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18 results on '"Vallé, Karine"'

2. The core contribution of transmission electron microscopy to functional nanomaterials engineering

Author

Carenco, Sophie, primary, Moldovan, Simona, additional, Roiban, Lucian, additional, Florea, Ileana, additional, Portehault, David, additional, Vallé, Karine, additional, Belleville, Philippe, additional, Boissière, Cédric, additional, Rozes, Laurence, additional, Mézailles, Nicolas, additional, Drillon, Marc, additional, Sanchez, Clément, additional, and Ersen, Ovidiu, additional

Published
2016
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12. Sol-Gel Coatings Ageing in LIL Pockels Cells

Author

Lavastre, Eric, primary, Maunier, Cédric, additional, Gaborit, Gaël, additional, Poncetta, Jean-Christophe, additional, Leymarie, Christophe, additional, Berthier, Thierry, additional, Pasini, Eric, additional, Père, Pascal, additional, Vallé, Karine, additional, Beaurain, Laurence, additional, Belleville, Philippe, additional, and Gamache, Caroline, additional

Published
2007
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15. One step microwave-assisted synthesis of nanocrystalline WOx–ZrO2acid catalystsElectronic supplementary information (ESI) available: Experimental section (synthesis protocols and characterization techniques). Characterization of the materials and catalytic results not shown in the manuscript. See DOI: 10.1039/c6cy01082b

Author

Gonell, Francisco, Portehault, David, Julián-López, Beatriz, Vallé, Karine, Sanchez, Clément, and Corma, Avelino

Abstract

Nanocrystalline ZrO2and WOx–ZrO2catalysts with good control over the zirconia phase and the nature of the W species were synthesized by a microwave-assisted aqueous route. The monoclinic ZrO2(m-ZrO2) and tetragonal ZrO2(t-ZrOz) polymorphs were isolated through accurate control of the synthetic conditions, in acidic and basic media, respectively. The evolution of the zirconia and W species under annealing of the WOx–ZrO2nanocomposites at 500 °C and 800 °C was studied, and the resulting materials were tested as catalysts for aldoxime dehydration and hydration of alkynes for the production of nitriles and carbonyls, respectively. In the dehydration reaction, the most active species are W(vi) in tetrahedral coordination, independently of the ZrO2polymorph, while in the hydration reaction the zirconia phase plays a key role, as the tungsten doped t-ZrO2appears to be the most active catalyst.

Published
2016
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17. Elasticity of an Assembly of Disordered Nanoparticles Interacting viaEither van der Waals-Bonded or Covalent-Bonded Coating Layers

Author

Ayouch, Adil, Dieudonné, Xavier, Vaudel, Gwenaëlle, Piombini, Hervé, Vallé, Karine, Gusev, Vitalyi, Belleville, Philippe, and Ruello, Pascal

Abstract

Tailoring physical and chemical properties at the nanoscale by assembling nanoparticles currently paves the way for new functional materials. Obtaining the desired macroscopic properties is usually determined by a perfect control of the contact between nanoparticles. Therefore, the physics and chemistry of nanocontacts are one of the central issues for the design of the nanocomposites. Since the birth of atomic force microscopy, crucial advances have been achieved in the quantitative evaluation of van der Waals and Casimir forces in nanostructures and of adhesion between the nanoparticles. We present here an investigation, by a noncontact method, of the elasticity of an assembly of nanoparticles interacting viaeither van der Waals-bonded or covalent-bonded coating layers. We demonstrate indeed that the ultrafast opto-acoustic technique, based on the generation and detection of hypersound by femtosecond laser pulses, is very sensitive to probe the properties of the nanocontacts. In particular, we observe and evaluate how much the subnanometric molecules present at nanocontacts influence the coherent acoustic phonon propagation along the network of the interconnected silica nanoparticles. Finally, we show that this ultrafast opto-acoustic technique provides quantitative estimates of the rigidity/stiffness of the nanocontacts.

Published
2012
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18. Design of interpenetrated networks of mesostructured hybrid silica and nonconductive poly(vinylidene fluoride)-cohexafluoropropylene (PVdF-HFP) polymer for proton exchange membrane fuel cell applications.

Author

Pereira F, Chan A, Vallé K, Palmas P, Bigarré J, Belleville P, and Sanchez C

Abstract

Organic-inorganic hybrid membranes of poly(vinylidene fluoride)-cohexafluoropropylene (PVdF-HFP) and mesostructured silica containing sulfonic acid groups were synthesized by using the sol-gel process. These hybrid membranes were prepared by in situ co-condensation of tetraethoxysilane and an organically modified silane (ormosil) by a self-assembly route using organic surfactants as templates for tuning the architecture of the hybrid organosilica component. In this paper, we describe the elaboration and characterization of hybrid membranes all the way from the precursor solution to the evaluation of the fuel cell performances. These hybrid materials were extensively characterized by using NMR and IR spectroscopy, electron microscopy, or impedance spectroscopy so as to determinate their physicochemical and electrochemical properties. Even though the ion-exchange capacity (IEC) was quite weak, the first fuel cell tests performed with these hybrid membranes show promising results relative to optimized Nafion 112 thanks to great water management of the silica inside the hydrophobic polymer., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2011
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