Prediction of the energy efficiency of an Ar-H2-O2 plasma torch with Ansys Fluent

International audienceThis study aims at modeling an inductively heated Ar-H2-O2 plasma [1]. This plasma produced by a plasma torch is commonly used for the removal of boron from Silicon [2]. Some modules made at SIMAP-EPM enable us to model the plasma specificities and the interaction of the conducting fluid with the electromagnetic field. The power generated by the coil will be partly dissipated with the joule effect in the conductive parts of the device, partly transmitted into the plasma. The energy transmitted into the plasma will be partly used for chemical reactions, partly used to heat the plasma. However the plasma will also transmit some of its energy to the water-cooled walls with the radiative effects. We define the energy efficiency R eff as the fraction of plasma power provided by the torch to the reactor (in the form of an enthalpy flow and radiation flux). This study aims to predict this ratio for a given set of experiments [3]

Croissance de semi-conducteurs à grand gap

La modélisation et la simulation des procédés de croissance tel que le transport physique en phase vapeur (PVT), le dépôt chimique en phase vapeur (CVD ou HTCVD) et les techniques hybrides (CFPVT), sont suffisamment au point pour être utilisées comme des outils de compréhension des phénomènes physiques couplés et comme des outils de conception de nouveaux procédés et d'optimisation de procédés existants. La modélisation des procédés d'élaboration rassemble plusieurs voies physico-chimiques de complexité variable, depuis des études thermodynamiques et/ou cinétiques jusqu'aux transferts simultanés de matière et de chaleur couplées avec les bases de données et propriétés thermodynamiques et/ou cinétiques et de transport. Différentes voies de modélisation sont utilisées, thermodynamiques, cinétique ou transfert de masse, de façon couplée ou découplée, permettant de visualiser l'évolution de la croissance et ainsi comprendre le rôle complexe et fortement couplé des phénomènes

Elaboration de silicium pour l'industrie photovoltaïque.

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Electromagnetic Processing of Materials at SIMaP : focus on Solar Silicon elaboration

International audienceThe metal-matrix-nano-composites (MMNCs) in this study consist of an Al alloy matrix (6061) reinforced with 1.0 wt.% SiC 50 nm diameter nanoparticles that are dispersed within the molten alloy matrix using ultrasonic cavitation (UST) and induction melting technologies. The required ultrasonic parameters to achieve the required cavitation for adequate degassing and refining of the Al alloy as well as the fluid flow characteristics for uniform dispersion of the nanoparticles into the 6061 alloy matrix are being investigated in this study by using an in-house developed magneto-hydro-dynamics (MHD) model. The MHD model accounts for turbulent fluid flow, heat transfer and solidification, electromagnetic field as well as the complex interactions between the solidifying alloy and nanoparticles by using ANSYS Maxwell and ANSYS Fluent Dense Discrete Phase Model (DDPM) and a particle engulfment and pushing (PEP) model. The PEP model accounts for the Brownian motion. The MHD model is coupled with a stochastic microstructure model to predict the formation of the microstructure during the UST and electromagnetic stirring (EM) processing of alloys and nanocomposites. Scanning electron microscope (SEM) analysis was performed on the as-cast MMNC coupons processed via ultrasonic cavitation dispersion technique (UCDS) and confirmed the distribution of the nanoparticles predicted by current model. A parametric study was performed using the validated model. The study includes the effects of electromagnetic field from the induction coils and the magnitude of the fluid flow. The effects of UST on the solidifying microstructure of the A356-based alloys and nanocomposites was also studied experimentally and numerically. Fine globular grain structures (of about 10-20 microns) were observed in the cast samples obtained via UST during solidification. Also, the eutectic microstructure was greatly modified when UST was applied during solidification

E-H mode transition of a high-power inductively coupled plasma torch at atmospheric pressure with a metallic confinement tube.

International audienceInductively coupled plasma torches need high ignition voltages for the E-H mode transition and are therefore difficult to operate. In order to reduce the ignition voltage of an RF plasma torch with a metallic confinement tube the E-H mode transition was studied. A Tesla coil was used to create a spark discharge and the E-H mode transition of the plasma was then filmed using a high-speed camera. The electrical potential of the metallic confinement tube was measured using a high-voltage probe. It was found that an arc between the grounded injector and the metallic confinement tube is maintained by the electric field (E-mode). The transition to H-mode occurred at high magnetic fields when the arc formed a loop. The ignition voltage could be reduced by connecting the metallic confinement tube with a capacitor to the RF generator

Atomic emission spectroscopy method for mixing studies in high power thermal plasmas

International audienceAtomic emission spectrometry was used to measure the distribution of concentration ratios and temperature in thermal plasmas produced by high power torches for process engineering. The spectroscopic method is based on absolute line intensity measurement and Abel inversion. Assuming local thermal equilibrium, the temperature is deduced from the absolute emission of an argon line and the concentration ratio is deduced from the emission ratio of two lines. Using the two dimensions of the camera for spatial and spectral resolution, fast measurements with high resolution can be done. The method has been tested on a 60 kW inductively coupled plasma torch at atmospheric pressure. The results show that the concentration ratios n(O)/n(Ar) and n(H)/n(Ar) can be measured with an accuracy of 25% and that errors due to deviations from LTE are small. Demixing occurs in the induction zone. The application of the method showed that hydrogen diffuses much more than oxygen. The main disadvantage of this method is that, using emission, it does not permit to measure the concentration in the "cold" zones in the center and at the edge of the plasma. (C) 2013 Elsevier B.V. All rights reserve

E–H mode transition of an inductively coupled plasma torch at atmospheric pressure

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