0.1 Pa) Cu ionized PVD. The model predictions indicate that there is an inherent non-uniformity in the re-deposition profile even for uniform sputtering over the entire HCM target. The predicted re-deposition profile agrees with experimental observations. Subsequent target redesign studies found that the non-uniformity in the re-deposition profile could be mitigated by using a conical sidewall between the top disk and the cylindrical sidewall or reducing the length of the cylindrical sidewall.     

SiOx包装阻隔薄膜的发展现状及其制备方法

SiOx阻隔薄膜具有优异的阻隔性,并且光透过性和微波透过性好,在阻隔包装领域的应用前景广泛,介绍了SiOx包装阻隔薄膜的制备方法:物理气相沉积,等离子体聚合及大气下等离子体聚合等.     

真空空心阴极电弧焊接研究和设备研制

介绍了国内研制的第一台真空空心阴极电弧焊接设备以及钛合金试板焊接工艺试验结果 .结果表明 :采用小孔膜片型空心阴极焊枪能够可靠地实现非接触引弧 ,焊接接头拉伸强度达到QJ1 666-95Ⅰ级接头要求 .     

Cold atmospheric plasma: Sources, processes, and applications

Atmospheric pressure gas discharge plasmas, especially those operated at energy non-equilibrium and low gas temperatures, have recently become a subject of great interest for a wide variety of technologies including surface treatment and thin-film deposition. A driving force for these developments is the avoidance of expensive equipment required for competing vacuum-based plasma technologies. Although there are many applications where non-equilibrium (cold) plasma at atmospheric and higher pressures represents a substantial advantage, there are also a number of applications where low-pressure plasmas simply cannot be replaced due to specific properties and limitations of the atmospheric plasma and related equipment. In this critical review, the primary principles and characteristics of the cold atmospheric plasma and differences from vacuum-based plasma processes are described and discussed to provide a better understanding of the capabilities and limits of emerging atmospheric plasma technologies.     

Simulating effects of gas flow on arc plasma to anode heat transfer during incinerator ash treatment

The conventional method for converting incineration ash to slag employs a plasma type furnace. An analysis of ash melting characteristics was undertaken by changing the inner shield N₂ gas flow rate, assuming a hollow cathode and the ash anode. Results show that heat input intensity characteristics on the ash depend strongly on the gas flow rate through the central hall of the tube cathode arc (TCA). The maximum temperature of the ash surface becomes about 3000-4000 K in a melting state. For a gas flow rate greater than 2 L/min, the shape of the heat input intensity on the ash is annular because of the gas flow. By adjustment of the inner shield gas flow rate, more practical melting of a wider area of the ash can be achieved with the intense annular heat input on the ash.     

内径20mm导向套筒内壁处理(1):空心阴极氩气放电特性研究

针对高端阀门内径20mm导向套内壁处理,采用高频高压脉冲电源,研究了氩气气氛下工作气压、脉冲电压和频率等参数对导向套空心阴极放电伏安特性的影响,并对工件间距及与阳极距离等放电结构进行了研究。结果表明:管内空心阴极放电需要一个稳定过程,脉冲电流随着时间的增加逐步降低,而后达到稳定放电阶段。提高脉冲电压或工作气压,管内空心阴极脉冲峰值电流增加。脉宽或频率的增加,脉冲峰值电流不变,但平均电流增加,且频率的增加使得激励时间减少。放电结构的分析表明,管间距的减少,放电电流变化不大,而管口与阳极之间距离的减少,使得放电峰值电流略有增加。以上研究结果为高端阀门小直径导向套等内壁薄膜制备提供了有效指导。     

Optimization and performance of atmospheric Fused Hollow Cathodes

Experimental results on the atmospheric hollow cathode plasma generation and performance, using a special configuration with tunable wall separations, are presented. The influence of the gas and type of the power used for generation on the optimum size of the cathode slit is investigated. The experimental results are in agreement with the hollow cathode model. The plasma source/plasma reactor design is of utmost importance for control of plasma-chemical kinetics. An example of the atmospheric hollow cathode plasma application for the NO_x conversion is given. The energy consumption and plasma characteristics are discussed.     

Nitriding of zirconium cathode for arc-heater testing in air

Zirconium cathodes with a nitrided surface layer are promising candidates for arc-heater tests in air because of their good erosion resistance and excellent physical properties. Nitriding of a zirconium cathode is performed by a microwave plasma generator. Nitrided cathodes yield a stable plasma flow of argon-air up to 80 A at a maximum flow rate of 4 l/min argon and 0.8 l/min air for a long duration. The specific input power corresponds to 11.8 MJ/kg. During arc-heater testing, nitriding is a governing reaction and golden zirconium nitride is formed at the tip of the cathode surface. The formation mechanism of a ceramic layer during microwave plasma generator treatment and arc-heater testing will also be discussed.     

Hydrogen plasma etching of silicon dioxide in a hollow cathode system

Chemical etching of various materials has been observed when hydrogen plasmas are used in material processing. In the case of the deposition of diamond films the preferential etching of sp² bonded carbon is considered to be of fundamental importance. A few papers have been published which have indicated that etching by hydrogen ions is different to that by hydrogen atoms. In this paper we describe the etching of silicon dioxide by hydrogen which was plasma-activated in a molybdenum-lined RF hollow cathode. The etch rate was seen to be thermally activated but decreased with increasing plasma power. The addition of a few percentage of helium increased the etch rate. The application of a − 50 V bias to the sample holder almost doubled the etch rate indicating the importance of ion bombardment for the chemical reaction. At high plasma powers and substrate temperatures in excess of 450 °C a thin molybdenum deposit was formed on the quartz samples.     

Products on electrodes in an argon-methane magnetically rotating arc at atmospheric pressure

The arc discharge method in a hydrocarbon atmosphere has a promising application in the nanocarbon synthesis field due to its high yield. In this paper, products on electrodes in an argon-methane magnetically rotating arc at atmospheric pressure are investigated. Different nanocarbons are obtained on the cathode and anode surfaces, respectively. Material analysis indicates that the products on the cathode are mainly carbon tubes. Some carbon tubes are well-aligned in one direction, and the others have a coil-like structure. The products on the anode are a mixture of graphene nano-flakes and aggregate hollow carbon particles. The hollow carbon particles exhibit a chain-like structure with internal space to be connected. To the authors’ knowledge, this is possibly the first time that aggregate hollow carbon particles with a chain-like structure have been observed in the absence of any catalyst. Based on the configuration of arc plasma, the formation mechanism of electrode products is briefly proposed.