Dans le travail de thèse, nous avons étudié le processus de croissance et l’évolution des propriétés structurales de l’alumine ultra-poreuse (UPA) monolithique pendant le traitement thermique dans le domaine des températures entre 20 et 1600 °C. Un modèle théorique a été proposé permettant de décrire et prédire sa structure. La formation de mullite à partir d’alumine imprégnée par la silice a été également étudiée. Les premières mesures conduites sur les propriétés diélectriques des UPA dans le domaine de fréquences GHz-THz montrent des possibilités d’application dans le domaine de l’optique réfractrice. L’installation expérimentale pour l'élaboration des monolithes ultra poreux est décrite. L’étude de la cinétique de croissance à partir d’aluminium technique, ultra pur et monocristallin a permis d’analyser l’influence des différentes impuretés présentes. Les matériaux ont été caractérisés par les méthodes DRX, MET/MEB, ICP/OES, TGA et PL. Les UPA modifiées chimiquement par imprégnation de TMES et TEOS en phase vapeur ont également été analysées. L’étude en fonction de la température des différents matériaux a été menée sur la taille des fibreuse, la surface spécifique, la densité massique, ainsi que la quantité de l’eau structurelle et adsorbée, d’une part, et la structure cristalline d’autre part. L’utilisation des méthodes DRX et PL corrélées a permis d’expliquer une transformation de la phase α de l’UPA en mullite 2:1.Le modèle proposé distingue deux principaux régimes de modification thermique de la structure des UPA : transport de masse sur la surface d’une fibre ou de la masse globalement (frittage). Des énergies d’activation du transport massique et des constantes pre-exponentielles ont été obtenues pour les deux régimes. Les résultats obtenus permettent de conclure que les transformations morphologiques, de la composition chimique et de la phase cristalline sont d’origine commune. / In this PhD work we investigated growth process and evolution of structural properties of ultraporous alumina (UPA) monoliths during thermal treatment in the range between 20 and 1600 °C. A simple theoretical model was proposed permitting description and prediction of the material structure. A particular extension of this study concerns the mullite formation with an increase of the silica loading. Furthermore, first measurements of dielectric properties (refraction index and losses) in GHz-THz range of frequencies were performed, indicating this material to be potentially interesting for fabrication of the refraction optics.The experimental installation for UPA elaboration is described, and the analysis is presented of principal impurities and their influence on the growth kinetics using technical, high-purity and monocrystalline aluminum. The obtained materials were characterized by XRD, TEM, SEM, ICP/OES, TGA and PL methods. UPA modified with TMES and TEOS vapor impregnations were also obtained and analyzed. The fibril size, specific surface area, mass density and content of structural, adsorbed water and crystalline phase were measured for different UPA materials as a function of the annealing temperature. The correlated XRD and PL analyses was performed explaining the conversion of α phase UPA to 2:1 mullite, which fundamental band gap was set to 7.55 eV.The proposed model distinguished two principal regimes of thermal modifications: surface diffusional mass transport over a single fibril and bulk mass transport involving total material mass (sintering). The activation energies of the mass transport and pre-exponential constants (diffusion coefficient and free volume) in both regimes were obtained, providing a better understanding of the underlying physical processes in different UPA materials. Based on these results, we conclude about a common origin of morphological, chemical composition and phase transformations.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / In recent years, mesoporous silica has attracted considerable scientifical and industrial interest. This material possess physical and chemical properties, which makes it to be used in a variety of applications. These properties include thermal stability, mechanical strength and low solubility, which makes it an ideal matrix support for catalysts. The heterogeneous catalysis has the advantage of separating catalyst from the reaction medium, which justifies the interest in heterogeneous catalysts. Coordination compounds are widely used in homogeneous catalytic processes, based on this there is a growing interest in producing catalytic systems onto heterogeneous silica matrices making very interesting materials. In this work, ruthenium complexes, [RuIICl2(dppb)(PPh3)] and [RuIIICl3(dppb)(OH2)] were synthesized and immobilized onto mesoporous silica matrices modified with aminopropyl and bipyridine groups forming the systems known as Si-apts-bipy-RuIICl2dppb and Si-apts-[bipy-RuIIICl2dppb]Cl-. These systems were characterized by spectroscopic techniques (FTIR, NMR and electronic absorption), electrochemical (cyclic and square wave voltammetry), thermogravimetry (TG), isotherms of adsorption / desorption of N2 and elemental analysis (CHN). The N2 adsorption isotherms using BJH (Barret, Joyner and Halenda) method for matrices shows the synthesized material has characteristics of micro and mesoporous with predominantly mesopore size. Si-apts-bipy-RuIICl2dppb system was the only one that showed catalytic activity in the reaction of hydrogenation of acetophenone with a yield of 53%. The development of catalysts in solid matrices is an area of great interest, which has justified this work. / A sÃlica mesoporosa à um material bastante versÃtil, com porosidade fÃcil de ser moldada tanto em forma quanto em tamanho, alÃm de possuir propriedades fÃsicas e quÃmicas que lhe possibilitam diversas aplicaÃÃes. Dessas propriedades destacamos a sua estabilidade tÃrmica, sua resistÃncia mecÃnica e sua pouca solubilidade as quais a tornam um suporte ideal para catalisadores. Nesse sentido, o uso de compostos de coordenaÃÃo ancorados em matrizes sÃlidas torna-se um interessante sistema a ser estudado, tendo em vista as propriedades, jà bem conhecidas, de alguns complexos metÃlicos de atuarem em catÃlise homogÃnea. De acordo com dados na literatura hà um contÃnuo interesse na sÃntese e caracterizaÃÃo de materiais mesoestruturados aplicados a heterogeinizaÃÃo de catalisadores, como por exemplo, o uso de compostos de coordenaÃÃo. Neste trabalho os complexos de rutÃnio, [RuIICl2(dppb)(PPh3)] e [RuIIICl3(dppb)(OH2)] foram sintetizados e imobilizados em matrizes de sÃlica mesoporosa modificada com grupos aminopropil e bipiridinÃcos, formando os sistemas denominados como Si-apts-bipy-RuIICl2dppb e Si-apts-[bipy-RuIIICl2dppb]Cl. Estes sistemas foram caracterizados por tÃcnicas espectroscÃpicas (FTIR, UV-Vis e RMN de 13C, 29Si e 31P), eletroquÃmicas (voltametria CÃclica e Voltametria de onda quadrada), termogravimÃtricas (TG), isotermas de adsorÃÃo/desorÃÃo de N2 e anÃlise elementar (CHN). As isotermas de N2 para adsorÃÃo pelo mÃtodo BJH (Barret, Joyner e Halenda) para as matrizes indicam que o material sintetizado neste trabalho apresenta caraterÃsticas micro e mesoporosas com predominÃncia de mesoporos. Dos materiais sintetizados apenas o sistema Si-apts-bipy-RuIICl2dppb apresentou atividade catalÃtica na reaÃÃo de hidrogenaÃÃo da acetofenona com um rendimento de 53%. O desenvolvimento de catalisadores em matrizes sÃlidas à uma Ãrea ampla e de grande interesse o que justifica o desenvolvimento deste trabalho.