The objective of this work is the synthesis of model material for manganese dioxygenase which is an enzyme that oxidizes catechol-like substrates with dioxygen. Our strategy comprises three main steps that form the different chapters of this thesis: - Synthesis and characterization of manganese(II) complexes with tridentate ligands. - Optimization of a microwave-assisted synthesis of a mesoporous silica. - Functionalization of these materials and complex grafting, as well as preliminary catalytic tests. The ligands used are tertiary amines containing an alkyne arm and two coordinating arms with functions such as pyridine, imidazole or carboxylate. The complexes were crystallized and/or characterized by IR, EPR, SQUID and cyclic voltamperometry. Microwave synthesis, based on the conditions of classical hydrothermal synthesis, allowed us to reduce the synthesis time from one day to two hours. The quality of these new materials was verified by IR, TGA, BET and powder XRD. These materials are then bi-functionalized using a molecular stencil patterning mehod with a an azide function for complex grafting via click chemistry and a function pyridine or trimethylsilyl to control the coordinating ability of the metal environment. These complexes and materials are active in catechol oxidation with O2.

A new mesoporous MOF, Zn4O(bpdc)(btctb)4/3 (DUT-32), containing linear ditopic (bpdc2−; 4,4′-biphenylenedicarboxylic acid) and tritopic (btctb3−; 4,4′,4′′-[benzene-1,3,5-triyltris(carbonylimino)]tris-benzoate) linkers, was synthesised. The highly porous solid has a total pore volume of 3.16 cm3 g−1 and a specific BET surface area of 6411 m2 g−1, adding this compound to the top ten porous materials with the highest BET surface area.

A NMR study of the structure-dynamics relationships in heterogeneous materials is presented. In the first part, transport in soft-matter systems is studied using the pulsed field gradient NMR technique (PFG NMR). The molecular crowding effect in biological matter has been addressed using polymer solutions as model systems. By performing ensemble-based diffusion studies, the earlier obtained data on anomalous diffusion have been complemented. The transition to normal diffusion on a larger time scale has been shown. Taking advantages of the NMR approach, transport properties of microemulsions consisting of micellar colloids dissolved in liquid crystals have been investigated. The self-diffusivities measured under equilibrium conditions have shown weak correlations with microscopic ordering and macroscopic phase transitions occurring in the systems under study. The formation of micelles is shown to be decisive for macroscopic separation at the isotropic-nematic transition. The second part of the thesis covers heterogeneous effects in diffusion for fluids in porous solids, as probed using a combination of NMR diffusometry and structure characterization methods. Ionic liquids have been investigated, revealing a complex behavior under confinement. The attempts to correlate the observed characteristics of the ionic liquids with their internal chemical structure were undertaken. Finally, the series of nanoporous glasses with tunable pore structure characteristics were studied. Strong correlations between their structure and the preparation conditions as well as between the resulting transport properties have been shown.

This thesis has addressed several of the fundamental challenges in correlating the structure thermal transport properties of complex nanoporous polycrystalline zeolite materials. Two types of zeolite materials, MFI and LTA, were employed in order to investigate the effects of temperature and both the framework and non-framework cations on the thermal conductivity of zeolite. The thermal conductivity values of both materials were measured using a well intergrown zeolite film 3-omega method. The thermal transport mechanisms in these materials were investigated by separately analyzing the contributions of different phonon scattering processes. This thesis represents our progress towards a robust framework for understanding and predicting thermal transport properties of zeolite materials and complex crystals in general. Furthermore, the important roles of boundary and defect scattering, as illustrated in this thesis, also imply that the thermal conductivity of zeolite materials can be tuned by exploiting not only the composition but also the pore structure. In addition, a non-equilibrium molecular dynamics simulation with external force was developed and employed to predict the thermal conductivity of materials. It has shown that this method can accurately predict the thermal conductivity of simple materials, such as argon and quartz; however, it failed to predict the thermal conductivity of complex materials, such as zeolite. This thesis presents possible factors that can explain the phenomena and future recommendations to elucidate this issue.

Thesis (MScEng (Mathematical Sciences. Applied Mathematics))--University of Stellenbosch, 2006. / When considering flow through porous media, different flow regimes may be identified. At very small Reynolds numbers the relation between the pressure gradient and the velocity of the fluid is linear. This flow regime ...

En vue de leur refroidissement, les parois de chambres de combustion aéronautiques sont perforées de trous à travers lesquels de l’air plus froid est injecté. La paroi est ainsi refroidie par convection et un film isolant est créé en surface chaude (film cooling). Cette thèse a pour objectif d’utiliser les possibilités de la fabrication additive pour proposer de nouvelles solutions architecturées qui permettraient d’augmenter les échanges de chaleur internes et d’obtenir ainsi de meilleures efficacités de refroidissement.La première approche consiste à élaborer de nouveaux designs de plaques multiperforées par Electron Beam Melting (EBM) et Selective Laser Melting (SLM) aux limites de résolution des procédés. Les architectures sont caractérisées en microscopie, en tomographie X et en perméabilité. Des simulations aérothermiques permettent de mettre en évidence l’effet de ces nouveaux designs sur l’écoulement et les échanges de chaleur, et de proposer des voies d’amélioration de la géométrie.La deuxième approche consiste à élaborer de façon simultanée une pièce architecturée par EBM, avec des zones denses et poreuses. A partir d’analyse d’images associée à une cartographie EBSD grand champ, il est possible de remonter aux mécanismes de formation du matériau poreux et de relier la perméabilité et la porosité aux paramètres procédé. Afin de favoriser le film cooling, il pourrait être avantageux que les zones microporeuses soient orientées dans le sens de l’écoulement. Pour ce faire, un nouveau procédé dénommé Magnetic Freezing, où des poudres métalliques forment une structure orientée par un champ magnétique, est mis au point.Les diverses solutions développées durant cette thèse sont testées sur un banc aérothermique. Les essais montrent qu’elles offrent un refroidissement plus efficace et plus homogène que la référence industrielle. Enfin, de premiers tests en combustion sur l’une des structures retenues, plus légère et plus perméable que la référence, montrent qu’il s’agit d’une solution aussi efficace à un débit traversant donné, et donc a priori plus efficace à une surpression donnée. / Combustion chamber walls are perforated with holes so that a cooling air flow can be injected through them. The wall is cooled by convection and an insulating film is created on the hot surface (film cooling). This PhD thesis aims to use the possibilities of additive manufacturing to provide new architectured solutions that could enhance the internal heat exchanges, and lead to a higher cooling effectiveness.The first approach is to develop new designs of multiperforated walls by Electron Beam Melting (EBM) and Selective Laser Melting (SLM) used at the resolution limits of the processes. They are characterized by microscopy, X-ray tomography and permeability tests. Some aerothermal simulations help understanding the effects of these new designs on the flow and on heat exchanges. These results lead to a geometry adaptation.The second approach is to simultaneously manufacture an architectured part with dense and porous zones by EBM. Thanks to image analysis combined with large field EBSD, it is possible to investigate the mechanisms leading to the porous zones and to link them to permeability and porosity. The film cooling effect could be favoured by the orientation of pores towards the cooling flow. Therefore, a new powder-based manufacturing process named Magnetic Freezing, where metallic powders organize into an oriented structure thanks to a magnetic field, is developed.The various solutions studied during this thesis are tested on an aerothermal bench. They all show a more efficient and homogeneous cooling than the industrial reference. Some first tests on one of the selected solutions are performed on a combustion bench. This lighter and more permeable structure proves to be a solution as efficient as the industrial reference at a given flow rate. It should therefore be a more efficient solution for a given overpressure.

This thesis combines synthetic studies for isotopic enrichment with solid-state characterisation techniques to investigate two classes of microporous materials: zeolites and metal-organic frameworks (MOFs). These materials have a wide range of successful applications, from industrial catalysis to medicine, resulting in the increasing need for both a complete understanding of their unique structural features and synthetic methods to target new frameworks. Nuclear magnetic resonance (NMR) spectroscopy, thanks to its sensitivity to the local, atomic-scale, environment and its element specificity, is applied, in combination with powder X-ray diffraction (PXRD), electron microscopy, N2 adsorption and mass spectrometry, to the study of these materials. Oxygen atoms play a crucial role in the structure and chemistry of zeolites and MOFs, making 17O NMR an excellent tool for chemical and structural investigations. However, the low natural abundance of this isotope (0.037%) and the cost of 17O-enriched reactants require the development of atom-efficient synthetic processes for isotopic enrichment. In the first part of this work, the unconventional assembly-disassembly-organisation-reassembly (ADOR) method is applied to the Ge-doped UTL framework and optimised in reduced-volume conditions for economic enrichment to obtain 17O- and 29Si-enriched UTL-derived zeolites. In situ and ex situ solid-state characterisation studies show that isotopic enrichment not only enables a more detailed spectroscopic investigation, but also provides new insights into the mechanism of the ADOR process and its sensitivity to experimental conditions. In the second part of this work, dry gel conversion synthesis and a novel steaming procedure are studied as cost-effective 17O-enrichment pathways for Al, Ga and Sc mixed-metal terephthalate MOFs. 17O solid-state NMR spectroscopy, in combination with PXRD and electron microscopy, is employed to investigate cation disorder and 17O NMR spectra are shown to be sensitive to substitution of metal centers and conformational changes upon interaction with guest molecules.

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No presente trabalho é apresentada a modelagem e solução numérica da convecção mista em cavidade aquecida por baixo com o topo deslizante, preenchida com meio poroso heterogêneo e homogêneo. Na abordagem heterogênea, o domínio do sólido é representado por blocos condutores de calor igualmente espaçados; a fase fluido circunda os blocos, limitada pelas paredes da cavidade. A abordagem homogênea ou poro-contínua é caracterizada através da porosidade e da permeabilidade da cavidade. As equações de conservação da massa, quantidade de movimento e energia são obtidas, adimensionalizadas e generalizadas de modo a representarem tanto o modelo contínuo quanto o poro-contínuo. A solução numérica é obtida através do método dos volumes finitos. As equações são discretizadas via esquema QUICK e é utilizado o algoritmo SIMPLE para o acoplamento pressão - velocidade. Visando o regime laminar, os parâmetros do escoamento são mantidos no intervalo de 102≤Re≤103 e 103≤Ra≤106 tanto para a abordagem heterogênea, quanto para a homogênea. Nas configurações testadas para o modelo contínuo, 9, 16, 36 e 64 blocos são considerados para cada combinação de Re e Ra e a porosidade microscópica é mantida constante φ=0,64 . No modelo poro-contínuo o número de Darcy (Da) é definido em função do número de blocos da cavidade heterogênea e da porosidade φ. Resultados numéricos do estudo comparativo entre a abordagem microscópica e a macroscópica são apresentados. Como resultado, correlações para o Nusselt médio para os modelos contínuo e poro-contínuo são obtidas em função do Ra modificado para cada Re. / In this work is presented mixed convection heat transfer inside a lid-driven cavity heated from below and filled with heterogeneous and homogeneous porous medium. In the heterogeneous approach, the solid domain is represented by heat conductive equally spaced blocks; the fluid phase surrounds the blocks being limited by the cavity walls. The homogeneous or pore-continuum approach is characterized by the cavity porosity and permeability. Generalized mass, momentum and energy conservation equations are obtained in dimensionless form to represent both the continuum and the pore-continuum models. The numerical solution is obtained via the finite volume method. QUICK interpolation scheme is set for numerical treatment of the advection terms and SIMPLE algorithm is applied for pressure-velocity coupling. Aiming the laminar regime, the flow parameters are kept in the range of 102≤Re≤103 and 103≤Ra≤106 for both the heterogeneous and homogeneous approaches. In the tested configurations for the continuous model, 9, 16, 36, and 64 blocks are considered for each combination of Re and Ra being the microscopic porosity set as constant φ=0,64 . For the pore-continuum model the Darcy number (Da) is set according to the number of blocks in the heterogeneous cavity and the φ. Numerical results of the comparative study between the microscopic and macroscopic approaches are presented. As a result, average Nusselt number equations for the continuum and the pore continuum models as a function of Ra and Re are obtained.