Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

This thesis deals with monitoring the durability of FRP reinforcement in different types of environments which cause degradation. The theoretical part of the thesis describes reinforcing fibers, matrix materials, manufacturing technology of composite reinforcements by pultrusion and durability of FRP materials in environmental degradation. In the experimental part of this thesis was carried storing samples reinforcements in alkaline environment with various temperatures. As suitable were selected temperatures of 20 °C, 40 °C and 60 °C. Subsequently are described changes in physical properties of the reinforcements and tracking optical microscope.

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This diploma thesis deals with the study of isothermal crystallization of nanocomposite materials based on isotactic polypropylene (iPP) and nanosilica, depending on the volume fraction (0, 2, 4 and 6 %) and type of silica and the crystallization temperature. Fumed silica and four types of silica with different surface treatment were used as filler. The crystallization performed at temperatures 136, 138, 140 and 142 °C has been studied in-situ using polarized optical microscope and the crystallization rate was evaluated from the growing radius of spherulites. It can be stated that particles of silica have been inbuilt into the spherulites due to the linear growth of spherulites of all composite materials. The most significant increase of the crystallization rate of iPP was caused by fumed silica, the most significant decrease was caused by silica TS-720 at volume fraction 4 %. The crystallization rate (G) has been slightly increased with the increasing volume fraction of filler at 136 °C, the G slightly decreased at 138 °C and there was no trend of G for two higher temperatures. Also, it was not possible to exactly evaluate the influence of the surface treatments. The reason is the most probably uneven (non-homogenous) distribution of nanosilica as revealed thermogravimetric analysis. The crystallization kinetics was evaluated according to the Lauritzen-Hoffmann theory. The morphological part of the study showed that iPP was in ? and ß-structure and spherulites of ? phase were of the type I, II and mixed.

The diploma thesis deals with the stability determination of model O/W (30/70) emulsions at 25°C. In fact, the time and emulsifier concentration (Tego Care PS) dependences of physical properties (aging) were monitored. In the second part of the work, the influence of conservant on emulsion stabilities were studied. In order to study physical properties of emusions rheometry, differential scanning calorimetry (DSC) and optical microscopy were employed. The rheological measurement provided information on viscosity and viscoelastic modulus. DSC experiments used the repeated freezing/thawing cycles which allowed monitoring of changes in crystallization temperature of water present in emulsions and melting enthalpy of ice formed during the cooling. The optical microscopy was used to examine the change in oil droplet size in the course of emulsion destabilization and phase separation. In this case the image analysis was carried out using program HarFA. The results showed that due to the emulsion creaming, the oil droplets diffuse and aggregate which causes phase separation. Those processes were quickest for the emulsion with lowest emulsifier concentration 0.1 % (destabilization during 51 days) The emulsions with emulsifier concentration about 1.5 and 1.3 % were stable at least for 4 months. The presence of the coemulsifiers increased the elastic modulus and descreased the phase difference due to the network formation. It was shown that for the stability determination is necessary to use conservant due to risk of microbial contamination. DSC experiments allowed to distingush samples prepared under different conditions. Lower rotational speed during emulsion preparation caused the appearance of two melting and crystalization peaks while for higher speed only one peak was observed.

This diploma thesis deals with study of crystalline structure of polyhydroxybutyrate (PHB), which contains different types of additives for studying of their nucleation activity and which were prepared by mixing. It is about boronitrid (BN), sacharin, hydroxapatit, plasticizer Tegmer a tree types of talc. Crystal structure was analysed by differential scanning calorimetry and x-ray diffraction, supramolecular structure was observed by optical microscopy (polarized and confocal laser scanning). Nucleating activity was evaluated by isothermal and non-isothermal crystallization made on calorimeter and heated table of optical microscope. There is not influence of additives on crystallographic structure, but additives affects number and size of spherulites including crystal domains defects, which can have impact on final mechanical properties. BN and talcs react as nucleating agents, other additives during low and high cooling speeds (vc) inhibit nucleation and in middle cooling speeds are without effect. Nucleating activity is not evaluated by numerically, because decrease of crystallization temperature together with vc is not linear. Results of direct methods are based on picture analysis, which is great benefit for understanding of crystal behaviour of PHB.

This thesis deals with monitoring of the durability of FRP reinforcements in alkaline environments with differing temperature exposures. The theoretical part of the thesis consists of a general description of the FRP composites, the manufacturing of these FRP reinforcements using pultrusion technology, the resistance of these composites in aggressive alkaline environments, and the influence of temperature on the speed and manner of degradation. In the experimental part of this thesis, the FRP reinforcements were placed in an alkaline environment tempered at different temperatures (20 °C, 40 °C, 60 °C). Subsequently, any optical physical changes of the reinforcements were described and evaluated by the use of optical microscopy and the destructive tests of these reinforcements.

La photocatalyse laisse entrevoir un large champ d’applications dans de nombreux domaines parmi lesquels figurent principalement ceux du traitement et de la purification de l’eau et de l’air. Ceci constitue une des raisons pour lesquelles les études fondamentales des processus de dégradation des molécules organiques à la surface des photocatalyseurs concernent le plus souvent les phases liquides et gazeuses. Les développements plus récents des applications de la photocatalyse dans le domaine des surfaces autonettoyantes ont soulevé des problématiques fondamentales concernant les mécanismes de dégradation photocatalytique de composés solides tels que les suies et les acides gras. Ces problématiques restent encore peu abordées dans la littérature malgré les enjeux majeurs en terme environnemental et méritent donc des travaux de recherche plus approfondis. Cette thèse porte sur l’étude des modes de dégradation photocatalytique de dépôts solides d’acide stéarique (AS) sur des couches minces de dioxyde de titane. Dans ce travail, des approches expérimentales originales basées sur la microscopie optique sont mises en œuvre pour suivre la dégradation photocatalytique de ces dépôts d’AS à l’échelle microscopique sous exposition à la lumière ultraviolette. Les dépôts d’AS se présentent sous forme d’îlots microscopiques présentant une distribution de taille et de forme. Sur la base d’un nouveau modèle cinétique que nous proposons, le lien existant entre la vitesse de dégradation photocatalytique du dépôt et la distribution de taille initiale de la population d’îlots est mis en évidence. Le modèle cinétique développé permet de rationaliser nos résultats et de concilier d’autres résultats, jusqu’alors contradictoires, de la littérature. Ce travail propose en outre une étude originale sur la dégradation photocatalytique de microcristaux d’AS déposés sur des couches minces de TiO2 microstructurées qui a permis d’appréhender le rôle des radicaux libres dans le processus de dégradation photocatalytique. La démarche expérimentale est basée sur le lien étroit existant entre l’orientation des molécules, inhérente à la structure propre des microcristaux, et les directions des plans cristallographiques {hkl}. Ainsi, nous mettons en évidence une dépendance en {hkl} des vitesses de dégradation des microcristaux qui est justifiée à l’échelle moléculaire par l’affinité des radicaux pour les terminaisons chimiques exposées selon ces plans cristallographiques / Photocatalysis is widely used in a variety of applications in water and air purification. For those reasons, fundamentals research on the photocatalytical degradation processes of organic compounds on photocatalysts surfaces concern in most cases liquid and gaseous phases. The more recent development of self-cleaning surfaces has raised several issues concerning the mechanisms of photocatalytic degradation of solid deposits such as soot or fatty acids. These issues remain little addressed in the literature and therefore deserve further attention. This thesis work deals with the study of the photocatalytical degradation modes of solid deposits of stearic acid (SA) on the surface of titanium dioxide thin films. In this work, an original experimental approach based on the use of optical microscopy is implemented to monitor, on a microscopic scale, the SA deposits as a function of UV light exposure. Viewed under microscope, the SA deposits appear as microscopic islands presenting size and form distribution. On the basis of a new kinetic model we propose, the existing relationships between the degradation rate of the deposit and the initial size distribution of the islands population is demonstrated. The proposed kinetic model rationalizes our experimental results as well as several others from the literature. Additionally, an original study on the degradation of SA microcrystals, grown on microstructured TiO2 thin films, provides insight into the role of the photogenerated oxygenated radicals in the photocatalytical mechanisms. Furthermore, the anisotropy of the microcrystals structure is put in relation with that of the SA molecules orientations within the microcrystal. This explains the observed {hkl}-dependence of the degradation rate of the microcrystals

Plasmons, i.e. collective oscillations of conduction electrons, have a strong influence on the optical properties of metal micro- and nanostructures and are of great interest for novel photonic devices. Here, plasmons on metal-dielectric interfaces are investigated using near-field optical microscopy and differential angular reflectance spectroscopy. Emphasis is placed on the study of plasmon interaction with individual nanostructures and on the nonlinear process of surface plasmon amplification. Specifically, plasmon transmission across single grooves in thin silver films is investigated with the help of a near-field optical microscope. It is found that plasmon transmittance as a function of groove width shows a non-monotonic behavior, exhibiting certain favorable groove widths with strongly decreased transmittance values. Additionally, evidence of groove-mediated plasmon mode coupling is observed. Spatial beating due to different plasmon wave vectors produces distinct interference features in near-field optical images. A theoretical approach explains these observations and gives estimated coupling effciencies deduced from visibility considerations. Furthermore, stimulated emission of surface plasmons induced by optical pumping using an organic dye solution is demonstrated for the first time. For this a novel twin-attenuated-total-reflection scheme is introduced. The experiment is described by a theoretical model which exhibits very good agreement. Together they provide clear evidence of the claimed process.

This thesis examines and exploits the optical properties of pairs of MNPs. Pairs of MNPs offer two further parameters not existent at single MNPs, which both affect the local optical fields in their vicinity: the distance between them, and their relative orientation with respect to the polarisation of the excitation light. These properties are subject of three chapters: One section examines the distance-dependent and orientation-sensitive scattering cross section (SCS) of two equally sized MNPs. Both near- and far-field interactions affect the spectral position and spectral width of the SCS. Far-field coupling affects the SCS even in such a way that a two-particle system may show both a blue- and redshifted SCS, depending only on the distance between the two MNPs. The maximum distance for this effect is the coherence length of the illumination source – a fact of importance for SCS-based experiments using laser sources. Another part of this thesis examines the near-field between two MNPs and the dependence of the locally enhanced field on the relative particle orientation with respect to the polarisation of the excitation light. To attain a figure of merit, the intensity of fluorescence light from dye molecules in the surrounding medium was measured at various directions of polarisation. The field enhancement was turned into fluorescence enhancement, even providing a means for sensing the presence of very small MNPs of 12 nm in diameter. In order to quantify the near-field experimentally, a different technique is devised in a third section of this thesis – scanning particle-enhanced Raman microscopy (SPRM). This device comprises a scanning probe carrying an MNP which in turn is coated with a molecule of known Raman signature. By manoeuvring this outfit MNP into the vicinity of an illuminated second MNP and by measuring the Raman signal intensity, a spatial mapping of the field enhancement was possible. / Diese Dissertation untersucht und nutzt die optischen Eigenschaften von Paaren von Metall-Nanopartikeln (MNP). MNP-Paare bieten gegenüber einzelnen MNP zwei weitere Parameter, welche beide auf das optische Nahfeld der zwei MNPs wirken: zum Einen der Abstand der zwei MNPs zueinander, zum Anderen die relative Ausrichtung des Paares bezüglich der Polarisation des anregenden Lichts. Diese Eigenschaften sind Thema der Arbeit: Ein Abschnitt untersucht den abstands- und orientierungsabhängigen Streuquerschnitt (SQS) zweier gleichgroßer MNPs. Die spektrale Position und die Breite des SQS wird von Wechselwirkungen sowohl im Nah- als auch im Fernfeld beeinflusst. Der Einfluß der Fernfeld-Wechselwirkung geht so weit, daß ein Zwei-MNP-System sowohl einen blau- als auch einen rotverschobenen SQS haben kann – dies hängt lediglich vom Abstand der zwei MNPs ab. Die Reichweite dieser Fernfeld-Wechselwirkung wird durch die Kohärenzlänge der Beleuchtungsquelle bestimmt – eine wichtige Tatsache für SQS-Untersuchungen, welche Laserquellen verwenden. Ein weiterer Teil der Dissertation untersucht das Nahfeld zwischen zwei MNPs. Insbesondere wird dargestellt, inwieweit die Überhöhung des Nahfelds von der Orientierung des Partikelpaares bezüglich der Polarisation des Anregungslichts abhängt. Um den Effekt quantifizieren zu können, wurde die Intensität der Fluoreszenz des umgebenden Mediums für verschiedene Polarisationsrichtungen gemessen. Die lokale Feldverstärkung konnte in eine Fluoreszenzverstärkung gewandelt werden, mit deren Hilfe sich sogar die Anwesenheit sehr kleiner MNPs von nur 12 nm Durchmesser nachweisen ließ. Wie Nahfeld-Intensitäten experimentell quantifiziert werden können, stellt ein dritter Abschnitt dieser Dissertation vor – per MNP-verstärkter Raman-Rastersonden-Mikroskopie. Diese Technik besteht aus einer Rastersonde, welcher ein MNP anheftet, welches wiederum mit einem Molekül bekannter Ramansignatur überzogen ist. Indem solch eine Sonde in die unmittelbare Nähe eines zweiten, beleuchteten MNPs gebracht wurde und dabei die Intensität des Raman-Signals aufgezeichnet wurde, ließ sich die räumliche Verteilung der Ramanverstärkung vermessen.