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26 results on '"Bêche, Eric"'

2. The Oxidation of ZrB 2 /MoSi 2 Ceramics in Dissociated Air: The Influence of the Elaboration Technique.

Author

Charpentier, Ludovic, Miranda, Pedro, Tallaron, Hugo, Nogales, Florencia M., Sández-Gómez, Álvaro, Bêche, Eric, and Balat-Pichelin, Marianne

Subjects
ISOSTATIC pressing, ULTRA-high-temperature ceramics, THERMAL shielding, SCANNING electron microscopy, X-ray diffraction
Abstract

In order to investigate the most extreme conditions in which materials potentially applicable in reusable thermal shields can be operated, ultra-high-temperature ZrB2 ceramics with 20 vol.% MoSi2 were prepared using two different techniques, cold isostatic pressing (CIP) and robocasting (RC, an additive manufacturing technique), followed by consolidation using pressureless spark plasma sintering (SPS). The oxidation behavior of the resulting materials was analyzed in low-pressure dissociated air at three different temperatures, namely 1800, 2000 and 2200 K. Using XRD and surface and cross-section SEM (coupled with EDS), zirconia was found to form at all three temperatures, while silica was only present at 1800 K, with gaseous SiO forming at a higher temperature. The elaboration technique influences the density of the ceramic, and less dense materials undergo deeper oxidation. This investigation suggests that 2000 K is already beyond the maximum temperature threshold at which damage to ceramics is limited by the formation of protective silica. This study confirms that the selected material is a promising candidate for thermal protection applications. [ABSTRACT FROM AUTHOR]

Published
2024
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16. X-Ray Reflectometry Characterization of Plasma Polymer Films Synthesized from Triallylamine: Density and Swelling in Water

Author

Schieda, Mauricio, Salah, Fethi, Roualdes, Stéphanie, Van Der Lee, Arie, Bêche, Eric, Durand, Jean, Institut Européen des membranes (IEM), Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM), Procédés, Matériaux et Energie Solaire (PROMES), and Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[CHIM]Chemical Sciences, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2013

17. Microsystèmes et capteurs opto-thermo-mécaniques sur matériaux polymères

Author

Bêche, Bruno, Gaviot, Etienne, Camberlein, Lionel, Goullet, Antoine, Begou, Thomas, Grossard, Nicolas, Bêche, Eric, Huby, Nolwenn, Ababou-Girard, Soraya, Solal, Francine, Jézéquel, Guy, Zyss, Joseph, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Acoustique de l'Université du Mans (LAUM), Centre National de la Recherche Scientifique (CNRS)-Le Mans Université (UM), Institut des Matériaux Jean Rouxel (IMN), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Ecole Polytechnique de l'Université de Nantes (EPUN), Université de Nantes (UN)-Université de Nantes (UN), PHOTLINE Technologies (PHOTLINE TECHNOLOGIES), AUTRES, Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Photonique Quantique et Moléculaire (LPQM), École normale supérieure - Cachan (ENS Cachan)-CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Le Mans Université (UM)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Université de Nantes (UN)-Ecole Polytechnique de l'Université de Nantes (EPUN), and Université de Nantes (UN)-Université de Nantes (UN)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2007

18. A matrix formulation to shape the concept of effective thermoelectric tensors in superlattices

Author

Bêche, Bruno, Bêche, Eric, Camberlein, Lionel, Polet, Frédéric, Gaviot, Etienne, Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Procédés, Matériaux et Energie Solaire (PROMES), Université de Perpignan Via Domitia (UPVD)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Acoustique de l'Université du Mans (LAUM), Centre National de la Recherche Scientifique (CNRS)-Le Mans Université (UM), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and Le Mans Université (UM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Condensed Matter::Materials Science, Condensed Matter::Superconductivity, [PHYS.MPHY]Physics [physics]/Mathematical Physics [math-ph], [SPI.NRJ]Engineering Sciences [physics]/Electric power, Condensed Matter::Strongly Correlated Electrons, [PHYS.PHYS.PHYS-GEN-PH]Physics [physics]/Physics [physics]/General Physics [physics.gen-ph], [SPI.MAT]Engineering Sciences [physics]/Materials
Abstract

International audience; An overall matrix formalism is shaped to define the concept of effective thermoelectric tensors in idealized free-standing superlattices (SL). Starting from the relations accounting for the thermoelectric effects in anisotropic materials, we include the relevant continuity conditions to formulate a global matrix framework describing the thermoelectric effects in an idealized SL. Effective electrical conductivity and thermal power of such SL are formulated as only two general matrix relationships. These versatile results can be applied to idealized free standing SL with layers of all the classes of any symmetry (triclinic, monoclinic, orthorhombic, hexagonal, tetragonal and cubic) in the low-frequency model.

Published
2005

24. Adsorption and Incorporation of Cadmium into a Calcium Hydroxyapatite

Author

Marchat, David, Bernache-Assollant, Didier, Champion, Eric, Bêche, Eric, and Flamant, Gilles

Abstract

The removal of cadmium from water by fixation into a calcium phosphate apatite Ca10(PO4)6(OH)2 (CaHA) was investigated in batch experiments. These ones were carried out using a wide range of initial Cd2+ concentration, three different temperatures, and several CaHA surface areas. The amount of immobilized cadmium was proportional to the surface area of CaHA, whatever the experimental parameters might be. It could reach 7.1 mol of Cd per mol of starting CaHA. Thermal and XPS analyses on the exchanged powders proved that a part of cadmium was quickly adsorbed at the grains surface in the form of hydrated complexes [Cd(OH2)n]2+. The latter were formed by an ionic exchange between adsorbed calcium and cadmium of the solution. Adsorption reaction was mainly limited by the number of specific sites available on the grains surface. Structural analyses showed that another part of Cd was slowly incorporated into a solid solution Ca10-xCdx(PO4)6(OH)2 (CaCdHA) onto the CaHA crystals surface. Results demonstrated unambiguously that the incorporation process was a surface precipitation and not an intracrystalline diffusion.

Published
2006
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25. Microstructural characterization of ZrC-MoSi2 composites oxidized in air at high temperatures.

Author

Charpentier, Ludovic, Balat-Pichelin, Marianne, Bêche, Eric, Sciti, Diletta, and Silvestroni, Laura

Subjects
*ZIRCONIUM carbide, *MICROSTRUCTURE, *MOLYBDENUM disilicide, *TEMPERATURE effect, *SCANNING electron microscopy, *OXIDATION
Abstract

Highlights: [•] ZrC/MoSi2 samples oxidized at various temperatures have been analyzed. [•] XPS and cross-section SEM/EDS revealed the compositions of the oxide layers. [•] Oxide phases involve both elements from the carbide and the additives. [•] We propose an oxidation mechanism based upon these observations and literature. [Copyright &y& Elsevier]

Published
2013
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26. Microstructural characterization of ZrB2–SiC based UHTC tested in the MESOX plasma facility

Author

Alfano, Davide, Scatteia, Luigi, Monteverde, Frederic, Bêche, Eric, and Balat-Pichelin, Marianne

Subjects
*CERAMIC materials, *MICROSTRUCTURE, *SILICON carbide, *BORIDES, *OXIDATION, *PLASMA gases, *HIGH temperatures, *SURFACES (Technology)
Abstract

Abstract: Microstructures were investigated for ZrB2–SiC and ZrB2–HfB2–SiC ultra high temperature ceramics that were subjected to a high temperature plasma environment. Both materials were tested in the MESOX facility to determine the recombination coefficient for atomic oxygen up to 1750°C in subsonic air plasma flow. Surfaces were analyzed before and after testing to gain a deeper insight of the surface catalytic properties of these materials. Microstructural analyses highlighted oxidation induced surface modification. Oxide layers were composed of silica with trace amounts of boron oxide and zirconia if the maximum temperature was lower than about 1550°C and zirconia for higher temperatures. The differences in the oxide layer composition may account for the different catalytic behavior. In particular, the presence of a borosilicate glass layer on the surface of ZrB2–SiC materials guarantees atomic oxygen recombination coefficients that are relatively lower than the coefficients measured when only zirconia is present. The oxidation processes of ZrB2–HfB2–SiC materials, associated with catalytic tests carried out up to 1550°C, lead to the formation of hafnia as well as silica, and zirconia. The higher recombination coefficients measured in the case of ZrB2–HfB2–SiC materials can be correlated with the presence of hafnia which is probably characterized by higher catalytic activity compared to zirconia. In any case, the investigated materials demonstrate a low catalytic activity over the inspected temperature range with maximum values of recombination coefficients close to 0.1. [Copyright &y& Elsevier]

Published
2010
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