Orléans, France
Orléans, France

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Wattieaux G.,CILAS | Lecerf P.,CILAS | Meyer L.,GREMI | Boufendi L.,GREMI | And 9 more authors.
Journal of Physics: Conference Series | Year: 2011

On Line Measurements campaigns have been carried out for the first time in IRAMIS/SPAM CEA's laser gas-phase pyrolysis nanoparticles production facilities. The produced aerosol is composed of Argon and/or Helium laden with SiC nanoparticles concentrated up to ∼14 mg/l. Different commercial apparatus were used for sampling, and characterisation of size, and morphology of the particles. A series of experiment is performed by IRSN with a DMS500 from Cambustion Ltd™, which gives electrical mobility equivalent diameter distribution in real time. Particles are sampled with an ejector-diluter VKL-10 from Palas™. On the same sampling line, APTL performed aerodynamic equivalent diameter mass distribution using a Nanomoudi from MSP Corp.™ and TEM post analysis, as well as post elemental analysis (EDS) after collection on TEM grid with a Thermophoretic Precipitator (TP). A previously developed model is used to obtain the aggregate morphology and primary particles sizes. In addition to these commercial or well-known techniques, a new patent-pending technique called RFPM (Radio Frequency Plasma Metrology developed by CILAS + GREMI in the frame of NANOCARA program) is tested for the first time off the lab. The principle is based on levitation of particles in plasma RF. The entire set up is a prototype, including the sampling line. Experiments showed that this technique is very promising for on line gas phase monitoring, even though future improvements are needed, especially on the direct injection of the sample in the measuring chamber. First results of size distribution on pyrolysis line were obtained: three modes of different geometric mean diameter D50 were measured. Further analysis of TEM micrographs gave insight on these three modes, they can be interpreted as primary particles, aggregated particles, and a third one which could be composed of silica oxide nanoparticles issued from the combustion of the remaining silane initiated by an air leak in the exhaust of the reactor. Furthermore, a parametric study was undertaken. Helium addition in reactor and laser power were authorized to vary within a significant range. There was an evidence of influence of these parameters on the size distributions. Thus, we have demonstrated the high interest of implementing a size monitoring set up on gas phase nanoparticles production line for safety, yield improvement, and cost reduction purposes. This set up can run in a safe and non invasive way, and require low maintenance.

Leray A.,GREMI | Leray A.,Renault S.A. | Guy A.,Safran | Makarov M.,Renault S.A. | And 3 more authors.
Topics in Catalysis | Year: 2013

The effect of a non-thermal plasma reactor over a commercial Diesel oxidation catalyst (DOC) was investigated. Studies have been focused on the gas treatment efficiency together with lowering light-off temperature when a DOC catalyst was connected downstream to plasma reactor in test bench scale. Experiments have been conducted using multi-DBDs (dielectric barrier discharge) reactor in planar configuration driven by a HV AC generator (11 kV-15 kHz). The specific input energy was set to 57 and 85 J/L. Experiments were performed in gas composition simulating Diesel exhaust. Commercial DOC, monolith-supported Pt-Pd/Al2O3, was used at gas hourly space velocities of about 55,000 and 82,000 h-1. CO and hydrocarbons light-off curves were determined for DOC, plasma, and plasma-DOC systems by temperature programmed surface reaction from 80 to 400 C. Particular attention has been paid to the gas temperature between the plasma reactor and the DOC. Results show that the plasma-catalyst system provides the lowest light-off temperatures for CO and HCs. Under conditions of this study, light-off temperature improvement by about 57 C was obtained and the plasma reactor totally oxidized NO to NO 2 at low temperature. © 2013 Springer Science+Business Media New York.

Massereau-Guilbaud V.,University of Orléans | Massereau-Guilbaud V.,Université Ibn Tofail | Geraud-Grenier I.,University of Orléans | Geraud-Grenier I.,Université Ibn Tofail | And 3 more authors.
AIP Conference Proceedings | Year: 2011

The particles are obtained by PECVD in radiofrequency (13.56 MHz) low pressure plasmas (90%CH4-10%Ar). During the particle growth, the particles trap electrons and modify the EEDF, and the electrical and optical characteristics of the plasma. The plasma is analyzed by Optical Emission Spectroscopy. The excitation temperature and the electron temperature are calculated from the Hα, Hβ, Hγ Balmer hydrogen line intensities and from Ar ones. The temporal evolutions of the temperatures during the particle formation are compared and discussed. © 2011 American Institute of Physics.

Worner L.,MPE | Kovacevic E.,GREMI | Berndt J.,GREMI | Thomas H.M.,MPE | And 3 more authors.
New Journal of Physics | Year: 2012

The growth of nanoparticles in low-temperature plasmas is often accompanied by the formation of complex particle patterns and intricate transport processes. This paper deals with the formation and growth of nanoparticles operated in a mixture of argon and acetylene. The experiments are performed in a cylindrical dc discharge, the so-called PK-4 facility that shall be launched to the International Space Station (ISS) in 2014. The experiments show that the particles are formed in a localized region close to the anode and are transported as still localized dust structures ('dust bullets') along the glass tube. The formation of new particles triggers an oscillatory process that is characterized by the periodic appearance and subsequent removal of dust particles. The frequency of this process, as well as the size of the particles within each 'dust bullet', can be controlled by means of the neutral gas flow. This behaviour can be understood by analysing the size-dependent forces acting on the growing particles. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Gosset N.,GREMI | Ladroue J.,STMicroelectronics | Tillocher T.,GREMI | Lefaucheux P.,GREMI | And 2 more authors.
ECS Transactions | Year: 2014

In this paper, the etched surface states of GaN using two different etching techniques are reported. In Cl2/Ar ICP based plasma, two types of defect were identified: cavities and columns. A strong decrease of the cavity diameter and density on etched surface was observed with the addition of CHF3 in the chemistry. SF6 addition instead of CHF3 leads to an etched surface free of defects with low GaN etch rate similar to that obtained with IBE technique. XPS and AFM measurements revealed the importance of fluorine species which leads to the formation of a GaxFy passivation layer on the GaN etched surface. © The Electrochemical Society.

Quoc An H.T.,Institute of Applied Material Science | Pham Huu T.,Institute of Applied Material Science | Le Van T.,Institute of Applied Material Science | Cormier J.M.,GREMI | Khacef A.,GREMI
Catalysis Today | Year: 2011

The combination of heterogeneous catalysts with non-thermal plasma (DBD operated in sinusoidal mode) was investigated for the removal of toluene from air at room temperature. The DBD reactor gives the possibility to introduce the heterogeneous catalyst directly into the discharge zone (in-plasma catalysis, IPC) or to place the catalyst downstream the plasma zone (post-plasma catalysis, PPC). Various catalytic materials based on Ag, Au, Cu, Co, Mn, La, and Nb, supported on Al 2O 3 and CeO 2 in powder form has been tested to select the catalysts that present the highest activity in the presence of plasma. Without plasma, the reaction of toluene conversion over perovskite, Al 2O 3, and OMS-2 based catalysts are promoted at high temperature (200-400 °C). In the absence of catalysts, the toluene removal efficiencies were in the 55-60% range. When the plasma was combined to catalyst, the toluene removal efficiency strongly increased when the catalysts are in IPC position. Best results, up to 96% toluene conversion, were obtained when using 1 wt% Au/Al 2O 3 and Nb 2O 5 catalysts. © 2010 Elsevier B.V.

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