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Chisham, Jason E. (Jason Edward). "Sol-gel materials for integrated optics." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=23992.
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The sol-gel process is a low temperature solution route to amorphous and crystalline materials. Organic modification of the precursors allows the formation of organic-inorganic composite materials. We use the sol-gel process to produce an organically-modified ceramic for integrated optical applications. Photosensitive organic components allow the fabrication of passive integrated optical devices by photolithography. We demonstrate the fabrication and characterization of channel waveguides, waveguide devices and gratings in this material. Active devices based on the emission of erbium at 1.55 $ mu$m are under much investigation because of their potential use in telecommunications. Luminescence quenching is a major problem as an Er$ sp{3+}$ ion in its excited state transfers its energy to a nearby vibrational mode of its environment and decays non-radiatively to the ground state. Encapsulation of the ion into a coordination sphere to shield the ion from its surroundings may lead to reduced quenching. We synthesize several erbium tetrakis $ beta$-diketone complexes and dope them into different solvent environments and sol-gel hosts to probe guest-host interactions in the excited state.
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Wallington, Sally-Ann. "Sol-gel materials for optical chemical sensing." Thesis, University of Kent, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308948.
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Savin, Shelley. "Sol-gel derived materials for chemical sensing." Thesis, University of Kent, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396920.
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Fan, Q. "Sol-gel materials for photoelectronic device applications." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366155.
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Hassan, Shereen Hassan Mohamed Gaber. "Sol-gel preparation of silicon nitride materials." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/72951/.
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Sol-gel techniques are mainly used for oxides but are of growing interest for non-oxide materials. They allow formation of solid materials through gelation of precursor solutions and can be used to control composition and to produce a large number of useful morphologies such as films, monoliths, aerogels, foams and materials with ordered pores on various length scales. Often the synthesis of non-oxide materials using sol-gel methods has focused on producing powders for applications such as catalysis, where controlled porosity and basic catalytic sites are the point of interest. In this thesis, formation of silicon nitride based materials as thin films, aerogels, inverse opal films and phosphor powders have been synthesised using non-oxide sol-gel methods. For thin films formation of amorphous silicon nitride, [Si(NHMe)4] solution in tetrahydrofuran (THF) with ammonia in the presence of a triflic acid catalyst was used. The sols formed from this mixture were used to make films using a simple dip coating technique. A number of coating and pyrolysis regimes have been compared. Aerogels were prepared through a small change in the sol preparation conditions leading to bulk gelation, supercritical drying was then applied to these gels. For templated films, the precursor was dissolved in hexane and polystyrene array tiles were coated with that solution using dip, drop or capillary techniques. The effects of several coating techniques and different pyrolysis temperatures on film morphologies have been studied. In addition, the sol-gel process offers an effective and controllable means of adding elements into Si-N matrix with the aim of combining the low reactivity of silicon nitride materials with other functional properties. Co-ammonolysis of a rare-earth amide with a silicon amide is shown to be an effective route to phosphor materials. Amorphous Tb:SiNx composition show strong photoluminescence and the variation in PL intensity with composition has been probed.
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Himmelhuber, Roland. "Sol-Gel Materials for Optical Waveguide Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/325227.
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Sol-gel materials are an important material class, as they provide for easy modification of material properties, good processability and routine synthesis. This allows for the tailoring of the material properties to the needs of specific device designs. In the case of electro-optic modulators with a coplanar or coplanar strip (CPS) electrode design, sol-gel cladding materials can be used to confine the light to the electro-optic material as well as to concentrate the electrical field used for poling and driving the modulator. Another important material property that can influence the poling efficiency is the conductivity of the material surrounding the electro-optic material, and this property can also be controlled. In this dissertation I discuss several approaches to altering the material properties of sol-gel materials in order to achieve a specific performance objective. The optical loss in the telecom regime as well the refractive index will be discussed. I will introduce a novel titania-based family of sol-gel materials, which exhibit very high refractive indices, tuneability and high dielectric constant (ε). Coplanar electrode design is useful for device platforms that do not allow for a microstrip geometry, such as silicon and Si₃N₄ devices. CPS electrodes however bring new challenges with them, especially optimizing the poling process. I will discuss a method for characterizing coplanar poled polymer films by a modified Teng-Man technique as well as with second harmonic microscope (SHM). SHM allows for an almost real-time mapping of the Pockels coefficient. The described method allows for quantitative measurements of the Pockels coefficient in a poled film with spatial resolution at the micron level. Finally, I will discuss the device design considerations for a silicon-EO hybrid modulator. Optimal dimensions for the silicon waveguide are shown and the feasibility of the proposed electrode design for high speed operation is theoretically shown. All design parameters, including electrode spacing and height are optimized towards the highest possible figure of merit. The functionality of a simple test device is shown. For Si₃N₄ waveguides optimal dimensions are found as well and the influence of a high ε sol-gel side cladding is examined.
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Holland, M. A. "Structural characterisation of novel sol-gel derived materials." Thesis, University of Kent, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369690.
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Phillips, Katherine Reece. "Sol-Gel Chemistry of Inverse Opals." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493452.
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Controlling nano to microscale structuration enables one to alter a material’s optical, wetting, mechanical, and chemical properties. Structuration on this scale can be formed from spherical building blocks; in particular, monodisperse, spherical colloids assemble into crystals that can be used to template an ordered, porous structure known as an inverse opal. The structure’s porosity and periodicity provide control over both light (photonic effects) and fluid flow (wetting effects). Controlling the composition allows chemical functionality to be added to the ordered, porous structure. Inverse opals are widely used in many applications that take advantage of these properties, including optical, wetting, sensing, catalytic, and electrode applications; however, high quality structures are necessary to maintain consistent properties. Many of their properties stem from the structure itself, so controlling inverse opals’ structure (including the local composition) provides the ability to control their properties, with the potential to improve some applications and potentially enable additional ones.
This thesis explores how molecular precursors can be used to control colloidal assembly and therefore alter the optical and wetting properties of high quality inverse opals. Using a bio-inspired approach, highly ordered, crack-free, silica inverse opals can be grown by co-assembling the colloidal template with a sol-gel matrix precursor using evaporation-induced self-assembly. Using sol-gel chemistry, the size, shape, and charge of the precursor can be controlled, which can be used to tune the colloidal assembly process. Here, we use the sol-gel chemistry of the precursors to control both the morphology and composition of these photonic structures.
In particular, temperature-induced condensation of the silica sol-gel matrix alters the shape of an inverse opal’s pores (Chapter 2), and silica and titania precursors can be mixed to make hybrid oxide structures (Chapter 3). Additionally, rationally designed precursors enable the fabrication of crack-free inverse opals in materials beyond silica, which we show for titania as a proof-of-concept (Chapter 4). By controlling the structure and composition with sol-gel chemistry, we can tailor both the optical and wetting properties, as discussed in the second part of each chapter; these properties have important effects for the various applications. In this way, sol-gel chemistry can be used to assemble inverse opals with complex functionality.<br>Chemistry and Chemical Biology
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Fabes, Brian David. "Strengthening of glass by sol-gel coatings." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14699.
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Silverman, Lee Arnold 1959. "Sol-gel derived tantalum oxide thin films." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14835.
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Glaser, Raymond Hans. "Structure-property behavior of sol-gel derived hybrid materials." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/54327.
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Structure-property studies were carried out on a number of different hybrid sol·gel materials. Multifunctional silicon ethoxides were prepared and studied by solid state ²⁹Si NMR and Raman spectroscopy to determine the type of silicate structures formed and the degree of conversion attained by the sol-gel process under previously established reaction conditions. New procedures were developed to incorporate titaniumisopropoxide as well as Al, Zr and Zn acetylacetonates into functlonalized polyltetramethylene oxide) modified sol-gel systems. The physical properties of titanium containing poIy(tetramethyIene oxide) modified sol-gel materials were studied in detail and correlated to morphological and structural information gained from dynamic mechanical analysis, small angle x-ray scattering and scanning electron microscopy. The incorporation of titanium was found to increase the measured Young’s modulus and stress at break relative to comparable materials based solely on TEOS.<br>Ph. D.
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Wingfield, Charles. "Fabrication of Anisotropic Sol-gel Materials by Photo-Crosslinking." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2706.
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This is a report on the fabrication and characterization of anisotropic, porous materials: functionally graded cellular and compositionally anisotropic aerogels. This new class of materials was fabricated by photopolymerization of selected regions of a homogeneous monolith using visible light. Visible light is not significantly absorbed and not significantly scattered by organic molecules and oxide nanoparticles in wet gels and it allows fabrication of deeply penetrating, well-resolved patterns. Simple variations of the exposure geometry allowed fabrication of a wide variety of anisotropic materials without requiring layers or bonding.
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Joardar, Saikat Sutej. "Siloxane modified hybrid materials by the sol-gel process." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-134057/.
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Doss, Calvin James. "Raman studies of the nanostructure of sol-gel materials." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164932/.
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Brennan, Anthony Bartholomew. "Structure/property behavior of inorganic/organic sol-gel derived hybrid materials." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-09162005-115036/.
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Sparks, Andrew William 1977. "Sol-gel synthesis of one-dimensional photonic bandgap structures." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9557.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.<br>Includes bibliographical references (p. 26-27).<br>A series of one-dimensional photonic bandgap devices were fabricated using SiO2 and TiO2 films deposited from solution by the sol-gel method. A dielectric mirror, or broadband interference filter, was fabricated by alternating quarter-wave optical thickness layers of the two films on a silicon substrate for a total of six layer pairs. This device exhibited an omnidirectional photonic bandgap of 450 nm in TE-polarization and 110 nm in TM-polarization. A microcavity, or narrowband filter, was fabricated with a TiO2 Fabry-Perot cavity sandwiched between two mirrors of three layer pairs each. The resonant cavity corresponded to a wavelength of roughly 1500 nm and shifted to shorter wavelengths with increasing incident angles. A maximum resonant quality factor of 11. 7 was achieved.<br>by Andrew William Sparks.<br>S.B.
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Hasegawa, George. "Studies on Porous Monolithic Materials Prepared via Sol-Gel Process." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157811.
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Noble, Kate. "Preparation of organically modified mesoporous materials via sol-gel processing." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340139.
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Newport, Anne Christine. "The sol-gel synthesis of anti-Stokes luminescent glass materials." Thesis, University of Greenwich, 2000. http://gala.gre.ac.uk/6257/.
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The materials commonly used and the synthetic problems that arise in the field of transparent glass materials with anti-Stokes luminescent properties are described. The literature has shown that rare earth doped oxide glasses, whilst chemically durable and relatively easy to manufacture, have weak anti-Stokes emissions, whereas rare earth doped fluoride materials have considerably improved anti-Stokes luminescence but are less chemically stable and highly reactive. Recent interest in glass ceramics has proposed alternative matrices with the advantages of both fluoride and oxide host materials. These materials consist of rare earth doped fluoride crystallites in an oxide glass matrix giving the emission characteristics of a fluoride crystal protected in the stable surroundings of an oxide matrix. The work in this thesis initially set out to build on these lattices but broadened in the light of the findings outlined below. The synthesis of silica based glasses using sol-gel techniques is covered thoroughly in this work and the incorporation of various cations into these matrices has been investigated. Amongst the cations added to silica sol-gel reactions are titania, alumina and yttrium. Their reactions and the factors that promote transparent and crystallite-free samples have been reported and discussed. Several advances in this field have been made including a detailed investigation into the synthesis and properties of yttrium based sol-gel reactions which have not been previously reported. The incorporation of fluorine into these materials has also been described and the various problems encountered have been examined. Several novel methods of incorporating fluoride ions into silica lattices are proposed and examined. It was found that in the presence of fluoride ions, the rare earth dopants form crystallites within the glass matrix. In a similar way, it was found that glass ceramics also formed when a titanium alkoxide is incorporated with fluoride ions during the sol-gel synthesis of these lattices. In these cases it was shown that TiO2 in the form of anatase or rutile crystallites can be grown in the glass matrix. Moreover the phase of TiCb grown can be easily controlled by choice of annealing temperature and firing times. Distinct anti-Stokes emissions are produced depending upon the form of titania present. These new materials are reported and discussed.
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Sierra, salazar Andrés Felipe. "Waterborne catalytic materials with original design." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2017. http://www.theses.fr/2017ENCM0014/document.
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Catalysis is one of the Green Chemistry Principles given its importance for limiting environmental impacts and improving current processes, as well as for developing new sustainable processes and products. In order to provide more performant catalysts, this study provides a novel preparation method for controlling the distribution of metal nanoparticles (NPs) within hierarchically meso- and macroporous catalysts. It consists of the combination of latex synthesis, sonochemistry and sol-gel process. All these steps can be carried out in water, reducing environmental impact. The first step is the synthesis of latex, typically polystyrene. The second step is the sonochemical synthesis and deposition of noble metal NPs on the surface of the latex polymer. The third step is the synthesis of the support by sol-gel process using tetraethyl orthosilicate (TEOS) under controlled conditions to modulate the porosity of the final silica matrix. As a result, an original catalyst morphology is obtained with active sites preferentially located within the macropores, which are surrounded by a mesoporous matrix. Using this approach, a monodisperse polystyrene latex (~130 nm) was prepared by emulsion polymerisation and then decorated with Pt NPs (~2.3 nm) by sonochemical reduction. The mesoporous silica support was prepared by sol-gel synthesis in the presence of the decorated latex. After calcination, the organic template left behind macropores with the Pt NPs within the generated macropores. Mesopores (2-15 nm) connecting these macropores (110-400 nm) were tuned by varying the synthesis conditions. Typically, specific surface areas of 615 m2/g and total pore volumes of 0.74 cm3/g were obtained. In a first case of study, hierarchically porous Pt/SiO2 catalysts were evaluated in the selective hydrogenation of p-chloronitrobenzene (p-CNB) to produce p-chloroaniline. They exhibited activities up to 91.7 ± 2.9 molCNB/(min molPt) and selectivity values up to 100 ± 2% at 80% of conversion, in comparison with 47.7 ± 2.9 molCNB/(min molPt) and 91 ± 2%, respectively, obtained with a commercial catalyst under the same conditions. Moreover, in a second case of study, it was possible to prepare silica-supported Pd, Pd-Pt and Pd-CeO2 catalysts with hierarchical porosity (meso and macro). These materials were tested in the direct synthesis of hydrogen peroxide from hydrogen and oxygen. The best productivity of H2O2 was obtained with the bimetallic Pd-Pt catalyst with 32500 molH2O2/(h molmetal) in batch, and the best selectivity was obtained with Pd-CeO2/SiO2 catalyst (63 ± 2%) in semi-batch. In summary, this thesis proposes a new aqueous preparation method for hierarchically porous functional materials by the combination of latex synthesis, sonochemical reduction and sol-gel process. It has been demonstrated that this preparation technique provides a very powerful and versatile toolbox for catalyst tailoring and optimisation. Further perspectives to achieve improved morphologies and controlled active sites distribution are also proposed<br>La catalyse est l'un des piliers pour le développement de procédés durables, car elle permet d'utiliser moins de ressources en accélérant les réactions chimiques. Afin de fournir des catalyseurs plus performants, cette étude propose une nouvelle méthode de préparation de catalyseurs pour contrôler la distribution de nanoparticules (NPs) métalliques au sein des catalyseurs hiérarchiquement poreux (méso et macro) en combinant la synthèse de latex, la réduction sonochimique et le procédé sol-gel. La première étape est la synthèse d'une empreinte porogène de billes de polystyrène (latex) obtenues par polymérisation en émulsion aqueuse. La deuxième étape est la synthèse et le dépôt de NPs de métaux nobles sur la surface des billes de polymère par voie sonochimique dans l’eau. La troisième étape est la synthèse du support catalytique par un procédé sol-gel en milieu aqueux en utilisant le latex décoré et l’orthosilicate de tétraéthyle (TEOS) dans des conditions contrôlées pour moduler la porosité finale de la matrice de silice (mésoporeuse). Toutes les étapes de cette approche sont effectuées dans l'eau, ce qui limite les impacts environnementaux de la préparation du catalyseur. L'élimination du porogène (latex) par calcination génère les macropores. Le matériau résultant possède alors une morphologie inédite pour un catalyseur, avec des macropores fonctionnalisés par des NPs métalliques, dans une matrice de silice mésoporeuse. Ainsi, il a été possible de synthétiser un latex monodisperse de polystyrène (~130 nm), lequel a été décoré avec des NPs de Pt (~2.3 nm) par réduction sonochimique. Le matériau final de silice a présenté des mésopores (2-15 nm) reliant les macropores (110-400 nm) contenant les NPs de Pt. Il a été possible d'obtenir des surfaces spécifiques et des volumes poreux totaux de 615 m2/g et 0,74 cm3/g, respectivement. Dans un premier cas d'étude, des catalyseurs de Pt/SiO2 à porosité hiérarchique ont été évalués dans l'hydrogénation sélective du p-chloronitrobenzene (p-CNB) pour produire la p-chloroaniline. Ils ont présenté des activités catalytiques allant jusqu'à 91,7 ± 2,9 molCNB/(min molPt) et des sélectivités jusqu'à 100 ± 2% à 80% de conversion, par rapport à 47,7 ± 2,9 molCNB/(min molPt) et 91 ± 2%, respectivement, obtenus dans les mêmes conditions avec un catalyseur commercial. Dans un deuxième cas d'étude, des catalyseurs à base de Pd, Pd-Pt et Pd-CeO2 supportés sur de la silice à porosité hiérarchique ont été préparés et testés dans la synthèse directe du peroxyde d'hydrogène. La meilleure productivité a été obtenue avec le catalyseur bimétallique Pd-Pt avec 32500 molH2O2/(h molmétal) en batch, et la meilleure sélectivité a été obtenue avec le catalyseur Pd-CeO2/SiO2 (63 ± 2%) en semi-continu. En résumé, cette thèse propose une nouvelle méthode de préparation dans l’eau de matériaux fonctionnels à porosité hiérarchique en combinant la synthèse de latex, la réduction sonochimique et le procédé sol-gel. Il a été démontré que cette technique de préparation fournit une boîte à outils très puissante et polyvalente pour la préparation et l'optimisation des catalyseurs. Des perspectives pour améliorer davantage les morphologies et la distribution contrôlée des sites actifs sont également proposées
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Suratwala, Tayyab Ishaq 1970. "Photostability of laser dyes in sol-gel-derived hosts." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290697.
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Improving the photostability of laser dyes within sol-gel derived hosts has been the focus of this study. To accomplish this, synthetic routes were established to incorporate laser dyes within various sol-gel matrices, the mechanisms of dye photodegradation were determined, and molecular engineering techniques were employed to improve the photostability of the dye doped sol-gel hosts. Various Coumarin (silylated and unsilylated) and Pyrromethene laser dyes were incorporated within sol-gel derived hosts ranging from SiO₂ xerogel films to SiO₂:PDMS Polyceram monoliths which were optically transparent, crack-free, and polishable. Processing parameters, such as the water content and the pre-hydrolysis of the silylated Coumarin dyes, greatly affected the degree of dye bonding. The chemical stability of the Pyrromethene laser dye was also greatly affected by processing parameters, such as the acid/base content. Both the Coumarin and Pyrromethene dyes were found to degrade by photo-oxidation processes. Therefore, it was expected that the photostability would improve by incorporating the dye molecules within molecular cages within the solid hosts, thereby preventing interactions of the dye with photo-reactive impurities such as oxygen. The photostability was found to improve using the following molecular engineering methods: (1) by covalently bonding the dye to the host matrix, where the photostability improvement was attributed to the greater probability of obtaining dye caging with the silylated dye; (2) by removing porosity within the host through control of sol-gel processing and composition, where the photostability improvement was attributed to the elimination of highly photo-reactive dyes located in the pores of the host; (3) by incorporating additives such as bases and hindered amine antioxidants which slowed the steps of the photodegradation process. The fluorescence photostability (fluorescence output intensity as a function of pump pulses) of the dye doped films and monoliths showed a characteristic behavior in the fluorescence output, signified by a rapid initial decay (attributed to dyes located within pores of the matrix) and then a slower long-term decay (attributed to photostable dye molecules located within SiO₂ cages). A model, which applied a Gaussian distribution of the photostabilities of the dye molecules, quantitatively described the observed photostability behavior of the dye doped samples.
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Gao, Xiaonan. "Sol-Gel Assembly of Metal Nanostructures into Metallic Gel Frameworks and Their Applications." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4319.
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The advent of nanoscience and nanotechnology has sparked many research forefronts in the creation of materials with control over size, shape, composition, and surface properties.1,2 However, for most of the applications, nanoscale materials need to be assembled into functional nanostructures that exhibit useful and controllable physical properties. Therefore, numerous efforts on the assembly of nanoparticles (NPs) using organic ligands, polymers and polyelectrolytes have been reported.3,4 However, the interactions between NPs are mediated by intervening ligands, which are detrimental to charge transport and limit the thermal stability. Hence, developing a new method to produce solid state nanostructures with direct NP linkage has become a significant challenge. To avoid the bridging ligands and improve the conductivity of NP based solid state structures, a novel strategy has been developed in which colloidal NPs undergo condensation to wet “jello-like” hydrogel with direct interfacial linkage. Then hydrogels can be dried supercritically to produce aerogels.5 Resultant nanostructures exhibit low densities, large open interconnected pores, and high internal surface areas and are containing entirely of colloidal metal NPs.6 Since noble metal NPs have been widely used in applications such as catalysts, sensors, and novel electrochemical device components, we herein expanded the sol-gel method to noble metal NPs to produce a new class of metal aerogels.
In the dissertation, the synthesis of hollow Ag hollow NPs, Au/Ag alloy NPs, and Au/Pt/Ag alloy hollow NPs with tunable sizes and physical properties, and their oxidative-assembly into high-surface-area, mesoporous, self-supported gel framework has been achieved. The gelation kinetics have been controlled by tuning the oxidant/thiolate molar ratio that governs the rate of NP condensation, which in turn determines the morphology, optical transparency, surface area, and porosity of the gel frameworks. These low-density mesoporous nano-architectures displaying optical transparency or opacity, enormously surface area, and interconnected meso-to-macro pore structure are promising candidates for catalytic, electrocatalytic, and SERS-based sensing applications. The SERS activity of Au/Ag alloy aerogels has been studied and significant signal enhancement was achieved. The performance of the Au/Pt/Ag aerogel towards methanol oxidation reaction has been studied via cyclic voltammetry and significant electro-catalytic activity was observed.
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Hayase, Gen. "Studies on sol-gel-derived monolithic porous polyorganosiloxanes." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188507.
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Sun, Zhengfei Wei Yen. "Novel sol-gel nanoporous materials, nanocomposites and their applications in bioscience /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/556.
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Fragkiadakis, Charalampos. "Integration of sol-gel frequency agile materials for tunable RF devices." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/7309.
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This thesis focuses on the use of high permittivity tunable dielectrics and more specifically sol-gel ferroelectric thin films for low cost, high performance tunable devices such as varactors and filters at RF and microwave frequencies. The top- ics covered include measurement techniques for the characterization of tunable dielectrics at low and microwave frequencies, fabrication processes, electrical and acoustic modeling of thin film ferroelectric varactors, performance optimization using conductive electrodes, realization of tunable microwave circuits and inte- gration of tunable dielectrics with conventional bulk acoustic wave resonators (FBAR). A lead strontium titanate (PST) sol-gel ferroelectric varactor is designed, elec- trically and acoustically modeled and fabricated, displaying dielectric tunability of "'-'75%. A two port automatic extraction technique using MATLAB allowing the de-embedding of parasitic connecting transmission lines, as well as parasitic pads has been developed and presented, yielding accurate dielectric permittivity values in good agreement with literature. The potential factors that may compro- mise the electrical performance of the ferroelectric tunable varactor are analyzed and a novel Au/Ti02 bottom electrode stack process is proposed and shown to improve the RF performance of the tunable varactor lowering the overall metaliza- tion resistance and improving performance, compared to the commonly used Pt electrodes. To establish the possibility of tunable microwave systems integrating sol-gel ferroelectric tunable varactors the following novel microwave devices are designed, modeled and fabricated: A ferroelectric varactor-based RF resonant switch, integrating a thin film sol- gel PST ferroelectric varactor with a high Q micro-machined inductor is fabri- cated. An insertion loss of ",1.5 dB and isolation of ",18 dB have been achieved for a single 7 GHz resonant switch with a device area of 0.6 mm x 1 mm. The intrinsic performance limitations of this type of device due to the ferroelectric thin film are discussed and the implementation of cascaded switches and state-of-the- art ferroelectric materials for further improvement of performance of this device, have been considered and simulated. Tunable band-stop resonators and notch filters using sol-gel PST ferroelectric varactors in a coplanar waveguide (CPW) defected ground structure are fabricated and measured. The PST varactors tune single resonators and 3-pole band-stop filters, operating at the center frequency of 4 and 8 GHz, having a maximum rejection of more than 13.8 dB at the stop band, while the insertion loss at the pass band is less than 3 dB. Full-wave analysis is performed to identify the critical points, where PST varactors are implemented to adjust the resonance frequency of the devices. An optimized fabrication process allows for fabrication of a 3-stage filter with a maximum rejection of 28 dB, albeit with a reduced tuning range, possibly due to DC bias path leakage. Finally, a fabrication approach where a ferroelectric varactor is integrated with a conventional zinc oxide (ZnO) acoustic wave resonator is presented. The approach avoids the piezoelectric thin film degradation due to the ferroelectric annealing by first fabricating the ferroelectric varactor and superimposing the conventional FBAR on top of it. The tuning of the series resonant frequency of a conventional ZnO FBAR with a ferroelectric varactor is demonstrated. Field induced deformation limits the maximum shift of the resonance to 0.45% at 1.5 GHz, for 41% tunability of the ferroelectric varactor, suggesting a big scope for possible improvements in performance by improving the design and fabrication. VIII.
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Malek, Mohamad Zahid Abdul. "Synthesis, processing and characterisation of photochromic dye doped sol-gel materials." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310760.
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Li, Chenghong. "Inorganic-Organic Sol-Gel Derived Hybrid Materials as Abrasion Resistant Coatings." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/39013.
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Inorganic-organic hybrid materials have been developed using sol-gel reactions of a trialkoxysilylated organic compound and a metal or semi-metal alkoxide and applied as coatings on polymeric or metallic substrates. Many of these coatings have demonstrated good to excellent abrasion resistance.
Abrasion resistant coatings were prepared by hydrolysis and condensation of mixtures of a triethoxysilylated diethylenetriamine (f-DETA), tetramethoxysilane (TMOS), water and an alcohol in the presence of an acid catalyst (a one-step hydrolysis approach). The influences of many formulation and processing variables on the gelation time, optical properties, hardness and abrasion resistance were investigated. An aminolysis mechanism was also proposed to explain the adhesion between sol-gel derived coatings and polycarbonate substrates promoted by a 3-aminopropyltriethoxysilane (3-APS) primer. FT-IR, GPC, 1H and 13C NMR, XPS experiments were conducted to support this mechanism.
The f-DETA/TMOS system is essentially a binary system of an alkyltriethoxysilane (T) and a tetraalkoxysilane (Q). At pH 0-2 and pH 4-5, the relative condensation reactivities of the T and Q species in this system were compared using 29Si NMR spectroscopy. After thermal curing, 13C or 29Si solid state NMR spectroscopy was used to estimate the extent of hydrolysis of the urea linkages in f-DETA, the concentration of residual alkoxysilane groups, and the extent of condensation for both T and Q species. The dependence of the morphology of f-DETA/TMOS gels on the pH and the water concentration was also investigated using AFM, SEM and SAXS.
Many other trialkoxysilylated organic compounds containing urea, urethane, epoxy and siloxane linkages were also synthesized and utilized to prepare abrasion resistant coatings via a one-step hydrolysis approach, a two-step hydrolysis approach or a moisture-curing approach. Coatings derived from many of these systems or approaches demonstrated abrasion resistance comparable to that of the f-DETA/TMOS coating. Thin coatings were also derived from cubic octasilicate monomers via hydrosilylation or sol-gel reactions. These coatings were very transparent but unfortunately lacked abrasion resistance.<br>Ph. D.
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Lu, Dong. "Hybrid organic-inorganic sol-gel materials and components for integrated optoelectronics." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280624.
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On the technical platform of hybrid organic-inorganic sol-gel, the integrated optoelectronics in the forms of heterogeneous integration between the hybrid sol-gel waveguide and the high refractive index semiconductors and the nonlinear functional doping of disperse red chromophore into hybrid sol-gel is developed. The structure of hybrid sol-gel waveguide on high index semiconductor substrate is designed with BPM-CAD software. A hybrid sol-gel based on MAPTMS and TEOS suitable for lower cladding for the waveguide is developed. The multi-layer hybrid sol-gel waveguide with good mode confinement and low polarization dependence is fabricated on Si and InP. As proof of concept, a 1 x 12 beam splitter based on multimode interference is fabricated on silicon substrate. The device shows excess loss below 0.65 dB and imbalance below 0.28 dB for both TE and TM polarization. A nonlinear active hybrid sol-gel doped with disperse red 13 has been developed by simple co-solvent method. It permits high loading concentration and has low optical loss at 1550 nm. The second-order nonlinear property of the active sol-gel is induced with corona poling and studied with second harmonic generation. A 3-fold of enhancement in the poling efficiency is achieved by blue light assisted corona poling. The chromophore alignment stability is improved by reducing the free volume of the formed inorganic network from the sol-gel condensation reaction. An active sol-gel channel waveguide has been fabricated using active and passive hybrid sol-gel materials by only photopatterning and spin-coating. An amplitude modulator based on the active sol-gel containing 30 wt.% of DR13 shows an electro-optic coefficient of 14 pm/V at 1550 nm and stable operation within the observation time of 24 days.
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Burglova, Kristyna. "Design of easily accessible organosilanes for functional sol-gel hybrid materials." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2012. http://www.theses.fr/2012ENCM0021.
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Les organosilices sont des matériaux en plein essor, qui combinent les propriétés des fragments organiques et ceux de la matrice siliciée. Ces matériaux hybrides ont trouvé des applications dans les domaines de la catalyse, de l'optique, de l'électronique etc. Ils peuvent être préparés par le procédé sol-gel à partir d'organosilanes contenant des fragments organiques à propriétés désirées. Pour former ces matériaux, il est essentiel de simplifier la préparation des organosilanes fonctionnels en réduisant le nombre d'étapes réactionnelles. Aussi, l'un des buts de cette thèse est de développer une méthode de préparation sélective, universelle et à spectre large pour les organo(trialcoxy)silanes. Dans ce but, la réaction Click de CuAAC, connue comme une approche simple de couplage, a été adaptée pour les composés sensibles à l'eau. En utilisant des azotures ou des alcynes contenant la fonction triéthoxysilane avec des partenaires organiques, nous avons réussi à préparer des séries de précurseurs silylés par réaction Click. La réaction est rapide, quantitative et sélective, et tolère une gamme étendue de substrats. De plus, de nouveaux alcynes et azotures comportant deux fonctions triéthoxysilyle ont été préparés, afin d'être clickés sur différentes molécules organiques. Ces précurseurs bissilylés sont des organo(triéthoxy)silanes clickables, précurseurs de silsesquioxanes pontés. En utilisant des molécules fonctionnelles comportant un seul site de dérivatisation, des organosilanes pontés peuvent être obtenus, présentant un fragment organique pendant. De plus, un précurseur contenant une fonction alcyne protégée a été obtenu, ce qui permettra la formation de matériaux multifonctionnels. Certains des précurseurs sol-gel obtenus ont été transformés en matériaux hybrides par le procédé sol-gel. Ceux contenant des fragments organiques connus comme des ligands chiraux actifs ont été choisis pour des tests en catalyse asymétrique. Par ce biais, des ligands chiraux supportés ont été formés, et testés pour quelques réactions bien connues. De plus, cette thèse s'est intéressée à la nano-structuration de matériaux. Des molécules contenant des systèmes aromatiques et des fonctions urée, capables de s'auto-assembler grâce à des interactions non covalentes, ont été conçues et préparées. Dans certains cas, en particulier les systèmes à base de Binol avec des fonctions urée, des nanostructures régulières ont été observées sur des surfaces localisées. En conclusion, les travaux présentés dans cette thèse ont apporté de nouvelles possibilités pour la synthèse d'organo(triéthoxy)silanes, ainsi que des matériaux hybrides à propriétés et applications ciblées<br>Organosilicates are attracting considerable attention, owing to the combined properties of the organic fragment and inorganic silica matrix. These hybrid materials have found application in catalysis, optics, electronics, etc. They can be prepared by the sol-gel hydrolysis of functional organosilanes with the desired properties. To apply these materials in industry, it is essential to make the preparation of these silylated precursors easier and more efficient by reducing the number of reaction steps. Therefore one of the aims of this thesis is to develop a universal, wide scope and selective method of preparation for trialkoxyorganosilanes. For this purposes the “CuAAC reaction”, known for its simple approach, has been adapted for water-sensitive substrates. Using a silylated azide or silylated alkyne with an organic counterpart, we were able to prepare a series of clicked sol-gel precursors. The reaction is quantitative, fast, and selective and tolerates a wide range of substrates. Moreover, new bissilylated alkynes and azides which can be clicked to various organic molecules were prepared. They represent new families of bridged organotrialkoxysilanes to which a desired organic molecule, bearing only one bonding site, can be incorporated as a pending group with a targeted functionality. Furthermore, a bissilylated precursor bearing a protected alkyne function was prepared, allowing the synthesis of bifunctional materials. Some of the prepared precursors were transformed into hybrid silicas by the sol-gel process. Those containing organic molecules known as active chiral ligands for enantioselective reactions were chosen. By this way, supported chiral ligands were formed and we tested their activity according to known reactions. Additionally, in this thesis the structuring of the materials was also attempted. Molecules bearing aromatic systems and urea functions, which are capable of self-organization thanks to the weak non-covalent bonding interactions, were designed and prepared. In some cases, especially Binol systems with urea function, regular nanostructures on localized areas have been observed. Overall, this thesis brings new possibilities in the synthesis of both trialkoxyorganosilanes precursors and hybrid materials with desired properties and applications
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Neto, Elias Paiva Ferreira. "Filmes híbridos fotocrômicos de Ormosil-fosfotungstato dopados com os cátions divalentes Zn2+, Mg2+, Ca2+, Sr2+e Ba2+." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-12092014-155541/.
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Neste trabalho, materiais fotocrômicos foram preparados pela imobilização de um heteropolioxometalato do tipo Keggin, fosfotungstato [PW12O40]3- (HPW) em uma matriz híbrida do tipo Ormosil (do inglês Organically Modified Silicates). Estudou-se o impacto da adição dos cátions divalentes Zn2+, Mg2+, Ca2+, Sr2+ e Ba2+ sobre as propriedades dos filmes de Ormosil-Fosfotungstato. Os materiais foram preparados pelo método sol-gel e depositados na forma de filmes em diferentes substratos pela técnica de dip-coating. A formação da rede híbrida de organosilicato e a presença do [PW12O40]3- com sua estrutura de Keggin intacta nos materiais foram comprovadas pelas técnicas de espectroscopia vibracional (FTIR e Raman). Os difratogramas de raios-X das amostras de xerogéis demonstram que os materiais apresentam caráter semicristalino, sendo que um pico na região de 2θ<10° sugere a formação de unidades discretas de octasilsesquioxanos e/ou lamelas de silicato. Estudos de microscopia eletrônica de transmissão revelaram que a adição dos cátions durante a síntese induz a precipitação de nano-aglomerados constituídos de HPW e dos cátions dopantes. A análise do XANES na borda K do Zn sugere que os cátions dopantes Zn2+ estão associados aos heteropoliânions em aglomerados do sal [Zn(OH2)6]x/2Hx-3PW12O40. A imobilização destes aglomerados na rede de organosilicato durante a deposição dos filmes acarreta na preparação de filmes com maior quantidade incorporada de fosfotungstato, como demonstrado pela análise de XRF. A formação dos aglomerados é favorecida pela presença dos cátions maiores, sendo que a adição do Ba2+, que possui maior raio iônico dentre os cátions aqui estudados, permite a incorporação de quase sete vezes mais fosfotungstatp no filme de Ormosil. Essa maior incorporação dea espécie fotoativa nos filmes híbridos se reflete no aumento resposta fotocrômica dos filmes dopados de 35% (amostra dopada com Mg2+) até 685% (amostra dopada com Ba2+). Assim, a adição dos cátions, sobretudo daqueles com maior raio iônico, durante a síntese sol-gel do nanocompósito Ormosil-fosfotungstato representa uma estratégia simples e bastante reprodutível para a preparação de filmes com propriedades fotocrômicas aprimoradas. A elevada resposta fotocrômica dos filmes dopados os torna bons candidatos a serem aplicados como dosímetros colorimétricos da radiação UV.<br>In this study photohromic materials wer prepared by the entrapment of the Keggin heteropoyoxometalate phosphoungstate [PW12O40]3 (HPW) in a Ormosil (Organically Modified Silicates) hybrid matrix. We evaluated the impact of the addition of the divalent cations Zn2+, Mg2+, Ca2+, Sr2+ and Ba2+ on the properties of Ormosil-phosphotungstate films. The materials were prepared by sol-gel route and deposited as thin films on different substrates by dip coating method. The formation of the hybrid organosilicate network and the presence of the Keggin heteropolianion [PW12O40]3- were confirmed by FTIR and Raman vibrational spectroscopies. The x-ray diffractograms of the xerogels samples indicated that the materials present semi-crystalline behavior. A broad diffraction peak in the 2θ<10° region pointsto the possible formation octasilsesquioxane discrete units and/or silicate lamellae. Transmission electron microscopy studies revealed that the cations addition during the sol-gel synthesis induces the precipitation of nano-agglomerates composed of HPW and the doping cations. Zn K-edge XANES analysis suggests that the Zn2+ doping cations are associated to the heteropolianions forming [Zn(OH2)6]x/2Hx-3PW12O40 salt agglomerates. The entrapment of these agglomerates in the organosilicate network during dip-coating deposition results in the preparation of films with enhanced incorporation of phosphotungstate as demonstrated by XRF analysis. Ba2+ doping enhances in almost seven times the amount of incorporated phosphotungstate. This behavior is explained by the fact that as the solubility of polyoxometalate salts greatly decreases with the increase counter cation size, the formation of the agglomerates is favored in the presence of the larger cations (Sr2+ and Ba2+). The enhanced incorporation of the photoactive specie reflects on the phtochromic response of the doped hybrud films, wich increases in the range of 35% (Mg2+ doped sample) to 685% (Ba2+ doped sample). Therefore, the addition of the cations during sol-gel synthesis of the Ormosil-phosphotungstate nanocomposite represents a simple and reproducible strategy for the preparation of films with enhanced photochromic properties. These highly photochromic hybrid films are promising candidates for the design of practical UV-sensing devices and dosimeters.
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Venz, Paul Andrew. "Anion chemistry in the sol-gel processing of titania." Thesis, Queensland University of Technology, 1999.
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Anderson, Ruth. "A study of the atomic-scale structure of novel glass materials." Thesis, University of Kent, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267368.
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Clavel, Guylhaine. "Magnetic impurities in nanostructured materials." Doctoral thesis, Montpellier 2, 2009. http://www.theses.fr/2009MON20121.
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Doutoramento em Química<br>Os resultados apresentados aqui foram alcançados no âmbito do programa de doutoramento intitulado “Impurezas Magnéticas em Materiais Nanoestruturados”.
O objectivo do estudo foi a síntese e caracterização de óxido contendo impurezas magnéticas. Durante este trabalho, sínteses de sol-gel não-aquoso têm sido desenvolvidos para a síntese de óxidos dopados com metais de transição (ZnO e ZrO2). A dopagem uniforme é particularmente importante no estudo de semicondutores magnéticos diluídos (DMSs) e o
ponto principal deste estudo foi verificar o estado de oxidação e a estrutura local do dopante e para excluir a existência de uma fase secundária como a
origem do ferromagnetismo. Para alargar o âmbito da investigação e explorar plenamente o conceito de "impurezas magnéticas em materiais
nanoestruturados" estudamos as propriedades de nanopartículas magnéticas dispersas em uma matriz de óxido. As nanopartículas (ferrita de cobalto) foram depositadas como um filme e cobertas com um óxido metálico semicondutor
ou dielétrico (ZnO, TiO2). Estes hetero-sistemas podem ser considerados como a dispersão de impurezas magnéticas em um óxido. As caracterizações exigidas por estes nanomateriais têm sido conduzidas na Universidade de Aveiro e Universidade de Montpellier, devido ao equipamento complementar.<br>Les résultats présentés ici ont été réalisés dans le cadre du programme doctorat intitulé "impuretés magnétiques dans les matériaux nanostructurés". Cette étude avait comme objectif la synthèse et la caractérisation d'oxydes contenant des impuretés magnétiques. Durant ces travaux, nous avons développé des voies de synthèses par sol-gel non-aqueux pour la synthèse d'oxydes dopés par des métaux de transition (ZnO et ZrO2). Un dopage homogène est particulièrement important dans l'étude des semi-conducteurs magnétiques dilués (DMSs), et le point principal de cette étude était de vérifier l'état d'oxydation et l'environnement local du dopant, ainsi que d'exclure l'existence d'une phase secondaire, comme l'origine du ferromagnétisme. Pour élargir le champ de recherche et étudier pleinement la notion d' "impuretés magnétiques dans les matériaux nanostructurés" Nous avons étudié les propriétés magnétiques de nanoparticules dispersées dans une matrice d'oxyde. Les nanoparticules (ferrite de cobalt) ont été déposées sous forme de film et recouvertes d'un oxyde métallique semi-conducteur ou diélectrique (ZnO, TiO2). Ces hétéro-systèmes peut être considérés comme une dispersion d'impureté magnétique dans un oxyde. Les caractérisations requises par ces nanomatériaux ont été réalisées à l'Université d'Aveiro et l'Université de Montpellier en raison des équipements complémentaires disponibles<br>The results presented here have been achieved under the PhD program entitled “Magnetic Impurities in nanostructured materials”. This study had as purpose the synthesis and characterization of oxidic semiconductor containing magnetic impurities. During this work we have developed non-aqueous sol-gel routes, leading to well controlled oxide nanomaterials, to the synthesis of transition-metal doped oxides (ZnO and ZrO2). Homogeneous doping is particularly important in the comprehensive study of diluted magnetic semiconductors (DMSs), and the main point of this study was to ascertain the oxidation state and local structure of the dopant, as well as to exclude the existence of secondary phase as the origin of ferromagnetism. To enlarge the field of research and fully explore the concept of “Magnetic Impurities in Nanostructured Materials” we have studied the magnetic properties of nanoparticles embedded in an oxide matrix. The nanoparticles (cobalt ferrite) were deposited as a film and coated by a semiconducting or dielectric metal oxide (ZnO, TiO2). These hetero-systems can be regarded as dispersion of magnetic impurities in oxides. The characterization needed by these nanomaterials was performed at the University of Aveiro and University of Montpellier because of complementary available equipments
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Passos, Aline Ribeiro [UNESP]. "Aluminas macro-mesoporosas produzidas pelo método sol-gel para aplicação em catálise heterogênea." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/136086.
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000854657.pdf: 7039373 bytes, checksum: e3e464e79dbd92c0c088c22c6648dea7 (MD5)<br>Alumina é um suporte importante em catálise heterogênea. O controle das propriedades física e texturais pode melhorar seu desempenho como suporte em aplicações de catálise. Os catalisadores de cobalto são conhecidos por apresentarem excelente performance na reação de reforma de etanol (ESR) devido a elevada capacidade de quebra das ligações C-H e C-C. Muitos estudos visam correlacionar as propriedades das aluminas com o desempenho dos catalisadores. As aluminas exibem uma química de superfície complexa que pode ser controlada pelo método de preparação. Neste trabalho aluminas com meso e macroporos foram obtidas usando o método sol-gel acompanhado de separação de fases. Nesta estratégia integrativa a gelatinização e a separação de fases ocorrem de maneira espontânea no sistema contendo um indutor de separação de fases. Diferentes alumina foram produzidas a partir do isopropóxido e cloreto de alumínio e do óxido de polietileno e óxido de polipropileno como indutores de separação de fases. A escolha apropriada da composição de partida permite o controle do tamanho e volume dos poros. Os macroporos são formados como resultado da separação de fases após remoção do indutor de separação de fases, enquanto os mesoporos são formados entre as partículas do xerogel. As diferentes aluminas porosas preparadas e uma alumina comercial foram utilizadas como suporte de catalisadores de cobalto. Os precursores óxidos dos catalisadores obtidos após calcinação são compostos pelas fases Co3O4 e CoAl2O4, esta última em maior quantidade nas aluminas sintetizadas via sol-gel. As aluminas sol-gel possuem maior proporção de Al em sítios octaédricos e grupos hidroxilas superficiais do que a alumina comercial, verificou-se que estas características podem facilitar a migração de íons de Co na rede da alumina levando a maior formação de CoAl2O4. Os catalisadores foram...<br>Alumina is an important support for heterogeneous catalysts. The matching of appropriate alumina physical properties and controlled textural properties can improve its performance as support in catalysis applications. Cobalt based catalysts have been reported to have a good ethanol steam reforming (ESR) performance due to their high activity for the cleavage of C-H and C-C bonds. Many studies have been conducted about the effects of alumina properties on the cobalt catalysts properties. Alumina exhibits a rather complex surface chemistry which can be controlled by the preparation procedure. In this work alumina samples with macro and mesoporous structure were obtained using the one-pot sol-gel synthesis accompanied by phase separation. In this integrative strategy both processes, gelation and phase separation, spontaneously occur in system containing the presence of the phase separation inducer. The different aluminas were produced by using as aluminum reactants, aluminum isopropoxide and chloride and polyethylene oxide or polypropylene oxide as phase separation inducer. Appropriate choice of the starting composition allows the control the pore size and volume. Macroporous are formed as a result of phase separation after burning the phase separation inducer, while voids between particles of the xerogel skeletons form a mesoporous structures. The different alumina porous alumina and commercial alumina were used as supports for preparing by wetness impregnation cobalt-based catalyst. The oxidic catalyst precursors obtained after calcination are composed of Co3O4 and CoAl2O4-like phases, the latter being in higher proportions in the sol-gel alumina than in the commercial one. As the sol-gel alumina presents a larger amount of octahedral AlVI sites and surface hydroxyl groups than the commercial alumina, it was assumed that these features can facilitate the migration of Co ions into the alumina network...
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Passos, Aline Ribeiro. "Aluminas macro-mesoporosas produzidas pelo método sol-gel para aplicação em catálise heterogênea /." Araraquara, 2015. http://hdl.handle.net/11449/136086.
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Orientador: Celso Valentim Santilli<br>Orientador: Valérie Briois<br>Co-orientador: Leandro Martins<br>Banca: Pedro de Oliveira<br>Banca: Sylvain Cristol<br>Banca: Victor Luis dos Santos Teixeira da Silva<br>Banca: Douglas Gouvêa<br>Resumo: Alumina é um suporte importante em catálise heterogênea. O controle das propriedades física e texturais pode melhorar seu desempenho como suporte em aplicações de catálise. Os catalisadores de cobalto são conhecidos por apresentarem excelente performance na reação de reforma de etanol (ESR) devido a elevada capacidade de quebra das ligações C-H e C-C. Muitos estudos visam correlacionar as propriedades das aluminas com o desempenho dos catalisadores. As aluminas exibem uma química de superfície complexa que pode ser controlada pelo método de preparação. Neste trabalho aluminas com meso e macroporos foram obtidas usando o método sol-gel acompanhado de separação de fases. Nesta estratégia integrativa a gelatinização e a separação de fases ocorrem de maneira espontânea no sistema contendo um indutor de separação de fases. Diferentes alumina foram produzidas a partir do isopropóxido e cloreto de alumínio e do óxido de polietileno e óxido de polipropileno como indutores de separação de fases. A escolha apropriada da composição de partida permite o controle do tamanho e volume dos poros. Os macroporos são formados como resultado da separação de fases após remoção do indutor de separação de fases, enquanto os mesoporos são formados entre as partículas do xerogel. As diferentes aluminas porosas preparadas e uma alumina comercial foram utilizadas como suporte de catalisadores de cobalto. Os precursores óxidos dos catalisadores obtidos após calcinação são compostos pelas fases Co3O4 e CoAl2O4, esta última em maior quantidade nas aluminas sintetizadas via sol-gel. As aluminas sol-gel possuem maior proporção de Al em sítios octaédricos e grupos hidroxilas superficiais do que a alumina comercial, verificou-se que estas características podem facilitar a migração de íons de Co na rede da alumina levando a maior formação de CoAl2O4. Os catalisadores foram...<br>Abstract: Alumina is an important support for heterogeneous catalysts. The matching of appropriate alumina physical properties and controlled textural properties can improve its performance as support in catalysis applications. Cobalt based catalysts have been reported to have a good ethanol steam reforming (ESR) performance due to their high activity for the cleavage of C-H and C-C bonds. Many studies have been conducted about the effects of alumina properties on the cobalt catalysts properties. Alumina exhibits a rather complex surface chemistry which can be controlled by the preparation procedure. In this work alumina samples with macro and mesoporous structure were obtained using the one-pot sol-gel synthesis accompanied by phase separation. In this integrative strategy both processes, gelation and phase separation, spontaneously occur in system containing the presence of the phase separation inducer. The different aluminas were produced by using as aluminum reactants, aluminum isopropoxide and chloride and polyethylene oxide or polypropylene oxide as phase separation inducer. Appropriate choice of the starting composition allows the control the pore size and volume. Macroporous are formed as a result of phase separation after burning the phase separation inducer, while voids between particles of the xerogel skeletons form a mesoporous structures. The different alumina porous alumina and commercial alumina were used as supports for preparing by wetness impregnation cobalt-based catalyst. The oxidic catalyst precursors obtained after calcination are composed of Co3O4 and CoAl2O4-like phases, the latter being in higher proportions in the sol-gel alumina than in the commercial one. As the sol-gel alumina presents a larger amount of octahedral AlVI sites and surface hydroxyl groups than the commercial alumina, it was assumed that these features can facilitate the migration of Co ions into the alumina network...<br>Doutor
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Weatherspoon, Michael Raymond. "Conformal sol-gel coatings on three-dimensional nanostructured templates." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/28157.
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Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Sandhage, Kenneth; Committee Member: Barefield, Kent; Committee Member: Bunz, Uwe; Committee Member: Carter, Brent; Committee Member: Tannenbaum, Rina.
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Freitas, Jefferson Arlen. "Sintese e caracterização de biossorventes a partir da imobilização da biomassa Sargassum sp em matrizes ceramicas pelo processo sol-gel." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266214.
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Orientador: Elias Basile Tambourgi<br>Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica<br>Made available in DSpace on 2018-08-11T04:08:18Z (GMT). No. of bitstreams: 1
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Previous issue date: 2007<br>Resumo: Este trabalho tratou da pesquisa e desenvolvimento de um adsorvente alternativo, aplicável no tratamento de rejeitos líquidos industriais, contendo baixas concentrações dos metais pesados Cd, Cu e Zn. Ele teve como objetivo geral produzir esferas adsorventes de zeólita 4A - Sargassum sp. com custo de produção competitivo e com elevada capacidade de captura dos metais pesados Cd, Cu e Zn, nas quais o processo de adsorção ocorra com elevada eficiência e com cinética favorável. A produção das esferas envolveu uma abordagem inovadora do Processo Sol - Gel, a qual permitiu produzir sete tipos de esferas, partindo da combinação e imobilização de adsorventes tradicionais pesquisados: biomassa Sargassum sp., caulim, alumina e zeólita. Este processo de imobilização das partículas dos adsorventes tradicionais causa uma obstrução dos poros e canais existentes nestas partículas e, com isto, reduz a capacidade de captura dos metais pesados nas esferas resultantes. Felizmente, a combinação de adsorventes realizada viabilizou a obtenção de esferas adsorventes com elevada capacidade de captura de metais pesados e com cinética favorável. É o caso das esferas de zeólita 4A, com capacidade máxima de captura de Cd+Cu+Zn de 746 µmol/g, com uma velocidade de captura aproximada de 18 µmol/g.h e com uma eficiência de captura de 82% e das esferas de zeólita 4A - 50% em peso de Sargassum sp., com capacidade máxima de captura de Cd+Cu+Zn de 709 µmol/g, com uma velocidade de captura aproximada de 20 µmol/g.h e com uma eficiência de captura de 83%. O comportamento de adsorção destas esferas se ajustou ao modelo de equilíbrio de Freundlich. Elas possuem uma cinética de adsorção compatível com o modelo cinético de pseudo-segunda ordem. Ao tratarem um efluente industrial real, estas esferas apresentam uma eficiência de captura de Cd+Cu+Zn =90% enquanto que numa resina quelante comercial esta eficiência é de 99,5%. Tem-se, pois, esferas adsorventes com elevada eficiência e baixo custo de produção, tornando-as um bom adsorvente para aplicação no tratamento de efluentes líquidos industriais com baixa concentração de Cd, Cu e Zn<br>Abstract: In this work had been made a research and the development of an alternative adsorbent which may be applied in the treatment of industrial liquid effluents containing low concentration of heavy metals, Cd, Cu and Zn. The main objective was to produce 4A type zeolite-Sargassum sp. adsorbents spheres with the following characteristics: competitive fabrication cost; high uptake capacity of the heavy metals, Cd, Cu and Zn; high affinity by the referred heavy metals; and appropriated adsorption kinetic. The marking of the adsorbents spheres had involve the innovative use of the Sol-gel Process. That had permitted to obtain seven types of adsorbents spheres for combination and immobilization of the particles of traditional adsorbents Sargassum sp., kaolin, alumina and 4A type zeolite. This immobilization process causes an obstruction of the pores and the channels present in these particles that reduced the uptake capacity of the produced adsorbents spheres. Fortunately, the combination of traditional adsorbents particles produced adsorbent spheres with high uptake capacity, high uptake efficiency, and appropriate adsorption kinetic. As, two types of adsorbent spheres, 4A type zeolite and 4A type zeolite-50% Sargassum sp. adsorbed 746 µmol/g and 709 µmol/g with an adsorption velocity of 18 µmol/g.h and 20 µmol/g.h, and a uptake efficiency of 82% and 83%, respectively. The adsorption behavior of these adsorbent spheres had been fitting to the Freundlich model. They have an adsorption kinetic compatible with the pseudo-second order model. When it treated an industrial liquid effluent with these adsorbent spheres, they showed a uptake efficiency higher than 90% and while an uptake efficiency of 99,5% is shown for the commercial chelant resin<br>Doutorado<br>Sistemas de Processos Quimicos e Informatica<br>Doutor em Engenharia Química
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Wang, Jing. "Novel Carbon Nanotube Sol-Gel Composite for Sensing Applications." Digital Commons @ East Tennessee State University, 2006. https://dc.etsu.edu/etd/2241.
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Sol-Gel techniques depend on the hydrolysis and condensation reactions of organosilicon precursors in aqueous media and, thus, provide an inclusive environment with bioaffinity. On the other hand, carbon nanotubes (CNTs), which possess unique electric, thermal, mechanical, and chemical properties, including their high surface area:volume ratio, can be further surface-functionalized to address different material or sensing demands.
In this work we describe a new composite material that combines the unique sol-gel network with conductive CNTs. Hydrolysis and subsequent condensation of tetramethyloxysilane (TMOS) in the presence of CNTs result in the formation of a dense, homogeneous material. Properties of this composite material on electrode surfaces are discussed and novel sensing applications are described.
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Walker, Jeremy D. "Exploring the Synthesis and Characterization of Nanoenergetic Materials from Sol-Gel Chemistry." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14573.
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Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed proton scavenging mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide/hydroxide, FeIIIxOyHz, has been confirmed for the weak base propylene oxide (PO), a 1,2 epoxide, as well as for the weak bases tetrahydrofuran (THF), a 1,4 epoxide, and pyridine, a heterocyclic nitrogen-containing compound. THF follows a similar mechanism as PO; the epoxide extracts a proton from the coordination sphere of the hydrated iron complex forming a protonated epoxide which then undergoes irreversible ring-opening after reaction with a nucleophile in solution. Pyridine also extracts a proton from the hydrated metal complex, however, the stable six-membered molecule has low associated ring strain and does not endure ring-opening.
Fe2O3/Al energetic systems were synthesized from the epoxides PO, trimethylene oxide (TMO) and 3,3 dimethyl oxetane (DMO). Surface area analysis of the synthesized matrices shows a direct correlation between the surface area of the iron (III) oxide matrix and the quantified exothermic heat of reaction of the nano-scaled aluminum-containing energetic material due to the magnitude of the interfacial surface area contact between the iron (III) oxide matrix and the aluminum particles. The Fe2O3(PO)/Al systems possess the highest heat of reaction values due to the oxide interfacial surface area available for contact with the aluminum particles. Also, reactions containing nano-scale aluminum react differently than those containing micron-scale aluminum.
RuO2/Al energetic systems behave differently dependent on the atmosphere the sample is heated. Heating the RuO2/Al samples in an inert atmosphere results in the complete reduction of the ruthenium oxide matrix to Ru(0) before reaction with the aluminum particles, resulting in the exothermic formation of RuxAly intermetallics, with the stoichiometry dependent on the initial Ru:Al concentration. However, heating the samples in an oxygen-rich atmosphere results in an exothermic reaction between RuO2 and Al.
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Chaumel, Frederic. "A new synthetic route to sol-gel materials containing nonlinear optical chromophores /." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31207.
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Network formation using chlorotris(diethylamino)silane [ClSi(NEt 2)3], tetrakis(dimethylamino)silane [Si(NMe2) 4], and tetrakis(diethylamino)tin [Sn(NEt2)4], and NLO-active chromophore was investigated to yield inorganic-organic hybrid materials for 2nd-order nonlinear optics. In contrast to hybrids obtained from Si(NEt2)4, those prepared from ClSi(NEt 2)3 and Sn(NEt2)4 were insoluble even in high boiling solvents. Facile hydrolysis of the NLO-active dye was found to occur in these hybrids due to the catalysis of HCl and the high reactivity for ClSi(NEt2)3 and Sn(NEt2)4 respectively. Due to the insolubility of the networks, it was not possible to determine if the dye present in these networks was physically trapped or covalently bound to the inorganic matrix. It was observed that the method used for the hydrolysis of M--NR2 bond played an important role in the stability of the Si--OR bond for hybrids prepared from Si(NMe 2)4 and Sn(NEt2)4.
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Hant, Steven Michael. "Characterization and fabrication of nanoporous materials by template-directed sol-gel methods." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/64302/.
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This research project focussed on developing synthetic strategies to fabricate a variety of nanoporous materials ranging the full range of pore sizes from micro to macro using template assisted sol-gel routes. Both colloidal crystals and surfactant self assemblies were employed as templates. Initial studies focussed on the fabrication of macroporous titano/alumino and tinsilicate materials by dip infiltrating colloidal crystal templates with sol-gel mixtures. The sols were prehydrolysed in order to ensure atomic scale homogeneity of the final material. These materials were subsequently characterised using SEM to observe the macrostructure whilst XRD, EDX, NMR and iR were used to characterise the thermal stability and chemical homogeneity. The work reports materials with metal:silicon atomic ratios for macroporous titanosilicates and aluminosilicates that are far in excess of those previously reported in the literature. Following this research was focused on the production of hierarchically ordered meso/macro silica materials by dip coating a preformed colloidal crystal into a sol-gel solution which contained surfactants. This technique combines principles of colloidal crystal templating and liquid crystal templating and by varying the surfactant it was possible to obtain mesoporous pore walls with both ordered and wormhole pore morphologies. The materials were characterised with both SEM, TEM and Nitrogen sorption and exhibited surface areas in excess of 500 m2 g-1. It was further shown that the mesopore size could be tuned by choosing different surfactants and mesopore sizes ranging from 2-7 nm were produced. Finally, the synthetic procedures developed to produce meso/macro silica were used to produce meso/macro titania and zirconia by extending the method to incorporate different metal alkoxides precursors. These materials were once again characterised by SEM, TEM and nitrogen sorption and it was shown meso/macro titania and zirconia could be easily fabricated using this simple approach. It was also shown that the ordering in these materials was more sensitive to the chosen surfactant with only larger tri-block copolymer surfactants yielding stable mesostructures.
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Huang, Xiaoguang. "Luminescent Lanthanide Hybrid Sol-gel Materials with Potential Applications in Electronic Devices." Palaiseau, Ecole polytechnique, 2015. http://www.theses.fr/2015EPXX0011.
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Wiper, Paul Vincent. "Novel sol-gel materials for advanced glass products : structure, dynamics and stability." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/7993/.
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Flame retardants are composite materials or chemicals used in thermoplastics, thermosets, textiles, coatings and glasses that inhibit or resist the spread of fire. In 2014 the global market for flame retardants is expected to reach $6.10 billion with a drive in research for designing and developing new fire resistant materials. A commercially available product based on a hydrogel/glass composite is an effective fire and heat resistant glazing that is employed in the commercial and domestic sector. The macroscopic effects of these materials have been investigated; however no information exists on the molecular level properties. Therefore, the aim of this research is to fully characterise a series of hydrogels with the ultimate goal of understanding structure-property relationships. The hydrogels discussed herein are made by drying commercially available sodium-silicate solutions onto traditional float glass to create a sandwich glazing. The materials present a unique challenge to characterise at the molecular level because of their amorphous and metastable nature. NMR spectroscopy has been extensively used in this research because it is shown to be an ideal technique for the elucidation of structures and dynamics in disordered systems. The complete “life-cycle” of the product is investigated; firstly, using solid-state NMR, a thorough and detailed analysis of the hydrogels are presented. The thermal stability of the hydrogels are then investigated by means of short and long term ageing effects, which shows that the product crystallises into the layered silicate makatite. The ability to improve the longevity of the product by inhibiting makatite formation follows with a final section dedicated to understanding different composites of the materials.
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Nguyen, Thoi Dang. "Design and operation of nanovalves constructed from supramolecules and sol-gel materials." Diss., Restricted to subscribing institutions, 2006. http://proquest.umi.com/pqdweb?did=1276397761&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Kustra, Joanna. "Elaboration of micro and mesostructured sol-gel materials using polysilsesquioxane molecular precursors." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1081/document.
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Le projet de thèse a pour but de synthétiser de nouveaux matériaux siliciques à microstructure contrôlée en utilisant des procédés de polycondensation à basse température, et de développer de nouvelles approches de microfabrication 3D à haute résolution par excitation bi-photonique d’une formulation sol-gel. La synthèse de matériaux microstructurés est ici centrée sur le procédé sol-gel, impliquant des réactions d’hydrolyse-polycondensation. Les mtériaux les plus étudiés par ces approches en particulier dans le cadre d’un contrôle de la porosité sont préparés à partir de tetraéthoxide de silicium (TEOS)/ Le matériau est structuré généralement par des agent moléculaires structurants (« templates ») tels que les composés tensioactifs. Ces derniers sont en général éliminés, après condensation des silanols, par traitement thermique ou lavage afin de libérer la porosité et générer la structuration. Cette étape d’élimination des agents structurants est souvent problématique, en particulier au niveau industriel, car elle utilise soit des hautes températures, soit des quantités importantes de solvants. Il y a un enjeu important à développer des approches de microstructuration s’affranchissant de ces agents moléculaires structurants, cela représentant le principal objectif de cette thèse.Deux stratégies sont abordées aux cours de ce travail de recherche. La première implique l’utilisation de précurseurs organosilylés donc la structure moléculaire permet une microstructuration du matériau synthétisé. Cette partie explore l’utilisation de précurseurs de la famille des silsesquioxanes et leur transformation vers les matériaux. La deuxième approche propose d’évaluer pour la première fois l’utilisation de l’excitation biphotonique pour contrôler l’étape de condensation sol-gel par modification de pH au point focal d’un laser et ainsi apporter une résolution micrométrique à la structuration du matériau<br>The main goal of this research was the synthesis of new siliceous materials with controlled microstructures, using low-temperature polycondensation process, and develop the new approach towards 3D microfabrication under two-photon excitation of a sol-gel formulation. Synthesis of microstructured materials is based on the sol-gel process, i.e. hydrolytic polycondensation. Most known siliceous materials with controlled microstructure are synthesized from tetraethoxysilane (TEOS). The materials are generally structured by structuring molecular agents ("templates") such as surfactant compounds, which are then removed by heat treatment or washing with appropriate solvents. This stage of removal of structuring agents is often problematic, particularly at the industrial level, because it uses either high temperatures or large amounts of solvents. Therefore, new methods to obtain materials with controlled porosity without the need to use templates are still being developed. Two strategies are discussed during this research work. First one involved the use of organosilicon precursors with a define structure that at molecular level modify the structure of the final materials. The use of well-defined precursors (silsesquioxanes), in appropriate proportions, allows the control of the porosity of the obtained silica materials. The second approach investigated in this work is the local photo-induced structuration of silicon based pre-hydrolyzed precursors under two-photon excitation allowing high 3D resolution
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DeRose, Christopher Todd. "Electro-Optic Polymers: Materials and Devices." Diss., The University of Arizona, 2009. http://hdl.handle.net/10150/195650.
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Electro-optic (EO) polymers are an attractive alternative to inorganic nonlinear materials. EO polymers with a Pockel's coefficient, r33, greater than 320 pm/V have been recently demonstrated. In addition to their high EO activity, EO polymers have the additional benefit that their dielectric constants at optical and millimeter wave frequencies are closely matched which allow for bandwidths which are limited only by the resistive losses of traveling wave electrodes. The amorphous nature of the host polymer makes heterogeneous integration of the materials on any substrate possible. The devices which will have the most immediate impact based on these recent materials developments are EO waveguide modulators. Performance benchmarks of less than 6 dB insertion loss, sub-volt Vpi and greater than 100 GHz bandwidth have been achieved separately however, the challenge of achieving all of these benchmarks in a single device has not yet been met.The aim of this dissertation is to optimize passive materials to achieve efficient in device poling of EO polymers, optimize the chromophore loading of the active polymers and to optimize waveguide modulators for device performance within a particular system, analog RF photonic links. These optimizations were done by defining figures of merit for the materials and modulators. This research strategy has led to significant improvements in poling efficiency as well as modulators with record low insertion losses which maintain a low half-wave voltage; on the order of 1 - 2 Volts. Using this optimization strategy and state of the art EO polymers, devices which meet or surpass the benchmark performance values in all categories are expected in the near future.
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Yang, Xiangxin. "Sol-gel synthesized nanomaterials for environmental applications." Diss., Manhattan, Kan. : Kansas State University, 2008. http://hdl.handle.net/2097/884.
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Clavel, Guylhaine. "Magnetic impurities in nanostructured materials." Doctoral thesis, Universidade de Aveiro, 2009. http://hdl.handle.net/10773/3210.
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Doutoramento em Química<br>Os resultados apresentados aqui foram alcançados no âmbito do programa de doutoramento intitulado “Impurezas Magnéticas em Materiais Nanoestruturados”.
O objectivo do estudo foi a síntese e caracterização de óxido contendo impurezas magnéticas. Durante este trabalho, sínteses de sol-gel não-aquoso têm sido desenvolvidos para a síntese de óxidos dopados com metais de transição (ZnO e ZrO2). A dopagem uniforme é particularmente importante no estudo de semicondutores magnéticos diluídos (DMSs) e o
ponto principal deste estudo foi verificar o estado de oxidação e a estrutura local do dopante e para excluir a existência de uma fase secundária como a
origem do ferromagnetismo. Para alargar o âmbito da investigação e explorar plenamente o conceito de "impurezas magnéticas em materiais
nanoestruturados" estudamos as propriedades de nanopartículas magnéticas dispersas em uma matriz de óxido. As nanopartículas (ferrita de cobalto) foram depositadas como um filme e cobertas com um óxido metálico semicondutor
ou dielétrico (ZnO, TiO2). Estes hetero-sistemas podem ser considerados como a dispersão de impurezas magnéticas em um óxido. As caracterizações exigidas por estes nanomateriais têm sido conduzidas na Universidade de Aveiro e Universidade de Montpellier, devido ao equipamento complementar.<br>The results presented here have been achieved under the PhD program entitled “Magnetic Impurities in Nanostructured Materials”. This study had as purpose the synthesis and characterization of oxidic semiconductor containing magnetic impurities. During this work we have developed non-aqueous sol-gel routes, leading to well controlled oxide nanomaterials, to the synthesis of
transition-metal doped oxides (ZnO and ZrO2). Homogeneous doping is particularly important in the comprehensive study of diluted magnetic
semiconductors (DMSs), and the main point of this study was to ascertain the oxidation state and local structure of the dopant, as well as to exclude the
existence of secondary phase as the origin of ferromagnetism. To enlarge the field of research and fully explore the concept of “magnetic impurities in nanostructured materials” we have studied the magnetic properties of nanoparticles embedded in an oxide matrix. The nanoparticles (cobalt ferrite) were deposited as a film and coated by a semiconducting or dielectric metal oxide (ZnO, TiO2). These hetero-systems can be regarded as dispersion of magnetic impurities in oxides. The characterizations needed by these nanomaterials were performed at the University of Aveiro and University of Montpellier because of complementary available equipments.
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Mehdi, Beata Layla. "FABRICATION OF SOL-GEL FILMS BASED ON ELECTROCHEMICALLY ASSISTED DEPOSITION PROCESSING." Miami University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=miami1367543075.
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Ellis, Michael Martin. "Formation of pure polycrystalline alpha-alumina fibers from an organo-metallic sol-gel." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20010.
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