ICMCTF2016 Session TS5: Atmospheric Plasma Applications
Monday, April 25, 2016 1:30 PM in Room Royal Palm 1-3
Time Period MoA Sessions | Abstract Timeline | Topic TS Sessions | Time Periods | Topics | ICMCTF2016 Schedule
TS5-1 Design Approach of Nanomaterials using Plasma Discharge in Solution
SangYul Lee, SungMin Kim (Korea Aerospace University, Republic of Korea); JungWan Kim (Incheon National University, Republic of Korea)
The electrical discharge process in a liquid environment, so called solution plasma process (SPP), is an effective method for the synthesis of metallic nanoparticles and nanofluids, sterilization and decomposition of organic compounds since solution plasma provides strong reaction fields, where active species with highly energetic ions, radicals and electrons react. Especially, SPP for the synthesis of metallic nanoparticles shows the most important advantages such as a short processing time, minimization of chemical uses and the preparation in room temperature and atmospheric pressure In this work, solution plasma process as a design tool for the authentic nanoparticles will be introduced and their applications for different industrial sectors will be illuminated, especially heat transfer application, renewable energy applications, etc.
Special attention will be paid to the synthesis of bimetallic nanoparticles such as Pt/Ag, Pt/Pd, Pt/Cu, and their electrochemical activities by means of hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) for fuel cell applications will be illuminated in detail. Various processing variable in SPP and their effects on electrochemical activities will be presented in detail and future direction for the development of nanoparticles will be suggested.
This study was supported by the National Research Foundation of Korea (NRF) funded by the Korean Government (NRF-2013R1A1A2060918).
TS5-3 Atmospheric Pressure Plasma Reforming of Ethanol
Ladislav Bardos, Hana Barankova (Uppsala University, Sweden)
The plasma source with a coaxial geometry based on the Fused Hollow Cathode (FHC) geometry was used for generation of plasma inside water and the ethanol-water mixtures. The effect of various generation regimes on the performance of plasma, on the hydrogen production efficiency and on the reaction rise-time was examined. A role of the solution temperature, composition of the mixture and current delivered to the discharge are investigated.
TS5-4 Investigation of a Scalable Barrel Atmospheric Plasma Reactor for the Treatment of Polymer Particles
Hisham Abourayana, Peter Dobbyn, Denis Dowling (University College Dublin, Ireland)
Polymer powders find applications in many branches of industry ranging from paint additives to biotechnology (cell supports). Surface properties are of key importance for the performance of the polymer particles. In this study the use of an atmospheric pressure plasma as a processing tool for the alteration of surface properties is investigated. In contrast to flat polymeric substrates or tubes, there have been very few publications on the plasma activation of powders to-date. This study reports on the performance of a novel barrel atmospheric plasma systems for the treatment of powders both at experimental (0.5 g) and lab scale (20 g). The latter system consists of a quartz chamber with dimension of 11 cm long and 10 cm inner diameter. The powder charge was agitated by rotating the glass chamber during treatment at speeds of 7 rotations / minute. The plasma which operates at a frequency of approx. 20 kHz, was generated between two parallel electrodes using a 100 watt power supply. The reactors were used to treat the following polymer particles - Silicone, Polypropylene (PP), Acrylonitrile butadiene styrene (ABS) and Polyethylene terephthalate (PET). These polymer particles had diameters in the range 3-5 mm. The plasma was generated using helium and helium / oxygen gas mixtures. The polymer particle wettability was determined based on water contact angle measurements. Before activation the water contact angle of silicone, PP, ABS and PET are 145°, 100°, 95° and 93° respectively. Using helium only plasma the water contact angle decreased to 106°, 58°, 41° and 34° respectively. No significant decrease in activation was observed for these polymer particles, after further increasing the activation time from 5 to 30 minutes. The effect of addition of oxygen into the He plasma was also investigated. The level of activation was found to be closely linked with the level of oxygen addition. In the case of the silicone particles for example, a contact angles of 5° was obtained after 20 minutes treatment (oxygen flow rate 0.05 slm). In contrast increasing the flow rate of oxygen to 0.125 slm, yielded a decrease in the level of activation, the silicone water contact angle only reduced to 85°. This effect is associated with the partial quenching of the discharge with the addition of higher levels of oxygen and thus decreasing its ability to activate the polymer particles. This quenching was confirmed based on optical emission spectroscopy measurements. In conclusion this study demonstrated the scalability of the barrel plasma system for the activate polymer particles.
TS5-5 Atmospheric Pressure Pulsed Arc Plasma Source (APPAPS) for Deposition of Metallic Coatings
Vasiliki Poenitzsch, Ronghua Wei, Edward Langa, Kent Coulter (Southwest Research Institute, USA)
Metallic or ceramic coatings are commonly deposited using a vacuum process such as a physical vapor deposition (PVD) or a plasma assisted chemical vapor process (PACVD). For some applications, vacuum deposition is impractical as in treating a portion of a large structure such as an aircraft wing or the impeller of a ship. An atmospheric pressure (AP) plasma deposition process becomes very attractive and practical. In this presentation, we will describe an apparatus termed as Atmospheric Pressure Pulsed Arc Plasma Source (APPAPS) and the method for the deposition of metallic or ceramic coatings using the APPAPS. APPAPS is an ambient pressure non-thermal plasma source with power, current, precursor dissociation and flux, ion energy and precursor diversity properties that are comparable with vacuum plasma systems. APPAPS has demonstrated, at proof-of-concept level, the ability to deposit durable coatings at ambient conditions. The design and operation characteristics of the APPAPS will be discussed and preliminary results will be presented.
TS5-6 Comparison of Surface Oxides Formed by Atmospheric Plasma Treatment and Furnace Annealing of Inconel 718 Alloy
Donovan Leonard, Michael Brady (Oak Ridge National Laboratory, USA); Peter Yancey (Atmospheric Plasma Solutions, Inc., USA)
Complex interactions between a downstream atmospheric plasma discharge and metal alloy surfaces can potentially produce beneficial effects related to surface preparation and cleaning, and subsequent properties such as surface adhesion, wear, and corrosion. The plasma treatment results in visual changes (e.g. scattering and interference of light) to surfaces after treatment. This study used advanced materials characterization tools to better understand the morphology, structure, and chemistry of resulting surface structures after an air plasma treatment of a metal surface. An Inconel 718 alloy was chosen as the substrate alloy and resulting surface features from air plasma treatment were compared with surface features formed by standard furnace annealing.
Inconel 718 was subjected to an air atmospheric plasma operating at a power level of 2.5kW for seven seconds at a height of 15mm above the surface which resulted in a multi-colored region on the samples surface that measured ~3mm in diameter. The atmospheric plasma exposure created a thin film on the Inconel 718 surface and FESEM revealed densely packed nodular features measuring 15-40nm in diameter. STEM bright field images showed the nanometer scale nodules to be crystalline and revealed that the atmospheric plasma produced chemically distinct layers on the Inconel 718 surface. Both XPS and EELS showed the top most layer, measuring 45-55nm thick, was rich in nickel and oxygen. Below this first layer was an iron and oxygen rich layer measuring 35-40nm and below this a 15-20nm thick chromium and oxygen rich layer directly above the Inconel 718 substrate. In comparison, the 800 degree centigrade, 1 hour duration furnace annealed sample produced faceted platelet features measuring 300-500nm across on the Inconel 718 surface. XPS and STEM/EDS/EELS showed a surface layer 20-30nm thick rich in iron, chromium and oxygen and a thicker 80-90nm chromium rich oxide at the Inconel 718 substrate.
The chemically distinct oxide layers formed by the air atmospheric plasma were created in seconds and used a fraction of the energy to form a comparably thick oxide than the 1hr long furnace anneal. The atmospheric plasma treated surface exhibited a distinct morphology and chemical composition when compared to the furnace annealed Inconel 718 surface. The use of an air atmospheric plasma may provide a rapid and energy efficient method to grow controllably thin oxide layers on metal substrates.
TS5-7 Tailoring Surface Morphology of Hydroxyapatite-Titania Coatings Produced from Electrolyte-Suspensions by Plasma Electrolytic Oxidation
WingKiu Yeung, Aleksey Yerokhin, Julian Dean, Allan Matthews (University of Sheffield, UK)
Enhancement of biological properties of Ti by surface doping with hydroxyapatite (HA) is of great interest for metal implant applications. This study addresses electrochemical aspects of plasma electrolytic fabrication of thin HA-TiO2 coatings on Ti alloys from electrolyte-suspensions. Methods of cyclic voltammetry are used for identification of voltage/current regions suitable for the PEO process, thus enabling a justified selection of electrical parameters to provide effective coating formation under conditions of controllable breakdown, avoiding development of powerful arcing. Final element modelling is used for time-resolved simulation of potential and current density distributions in the heterogeneous HA-TiO2 surface layer, providing a better understanding of microscopic conditions governing plasma discharge behaviour. The coating morphology is analysed using the Minkowski functionals which provide a new useful tool to identify morphological features and compare coatings with similar surface morphologies.
TS5-8 Atmospheric Plasma Deposition of Transparent and Conductive Films
Siming Dong, Michael Hovich, Reinhold Dauskardt (Stanford University, USA)
Atmospheric plasma deposition is a versatile, low cost and flexible process that enables deposition on large and/or complex shapes in laboratory air and at low temperature. The low temperature plasma and solvent free process allows deposition on, and simultaneous functionalization of plastic substrates in a single step.
Building on our previous studies, we demonstrate a highly efficient deposition method using single and dual precursors to deposit multilayer organosilicate transparent coatings on selected polymer, silicon and glass substrates. The films exhibited ~100% transmittance in the visible wavelength range. FTIR and Raman spectroscopy of the films showed that we are able to control the incorporation of organic components (-C-C-)n in the molecular network despite the oxidizing environment. This incorporation increased the film deposition rate and also resulted in mechanical plasticity in the films. We show how significant increases in the film adhesion with plastics can be achieved from ~2 J/m2 to ~10 J/m2 along with exceptional Young’s modulus ranging from 22GPa to 34GPa. Film structures including composition and thickness to achieve optimized hardness and adhesive properties are reported.We also report on the feasibility of using open air atmospheric plasma to deposit various conductive and antireflective bilayer films on both silicon and plastics. For example, ZnO is an attractive alternative candidate for transparent conducting oxide films and we demonstrate successful deposition under atmospheric conditions at low temperature on polymer substrates. Films with thicknesses of up to 500 nm were successfully deposited on the three polymer substrates. XPS analysis of the films exhibited only peaks associated with Zn and O with an atomic concentration ratio of ~1:1. The film optical and electrical properties varied with deposition conditions. Remarkably high transmittance values above 95% were achieved with a wide range of semi-conducting and conducting electrical properties. We show similar success with blends of TiN/TiO films with transparent and conducting properties. Finally, we discuss our work controlling the refractive index of TaO and TiO films for antireflective coating layers and make comparisons with traditional fabrication techniques in order to assess the viability of a TaOx/SiOy anti-reflection bilayer deposited by open air atmospheric plasma.
TS5-10 Growth of Al2O3/SiO2 Nanocomposite by Plasma Electrolytic Oxidation
Alexandre Nomine (The Open University, UK); Julien Martin, Jaafar Ghanbaja, Thierry Belmonte, Gérard Henrion (Institut Jean Lamour-UMR 7198 CNRS-Université de Lorraine, France)
Plasma Electrolytic Oxidation (PEO) is a promising plasma-assisted surface treatment of light metallic alloys (e.g. Al, Mg, Ti). Although the PEO process makes it possible to grow oxide coatings with interesting corrosion and wear resistant properties, the physical mechanisms of coating growth are not completely understood yet.
Typically, the process consists in immersing the metal work piece in an electrolyte bath and applying a high voltage difference between the work electrode and a counter-electrode. Compared with anodising, the main differences concern the electrolyte composition and the current and voltage ranges which are at least two orders of magnitude higher in PEO. These significant differences in current and voltage imply the dielectric breakdown and consequently the appearance of micro-discharges (MD) on the surface of the sample under processing. Those MD are recognized as being the main contributors to the formation of a dielectric porous crystalline oxide coating.
By using a bipolar pulse current generator, it was shown that a judicious setting of the cathodic half-period parameters (amplitude, duration) with respect to the anodic ones improves strongly the coating compactness and growth kinetics. This regime called “soft regime”  is associated with a quasi-disappearance of MD and a significant voltage drop. The surface of aluminium samples treated in the conditions of “soft regime” exhibits a thin sponge-like glass phase that covers a thick alumina (α and γ-Al2O3) layer.
Transmission electron microscopy (TEM) observations of cross sections showed that the glass phase is composed of amorphous SiO2 with inclusions of sodium. The presence of those elements comes from the electrolyte which is composed of KOH and Na2SiO3.
More surprisingly, we also lighted on that what was previously considered as a dense alumina layer is in fact composed of a stack made alternatively of 80 nm-thick alumina and 10-15 nm-thicksilicasublayers . The formation of such a composite is responsible for the increase in layer compactness and therefore the improvement of mechanical and anticorrosive properties. Two scenarii of growth mechanisms will be discussed, one dealing with single step spinodal transition and one consisting in the formation of porous alumina subsequently filled with silica.
 F. Jaspard-Mécuson, T. Czerwiec, G. Henrion, T. Belmonte, L. Dujardin, A. Viola, J. Beauvir, Surf. Coat. Technol. 201 (2007) 8677