Les MOFs sont des matériaux hybrides (organiques/inorganiques), nanoporeux et cristallin. La périodicité et la porosité apportent à ces matériaux des propriétés modulables par la topologie des réseaux et par les interactions entre le réseau et les molécules qui peuvent pénétrer dans les nanopores. L'adsorption de molécules dans les pores permet les séparations de mélanges, la séquestration sélective de molécules, la catalyse, le stockage de l'énergie etc... La flexibilité de certains MOFs est caractérisée par des variations de volume, parfois extrêmes, pouvant modifier de manières significatives les propriétés de ces matériaux. L'eau est tout à la fois une impureté inévitable dans les usages pratiques de ces composés mais également un composant important dans la modulation de la flexibilité. Bien que les nombreuses études publiées offrent une vision globale de la flexibilité et des interactions mises en jeu lors de l'adsorption de molécules de différentes natures, l'eau reste cependant une de celles qui résistent le plus aux mesures et aux interprétations. Cette thèse a eu pour objet d'utiliser de façon conjointe la diffraction des rayons-X synchrotron, des neutrons et a résonance magnétique nucléaire (RMN), pour ré-investiguer le rôle de l'eau dans la flexibilité de deux MOFs archétypiques, le UiO-66 (ZrCDC) et le MIL-53(Al). Nos résultats ont permis d'éclairer plusieurs points critiques. Avec ZrCDC il a pu être montré qu'en présence d'eau, les deux briques de constructions, inorganique et organique, sont couplées tout en ayant chacune une flexibilité distincte. Pour MIL-53(Al), la réinvestigation a été notablement plus conséquente, reprenant le suivi de la flexibilité en température de la phase anhydre et sous l'influence des gaz composants de l'air, oxygène et azote, puis l’étude du rôle de l'eau par RMN qui permet de caractériser les modifications structurales et dynamiques des phases anhydre et hydratée. Le suivi progressif de l'adsorption et de la désorption a notamment permis de mettre en évidence des phénomènes d'échange protoniques lents responsables des hystérèses observés. Ces résultats permettent de remettre en perspective les études antécédentes et de proposer une description renouvelée de la flexibilité de ces composés, comme une "horlogerie cristalline" des mouvements moléculaires. / MOFs (metal-organic-frameworks) are hybrid (organic/inorganic) crystalline nanoporous materials. Periodicity and porosity provide to these materials modularity of properties by the topology of networks, and interactions between the framework and penetrating molecules in nanopores. Adsorption of molecules in pores allows for mixtures separation, selective sequestration of molecules, catalysis, storage of energy etc... Flexibility of some MOFs is characterized by extremes volume variations modifying properties of these materials. Water is at the same time an inevitable impurity in practical uses of such compounds and an equally significant component for modulation of flexibility. Although many published studies provide comprehensive views of the flexibility and interactions involved in the adsorption of molecules of different types, however water is one of those most resistant to measurements and interpretations. This thesis has been using jointly X-rays synchrotron and neutrons diffractions as well as nuclear magnetic resonance, to re-investigate water role on two archetypical MOFs, UiO-66 (ZrCDC) and MIL-53(Al). Our results obtained along this thesis shed some light on several critical points. With ZrCDC it has been demonstrated that both building blocks, inorganic and organic, exhibit each of them, in the presence of water a distinct flexibility, coupled together. For MIL-53(Al), this reinvestigation was noticeably more studied, covering flexibility in temperature of the anhydrous phase and under the influence of the components of air, oxygen and nitrogen. Then the study of water role in the anhydrous and hydrated phase by NMR characterized structural and dynamic changes. A progressive monitoring of adsorption and desorption, brought out slow proton exchange phenomena responsible of the hysteresis. These results allow for redefined a perspective of previous investigations and to propose a renewed description of flexibility of these materials, as a "crystalline clockwork" of molecular motions.

Limestone is a raw material in the cement and quicklime industry and knowledge about limestone characteristics can help improve and optimize production processes. In the end this can lead to a reduction in CO2 emissions from the industry. In this project X-ray tomography (XRT) was used to examine limestone samples. The aim was to determine if XRT, including synchrotron-based XRT, is a reliablemethod to determine porosity, pore structure and internal distributions of pores and pyrite (FeS2) grains in limestone. The aim also included to determine if XRT could be used to resolve material variations, fine-grained and larger crystals in limestone. In total, there were ten limestone samples and the performed XRT was done by Advanced Light Source (ALS) in Berkeley, California and by Luleå University of Technology. A brief comparison between ALS and Luleå was also done by inspectingsamples that have been through XRT at both facilities. The main software used foranalysis was Avizo v.9.2.0. The results showed that XRT is a suitable method for determining porosity and pore distribution. Interactive thresholding was used in Avizo for measuring porosity. The porosity was determined as a single value and as a narrow range, where a narrow range was more reliable. XRT was also found to be a suitable method for visually determining a variety of textures within the samples. Areas with different materials(such as dolomite) and/or newly-formed crystals were visually distinguishable but individual newly-formed crystals were not as clear when compared to scanning electron microscopy. Individual older fine-grained and larger crystals were hard to resolve. Internal distributions in 3D of both pores and pyrite grains were possible to obtain with XRT. The analysis of internal distributions was found to be a clear advantage with the method of XRT. The equivalent diameter of pores and pyrite grains was also measured and plotted in histograms. The XRT performed at ALS had higher resolution than the XRT performed in Luleå (0.65 vs 2 μm). Lower resolution over-estimated the average equivalent diameter of pores, and boundaries of pores and cavities were harder to see. Therefore, the higher resolution from ALS was preferable. These results contribute to understanding limestone characteristics.

The X-ray optics of synchrotron radiation beamlines are considered in this paper. The characteristics of synchrotron radiation which make it the premier source of light for studies in many regions of the electromagnetic spectrum are given. A chapter is devoted to the collimating, focusing and monochromating optics of two X-ray diffraction beamlines at the National Synchrotron Light Source. The beamlines are operated by the Naval Research Laboratory (NRL) and the Oak Ridge National Lab (ORNL). The major optical components of these beamlines are reviewed in regards to their function and their flexibility. A detailed analysis is performed on the NRL X-ray collimating mirror. The mirror is treated as an elastically bent beam. Deflection and slope error equations are developed which relate the shape of the bent mirror to its ideal surface. Visible light diffraction patterns collected from the mirror helped to establish operating conditions which provide good collimation. When the observed patterns are wed to the theoretical calculations, estimates of the average figure error are made. Finally, the effect of a highly collimated synchrotron beam on the reproducibility of the integrated intensities from polycrystalline materials is considered. The calculations show that except for the most fine grained materials, representative intensity measurements can only be made when the sample is permitted to move. / M.S.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Différentes techniques d'imagerie par contraste de phase des rayons X ont été récemment développées. Contrairement aux méthodes conventionnelles, qui mesurent les propriétés d'absorption des tissus, ces techniques donnent aussi le contraste du déphasage introduit par l'échantillon. Puisque le changement dans la phase peut être important même quand les différences en atténuation sont faibles ou absentes, le contraste d'image obtenable peut être considérablement augmenté, notamment pour les tissus mous biologiques. Ces méthodes sont donc très prometteuses pour une application dans le domaine médical. Cette Thèse a le but de contribuer à une compréhension plus profonde de ces techniques, en particulier la propagation-based imaging (PBI), la analyzer-based imaging (ABI) et la grating interferometry (GIFM), et d'étudier leur potentiel et la meilleure implémentation pratique pour les applications médicales. Une partie importante de cette Thèse est dédiée à l'utilisation d'algorithmes mathématiques pour l'extraction, à partir des images acquises, d'informations quantitatives (absorption, réfraction et diffusion) concernant l'échantillon. En particulier, cinq parmi les algorithmes les plus connus pour la technique ABI sont analysés théoriquement et comparés expérimentalement, dans les modalités planaire et tomographique, en utilisant des fantômes et des échantillons de tissu mammaire et d'os-cartilage. Une méthode semi-quantitative pour l'acquisition et la reconstruction d'images tomographiques dans les techniques ABI et GIFM est aussi proposée. Les conditions de validité sont analysées en détail et la méthode, permettant une simplification considérable de l'implémentation pratique, est vérifiée expérimentalement sur des fantômes et des échantillons humains. Enfin, une comparaison théorique et expérimentale des techniques PBI, ABI et GIFM est présentée. Les avantages et les désavantages de chacune des techniques sont mis en évidence. Les résultats obtenus par cette analyse peuvent être très utiles pour déterminer quelle technique est la plus adaptée à une application donnée.

No description available.

Osteocytes, the most abundant cell within bone, have been linked to the processes of mechanosensation and transduction. Based upon relatively limited empirical evidence, variations in their abundance and morphology have been linked to sex, age, biomechanics and disease. In order to better elucidate lacunar variation within a healthy cohort, samples from 30 women aged 20-86 and 36 men aged 18-92 were studied utilizing synchrotron radiation micro-CT. Initial studies of normal variation within the femoral proximal shaft cross-section found high variation in lacunar density (up to ~54%) and associated morphological differences linked to biomechanical regions. In women, a non-significant trend in lacunar density reduction was apparent with age; however, a significant reduction in lacunar volume with age (~30%) was observed. Also noted were differences in lacunar morphology, with the lacunae of younger women characterized as flatter and less equant than their older counterparts. The males, who demonstrated lacunar density decline with age and a tendency towards more equant and less elongate lacunae, did not share these characteristics. Intriguingly, the previously noted reductions in lacunar volume were not observed in males. The results of this research indicate that normal variation in osteocyte lacunar parameters is high. To our knowledge the observation that lacunar volume differs in women with age is novel, potentially resulting from preferential surface infilling within the extracellular space. The functional impact of this infilling is unclear but such a change in scale likely impacts the mechanosensing function of the osteocyte network. This hypothesis warrants further investigation as, if confirmed, it would represent a profound negative impact on the osteocyte network and may provide new insights into age-related bone loss.

Precessional dynamics are exploited in the operation of high frequency magnetic devices such as magnetic disk drives, non reciprocal microwave devices and spin transfer oscillators. The trajectory of the precession and its damping are of crucial importance. This thesis presents the characterisation of a variety of magnetic thin film structures performed with a range of phase sensitive techniques. It is possible to obtain new insight by utilising the chemical and site specificity of X-ray Magnetic Circular Dichroism (XMCD) to isolate the precession in different chemical species or at distinct sites in the crystal structure of a chosen material. X-ray Ferromagnetic Resonance (XFMR) combines XMCD and Ferromagnetic Resonance (FMR) phenomena in a technique capable of measuring the FMR response of an alloy or multilayer with both chemical and site specificity. To complement the XFMR technique a low temperature Time-Resolved Magneto Optical Kerr Effect (TR-MOKE) setup has been developed. This allowed for the characterisation of samples at temperatures in the range 4 K to room temperature. A frequency swept Vector Network Analyser FMR (VNA-FMR) setup was developed to allow for a fast method for determining the resonance condition and damping of a range of ferromagnetic thin film samples. In addition a TR-X-ray Photoemission Electron Microscopy (TR-XPEEM) setup has been established which allows images to be obtained with magnetic contrast. The combination of the above techniques has lead to studies on rare earth capped spin valve free layers and the measurement of spin pumping in industrially relevant spin valves.

The ionization and thermal balances are considered for a gas that is ionized by a dilute radiation field, taking into account the diffuse ionizing radiation produced by the gas. A number of models are constructed in which the electron temperature and the ionization of the elements H, He, C, N, 0, Ne, and Mg are determined for optically thin and optically thick gases ionized by ultraviolet synchrotron radiation under different conditions. Conclusions are then drawn about the general characteristics of ionization by synchrotron radiation. It is shown that, in an optically thin gas, because of the insensitive frequency- dependence of synchrotron radiation each element occupies a number of different stages of ionization at any one point in the gas. It is also shown that in an optically thick gas the heavy elements remain ionized to much greater distances from the source than hydrogen and helium, and that the gas becomes thermally unstable when H and He have become almost completely neutral. In addition, observations of the emission -line intensities of the Crab Nebula are compared with a model of this object. Considerable disagreement exists between the observed and predicted intensities, and possible reasons for the discrepancy are discussed.

Soft x-ray spectroscopy can provide a wealth of information on the electronic structure of solids. In this work, a suite of soft x-ray spectroscopies is applied to organic and inorganic materials with potential applications in electronic and energy generation devices. Using the techniques of x-ray absorption (XAS), x-ray emission spectroscopy (XES), and x-ray photoemission spectroscopy (XPS), the fundamental properties of these different materials are explored. Cycloparaphenylenes (CPPs) are a recently synthesized family of cyclic hydrocarbons with very interesting properties and many potential applications. Unusual UV/Visible fluorescence trends have spurred a number of theoretical investigations into the electronic properties of the CPP family, but thus far no comprehensive electronic structure measurements have been conducted. XPS, XAS, and XES data for two varieties, [8]- and [10]-CPP, are presented here, and compared with the results of relevant DFT calculations. Turning towards more application-centered investigations, similar measurements are applied to two materials commonly used in solid oxide fuel cell (SOFC) cathodes: La_(1−x)Sr_(x)MnO_(3) (LSMO) and La_(1−x)Sr_(x)Co_(1−y)Fe_(y)O_(3) (LSCF). Both materials are structurally perovskites, but they exhibit strikingly different electronic properties. SOFC systems very efficiently produce electricity by catalyzing reactions between oxygen and petroleum-based hydrocarbons at high temperatures (> 800 C). Such systems are already utilized to great effect in many industries, but more widespread adoption could be had if the cells could operate at lower temperatures. Understanding the electronic structure and operational evolution of the cathode materials is essential for the development of better low-temperature fuel cells. LSCF is a mixed ion-electron conductor which holds promise for low-temperature SOFC applications. XPS spectra of LSCF thin films are collected as the films are heated and gas-dosed in a controlled environment. The surface evolution of these films is discussed, and the effects of different gas environments on oxygen vacancy concentration are elucidated. LSMO is commonly used in commercial fuel cell devices. Here the resonant soft x-ray emission (RIXS) spectrum of LSMO is examined, and it is shown that the inelastic x-ray emission structure of LSMO arises from local atomic multiplet effects.