Multiphase Plasma Processes and Environment
The activities of the OR concern the experimental study and the modeling of plasmas for environmental applications, mainly for the treatment of gaseous pollutants in indoor air, by original techniques of controlled energy cost.
The OR continues the studies carried out on the development of process coupling chemistry of degradation in homogeneous phase (plasma) and heterogeneous phase (catalysis at ambient temperature). These experimental studies are coupled with the development of kinetic diagrams allowing the identification of the main degradation pathways of pollutants, both within the plasma and on the surface of the catalyst. In-situ experimental studies of plasma/surface interaction (infrared diffuse reflection technique under plasma environment) allow to feed the models with basic kinetic data. In addition, studies are underway to test metal oxides (ZnO, NiO, Y2O3, Mn2O3, ZrO2, …) deposited by sol-gel on silica beads, in order to explore their catalytic properties for the degradation of volatile organic compounds (VOCs) by plasma/catalysis process. Preliminary results obtained with ZnO showed good efficiency on acetaldehyde degradation compared to the results without plasma.
In parallel, the OR has opened a new field of study since September 2015, which concerns the study of pulsed plasmas in liquids for the synthesis of metal nanoparticles (Ag and Au mainly). In order to master this process, it is essential to understand the physicochemical phenomena at the origin of the elaboration of nanoparticles and thus to correctly describe the energy deposition within the liquid phase and the associated mechanisms. In particular, it is necessary to characterize the electrical and chemical properties of the medium at the different stages of the discharge. Thus the temporal and spatial resolution of the diagnostics is essential. The experimental study of these plasmas, generated with a pulsed high voltage between two point-to-point electrodes immersed in a solution (AgNO3/H2O for example), relies on many optical techniques (time-resolved interferometry in order to map the electric field as a function of the experimental conditions, time-resolved strioscopy to highlight hydrodynamic and thermodynamic phenomena during the initiation and propagation of the discharge, time-resolved nonlinear spectroscopy to study the chemical composition of the medium). The results of these experimental studies will be compared with the characteristics of the nanoparticles synthesized with this process. These studies are conducted in collaboration with various academic laboratories (different departments of ONERA, Institut Pierre Gilles de Gennes, …).