L’incorporation de fibres de carbone greffées avec des nanotubes de carbone (CNTs-CF) dansune matrice polymère permet d’obtenir des matériaux avec des propriétés mécaniques, des propriétés de conductivité électrique et de conductivité thermique notamment améliorées. Ces matériaux sont des candidats idéaux pour être intégrés dans des applications fonctionnelles et même structurales dans les domaines de l’industrie aéronautique, de l’industrie automobile, de la défense et de l’industrie des produits pour le sport. L’objectif (des travaux menés au cours) de cette thèse de Doctorat est d’établir une technique efficace de production de matériaux composites possédant des propriétés multifonctionnelles. Nous étudions l’adaptation d’une technique de dépôt de polymère par plasma sur la surface de fibres de carbone (CFs) puis sur la surface de CNT-CFs. Le dépôt de polymère par plasma sur la surface CNT-CFs est ici recherché non pour des raisons de sécurité, certainement avantageuses, mais pour conférer les propriétés des nanotubes de carbone à l’ensemble du matériau composite. Dans le premier chapitre, nous proposons un tour d’horizon des 2 sujets majeurs de notre étude : (1) les matériaux composites et leurs applications (2) les applications des plasmas pour procédés de traitement des matériaux. Dans le deuxième chapitre, nous présentons la procédure expérimentale du traitement plasma des fibres, ainsi que le schéma détaillé du mécanisme permettant de manipuler les échantillons. Nous précisons aussi les procédures suivies pour la caractérisation chimique, électrique et mécanique des fibres et des matériaux composites. Dans le troisième chapitre, nous évaluons les effets des variations de 2 et de 3 paramètres (par exemple la puissance plasma utilisée, la durée d’exposition et la nature des précurseurs) sur la résistivité électrique des fibres de carbone (CFs) et des fibres de carbone greffées de nanotubes de carbone (CNTs-CF) par la méthodologie des surfaces de réponse. D’après cette étude pour l’optimisation du procédé, nous étudions les principaux facteurs et les interactions entre les différents paramètres. Nous montrons les variables (ou facteurs) qui ont la plus grande influence sur la résistivité électrique sur les 2 types de fibres de carbone. Dans le quatrième chapitre, nous traitons des études de caractérisations des fibres de carbone par XPS (composition chimique), MEB (microstructure), AFM (topologie, rugosité) et TGA (stabilité thermique, cinétique de dégradation). Il s’agit de fournir une meilleure compréhension des structures obtenues sur de telles fibres dans des domaines allant du macroscopique jusqu’au niveau de l’atome. Nous analysons aussi des échantillons avant traitement pour comparer les différences morphologiques et chimiques avec les échantillons traités par plasma. Finalement, dans le cinqième chapitre, nous étudions les proprieties mécaniques et électriques des échantillons de matériaux composites élaborés à partir de fibres non-traitées et des fibres traitées par dépôt plasma de polypyrrole (sur CFs et CNTs-CF). A partir des essais mécaniques et des mesures électriques, nous concluons sur les améliorations apportées par le traitement plasma. / The incorporation of carbon nanotubes grafted carbon fibers (CNTs-CF) into polymermatrices provides highly-enhanced mechanical, electrical, and thermal properties to the materials. They are ideal candidates to be integrated into structural and functional applications in the fields of aerospace, automobile, defense, and sport industries. The aim of this PhD thesis is to establish an efficient technique to produce carbon fiber composites with multifunctional properties. We study the adaptation of a plasma technique for polymer deposition on the surface of carbon fibers (CFs) and carbon nanotubes grafted carbon fibers (CNTs-CF). The plasma polymer deposition on CNTs-CF is not performed only to keep nanotubes on the carbon fiber surface for safety reasons, but it is also applied to retain the bulk properties of those materials. In the first chapter, we give an overview of the two major subjects of the study: (1) composites and their applications, (2) plasma application for materials processing. In the second chapter, we present the experimental procedure of the plasma treatment process of fibers including the detailed design of the plasma system for the treatment of these samples. Then we explain the procedures of several sorts of characterization studies of fibers and composites (e.g. chemical, electrical, and mechanical). In the third chapter, we evaluate the effect of double and triple varied process parameters (i.e. plasma power, exposure time and precursors) on electrical resistivity of CFs and CNTs-CF by response surface methodology. According to the optimization studies we investigate the main factors and the interactions between the different process parameters and we demonstrate which variable (or factor) has the greatest effect on the electrical resistivity of both types of the treated carbon fibers. In the forth chapter, we deal with the characterization studies of the plasma treated CFs and CNTs-CF by using XPS (chemical structure), SEM (microstructure), AFM (topography, roughness), and TGA (thermal stability, degradation kinetics) in order to provide better understanding of the obtained structures on such fibers in a domain ranging from macroscopic to atomic scales. We also analyze the untreated samples to compare mainly the chemical and morphological differences between unmodified and plasma modified fibers. Finally, in the fifth chapter, we study the mechanical and electrical properties of untreated and plasma polypyrrole treated CFs and CNTs-CF reinforced composites experimentally. According to the electrical and mechanical tests, we determine the healing effect of plasma surface treatment performed on CFs and CNTs-CF.

Doctor of Philosophy / Department of Civil Engineering / Alok Bhandari / Aquifers are frequently contaminated by phenolic compounds from spills, leaking underground storage tanks, or landfills. These compounds can be toxic to a variety of organisms including humans. Their disposal is restricted in many countries with strict limits for acceptable concentrations in drinking water. Phenols that are chlorinated have significantly greater toxicity and are resistant to aerobic biodegradation. Enzyme-mediated in situ stabilization has been advocated as an approach for the treatment of phenolic compounds in soils and groundwater. This research investigated the applicability of a luminol-based chemiluminescence assay to monitor transport of horseradish peroxidase (HRP) enzyme in saturated porous media. The chemiluminescence assay was optimized by varying solution conditions such as the concentration of luminol, p-iodophenol, hydrogen peroxide, ionic strength and pH. All assay components were found to affect the maximum chemiluminescene intensity. The study also evaluated the ability of HRP to mediate the removal of phenol from solution by catalyzing its oxidative polymerization in simulated aquifer conditions. HRP behaved as a conservative tracer in the column packed with Ottawa sand. The concentration of phenol in the column effluent was found to decrease by nearly 90% in the presence of HRP and H2O2 in the continuous flow system. HRP mediated oxidative polymerization of phenols resulted in the production of soluble and insoluble oligomeric products. Modification of porous media caused by the deposition of phenol polymerization products was studied and the impact of media modification on subsequent transport of phenolic contaminants was evaluated using 2,4-dichlorophenol (2,4-DCP) as a probe solute. The pore volume of the porous media was reduced due to the deposition of insoluble phenolic oligomers. The transport behavior of 2,4-DCP showed that the contaminant was retarded in the modified porous media.

<p>An explosion in the growth of organic materials used for optoelectronic devices is linked to the promise that they have demonstrated in several ways: workable carrier mobilities, ease of processing, design flexibility to tailor their optical and electrical characteristics, structural flexibility, and fabrication scalability. However, challenges remain before they are ready for prime time. Deposition of these materials into ordered thin films requires that they be cast from solutions of organic solvents. Drawbacks of solution-casting include the difficulty of producing layered films without utilizing orthogonal solvents (or even with orthogonal solvents), the difficulty in controlling domain sizes in films of mixed materials, and the lack of parameter options used to control the final properties of thin films. Emulsion-based, resonant infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) is a thin film deposition technique that is demonstrated to provide solutions to these problems.</p><p>This work presents fundamental research into the RIR-MAPLE process. An investigation of the molecular weight of deposited materials demonstrates that emulsion-based RIR-MAPLE is capable of depositing polymers with their native molecular weights intact, unlike other laser deposition techniques. The ability to deposit multilayer films with clearly defined interfaces is also demonstrated by cross-sectional transmission electron microscopy imaging of a layered polymer/quantum dot nanocomposite film. In addition, trade-offs related to the presence of surfactant in the target, required to stabilize the emulsion, are articulated and investigated by x-ray diffraction, electrical, optical, and surface characterization techniques. These studies show that, generally speaking, the structural, optical and electrical properties are not significantly affected by the affected by the presence of surfactant, provided that the concentration within the target is sufficiently low. Importantly, the in-plane mobility of RIR-MAPLE devices, determined by organic field effect transistor (OFET) characterization, rivals that of spin-cast devices produced under similar conditions. </p><p>This work also presents results of emulsion-based RIR-MAPLE deposition applied to optical coatings (gradient-refractive index antireflection coating based on porous, multilayer films) and optoelectronic devices (organic photovoltaics based on the polymer, P3HT, and small molecule, PC61BM, bulk heterojunction system). The optical coating demonstrates that RIR-MAPLE is capable of producing nanoscale domain sizes in mixed polymer blends that allow a film to function as an effective medium relevant to devices in the visible spectrum. Moreover, bulk heterojunction organic photovoltaic (OPV) devices that require nanoscale domains to function effectively are achieved by co-deposition of P3HT and PC61BM, achieving a power conversion efficiency of 1.0%, which is a record for MAPLE-deposited devices. </p><p>Results of these studies illuminate unique capabilities of the RIR-MAPLE process. Multilayer films are readily fabricated to create true bilayer OPV structures. Additionally, true gradient thin films are created by varying the ratio of two materials, including two-polymer films and a film consisting of a polymer and a small molecule, over the course of a single deposition.</p> / Dissertation

The aim of this work was the development of a method for the generation of surface features on n-type silicon samples with deeply buried p-implants, in the form of heterogeneities aligned directly above the buried implants. This task was motivated by the realisation of a simpler process for the formation of superjunction transistors, which currently require the repeated creation of the same implantation structure over multiple steps of photolithography These lithography steps can be potentially replaced, if a suitable process for the self-alignment in accordance to the buried implants can be found. The work on this goal was separated into three parts: the analysis of samples for suitable surface properties, the generation of surface heterogeneities using such a property and the analysis of the mechanism for the used process of contrast generation. Within this doctoral thesis, a before unseen method of selective etching on silicon was discovered and investigated. Hence, the overall aim of this work was successfully achieved. • Samples containing buried p-implants inside a n-type silicon substrate were characterised with regard to various properties. Of these, the through-sample resistance showed a significant variation in accordance to the buried implants also through a homogeneous epitaxial layer. • Various methods aimed at the usage of the resistance variation in order to generate a surface heterogeneity through electrodeposition failed to enable a suitable process. Instead, another method was found, which enables the replication of the implant structure via selective etching. This novel process enables the lithography free patterning of the substrates through a simple alkaline etch process performed under illumination. This results in a surface heterogeneity as an alteration of the sample topography combined with a material contrast due to the formation of an in-situ SiO2 etch mask. This material variation can also be used for the selective deposition of polymers, enabling further processing of the etched samples. • For this new method, named Light Induced Selective Etching (LISE), a mechanism underlying the selectivity was proposed and through a number of experiments. In essence, the illumination during the etching process produces a flux of photogenerated electrons directed from the buried implants toward the surface, which increase the negative surface charge in the areas above these implants. The locally increased surface charge causes a local protection of the native silicon oxide layer against the alkaline etching, leading to the structuring of the substrate. In essence, this novel method allows for the previously unreported self-adjusted structuring of silicon based on deeply buried implant structures. In general, even the characterisation of such implant structures is difficult, whereas this method allows for structuring with regard to such buried structures with a very simple setup of only an etchant solution and a suitable light source. With regard to the introduction and motivation of this thesis, this process can possibly be applied for the intended purpose of creating a self-aligned resist in order to replace repeating lithography steps. This is the case in particular in combination with polymer deposition, as shown in the last part of the results. Certain limitations, such as the resolution limit and dimensional size increase exist, but can be circumvented by appropriate device design and further optimisation of the process parameters. Furthermore, the LISE process appears applicable for the manufacturing of MEMS and MOEMS devices, as the typical feature sizes in these cases fit well to the achieved resolution of the LISE process. For devices needing a certain implant structure in combination with a corresponding topography, the new method allows for the elimination of at least one lithography step, including the necessary substeps such as alignment and measurement. Accordingly, LISE has the potential of simplifying the manufacturing process, enabling better and cheaper devices.