Fibronectin/phosphorylcholine coatings on fluorocarboned surfaces: a study upon adsorption and grafting processes

Depuis ces dernières décennies, le domaine des biomatériaux a connu un essor considérable, évoluant de simples prothèses aux dispositifs les plus complexes pouvant détenir une bioactivité spécifique. Outre, le progrès en science des matériaux et une meilleure compréhension des systèmes biologiques a offert la possibilité de créer des matériaux synthétiques pouvant moduler et stimuler une réponse biologique déterminée, tout en améliorant considérablement la performance clinique des biomatériaux. En ce qui concerne les dispositifs cardiovasculaires, divers recouvrements ont été développés et étudiés dans le but de modifier les propriétés de surface et d’améliorer l’efficacité clinique des tuteurs. En effet, lorsqu’un dispositif médical est implanté dans le corps humain, son succès clinique est fortement influencé par les premières interactions que sa surface établit avec les tissus et les fluides biologiques environnants. Le recouvrement à la surface de biomatériaux par diverses molécules ayant des propriétés complémentaires constitue une approche intéressante pour atteindre différentes cibles biologiques et orienter la réponse de l’hôte. De ce fait, l’élucidation de l’interaction entre les différentes molécules composant les recouvrements est pertinente pour prédire la conservation de leurs propriétés biologiques spécifiques. Dans ce travail, des recouvrements pour des applications cardiovasculaires ont été créés, composés de deux molécules ayant des propriétés biologiques complémentaires : la fibronectine (FN) afin de promouvoir l’endothélialisation et la phosphorylcholine (PRC) pour favoriser l’hémocompatibilité. Des techniques d’adsorption et de greffage ont été appliquées pour créer différents recouvrements de ces deux biomolécules sur un polymère fluorocarboné déposé par traitement plasma sur un substrat en acier inoxydable. Dans un premier temps, des films de polytétrafluoroéthylène (PTFE) ont été utilisés en tant que surface modèle afin d’explorer l’interaction de la PRC et de la FN avec les surfaces fluorocarbonées ainsi qu’avec des cellules endothéliales et du sang. La stabilité des recouvrements de FN sur l’acier inoxydable a été étudiée par déformation, mais également par des essais statiques et dynamiques sous-flux. Les recouvrements ont été caractérisés par Spectroscopie Photoéléctronique par Rayons X, immunomarquage, angle de contact, Microscopie Électronique de Balayage, Microscopie de Force Atomique et Spectrométrie de Masse à Ionisation Secondaire à Temps de Vol (imagerie et profilage en profondeur). Des tests d’hémocompatibilité ont été effectués et l’interaction des cellules endothéliales avec les recouvrements a également été évaluée. La FN greffée a présenté des recouvrements plus denses et homogènes alors que la PRC quant à elle, a montré une meilleure homogénéité lorsqu’elle était adsorbée. La caractérisation de la surface des échantillons contenant FN/PRC a été corrélée aux propriétés biologiques et les recouvrements pour lesquels la FN a été greffée suivie de l’adsorption de la PRC ont présenté les meilleurs résultats pour des applications cardiovasculaires : la promotion de l’endothélialisation et des propriétés d’hémocompatibilité. Concernant les tests de stabilité, les recouvrements de FN greffée ont présenté une plus grande stabilité et densité que dans le cas de l’adsorption. En effet, la pertinence de présenter des investigations des essais sous-flux versus des essais statiques ainsi que la comparaison des différentes stratégies pour créer des recouvrements a été mis en évidence. D’autres expériences sont nécessaires pour étudier la stabilité des recouvrements de PRC et de mieux prédire son interaction avec des tissus in vivo.

Optical emission spectroscopy as a process-monitoring tool in PECVD of amorphous carbon coatings

Dans ce projet de recherche, le dépôt des couches minces de carbone amorphe (généralement connu sous le nom de DLC pour Diamond-Like Carbon en anglais) par un procédé de dépôt chimique en phase vapeur assisté par plasma (ou PECVD pour Plasma Enhanced Chemical Vapor deposition en anglais) a été étudié en utilisant la Spectroscopie d’Émission Optique (OES) et l’analyse partielle par régression des moindres carrés (PLSR). L’objectif de ce mémoire est d’établir un modèle statistique pour prévoir les propriétés des revêtements DLC selon les paramètres du procédé de déposition ou selon les données acquises par OES. Deux séries d’analyse PLSR ont été réalisées. La première examine la corrélation entre les paramètres du procédé et les caractéristiques du plasma pour obtenir une meilleure compréhension du processus de dépôt. La deuxième série montre le potentiel de la technique d’OES comme outil de surveillance du procédé et de prédiction des propriétés de la couche déposée. Les résultats montrent que la prédiction des propriétés des revêtements DLC qui était possible jusqu’à maintenant en se basant sur les paramètres du procédé (la pression, la puissance, et le mode du plasma), serait envisageable désormais grâce aux informations obtenues par OES du plasma (particulièrement les indices qui sont reliées aux concentrations des espèces dans le plasma). En effet, les données obtenues par OES peuvent être utilisées pour surveiller directement le processus de dépôt plutôt que faire une étude complète de l’effet des paramètres du processus, ceux-ci étant strictement reliés au réacteur plasma et étant variables d’un laboratoire à l’autre. La perspective de l’application d’un modèle PLSR intégrant les données de l’OES est aussi démontrée dans cette recherche afin d’élaborer et surveiller un dépôt avec une structure graduelle.

Corrosion protection of PVD and paint coatings for selective solar absorber surfaces

The selective solar absorber surface is a fundamental part of a solar thermal collector, as it is responsible for the solar radiation absorption and for reduction of radiation heat losses. The surface’s optical properties, the solar absorption (á) and the emittance (å), have great impact on the solar thermal collector efficiency. In this work, two coatings types were studied: coatings obtained by physical vapor deposition (PVDs) and coatings obtained by projection with different paints (PCs) on aluminum substrates. The most common industrial high performing solar selective absorbers are nowadays produced by vacuum deposition methods, showing some disadvantages, such as lower durability, lower resistance to corrosion, adhesion and scratch, higher cost and complex production techniques. Currently, spectrally selective paints are a potential alternative for absorbing surfaces in low temperature applications, with attractive features such as ease of processing, durability and commercial availability with low cost. Solar absorber surfaces were submitted to accelerated ageing tests, specified in ISO 22975-3. This standard is applicable to the evaluation of the long term behavior and service life of selective solar absorbers for solar collectors working under typical domestic hot water system conditions. The studied coatings have, in the case of PVDs solar absorptions between 0.93 and 0.96 and emittance between 0.07 and 0.10, and in the case of PCs, solar absorptions between 0.91 and 0.93 and emittance between 0.40 and 0.60. In addition to evaluating long term behavior based on artificial ageing tests, it is also important to know the degradation mechanism of different coatings that are currently in the market. Electrochemical impedance spectroscopy (EIS) allows for the assessment of mechanistic information concerning the degradation processes, providing quantitative data as output, which can easily relate to the kinetic parameters of the system. EIS measures were carried out on Gamry FAS2 Femostat coupled with a PCL4 Controller. Two electrolytes were used, 0.5 M NaCl and 0.5 M Na2SO4, and the surfaces were tested at different immersion times up to 4 weeks. The following types of specimens have been tested: Aluminium with/without surface treatment, 3 selective paint coatings (one with a poly(urethane) binder and two with silicone binders) and 2 PVD coatings. Based on the behaviour of the specimens throughout the 4 weeks of immersion, it is possible to conclude that the coating showing the best protective properties corresponds to the selective paint coating with a polyurethane resin followed by the other paint coatings, whereas both the PVD coatings do not confer any protection to the substrate, having a deleterious effect as compared to the untreated aluminium reference.

MICROSCALE DIELECTRIC ANTI-REFLECTION COATINGS FOR PHOTOVOLTAICS

In order to power our planet for the next century, clean energy technologies need to be developed and deployed. Photovoltaic solar cells, which convert sunlight into electricity, are a clear option; however, they currently supply 0.1% of the US electricity due to the relatively high cost per Watt of generation. Thus, our goal is to create more power from a photovoltaic device, while simultaneously reducing its price. To accomplish this goal, we are creating new high efficiency anti-reflection coatings that allow more of the incident sunlight to be converted to electricity, using simple and inexpensive coating techniques that enable reduced manufacturing costs. Traditional anti-reflection coatings (consisting of thin layers of non-absorbing materials) rely on the destructive interference of the reflected light, causing more light to enter the device and subsequently get absorbed. While these coatings are used on nearly all commercial cells, they are wavelength dependent and are deposited using expensive processes that require elevated temperatures, which increase production cost and can be detrimental to some temperature sensitive solar cell materials. We are developing two new classes of anti-reflection coatings (ARCs) based on textured dielectric materials: (i) a transparent, flexible paper technology that relies on optical scattering and reduced refractive index contrast between the air and semiconductor and (ii) silicon dioxide (SiO2) nanosphere arrays that rely on collective optical resonances. Both techniques improve solar cell absorption and ultimately yield high efficiency, low cost devices. For the transparent paper-based ARCs, we have recently shown that they improve solar cell efficiencies for all angles of incident illumination reducing the need for costly tracking of the sun’s position. For a GaAs solar cell, we achieved a 24% improvement in the power conversion efficiency using this simple coating. Because the transparent paper is made from an earth abundant material (wood pulp) using an easy, inexpensive and scalable process, this type of ARC is an excellent candidate for future solar technologies. The coatings based on arrays of dielectric nanospheres also show excellent potential for inexpensive, high efficiency solar cells. The fabrication process is based on a Meyer rod rolling technique, which can be performed at room-temperature and applied to mass production, yielding a scalable and inexpensive manufacturing process. The deposited monolayer of SiO2 nanospheres, having a diameter of 500 nm on a bare Si wafer, leads to a significant increase in light absorption and a higher expected current density based on initial simulations, on the order of 15-20%. With application on a Si solar cell containing a traditional anti-reflection coating (Si3N4 thin-film), an additional increase in the spectral current density is observed, 5% beyond what a typical commercial device would achieve. Due to the coupling between the spheres originated from Whispering Gallery Modes (WGMs) inside each nanosphere, the incident light is strongly coupled into the high-index absorbing material, leading to increased light absorption. Furthermore, the SiO2 nanospheres scatter and diffract light in such a way that both the optical and electrical properties of the device have little dependence on incident angle, eliminating the need for solar tracking. Because the layer can be made with an easy, inexpensive, and scalable process, this anti-reflection coating is also an excellent candidate for replacing conventional technologies relying on complicated and expensive processes.

Interference lithography for optical devices and coatings

Interference lithography can create large-area, defect-free nanostructures with unique optical properties. In this thesis, interference lithography will be utilized to create photonic crystals for functional devices or coatings. For instance, typical lithographic processing techniques were used to create 1, 2 and 3 dimensional photonic crystals in SU8 photoresist. These structures were in-filled with birefringent liquid crystal to make active devices, and the orientation of the liquid crystal directors within the SU8 matrix was studied. Most of this thesis will be focused on utilizing polymerization induced phase separation as a single-step method for fabrication by interference lithography. For example, layered polymer/nanoparticle composites have been created through the one-step two-beam interference lithographic exposure of a dispersion of 25 and 50 nm silica particles within a photopolymerizable mixture at a wavelength of 532 nm. In the areas of constructive interference, the monomer begins to polymerize via a free-radical process and concurrently the nanoparticles move into the regions of destructive interference. The holographic exposure of the particles within the monomer resin offers a single-step method to anisotropically structure the nanoconstituents within a composite. A one-step holographic exposure was also used to fabricate self- healing coatings that use water from the environment to catalyze polymerization. Polymerization induced phase separation was used to sequester an isocyanate monomer within an acrylate matrix. Due to the periodic modulation of the index of refraction between the monomer and polymer, the coating can reflect a desired wavelength, allowing for tunable coloration. When the coating is scratched, polymerization of the liquid isocyanate is catalyzed by moisture in air; if the indices of the two polymers are matched, the coatings turn transparent after healing. Interference lithography offers a method of creating multifunctional self-healing coatings that readout when damage has occurred.

Fire protection durability of intumescent coatings after accelerated aging

The most common method of achieve the required fire resistance is by the use of passive fire protection systems, being intumescent coatings the fire protection material frequently used. These are usually considered thin film coatings as they are applied with a dry film thickness (DFT) between 0.3-3 [mm]. The required DFT is obtained by experimental fire resistance tests performed to assess the contribution of this reactive fire protection material to the steel member fire resistance. This tests are done after dry coating and a short time period of atmospheric conditioning, at constant temperature and humidity. As the coatings formulation is mainly made from polymeric basis compounds, it is expected that the environmental factors, such temperature, humidity and UV radiation (UVA and UVB) significantly affect the intumescent coating fire protection performance and its durability. This work presents a research study about the effects of aging on the fire protection performance of intumescent coatings. A commercial water based coating is submitted to an accelerated aging cycle, using a QUV Accelerated Weathering Tester. This tests aim to simulate 10 years of the coating natural aging. The coating durability is tested comparing the fire protection of small steel samples submitted to a radiant heat flux exposure from a cone calorimeter. In total, 28 tests were performed on intumescent coating protected steel specimens, of which 14 specimens were tested before the hydrothermal aging test and other 14 after accelerated aging. The experimental tests results of the steel temperature evolution shows that increasing the intumescent dry coating film thickness, the fire resistance time increases. After the accelerated aging cycles, the coating lose their ability to expand, resulting in an increase of the steel temperature of approximately 200 [ºC], compared to the samples without aging.

Decorative tiles between Brazil and Europe: the case of the Santa Catharina factory

Abstract It was in the first decade of the twentieth century that the first white china Factory was implemented in Brazil. Fruit of the association between the Sao Paulo Aristocracy and the Italian Romeo Ranzini, this factory was responsible for producing significant amounts of crockery in industrial moulds in sao Paulo, Brazil. It was also the first factory to produce decorative tiles that would be part of the architecture of the public buildings built between 1919 and 1922 in Commemoration of the Centennial of the Brazilian Independence. Known as The Santa Catharina Factory, this factory was inaugurated in 1913 with the participation of Italian immigrants and German technologies for the development of its first manufacturing activities. As a result of a number of economic, political and social matters that started in the previous century in the city of Sao Paulo, The Santa Catharina factory played an important role in industrial development as regards the production of national white china and was used as a model for the construction of new ceramic factories in Sao Paulo. After acquired by Matarazzo industries in 1927, had closed their activities in 1937. This research is based on the identification and analysis of the first tiles produced in Brazil by the Santa Catharina Factory, which were part of the architectural decorations of the buildings built in Sao Paulo to the celebration of the Centennial of the Brazilian Independence. Designed by Victor Dubugras, The Largo da Memoria (located in the city of Sao Paulo) and the buildings located in the "Paths of the Sea" road marked the beginning of Brazilian industrialization and the emergence of Neocolonial Movement in architecture of Sao Paulo. Studies of the first national patterns of decorative tiles approach a subject poorly researched by experts in tiled studies in Brazil, although in this case these tiles have represented not only an important milestone in the national industrialization, but also have demarcated the significant changes in architectural and decorative practices in the country in the early twentieth century; RESUMÈ: C'est durant la premiere decennie du XXe siecle que la premiere usine de porcelaine blanche fut implant& au Bresil. Elle fut le fruit de l'association entre l'aristocratie de Sao Paulo et l'italien Romeo Ranzini. L'usine produisait une quantite signifiante de porcelaine sur le territoire industriel de Sao Paulo. Ce fut egalement la premiere usine a produire des carreaux decoratifs qui sont aujourd'hui visibles dans l'architecture des batiments publics construit entre 1919 et 1922, pour la commemoration du centenaire de l'independance bresilienne. Connue sous le nom de Santa Catharina, cette usine fut inaugure en 1912. Elle fut construite par des émigrés Italiens, et utilisa pour la technologie allemande pour so production. En tant que resultat d'un certain nombre de questions economiques, politiques et sociales qui ont &butes durant le siecle precedent dans la ville de Sao Paulo, l'usine Santa Catharina a joue un role important dans le developpement industriel de la production de porcelaine blanche nationale et a ete utilise comme modele pour la construction de nouvelles usines de ceramique a Sao Paulo. Apres avoir ete achete par l'industrie Matarazzo en 1927, elle cessa ses activites en 1937. Cette recherche est basee sur l'identification et l'analyse des premiers carreaux decoratifs fabriques au Bresil par l'usine Santa Catharina, qui etait une partie des decorations architecturales des batiments construits a Sao Paulo pour la celebration du centenaire de l'Independance Bresilienne. Connue par Victor Dubugras, le "Largo da Memoria" (situe dans la ville de Sao Paulo), et les batiments situes sur le "Path of the Sea", ont marque le debut de l'industrialisation bresilienne et l'emergence d'un mouvement neocolonialiste dans l'architecture de Sao Paolo. L'etude des premiers modeles nationaux de carreaux decoratifs est un sujet peut etudie par les experts bresiliens, bien qu'ils furent un jalon importante pour l'industrialisation nationale. Its ont egalement entrains des changements importants dans les pratiques architecturales, et decoratives au sein du pays au XXe siecle. Mots-cles: Ceramique - carreaux decoratifs — L'usine Santa Catharina, Bresil - Production de carreaux; RIASSUNTO: Nel primo decennio del Novecento vide luce la prima fabbrica di ceramica di porcellana in Brasile. Frutto dell'associazione tra l'aristocrazia Paulista e l'italiano Romeo Ranzini, questa fabbrica fu responsabile della produzione di notevoli quantita di ceramica di porcellana mediante stampi industriali nella citta di San Paolo, Brasile. Fu anche la prima fabbrica a produrre azulejos che avrebbero poi fatto parte dell'architettura degli edifici pubblici costruiti tra it 1919 ed it 1922, per la commemorazione del Centenario dell'indipendenza Brasiliana. Conosciuta come Fabbrica di Santa Catharina, questa fu inaugurata nel 1913, con la partecipazione di immigrati italiani e con l'impiego di tecnologie tedesche per lo sviluppo delle sue prime attivita produttive. Risultato di una serie di cambiamenti economici, politici e sociali, che ebbero inizio nel secolo precedente nella citta di San Paolo, la Fabbrica di Santa Catharina svolse un ruolo importante nello sviluppo industriale per quanto riguarda la produzione di ceramica di porcellana nazionale e fu adottata come modello per la costruzione di nuove fabbriche a San Paolo. Successivamente, fu acquisita dalle industrie Matarazzo nel 1927, vedendo poi chiudersi le sue attivita nel 1937. Questa ricerca si basa sull'identificazione e l'analisi dei primi azulejos prodotti in Brasile dalla Fabbrica di Santa Catharina che fecero parte delle decorazioni architettoniche degli edifici costruiti a San Paolo per la commemorazione del Centenario dell'indipendenza Brasiliana. Progettati da Victor Dubugras, it Largo da Mem(Via (situato nella citta di San Paolo) e gli edifici che si trovano nei Caminhos do Mar marcarono l'inizio dell'industrializzazione brasiliana e la nascita del Movimento Neocolonial dell'architettura Paulista. Gli studi dei primi modelli di azulejos nazionali affrontano un argomento poco studiato dagli esperti in azulejaria in Brasile, nonostante rappresentino un importante avvenimento dell'industrializzazione nazionale, ma segnano anche i cambiamenti di significative pratiche architettoniche e decorative nel Paese nel primo Novecento. Parole chiave: Ceramica - porcellana - La fabbrica di Santa Catharina - Produzione di ceramica .