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Articles:

Hamdan, A., Noel, C., Kosior, F., Henrion, G. and Belmonte, T.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 134(2, 1):991-1000 Belmonte, T (Reprint Author), Univ Lorraine, Inst Jean Lamour, UMR CNRS 7198, Parc Saurupt,CS 14234, F-54042 Nancy, France. Hamdan, A.; Noel, C.; Kosior, F.; Henrion, G.; Belmonte, T., Univ Lorraine, Inst Jean Lamour, UMR CNRS 7198, F-54042 Nancy, France.
2013
ISSN: 0001-4966

Resume: The determination of the initial pressure at the bubble wall created by a discharge in heptane for micro-gap conditions cannot be determined straightforwardly by modeling the time-oscillations of the bubble. The resolution of the Gilmore equation gives the same solutions beyond 1 mu s typically for various sets of initial parameters, making impossible the determination of the initial pressure at the bubble wall. Furthermore, the very first instant of the bubble formation is not easily accessible at very short time scales because of the plasma emission. Since the pressure waves propagate in the liquid, it is much easier to gain information on the first instants of the bubble formation by studying the pressure field far from the emission source. Then, it is possible to deduce by modeling what happened at the beginning of the emission of the pressure waves. The proposed solution consists in looking at the oscillations affecting another bubble located at least twice farther from the interelectrode gap than the maximum radius reached by the discharge bubble. The initial plasma pressure can be determined by this method. (C) 2013 Acoustical Society of America.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Hamdan, A., Noel, C., Kosior, F., Henrion, G. and Belmonte, T.
JOURNAL OF APPLIED PHYSICS, 113(4) Belmonte, T (Reprint Author), Univ Lorraine, Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France. Hamdan, A.; Noel, C.; Kosior, F.; Henrion, G.; Belmonte, T., Univ Lorraine, Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France. Noel, C.; Kosior, F.; Henrion, G.; Belmonte, T., Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France.
2013
ISSN: 0021-8979

Resume: Modes of energy dissipation in impacts made on various materials (Al, Cu, Fe, and Si) by discharges in heptane are investigated for micro-gap conditions. Bulk metals and thin films of 300 nm in thickness deposited on silicon wafers are used as samples. Positive high voltage pulses with nanosecond rise times make it possible to isolate a single discharge and to study the way the charge delivered by the power supply is transferred to the larger electrode (the sample) in a pin-to-plate configuration. The diameter of the impacts created by the plasma varies linearly versus the charge raised at a power close to 0.5. However, the exact value of the power depends on the material. We also show how the impact morphologies change with the applied charge. At high charges, the diameters of impacts on thin films behave as those made on silicon. At low charges, they behave as the bulk material. Finally, we show that the energy dissipated in impacts is below a few percent. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4780786]

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Hamdan, Ahmad, Audinot, Jean-Nicolas, Migot-Choux, Sylvie, Noel, Cedric, Kosior, Francis, Henrion, Gerard and Belmonte, Thierry
ADVANCED ENGINEERING MATERIALS, 15(10):885-892 Hamdan, A (Reprint Author), Univ Lorraine, Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France. Hamdan, Ahmad; Migot-Choux, Sylvie; Noel, Cedric; Kosior, Francis; Henrion, Gerard; Belmonte, Thierry, Univ Lorraine, Inst Jean Lamour, CNRS, UMR 7198, F-54042 Nancy, France. Audinot, Jean-Nicolas, Ctr Rech Publ Gabriel Lippmann, SAM Dept, L-4422 Belvaux, Luxembourg.
2013
ISSN: 1438-1656

Resume: Discharges in heptane in pin-to-plate configuration are produced between a platinum wire and a (100)-oriented silicon wafer coated by a carbon nanotube (CNT) carpet. This carpet is used to simulate the behavior of a nanostructured surface in electro-discharge machining (EDM) where small protrusions on the surface could play a similar role. CNTs behave like simple electrical conductors between the discharge and the silicon wafer. They act as if they would focus the current on smaller areas. The average diameter of impacts is about five times smaller if the silicon wafer is coated by a CNT carpet. The underlying silicon surface is heated by the plasma and melts, forming a central spot surrounded by a serrated trailing edge. The current density being about one order of magnitude larger when a CNT carpet is present, the induced magnetic field stirs the molten silicon, creating serrations all around the impact. Hot nanoparticles of carbon coming from the plasma fall and roll randomly on the silicon surface where they create wavy micro-channels. Nanowires that are detached from the surface are covered by nanoparticles of platinum in the plasma and embedded within an amorphous carbon layer deposited on the nanotube. However, these effects can only be observed if the current density is high enough (>approximate to 10A mu m(-2) depending on the material) like in micro-EDM but not in nano-EDM.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Hamdan, A., Audinot, J. -N., Noel, C., Kosior, F., Henrion, G. and Belmonte, T.
APPLIED SURFACE SCIENCE, 274:378-391 Belmonte, T (Reprint Author), Univ Lorraine, Inst Jean Lamour, UMR CNRS 7198, F-54011 Nancy, France. Hamdan, A.; Noel, C.; Kosior, F.; Henrion, G.; Belmonte, T., Univ Lorraine, Inst Jean Lamour, UMR CNRS 7198, F-54011 Nancy, France. Audinot, J. -N., Ctr Rech Publ Gabriel Lippmann, SAM Dept, L-4422 Belvaux, Luxembourg. Noel, C.; Kosior, F.; Henrion, G.; Belmonte, T., CNRS, Inst Jean Lamour, UMR CNRS 7198, F-54011 Nancy, France.
2013
ISSN: 0169-4332

Mots clefs: Microplasma; Plasma in liquids; Plasma-surface interaction; Thin films

Resume: Interaction of discharges in heptane with magnetron-sputtered thin films made of aluminum, copper or iron is studied in a pin-to-plate configuration. The behavior of discharges on thin films can be used to better understand the interaction of discharges with given surfaces and it might also improve the reproducibility of the impacts in order to better control their shape. Single layers and bilayers of metals are characterized after impact by SEM, AFM, micro-EDX and nano-SIMS analyses. Discharges last typically for a few hundreds of nanoseconds and dissipated energies range between 1 and 100 mJ. We show that at low impact energy, copper and aluminum are heated and stretched by surface stress. At intermediate energy, melting occurs, leading to the synthesis of external beads by Marangoni's convection. At high energy, the shape of the impact is defined by the pressure release when the discharge stops. When iron is deposited onto silicon, dewetting is an important mechanism. The columnar structure of the deposit may have two distinct roles. On the one hand, gases trapped in intercolumnar boundaries can produce tiny holes. On the other hand, the shock wave can abrade the outermost and less cohesive part of the film if it is made of columns separated by large porosities. (C) 2013 Elsevier B.V. All rights reserved.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

Hamdan, A., Kosior, F., Noel, C., Henrion, G., Audinot, J-N, Gries, T. and Belmonte, T.
JOURNAL OF APPLIED PHYSICS, 113(21) Belmonte, T (Reprint Author), Univ Lorraine, CNRS, Dept CP2S, Inst Jean Lamour, Parc Saurupt,CS 50840, F-54011 Nancy, France. Hamdan, A.; Kosior, F.; Noel, C.; Henrion, G.; Gries, T.; Belmonte, T., Univ Lorraine, CNRS, Dept CP2S, Inst Jean Lamour, F-54011 Nancy, France. Audinot, J-N, Ctr Rech Publ Gabriel Lippmann, SAM Dept, L-4422 Belvaux, Luxembourg.
2013

Resume: The main processes related to discharges between pin and plate electrodes in hydrocarbon liquid (heptane) are modelled for micro-gap (from 10 to 100 mu m) conditions. When a plasma channel hits the surface, a micro-crater is created. The different phenomena controlling the geometry (shape and dimension) of a single crater are described and included in a theoretical model developed for the specific case of pure aluminium. The influence of the most important parameters affecting the geometry of the crater is discussed. Among them, one finds the pressure exerted by the plasma on the liquid metal. It is found that the distribution of the pressure applied on the liquid pool changes significantly the way the plasma shapes the pool. It is assumed that at high charges, the pressure profile is tilted from the channel axis, leading to the formation of a central protrusion. On the other hand, we demonstrate that Thomson-Marangoni forces play an important role for crater diameters smaller than 5 mu m. Then, the choice of the first derivative of the surface tension with respect to the temperature is a key factor. This effect is strongly related to the way convection displaces matter in the liquid pool. Finally, the quenching step is sufficiently fast to freeze the liquid shape as soon as the plasma vanishes. (C) 2013 AIP Publishing LLC.

Equipe: Centre de Compétences : ERMIONE informatique et calcul

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