Limoges, France
Limoges, France
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Landreau X.,SPCTS | Boens B.,LCSN | Lanfant B.,SPCTS | Merle T.,SPCTS | And 4 more authors.
Technical Proceedings of the 2012 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2012 | Year: 2012

A coaxial injection microwave excited plasma torch operating at atmospheric pressure is applied to synthesizing SiO xH yC z nano-islands from hexamethyldisiloxane precursor on prepatterned Pt/Si(100) substrates. Herein we report on the spatial organization of these nano-islands in a square array of indents. Prior to the PECVD deposition, the Pt/Si(100) substrates are patterned by nano-indentation. SEM characterizations demonstrate that nano-indents act as trapping sites, allowing ripening of SiO xH yC z nano-dots at those locations during subsequent deposition and diffusion of chemical species on the surface. Results show that islands ordering is intrinsically linked to the nucleation and growth at indented sites and strongly depends on pattern parameters. Then, we report on the selective alkyno-functionalization of the nano-islands surface, followed by the addition of coumarin fluorophore through click-chemistry process for a sensing purpose.

De Romeo Banoukepa G.,University of Limoges | Antony R.,University of Limoges | Colas M.,SPCTS | Ratier B.,University of Limoges
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2010

Organic devices such as solar cells or light emitting diodes (OLEDs) have been intensively studied for the last decade, and have now the potential to reach the market for various applications. Nevertheless, various reports have shown that devices based on Indium Tin Oxide anode present a reduced efficiency due to indium diffusion into organic active layers. In this context, our work focus on the development and the characterization of alternative anodes based on Single Walled Carbon Nanotube (SWNT) Films. In particular, this work is devoted to the morphology and charge transport properties of carbon nanotube thin layers. SWNT films were prepared on glass substrates using the vacuum filtration method reported by Wu et al. As a second step, the films were dipped in a nitric acid and subsequently dried in order to reduce their sheet resistances. Raman spectroscopy is then used to chemically map the film surface, and allow us to assess the homogeneity of the achieved films. Finally, optical and electrical characterizations (measurements of the sheet resistance and optical transmission) provide evidence of a correlation between the quality of the surface and the nature of charge transport occurring in the prepared SWNT films. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Prieur D.,CEA Marcoule Nuclear Site | Prieur D.,Limoges National Superior School of Industrial Ceramics | Martin P.M.,French Atomic Energy Commission | Lebreton F.,CEA Marcoule Nuclear Site | And 6 more authors.
Journal of Solid State Chemistry | Year: 2012

Uranium-americium mixed oxides are promising fuels for achieving an efficient Am recycling. Previous studies on U 0.85Am 0.15O 2±x materials showed that the high α activity of 241Am induces pellet swelling which is a major issue for cladding materials design. In this context, X-ray Diffraction and X-ray Absorption Spectroscopy measurements were used to study self-irradiation effects on U 0.85Am 0.15O 2±x local structure and to correlate these results with those obtained at the macroscopic scale. For a cumulative α decay dose equal to 0.28 dpa, it was shown that non-defective fluorite solid solutions were achieved and therefore, that the fluorite structure is stable for the studied doses. In addition, both interatomic distance and lattice parameter expansions were observed, which only partially explains the macroscopic swelling. As expected, an increase of the structural disorder with self-irradiation was also observed. © 2012 Elsevier Inc. All rights reserved.

Chehaidi S.,SPCTS | Foucaud S.,SPCTS | Maitre A.,SPCTS | Goursat P.,SPCTS | And 5 more authors.
Applied Organometallic Chemistry | Year: 2010

Two routes were simultaneously investigated to prepare organometallic precursors. They were characterized by NMR and FTIR techniques. In the first route, yttrium acetate was silylated by trimethylchlorosilane before its dissolution in hexamethydisilazane. That leads to a liquid precursor containing Si-C-N-Y-O-H elements. In the second route, a precursor with the same elements was elaborated by dissolution of an amminolysed yttrium compound in tetramethyldisiloxane. The amminolysed yttrium compound was obtained through the amminolysis of the yttrium trichloride by triethylamine [N(C2H 5)3]. Copyright © 2010 John Wiley & Sons, Ltd.

Rossi F.,Arts et Metiers ParisTech | Lambertin M.,Arts et Metiers ParisTech | Delfaut-Durut L.,CEA Valduc Center for Nuclear Studies | Maitre A.,SPCTS | Vilasi M.,University of Lorraine
International Journal of Materials Research | Year: 2010

Transformations undergone by lead - calcium alloys are numerous and have different kinetics from a few minutes to a few years. Anisothermal calorimetric measurements were performed to be able to identify these transformations quickly. It was then possible to identify five transformations. Complementary measurements have enabled us to define transformations with an in-situ electrical resistance measurement to follow the evolution of the calcium in solid solution and with an in-situ hardness measurement to characterise the mechanical properties. The aim of these results is to simulate the ageing and overageing of the alloy in isothermal conditions. Copyright © Carl Hanser Verlag GmbH & Co. KG.

Candidato R.T.,Jr. | Sokolowski P.,SPCTS | Sokolowski P.,Wroclaw University of Technology | Pawlowski L.,SPCTS | Denoirjean A.,SPCTS
Surface and Coatings Technology | Year: 2015

The liquid precursors of calcium hydroxide and diammonium hydrogen phosphate were injected into the plasma jet generated by the SG-100 torch to synthesize the hydroxyapatite (HA) coatings. Three operational deposition process parameters, namely: (i) electric power, (ii) spray distance, and (iii) scan speed were varied. The process enabled synthesization of coatings with HA as major phase onto stainless steel substrates. The coatings were deposited to reach the thickness of about 50. μm with high rate ranging from 3. μm to nearly 7. μm by pass of torch. The X-ray diffraction (XRD) analysis of coatings enabled finding of HA accompanied by calcium phosphates, calcium oxide, and calcium carbonate. The presence of the carbonates was confirmed by Fourier Transform Infrared (FTIR) spectroscopy and by elemental mapping made with the use of Electron Dispersive X-ray Spectroscopy (EDS). The morphology of coatings, observed using scanning electron microscope (SEM), revealed fine-grained microstructure and porosity in the range of 1.3 to 5.1%. The adhesion of coatings obtained using scratch test characterized by critical force was in the range of 2.5 to 3.6. N. © 2015 Elsevier B.V..

Chehaidi S.,SPCTS | Foucaud S.,SPCTS | Maitre A.,SPCTS | Goursat P.,SPCTS
Powder Technology | Year: 2011

SiCNYO nanopowders have been elaborated by a spray pyrolysis method from an organometallic precursor which is synthesized by two different routes. Fourier-transform infrared spectroscopy and solid state nuclear magnetic resonance were used to identify the silylation and the amminolysis mechanism applied for the synthesis of each precursor. The SEM micrographs of the each "as-pyrolysed" product revealed spherical SiCNYO nanopowders with a bimodal size distribution. A drop-to-particle and a gas to particle exchanges seem to be the two mechanisms at the origin of grains size distribution. The nature and the reactivity of the carrier gas used in the aerosol indicate a significant influence on the powder morphology. It was found also that evaporation rate of the as-prepared precursor may lead to prevent the enlarging of particles. © 2010 Elsevier B.V.

Chehaidi S.,SPCTS | Salles V.,SPCTS | Foucaud S.,SPCTS | Maitre A.,SPCTS | Goursat P.,SPCTS
Journal of the European Ceramic Society | Year: 2011

We performed pyrolysis of SiCNAlH and SiCNYOH nanopowder precursors under a reactive atmosphere (Ar/NH3/H2) with various compositions of ammonia (NH3) and dihydrogen (H2) to diminish C content, which is deleterious for thermal stability and sintering of the powders. This paper continues a previous work on the fabrication of an Si3N4/SiC composite without free C by studying the effect of H2 on the C/N atomic ratio of the powder. We studied the influence of the nature of the gaseous mixture (Ar/NH3/H2) on the powder composition. Elemental analysis showed that the introduction of H2 in the pyrolysis atmosphere limited the decomposition of NH3 and allowed for control of the C/N ratio. This behaviour can be explained by the structural evolution observed by 29Si NMR spectrometry but also by Fourier transform infrared and Raman spectroscopy. An Si3N4/SiC composite, with traces of free C, was obtained after post-pyrolysis heat treatment of the powders synthesized with 10wt.% of H2 and 25wt.% NH3. © 2011 Elsevier Ltd.

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