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Rozprawy doktorskie na temat "Fluorure de cérium":
Makhlouf, Sandy. "Modélisation et simulation de la structure électronique de petites molécules environnementales : Un exemple : les halogénures et monoxydes de Lanthanides (Ce et Lu)". Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR042.
Our research work focuses on the theoretical investigation of the electronic structure of environmental diatomic molecules such as the cerium and the lutetium monoxides (CeO and LuO), the cerium monofluoride (CeF) and the zirconium monosulfide (ZrS). For these studies, we used ab initio quantum chemistry methods which encompass the Hartree-Fock methods, the complete active space self-consistent field (CASSCF) method and the multi-reference configuration interaction methods (ICMR) with single and double excitation. The MOLPRO software package is used to perform the calculations with and without the inclusion of the spin-orbit coupling. The Davidson's correction is considered and the calculations are elaborated in the C2v symmetry. For each molecule, corresponding atomic basis functions are adopted and theoretical models are tested. As result, the potential energy curves are plotted and then fitted to the Morse potential in order to determine the spectroscopic constants (the equilibrium electronic energy Te, the equilibrium internuclear distance Re, the harmonic ωe and anharmonic ωe vibrational constants and the rotational constant Be) of the electronic states 2S+1Lambda+/- and the respective Omega+/- components. The transition and permanent dipole moments are estimated for the Lambda+/- states. The Omega+/- components and the mixing percentages that provide the parental states Lambda+/- are obtained from the ICMRSD(+Q) calculations including the spin-orbit coupling.Our results with and without taking into consideration the spin-orbit effect are very satisfactory. They are compared with the experimental data and show good agreement and in general the relative error is found of less than 6% for all the spectroscopic constants of the studied molecules
Blanc, Wilfried. "Processus de scintillation dans des matériaux fluorés à base de lutécium activés au cérium trivalent". Lyon 1, 2000. http://www.theses.fr/2000LYO10126.
Sronek, Laetitia. "Nouveaux oxydes et oxyfluorures divisés à base de cérium à propriétés anti-UV". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2007. http://tel.archives-ouvertes.fr/tel-00187026.
Les propriétés d'absorption UV de ces composés sont évaluées et corrélées à la composition chimique et aux paramètres structuraux.
Penkala, Bartosz. "Low Temperature Oxygen Mobility Applied to Catalysis". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS022.
Accomplishing specifications of new regulations regarding automotive exhaust after-treatment technologies, e.g. TWC, imply the availability and usage of catalytically active materials and especially oxygen buffer compounds, which can reversibly store and release high quantities of the oxygen. Doped cerium oxide presents still today the only reference compound for a suitable support, due to its high oxygen storage capacity and ability to easily create oxygen ion vacancies. However, for economic reasons and very limited natural abundance to a few countries, the substitution of ceria appears to be mandatory; in this context we note that ceria is part of the list of 13 economically important raw materials which were identified by the European Commission as subject to a high risk of supply interruption.In this context, Brownmillerite-type oxides are of potential interest, since they reveal oxygen ion mobility down to ambient temperature. Furthermore, they allow to adjust the presence of extended defects e.g. anti-phase boundaries, during synthesis conditions, and which have been shown to significantly decrease the activation energy for oxygen diffusion. We were thus able to show that defect-rich nano-Ca2Fe2O5, traditionally known as a stoichiometric line-phase, can be oxidized under mild conditions to CaFeO3, while the oxidation of ordinary Ca2Fe2O5 usually requires extreme reaction conditions, i.e. 1100°C and several GPa oxygen partial pressure. Thus, introducing a high concentration of defects seems to be a promising concept to transform even traditionally known stoichiometric line-phases to become a kind of oxygen sponge and behave as oxygen storage/buffer compound at very moderate temperatures. This behavior is thus comparable to the oxygen storage capacity of doped cerium oxide, and offers a true potential for application in the catalysis. Consequently, the Brownmillerite Ca2Fe2O5 appears to be a promising candidate to study due to its known oxygen ion conductivity properties.Primary aim of this work is to establish fundamental relation between structure/microstructure, oxygen mobility properties and catalytic activity, simultaneously undertaken for two systems: Ca2Fe2O5 with Brownmillerite-type structure and CeO2 with Fluorite-type structure. We essentially explored the underlying criteria governing their chemical/catalytic activity, using oxygen isotope exchange behavior by TG couples MS experiments. Further studies using essentially Raman spectroscopy allowed concluding from a modified lattice dynamics for different oxygen isotopes to differentiate between bulk and surface oxygen participation to the oxidation mechanism of CO to CO2. For a deeper mechanistic understanding of the CO oxidation, we developed a new catalytic test, based on a dynamic variation of the oxygen partial pressure in the reaction vessel, allowing to conclude simultaneously on the catalytic activity of the catalyst and its oxygen release/uptake behavior, not accessible by the classical catalytic activity test performed under constant gas flow. In this way we got a new insight to differentiate the participation of surface and bulk oxygen activity for different Ca2Fe2O5 and ceria based catalysts
Abel, Jonathan. "Corrélations compositions chimiques- structures d'oxydes mixtes (Ce/Zr) à base de Pr4+/Pr3+ et propriétés de réductibilité". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00661383.
Abel, Jonathan. "Corrélations compositions chimiques-structures d’oxydes mixtes (Ce / Zr) à base de Pr4+ / Pr3+ et propriétés de réductibilité". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14334/document.
This work deals with the synthesis and the characterization of Pr1-zCezO2-y and Pr1-xZrxO2-y oxides. Various chemical compositions associated with mixed valence state Pr4+/Pr3+ concomitant to precise oxygen vacancies rate were isolated for compounds in both oxidized and reduced compounds. In the reduced state, different superstructures of the fluorine network were characterized by X-ray and neutrons diffraction. On the basis of magnetic measurements, X-ray absorption spectroscopy (XANES-EXAFS) at Zr K-edge and Pr and Ce LII/III-edges and the thermogravimetric analyses and\or TPR (Temperature Programmed Reduction), evolutions of Pr4+/Pr3+ rates in this series were estimated. Finally, in-situ measurements under reducing atmosphere by neutrons diffraction and EELS (Electron Energy Loss Spectroscopy) were realized to correlate chemical compositions- structural features and reducibility properties