This research focuses on carbon fiber treatment by nitric acid and 3- (trimethoxysilyl)propyl methacrylate silane, and how this affects carbon/vinyl ester composites. These composites offer great benefits, but it is difficult to bond the fiber and matrix together, and without a strong interfacial bond, composites fall short of their potential. Silanes work well with glass fiber, but do not bond directly to carbon fiber because its surface is not reactive to liquid silanes. Oxidizing surface treatments are often prescribed for improved wetting and bonding to carbon, but good results are not always achieved. Furthermore, there is the unanswered question of environmental durability. This research aimed to form a better understanding of oxidizing carbon fiber treatments, determine if silanes can be bonded to oxidized surfaces, and how these treatments affect composite strength and durability before and after seawater exposure. Nitric acid treatments on carbon fibers were found to improve their tensile strength to a constant level by smoothing surface defects and chemically modifying their surfaces by increasing carbonyl and carboxylic acid concentrations. Increasing these surface group concentrations raises fiber polar energy and causes them to cohere. This impedes wetting, resulting in poor quality, high void content composites, even though there appeared to be improved adhesion between the fibers and matrix. Silane was found to bond to the oxidized carbon fiber surfaces, as evidenced by changes in both fiber and composite properties. The fibers exhibited low polarity and cohesion, while the composites displayed excellent resin wetting, low void content, and low seawater weight gain and swelling. On the contrary, the oxidized fibers that were not treated with silane exhibited high polarity and fiber cohesion. / Their composites displayed poor wetting, high void content, high seawater weight gain, and low swelling. Both fiber treatment types resulted in great improvements in dry transverse tensile strength over the untreated fibers, but the oxidized fiber composites lost strength as the acid treatment time was extended, due to poor wetting. The acid/silane treated composites lost some transverse tensile strength after seawater exposure, but the nitric acid oxidized fiber composites appeared to be more seawater durable. / by Tye A. Langston. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

Neste trabalho buscou-se otimizar a obtenção de três diferentes filmes polissilânicos, a base de bis-1,2-(trietoxisilil)etano (BTSE), bis-(-trimetoxisililpropil)amina (BTSPA) e bis-1,2-[(trietoxisilil)propil]tetrassulfeto (BTESPT), com o intuito de proporcionar maior resistência à corrosão para o aço carbono e para o aço galvanizado. Foi variada a concentração do silano, o tempo de hidrólise e dopantes (íons de cério (III) e cério (IV)), sendo estes últimos adicionados na solução precursora. Estes parâmetros foram testados sobre dois tipos de superfícies: uma a base de ferro (aço carbono) e outra a base de zinco (aço galvanizado) obtendo, desta forma, condições para que cada filme polissilânico fornecesse a melhor proteção contra corrosão do substrato. As técnicas eletroquímicas usadas para esta avaliação foram espectroscopia de impedância eletroquímica (EIE), resistência de polarização linear (Rp) e curvas de polarização (CP); também foram utilizadas a microscopia de força atômica (AFM) e a microscopia eletrônica de varredura (MEV). Com a otimização do processo de obtenção dos filmes de silano, foram pré-tratados os corpos-de-prova (cdp) e submetidos ao processo de pintura, objetivando a comparação entre o pré-tratamento a base de silano e o de fosfatização, ambos atuando como promotores de resistência à corrosão e aderência entre os substratos e a camada de tinta. Os cdps pintados foram avaliados por EIE, testes físicos de aderência e flexibilidade e também por ensaios acelerados de corrosão atmosférica (névoa salina). Os resultados mostraram que todas as camadas a base de polissilanos estudadas proporcionaram ao aço carbono e ao aço galvanizado aumento em suas respectivas resistências à corrosão em solução de NaCl 0,1 mol.L-1 e que, pela adição de íons de Ce3+ ou Ce4+, é observada uma maior eficiência no efeito barreira do filme devido à formação de óxidos e/ou hidróxidos de cério e pela melhor reticulação do filme de silano, respectivamente. Os resultados mostraram que a utilização de pré-tratamentos a base de polissilanos em aço carbono e em aço galvanizado em processos de pintura industrial é possível, sendo esta uma potencial alternativa no aumento da resistência à corrosão para o aço e na minimização de impactos ambientais gerados nos processos de tratamentos de superfícies e de pintura. / The aim of the present study was to optimize the process to obtain three different silane films, based on the bis-1,2-(trietoxysilyl)ethane (BTSE), bis-(-trimetoxysilylpropyl)amine (BTSPA) and bis-1,2-[(trietoxysilyl)propyl]tetrasulphide (BTESPT), seeking superior corrosion resistance for carbon and galvanized steel. Silane concentration, time of hydrolysis and dopant (Ce3+ and Ce4+ ions) addition the latter being added in the precursor solution -were varied. These parameters were tested in two different surfaces: iron based (steel) and zinc base (galvanized steel), to obtain conditions for each silane film providing superior corrosion protection for the substrate. The electrochemical techniques used were electrochemical impedance spectroscopy (EIS), linear polarization resistance (Rp) and polarization curves; also was used the atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. In order to compare silane and phosphate based, pre-treated panels were painted with both acting as adhesion and corrosion resistance promoters between the substrate and the paint. Painted panels were evaluated by electrochemical impedance spectroscopy, adhesion and flexibility tests and also accelerated atmospheric corrosive tests (salt spray). The results showed that all the silane based films studied provided an increase of corrosion resistance in 0.1 mol.L-1 NaCl solution to the carbon and galvanized steel; with the addition of Ce3+ or Ce4+ ions better efficiency was observed for the barrier effect of the film due to the formation of cerium oxides and/or hydroxides and the better crosslinking of silane film, respectively. In addition, the experiences results that the use of silane based pre-treatments on carbon and galvanized steel in industrial painting processes is feasible and could be one of the potential alternative processes to increase the corrosion resistance for steel, reducing the environmental impacts generated in surface pretreatment and painting processes.

Os revestimentos poliméricos podem atuar como uma barreira física entre os íons agressivos e o substrato metálico. Porém, uma exposição prolongada pode causar danos ao revestimento polimérico, conduzir a uma redução contínua do efeito barreira e por consequência a perda da proteção contra a corrosão. A utilização de nano materiais pode atuar aumentando o efeito barreira, proporcionando um aumento no caminho de difusão dos íons agressivos e água até o substrato metálico. Nanopartículas de celulose apresentam elevada cristalinidade e razão de aspecto, excelentes propriedades mecânicas e são proveniente de fonte renovável. Por outro lado, a polianilina (PAni) vem sendo utilizada em revestimentos devido a elevação do potencial de corrosão dos aços devido o seu comportamento redox que proporciona a formação de uma camada de óxidos estável no substrato metálico. A aderência do revestimento polimérico é fundamental para que este possa atuar como revestimento protetor contra a corrosão. Com isso, um pré-tratamento superficial a base de ácido hexafluorzircônico e a utilização de organosilanos na resina epóxi, podem ser utilizados melhorando as propriedades de proteção contra a corrosão e de aderência. O objetivo deste estudo consistiu na obtenção de nanowhiskers de celulose (CNW) por moagem ultrafina através da celulose microcristalina (MCC) para posterior utilização em revestimento polimérico a base de resina epóxi. A CNW foi utilizada funcionalizada ou não com PAni SE (polianilina na forma condutora – sal de esmeraldina) em comparação a MCC nas mesmas condições. Foi avaliada a incorporação de silano aminopropiltrietoxisilano (APS) na resina epóxi e a utilização de uma camada de conversão de zircônia (Zr) aplicada ao substrato metálico. Os revestimentos poliméricos foram avaliados quanto a propriedades mecânicas e à proteção contra a corrosão. As imagens da microscopia de transmissão (TEM) mostram que é possível a obtenção da CNW por meio do processo de moagem, apresentando melhor estabilidade térmica em comparação a MCC. Os revestimentos poliméricos utilizando o silano APS e a camada de conversão de Zr apresentaram as melhores propriedades físicas e mecânicas. A interação entre a carga de reforço, a resina epóxi e a superfície metálica é um fator determinante na eficiência do revestimento polimérico, pois de acordo com a análise de migração subcutânea, a superfície do aço carbono, após 1000 h de exposição, não apresentou corrosão superficial. Com relação à proteção contra a corrosão, quando incorporado a CNW funcionalizada com PAni SE ao revestimento epóxi com APS e a camada de Zr, este apresentou os melhores resultados como constatado nas análises de névoa salina e espectroscopia de impedância eletroquímica (EIS). / Polymeric coatings can act as a physical barrier between the aggressive ions and the metal substrate. However, prolonged exposure can cause damage to the polymer coating and conduct to a continuous reduction in the barrier effect and result in the loss of protection against corrosion. The use of nanomaterials may act by increasing the barrier effect and providing an increased diffusion path of aggressive ions and water to the metal substrate. Cellulose nanoparticles have high crystallinity and aspect ratio, excellent mechanical properties and are derived from renewable sources. On the other hand polyaniline (PAni) has been used in coatings due to the increase of the corrosion potential of the steel due to redox behavior that results in the formation of a stable oxide layer on the metallic substrate. The adhesion of the polymeric coating is essential so that it can act as a protective coating against corrosion. With this, a superficial pre-treatment based on hexafluorzircônico acid and the use of organosilanes in the epoxy resin, can be used to improve the protection against corrosion properties and adhesion. The objective of this study was to obtain cellulose nanowhiskers (CNW) for ultrafine grinding through microcrystalline cellulose (MCC) for subsequent use in the polymer coating based on epoxy resin. The CNW was used functionalized or not with PAni SE (polyaniline in the conductive form - emeraldine salt) compared with MCC under the same conditions. The incorporation of silane aminopropyltriethoxysilane (APS) was evaluated in the epoxy resin and the use of a zirconia conversion layer (Zr) applied to the metal substrate. The polymeric coatings were evaluated for mechanical properties and corrosion protection. Transmission microscopy (TEM) show that obtaining the CNW through the ultrafine grinding process is possible, resulting in better thermal stability compared with MCC. Polymeric coatings using APS silane and Zr conversion coating had the best physical and mechanical properties. The interaction between the reinforcing filler, the epoxy resin and the metal surface is a determining factor in the efficiency of the polymeric coating, because according to the subcutaneous migration analysis, carbon steel surface after 1000 h of exposure, showed no corrosion superficial. With regard to protection against corrosion, when incorporated CNW functionalized with PAni SE to epoxy coating with APS and the Zr layer, showed the best results as found in salt spray tests and electrochemical impedance spectroscopy (EIS).

Com o desenvolvimento da nanociência e da nanotecnologia, as nanopartículas magnéticas vêm sendo cada vez mais gerado interesse devido as inúmeras possíveis aplicações na área de catálise, diagnóstico, pigmentos, sensores, etc. Atualmente, as nanopartículas com potencialidade de aplicação em biomedicina que pode se destacar os as ferritas magnéticas os quais apresentam comportamento superparamagnético a temperatura ambiente. Além dos ligantes funcionais, as nanopartículas magnéticas são geralmente recobertas com polímeros orgânicos ou inorgânicos, destacando-se a sílica, nessa última classe. O sistemas as nanopartículas magnéticas recobertas com sílica formando um sistema casca-caroço, possibilita que o núcleo magnético se mantenha protegido por uma camada polimérica que pode conter grupos funcionais ativos, formando hidridos orgânicos-inorgânicos que devido a sua propriedade hidrofóbica ou hidrofílica dependendo da natureza do ligante de modificação de superfície. Este trabalho foi desenvolvido com intuito de obter nanopartículas magnéticas de ferrita MFe2O4, com (M= Fe, Co, Ni e Cu) com controle de tamanho, forma, composição química e estrutural, dos quais foram sintetizados pelo método de decomposição térmica utilizando diferente precursores metálicos para adequação das melhores condições de síntese. As ferritas magnéticas foram recobrimento com sílica, modificando da superfície da partícula e possibilitando caráter hidrofílico ao sistema casca-caroço, apresentando uma melhor estabilidade coloidal em dispersão aquosa devido a presença de grupos silanois na superfície, bem como uma recobrimento uniforma com apenas um núcleo magnético sem formação de aglomerados. A funcionalização com o grupo o trietoxivinilsilano, através de reações de condensação via catálise básica ou ácida, formou uma rede polimérica Si-O-Si, sendo que a presença do grupo vinil (-CH=CH2) livre na a superfície do sistema casca-caroço foi evidenciado através da técnica de FTIR. Portanto foi possível a obtenção de um sistema hibrido orgânico-inorgânico com a superfície contendo grupo que podem ser reativos, abrindo a possibilidade da utilização deste material para futuros testes de aplicações como sensor multifuncional. / In recent decades the development of nanoscience and nanotechnology, magnetic nanoparticles have been increasingly generated interest due to the numerous possible applications in the field of catalysis, diagnosis, pigments, sensors, etc. Currently, the nanoparticles with potential of application in biomedicine that can stand out the magnetic ferrites which have superparamagnetic behavior at room temperature. In addition to the functional binders, magnetic nanoparticles are generally coated with organic or inorganic polymers, especially silica in the latter class. The magnetic nanoparticle systems covered with silica forming a shell-core system allow the magnetic core to remain protected by a polymeric layer that may contain active functional groups, forming organic-inorganic hydrides that due to its hydrophobic or hydrophilic property depending on the nature of the surface modifying binder. This work was developed to obtain magnetic nanoparticles of MFe2O4 ferrite, with (M = Fe, Co, Ni and Cu) control of size, shape, chemical and structural composition, of which were synthesized by the thermal decomposition method using different precursors to suit the best conditions of synthesis. The magnetic ferrites were coated with silica, modifying the surface of the particle and allowing a hydrophilic character to the shell-core system, presenting a better colloidal stability in aqueous dispersion due to the presence of silane groups on the surface, as well as a uniform coating with only one magnetic core without formation of agglomerates. The functionalization with the triethoxyvinylsilane group, through condensation reactions via basic or acid catalysis, formed a Si-O-Si polymer network, and the presence of the free vinyl group (-CH=CH2) on the shell surface was observed by FTIR technique. Therefore, it was possible to obtain an organic-inorganic hybrid system with the surface containing the reactive group, opening the possibility of using this material for tests of future applications as multifunctional sensor.

A reação química entre os hidróxidos alcalinos presentes no cimento e fases minerais reativas presentes no agregado dá origem a um gel sílico-alcalino que ao adsorver água se expande, podendo causar expansão e fissuração do concreto, afetando a sua durabilidade. Este fenômeno é chamado de reação álcali-agregado (RAA) e embora seja conhecido há aproximadamente 70 anos no meio técnico, e principalmente estar relacionado às grandes barragens e estruturas de concretos diversas de Usina hidrelétricas, nos últimos anos outros tipos de estruturas têm sido afetadas, inclusive fundações de edifícios, deixando ainda mais o problema em evidência. As medidas preventivas para esta reação já são conhecidas há muito tempo e aplicadas rotineiramente em estruturas de usinas hidrelétricas quando se tem agregados reativos, sendo recentemente normalizadas no Brasil. Porém, ainda existem grandes carências em se combater o fenômeno quando já se encontra instalado no concreto. Diante do exposto, este trabalho, desenvolvido dentro do programa de P&D de Furnas/ANEEL, teve como principal objetivo verificar a potencialidade de compostos a base de Silanos através de testes laboratoriais com vistas à aplicação em concretos contendo agregados reativos na tentativa de minimizar as expansões residuais em estruturas que já se encontram afetadas. As atividades desenvolvidas contemplam ensaios em barras de argamassas que foram tratadas, em três etapas distintas, com compostos a base de silanos. A primeira etapa foi desenvolvida como projeto piloto, e seus resultados serviram de apoio para a realização das etapas seguintes. Nas segunda e terceira etapas foi verificada a atuação dos produtos na prevenção e na mitigação da RAA, respectivamente. Os resultados obtidos na primeira etapa não foram satisfatórios, pois as expansões foram maiores do que as da referência. Já para a segunda e terceira etapas, os procedimentos para aplicação dos tratamentos previram que as barras fossem tratadas sem que estivessem previamente expostas à solução de NaOH, conforme realizado na primeira etapa, o que possivelmente ocasionou o acréscimo das expansões, sem a eficiência do produto. Os resultados obtidos nessas etapas se mostraram eficientes tanto na prevenção quanto na mitigação das expansões residuais da RAA e, embora o lítio produza uma maior eficiência na redução das expansões, os tratamentos à base de silano, e principalmente do tipo octiltrietoxisilano, mostraram muito promissores. Após o lítio, o tratamento à base do silano OCTEO, no teor de 10%, com o surfactante tipo DMSO, em aplicação múltipla, se mostrou mais eficiente. Para complemento da parte experimental da pesquisa, foram realizados ensaios de absorção de água por imersão e análises por microscopia eletrônica de varredura e verificou-se o efeito dos produtos de tratamento nos poros das argamassas. / The chemical reaction between cement alkaline hydroxides and reactive silica present in some aggregates produces an alkaline silicate gel that expands when it adsorbs water and can cause concrete expansion and cracking, thereby affecting durability. This phenomenon is known as alkali-aggregate reaction (AAR) and was first detected over 70 years ago as the cause of deterioration especially in large dams and a number of other concrete structures in hydroelectric power plants in general. In recent years, AAR has also been noted in other types of structure, such as building foundations, bringing the problem more dramatically to the fore. Preventive measures for AAR have long been known and are routinely applied in hydroelectric power plant structures when there are reactive aggregates. These measures have been recently standardized in Brazil. Nevertheless there are still flaws in our knowledge regarding how to mitigate expansion when this phenomenon is already present in the concrete. Considering these aspects, the main purpose of this study, developed within Furnas/ANEEL Research and Development Program, is to verify, at laboratory level, the mitigating potential of silane compounds in residual expansion in affected mortars which contain reactive aggregates. Assays were performed on bars of mortar treated with silane compounds in three different stages. The first stage was developed as a pilot study with results serving as support for the following stages. The second and third stages verified the activity of the products in the prevention and mitigation of AAR, respectively. The results obtained in the first stage were unsatisfactory as the expansions were greater than the references. The second and third stage treatments required bars not previously exposed to NaOH, differently from the first stage and which may have been the cause of the increased expansion and product inefficiency. The results in these stages proved satisfactory both in preventing and mitigating AAR residual expansions, and although lithium is more efficient in reducing expansions, silane based treatments, mainly the octyltriethoxysilane types proved most promising. Following lithium, the most efficient treatment was 10% content OCTEO silane with a DMSO type surfactant applied in multiple layers. To complement the experimental part of the study, assays on water absorption through immersion were performed as well as scanning electron microscopy to verify the effect of the treatment products on the mortar pores.

The term "Lab-on-a-Chip" (LoC) describes highly miniaturized systems in which the functionalities of entire laboratories are scaled down to the size of transportable microchips. Particularly in the field of chemical and bio-analysis, such platforms are desired for a fast and highly sensitive sample analysis at the point of care. This work focuses on silicon nanowire (SiNW) based sensors. Innovative device fabrication concepts are developed from various directions, for a facile and reliable assembly of LoC analysis systems. Firstly, a multifunctional microfluidic set-up is developed which allows for a facile reversible sealing of channel structures on virtually any kind of substrate while maintaining the possibility of a rapid prototyping of versatile channel designs and the applicability of high working pressures of up to 600 kPa. Secondly, a 3-(triethoxysilyl)propylsuccinic anhydride (TESPSA) based surface modification strategy for the attachment of specific receptor molecules without additional binding site passivation is explored. Thirdly, bottom-up grown SiNWs are utilized for producing parallel arrays of Schottky barrier field-effect transistors (FETs) via contact printing. Using the initially developed microfluidic set-up, the concept of the TESPSA-based receptor immobilization is proved via fluorescence microscopy and by applying the SiNW FETs as biosensors. Using a receptor-analyte system based on a set of antibodies and a peptide from human influenza hemagglutinin, it is shown that antibodies immobilized with the developed method maintain the specificity for their antigens. The fourth major research field in this work is the microfluidics-based alignment of one-dimensional nanostructures and their deposition at predetermined trapping sites for reliably fabricating single NW-based FETs. Such devices are expected to provide superior sensitivity over sensors based on parallel arrays of FETs. Consequently, within this work, innovative LoC devices fabrication approaches over a broad range of length scales, from micrometer scale down to the molecular level, are investigated. The presented methods are considered a highly versatile and beneficial tool set not only for SiNW-based biosensors, but also for any other LoC application. / Unter dem Begriff „Lab-on-a-Chip“ (LoC) fasst man stark miniaturisierte Systeme zusammen, die die Fähigkeiten eines ganzen Labors auf einen transportablem Mikrochip übertragen. Insbesondere im Bereich der Analyse chemischer und biologischer Proben werden solche Plattformen bevorzugt eingesetzt, da sie direkt am Ort der Probenentnahme schnelle, hoch sensible Messungen ermöglichen. Im Mittelpunkt dieser Doktorarbeit stehen Sensoren auf Basis von Siliziumnanodrähten (SiNWs). Auf verschiedenen Gebieten werden innovative Konzepte zur einfachen und zuverlässigen Herstellung von LoC Systemen entwickelt. Zu Beginn wird ein multifunktionaler Mikrofluidik-Aufbau vorgestellt, der ein einfaches reversibles Verschließen von Mikrofluidik-Kanälen auf nahezu allen möglichen Substraten erlaubt. Der Aufbau ermöglicht das schnelle Anfertigen und Testen verschiedener Kanalstrukturen sowie das Betreiben von Fluidik-Experimenten mit hohen Arbeitsdrücken von bis zu 600 kPa. Der zweite Schwerpunkt der Arbeit ist die Entwicklung einer Methode zur Funktionalisierung von Sensor-Oberflächen mittels 3-(Triethoxysilyl) Propyl Bernsteinsäure Anhydrid (TESPSA) für die Immobilisierung spezifischer Rezeptormoleküle. Bei dieser Methode entfällt die Notwendigkeit einer zusätzlichen Passivierung ungenutzter Anbindungsstellen. Des Weiteren erfolgt die Herstellung von Parallelschaltungen von Schottky-Barrieren-Feld-Effekt-Transistoren (SB-FETs) aus „bottom-up“ gewachsenen SiNWs durch mechanisches Abreiben der SiNWs vom Wachstumssubstrat auf ein Empfängersubstrat. Unter Verwendung des eingangs entwickelten Mikrofluidik-Aufbaus wird die prinzipielle Anwendbarkeit der TESPSA-basierten Rezeptor-Immobilisierung nachgewiesen, sowohl anhand von Fluoreszenzmikroskopie-Untersuchungen als auch mit Hilfe der SiNW FETs als Biosensoren. Mittels eines Rezeptor-Analyt-Systems, bestehend aus verschiedenen Antikörpern und einem Peptid des Influenzavirus A, wird gezeigt, dass Antikörper, die über TESPSA an Oberflächen gebunden werden, ihre Spezifizität für ihre Antigene beibehalten. Der vierte große Forschungsabschnitt dieser Arbeit widmet sich der mikrofluidischen Ausrichtung eindimensionaler Nanomaterialien und deren Ablage an vorgegebenen Fangstellen, wodurch eine zuverlässige Herstellung von FETs aus Einzelnanodrähten erreicht wird. Es wird davon ausgegangen, dass Einzelnanodraht-FETs gegenüber Parallelschaltungen von Nanodraht-FETs verbesserte Sensoreigenschaften aufweisen. Folglich beinhaltet diese Arbeit viele zukunftsweisende Ansätze für die Herstellung von LoC Systemen. Untersuchungen über eine Bandbreite von Längenskalen, von Mikrometer großen Strukturen bis hinab zur molekularen Ebene, werden präsentiert. Es wird davon ausgegangen, dass die vorgestellten Methoden als eine vielfältige Sammlung von Werkzeugen nicht nur bei der Herstellung von Biosensoren auf SiNW-Basis Einsatz finden, sondern ganz allgemein den Aufbau verschiedenster LoC Systeme vorantreiben.

*Please refer to dissertation for diagrams. / Part I describes the silicon-hydrogen bond activation (SiHA) of silanes with both electron-deficient iridium porphyrin carbonyl chloride (Ir(ttp)Cl(CO)) and electron-rich iridium porphyrin methyl (Ir(ttp)Me) to give iridium(III) porphyrin silyls (Ir(ttp)SiR3). Firstly, Ir(ttp)SiR3 were synthesized in moderate to good yields conveniently from the reactions of Ir(ttp)Cl(CO) and Ir(ttp)Me with silanes, via SiHA in solvent-free conditions and non-polar solvents at 200°C. Base facilitated the SiHA reaction even at lower temperature of 140°C. Specifically, K3PO4 accelerated the SiHA with Ir(ttp)Cl(CO), while KOAc promoted the SiHA by Ir(ttp)Me. Mechanistic experiments suggest that Ir(ttp)Cl(CO) initially forms iridium porphyin cation (Ir(ttp)+), which then reacts with silanes likely via heterolysis to give iridium porphyrin hydride (Ir(ttp)H). Ir(ttp)H further reacts with silanes to yield Ir(ttp)SiR3. On the other hand, Ir(ttp)Me and Ir(ttp)SiR3 undergo either oxidative addition (OA) or sigma-bond metathesis (SBM) to form the products. In the presence of base, a penta-coordinated silicon hydride species likely forms and reacts with Ir(ttp)Me to form iridium porphyrin anion (Ir(ttp) -) that can further react with silane to yield Ir(ttp)H after protonation. Ir(ttp)H finally reacts with excess silane to give Ir(ttp)SiR 3.* / Part II describes successful base promoted aromatic carbon-fluorine (C-F) and carbon-hydrogen (C-H) bond activation of fluorobenzenes in neat conditions to give the corresponding iridium(III) porphyrin aryls (Ir(ttp)Ar) at 200°C in up to 95% yield. Mechanistic studies suggested that Ir(ttp)SiEt3 is firstly converted to Ir(ttp)- in the presence of KOH. Ir(ttp)- cleaves the aromatic C-F bond via an S NAr process. As the reaction proceeds, a hydroxide anion can coordinate to the iridium center of Ir(ttp)Ar to form an iridium porphyrin trans aryl hydroxyl anion (trans-[ArIr(ttp)OH]-). In the presence of water, trans-[ArIr(ttp)OH]- can give Ir(ttp)OH and ArH. Ir(ttp)OH then undergoes aromatic C-H bond activation reaction to give Ir(ttp)Ar'. Furthermore, the aromatic C-F bond activation products were found as the kinetic products, and aromatic C-H bond activation products were the thermodynamic ones.* / Part III describes the successful C(C=O)-C(alpha) bond activation of acetophenones by high-valent iridium porphyrin complexes (Ir(ttp)X, X = Cl(CO), (BF4)(CO), Me) in solvent-free conditions at 200°C to give the corresponding iridium porphyrin benzoyls (Ir(ttp)COAr) in up to 92% yield. Mechanistic studies suggest that Ir(ttp)X reacts with acetophenones to give alpha-CHA product as the primary product, which can re-convert back to the active intermediate Ir(ttp)OH or Ir(ttp)H in the presence of water formed from the concurrent iridium-catalyzed aldol condensation of acetophenones. Then Ir(ttp)OH cleaves the aromatic C-H bonds to produce the aromatic CHA products, which are more thermally stable than the alpha-CHA product. Both Ir(ttp)H and Ir(ttp)OH were the possible intermediates to cleave the C(C=O)-C(alpha) bond to give thermodynamic products of Ir(ttp)COAr. On the other hand, only Ir(ttp)(BF 4)(CO) can react with the aliphatic ketones, likely due to the stronger Lewis acidity and the HBF4 generated in catalyzing the aldol condensation of aliphatic ketones to facilitate the formation of Ir(ttp)OH and Ir(ttp)H.* / The objectives of the research focus on the bond activation chemistry by iridium porphyrin complexes with three organic substrates, (1) hydrosilanes (HSiR3), (2) fluorobenzenes (C6HnF6-n , n = 0--6), and (3) aromatic or aliphatic ketones (RCOR, R = alkyl or aryl). / Li, Baozhu. / Adviser: Kin Shing Chan. / Source: Dissertation Abstracts International, Volume: 72-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Choosing a stationary phase is the first step in developing a liquid chromatography (LC) separation method, where the selectivity is governed by the differential interactions of the analytes with the stationary and mobile phases. Introducing a gradient in stationary phase functionality allows for tuning of analyte retention, translating to a possible improvement in selectivity and an increase in resolution versus that offered by uniform stationary phases. In this work, C18-silica, phenylbutyl-silica, and phenylbutyl-ammonium opposed continuous stationary phase gradients were fabricated using controlled rate infusion (CRI) on particle packed LC columns. Characterization of the stationary phase was carried out using spectroscopy and LC analysis to relate the ligand density gradient profile to the observed chromatographic parameters. C18-silica gradients were created with a time-dependent acid hydrolysis infusion and demonstrated an increase in resolution when combined with a mobile phase gradient. Phenylbutyl-silica and phenylbutyl-ammonium gradients were produced using an in-situ silanization CRI method. Phenylbutyl-silica gradients were confirmed to be stable and reproducible; however, produced tailing peak shapes. Phenylbutyl-ammonium gradients were utilized to incorporate an ion exchange model into a simulator built by Jeong et al. The phenylbutyl-ammonium gradient was not reproducible but did exhibit an increase in resolution when combined with a mobile phase gradient. Also, the ion exchange model was successfully added within the simulator, with percent differences for retention prediction all under 5 %. This dissertation serves as a proof-of-concept for gradient stationary phases on particle packed LC columns.

Les plasmas et les poussières coexistent dans de nombreuses situations, aussi bien à l'état naturel (astrophysique) que dans l'industrie (microélectronique, nanotechnologie). Le milieu ainsi constitué est alors le siège de phénomènes nouveaux. Dans ce travail, différentes méthodes de formation des poussières (pulvérisation, gaz réactifs) ont été utilisées. Leur cinétique de croissance a été analysée et en particulier la formation de nanoparticules pour les applications industrielles. Les poussières acquièrent une charge négative en capturant une partie des électrons du plasma. Cette charge va fortement conditionner la dynamique et le piégeage du nuage de poussières au sein du plasma. La structure et le comportement du nuage ont ainsi été étudiés. La variation de densité électronique perturbe fortement le plasma et donne lieu à une grande variété d'instabilités qui ont été caractérisées. Finalement, le devenir de la charge électrique à l'arrêt de la décharge a été étudié.

Nous avons identifié, à l'aide d'un dispositif rhéo-optique contra-rotatif, les mécanismes de dispersion d'agglomérats de silice de précipitation (Z1115MP et Z1165MP) immergés dans une matrice visco-élastique (SBR 25E) soumise à un cisaillement et déterminé les paramètres clés qui jouent un rôle dans le processus de dispersion. Les effets de la nature de la silice, du greffage des agglomérats par un agent de recouvrement silane, de leur infiltration par les chaînes polymères et de la concentration en charges sur les critères et mécanismes de dispersion ont été étudiés. Les principaux résultats sont : <br />- La silice Z1165MP se disperse via un mécanisme de rupture et la silice Z1115MP via un mécanisme de désintégration. Ces deux mécanismes interviennent à partir d'une contrainte hydrodynamique critique. La silice Z1165MP est plus difficile à disperser que la silice Z1115MP. Les différences de mécanismes et de critères critiques de dispersion sont discutées en terme d'organisation structurelle des silices.<br />- Le greffage de la silice Z1115MP par un agent de recouvrement ne modifie pas le mécanisme observé mais réduit considérablement la cohésion des agglomérats et donc les contraintes hydrodynamiques critiques pour leur désintégration.<br />- Lorsque les agglomérats de silice Z1115MP sont intégralement infiltrés par la matrice élastomère, un nouveau mécanisme de dispersion est observé: le délitement. Il intervient à partir d'une contrainte hydrodynamique critique, directement proportionnelle au rayon des agglomérats.<br />- En milieu concentré, les deux types de silice se dispersent par des arrachements successifs de fragments induits par les collisions. Dans les mêmes conditions hydrodynamiques, la cinétique de dispersion d'un agglomérat de silice Z1165MP est cinq fois plus lente qu'un agglomérat de silice Z1115MP de même taille.<br />Tous ces résultats apportent des informations pertinentes sur les effets de différents paramètres sur les mécanismes de dispersion de la silice lors du procédé industriel de mélangeage.