Dissertations / Theses: 'Sol-gel'

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Yang, Quanzu. "Composite sol-gel ceramics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/NQ46453.pdf.

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Zheng, Lei. "Cobaltferrite-bariumtitanate sol-gel biferroics." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3648.

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Thesis (M.S.) -- University of Maryland, College Park, 2006.
Thesis research directed by: Dept. of Material Science and Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Gardener, Martin. "Studies in sol-gel chemistry." Thesis, Nottingham Trent University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341276.

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Borislav, Simendić. "Niskotemperaturno procesiranje sol-gel mulita." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 2003. https://www.cris.uns.ac.rs/record.jsf?recordId=71471&source=NDLTD&language=en.

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Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).Mehanizam nastanka mulita zavisi od načina doziranja polaznih oblika reaktanata kao što su alumina i silika. Dobijanje mulita sol-gel postupkom je u velikoj meri poboljšano u odnosu na klasično procesiranje zbog mogućnosti homogenog mešanja AI₂O₃ i SiO₂ komponenti i kontrole dodataka. Sol-gel metod omogućuje pripremu vrlo homogenih i reaktivnih gelova koji mogu da sinteruju na nižim temperaturama pri čemu se može postići vrlo fina mikrostruktura. U ovom radu koji se odnosio na procesiranje mulita sol-gel postupkom, hipoteza je bila da se na samom početku procesiranja aluminijumovi joni iz alkoholnog rastvora Al-soli uključuju u polimernu gel strukturu koju formira silika. Svrha ovog rada, je proučavanje uticaja procesnih promenjivih, dodatka fluornog jona i “seedinga” na temperaturu nastanka sol-gel mulita pri čemu se očekuje što je moguće niža tempertura nastanka mulita (niža od 980⁰C). Polimerni sol je dobijen u prvom slučaju mešanjem TEOS-a i aluminijum nitrata nanohidrata koji je prethodno rastvoren u etil alkoholu. U drugom slučaju, u polimerni sol je dodavan fluorni jon u koncentraciji 2 do 5 % mas. u odnosu na očekivani prinos mulita i u trećem slučaju je dodavana različita količina mulitnih klica (2-4 % mas.). Eksperimantalno je potvrđeno da procesne promenljive; pH, temperatura geliranja i R odnos imaju, veliki uticaj na brzinu geliranja i na nastanak mulita. U slučaju dodavanja fluornog jona, potvrdena je hipoteza da fluorni jona na različite načine utiče na mehanizam nastanka mulita, pri čemu u prvom slučaju prisustvo fluornog jona obezbeduje mesta u oblastima razdvajanja granica faza nakon geliranja koja utiču na proces nukleacije. Ova mesta slično procesu kristalizacije stakla, omogućuju lakšu nukleaciju mulita prilikom njegove transformacije iz gela. Mesta na granici razdvanja faza postaju mesta na kojima se uspostavlja proces heterogene nukleacije što je jedan od mogućih načina za snižavanje temperature nastanka mulita. Pored ovoga, dodavanje fluornog jona je doprinelo promeni mulitnih gel struktura, pri čemu je promena brzine hidrolize silike imala za posledicu promenu sadržaja vezane vode u toku geliranja što se takođe značajno odražavalo na temperaturu nastanka mulita. Eksperimentalni rezultati termički obradenih gelova su pokazali, da dodavanje lluornog jona u polimerni mulitni sol stvara uslove za snižavanje temperature obrazovanja mulita sve do 890⁰C. U ovom radu je takođe pokazano da mulitne čestice, kao nukleanti pri “seeding" procesiranju, doprinose nastanku mulitnog gela koji nakon termičke obrade na 1000⁰C pokazuje veoma finu mikrostrukturu.
Abstract was processed by technology for Optical character recognition (OCR).The mechanism of mullite formation depends upon the method of combining the alumina and silica containing reactants. Mullite can be obtained through the sol-gel process and can be greatly improved by the control of some reaction conditions particulaiiy by homogeneous mixing of Al2O3 and SiO2, and controlling of the additions. Sol-gel method allow preparation of very homogenous and reactive gels which can be sintering at low temperature and consequently submicronic microstructure can be reached. In this study of the mullite formation by sol-gel method, the hypothesis was that aluminium ions from alcoholic solulion of its salts incorporate to polymeric silica gel structure. The aim of this work was the investigation of the effect processing variables, fluorine addition and “seeding”on the temperature of sol-gel mullite formation and to obtain as lower temperature of mullite formation as possible (smaller than 980°C). Polymeric sols, were prepared by the mixing of TEOS and aluminum nitrate nanohydrate dissolved in absolute ethyl alcohol and by adding fluorine ions in the second case from 2 wt.% to 5 wt.% and by different content of mullite seeded (2- 4 wt. %). Experimentally is determined that the processing variables as pH, gelling temperature and R ratio have high influence on the gelling rate and mullite formation. The hypothesis in the case of fluorine addition was that addition of fluorine ions could have different effects on the mechanism of mullite formation; the first it makes the sites at boundary of phase separation regions after gelling which influence at the process of the nucleation. These sites will act as a place for easy mullite nucleation, similar to process of the glass crystallization. The boundaries of the phase separation are the sites for heterogeneous nucleation which is one of the condition for lowering the temperature of mullite formation. Besides, fluorine addition could change the mullite gel structure (by changing the rate of hydrolyses of silica and it could change the content of bonded water during gelling), which should be very important for the temperature of mullite formation, too. The experimental results of heat treated gels showed that the addition of fluorine ion does decrease the temperature of mullite formation (in respect to classical sol-gel mullite processing) up to 8900C. As a nucleant in this study the mullite powder by “seeding” process contribute to muillite gel formation that after heat treatment up to 10000C showed very fine microstructure.

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Pohl, Annika. "Sol−Gel Synthesis of CMR Manganites." Doctoral thesis, Uppsala University, Department of Materials Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3970.

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The development of more advanced materials forms the basis of technological progress. One group of fascinating compounds with many potential applications in spintronic devices are the mixed-valence perovskite manganites. These have attracted considerable interest during the last decade through their very large magnetoresistance near the Curie Temperature. Although the properties of a material determinie any application, the development of reliable and flexible synthesis methods is crucial, as is the understanding of these methods. Knowledge of how different materials are formed is also of general importance in tailoring new materials. The aim of this project has therefore been not only to develop a new synthesis route, but also to understand the mechanisms involved.

This thesis describes the synthesis and characterization of a novel manganese alkoxide and its use in sol–gel processing of magnetoresistive perovskite manganites. In searching for a soluble manganese alkoxide for sol–gel processing, we found that the methoxy-ethoxide, [Mn₁₉O₁₂(moe)₁₄(moeH)₁₀]·moeH, has a high solubility in appropriate organic solvents. Being 1.65 nm across, it is one of the largest alkoxides reported; it is also of interest because of its (for oxo-alkoxides) rare planar structure. After mixing with La, Nd, Ca, Sr, and Ba methoxy-ethoxides, [Mn₁₉O₁₂(moe)₁₄(moeH)₁₀]·moeH was used in the first purely alkoxide based sol–gel processing of perovskites manganites. The phase evolution on heating xerogel powders to 1000°C was studied, and thin films were prepared by spin-coating.

It was found that the easily oxidised Mn-alkoxide facilitates the formation of high oxygen-excess modifications of the perovskites. The reactive precursor system yields fully hydrolysed gels almost without organic residues, but the gel absorbs CO₂ from the air, leading to carbonate formation. The carbonate decomposition is the limiting step in oxide formation. Transport measurements of La_0.67Ca_0.33MnO₃ films on LaAlO₃ substrate show that all-alkoxide sol–gel derived films can compete with PLD films in terms of quality of epitaxy and transport. The somewhat different behaviour of the sol–gel derived films compared to PLD films is attributed to differences in morphology and oxygen stoichiometry.

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Barreau, Stephanie. "Biosensing with sol-gel-immobilised proteins." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/27275.

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Low temperature-processed, porous sol-gel glasses represent a new class of materials for the immobilisation of biomolecules. If used to entrap biological recognition elements, these transparent and chemically inert glasses offer a new approach in the development of optical biosensors.

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Noureddine, Achraf. "Approches Click en Chimie Sol-Gel." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2014. http://www.theses.fr/2014ENCM0005/document.

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Nous visons dans ce travail de thèse à développer une méthodologie de fonctionnalisation par chimie click des silices hybrides synthétisées par voie sol-gel. La réaction click de cycloaddition azoture-alcyne catalysée au cuivre (CuAAC) offre une tolérance exceptionnelle pour les fonctions organiques en plus de conversions très élevées. Dans cette optique, nous avons mis en œuvre en premier lieu des matériaux clickables à base d'organosilice pure (organosilice à mésoporosité périodique (PMO) et silsesquioxanes pontés (BS)) qui ont permis une conversion quasi-quantitative de greffage par CuAAC. Nous avons ensuite utilisé cette particularité pour contrôler les propriétés de surface des BS en modifiant leur caractère hydrophile/lipophile. Dans le second axe de travail, nous nous sommes intéressés à l'apport de la chimie click pour la préparation de nanoparticules mésoporeuses de silice multifonctionnelles, dites mécanisées, pour des systèmes à délivrance contrôlée de principes actifs
The present work aims to develop a trustful methodology of functionalization for hybrid silica materials made by the sol-gel process using the copper-catalyzed alkyne-azide cycloaddition (CuAAC)Click reaction. This transformation can be highly useful in materials science thanks to its high conversions and the excellent functional group tolerance. In this prospect, we have synthesized fully clickable bridged silisesquioxanes and periodic mesoporous organosilica that show high extents of click grafting. CuAAC was then used for tailoring the surface of bridged silsesquioxane and fine-tuning the hydrophilic/lipophilic balance. Finally, the click reaction was used as an efficient way to obtain multiply functionalized mesoporous silica nanoparticles in order to make nanomachines for controlled delivery of cargo molecules

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Stani´c, Vesha. "Sol-gel processing of metal sulfides." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq21641.pdf.

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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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Bellatone, Maria. "Sol-gel derived antimicrobial bioactive glass." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394943.

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Pethybridge, Guy David. "Sol-gel processing of dielectric ceramics." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318872.

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Mogili, Sravya. "Sol-Gel Synthesis of Aluminosilicate Glasses." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1584733.

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The main goal of this research project is to synthesize aluminosilicate glass materials that are doped with praseodymium. To be useful for optical studies, these glass materials must be optically transparent, strong enough to be handled and polished, and free of cracks. An advantage of the sol-gel process is that we have control over the amount of doping. However, a disadvantage of the sol-gel process is that cracking often occurs during the drying step.

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Blyth, David John. "Optical biosensing using sol-gel technology." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338063.

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Meegan, Jonathan E. "Sol gel synthesis of organised matter." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417746.

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Lima, Patricia Tavares de. "Cordierita : sintese por processamento sol-gel." [s.n.], 1998. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249760.

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Orientador: Celso Aparecido Bertran
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-07-23T13:55:18Z (GMT). No. of bitstreams: 1 Lima_PatriciaTavaresde_M.pdf: 2924918 bytes, checksum: 7a7d3e5d1691d52cb5aa9a78d165f5de (MD5) Previous issue date: 1998
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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.
Chemistry and Chemical Biology

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Karg, Matthias. "Fluorolytische Sol-Gel-Synthese von Magnesiumfluorid." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17292.

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Die vorliegende Arbeit befasst sich mit mechanistischen Untersuchungen der fluorolytischen Sol-Gel-Synthese von nano-Magnesiumfluorid, sowie verschiedenen Abwandlungen der bekannten Synthese zur gezielten Veränderung der Eigenschaften der erhaltenen Materialien. Es werden die drei im folgenden beschriebenen Themenbereiche behandelt: Der Verlauf der Fluorolyse von Magnesiummethoxid mit methanolischer HFLösung wird mit der 19F-NMR-Spektroskopie über sechs Monate untersucht. Es wird gezeigt, dass MgF2-Nanopartikel, Agglomerate von gestörten MgF2-Partikeln und nicht umgesetzte, adsorbierte HF-Spezies in den Solen nachweisbar sind. Erstmalig werden MAS-NMR-Experimente an Solen beschrieben. Zusätzlich wird die schrittweise Fluorolyse von MgCl2 mittels NMR-Spektroskopie und XRD untersucht. Es werden drei verschiedene Synthesewege vorgestellt, mit denen eine Veränderung von Partikel- oder Kristallitgrößen erreicht wird. Eine sequentielle Synthese ermöglicht die Vergrößerung der Agglomerate im Sol. Das Erhitzen eines Sols zum Sieden unter Rückflusskühlung führt zu einem geringfügigen Anwachsen der Kristallitgröße. Durch Solvothermal-Synthesen wird eine signifikante Vergrößerung der Kristallite erzielt. Der Einfluss verschiedener Reaktionsparameter wird untersucht. Der Einfluss von MgF2 auf die Kristallisation von amorphem TiO2 wird untersucht. Es wird gezeigt, dass die Sol-Gel-Synthese von TiO2 in Gegenwart eines MgF2-Sols (min. 5 mol%) zur Kristallisation von Rutil-TiO2 bei vergleichsweise niedrigen Temperaturen führt. Verschiedene alternative Synthesen werden vorgestellt, durch die bei vergleichbaren Bedingungen nur Anatas-TiO2 erhalten werden kann. Ein möglicher Mechanismus der Strukturinduktion wird vorgeschlagen.
The present Ph.D. thesis deals with mechanistic investigations of the fluorolytic sol-gel synthesis of nano magnesium fluoride. Furthermore, variations of the well known synthesis are introduced. The aim of these variations is to tailor the properties of the synthesized materials. The thesis covers three main chapters briefly introduced below: The course of the fluorolysis of magnesium methoxide with methanolic HF-solution will be monitored for six months using 19F NMR spectroscopy. The existence of MgF2 nanoparticles and agglomerates of disturbed MgF2 particles will be proven. It is demonstrated that hydrogen fluoride does not react immediately after the addition of HF-solution. For the first time MAS-NMR experiments of sols will be conducted. Furthermore, stepwise fluorolysis of magnesium chloride will be followed by NMR spectroscopy and X-ray diffraction. In this case no intermediates will be detected. Three different synthetic approaches capable of tailoring the crystallite and particle sizes will be presented. Using a sequential synthesis leads to increased size of the agglomerates in the sols. It will be demonstrated that heating and refluxing of a sol increases the crystallite size slightly. Solvothermal synthesis will be the last method leading to significant increase in crystallite sizes. Several synthetic parameters will be varied to identify their influence on the received crystallites. The influence of nano MgF2 on the crystallisation of amorphous TiO2 is investigated. It will be shown, that the sol-gel synthesis of TiO2 in the presence of a MgF2 sol leads to the crystallisation of the rutile polymorph of TiO2. The temperature treatment for that is comparatively low and just 5 mol% MgF2 are necessary. Furthermore, a different alternative synthesis will be introduced, that gives the anatase polymorph at the same conditions. Eventually a possible mechanism for the structural induction is proposed.

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Lukešová, Magdalena. "Sol-gel proces s reverzními micelami." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2011. http://www.nusl.cz/ntk/nusl-216770.

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Práce popisuje přípravu tenkých transparentních vrstev oxidu titaničitého metodou sol-gel procesu s reverzními micelami, které jsou jedinečným uskupením zajišťujícím uniformní velikost připravených částic. Neionogenní tenzid byl použit jako templát. Pomocí materiálového tisku, tedy specializovanou formou inkoustového tisku, byly připraveny tenké filmy oxidu titaničitého nanesením 1–4 vrstev. Po kalcinaci byly připravené vrstvy oxidu titaničitého charakterizované šířkou zakázaného pásu. Struktura vrstev byla popsána optickou mikroskopií a SEM. Fotokatalytická aktivita byla ověřena oxidační reakcí 2,6-dichlorindofenolu a rozkladem kyseliny stearové, která byla přímo natištěna na vrstvy oxidu titaničitého. Fotoindukovaná změna hydrofility byla studována pomocí měření kontaktního úhlu smáčení vody. Fotokatalytická účinnost připravených filmů rostla s počtem vrstev oxidu titaničitého.

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Gigant, Karine. "Raman-Spektroskopie hybridpolymerer Sol-Gel-Materialien vom Sol bis zur Schicht /." Doctoral thesis, [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=980144906.

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Almeida, Camargo Nelson Heriberto. "Elaboration et caractérisation de céramiques d'alumine sol-gel pure et de nanocomposites alumine sol-gel/carbure de silicium." Lyon, INSA, 1995. http://www.theses.fr/1995ISAL0051.

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Une céramique d'alumine pure a été élaborée par procédé sol-gel en utilisant un précurseur organo-minéral. La filiation Sol --> Gel--> Xérogel -->Alumine de transition (calcination à 900°C) - Alumine alpha (calcination à T1> l000°C) -->Céramique (pressage sous charge à T2 = 1550°C) a fait l'objet d'un analyse physico-chimique et microstructurale exhaustive. L'optimisation de la température a permis d'obtenir une céramique présentant une contrainte de rupture en flexion particulièrement performante (environ 700 MPa). Puis une poudre nanométrique de SiC (d = 20-30 nm) a été incorporée (5% Vol. ) au sol avant gélification, incorporation conduisant à une stabilisation thermique de l'alumine de transition. Ce phénomène a été expliqué sur la base d'une limitation des processus diffusionnels associés à la germination-croissance de l'alumine alpha, nécessitant ainsi une températures T1 sensiblement plus élevée pour former le corindon. Tenant compte de ces observations, des échantillons de céramique nano-composite Alumine/SiC ont été préparés par pressage à chaud à différentes température T2 de 155°C à 175°C. Les caractéristiques mécaniques obtenues restent toujours inférieures à celle de la matrice d'alumine pure et la fracture est transgranulaire, conséquence de l'établissement de contraintes internes élevées au cours du refroidissement du matériau. Ces résultats ont été expliqués par l'analyses de la micro- et de la nano-structure des matériaux en utilisant les techniques de microscopie électronique. Les propriétés assez moyennes obtenues, qui résultent en particulier de la mauvaise dispersion du renfort SiC dans la matrice, ont pu être sensiblement améliorées par une opération d'attrition du xérogel composite associée à un recuit qui limite les contraintes. Mais pour obtenir des caractéristiques performantes, de nombreux autres paramètres doivent être pris en compte. Une analyse de ces paramètres est présentée
A pure alumina ceramic matrix has been made by sol-gel route, using an organo-mineral precursor. The "Sol--> Gel--> Xerogel--> Transition alumina--> Alpha Alumina (calcination at Tl> 1000°C) -->Alumina ceramic (hot-pressing at T2 >Tl)" filiation was subjected to an exhauxtive physico-chemical and microstructural analysis. The optimization of the Tl temperature has allowed to obtain a ceramic body with particularly high flexural strength (about 700 MPa). Then, a nanometric SiC powder was dispersed into the sol before gellation, processing that leads to the thermal stabilization of the transition alumina. This phenomenon was explained on the basis o a limitation of diffusionnal processes associated with the nucleation growth of alpha alumina grains, what needs'to increase the T1 temperature of formation of corundum. Taking this observation into account, nano-composite Alumina/SiC bodies have been elaborated at different T2 temperatures from 1550°C to 1750°C. But mechanical characteristics of the samples obtained are always lower than those of the pure sol-gel alumina ceramic and the fracture is transgranular in type, a consequence of internal stresses that appear during cooling the samples. These results have been explained on the basis of an exhaustive analysis of both the nano- and the microstructure, using electron microscopy. The middle-sized strengths obtained, that also result from the bad dispersion of the SiC reinforcement in the matrix, have been sensitively improved by bali milling the xerogel and annealing the hot-pressed bodies to limit the internal stresses. But the obtention of high strength bodies must take into account the role of many other parameters that are discussed

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Thakor, Vikalp Amar Peng Zhonghua. "Syntheses and sol-gel polymerizations of organotriethoxysilanes." Diss., UMK access, 2005.

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Thesis (M.S.)--Dept. of Chemistry. University of Missouri--Kansas City, 2005.
"A thesis in chemistry." Typescript. Advisor: Zhonghua Peng. Vita. Title from "catalog record" of the print edition Description based on contents viewed June 27, 2006. Includes bibliographical references (leaves 79-85). Online version of the print edition.

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Kapusuz, Derya. "Sol-gel Synthesis Of Dna Encapsulated Silica." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610627/index.pdf.

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Sol-gel processing routes for encapsulation of double stranded DNA in solid porous silica hosts have been established. The encapsulation was carried out in two steps: hydrolysis of a silica-forming alkoxide-based sol was followed by condensation/gelation to a solid form upon addition of a buffer solution containing DNA molecules. The effects of gelation chemistry and DNA amount on chemical and microstructural properties of resultant silica matrices and on DNA encapsulation efficiency were investigated. The analytical characterization was performed by UV-vis spectroscopy, 29Si nuclear magnetic resonance spectroscopy and by nitrogen adsorption studies. It was demonstrated that DNA incorporation had a pH-dependent catalytic effect on gelation kinetics and promoted silica network completion. In addition, the scale of porosity and the average pore size of the resultant silica increased with gelation pH and also with DNA-buffer solution in the starting sol-gel formulation. The chemistry-derived pore size variation controls the DNA encapsulation efficiency in the silica matrices and the DNA holding capacity strongly depends on the scale of the porosity attained. The selective adsorption of ethidium bromide- a DNA-intercalative reagent molecule- on DNA-silica gels confirmed that the DNA molecules remained entrapped within the silica host in their native state without any deterioration. Besides pure silica, amine-functionalized hybrid silica hosts were also formed by sol-gel. The hybrid gels were found not to be suitable for DNA encapsulation, as these matrices dissolve in aqueous environment due to incomplete silica network formation. The DNA-doped silica hosts may provide promising matrices for development of biosensors, bioreactors and bioassay platforms.

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Rodgers, Lisa Elizabeth Biotechnology &amp Biomolecular Sciences Faculty of Science UNSW. "The molecular characterisation of sol-gel biocatalysts." Awarded by:University of New South Wales. School of Biotechnology and Biomolecular Sciences, 2006. http://handle.unsw.edu.au/1959.4/26809.

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Sol-gel matrices may be used to immobilise enzymes, facilitating retention of the catalyst while allowing a flow of substrates and products through the matrix. Candida antarctica lipase B (CALB), a commonly used industrial enzyme, has been shown to have a prolonged catalytic life and enhanced activity when encapsulated in these sol-gel materials. However, the molecular basis for this effect had yet to be elucidated. This study investigated the effect of encapsulating CALB in sol-gel matrices by comparison of CALB in solution with its encapsulated form. Use of complementary techniques revealed the presence of complex interactions between the enzyme and the evolving sol-gel material. 29Si Nuclear Magnetic Resonance (NMR) measurements demonstrated that CALB influenced sol-gel structure by altering silica speciation. Inclusion of CALB also altered the mesoporosity of the matrices as determined using nitrogen sorption and electron microscopy. Correlation of activity assays with 29Si speciation changes indicated that the catalytic activity of the enzyme in solution was directly involved in sol-gel hydrolysis and condensation reactions. Increased specific activity of CALB in the sol-gel aqueous precursor solution resulted in measurable changes in the gel structure of matrices containing 3.1mg of CALB/ml of gel. Small angle neutron scattering (SANS) was used to examine the structure of CALB in solution. The influence of the sol-gel reactants glycerol, sodium fluoride and isopropanol upon the radius of gyration of CALB in solution was determined. SANS was also employed in an investigation of encapsulated CALB molecules which utilised contrast matching of the sol-gel matrix. However, contrast variation studies found that the match point for the silica matrix, both with and without enzyme present, was lower than predicted (~35% vol% D2O). Consequently, the contrast match point of the protein was close to that of the encapsulating material. Scattering from the encapsulated protein at this point was therefore minimal; it is clear that the contrast match point of the protein should be moved through in vivo deuteration in future experiments of this type. These investigations advance the understanding of interactions between the matrix and the encapsulated enzyme in sol-gel biomaterials.

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Leclerc, Brian. "Process optimization for sol-gel PZT films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ37962.pdf.

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25

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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26

Li, Xiaochun. "Structural studies of sol-gel derived glasses." Thesis, Brunel University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293198.

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Laurie, Joyce. "Freeze casting : a modified sol-gel process." Thesis, University of Bath, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260248.

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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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Chevers, John Michael. "Fluorescence studies of sol-gel glass formation." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248307.

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Weng, Luqian. "Sol-gel processing of tellurite thin films." Thesis, University of Lincoln, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312891.

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Garcia-Miquel, J. L. "Solid-state electrochromic films by sol-gel." Thesis, Cranfield University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409619.

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34

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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35

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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Sugrue, Maria. "Sol-gel routes to transparent conductive coatings." Thesis, Kingston University, 2000. http://eprints.kingston.ac.uk/20667/.

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A novel sol-gel process has been developed for producing transparent conductive tin dioxide films and for their application to polymer substrates. Initially, tin oxide was produced by hydrolysis of tin tetrachloride using amended versions of methods found in the literature. The tin oxide produced from the procedure did not adhere well to glass and was not transparent. The procedure was also very time consuming. Preliminary experiments using tin bis (acetylacetonate) dichloride as a precursor were very promising and all efforts were soon concentrated on that route. After a lot of experimentation optimising the method, it was found that colloids capable of producing conductive transparent tin oxide coatings were obtained approximately 10 days after beginning the procedure. Indium and antimony dopants were added to the tin oxide at the sol-gel stage in order to investigate their effect on the DC conductivities of the tin oxide coatings. Bulk conductivities in the ranges 1 to 100 Sm[sup]-1 and 13 to 800 Sm[sup]-1 were obtained for p- and n-type doped annealed tin oxide coatings on glass substrates respectively. The percentage transparencies of the coatings remained high for unannealed coatings (~80%) but decreased to ~ 40% after annealing. Polymer pre-treatments were carried out on the poly (methyl methacrylate), polycarbonate and poly (ethylene terephthalate) substrates. The contact angles and surface energies of the substrates were studied to investigate the effects of the surface pre-treatment techniques. Treatment of the poly (methyl methacrylate) and poly (ethylene terephthalate) substrates consisted of hydrolysis by aqueous sodium hydroxide. A combination of UV/ozone oxidation was used for the polycarbonate substrates. The tin oxide coatings were applied to the polymer substrates by spin-coating, solvent casting and spray coating. From optical microscopy studies, it was shown that the spin-coated films were the most uniform and least cracked. To further increase the adhesion of the coatings on the polymeric substrates, a systematic study was made of the effects of coupling agents, both on the substrate surfaces and in the sol-gel solutions themselves. Short pulses of heating were given to the coatings in an infrared furnace. The annealing did not increase the bulk conductivities greatly but the coatings retained a very high transparency (greater than 90%). To investigate the effect of infrared annealing on tin oxide powder, it was shown from X-ray diffraction that the crystallinity of the tin oxide increased significantly as a result of annealing in the infrared furnace.

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37

Moreira, Paulo Jorge Brandão. "Óptica integrada em tecnologia sol-gel híbrido." Doctoral thesis, Porto : edição do autor, 2005. http://hdl.handle.net/10216/64287.

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38

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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39

Pouxviel, Jean-Claude. "Mecanisme de croissance et polymerisation sol-gel." Paris 6, 1987. http://www.theses.fr/1987PA066587.

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Etude de la polymerisation sol gel d'alcoolate((obu)::(2) al-o-si(oet)::(3)). L'analyse des spectres de rmn du silicium, relayee par des simulations numeriques mettent en evidence les effets de concentration des reactifs(eau, precurseur, alcool, acide) sur les cinetiques d'hydrolyse-condensation du tetraethoxysilane

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40

Amiel, Catherine. "Etude expérimentale de la transition sol-gel." Paris 6, 1986. http://www.theses.fr/1986PA066323.

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41

Marzini, Michael. "Automatisierung und Optimierung des Sol-Gel-Prozesses." [S.l. : s.n.], 2006.

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42

Pouxviel, Jean-Claude. "Mécanisme de croissance et polymérisation sol-gel." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37609036j.

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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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44

Almeida, Rusiene Monteiro de. "Preparação do TiO2 sulfato via sol-gel." Florianópolis, SC, 2003. http://repositorio.ufsc.br/xmlui/handle/123456789/86603.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Química
Made available in DSpace on 2012-10-21T08:39:40Z (GMT). No. of bitstreams: 0
São descritas nesta dissertação as influências causadas por diferentes maneiras no preparo do catalisador TiO2 sulfatado nas suas propriedades físico-químicas e caracterização através de técnicas físico-químicas destes catalisadores. O TiO2 sulfatado foi preparado baseando-se no método sol-gel, porém com algumas alterações. A caracterização foi feita por análise termogravimétrica, espectroscopia de absorção no infravermelho, espectroscopia Raman, espectroscopia no infravermelho de piridina adsorvida para determinação da relação sítios ácidos de Brönsted/sítios ácido de Lewis, determinação da área superficial específica, diâmetro médio dos poros e atividade catalítica na reação de isomerização do n-hexano. Através das análises termogravimétricas, determinou-se o teor de sulfato e as temperaturas de perda de massa do sulfato das amostras. Nos espectros no infravermelho das amostras de TiO2/SO4 verificou-se que o sulfato está coordenado ao titânio na forma quelato. Nos espectros Raman observou-se que as amostras estão na forma anatase. Comparando-se os métodos de preparação das amostras, verificou-se que a relação H2SO4/H2O, utilizado e a ordem de adição dos dois influi nas propriedades do TiO2/SO4, inclusive na atividade catalítica. Verificou-se que as amostras que apresentaram maior diâmetro médio dos poros e maior relação de sítios ácidos de Brönsted/sítios ácidos de Lewis foram as que tiveram maior atividade catalítica. Foram feitos testes catalíticos de conversão do n-hexano a 100°C e 200°C. A 100°C foi observado que a seletividade para a isomerização e estabilidade catalítica são maiores do que a 200°C, porém, a 100°C a conversão é menor do que a 200°C.

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45

Moreira, Paulo Jorge Brandão. "Óptica integrada em tecnologia sol-gel híbrido." Tese, Porto : edição do autor, 2005. http://catalogo.up.pt/F?func=find-b&local_base=FCB01&find_code=SYS&request=000093714.

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46

Jämting, Åsa. "Mechanical properties of thin sol-gel films." Thesis, Queensland University of Technology, 1999. https://eprints.qut.edu.au/36085/6/A%CC%8Asa%20J%C3%A4mting_Digitised%20Thesis.pdf.

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This thesis presents a study of the mechanical properties of thin films. The main aim was to determine the properties of sol-gel derived coatings. These films are used in a range of different applications and are known to be quite porous. Very little work has been carried out in this area and in order to study the mechanical properties of sol-gel films, some of the work was carried out on magnetron sputtered metal coatings in order to validate the techniques developed in this work. The main part of the work has concentrated on the development of various bending techniques to study the elastic modulus of the thin films, including both a small scale three-point bending, as well as a novel bi-axial bending technique based on a disk resting on three supporting balls. The bending techniques involve a load being applied to the sample being tested and the bending response to this force being recorded. These experiments were carried out using an ultra micro indentation system with very sensitive force and depth recording capabilities. By analysing the result of these forces and deflections using existing theories of elasticity, the elastic modulus may be determined. In addition to the bi-axial bending study, a finite element analysis of the stress distribution in a disk during bending was carried out. The results from the bi-axial bending tests of the magnetron sputtered films was confirmed by ultra micro indentation tests, giving information of the hardness and elastic modulus of the films. It was found that while the three point bending method gave acceptable results for uncoated steel substrates, it was very susceptible to slight deformations of the substrate. Improvements were made by more careful preparation of the substrates in order to avoid deformation. However the technique still failed to give reasonable results for coated specimens. In contrast, biaxial bending gave very reliable results even for very thin films and this technique was also found to be useful for determination of the properties of sol-gel coatings. In addition, an ultra micro indentation study of the hardness and elastic modulus of sol-gel films was conducted. This study included conventionally fired films as well as films ion implanted in a range of doses. The indentation tests showed that for implantation of H⁺ ions at doses exceeding 3x10¹⁶ ions/cm², the mechanical properties closely resembled those of films that were conventionally fired to 450°C.

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47

Sibottier, Emilie. "Génération électro-assistée de films à base de silice : fonctionnalisation, mésostructuration et applications analytiques." Thesis, Nancy 1, 2007. http://www.theses.fr/2007NAN10101/document.

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L’étude menée concerne divers aspects d’une nouvelle voie de synthèse sol-gel : la génération électro-assistée de films à base de silice fonctionnalisée et/ou mésostructurée, ainsi que leurs applications en électrochimie analytique. Des films à base de silice fonctionnalisée par des groupements amine ou thiol ont été déposés sur électrode d’or par catalyse électrochimiquement assistée de la polycondensation. La formation d’une monocouche auto-assemblée partielle de mercaptopropyltriméthoxysilane permet une très bonne adhésion du film silicaté sur la surface d’or. Le processus d’électro-dépôt est caractérisé par deux étapes successives de vitesse différente. A une étape de dépôt lent et régulier succède une croissance bien plus rapide du film. L’utilisation des électrodes modifiées a été envisagée en tant que capteur de Cu2+. En introduisant un tensioactif dans le sol de synthèse, il est possible d’électrogénérer des films à base de silice mésoporeuse de structure hexagonale avec les pores orientés perpendiculairement par rapport au substrat (difficile à obtenir par d’autres méthodes). Il semblerait que l’électrochimie permette à la fois un contrôle de la structure du tensioactif à la surface de l’électrode et la croissance simultanée du film sol-gel. Cette méthode d’électrogénération permet aussi d’obtenir des films fins homogènes sur des surfaces non planes ou présentant des hétérogénéités de conductivité. Enfin, une approche préliminaire a été proposée visant à appliquer le processus d’électrogénération, couplé à la technique de microscopie électrochimique à balayage, pour déposer localement des films à base de silice sous forme de plots de taille micrométrique sur or
The study deals with various aspects of a novel method of sol-gel synthesis : the electro-assisted generation of functionalized and/or mesostructured silica thin films, and their applications in analytical electrochemistry. Sol-gel-derived silica films functionnalized with amine or thiol groups have been electrogenerated on gold electrodes. The formation of a partial self-assembled monolayer of mercaptopropyltrimethoxysilane (MPTMS) on gold led to a silica film adhering well to the electrode surface owing to the MPTMS acting as a « molecular glue ». The whole process was characterized by two successive distinct rates, starting by a slow deposition stage leading to thin deposits, which was followed by a much faster film growing in the form of macroporous coatings. The use of these modified electrodes was considered as a voltammetric sensor for copper(II). By adding a surfactant in the synthesis medium, it’s possible to electrogenerate mesostructured silica films with hexagonal structure with pore channels oriented perpendiculary to the substrate (which is difficult to get by other methods). The electrochemically-induced-self-assembly of surfactant-templated silica thin films can be applied to various conducting supports. The broad interest of the novel method was demonstrated by its ability to produce homogeneous deposits of silica on non-planar surfaces or heterogeneous substrates, what is difficult by the traditional techniques of film deposition. Finally, a preliminary approach has been proposed in order to apply the electrodeposition process coupled with a scanning electrochemical microscope in order to get localized sol-gel deposits at the micrometric size level on gold

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48

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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49

Huang, Yu Hong. "Sol-gel PbTiO₃ thin films for pyroelectric applications /." Lausanne, 1995. http://library.epfl.ch/theses/?nr=1343.

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Völger, Karl Wolfgang. "Keramische Materialien über einen nichtoxidischen Sol-Gel-Prozess /." Aachen : Shaker, 2002. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=010295269&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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Dissertations / Theses on the topic 'Sol-gel'

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