Mesoporous silica gel containing embedded phosphotungstic acid (PTA) was synthesized by sol-gel co-condensation of tetraethyl orthosilicate with PTA in acidic media. The obtained material had high Brunauer-Emmett-Teller Theory (BET) surface area and pore volume. A characteristic band of the Keggin structure of PTA was present in its FT-IR spectrum while its X-ray diffraction patterns were absent. This proved the embedding of PTA on a sub-molecular level and not as a second phase. Acidic sites were determined by neutralization with base in aprotic solvent, followed by titration of the remaining base with an acid. The material demonstrated high adsorption capacity of Cs. Kinetic studies showed that the adsorption data correlates strongly with the pseudo-second order model. At higher temperatures, the nature of adsorption fit the Langmuir model extremely well. The obtained results can be used in the development of an effective adsorbent for clean-up of water contaminated by radioactive 137Cs.

L'objet de cette thèse est l'étude théorique puis expérimentale de la possibilité de réduire les fluctuations d'origine quantique de la lumière, à l'aide d'une cavité optique bistable contenant un milieu non linéaire. Le calcul des spectres du bruit de la lumière sortant d'une telle cavité optique est présenté à l'aide d'un formalisme "entrée-sortie" permettant de décrire la modification des fluctuations du champ électromagnétique par la cavité, et de tenir compte des fluctuations éventuellement ajoutées par le milieu non linéaire. Ce formalisme est appliqué au cas où le milieu non linéaire est un effet Kerr pur. Ce modèle simple nous permet de dégager un critère pour comparer les qualités des différents milieux existants pour la réduction du bruit quantique. Un milieu composé d'atomes immobiles est de ce point de vue un bon candidat. Cependant, à cause des propriétés spécifiques liées aux résonances atomiques, il nécessite un calcul détaillé des spectres de bruit qui est fait avec le modèle à deux niveaux et le formalisme "entrée-sortie". Ces calculs confirment la possibilité de réduire les fluctuations quantiques de la lumière avec des atomes immobiles. La partie expérimentale de cette thèse décrit la réalisation d'un piège magnéto-optique fournissant un nuage d'atome de césium presque immobiles. L'interaction de ces atomes piégés avec une cavité optique nous a permis d'observer deux phénomènes, dont une oscillation laser due à un gain par effet Raman stimulé dans les atomes froids. L'autre phénomène est la bistabilité optique, parfois accompagnée d'instabilités, dues à la non-linéarité du milieu et à la contre-réaction optique de la cavité. La dernière partie de ce mémoire discute les difficultés de la mesure du bruit quantique de la lumière et présente des mesures préliminaires du bruit de la lumière ayant intéragi avec la cavité bistable.

Graduation date: 1997

Glass materials surround us, impacting our lives on a daily basis, whether geologically deposited by volcanic activity or synthesized in large volume by industry. These amorphous oxide materials are vastly important due to their variety of applications including solid electrolytes, cookware, and storage of high-level nuclear waste. Although they are used for different applications, one common characteristic of these materials is the absence of long-range periodic order. This makes it difficult to use traditional solid-state characterization methods such as x-ray and neutron diffraction to study glass structure. Nuclear magnetic resonance (NMR), is ideally suited to study materials that exhibit short-range non-periodic order as it probes directly at a nucleus of interest and is sensitive to its local structural environment. This ability of solid-state NMR is illustrated by revealing local structural features in various oxide materials presented in this thesis. Within is a compilation of studies looking at basic borates, followed by borovanadates and complex borosilicate glasses. A multinuclear application of using quantum chemical calculations, single and double resonance methods and charge-balance models are discussed to deconvolute the complex structures of these disordered materials. This is followed by a study of a difficult low-gamma nucleus, 73Ge, (once considered “impossible” for solid-state NMR) which is explored for future material studies by looking at 73Ge NMR of crystalline and glassy germanates. 73Ge chemical shifts were related to coordination environments and quadrupolar coupling constants were related to bond length distortions.

Ce travail porte sur l'étude d'isotopes de cesium (118,146Cs) et de francium (207-213Fr et 220-228Fr) par spectroscopie atomique hyperfine et sur l'interprétation de ces résultats du point de vue nucléaire. Les grandeurs nucléaires mesurées sont : le spin, le moment magnétique, le moment quadrupolaire électrique et le rayon carré moyen de charge. La technique employée, basée sur le pompage optique hyperfin à l'aide d'un laser accordable, puis la sélection magnétique des atomes est décrite dans la première partie. Les résultats de ces mesures atomiques y sont également présentés. Dans la seconde partie, ces résultats sont interprétés dans le cadre de modèles nucléaires. Les déformations des isomères des césiums légers sont comparées aux valeurs obtenues par un calcul théorique auto-consistant. Les isotopes de francium lourds se trouvent dans une région où est prédite l'existence de déformations octupolaires statiques. L'effet pair-impair mesuré sur le rayon carré moyen est anormal dans cette région. Mais les résultats expérimentaux ne permettent pas de conclure définitivement quant à la nature de ces déformations.

Glass materials surround us, impacting our lives on a daily basis, whether geologically deposited by volcanic activity or synthesized in large volume by industry. These amorphous oxide materials are vastly important due to their variety of applications including solid electrolytes, cookware, and storage of high-level nuclear waste. Although they are used for different applications, one common characteristic of these materials is the absence of long-range periodic order. This makes it difficult to use traditional solid-state characterization methods such as x-ray and neutron diffraction to study glass structure. Nuclear magnetic resonance (NMR), is ideally suited to study materials that exhibit short-range non-periodic order as it probes directly at a nucleus of interest and is sensitive to its local structural environment. This ability of solid-state NMR is illustrated by revealing local structural features in various oxide materials presented in this thesis. Within is a compilation of studies looking at basic borates, followed by borovanadates and complex borosilicate glasses. A multinuclear application of using quantum chemical calculations, single and double resonance methods and charge-balance models are discussed to deconvolute the complex structures of these disordered materials. This is followed by a study of a difficult low-gamma nucleus, 73Ge, (once considered “impossible” for solid-state NMR) which is explored for future material studies by looking at 73Ge NMR of crystalline and glassy germanates. 73Ge chemical shifts were related to coordination environments and quadrupolar coupling constants were related to bond length distortions.

Clusters of atoms or molecules form the building blocks of nanoscience and are regarded as a new type of material, as they constitute a bridge between microscopic and macroscopic forms of matter. The experimental and quantum theoretical study of structures, chemical and physical properties and reactivities of nanoclusters represents an innovative and very active field of research, which has resulted in a wide range of applications. Independent of the model used to describe the bonding in these clusters, one of the prime objectives is to find the geometrical arrangement of the atoms or molecules, for a given cluster size, which corresponds to the lowest energy on the potential energy hyper-surface, the global minimum. In order to find such an arrangement, a density functional theory based genetic algorithm code, which is rooted in the Darwinian evolution concept of the survival of the fittest, is developed and utilized to systematically search for the global minimum isomers of homo-nuclear clusters consisting of up to twenty atoms of cesium, tin, gold and of nine atoms of copper. The performance of this algorithm is excellent as numerous energetically lower-lying cluster isomers (compared to those reported in the literature) are found. Extensive valence basis sets together with energy-consistent scalar-relativistic pseudopotentials are employed to optimize the geometry of these clusters and to calculate their electronic properties accurately at the density functional level of theory. Moreover, in collaboration with the Technische Universit??t Darmstadt, the mean static polarizability of tin clusters are measured by a beam deflection method. The qualitative agreement between measured and calculated dipole moments and static electric dipole polarizabilities of tin clusters up to twenty atoms is satisfactory, thus confirming the accuracy of the theoretical models used in this work. Furthermore, the performance of density functional theory in the field of metallophilicity is investigated for dimeric and trimeric [X-M-PH3] compounds (X = Cl, Br, I; M = Cu, Ag, Au) and it is found that the metallophilicity decreases down the group 11 elements of the periodic table of elements.

Made available in DSpace on 2014-10-09T12:42:47Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:19Z (GMT). No. of bitstreams: 1 05234.pdf: 8658831 bytes, checksum: 5fdbfa575f19ac2ea95052849f7b67f1 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Ce travail porte sur la synthèse et la caractérisation de nouveaux matériaux afin de proposer une alternative dans le cadre de la dépollution nucléaire. Dans une première partie bibliographique, les principaux matériaux inorganiques utilisés pour ce procédé sont décrits en précisant leurs capacités de sorption. Les matériaux lamellaires apparaissent comme possédant un fort potentiel pour cette application. Deux solides ont retenu notre attention : les nanostructures à base de vanadates et de manganates.Des synthèses solvothermales sous flux micro-ondes de ces composés sont ensuite développées, afin d’obtenir une structuration sous forme de nanotubes de vanadates et de nanofleurs de manganates. Une optimisation des vanadates a ainsi été menée en évaluant l’impact de différents facteurs (par exemple, temps de maturation, temps de chauffage, nature et quantité de templates) sur les propriétés structurales et texturales des produits synthétisés. L’enroulement des feuillets est fortement influencé à la fois par la quantité d’amine et sa structure chimique. En effet, seules les amines à longue chaîne conduisent à l’obtention de nanotubes de façon homogène. Une analyse structurale a également été menée pour les deux types de composés en couplant les données expérimentales et celles obtenues par simulation.Les performances de sorption et la sélectivité des matériaux dans différents milieux (eau ultra-pure, eau de rivière) ont été évaluées vis-à-vis du césium et du strontium, seuls ou en mélange. Les résultats montrent clairement une sélectivité très forte des vanadates vis-à-vis du Cs+ et des manganates pour le Sr2+, même en milieu compétitif.La calorimétrie et la simulation moléculaire ont finalement été couplées pour mieux décrire les processus de sélectivité. / This work focuses on the synthesis and characterization of new nanostructured materials that can be potentially proposed as alternatives in the field of nuclear decontamination. The first part is devoted to the state of the art on the use of inorganic materials for decontamination purposes, with the emphasis placed on their sorption capacity and selectivity. The layer materials are considered as offering potential for such applications. In consequence, the main efforts in this work have been focused on manganate and vanadate nanostructures.Solvothermal synthesis of these materials was developed on the basis of micro-wave oven procedures to control the materials structuring, thus leading to vanadate nanotubes and manganate nanoflowers. The optimization of vanadates was carried out by taking into account the effect of various factors (e.g., duration of maturation and heating stages, nature and mass of the template) on both the structural and textural properties of the resulting substrates. It was demonstrated that the scrolling of the layers was strongly influenced by the amount of amine and its chemical structure. Indeed, only the amine templates possessing long chains allowed homogeneous nanotubes to be achieved. More information about the structuring process was inferred when coupling experimental and simulation approaches.The sorption performance of the resulting solid materials in terms of sorption capacity and selectivity was assessed in model and simulated systems obtained by using either ultrapure or river water with an adequate composition as solvent to prepare aqueous solutions of strontium or/and cesium. The results of sorption experiments clearly indicated strong selectivity of the vanadate structures toward Cs+ and that of the manganate ones toward Sr2+, even under conditions of competition among various ionic species.Direct calorimetry measurements of heat effects accompanying sorption were correlated with the results of molecular simulation studies to shed more light on the origin of the improved sorption selectivity.

Made available in DSpace on 2014-10-09T12:45:34Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:28Z (GMT). No. of bitstreams: 1 07179.pdf: 6113980 bytes, checksum: 1a969cfb7280cccf98f26594e185a2c2 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP