Deposition of SiOx Films from Hexamethyldisiloxane/Oxygen Radiofrequency Glow Discharges: Process Optimization by Plasma Diagnostics

Optical emission and Fourier transform infrared absorption diagnostics have been carried out in hexamethyldisiloxane/oxygen RF discharges for studying the effects of the feed composition and the power on the deposition of SiO₂—like thin films. Ex situ FTIR absorption has been utilized to monitor organic moieties and silanol groups in the film. It is shown that carbon-free films can be obtained by highly diluting the monomer in oxygen, while medium-to-high power is necessary to abate silanol groups. These two conditions represent the optimization criterion to obtain excellent barrier films for food packaging applications.     

Deposition of Super-Hydrophobic and Oleophobic Fluorocarbon Films in Radio Frequency Glow Discharges

Fluorocarbon films using a monomer, 1H, 1H, 2H-perfluoro–1-dodecene were deposited in a continuous radio frequency (RF) glow discharge, the process was carried out in a parallel-plate RF discharge onto stainless steel reactor in order to produce coating with a water-and oil–repellent surface. Fourier-Transform Infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS) revealed that the films obtained contain mainly perfluoromethylene (CF₂) species. Film wettability was tested using water and hydrocarbon liquids for contact angle measurements, furthermore surface energy was also calculated. Oil-repellency was found to increase as the amount of CF₂ species increases in the film structure. Film morphology was studied by Atomic Force Microscopy (AFM), films showing an usual morphology from that typical of Plasma Polymerised Fluorocarbon (PPFC) films. The combination of the low surface energy coating and the surface morphology produces materials which are both water and oil repellency.     

Plasma Reaction Behaviors of Carbon Disulfide and Carbon Dioxide in Glow Discharges

Reaction behaviors of carbon disulfide and carbon dioxide in plasma were investigated and compared. It was found that carbon disulfide is very reactive in plasma to produce dark brown filmy polymers, but carbon dioxide does not give polymeric products at all. The difference in plasma behaviors of the two monomers can be attributed to the roles of sulfur and oxygen in the monomers. There is also some discussion on the spectro-scopic data of carbon disulfide polymers.     

Organic Syntheses in the Plasma of Glow Discharges and Their Preparative Application

It is only during the last few years that reactions of organic substances as a result of electron collisions in the cold plasma of glow and corona discharges have been developed into a preparatively useful method with a wide range of possibilities. Its basic principles and development prospects are discussed in the present progress report on the basis of the research results that are known at present.     

溶剂对等离子体引发的衰减链转移接枝聚合动力学的影响

采用等离子体引发的衰减链转移(DT)接枝聚合法,以丙烯酸(AA)为单体,碘仿为链转移剂,对聚丙烯(PP)薄膜进行表面改性。研究了水和N,N-二甲基甲酰胺(DMF)对等离子体引发聚合及等离子体引发DT聚合动力学的影响。结果表明,采用等离子体引发的方法可以实现DT可控-活性聚合,DMF介质中的可控性优于水介质,等离子体引发DT聚合的溶剂效应明显减弱,接枝量与转化率成正比关系并与FT-IR、接触角的表征结果相符。     

Effects of Cathode and Anode on Deposition of Trimethylsilane in Glow Discharge

DC cathodic polymerization of trimethylsilane (TMS) was carried out in plasma reactors with and without using anode assembly. In DC cathodic polymerization, the TMS plasma polymers are mainly deposited on the cathode (substrate) surface. As a result, fast deposition of TMS plasma polymers was easily achieved in DC cathodic polymerization as compared with AF or RF plasma polymerization. DC cathodic polymerization without using anode assembly has its advantageous features that the size and number of substrates (as cathodes) are not restricted by the size and the location of anode assembly. It was found that the maximum deposition rate on the cathode surfaces was obtained without anode assembly. The DC cathodic polymerization of TMS was conducted also in a large volume reactor with multiple cathodes (substrates). The same deposition mechanisms for DC cathodic polymerization with a single cathode also apply to the multiple cathodes. Uniform deposition on each cathode could be obtained with appropriate spacing of multiple cathodes and by adjusting the operational parameters, which are based on the current density and the system pressure.     

等离子体聚合成膜中的活性粒子模拟分析

针对等离子体聚合成膜实验中的活性粒子的能量及空间分布问题,运用电磁场理论和Ｍｏｎｔｅ Ｃａｒｌｏ方法模拟分析氢、氧、氮直流辉光放电等离子体中的活性粒子的运动,得出其能量分布图和空间密度分布图,并与离子活性能量范围相比较,从而得出结论：在氢、氧等离子体中有足够多的活性离子可以参与和单体分子的物理化学反应,成膜较快;在氮等离子体中,达到活性粒子能量范围的离子相当少,成膜较慢。     

含氮、硫单体等离子体聚合过程中气相组分分析

报导了用ＧＣ－ＭＳ和ＩＲ对含氮，硫单体等离子体聚合过程中气相组分的分析，根据分析结果探讨了该类单体等离子体聚合机理。     

Features of Coating Deposition Inside a Narrow Cavity in Octafluorocyclobutane Discharge Plasma

High Energy Chemistry -     

Effects of Reaction Conditions on the Plasma Polymerization of Ethylene

Abstract

Ehylene can be polymerized at low pressures in a radio-frequency glow discharge. The form of the resulting polymer may be a powder at low pressure (1 to 2 Torr) and low monomer feed rate (10 to 40 cc/min), a colorless film at low pressure and high feed rate (70 to 90 cc/min), or an oil at high pressure (4 to 5 Torr) and high feed rate. The powder and film forms of plasma-polymerized ethylene are insoluble in common organic solvents, indicating a highly cross-linked structure. The oily products, however, are soluble in acetone and xylene. Chemical evidence indicates that the oil is most likely composed of highly branched oligomers of ethylene. Mass spectrometric analysis of the gaseous effluents show that under film-forming conditions the only hydrocarbon species observable are those derived from ethylene. The powder- and oil-forming conditions, on the other hand, yielded oligomeric species. On the basis of this evidence, a mechanism for the plasma-polymerization of ethylene is proposed.     

A Mechanisms and Kinetics Study of Polymeric Thin-Film Deposition in Glow Discharge

Polymeric thin-film deposition in a capacitively coupled rf glow discharge of styrene has been investigated. A kinetic scheme for the polymerization was proposed in which initiation of monomers by electron impact was followed by propagation and termination as in conventional polymerization, the initiation rate constant being a function of electron temperature alone. Four mechanism models were examined, depending on where each reaction step takes place: in the gas phase or on the substrate. Free-radical polymerization was assumed. Experiments were carried out at pressures ranging from 0.25 to 1.05 Torr and at voltages and currents that yielded cold and stable discharges. Substrate temperature was controlled. Deposition rate was determined by weighing. A regression program was used in addition to experimental tests in which substrate temperature was varied. The best approximation to the plasma polymer deposition process was found to be the following model: monomers are activated in the gas phase by electron bombardment and subsequently diffuse to the substrate where they propagate and terminate, adsorption of monomers on the substrate playing an important role. A rate expression relating polymer film deposition rate to the experimental variables is presented.     

Combined Effects of Temperature,Pressure, and Co‐Solvents on the Polymerization Kinetics of Actin

In vivo studies have shown that the cytoskeleton of cells is very sensitive to changes in temperature and pressure. In particular, actin filaments get depolymerized when pressure is increased up to several hundred bars, conditions that are easily encountered in the deep sea. We quantitatively evaluate the effects of temperature, pressure, and osmolytes on the kinetics of the polymerization reaction of actin by high‐pressure stopped‐flow experiments in combination with fluorescence detection and an integrative stochastic simulation of the polymerization process. We show that the compatible osmolyte trimethylamine‐N‐oxide is not only able to compensate for the strongly retarding effect of chaotropic agents, such as urea, on actin polymerization, it is also able to largely offset the deteriorating effect of pressure on actin polymerization, thereby allowing biological cells to better cope with extreme environmental conditions.     

The Polymerization and Oxidation of Pyrrole by Halogens in Organic Solvents

Simultaneous chemical polymerization and oxidation of pyrrole have been initiated by a halogenic electron acceptor, bromine or iodine, in various organic solvents. The polypyrrole (PPY)-halogen charge transfer (CT) complexes obtained from polymerization in acetonitrile are of particular interest. Both the PPY-I₂ and PPY-Br₂ CT complexes are granular in nature and have an electrical conductivity in the order of 1 to 10 ohm^?1 cm^?1. Both complexes show remarkable stability in the atmosphere and in the presence of moisture. The PPY-I₂ and PPY-Br₂ CT complexes in the form of thin, coarse films have also been synthesized on a SnO₂ electrode by electrochemical polymerization in acetonitrile. The physicochemical properties of the PPY-I₂ and PPY-Br₂ CT complexes prepared by the chemical methods are characterized by means of UV-visible and IR absorption spectroscopy, thermal and chemical analysis, and electrical conductivity and density measurements.     

Pulse Plasma Deposition of Terpinen-4-ol: An Insight into Polymerization Mechanism and Enhanced Antibacterial Response of Developed Thin Films

Plasma Chemistry and Plasma Processing - Antifouling/antibacterial coating derived from a sustainable natural resource for biomedical devices have shown promising outcomes, especially in the...     

Study on Generation of Glow Discharge Plasma in Air and Surface Modification of Wool Fabric

Plasma Chemistry and Plasma Processing - A lamellar electrode structure is proposed to achieve the generation of a large-area plasma and the effective processing of the wool fabric with the...     

Atmospheric Pressure Glow Discharges Generated in Contact with Flowing Liquid Cathode: Production of Active Species and Application in Wastewater Purification Processes

Miniaturized atmospheric pressure glow discharges (APGDs) were generated in contact with small sized flowing liquid cathode systems. As anodes a solid pin electrode or a miniature flow Ar microjet were applied. Both discharge systems were operated in the open to air atmosphere. Hydrogen peroxide (H₂O₂) as well as ammonium (NH₄ ⁺), nitrate (NO₃ ^?), and nitrite (NO₂ ^?) ions were quantified in solutions treated by studied discharge systems. Additionally, an increase in the acidification of these solutions was noted in each case. Emission spectra of the near cathode zone of both systems were measured in order to elucidate mechanisms that lead to the formation of active species in gas and liquid phases of the discharge. Additionally, the concentration of active species in the liquid phase (H₂O₂, NH₄ ⁺, NO₃ ^? and NO₂ ^?) was monitored as a function of the solution uptake rate and the flow rate of Ar. The suitability of investigated discharge systems in the water treatment was tested on artificial wastewaters containing an organic dye (methyl red), hardly removable by classical methods non-ionic surfactants (light Triton x-45 and heavy Triton x-405) and very toxic Cr(VI) ions. Preliminary results presented here indicate that both investigated flow-through APGD systems may successfully be applied for the efficient and fast on-line continuous flow chemical degradation of toxic and hazardous organic and inorganic species in wastewater solutions.     

Chemical Vapor Deposition of Silicon Dioxide by Direct-Current Corona Discharges in Dry Air Containing Octamethylcyclotetrasiloxane Vapor: Measurement of the Deposition Rate

Experiments in a positive-polarity, wire/plate electrode establish the effects of the concentration of octamethylcyclotetrasiloxane (150–1100 ppm) and the operating current (0.5–2.55 μA/cm length of wire) on the rate of deposition of silicon dioxide on the high voltage wire. The wire is 100 μm radius tungsten and the wire-to-plate spacing is 1.5 cm. Analyses of the deposit with X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy show that it is amorphous silicon dioxide. The deposition rate increases linearly with increasing silicone concentration and corona current. For the concentrations of silicone likely to present in indoor air, the gas-phase processes limit the rate of deposition.     

Magnetic Field Resonance and Pressure Effects on Epitaxial Thin Film Deposition and In Situ Plasma Diagnostics

This study demonstrated the use of quadrupole mass spectrometry and optical emission spectrometry in diagnosing the plasma in the electron cyclotron resonance chemical vapor deposition (ECRCVD) process. The effects of adjusting the main magnetic coil current and process pressure on chemical composition of the plasma and the characteristics of the epitaxial thin film in the ECRCVD system were investigated. When the main magnetic coil current increased, the deposition rate of thin film increased, with no major effect on thin film crystallization. However, when the process pressure was higher, both the deposition rate and crystallization of epitaxial thin film increased.     

Glow Discharge Plasma Induced Dechlorination and Decomposition of Dichloromethane in an Aqueous Solution

In the present study, efficient dechlorination and decomposition of dichloromethane (DCM) induced by glow discharge plasma (GDP) in contact with an aqueous solution was investigated. Experimental results showed that DCM underwent effective dechlorination and decomposition under the action of GDP. Both the removal and the dechlorination of DCM increased with increasing pH and with the presence of hydroxyl radical scavengers and decreased with quenchers of hydrated electrons. Formic acid and formaldehyde were the major intermediate byproducts. Final products were carbon dioxide and chloride ion. Hydrated electrons were the most important active species responsible for initiation of the reaction. Hydrolysis of the resulting chloromethyl radicals played an important role in mineralization of chlorine atoms of the molecule. Hydroxyl radicals were mainly involved in the oxidation of the intermediate byproducts. Reaction mechanism was proposed based on the dechlorination kinetics and the distribution of intermediate byproducts.