Structure and bonding properties of gold (Au) nanoparticles (NPs) are of great interest due to the unique size-dependent quantum-confinement effect exhibited by structures on the nanoscale. As such, Au NPs have demonstrated their potential use in a variety of fields (e.g. imaging, drug delivery, catalysis). The popularity of Au NPs is largely due to its versatility in synthesizing different NP compositions and surfaces. In this thesis, structure and bonding in Au NPs was examined from both surface functionalization/ligand and composition/metal bonding perspectives. Functionalization of Au-surface with model biomolecule ligands enables formation and electroless deposition of Au NPs onto a biocompatible Ti substrate. Through variation of model biomolecule size and concentration with respect to a Au precursor, insight was gained into the formation mechanisms of Au NPs, and the processes that lead to deposition upon the Ti substrate. Furthermore, using extended X-ray absorption fine-structure (EXAFS) with sample spinning and glancing angle setup allowed us to resolve small differences in coordination, leading to new findings on fine-tuning of peptide-coated Au NP size on Ti substrates. To explicitly analyze Au NP structure and bonding from a metallic perspective, NP model systems with precisely controlled compositions were studied with ab initio calculations to compare local environment and electronic character. It was determined that while surface features may be structurally similar, the effect of local environment and geometry can affect the electronic character of these features. Finally, small Au NP samples were studied to understand the alloying effect. The position of a heteroatom dopant Pt atom within Au25 has been a disputed issue, with no definitive means of determination. Using a combination of EXAFS spectra and ab initio calculations, it was possible to determine that the Pt atom resides in the central position of the icosahedral core. Furthermore, Pt doping in Au25 resulted in a contraction of the surface Au structure, an unobserved phenomenon until now. Through the careful and systematic comparison of Au NP systems, this thesis will contribute to a better understanding of Au local structure and bonding in ligand-functionalized substrate-supported Au NPs, as well as compositionally precise Au nanoclusters.

<p> Ceramic samples of Li2+xYxZr1-xO3 with x=0 to 0. 1, Li8+xYxZr1-xO6 with x=0 to 0.2, Li1-xYxZr1-xO2 with x=0 to 0.5 and Li1+xZrxY1-xO2+x with x=0 to 0. 3 were prepared via conventional solid reactions. The solubilities, crystal structures and microstructures in these samples were studied by x-ray diffraction(XRD), infrared spectra, differential thermal analysis(DTA) and scanning electron microscopy(SEM). The results show that the solubilities are 0.05≤X<0.1 for Li2+xYxZr1-xO3 and Li8+xYxZr1-xO6, 0.1≤x<0.15 for Li1-xYxZr1-xO2, and x≥0.3 for Li1+xZrxY1-xO2+x, respectively. The crystal structures of the solid solutions of Li2+xYxZr1-xO3 and Li8+xYxZr1-xO6 are the same as Li2ZrO3 and Li8ZrO6, respectively but the cell constants change slightly with x, while the structure of Li1-xYxZr1-xO2 and Li1+xZrxY1-xO2+x changes from monoclinic for pure LiYO2 (x=0) to tetragonal (x≥0.005). The sinterability of Li2ZrO3 improves greatly with yttrium additions to Li2ZrO3. </p> <p> The conductivities of the samples were measured by complex impedance spectroscopy and dc polarization. The results show that lithium conductivity in Li2+xYxZr1-xO3 samples increases slightly from 3.9x10^-6 to 5.0x10^-6 S/cm at 400°C as x increases from 0 to 0.05 and the corresponding conduction activation energy decreases slightly from 0.99 to 0.92 eV. Based on the effective medium theory, the conductivity increase in the solid solution was estimated to be 3% for x=0.05 compared with pure Li2ZrO3 crystal.</p> <p>For Li8+xYxZr1-xO6 samples, a mixture of LiOH and Li2CO3, which melts at about 430°C, can be formed during the processing and measurements. The ionic conductivity depends to a large degree on the microstructure(the amount and distribution of the mixture) below 430°C. The lithium conductivity at 435°C increases from 1.0x10^-2 to 6.9x10^-2 S/cm as x increases from 0 to 0.05. The electronic contribution to total conductivity is lower than 1% below 435°C.</p> <p> The ionic conductivity in the tetragonal phase of Zr-doped LiYO2 is much lower than in pure monoclinic LiYO2. The conductivity values at 500°C are 1.3x10^-2 for pure LiYO2 and 1.2x10^-4 for Li1.3Zr0.3Y0.7O2.3. The ionic conduction activation energy in the tetragonal Zr-doped LiYO2 is much higher than pure LiYO2.</p> <p> The thermal stability and the hydrolysis tendency for Li2ZrO3, Li8ZrO6 and LiYO2 were examined by thermodynamic calculations and by experiments.</p> / Thesis / Master of Engineering (MEngr)

<p> The properties of the levels of 21Ne and 29Si have been studied via γ-ray angular distribution and linear polarization measurements and γ-γ coincidence studies yielding a number of new spin-parity assignments to the states of both nuclei. Comparison of the results with the Nilsson model for odd nuclei indicate that for 21Ne, good agreement is in general obtained. Nevertheless, a number of interesting discrepancies exist with regard to the negative parity states of 21Ne and explanations have been proposed for some of these. The agreement is also quite good for 29Si with a calculation using a minimum of free parameters, confirming the oblate shape for this nucleus.</p> / Thesis / Doctor of Philosophy (PhD)

In this dissertation, the multiple facets of benzodithiophene (BDT) units are explored, with a focus on understanding how the isomerism of the BDT structure affects the macroscopic properties of the oligomeric and polymeric materials created. First, the story focuses on an overview of the BDT synthons and their applications in organic electronics. A straightforward synthesis of BDT and its derivatization to seven π-conjugated building blocks and seven polymers is presented. Then, symmetric (donor)2-acceptor (D2-A) dye architecture for application in dye-sensitized solar cells are investigated. Two isomeric systems are studied, and the branched sensitizers show a greater incident photon-to-current efficiency than the linear dyes. The nature of the accepting core is also varied between dibenzophenazine to dithienophenazine. The sensitizer with the weakest accepting core displays the best photovoltaic performance, due to an increase in the open-circuit voltage of ~100 mV caused by the favorable shift of the metal oxide conduction band. Lastly, a study of the donating building blocks in these (D2-A) sensitizers demonstrates that increasing the number of donor units from two to six thiophene moiety doubles the solar cell performance, due to the improvement of the light harvesting ability.

This work investigates the feasibility of the use of plasma spray deposition as a method of producing high performance polymer coatings. The work concentrates on the understanding of the processing of the plasma spraying of polymers, the behaviour of polymeric materials during deposition, and the study of process-structure-properties relationships. Processing modelling for the three stages of the evolution of a polymer deposit (droplet-splat-coating) has been carried out using heat transfer theory. A theoretical model is proposed which consists of three parts: the first part predicts the temperature profile of in-flight particles within plasma jet, the second part predicts the cooling of isolated splats impacting on a substrate and the third part, the heat transfer through the coating thickness. The heat transfer analysis predicts that the development of large temperature gradients within the particle is a general characteristics of polymers during plasma spraying. This causes difficulties for polymer particles to be effectively molten within the plasma jet without decomposition. The theoretical calculations have predicted the effect of processing parameters on the temperature, the degree of melting and decomposition of in-flight polymer particles. With the aid of the model, the conditions for the preparation of high integrity thermoplastic deposits have been established by the control of the plasma arc power, plasma spraying distance, feedstock powder injection, torch traverse speed and feedstock particle size. The optimal deposition conditions are designed to produce effective particle melting in the plasma, extensive flow on impact, and minimal thermal degradation. The experimental work on optimizing processing parameters has confirmed the theoretical predictions. Examination of polymer coating structures reveals that the major defects are unmelted particles, cracks and pores. Five major categories of pores have been classified. It also revealed a significant loss in crystallinity and the presence of a minor metastable phase in the plasma deposited polyamide coatings due to rapid solidification. The study has indicated that the molecular weight of a polymer plays an important role on the splat flow and coating structure. Under non-optimal deposition condition, substantial thermal degradation occurred for which a chain scission mechanism is proposed for plasma deposited polyamide coatings. There are difficulties in achieving cross-linking during plasma spray deposition of thermosets. The theoretical calculations predict that adequate cross-linking is unlikely in a coating deposited under normal conditions, but preheating the substrate to above the cross-linking temperature improves the degree of cross-linking of the coatings substantially. In addition, the coating thickness has a major effect on the degree of cross-linking of thermosets. The calculations also predict that lowering the thermal conductivity by applying a thermal barrier undercoat and using a faster curing agent to reduce time required for the cross-linking reaction can improve the degree of cross-linking of thermoset deposits. The experimental results for the degree of cross-linking and wear resistance confirmed these predictions.

No description available.

No description available.

Dans un contexte de développement durable, de nouvelles architectures macromoléculaires biosourcées et aromatiques ont été synthétisées à partir de deux types de ressources renouvelables : des tanins, issus du bois, et des glycérides, issus de végétaux ou de microalgues, afin de développer des matériaux pour des applications dans le bâtiment. Dans un premier temps, la réaction d’alkoxylation a été étudiée sur les tanins. Des chaînes de polyéther glycol (propylène et butylène) ont été greffées sur des tanins issus de différentes espèces botaniques aboutissant à l’obtention de divers macropolyols. A partir de ces macropolyols, des polyuréthanes (PUs) ont été synthétisés en modulant les paramètres réactionnels dans le but de contrôler les propriétés finales des matériaux pour répondre à des cahiers des charges. Des membranes d’étanchéité en PUs et des mousses rigides uréthane-isocyanurates d’isolation ont été élaborées. Enfin de l’huile algale ainsi que de l’huile de colza (comme référence) ont été modifiées en époxydes et polyols. Ces nouveaux synthons ont ensuite été incorporés dans la formulation de mousses uréthane-isocyanurates en vue d’étudier l’impact du type et du nombre de fonctions réactives sur les propriétés finales de mousses rigides à cellules fermées. Ces études ont permis d’analyser l’effet de l’addition de nouveaux synthons biosourcés et renouvelables dans des architectures et matériaux polymères. Le grand potentiel des tanins et des glycérides algosourcés pour l’élaboration de nouveaux matériaux performants pour des applications en particulier dans le domaine du bâtiment, a pu être largement démontré. / In a context of sustainable development, new biobased and aromatic macromolecular architectures were synthesized from two types of renewable resources: tannins, extracted from wood, and glycerides derived from plant or from microalgae to develop innovative materials for building applications. Firstly, the alkoxylation reaction was performed on tannins. Polyether glycol (propylene or butylene) chains were grafted on tannins extracted from different botanical sources species, resulting in various macropolyols with various controlled macromolecular architectures. Based on these macropolyols, polyurethanes were synthesized by varying the reaction parameters to control the final properties of materials to fit specific requirements. PU proofing membranes and rigid urethane-isocyanurate foams for insulation were elaborated. Finally, algal oil and rapeseed oil (as reference) were modified in epoxides and polyols. These new building blocks were incorporated in the structure of urethane-isocyanurates foams to study the impact of the type and the number of reactive functions on the final properties of rigid foams.New renewable bio-based building blocks were developed and integrated in the final macromolecular architectures and materials. The great potential of tannins and glycerides from microalgae for developing high-performance materials, for building applications, especially waterproofing membranes and insulation foams has been clearly established.

Les processus de lavage, et plus particulièrement l'utilisation de solutions chlorées, peuvent engendrer une dégradation prématurée des membranes de filtration d'eau. Alors que le marché des technologies membranaires en PVDF est en pleine expansion, peu de travaux portent sur l'étude de leur dégradation sur le long terme. Dans ce contexte, la thèse a porté sur l'étude du vieillissement de membranes de filtration commercialisées en PVDF. Les échantillons sont immergés dans une solution d'hypochlorite de sodium et l'effet du pH sur leur dégradation est approfondi. Les propriétés mécaniques, d'hydrophilie, les performances hydrauliques ainsi que la porosité sont étudiées. L'évolution des propriétés est mise en relation avec la structure chimique étudiée à différentes échelles : moléculaire, macromoléculaire et supramoléculaire. Cette approche n'a à ce jour jamais été utilisée dans le cas des membranes fibres creuses en PVDF. Les analyses en chromatographie d'exclusion stérique révèlent les modifications les plus importantes. La dégradation du PVDF des membranes se traduit par un phénomène prédominant de coupures de la chaîne principale du PVDF accompagné, dans une moindre mesure, d'un phénomène de réticulation. Les principales modifications sont constatées à des pHs inférieurs à 10 révélant la possible action conjointe des radicaux OH•, ClO• et Cl•. Le vieillissement d'une membrane PVDF additivée montre à la fois une dégradation du PVDF et une élimination des additifs. Alors que la membrane sans additif conserve une stabilité de ses propriétés, l'élimination des additifs entraine une évolution de la porosité et une propension au colmatage plus importante. Cependant, les membranes PVDF conservent des propriétés d'utilisation acceptables au regard des conditions extrêmes de vieillissement étudiées. / The cleaning processes, especially the use of chlorine solutions, may cause the untimely degradation of the water filtration membranes. While the market for PVDF membrane-based treatment technologies is rapidly expending, only few works deal with the study of their ageing on a long-term basis. In this context, this project focuses on the study of the ageing of two PVDF filtration membranes. Samples are immersed in a sodium hypochlorite solution and the effect of the chlorine solution pH is investigated. The properties of the membranes are characterized throughout the study by tensile tests, hydrophilicity, hydraulic performances and porosity analysis. The evolution of properties is related to the chemical structure of the membranes at a molecular, a macromolecular and a supramolecular scale. Until now, this approach has never been used in the case of PVDF membranes under chlorine conditions. The size exclusion chromatography analyses revealed the most important modifications. The degradation occurs mainly by chain scissions of the PVDF and crosslinking phenomenon in lesser extent. The main modifications occurred at pH less than 10 proving the joint action of OH•, ClO• and Cl• radicals. The ageing of the PVDF membrane containing additives showed at the same time the PVDF degradation and the elimination of the additives. Whereas the properties of the additive-free PVDF membrane were preserved, the elimination of additives led to a modification of the porosity and an increased fouling. However, even if the PVDF degradation is proved, the using properties of the PVDF membranes remain acceptable taking into consideration extreme conditions of ageing studied.

Les matériaux composites à matrice céramique (CMCs) à matrice auto-cicatrisantes (MAC) sont développées depuis plusieurs années pour leurs possibilités d'application dans le domaine de la propulsion aéronautique où ils se révèlent trés intéressants en termes de résistance à des conditions sévères et de légèreté. Dans le cadre d'un programme d'étude du comportement des CMC-MAC et de leurs mécanismes d'endommagement, l'objectif de ces travaux est de construire un modèle numérique multi-physique permettant de déterminer la durée de vie d'un échantillon d'un tel matériau soumis à une contrainte mécanique dans un environnement oxydant. L'étude porte sur la mise en place d'un couplage entre deux codes de calcul : un code d'endommagement mécanique et un code physico-chimique qui a été développé au cours de cette thèse. De façon inédite, on se place dans la géométrie 2D d'un plan de fissure, partant d'une image détaillée de l'arrangement des constituants (fibres, interphases, matrice multi-couche). Les différentes parties du programme ont été validées indépendamment et des résultats du calcul complet sont présentés et discutés. / Self-Healing Ceramics Matrix Composites (HT-CMC) are developed since several years for theirapplication in aeronautic applications and are interesting for their good resistance to criticalenvironments. As part of a study program of the HT-CMC behavior and their damagemechanisms, the objective of this thesis is to build a multi-physics numerical model todetermine the lifetime of a sample such a material subjected to a mechanical stress in anoxidizing environment. The study focuses on the establishment of a coupling between twocomputer codes: a code of mechanical damage and a physical-chemical code that wasdeveloped during this thesis. In an unprecedented way, we place ourselves in the 2D geometryof a crack plane, starting from a detailed picture of the arrangement of the components (fiber,interphase, multi-layer matrix). The different parts of the code have been independentlyvalidated and the results of the complete calculation are presented and discussed.