The productivity of most gas condensate wells is reduced significantly due to condensate banking when the bottom hole pressure falls below the dew point. The liquid drop-out in these very high rate gas wells may lead to low recovery problems. The most important parameter for determining condensate well productivity is the effective gas permeability in the near wellbore region, where very high velocities can occur. An understanding of the characteristics of the high-velocity gas-condensate flow and relative permeability data is necessary for accurate forecast of well productivity. In order to tackle this goal, a series of two-phase drainage relative permeability measurements on a moderate permeability North Marmara &ndash / 1 gas well carbonate core plug sample, using a simple synthetic binary retrograde condensate fluid sample were conducted under reservoir conditions which corresponded to near miscible conditions. As a fluid system, the model of methanol/n-hexane system was used as a binary model that exhibits a critical point at ambient conditions. The interfacial tension by means of temperature and the flow rate were varied in the laboratory measurements. The laboratory experiments were repeated for the same conditions of interfacial tension and flow rate at immobile water saturation to observe the influence of brine saturation in gas condensate systems. The laboratory experiment results show a clear trend from the immiscible relative permeability to miscible relative permeability lines with decreasing interfacial tension and increasing velocity. So that, if the interfacial tension is high and the flow velocity is low, the relative permeability functions clearly curved, whereas the relative permeability curves straighten as a linear at lower values of the interfacial tension and higher values of the flow velocity. The presence of the immobile brine saturation in the porous medium shows the same shape of behavior for relative permeability curves with a small difference that is the initial wetting phase saturations in the relative permeability curve shifts to the left in the presence of immobile water saturation. A simple new mathematical model is developed to compute the gas and condensate relative permeabilities as a function of the three-parameter. It is called as condensate number / NK so that the new model is more sensitivity to temperature that represents implicitly the effect of interfacial tension. The new model generated the results were in good agreement with the literature data and the laboratory test results. Additionally, the end point relative permeability data and residual saturations satisfactorily correlate with literature data. The proposed model has fairly good fitness results for the condensate relative permeability curves compared to that of gas case. This model, with typical parameters for gas condensates, can be used to describe the relative permeability behavior and to run a compositional simulation study of a single well to better understand the productivity of the field.

A functional nanometer-scale hybrid coating layer with multi-walled carbon nanotubes (MWCNTs) and/or nanoclays, as mechanical enhancement to ‘heal’ surface microcracks and environmental barrier layer is applied to alkaliresistant glass (ARG) fibres. The nanostructured and functionalised traditional glass fibres show both significantly improved mechanical properties and environmental corrosion resistance. Early warning material damage can be achieved by carbon nanotubes concentrated interphases in the composites. / Eine funktionale nanometerskalige Hybridbeschichtung mit multi-walled carbon nanotubes (MWCNTs) und/oder Nanoclay wurde als mechanische Verbesserung des „Ausheilens“ von Oberflächen-Mikrorissen und Barriereschicht gegenüber Umwelteinflüssen auf alkaliresistente Glasfasern (ARG) appliziert. Die nanostrukturierten und funktionalisierten traditionellen Glasfasern zeigen signifikant verbesserte mechanische Eigenschaften und Korrosionsbeständigkeit. Die Frühwarnung des Materialversagens kann durch Carbon Nanotubes, konzentriert in der Grenzschicht der Composites, erreicht werden.

Es werden die Gleichgewichtskonstanten der Zinkextraktion ermittelt. Das Wilson-Modell und das erweiterte Debye-Hückel-Gesetz werden zur Beschreibung der Aktivitäten verwendet. Die tensiometrischen Untersuchungen erfolgen am hängenden Tropfen. Die Modellauswahl zur Beschreibung der Gleichgewichtsgrenzflächenspannung erfolgt im submizellaren Konzentrationsbereich. Die pseudo-nichtionische Modellierung auf der Basis der Langmuir-Isothermen der Mehrkomponentenadsorption bei Verwendung der Stern-Isothermen für die Gegenionenanreicherung liefert die beste Datenanpassung. Durch ein einfaches Modell zur Mizell- und Aggregatbildung gelingt die Modellerweiterung. Die gemessenen dynamischen Grenzflächenspannungskurven werden sorptionskinetisch und durch diffusive Approximationen angepasst. Es zeigt sich, dass der Stofftransport diffusionsdirigiert ist. Am oszillierenden Tropfen werden die Ergebnisse bestätigt. Für das Kationenaustauscheranion wird die Gültigkeit des Maxwell-Modells zur Beschreibung der Grenzflächendilatationsrheologie nachgewiesen.

This study illustrates the ability of SWNT to nucleate and template polymer crystallization and orientation, and produce materials with improved properties and unique polymer morphologies. This research work focuses primarily on the physical interaction between single-wall carbon nanotubes (SWNT) and the flexible polymer system polyvinyl alcohol (PVA). Polymer crystallization in the near vicinity of SWNT (interphase) has been studied to understand the capability of SWNT in influence polymer morphology in bulk films and fibers. Fibrillar crystallization was achieved by shearing PVA/SWNT dispersions and resulted in the formation of oriented PVA/SWNT fibers or ribbons, while PVA solutions produce unoriented fibers. PVA single crystals were grown in PVA solutions as well as PVA/SWNT dispersions over a period of several months at room temperature (25 C). PVA single crystal growth in PVA/SWNT dispersions is templated by SWNT, and these crystals show the presence of new morphologies for PVA. PVA single crystals of differing morphology were also grown at elevated temperatures, and show morphology dependant electron beam irradiation resistance. Gel-spinning was used to produce PVA, and PVA/SWNT fibers where, PVA crystallization in the bulk fiber was observed. With 1 wt% SWNT loading in PVA, the fiber tensile strength increased from 1.6 GPa for the control PVA to 2.6 GPa for PVA/SWNT. Analysis of this data suggests stress of up to ~120 GPa on the SWNT. This is the highest reported stress on the SWNT to date and confirm excellent reinforcement and load transfer of SWNT in the PVA matrix. Raman spectroscopy data show high SWNT alignment in the fiber where the ratio is measured to be 106. High-resolution transmission electron microscopy (HR-TEM) is used to characterize polymer morphology near the polymer-SWNT interface for PVA/SWNT fibers. HR-TEM studies of Polymer/CNT composites show distinct morphological differences at the polymer-SWNT interface/interphase for semi-crystalline and amorphous polymer systems which may be related to polymer-SWNT interaction in the composite. Studies on polymer crystallization, carbon nanotube (CNT)/polymer composite, and polymer composite interfacial literature in summarized in Chapter 1. Fibrillar crystallization of PVA and PVA/SWNT is presented in Chapter 2. PVA single crystal grown at varying temperatures is discussed in Chapter 3, followed by single crystal growth studies in PVA/SWNT dispersions in Chapter 4. Chapter 5 summarizes the gel-spinning studies of PVA and PVA/SWNT fibers. Conclusions and recommendations for future work pertaining to this study are given in Chapter 6. Results of HR-TEM studies on other polymer/SWNT composites are given in Appendix A, Appendix B summarizes work on PE crystallization in the SWNT/DMF dispersions, and studies of PVA and PVA/SWNT gel films are summarized in Appendix C.

The present work was undertaken to develop a composite osmotic distillation (OD) membrane consisting of a thin hydrogel coating on a microporous hydrophobic substrate for the concentration of aqueous feeds containing surface-active agents. The range of OD applications using the hydrophobic membrane alone have been severely limited by the propensity for membrane wet-out when contacted by amphiphilic agents such as oils, fats and detergents. Wet-out allows the feed solution to track freely through the membrane pores with a resulting loss of solutes and a decrease in selectivity. The rationale for the approach taken was based on the hypothesis that the high water selectivity of the hydrophilic coating would maintain good water mass transfer to the underlying hydrophobic substrate but exclude other components including surface-active agents. The first stage of this work involved the identification of potential coating materials and the fabrication and structural characterization of films of these materials to determine their suitability. The second stage involved the development of techniques to facilitate adhesion of the hydrophilic coatings to the hydrophobic substrate, and the testing of the resulting composite membranes for OD performance and resistance to wet-out by surface-active agents. Sodium alginate was selected as the major coating component on the basis of its non-toxicity and its potential for stable hydrogel formation. Structural characterization of noncrosslinked films and films crosslinked using a water-soluble carbodiimide (WSC) was carried out using differential scanning calorimetry (DSC), Fourier Transform infrared spectroscopy (FT-IR) and swelling measurements. Maximum crosslinking through esterification of hydroxyl and carboxylic acid groups on adjacent polymer strands using the film immersion method was achieved with a non-solvent (ethanol) concentration of 60 vol % and a WSC concentration of 100 mM at pH 4. These conditions resulted in a hydrogel with an equilibrium water content of 60 wt %. DSC measurements of noncrosslinked and crosslinked alginate films showed an increase in crystallinity and hence rigidity on crosslinking. Therefore, several coatings were prepared as blends of sodium alginate and amorphous highly flexible carrageenan gum in order to meet the flexibility requirements of a membrane subjected to varying operating pressures in an industrial OD plant. Structural characterization with respect to polymer blend ratio was carried out using scanning electron microscopy (SEM), DSC, X-ray diffraction (XRD). The optimisation for crosslinking conditions was undertaken as for sodium alginate alone. Optimum conditions for film preparation were 20 wt % carrageenan content and a crosslinking medium containing 60 vol % non-solvent (ethanol) and 120 mM WSC at pH 4. These conditions produced a hydrogel with an equilibrium water content of 85 wt %. Two different techniques were employed to anchor the coatings on substrate PTFE membranes. For membranes with a nominal diameter of 0.2 µm, the technique involved surface tension adjustment of the coating solution by ethanol addition in order to enhance penetration of the coating solution meniscus into the substrate pores. This was followed by polymer precipitation by the selective removal of water using OD to provide structural interlocking. T-peel strength measurements showed that this technique resulted in a ten-fold increase in adhesion strength when compared with a coating cast without surface tension adjustments. For membranes with a nominal diameter of 0.1µm, an interfacial bonding agent, myristyltrimethylammonium bromide (MTMA), was used. This technique gave a three-fold increase in adhesion strength relative to that of coating cast without the use of MTMA. The composite membranes were tested in extended OD trials using pure water and feeds containing limonene, the major surface-active components of orange oil. The sodium alginate-carrageenan blend membrane, which was the preferred membrane based on flexibility and water sorption considerations, was also tested against full-cream milk and an industrial detergent, sodium dodecylbenzene sulfonate (DBS). The results indicated that the coatings offered little resistance to water transport and were effective in providing protection against membrane wet-out. Durability trials showed that the composite membranes retained their integrity in water for a minimum of 30 days. Overall, this study has expanded the potential applications of OD to include many important industrial concentration steps that are currently being undertaken by conventional processes with unsatisfactory results. These include the concentration of citrus juices, full-cream milk and nuclear power plant liquid waste. These feeds contain limonene, fats and detergents respectively, all of which wet out unprotected hydrophobic membranes.

De nos jours, l'industrie microélectronique utilise des fréquences de fonctionnement plus élevées dans les composants commercialisés. Ces fréquences entraînent des températures de fonctionnement plus élevées et limitent donc l'intégrité et la durée de vie des composants électroniques. Cependant, les besoins actuels nécessitent des dispositifs miniaturisés et de haute densité de puissance. De ce fait, la dissipation thermique dans les composants microélectroniques s’avère capitale. Ainsi, des drains thermiques sont utilisés pour évacuer la chaleur produite par le fonctionnement du composant. Les drains thermiques actuels sont composés de métaux, tels que le cuivre et l’aluminium, présentant des conductivités et des coefficients de dilatation thermiques élevés. Néanmoins, les coefficients de dilatation thermique des différents matériaux présents dans un circuit peuvent induire des contraintes thermo-mécaniques aux interfaces et engendrer une défaillance des composants après plusieurs cycles de fonctionnement. Dans ce contexte, nous proposons de remplacer ces drains métalliques par un système composite à matrice cuivre renforcée par du carbone, sur lequel est déposé un diffuseur thermique sous forme de diamant. Ces composites Cu/C présentent des propriétés thermo-mécaniques adaptatives pouvant palier aux contraintes induites durant l’utilisation des composants. Le transfert optimal des propriétés dans les MMC est souvent compromis par l'absence de liaison chimique interfaciale, en particulier dans les systèmes non réactifs telsque Cu/C. Cependant, pour un assemblage thermiquement efficace, l'interface devrait permettre un bon transfert de charges thermo-mécaniques entre les matériaux. L'objectif de cette étude est de combiner les propriétés exceptionnelles du diamant et les propriétés thermo-mécaniques adaptatives des MMC. Les composites à matrice de cuivre renforcés au carbone sont synthétisés à l'aide d'un processus dit semi-liquide pour obtenir des gradients de composition et des propriétés optimisées d'interface matrice - renfort. Par conséquent, des éléments d'alliage sont insérés dans le matériau pour former des interphases de carbure à l'interface Cu/C. Le film mince de diamant est obtenu par dépôt chimique en phase vapeur assisté par laser. Cette méthode de dépôt permet d’agir sur la qualité du film ainsi que sur l’adhésion avec le substrat composite. Finalement, une importance particulière est portée à l’influence des interfaces sur les propriétés thermiques tant au sein du matériau composite (interface matrice – renfort), qu’au sein de l’assemblage film diamant – MMC.Ces travaux ont été menés dans le cadre d’un accord franco-américain de cotutelle de thèse entre l’Institut de Chimie de la Matière Condensée de l’Université de Bordeaux, en France, et le département d’Ingénierie Electrique de l’Université du Nebraska-Lincoln, aux Etats-Unis. Ils ont été financés, en France, par la Direction Générale de l’Armement (DGA), et par l’équivalent Américain aux Etats-Unis. / Today, the microelectronics industry uses higher functioning frequencies in commercialized components. These frequencies result in higher functioning temperatures and, therefore, limit a component’s integrity and lifetime. Until now, heat-sink materials were composed of metals which exhibit high thermal conductivities (TC). However, these metals often induce large coefficient of thermal expansion (CTE) mismatches between the heat sink and the nonmetallic components of the device. Such differences in CTEs cause thermomechanical stresses at the interfaces and result in component failure after several on/off cycles.To overcome this issue, we suggest replacing the metallic heat sink materials with a heat-spreader (diamond film) deposited on metal matrix composites (MMCs), specifically, carbon-reinforced copper matrices (Cu/C) which exhibit optimized thermomechanical properties. However, proper transfer of properties in MMCs is often compromised by the absence of effective interfaces, especially in nonreactive systems such as Cu/C. Therefore, the creation of a chemical bond is ever more relevant. The goal of this research was to combine the exceptional properties of diamond by means of a thin film and the adaptive thermomechanical properties of MMCs. Carbon-reinforced copper matrix composites were synthesized using an innovative solid-liquid coexistent phase process to achieve designed composition gradients and optimized matrix/reinforcement interface properties. In addition, the lack of chemical affinitybetween Cu and C results in poor thermal efficiency of the composites. Therefore, alloying elements were inserted into the material to form carbide interphases at the Cu/C interface. Their addition enabled the composite’s integrity to be optimized in order to obtain thermally efficient assemblies. The diamond, in the form of a thin layer, was obtained by laser-assisted chemical vapor deposition. This process allowed action on the film’s phase purity and adhesion to the substrate material. Of particular importance was the influence of the interfaces on thermal properties both within the composite material (matrix-reinforcement interface) and within the diamond film-MMC assembly. This work was carried out within the framework of a Franco-American agreement between the Institute of Condensed Matter Chemistry of the University of Bordeaux in France and the Department of Electrical Engineering at the University of Nebraska-Lincoln, in the United States. Funding, in France, was provided by the Direction Générale de l’Armement (DGA), and by the American equivalent in the United States.

Le carbure cémenté (WC-Co) est un système biphasé constitué de grains de carbure de tungstène enrobés dans un liant à base de cobalt. Dans ce matériau composite, qui allie donc la dureté du carbure à la résilience du cobalt, la maîtrise de la microstructure est un paramètre clef pour l’optimisation des propriétés mécaniques.Le but de ce travail est de mettre au jour les mécanismes régissant le développement des joint de grain et des joints de phase lors du frittage. L’effet de la teneur en liant, du taux de carbone et du temps de frittage ont été particulièrement étudiés.Ce travail est basée sur la caractérisation du matériau par EBSD (Electron BackScattered Diffraction), une méthode qui facilite la séparation des grains et donc l’utilisation de techniques d’analyse d’image pour étudier la microstructure. En outre un programme basé sur les données d’orientation des grains collectées par EBSD et permettant l’analyse de la texturation des joints de grain et des joints de phase a été développé pour cette étude.L’étude de la contiguité montre qu’elle ne dépend pas du taux de frittage ni de la teneur en carbone du liant, mais essentiellement de la fraction volumique de liant. Cela implique que l’encombrement et l’imbrication des particules sont les principaux paramètres entrant en compte dans l’établissement de la contiguité. Un grossissement plus rapide et plus marqué a été observé dans les échantillons riches en carbone, ainsi que dans ceux présentant un fort taux de liant. Un grossissement anormal a été observé dans les échantillons riches en carbone et à fort taux de liant. La désorientation aux joints de grains est caractérisée par un couple axe/angle décrivant la rotation liant les deux cristaux. L’étude de la distribution des axes a révélé que trois rotations sont particulièrement abondantes : celles autour de [101 ̅0], [21 ̅1 ̅0] et [0001]. Elles représentent environ 30% de la surface totale des joints de grains. Pour chacune des rotations particulières ont été détectées : [101 ̅0]/90°, [21 ̅1 ̅0] / (48°- 60°- 90°) et [0001]/90°. L’étude de la géométrie de ces joints suggère que leur remarquable stabilité est due au fort taux de cohérence dans le plan de joint. L’analyse statistique des plans de joint de grain et de joint de phase montre que la plupart d’entre eux correspond à un plan basal ou prismatique pour au moins l’un des deux grains (70% environ de la surface totale de joint de grain, et 50% environ de la surface totale de joint de phase). Sur la base de ces résultats, un scénario décrivant l’évolution de la microstructure durant le frittage est finalement proposé. / WC-Co cemented carbide is a two phase system constituted of a cobalt based binder matrix embedding hard tungsten carbide grains. This material is especially used in fields such as metal cutting or mining, where high mechanical properties are required. Therefore, the microstructure is a key parameter to control to optimize the mechanical properties of the alloy.This work aims at understanding the mechanisms of grain boundary and phase boundary development during sintering, and how they may influence the final microstructure. The effect of the binder content, carbon content and sintering time was especially investigated.Electron BackScattered Diffraction characterization was chosen to conduct this study. First because the precise separation of grains in the resulting images makes possible automation of the measurements, and thus allows a statistical analysis of several microstructural parameters (as grain size, contiguity) on numerous samples. Secondly because orientation data collected by this way make possible the analysis of grain boundary and phase boundary texture. To this end, an automated method was developed for analysis of grain boundaries and estimation of remarkable boundary planes fraction from 2D EBSD measurements.The study of contiguity shows that it does not depend on sintering time or carbon content in the binder, but essentially of the carbide grain volume fraction. This result implies that impingement is the first order parameter in the evolution of contiguity. Grains appear to grow faster and in a larger extent in samples with a carbon rich binder, as well as in high binder content samples. Abnormal grain growth seems to be favored by high binder content in carbon rich samples. All grain boundaries were characterized by a couple of rotation axis and misorientation angle. Three particular rotation axes were identified: [101 ̅0], [21 ̅1 ̅0] and [0001]. They represent around 30% of the total grain boundary surface area. In addition, specific rotations were found to be particularly abundant in the microstructure: [101 ̅0]/90°, [21 ̅1 ̅0] / (48°- 60°- 90°) and [0001]/90°.A study of their geometry suggests that their stability would be due to a particularly coherent boundary plane. A statistical analysis shows that most grain boundaries and phase boundaries have a habit plane parallel to a basal or prismatic plane (about 70% of the total grain boundary surface area and 50% of the total phase boundary area. Finally, a scenario is proposed for the microstructure development model during sintering of cemented carbides on the basis of the results.

The study of materials composed from the combination of chitosan and silver nanoparticles has attracted the interest of researchers from different areas due to large variety of applications of these systems, such as the development of electro-optical devices and the disease treatment like cancer. Despite the existence of several works devoted to the characterization of the biological activity of these materials, many physical properties have not been explored so far. In this work, we study thermo-optical, interfacial and morphological properties of fluids and lms based on chitosan, by considering the effects associated with the addition of silver nanoparticles. Using a large variety of experimental techniques, it is investigated how the concentration of silver nanoparticles modifies the heat diffusion, fluid adhesion and photodegradation process in chitosan samples. From the time-resolved z-scan measurements in solution of chitosan and silver nanoparticles, it is studied how the heat transport induced by the visible radiation is modifed by the insertion of the metallic nanoparticles. Our results show that thermo-optical coefficient and thermal diffusivity are sensible to the variation of colloids concentration. With respect to morphological properties of chitosan film doped with silver nanoparticles, it is observed that the introduction of guest particles tends to modify the superficial structure of the films, with the formation large clusters of nanoparticles. In relation to interfacial properties associated with wetting phenomenom, it is observed a non-monotonic behavior of the contact angle of castor oil droplets as the silver nanoparticles concentration is increased. The parameters related to wetting phenomenon are computed from the analysis of time-evolution of the droplet spreading, by using a molecular-kinetic theory. Further, the effects of silver concentration on the photodegradation of chitosan films are examined, when the films are exposed to the electromagnetic radiation in the visible and ultraviolet regions. The present results reveal that the photodegradation process of the films depends on the radiation wavelength and the used excitation regime. / O estudo de materiais formados pela associação da quitosana a nanopartículas de prata tem atraído a atenção de pesquisadores de diferentes áreas devido à grande variedade de aplicações destes sistemas, tais como a fabricação de dispositivos eletro-ópticos e o tratamento de doenças como câncer. Apesar da existência de inúmeros trabalhos voltados à caracterização da atividade biológica destes materiais, diversas propriedades físicas ainda não foram devidamente caracterizadas. Neste trabalho, estudaremos as propriedades termo-ópticas, interfaciais e morfológicas de fluidos e filmes baseados em quitosana, considerando os efeitos associados à adição de nanopartículas de prata. Usando uma grande variedade de técnicas experimentais, é investigado como a concentração de nanopartículas de prata altera os processos de difusão de calor, de adesão à fluidos e de fotodegradação nas amostras de quitosana. A partir de medidas de varredura Z resolvida no tempo em soluções de quitosana e nanopartículas de prata, é averiguado como o transporte de calor induzido pela radiação visível incidente é modificado pela inserção da nanopartículas metálicas. Nossos resultado mostram que o coeficiente termo-óptico e a difusidade térmica são sensíveis à variação da concentração de nanopartículas de prata. No que diz respeito às propriedades morfológicas de filmes de quitosana dopada com nanopartículas de prata, é observado que a introdução das partículas hóspedes tende a transformar a estrutura super cial dos lmes, com a formação de grandes aglomerados de nanopartículas. Com relação as propriedades de interfaciais associadas ao fenômeno de molhagem, é observado um comportamento não-monotônico do ângulo de contato de gotículas de óleo de mamona, à medida que a concentração de nanopartículas aumenta. Os parâmetros associados ao fenômeno de molhagem são calculados a partir da análise da evolução temporal do espalhamento das gotas, usando a teoria cinética-molecular. Além disso, os efeitos da concentração de nanopartículas sobre a fotodegradação dos filmes de quitosana dopada são verificados, quando submetidos à radiação eletromagnéticas nas regiões do visível e ultravioleta. Os presentes resultados revelam que o processo de fotodegradação dos filmes depende do comprimento de onda e do regime de excitação utilizado.

La synthèse de nanoparticules de fer zéro-valent, par le couplage des procédés d'ultrasonication et d'électrodéposition, est étudiée selon deux approches. La première partie de l'étude s'intéresse à l'influence du substrat, utilisé pour l'électrodéposition, sur la croissance des dépôts de fer et sur leur dispersion par ultrasonication. L'énergie interfaciale ainsi que l'énergie d'adhésion du dépôt sur le substrat (Y_(Fe/substrat) et W_(Fe/substrat) respectivement) étant reliées à l'énergie de surface et à la rugosité du substrat, un intérêt particulier a été porté à ces deux propriétés. Ainsi, deux matériaux présentant des énergies de surface différentes, l'or (Au) et le carbone vitreux (VC), ainsi que des rugosités différentes ont été testés. Un développement théorique basé sur les interactions de Van der Waals a permis de démontrer que Y_(Fe/VC)>Y_(Fe/Au) ce qui suggère une meilleure affinité du dépôt de fer avec l'or qu'avec le VC. Cette différence influence la morphologie (croissance 2D sur or et 3D sur le VC) mais aussi l'adhésion des dépôts. En effet, les expériences réalisées pour étudier l'effet des ultrasons sur le dépôt de fer révèlent une dispersion du dépôt progressive et complète pour le cas du VC alors qu'aucun détachement du dépôt n'est obtenu en utilisant l'or. La seconde partie de l'étude est consacrée à la synthèse de nanoparticules de fer par une nouvelle approche : l'électrodéposition de dépôts de fer ramifiés est étudiée dans une cellule de Hele-Shaw intégrant un élément vibrant (diaphragme piézoélectrique) permettant à la fois la formation de dépôts de fer et leur fragmentation. Les expériences menées révèlent que les bulles d'hydrogène, formées lors de la co-réduction des protons libres durant l'électrodéposition du fer, influencent fortement le processus de fragmentation. En utilisant des hautes fréquences et amplitudes de vibration du PZT, les bulles d'hydrogène oscillent avec des déformations de surface. Celles-ci génèrent des vitesses d'interface suffisamment hautes (˜ 4 m/s) pour permettre aux bulles de fragmenter des dépôts ramifiés en particules de fer, de tailles comprises entre 1 µm et 100 nm, et présentant une grande surface spécifique due à leur morphologie dendritique. Cette deuxième partie de l'étude permet d'ouvrir la voie à une nouvelle technologie de fabrication des nanoparticules. / This study concerns the coupling of the ultrasounds with the electrodeposition process for the synthesis of zero-valent iron nanoparticles; it is structured in two sections. The first focuses on the electrode substrate used for the iron electrodeposition and aims to determine its influence on both the deposit growth and its dispersion by ultrasonication. The interfacial and the adhesion energies of the deposit on the substrate (Y_(Fe/substrate) and W_(Fe/substrate) respectively) being related to the surface energy and the roughness of the substrate, a particular focus is put on the influence of these two properties. Thus, two materials of different surface energies, gold (Au) and vitreous carbon (VC), as well as various roughnesses, are tested. Considering only the Van der Waals interactions, a theoretical development has enabled to determine that Y_(Fe/VC)>Y_(Fe/Au) which suggests a better affinity of the iron deposit with the gold than with the VC substrate. This difference impacts the deposit morphology (2D growth on the gold and 3D growth on the VC substrate) but also the deposit adhesion. Indeed, experiments performed to study the effect of ultrasounds on the iron electrodeposit reveal its progressive and complete dispersion for the vitreous carbon case while no dispersion (no removal of the deposit from the electrode) is obtained with the gold substrate. The second section of the present study deals with the synthesis of iron nanoparticles; to this end, the electrodeposition of branched deposits has been investigated in a Hele-Shaw cell integrating a vibrating element (piezoelectric diaphragm), expected to allow both the deposit formation and its fragmentation. Experiments reveal that the hydrogen bubbles, formed by the co-reduction of free protons during the iron electrodeposition, strongly influence the fragmentation process. Using high vibration frequencies and high amplitudes, the bubbles oscillate with surface deformations, inducing interface velocity sufficiently high (˜ 4 m/s) to allow the fragmentation of the deposit into particles of sizes ranging between 1 µm and 100 nm and showing a high specific surface due to their dendritic morphology. Thus this work opens the way for a new particles manufacturing technology.

Le mélange de polymères est une méthode répandue pour élaborer des matériaux polymères. Cependant, la plupart des polymères sont thermodynamiquement immiscibles entre eux, engendrant une séparation de phase des mélanges et une détérioration de leurs propriétés. Afin de palier ces problèmes, la méthode dite compatibilisation réactive est souvent employée. Elle est basée sur la formation in-situ de copolymères à bloc ou greffés par l’intermédiaire de réactions interfaciales entre polymères réactifs. Cette thèse a pour objet de développer un concept dit agent compatibilisant-traceur réactif qui permettra d’utiliser de faibles quantités d’agents compatibilisants réactifs pour évaluer leurs efficacités de compatibilisation directement sur des extrudeuses bi-vis industrielles, d’une part ; et de caractériser la performance du mélange d’une extrudeuse bi-vis en fonction des conditions opératoires et/ou du profil de vis employé. Ses principales contributions se résument ci-après. L’anthracène de 9-méthylaminométhyle (MAMA), une molécule fluorescente, est incorporée dans un copolymère statistique de styrène (St) et d’isocyanate de 3-isopropenyle-?, ?’-diméthylebenzène (TMI), noté PS-TMI, pour former un agent compatibilisant-traceur réactif, noté PS-TMI-MAMA. Ce dernier sert à la fois comme agent compatibilisant réactif grâce aux groupements isocyanate et traceur grâce aux groupements fluorescents. Il est utilisé pour les mélanges à base de polystyrène (PS) et de polyamide 6 (PA6) afin d’évaluer son efficacité de compatibilisation. Les mélanges PS/PA6 sont élaborés dans un mélangeur discontinu et une extrudeuse bi-vis, respectivement. Dans le cas du mélangeur discontinu, la quantité du copolymère greffé formé in-situ, noté PS-g-PA6-MAMA, augmente alors que le diamètre des domaines de la phase dispersée (DDD) diminue considérablement au début du mélange. Lorsque le mélange se poursuit, le nombre de greffons en PA6 du PS-g-PA6-MAMA augmente, engendrant une composition très asymétrique du PS-g-PA6-MAMA qui est thermodynamiquement instable aux interfaces. De ce fait, il peut être arraché des interfaces vers la phase PA6 et peut y former des micelles. Lorsqu’il est arraché des interfaces, il perdra son efficacité de compatibilisation et le DDD augmentera. L’action du mélange a un double effet sur le procédé de compatibilisation réactive. Il promeut la réaction interfaciale entre le PS-TMI-MAMA et le PA6, d’une part ; et aggrave l’arrachage du PS-g-PA6-MAMA de l’interface, d’autre part. L’utilisation de faibles quantités de l’agent compatibilisant-traceur réactif permet de mesurer les évolutions de la teneur en agent compatibilisant-traceur réactif, du DDD et de la teneur en agent compatibilisant-traceur réactif ayant réagi en fonction du temps de séjour dans une extrudeuse bi-vis. Pour une masse molaire donnée, l’efficacité de compatibilisation d’un agent compatibilisant-traceur réactif augmente avec l’augmentation de la teneur en TMI dans une certaine limite. Pour une teneur en TMI donnée, la réaction interfaciale est plus rapide avec la diminution de la masse molaire dans une certaine limite et le DDD devient plus petit en un temps plus court. L’influence du taux de remplissage de la vis est plus significative que celle du temps de séjour. Lorsque le taux de remplissage de la vis augmente, le taux de la réaction interfaciale augmente et le DDD diminue. Lorsque l’angle d’un élément de mélange augmente, les efficacités du mélange distributif et du mélange dispersif augmentent, ce qui se traduit par une augmentation de la quantité du PS-g-PA6-MAMA formée et une diminution du DDD par rapport à la même quantité de PS-g-PA6-MAMA produite. Lorsque la largeur d’un élément de mélange augmente, l’efficacité du mélange distributive augmente alors que celle du mélange dispersif demeure inchangée. La substitution d’éléments de mélange par des éléments inverses améliore l’efficacité du mélange distributif et celle du mélange dispersif / Polymer blending is a common method to prepare high-performance polymer materials. However, most polymer pairs are thermodynamically immiscible, leading to phase separation and deterioration in material properties. To overcome such problems, the most common method is reactive compatibilization which is based on the in-situ formation of a graft or block copolymer by interfacial reaction between reactive polymers. This thesis aims at developing a concept of reactive compatibilizer-tracer which will allow using small amounts of reactive compatibilizers to evaluate their compatibilizing efficiency in industrial scale twin screw extruders, on the one hand; and to characterize the mixing performance of a twin screw extruder as a function of process conditions and/or screw profile. Its main contributions are summarized below. 9-(methylaminomethyl) anthracene (MAMA), a fluorescent molecule, is incorporated into a random copolymer of styrene (St) and 3-isopropenyl-?, ?’-dimethylbenzene isocyanate (TMI), denoted as PS-TMI, to form a reactive compatibilizer-tracer, denoted as PS- TMI-MAMA. The latter serves both as a reactive compatibilizer due to its isocyanate moieties and a tracer due to its fluorescent moieites. It is used for polystyrene (PS)/polyamide 6 (PA6) blends to evaluate its compatibilizing efficiency. Compatibilized PS/PA6 blends are processed in a batch mixer and in a twin screw extruder, respectively. In the case of the batch mixer, the amount of the in-situ formed graft copolymer denoted as PS-g-PA6-MAMA increases and the dispersed phase domain diameter (DDD) decreases drastically in the initial period of mixing. As the mixing further proceeds, the number of PA6 grafts of the PS-g-PA6-MAMA increases, resulting in a highly asymmetrical composition of the PS-g-PA6-MAMA which causes thermodynamic instablility at the interface. As a result, it could be pulled out of the interface to the PA6 phase and form micelles. Once it is pulled out of the interface, it will lose its compatibilizing efficiency and the dispersed phase domain diameter increases sharply. Mixing has a dual effect on the reactive compatibilization process. On the one hand, it promotes the interfacial reaction between the PS-TMI-MAMA and PA6. On the other hand, it aggravates the pull out of the resulting PS-g-PA6-MAMA from the interface. The use of small amounts of the reactive compatibilizer-tracer together with transient experiments for RTD allows assessing the evolutions of the reactive compatibilizer-tracer content (CC), the dispersed phase domain diameter (DDD), and the reacted reactive compatibilizer-tracer content (RCC) as a function of residence time in a twin-screw extruder. Based on the above results, the emulsification curve (DDD vs. CC), the RCC vs. CC curve and effective emulsification curve (DDD vs. RCC) are obtained. When the molar mass of the reactive compatibilizer-tracer is fixed, its compatibilizing efficiency increases with increasing TMI content within an appropriate range. When its TMI content is fixed, the interfacial reaction goes faster as the molar mass of the reactive compatibilizer-tracer decreases within a certain range, and the DDD becomes smaller in a shorter time. The effect of degree of fill fixed by the throughput Q/screw speed N ratio is more dominant than that of residence time. As the degree of fill increases, the interfacial reaction increases and the DDD decreases. As the angle of adjacent the kneading block increases, its distributive and dispersive mixing efficiencies increase, resulting in an increase in interfacial area generation and a decrease in DDD on the basis of the same amount of PS-g-PA6-MAMA. On the other hand, as the width of the kneading block increases, the distributive mixing efficiency increases and the dispersive mixing efficiency remains unchanged. Substitution of kneading blocks by reverse ones increase both the distributive and dispersive mixing efficiencies