Combustion, Plasma and Environment

The Combustion, Plasma and Environment group in the Department of Molecular Physics brings together researchers working in the areas of Flame Physics and Chemistry, Electrical Arcing, Nanoparticle formation in plasma environments, plasma chemistry, planetary atmospheric and atmospheric chemistry and the emission of pollutants from natural sources.

The group not only has its in-house apparatus for studying chemical processes and problems associated with electrical switching but is a long-time user of “Grand Instruments”, large scale experimental facilities such as the European Synchrotron Radiation Facility (ESRF), Synchrotron Soleil, neutron sources in France and England, the Mersen High Current Laboratory in Grenoble and heavy ion storage rings in Denmark and Sweden. We have plans to use the new X-Ray laser facility (LCLS) at Stanford University in the US and a new Heavy Ion Storage Ring in Langzhou in China.

The individual research areas of the group are outlined in the following:

Nanoparticle Formation in Flames

This work is based on the use of Small Angle X-Ray Scattering (SAXS) to measure the size distribution of soot particles formed in hydrocarbon flames and how this distribution can be modified by additives. Experiments are performed at the ESRF in Grenoble. The group is a pioneer in this research that allows soot formation to be followed in-situ, in real time in laboratory scale flames. [1]

Collaborations:

  • S. Di Stasio, Istituto Motori, Naples, Italy
  • F. Ossler, Lund University

Nanoparticle Formation in Plasmas

Having demonstrated that SAXS can be used in dilute gaseous environments such as flames, we have applied the method to investigating nanoparticles created in microwave air plasmas and most recently in laser ablation plumes and electrical arcs. This is a non-intrusive method and yields information on nanoparticle condensation phenomena under extremes of temperature. Experiments are performed at the ESRF and Synchrotron Soleil in collaboration with researchers from the University of Tel Aviv in Israel, The University of Bourgogne and Schneider Electric. [2]

Collaborations:

  • E. Jerby, University of Tel Aviv, Israel
  • L. Lavisse, University of Bourgogne
  • Schneider Electric.

Synchrotron Radiation Studies of Free Nanoparticles

This work performed in collaboration with scientists from Synchrotron Soleil, the CEA, IRSN and the University of Rouen involves injecting pre-prepared nanoparticles into a vacuum apparatus via an aerodynamic lens and performing x-ray photoelectron and mass spectrometric studies on these particles as they are exposed to tuneable soft x-ray radiation. Amongst the goals of the project is to examine slow oxidation phenomena and to characterise soot particle chemistry. In future experiments, SAXS will be applied to these experiments to tie down the size of the particles exiting the lens, prior to irradiation.

Collaborations:

  • C. Miron, Synchrotron Soleil
  • O. Sublemontier, CEA
  • F-X, Ouf, IRSN
  • J. Yon, INSA, Rouen

Electrical, Arcing and its Consequences

The Electrical contacts laboratory has a worldwide reputation in the study of the degradation of electrical contacts used in switches in the automotive and aeronautical industries. The influence of arcing and mechanical constraints on contact wear brings together fields such as metallurgy, magnetism, friction, mechanical properties of matter, plasma spectroscopy and fire ignition in electrical cables. [3]

Collaborations: Renault, Metalor, FCI, EDF, Schneider Electric

Electron recombination and attachment

These are fundamental studies related to plasma chemistry whether terrestrial such as in fusion reactors or processing devices or in planetary atmospheres and interstellar clouds. These studies are performed either using the flowing afterglow techniques in our laboratory in Rennes or at Heavy ion Storage Rings using the electron-ion merged beams technique. Plans are in place to use the new accelerator facility at Langzhou in China to study product branching ratios. [4]

Collaborations:

  • A. Viggiano, United States Air Force
  • M. Chabot, l’Institut de Physique Nucléaire d’Orsay
  • P. Pernot, Laboratory de Chimie-Physique d’Orsay
  • I. Schneider, The Université du Havre
  • K. Beroff , l’Institut des Sciences Moléculaires d’Orsay
  • V. Kokoouline, Florida State University

Atmospheric Chemistry Studies

It is well established that the gas phase degradation of Volatile Organic Compounds (VOCs) plays a central role in the generation of a variety of secondary pollutants which may have a harmful impact on human health and on the environment. In order to provide a better knowledge of the environmental impact of VOCs, it is necessary to understand their atmospheric fate. In this respect, this project aims to study the kinetics and mechanisms of neutral-neutral gas-phase reactions involving VOCs under atmospheric conditions. These experimental data are useful in atmospheric modelling. Kinetic studies are performed using a newly constructed apparatus based on a cryogenic cell coupled to the PLP-LIF technique. [5]

The development of this apparatus has been funded by the “Région de Bretagne”.

Collaborations:

  • Department of Chemistry-Physics – University of Castilla La Mancha (UCLM), Ciudad Real, Spain
  • Departments of Physics and Chemistry -Lebanese University-Beirut-Lebanon
  • « Groupe de Spectrométrie Moléculaire et Atmosphérique GSMA » –University of Reims Champagne Ardenne-France
  • « Laboratoire des Sciences analytiques » –University of Lyon- France

Pollutant emissions from natural Sources

This is a new project that aims to characterise pollutants emitted from sources such as Green Algae on beaches, a problem of particular importance in Brittany. To this end we have obtained financing for the acquisition of a portable Proton Transfer Mass Spectrometer that will allow in-situ quantitative measurements of pollutant species to be rapidly. This technique closely resembles the afterglow methods already used by the group. Additional projects will involve detecting pollutants from livestock rearing facilities (in collaboration with INRIA and cooperation with the University of Béjaia in Algeria for studies of emissions from open burning.

References

  • [1] Demonstration of the Onset of Soot Particle Aggregation and Growth in an Ethylene Flame by Small Angle X-Ray Scattering , J. B. A. Mitchell, S. di Stasio, J.L. LeGarrec, A.I. Florescu-Mitchell, T. Narayanan and M. Sztucki, Journal of Applied Physics 105, 124904 (2009)
  • [2] Evidence for nanoparticles in microwave-generated fireballs observed by synchrotron X-ray scattering, J.B.A. Mitchell, J.L. LeGarrec, M. Sztucki, T. Nayaranan, V. Dikhtyar and E. Jerby, Phys. Rev. Lett. 100, 065001 (2008)
  • [3] New contact material for reduction of arc duration for dc application.
    L. Doublet, N. Ben Jemaa, S. Rivoirard, C. Bourda, E. Carvou, D. Sallais, D. Givord, P. Ramoni, European Physical Journal – Applied Physics, 50, 1 ( 2010)
  • [4] The Dissociative Recombination of Molecular Ions: An Experimental and Theoretical Review, A. I. Florescu-Mitchell and J.B.A. Mitchell, Physics Reports 430, 278 (2006)
  • [5] Gas phase UV absorption cross-sections for a series of hydroxycarbonyls “, L. Messadia. G. El Dib, A. Ferhati, E. Roth., A. Chakir , Chemical Physics Letters, 529, 16 (2012)

Contacts


Gisèle EL DIB

Brian MITCHELL

Jean-Luc LE GARREC

Erwann CARVOU

André CANOSA

Sophie CARLES

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