Papers

ICMCTF2006 Session G3: Atmospheric Plasma, Hollow Cathode, and Hybrid Plasma Processing

Thursday, May 4, 2006 1:30 PM in Room Royal Palm 4-6

Thursday Afternoon

Start	Invited?	Item
1:30 PM		G3-1 Dielectric Barrier, Atmospheric Pressure Glow Discharges (DB-APGD): Diagnostics, Modeling and Applications M.R. Wertheimer (Ecole Polytechnique, Canada) "Cold" (non-equilibrium) plasmas at atmospheric pressure (AP) promise economic processing without vacuum systems. Dielectric barrier discharges (DBD) are a particularly attractive subgroup; among these, AP glow discharges (APGD) occur in certain gases with long-lived energetic states, for example nitrogen and the noble gases. They can manifest unique properties, described below, and they have opened application areas as diverse as (a) deposition of novel thin film materials, (b) polymer surface modification, (c) plasma displays, (c) short wavelength light sources, and many others. After a brief overview of recent industrial innovations, fundamental and applied research on DB-APGD in this laboratory is described. The former comprises diagnostic and modeling studies, mostly for the case of helium gas: (i) At low applied a.c. voltage, V, the usual single, multi-microsecond current pulse per half-cycle may comprise many geometrically-ordered plasma columns that ignite and extinguish in perfect synchronism; (ii) at higher V, these merge into the "true" APGD, spread uniformly over the entire electrode area. (iii) Under specific applied voltage and frequency conditions, a "pseudoglow" regime sets in, one comprising multiple pulses per half-cycle. We explain observations (i) to (iii) and demonstrate excellent agreement between measured and theoretically-modeled spatial and temporal discharge evolutions in several electrode geometries; further physical insight comes from spatio-temporally resolved optical emission spectroscopy, including gas temperature measurements. We then turn to applied research in the areas mentioned above: (a) Extremely nitrogen-rich plasma-polymer thin films show great promise in biotechnology, as substrates for tissue engineering applications; (b) surface modification of polymers using nitrogen APGD possesses several advantages over the "conventional" method, namely so-called "corona" discharges.
2:10 PM		G3-3 Surface Functionalization Using Atmospheric Plasma Treatment, Grafting and Coating Technologies A. Yializis, R.E. Ellwanger (Sigma Technologies International Inc.); Rory Wolf (Enercon Industries Corporation) Material surfaces are functionalized for adhesion promotion and other properties using mechanical, wet chemical and ionized gas surface treatments. Atmospheric based ionized gas treatments include corona, flame, and plasma treatment. Atmospheric Plasma Treatment (APT) is a new emerging technology that is finding a variety of applications in industries where value added surface functionality is creating new product opportunities. Atmospheric plasma like vacuum plasma, employs a low temperature process which can induce non-thermally activated surface reactions by the introduction of selected gases which are energized by an electrical field at high frequency. This process is now used to complement the use of corona and flame in promoting adhesion to flexible packaging polyolefin materials such as polypropylene, polyester and polyethylene film webs at commercial speeds. This paper will compare corona, flame and atmospheric plasma ionized gas treatment technologies, with emphasis on their impact on material surface properties. The emergence of atmospheric plasma technology is highlighted as a viable process for economically treating large area substrates. Additional commercial applications of atmospheric plasma are presented, including removal of organic contaminants from foil and glass surfaces and ceramic layer deposition using an Atmospheric Plasma assisted Chemical Vapor Deposition (APCVD) process.
2:50 PM		G3-5 Surface Modification of Polyamide Fibers and Films Using Atmospheric Plasmas D.D. Pappas, E.J. Robinette, W.E. Kosik, J. Hirvonen, J.D. Demaree, R. Jensen, S.H. McKnight (US Army Research Laboratory) High performance polymeric materials provide potential applications as reinforcement fibers for advanced composite systems. In this work, polyamide fibers were treated under atmospheric pressure glow discharges (APGD) and the effects on the morphology and chemistry of the material were studied. The fibers were plasma treated with various gases like N2, O2, Ar, C₂H₂ and He for (30- 120) sec at a frequency of 90 kHz, leading to the functionalization of the surface through the addition of new reactive chemical groups such as "COOH", -OH and -NH₂ and changing the energy, chemical composition and hydrophobicity of the surface. Surface characteristics were examined via contact angle measurements, XPS and SEM. The interfacial strength between polyamide and epoxy matrix was measured using small scale microbond tests as well as larger scale short beam sheer strength tests. Preliminary XPS results show a significant increase in oxygen content and a decrease in the carbon content of the surface. The corresponding changes of the total surface energy were evaluated with a dynamic contact angle analysis system revealing a significant increase that can be mainly attributed to the increase of its polar component. Most importantly, the plasma modified fibers exhibit a stable wetting behavior, even for weeks after being treated, suggesting that it is an ideal technique against aging phenomena.
3:10 PM		G3-6 Hybrid Atmospheric Plasma in Molecular Gas H. Baránková, L. Bardos, D. Söderström (Uppsala University, Sweden) A low gas flow hybrid source combining microwave plasma generated by an antenna and a pulsed hollow cathode plasma generated at the outlet of the antenna was used in an open arrangement in air to produce nitrogen and air plasma columns. Characteristics of the atmospheric plasma columns were examined by optical emission spectroscopy. Emission spectra exhibit nitrogen and oxygen molecular bands and atomic oxygen lines. With increase of pulsed dc power at the hollow cathode metal lines indicate an extended release of the cathode material. Vibrational temperatures of nitrogen molecules were calculated for different regimes of the plasma generation. At the microwave power between 200 and 400 W and at gas flow rates between 100 and 300 sccm the vibrational temperature reached values between 2500 and 6500 K. Corresponding temperatures on thermally insulated steel substrates at the distance of 1 cm from the hollow cathode were between 500 and 800°C. Plasma columns produced by the hybrid source were tested for activation of surfaces and PECVD. Chemical composition and mechanical properties of carbon based solid products deposited by PECVD were characterized with respect to plasma parameters.
3:30 PM		G3-7 Functionalized Nanostructured Coatings Based on Inorganic-Organic Hybrid Systems for Various Industrial Applications R. Phani, M. Passacantando, S. Santucci (University of L’Aquila, Italy) The combination at the nanosize level of inorganic and organic or even bioactive components in a single material makes accessible an immense new area of materials science and engineering that has extraordinary implications for developing novel multi-functional materials exhibiting a wide range of properties. In the present investigation, inorganic-organic polymers synthesized by a two step sol-gel processing method have been applied as thin transparent coatings on various substrates (polymers, metals, ceramics). The curing of the hybrid structures has been performed as low as 500S2°C substrate temperature or by UV radiation. An over view of the developed materials for different applications has been described. These include (i) tunable lasers in the visible range based on perylimide and pyrromethane are embedded in organically modified silicate matrix (ii) non-linear optics and optical switches materials based on CdS nanoparticles are incorporated in the ZrO₂ matrix and (iii) holographic storage, energy-efficient window materials based on vanadium dioxide and doped vandianm dioxide with tungsten and (iv) antistatic and antiadhesive materials based on perfluorinated alkoxysilane compounds. The deposited nanostructured thin films have been characterised for thier structural, compositional, optical, and microstructure has been measured by employing X-ray diffraction, X-ray Photoelectron spectroscopy, UV-visible, atomic force microscopy and high resolution scanning electron microscopy techniques, respectively.
3:50 PM		G3-8 Multi-Arc Fluidized Bed Reactor CVD (MA/FBR-CVD): a New High Throughput Technique for theSurface Treatment and Encapsulation of Particles M. Costa, M. Alvarez, C. Colominas (Universitat Ramon Llull, Spain) A novel high throughput approach to the surface treatment and coating of particles is presented. Electric discharges are generated inside a bed of particles that are fluidized either at atmospheric or reduced pressure. Inert and reactive gas species are fed to the reactor and excited by the electric arcs to promote surface reactions onto the particles. The concept is proved by coating sodium chloride particles in the range of 20-40 microns with silicon dioxide from Tetraethylorthosilicate (TEOS) and oxygen at various pressures, voltages and frequencies. The encapsulated particles were characterized by X-ray diffraction, Scanning Electron Microscopy and some specific dissolution and chemical tests. The silica films were conformal, amorphous and porous, with thicknesses in the micron to the submicron range, and resulted in remarkably slow dissolution kinetics for sodium chloride. Potential applications in the slow release of soluble salts are discussed. Preliminary results in the fabrication of silica micro-shells and nanometer sized plate-like particles are also presented.