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International audience; Active ingredients containing fluorinated organic compounds such asFluoroalkylamines or pyrimidine-based molecules are promising in the field of agriculture (pesticides and herbicides) and pharmacology (antibiotics). The massive use of these molecules will result in a massive increase in waste containing this type of molecule. Developed countries have restrictive waste management policies, which is not the case in developing countries. In the latter, we are witnessing a proliferation of storage areas and open-air disposal of waste, sometimes from developed countries. These practices have enormous consequences on the environment such as air, soil and water pollution and therefore on human health. One of the solutions already proven on solid waste would be the use of plasma torches. These torches can reach high temperatures (5,000 K to 20,000 K). However, the use of these means of treatment is not without danger since toxic or lethal molecules could be produced. In order to understand these difficulties, we propose to study the influence of air on the chemical composition of a plasma based on fluoroalkylamines (trifluoroethylamine: C2H4F3N, nonafluoropentylamine: C5H4F9N, etc.), at atmospheric pressure and at atmospheric pressure. local thermodynamic equilibrium (E.T.L), in a temperature range from 500 K to 20,000 K. In order to obtain the chemical composition of the plasma, we use the Gibbs free energy minimization method. The results obtained show that dangerous and toxic gaseous chemical species such as CF2, CO, HCN and HF appear at low temperatures with high concentration.; Les principes actifs contenant des composés organiques fluorés comme les fluoroalkylamines ou les molécules à base de pyrimidine sont prometteurs dans le domaine de l’agriculture (pesticides et herbicides) et de la pharmacologie (antibiotiques). L’utilisation massive de ces molécules aura pour conséquence une augmentation massive de déchets contenant ce type de molécules. Les pays développés ont des politiques contraignantes en matière de gestion de déchets ce qui n’est pas le cas dans les pays en voie de développement. Dans ces derniers, nous assistons à une prolifération des aires de stockage et des éliminations à l’air libre des déchets parfois issus des pays développés. Ces pratiques ont d’énormes conséquences sur l’environnement comme la pollution de l’air, des sols et de l’eau et par conséquent sur la santé humaine. L’une des solutions déjà éprouvé sur des déchets solides serait l’utilisation de torches à plasma. Ces torches peuvent atteindre des températures élevées (5.000 K à 20.000 K). Cependant, l’utilisation de ces moyens de traitement n’est pas sans danger puisque des molécules toxiques ou létales pourraient être produites. Afin d’appréhender ces difficultés, nous proposons d’étudier l’influence de l’air sur la composition chimique d’un plasma à base de fluoroalkylamines (trifluoroéthylamine : C2H4F3N, nonafluoropentylamine : C5H4F9N, …), à la pression atmosphérique et à l’équilibre thermodynamique local (E.T.L), dans une gamme de températures allant de 500 K à 20.000 K. Afin d’obtenir la composition chimique du plasma, nous utilisons la méthode de minimisation de l’énergie libre de Gibbs. Les résultats obtenus montrent que des espèces chimiques gazeuses dangereuses et toxiques comme CF2, CO, HCN et HF apparaissent aux basses températures avec de forte concentration.

International audience; A low pressure recombining Ar plasma to which mixtures of N 2 and O 2 were added has been studied to explore the relevance of surface related processes for the total chemistry. The abundances of the stable molecules N 2, O 2, NO, N 2 O and NO 2 have been measured by means of a combination of infrared tunable diode laser absorption spectroscopy and mass spectrometry. A gas phase chemical kinetics model was developed in chemkin to investigate the contribution of homogeneous interactions to the conversion of the feedstock gases N 2 and O 2. At a partial pressure of N 2 plus O 2 less than 8 Pa, significant discrepancies between measured and calculated concentrations of N 2 O and NO 2 were observed, indicating that heterogeneous processes are dominating the chemistry in this pressure range. At a partial pressure of N 2 plus O 2 higher than 40 Pa and a relatively high fraction of admixed O 2 we observed a fair agreement between measured and calculated concentrations of NO molecules, indicating that homogeneous processes (notably Natom induced) are more dominant than heterogeneous processes.

International audience; A global kinetic model of Cl-2/Ar/N-2 plasma discharge has been developed, which allows calculation of the densities and fluxes of all neutral and charged species considered in the reaction scheme, as well as the electron temperature, as a function of the operating conditions. In this work, the results from the global model are first compared to the calculations given by other models. Our simulation results are focused on the effect of nitrogen adding to the Cl-2/Ar plasma mixture, which impacts both neutral and charged species transport phenomena. The N-2 percentage is varied to the detriment of Cl-2 by keeping the total flow rates of Cl-2 and N-2 constant. In order to better understand the impact of N-2 addition to the Cl-2/Ar gas mixture, the authors analyzed the output plasma parameters calculated from the model for different N-2 flow rate percentages. Indeed, the simulation results show a decrease in electron density and an increase in electron temperature with increasing percentage of N-2. Particular attention is paid to the analysis of electronegativity, Cl-2 and N-2 dissociation, and positive ion to neutral flux ratio evolution by varying percentage of N-2. Such parameters have a direct effect on the etching anisotropy of the materials during the etching process. (C) 2013 American Vacuum Society.

A coaxial double dielectric barrier discharge (DBD) reactor is developed for plasma-catalytic conversion of CH4 and CO2 into syngas and other valuable products. A supported metal catalyst (Ni/Al2O3) reduced in a methane discharge is fully packed into the discharge region. The influence of the Ni/Al2O3 catalyst packed into the gas gap on the electrical characteristics of the discharge is investigated. The introduction of the catalyst pellets leads to a transition in discharge behaviour from a typical filamentary microdischarge to a combination of spatially limited microdischarges and a predominant surface discharge on the catalyst surface. It is also found that the breakdown voltage of the CH4/CO2 discharge significantly decreases when the reduced catalyst is fully packed in the discharge area. Conductive Ni active sites dispersed on the catalyst surface contribute to the expansion of the discharge and enhancement of charge transfer. In addition, plasma-catalytic dry reforming of CH4 is carried out with the reduced Ni/Al2O3 catalyst using a mixing ratio of CH4/CO2 = 1 and a total flow rate of 50 ml min−1. An increase in H2 selectivity is observed compared with dry CH4 reforming with no catalyst, while the H2/CO molar ratio significantly increases from 0.84 to 2.53 when the catalyst is present.

International audience; A systematic investigation into transition metal halides and ~oxides showed the high potential of transition metal oxides as visible radiators for highly efficient gas discharge light sources. Zirconium monoxide (ZrO) has been identified as most promising candidate combining highly attractive green and red emission band systems with very high dissociation energy (8.2eV) which assures that the molecule is stable even in the hot plasma centre. Thus far, however, it has been impossible to keep ZrO in the gas phase of a closed discharge vessel, because at wall temperature usually compounds are formed which have negligible vapour pressures. We succeeded in establishing a regenerative chemical cycle by filling ZrX 4 (X=Cl, Br, I) together with a stable, but volatile oxygen compound (like MoO 2 X 2) and realized thus highly attractive, novel gas discharge light sources. The aim of any lamp engineer is to develop a white light source with good colour rendering properties (Ra 8 > 80) and highest luminous efficacy . Current discharge lamps - emitting mainly atomic radiation - are reaching only about half of the theoretical efficacy limit of 200-230 lm/W. The possible efficacy rise by increasing atomic radiation is limited by self-absorption of the atomic lines (= radiation trapping). This limitation does not apply for molecular radiation, since the molecular emission is distributed over a huge number of molecular transitions which is several orders of magnitude higher than the corresponding number of atomic lines. As a matter of fact, various molecular radiators have been investigated in gas discharges for lighting applications in the course of the last century [ 1-15 ]. Nevertheless there still is no large-scale commercially applied discharge lamp type on the market whose radiation output is dominated by molecular emission. Molecular discharge light sources investigated in the past suffered from serious drawbacks: Severe chemical attack of the wall material, corrosion of the tungsten electrodes and - in most cases - poor plasma efficacy. Therefore, we strive for a breakthrough efficacy improvement by introducing novel molecular radiators for discharge lamps.

International audience; Experiments was carried out to investigate the removals of SO2 and NOx from simulated glass manufacturing industry flue gas containing O2, N2, NO, NO2, CO2, SO2, and H2O using a sub-µs pulsed Dielectric Barrier Discharge (DBD) at atmospheric pressure. Removal efficiencies of SO2 and NOx (NO+NO2) were achieved as a function of gas temperature for two specific energies and two initial NO, NO2, and SO2 concentrations. The higher SO2 and NOx removal efficiencies were achieved in gas stream containing 163 ppm of SO2, 523 ppm of NO, 49 ppm of NO2, 14% of CO2, 8% of O2, 16% of H2O, and N2 as balance. The experimental results were evaluated using the energy cost or W-value (eV/molecule removed). About 100% of SO2 and 36% of NOx were removed at a gas temperature of 100°C with an energy cost of about 45 and 36 eV/molecule removed, respectively. These results indicate that DBD plasmas have the potential to remove SO2 and NOx from gas streams without additives.

Dielectric barrier discharges (DBDs) have been investigated under a wide range of experimental conditions (pulsed and sinusoidal excitation, input energy, frequency, and residence time) to remediate NOx from atmospheric O 2 rich gas streams. In a given reactor under identical gas composition and equivalent energy density deposition, results show that the main parameter which controls the efficiency of the plasma process is the energy deposition mode. For example, in a pulsed DBD processing at energy density deposition of 30 J/L, 25% of NOx and 40% of C 3 H 6 were converted at 35 mJ/pulse whereas, at 195 mJ/pulse these values were 0% and 15%, respectively. Furthermore, significantly different end products were observed when changing the nature of electrical excitation.

Dielectric barrier discharges (DBDs) are a promising technology for high-intensity sources of specific ultraviolet (UV) and vacuum ultraviolet (VUV) radiation. In this work, the microdischarge dynamics in DBDs for Ne–Xe mixtures under the close conditions of excimer lamp working has been investigated. The computer model including the cathode fall, the positive column and the dielectric is composed of two coupled sub-models. The first submodel describes the electrical properties of the discharge and is based on a fluid, two-moments description of electron and ion transport coupled with Poisson's equation during the discharge pulse. The second submodel, based on three main modules: a plasma chemistry module, a circuit module and a Boltzmann equation module, with source terms deduced from the electric model, describes the time variations of charged and excited species concentrations and the UV photon emission. The use of the present description allows a good resolution near the sheath at high pressure and it predicts correctly the waveform of the discharge behaviour. The effects of operation voltage, dielectric capacitance, gas mixture composition, gas pressure, as well as the secondary electron emission by ion at the cathode on the discharge characteristics and the 173 nm photon generation have been investigated and discussed.