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2012

Articles:

ISIJ INTERNATIONAL, 52(7):1273-1280
2012
ISSN: 0915-1559

Resume: The treatment of liquid metal in gas-stirred ladles has long been identified as the main process responsible for the inclusion cleanness in special steels. Four university teams and three steels developers have combined their efforts through a project, supported by French National Research Agency, in order to improve the understanding of the complex mechanisms involved during the ladle treatment. In this paper, the contribution of the Institut Jean Lamour to this program, that bears the acronym CIREM, is presented. Using a commercial CFD code as a basis, a three-dimensional simulation model is developed that includes the geometry and industrial operating conditions. The hydrodynamics of the turbulent metal/bubbles mixture is well represented along with the coupled mechanisms of transport, aggregation and surface entrapment of inclusions.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

2011

Articles:

Belmonte, T., Gries, T., Cardoso, R. P., Arnoult, G., Kosior, F. and Henrion, G.
PLASMA SOURCES SCIENCE & TECHNOLOGY, 20(2)
2011
ISSN: 0963-0252

Resume: This paper describes several specific aspects of atmospheric plasma deposition carried out with a microwave resonant cavity. Deposition over a wide substrate is first studied. We show that high deposition rates (several hundreds of mu m h(-1)) are due to localization of fluxes on the substrate by convection when slightly turbulent flows are used. Next, we describe possible routes to localize deposition over a nanometre-sized area. Scaling down atmospheric plasma deposition is possible and two strategies to reach nanometre scales are described. Finally, we study self-organization of SiO(2) nanodots deposited by chemical vapour deposition at atmospheric pressure enhanced by an Ar-O(2) micro-afterglow operating at high temperature (>1200 K). When the film being deposited is thin enough (similar to 500 nm) nanodots are obtained and they can be assembled into threads to create patterned surfaces. When the coating becomes thicker (similar to 1 mu m), and for relatively high content in HMDSO, SiO(2) walls forming hexagonal cells are obtained.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Cardoso, R. P., Belmonte, T., Kosior, F., Henrion, G. and Tixhon, E.
THIN SOLID FILMS, 519(13):4177-4185
2011
ISSN: 0040-6090

Mots clefs: Plasma-enhanced chemical vapor deposition; Hexamethyldisiloxane; Microwave assisted chemical vapor deposition; Resonant cavity; Afterglow; Post discharge

Resume: The post-discharge of a microwave resonant cavity working at atmospheric pressure is used to enhance deposition of SiOx thin films from HMDSO by chemical vapor deposition. Maximum static deposition rates are close to 150 mu m h(-1) for low power consumption per unit of coated width (similar to 100 W/cm). Dynamic deposition rates are close to 3.5 nm ms(-1). The distribution of the coating thickness is heterogeneous over an area of 150 x 90 mm(2). The influence of the main parameters of the process is systematically studied to show how the key reactions, i.e. gas phase synthesis of powders and surface deposition, are correlated. (C) 2011 Elsevier B.V. All rights reserved.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Arnoult, G., Belmonte, T., Kosior, F., Dossot, M. and Henrion, G.
JOURNAL OF PHYSICS D-APPLIED PHYSICS, 44(17)
2011

Resume: The origin of organization of nanostructured silica coatings deposited on stainless steel substrates by remote microplasma at atmospheric pressure is investigated. We show by resorting to thermal camera measurements coupled with modelling that deposition, limited to a few seconds in time, occurs at low temperature (similar to below 420 K) although the gas temperature may reach 1400 K. Raman analyses of deposited films with thicknesses below 1 mu m show the presence of oxidized silicon bonded to the metallic surface. The origin of nanodots is explained as follows. Close to the microplasma nozzle, the concentration of oxidizing species and/or the temperature being high enough, a silica thin film is obtained, leading to ceramic-metallic oxide interface that leads to a Volmer-Weber growth mode and to the synthesis of 3D structures over long treatment times. Far from the nozzle, the reactivity decreasing, thin films get a plasma-polymer like behaviour which leads to a Franck-Van der Merwe growth mode and films with a higher density. Other nanostructures, made of hexagonal cells, are observed but remain unexplained.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

2009

Articles:

Cardoso, R. P., Belmonte, T., Noel, C., Kosior, F. and Henrion, G.
JOURNAL OF APPLIED PHYSICS, 105(9)
2009
ISSN: 0021-8979

Resume: Filamentation in an argon plasma is studied using a microwave cavity at atmospheric pressure. We show that the size and gas temperature of the filaments increase with the power absorbed by the plasma. The appearance of an additional filament occurs at specific values of the absorbed power. Each new filament appears with a smaller diameter than that of its parent filament but the sum of the diameters of all filaments evolves linearly with the absorbed power. A secondary filament emerges from a set of microfilaments created by a perturbation of the electric field (a slight increase in the incident power above a threshold value). This perturbation occurs over a larger radius than that of the parent filament. By resorting to modeling, we found that the filamentation process involves either a decrease in the effective frequency for momentum-transfer collisions, i.e., a lower electron temperature, or an increase in the electron density. We could show that a small change in the relative positions occupied by two filaments in the microwave cavity requires a strong variation in the electron temperature. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3125525]

Equipe: Centre de Compétences : ERMIONE informatique et calcul

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