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Plasmas for environment
The use of non thermal plasmas for environment corresponds to a large variety of applications. At LPP, resarch studies are carried out on the following subjects
Physics of atmospheric pressure plasmas
Air plasmas at atmospheric pressure are often filamentary. Those filaments correspond to transient phenomena which propagate along few millimeters within few nanoseconds, with diameters in the range of 100 micrometers. At LPP, the development of fluid code on the one hand and in situ diagnostics on the other hand, which are resolved in time to study the plasma jet/surface interaction, allows progress to be made in understanding these complex interactions (see project page).
The valorization of CO2 (Project page)
Reducing CO2 emissions is one of the greatest challenges of today. In addition, the large-scale development of renewable energies (wind, photovoltaic) requires the ability to store this electrical energy in chemical form in order to transport this energy. Plasma offers a credible solution by being powered by renewable energy electricity, and by allowing this energy to be stored by converting the CO2 "waste".
The use of cold plasmas to activate the CO2 molecule and allow its conversion to a higher energy content molecule is a very promising solution. Indeed, the average energy of the electrons in a molecular gas plasma primarily promotes the vibrational excitation of the molecules, which therefore constitutes a formidable reservoir of energy. The aim of our research is to optimize the use of this vibrational excitation in order to trigger chemical reactions at a minimal energy cost.
Non thermal plasma / catalyst coupling
The coupling of non thermal plasma with catalyst is a promising technique for air treatment. The efficiency of these techniques requires to optimize both the generation of atmospheric pressure filaments and their chemical reactivity, depending on the concentrations and types of pollutants. The coupling with catalytic material is then necessary and a better understanding of the physical and chemical interactions between plasma filaments and different materials (porous, adsorbant or chemically reactive) is essential.
Plasmas in liquids
Plasma in liquids can be generated when a high voltage is applied between two immersed electrodes. In this case, the plasma has a filamentary and tree-like structure. Each plasma channel dissociates water molecule on its path by electron collisions. Highly reactive chemical radicals are produced and destroy any organic molecule dissolved in the liquid. Plasma in water can be used for environmental purposes but its chemical efficiency has to be quantified. Eventually this purely physical process will supplant traditional chemical processes for water pollution control. From a physical point of view, the non thermal plasma team wants to understand how the plasma discharge is initiated in liquids and how it propagates inside a dense medium. Fast time resolved optical diagnostics are implemented to study the dynamics of discharges in liquids under various experimental conditions.
CO2 recycling
Plasma assisted combustion
Microplasmas
The study of microplasmas began to develop in the middle of the 90’s in the USA, before undergoing an important expansion thanks to the experimental and theoretical work that has been performed in the past few years. The interest of microplasmas is that they can be generated at medium and high pressure with a very low applied voltage or injected power. They have applications in various fields such as surface treatment, light sources and microjets.
Among the different types of microplasmas devices, our team studies the micro hollow cathode type (MHCD). The MHCD device is a molybdenum-alumina-molybdenum sandwich and a hole is drilled through the sandwich structure (100, 200 or 400µm). Adding a third planar electrode located about a centimeter from the MHCD, large volume plasma can be generated. In an experimental point of view, we perform electrical characterization, chromatography measurements, CCD imaging, emission spectroscopy and CRDS. In order to confirm the interpretation of the experimental results, we use a simple 1D model to obtain the radial evolution of the densities.
