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Your search keyword '"Département Procédés de Transformations des Solides et Instrumentation (PTSI-ENSMSE)"' showing total 2 results
Start Over Author "Département Procédés de Transformations des Solides et Instrumentation (PTSI-ENSMSE)" Publisher american chemical society (acs)
2 results on '"Département Procédés de Transformations des Solides et Instrumentation (PTSI-ENSMSE)"'

1. Oxidation as an Early Stage in the Multistep Thermal Decomposition of Uranium(IV) Oxalate into U3O8

Author

Lénaïc Desfougeres, Loïc Favergeon, Maelig Ollivier, Renaud Podor, Nicolas Clavier, Philippe Martin, Éléonore Welcomme, Myrtille O.J.Y. Hunault, Julie Hennuyer, Département de recherche sur les procédés pour la mine et le recyclage du combustible (DMRC), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Département Procédés de Transformations des Solides et Instrumentation (PTSI-ENSMSE), Centre Sciences des Processus Industriels et Naturels (SPIN-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Laboratoire Georges Friedel (LGF-ENSMSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Etude de la Matière en Mode Environnemental (L2ME), Institut de Chimie Séparative de Marcoule (ICSM - UMR 5257), Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Interfaces de Matériaux en Evolution (LIME), and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)

Subjects
010405 organic chemistry, Chemistry, Inorganic chemistry, Thermal decomposition, chemistry.chemical_element, [CHIM.MATE]Chemical Sciences/Material chemistry, Actinide, [CHIM.INOR]Chemical Sciences/Inorganic chemistry, Uranium, 010402 general chemistry, 01 natural sciences, Oxalate, 0104 chemical sciences, Inorganic Chemistry, chemistry.chemical_compound, Oxidation state, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, Stage (hydrology), Physical and Theoretical Chemistry, [CHIM.RADIO]Chemical Sciences/Radiochemistry
Abstract

International audience; The thermal decomposition of actinides oxalates greatly depends on the oxidation state of the cation, the gas involved and the physical characteristics of the precursor. In the actinides series, uranium(IV) oxalate U(C 2 O 4) 2 .6H 2 O can be viewed as a peculiar case, as its sensibility towards oxidation leads to a specific series of reactions when heating under oxygen atmosphere. In order to clarify the disagreements existing in the literature, particularly concerning potential carbonate intermediates and the possible transitory existence of UO 3 , we show here an extended characterization of the different intermediates through a combination of X-Ray diffraction, vibrational spectroscopies and X-Ray absorption near edge spectroscopy. In this frame, uranium oxidation was found to occur at low temperature (200°C) concomitantly to the onset of oxalate groups decomposition, leading to an amorphous oxo-oxalato compound. Pursuing the thermal conversion up to 350°C led to complete oxidation of U(IV) into U(VI), then to the formation of amorphous UO 3 still bearing adsorbed carbonates. The first pure oxide formed during the thermal conversion was further identified to sub-stoichiometric UO 3- after heating at 550°C. Finally, U 3 O 8 was obtained as the final stable phase after heating above 660°C. The mechanism of thermal conversion of uranium(IV) oxalate into oxide under oxygen is then driven by a complex interplay between redox reactions and decomposition of the organic fractions. Such chemical reactions were also found to significantly modify the morphology of the powder through HT-ESEM observations : decomposition led the size of the aggregates to reduce by 20% while uranium oxidation clearly promoted growth within the agglomerates. 2

Published
2020
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2. Diffusion in CaCO3 Calcite Investigated by Atomic-Scale Simulations

Author

Loïc Favergeon, Rémy Besson, David Tingaud, Unité Matériaux et Transformations - UMR 8207 (UMET), Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Ecole Nationale Supérieure de Chimie de Lille (ENSCL)-Institut National de la Recherche Agronomique (INRA), Laboratoire des Sciences des Procédés et des Matériaux (LSPM), Centre National de la Recherche Scientifique (CNRS)-Université Sorbonne Paris Cité (USPC)-Institut Galilée-Université Paris 13 (UP13), Département Procédés de Transformations des Solides et Instrumentation (PTSI-ENSMSE), Centre Sciences des Processus Industriels et Naturels (SPIN-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Laboratoire Georges Friedel (LGF-ENSMSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Université de Lille - Unité Matériaux et Transformations - Groupe de Métallurgie Physique et Génie des Matériaux, Université Paris XIII - Institut Galilée - Laboratoire des Sciences des Procédés et des Matériaux, Institut de Chimie du CNRS (INC)-Institut National de la Recherche Agronomique (INRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Lille-Ecole Nationale Supérieure de Chimie de Lille (ENSCL), Université Paris 13 (UP13)-Institut Galilée-Université Sorbonne Paris Cité (USPC)-Centre National de la Recherche Scientifique (CNRS), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure de Chimie de Lille (ENSCL)-Institut de Chimie du CNRS (INC)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), Université de Lille, CNRS, INRA, ENSCL, Unité Matériaux et Transformations - UMR 8207 [UMET], Laboratoire des Sciences des Procédés et des Matériaux [LSPM], and Laboratoire Georges Friedel [LGF-ENSMSE]

Subjects
carbonation, Materials science, Ab initio, Context (language use), 02 engineering and technology, 010402 general chemistry, 01 natural sciences, Atomic units, Vacancy defect, [SPI.GPROC]Engineering Sciences [physics]/Chemical and Process Engineering, Kinetic Monte Carlo, Physical and Theoretical Chemistry, Diffusion (business), 10. No inequality, atomic-scale, calcite, atomic diffusion, 021001 nanoscience & nanotechnology, Crystallographic defect, 0104 chemical sciences, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, General Energy, Orders of magnitude (time), Chemical physics, 0210 nano-technology
Abstract

International audience; In the context of CO2 storage, we used ab initio-based atomic-scale modelings and simulations to study oxygen and carbon diffusion in CaCO3 calcite. In overall agreement with earlier experimental findings, oxygen diffusion is found to take place possibly by either interstitial or vacancy mechanisms depending on the thermodynamic conditions. Contrary to almost isotropic interstitial diffusion, the vacancy mechanism strongly favors oxygen jumps within (111) planes characteristic of the CaCO3 layered structure, with significant less-than-unity correlation factors. Our simulations show that such mechanisms cannot be applied to carbon, and complex point defects may be required to explain the diffusion of this element. While stability arguments indicate that vacancy complexes formed with CO or CO3 missing groups may be efficient candidates to convey C diffusion, no low-energy migration path could be identified for these complexes. Focusing on the mostly stable CO vacancy complex and using generic values for unknown migration energies, kinetic Monte Carlo simulations show that this complex mechanism may be responsible for C diffusion roughly 2 orders of magnitude above its oxygen counterpart.

Published
2019
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