Plasma modification and deposition on inner tube faces by pulsed DC discharges

The modification of inner surfaces of tubes becomes increasingly important in many fluid transport applications. However, long tubes require special plasma techniques for a surface functionalization on the nanometer scale without damaging the bulk. This work focuses on pulsed DC glow discharges in inert argon, reactive oxygen, nitrogen and air plasma as well as polymerizing acetylene plasma revealing strong influences to the wetting behavior by the total duration of the plasma discharge time (plasma on-time). While the investigated polymers polyamide, polycarbonate, polyethylene terephtalate, and thermoplastic polyurethane react very differently on the inert and reactive etching (activation) plasma, the deposition of plasma polymer films (polymer-like carbon with decreasing cross-linking at lower plasma intensity and >50% hydrogen content) suppresses all substrate influences.     

SiO2 thin film deposition on the inner surface of a poly(tetra-fluoroethylene) narrow tube by atmospheric-pressure glow microplasma

SiO₂ thin films were deposited on the inner surfaces of a commercial poly(tetrafluoroethylene) narrow tube with an inner diameter of 0.5 mm using tetraethoxysilane/O₂ feedstock gases and He carrier gas by atmospheric-pressure microplasma-enhanced chemical vapor deposition. A glow microplasma was generated inside the tube by radio frequency (RF) capacitively coupled discharge. X-ray photoelectron spectroscopy spectra showed that the tube inner surface was covered by a SiO₂ thin film. Transparent SiO₂ thin films were obtained with a deposition rate of 230 nm/min at an RF power of 6 W and substrate temperature of 100 °C. The wettability of the SiO₂-coated tube was about 3 times as large as that of an untreated sample tube.     

Improvement in the hydrophilic property of inner surface of polyvinyl chloride tube by DC glow discharge plasma

A DC glow discharge plasma was generated inside polymer tube at low pressure. The polyvinyl chloride (PVC) tube with 4 mm inner diameter and 50 mm length was treated by Ar plasma generated inside the tube. The hydrophilic property of the inner surface of the PVC tube was remarkably improved after the plasma treatment. The water contact angle of the inner surface decreased to 37° from 75° for the untreated sample as the treatment time increase to 30 min. The water contact angle of plasma-treated PVC tube decreases with increasing applied voltage, but increase with increase in working pressure. When the Ar plasma-treated PVC tubes are stored in air at room temperature, the contact-angles of the inner surface quickly increases and finally reaches a plateau value which is still considerably lower than the 75° for the untreated sample.     

等离子体辉光溅射反应复合渗镀合成TiN的研究

本文介绍了一种新的制备TiN的工艺方法.利用辉光放电溅射现象、尖端放电和空心阴极效应,在钢铁材料表面直接复合形成TiN渗镀扩散层.用X射线衍射、辉光放电剥层成分分析仪、显微硬度仪等方法,对复合层进行分析.结果表明:本研究方法复合形成的TiN渗镀层,TiN呈溶质固溶于基体表面层中,呈梯度沿基体向内分布.该表面复合层与一般表面沉积的TiN层不同,是冶金结合扩散层,不会产生剥落现象.在1020 ℃复合形成渗镀层时,层深可达15 μm左右,并得到择优取向为(200)晶面的TiN相,渗镀TiN层的表面硬度随渗镀温度的提高而增加,渗镀TiN层随渗镀温度的升高而增厚.     

真空管道自体溅射镀TiN膜研究

本文详细介绍了长真空管道内表面直流溅射镀TiN膜技术和成膜系统配置。采用真空管道自体真空镀膜方法解决细长管道内表面镀膜问题，特殊的阴极靶结构设计成功地解决了长管道内表面直流溅射镀膜的问题。本实验方法在真空管道内壁获得了均匀的、高品质的TiN膜层，并实现了细长真空管道大面积镀膜过程的稳定性、重复性和一致性。真空管道自体直流溅射镀膜实验中采用的工作原理以及设备简单，操作方便，成本低廉。     

Rotational temperature of oxygen molecules in DC glow discharge in O2-Ar mixtures sustained in discharge tube made from Pyrex glass

The active DC glow discharge sustained in pure O₂ and O₂-Ar mixtures with Ar/O₂ concentration ratios up to 50% has been studied in a Pyrex discharge tube for pressures up to 500 Pa and for discharge currents up to 40 mA. The electric field strength and emission spectra parameters of the discharge were studied by means of the double-probe method and optical emission spectroscopy.The electric field strength was found to increase with the pressure and decrease with the discharge current, which is typical for DC glow discharges. Considering O₂-Ar mixtures, the values of electric field strength decreased with Ar/O₂ ratio.We have focused on the emitted radiation. The rotational temperature T_rot of molecular oxygen was determined from the well-resolved atmospheric A-band at 760 nm. The increase of the rotational temperature with increasing deposited power has been observed for all studied Ar/O₂ ratios. Moreover, it has been found that values of T_rot are independent of the mixture composition.     

Modifying the properties of AISI 316L steel by glow discharge assisted low-temperature nitriding and oxynitriding

Apart from titanium, its alloys and CoCrMo alloys, austenitic steels are widely used in medical applications. In order to improve the frictional wear resistance of these steels, they are subjected to various surface treatments such that the good corrosion resistance of the steels is preserved.The paper analyzes the structure and phase composition of AISI 316L steel after subjecting it to low-temperature nitriding and oxynitriding under glow discharge conditions. The treatments produced diffusion-type surface layers composed of nitrogen-expanded austenite (known as the phase S, i.e. supersaturated solution of nitrogen in austenite) with a thin surface layer of chromium nitride (CrN) zone (after nitriding) or chromium oxide (Cr₂O₃) zone (after oxynitriding). It has been shown that the treatments substantially increase the hardness and frictional wear resistance of the steel without degrading its good corrosion resistance (examined in the Ringer physiological solution at a temperature of 37 °C).     

Study of rotational temperature of oxygen DC glow discharge in Silica and Pyrex discharge tubes

Active DC glow discharges in oxygen have been studied in Silica and Pyrex discharge tubes for medium pressures up to 550 Pa and for discharge currents up to 40 mA. Electric field strength measured by a double-probe technique was found to increase with the pressure and to decrease with the discharge current, which is typical for DC glow discharges. We have focused on the emitted radiation. The rotational temperature (T_rot) of molecular oxygen was determined from the ^PP and ^PQ branches of the well-resolved atmospheric A-band of molecular oxygen at 760 nm. Good agreement between values of T_rot obtained from particular branches was found. The increase of the rotational temperature with increasing pressure and discharge current has been observed in both discharge tubes, however, the values of rotational temperature were systematically higher in the tube made of Pyrex glass. This difference was explained by the particular thermal conductivity of the tube material.     

Effect of various gases and chemical catalysts on phenol degradation pathways by pulsed electrical discharges

The processes of phenol degradation by pulsed electrical discharges were investigated under several kinds of discharge atmospheres (oxygen, argon, nitrogen and ozone) and chemical catalysts (ferrous ion and hydrogen peroxide). The temporal variations of the concentrations of phenol and the intermediate products were monitored by HPLC and GC–MS, respectively. It has been found that the effect of various gases bubbling on phenol degradation rate ranked in the following order: oxygen-containing ozone > oxygen > argon > nitrogen. The high gas bubbling flow rate was beneficial to the removal of phenol. It was found that the degradation proceeded differently when in the presence and absence of catalysts. The phenol removal rate was increased when ferrous ion was added. This considerable enhancement may be due to the Fenton's reaction. What's more, putting the chemical additives hydrogen peroxide into the reactor led to a dramatic increase in phenol degradation rate. The mechanism was due to the direct or indirect photolysis and pyrolysis destruction in plasma channel. Furthermore, the intermediate products were monitored by GC–MS under three degradation conditions. More THBs were generated under degradation conditions without gases bubbling or adding any catalyst, and more DHBs under the condition of adding ferrous ion, and more carboxylic acids under the condition of oxygen-containing ozone gas bubbling. Consequently, three distinct degradation pathways based on different conditions were proposed.     

Engineering the tube size for an inner surface modification by plasma-based ion implantation

In order to apply the inner surface modification of the tube component by plasma-based ion implantation (PBII) technique, the tube size has been characterized by introducing a characteristic parameter - the critical radius of tube (CRT) to optimize the process parameters of a grid-enhanced PBII technique for the nitrogen ion implantation onto the inner surface of an Fe-Cr-Ni stainless steel tube under the process conditions, including the plasma density of central plasma source, the steady pulse voltage, the grid electrode radius, and the processing pressure. The temporal sheath dynamics of the ion matrix sheath on the inner surface of the tube component modified by PBII were demonstrated by the collisional fluid model using the equations of ion continuity and ion motion, Poisson’s equation, and Boltzmann’s relationship of electron to determine the effective range of the process parameters. The optimum process parameters were found by the effect factors of the CRT which was bounded by the two important process parameters, i.e. the ion implantation dose and the processing time, for the engineering practice due to the available dependence on the surface modification effect in suitable costs.     

RF-superimposed DC and pulsed DC sputtering for deposition of transparent conductive oxides

Transparent conductive oxide films are widely used materials for electronic applications such as flat panel displays and solar cells. The superposition of DC and pulsed DC power by a certain fraction of RF power was applied to deposit indium tin oxide films. This technique allows an additional tuning of different parameters relevant to film growth, and yields high quality films even under kinetically limited conditions.A long-term stable RF/DC process could be realized by using different combinations of standard power supply components, which includes a fully reliable arc handling system for both the RF and DC generators. The effectiveness of the arc handling system is illustrated by the current and voltage behavior recorded for actual arcing events. The resistivity of indium tin oxide films is strongly influenced by the respective sputtering mode. The best resistivity values of 145-148 μΩ cm were obtained by RF-superimposed pulsed DC sputtering at a pulse frequency between 100 and 200 kHz and a substrate temperature as low as 140 °C. In addition, the films were extremely smooth with a surface roughness of 1-2.5 nm.     

Experimental and theoretical study of the role of the gas composition and plasma-surface interactions on the SnOx films stoichiometry prepared by DC magnetron reactive sputtering

In this paper, we have studied the tin oxide films deposition by DC magnetron reactive sputtering. We have investigated the discharge parameters such as discharge voltage and deposition rate and the discharge composition as a function of the input oxygen partial pressure. We have compared these results with the deposited films stoichiometry. In the constant current discharge mode, we observe, with increasing oxygen partial pressure, a decrease of the discharge voltage followed by a slight increase, and a drop of the deposition rate. For each experimental conditions, we measure the gas composition by mass spectrometry (glow discharge mass spectrometry mode and residual gas analysis mode (RGA)) and the deposited films stoichiometry by X-ray photoemission spectroscopy. The results are fitted by means of a model, taking into account the plasma-surface interactions. All the data are fitted by the same equation, with only four fitting parameters, namely the sticking-reaction coefficients of O and O₂ on Sn and SnO surfaces. Our results show that the main reaction is the reaction between the atomic oxygen and the metallic part (Sn) of the substrate. This reaction is characterized by a sticking coefficient value (α₁⁰) of 0.96.     

Study on multi-peak behavior of pulsed dielectric barrier discharges in atmospheric-pressure helium

In this work the multi-peak behavior of the dielectric barrier discharge excited by repetitive voltage pulses (pulsed DBD) in atmospheric-pressure helium has been systematically investigated, based on a one-dimensional fluid model. The effects of the parameters of the applied voltage pulse and dielectrics on the multi-peak behavior of the pulsed DBD have been analyzed in detail. The parameters of the applied voltage pulse include voltage growth rate, amplitude, pulse-width, and frequency. The parameters of dielectrics refer to relative permittivity and dielectric thickness. Under the given amplitude of the applied voltage pulse, the number of current pulses presents no monotonic decrease with increasing voltage growth rate, and the dependence of the amplitude of each current pulse on voltage growth rate is different. For a given voltage growth rate, the number of current pulses will increase with increasing applied voltage amplitude, but the amplitude of each current pulse does not vary. In addition, the increase of the pulse-width or the frequency can induce not only later appearance of current pulses and smaller amplitude of the last current pulse at the rising edge of the applied voltage pulse but also larger amplitude of the last current pulse at the falling edge of the applied voltage pulse. Also, the decrease of relative permittivity of the dielectric or the increase of dielectric thickness results in smaller discharge current density and shorter time of charging dielectrics, which may increase the number of current pulses.     

Adhesive properties of polypropylene (PP) and polyethylene terephthalate (PET) film surfaces treated by DC glow discharge plasma

In this study, the adhesive properties of the plasma modified polypropylene (PP) and polyethylene terephthalate (PET) film surfaces have been investigated. Hydrophilicity of these polymer film surfaces was studied by contact angle measurements. The surface energy of the polymer films was calculated from contact angle data using Fowkes method. The chemical composition of the polymer films was analyzed by X-ray photoelectron spectroscopy (XPS). Atomic force microscopy (AFM) was used to study the changes in surface feature of the polymer surfaces due to plasma treatment. The adhesion strength of the plasma modified film was studied by T-peel strength test. The results showed a considerable improvement in surface wettability even for short exposure times. The AFM and XPS analyses showed changes in surface topography and formation of polar groups on the plasma modified PP and PET surfaces. These changes enhanced the adhesive properties of polymer film surfaces.     

Study of rotational temperature of oxygen molecules in H and T forms of DC glow discharge sustained in pure oxygen

The active DC glow discharge sustained in pure oxygen has been studied in a Silica discharge tube by means of optical emission spectroscopy and double-probe diagnostics for pressures 600, 750 and 1000 Pa and for discharge currents up to 40 mA. Two different forms of positive column of the discharge (high-gradient H form and low-gradient T form) were observed. Our investigation was focused on the variations of the rotational temperature T_rot determined from emission spectra of molecular oxygen (atmospheric A-band at 760 nm) in the dependence on the discharge current and on the pressure with respect to the existence of the two forms of the discharge. An increase of the rotational temperature with increasing discharge current has been observed. Moreover, higher values of T_rot were found in the H form compared with the T form.     

Surface modification of materials by dielectric barrier discharge deposition of fluorocarbon films

Dielectric barrier discharges have been used to deposit fluorocarbon (FC) films on various materials, such as paper, glass, and silicon substrates. The primary monomers used for plasma polymerization were difluoromethane (CH₂F₂), octafluoropropane (C₃F₈), and octafluorocyclobutane (C₄F₈). FC films were characterized using Fourier transform infrared spectroscopy, atomic force microscopy, static contact angle measurements, and scanning electron microscopy. Surface and structural properties of deposited films are strongly dependent on the plasma compositions and plasma parameters. FC films deposited on paper are to enhance its barrier properties and to achieve hydrophobic surfaces. Contact angle studies reveal that a minimum FC film thickness of about 200 nm on paper is required to completely cover surface and near-surface fibers, thereby providing the paper with long term hydrophobic character. In the C₃F₈ and C₄F₈ systems, the contact angles of the deposited films do not change appreciably with plasma parameters and are strongly dependent on the substrate roughness. Hydrogenated FC films deposited with CH₂F₂ plasmas show the relatively low contact angles due to the existence of CH_X (x = 1-3) groups.     

Micro-structured electrode arrays: Glow discharges in Ar and N2 at atmospheric pressure using a variable radio frequency generator

Micro-structured electrode (MSE) arrays consist of an interlocked, comb-like, capacitive electrode system with gap widths in the μm range. Large-area uniform glow discharges up to atmospheric pressure were penetrated with our arrays. In order to ignite glow discharges at atmospheric pressure this approach is established next to using dielectric barrier arrays and plasma jets. Because of the industrial, scientific and medical (ISM) limitation of available radio frequencies the usual frequency for experiments is 13.56 MHz. Using a variable radio frequency generator more information about the frequency dependent breakdown mechanisms are gained. The electric parameters of the non-thermal plasma system are characterized by a special probe with an upper frequency detection limit of 60 MHz.     

Synthesis and characterization of cross-linked silicone thin films by pulsed laser ablation deposition (PLAD)

Stable, uniform and cross-linked silicone films have been synthesized by pulsed laser ablation deposition (PLAD) for the first time. A KrF excimer (248 nm) laser was used in the synthesis. The effect of incident energy density on the deposited film chemistry was examined in depth. The surface analysis showed that at low energy densities (100–150 mJ/cm²), smooth, hydrophobic films similar in structure to the starting cross-linked silicone elastomer were obtained. Beyond 200 mJ/cm², hydrophilic films with oxygen contents much higher than the starting polymer were obtained. These films also exhibited a more particulate texture suggesting ablation of particles and/or polymeric clusters from the silicone target. The results demonstrate that the PLAD process may prove valuable for the preparation of cross-linked silicone thin films with tailored properties. Received: 27 June 2001 / Accepted: 17 July 2001     

偏压对活性屏离子渗氮工艺的影响

通过对40C钢进行活性屏离子渗氮处理,研究了在活性屏离子渗氮工艺过程中工件所加的偏压对渗氮层的影响.试验结果表明,在不加偏压或偏压较低的情况下,对距离活性屏较近的工件,其表面有一定厚度的渗氮层形成,硬度提高;而距离活性屏较远的工件,其表面几乎没有渗氮层的形成,但当增大偏压至400～450 V时,工件表面产生弱的辉光放电...     

采用高温氮气氛直流电弧放电法制备大直径碳管

在高温氮气氛以及铁、钴、镍的氧化物混合催化剂作用下,采用直流电弧放电法制备了具有不同形貌特征的外径超过100 nm的大直径碳管(LDCTs).透射电子显微镜(TEM)表征结果表明,LDCTs的外径为90~160 nm,内径为70~150 nm,管壁厚度为9~24 nm.高分辨透射电子显微镜(HRTEM)表征结果表明,LDCT的管壁内层为石墨层结构(平均厚度约为4~7 nm),外层为无定形碳结构(平均厚度约为4 nm),管壁间的隔层亦为石墨层结构.能量色散X射线(EDX)谱图和选区电子衍射(SAED)表征结果表明,LDCTs中掺杂有氮和过渡金属元素.初步探讨了LDCTs的生长机理.