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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Preparation, characterization and applications of monolithic titania-silica aerogels /

Cao, Shengli. January 2007 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2007. / Includes bibliographical references. Also available in electronic version.

Chemistry in an inorganic-organic hybrid aerogel : chitosan-silica aerogel /

Liu, Xipeng. January 2005 (has links)
Thesis (Ph.D.)--Brown University, 2005. / Vita. Thesis advisor: William M. Risen, Jr. Includes bibliographical references (leaves 35-37, 86-88, 162-165, 210-212). Also available online.

Transparent and Crack-Free Silica Aerogels

Athmuri, Kalyan Ram January 2012 (has links)
The process of making silica aerogels has been studied in detail over the past two decades due to its usage in a wide range of low end applications such as thermal insulators, supercapacitors etc., as well as high end applications like particle physics, space explorations. These applications call for control over the properties of aerogels, such as their transparency, density, porosity, pore size, and integrity. However, despite all the past research, controlling properties of aerogels is still not a fully developed science, a lot more research needs to be done. The literature on silica aerogels does not cover the study of the relation between transparency and cracks in aerogels – which can be a key factor in making aerogels for many applications. Hence, optimization of the transparency and integrity of the aerogels in order to obtain high transparency and low cracks was attempted in this thesis.

Alkali activated aerogels /

Svingala, Forrest R. January 2009 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Caption title. Includes bibliographical references (leaves 68-70).

Characterizaton of Triethoxyfluorosilane and Tetraethoxysilane Based Aerogels

Roepsch, Jodi Ann 12 1900 (has links)
Aerogels are highly porous, low dielectric constant (low k) materials being considered by the semiconductor industry as an interlayer dielectric. Low k materials are needed to overcome capacitance problems that limit device feature sizes. Precursors triethoxyfluorosilane (TEFS) and tetraethoxysilane (TEOS) were used to prepare bulk aerogels. Samples were prepared by sol-gel methods, and then carbon dioxide supercritically-dried. Effects of varying the water to precursor ratio were studied with respect to aerogel properties and microstructure. Methods of analysis for this study include FTIR-ATR, TEM, RBS, EDS, SEM, dielectric constant determination by impedance and surface area by gas adsorption. Si-F bonds were determined to be present in both acid- and base-catalyzed TEFS as well as HF-catalyzed TEOS. Fluorine promotes a fractal network microstructure as opposed to a particle-like microstructure. Surface area and dielectric constant were determined to increase slightly with increases in the water to precursor ratio.

Embedding luminescent nanocrystals in silica sol-gel matrices

Sorensen, Lindsey Michelle. Strouse, Geoffrey F. January 1900 (has links)
Thesis (M.S.)--Florida State University, 2006. / Advisor: Geoffrey F. Strouse, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed June 8, 2006). Document formatted into pages; contains x, 50 pages. Includes bibliographical references.

Function-led Design of Aerogels: Self-assembly of Alloyed PdNi Hollow Nanospheres for Efficient Electrocatalysis

Cai, Bin, Wen, Dan, Liu, Wei, Herrmann, Anne-Kristin, Benad, Albrecht, Eychmüller, Alexander 26 August 2016 (has links) (PDF)
Amelioration of the building blocks is a plausible approach to graft aerogels with distinguished properties while preserving the aerogel superiority. However, the incorporation of designated properties into metallic aerogels, especially catalytically beneficial morphologies and transition metal doping, still remains a challenge. Here, we report on the first case of an aerogel electrocatalyst composed entirely of alloyed PdNi hollow nanospheres (HNSs) with controllable chemical composition and shell thickness. The synergy of the transition metal doping, combined with the hollow building blocks and the three dimensional network structure make the PdNi HNS aerogels promising electrocatalysts towards ethanol oxidation, among which the Pd83Ni17 HNS aerogel shows a 5.6-fold enhanced mass activity compared to commercial Pd/C. This work expands the exploitation approach of electrocatalytic properties of aerogels into morphology and composition control of its building blocks.

Functionalisation of clay aerogel composites for applications in construction

Abo Madyan, Omar January 2018 (has links)
Clay aerogels are relatively a new class of materials with number of merits suitable for many applications in various industrial sectors. With the current mandate to utilise environmentally friendly materials to produce functional materials, clay aerogels provide an attractive potential green solution to overcome thermal issues in construction. However for it to be effectively used as an insulation material, research work is required to address several critical issues and setbacks: the first of these is poor mechanical properties highlighted in the literature as its main weakness; the second is there extremely high hydrophilic and hygroscopic nature identified as the main research gap, which not only can cause a significant increase in thermal conductivity but also can disintegrate the aerogels. This thesis investigates and develops novel methodologies to overcome the associated setbacks through comprehensive characterisation and better understanding of mechanisms of formulation, architecture, behaviour and corresponding performance of clay aerogel constituents and composites: (I) The anisotropic structure of the aerogel was thoroughly investigated and its influence on properties was established; (II) By adjusting and tuning the mixing temperatures, the compressive modulus was enhanced by more than 7 folds; (III) Ultrasonic technologies were used to prepare organoclay- polyvinyl alcohol aerogel composites with 40% less moisture absorption in addition to lower thermal conductivity; (IV) Implementing organosilanes and isocyanates to prepare clay-PVA aerogels resulted in an effective method to reduce the moisture absorption by more than 40% with a 6 fold increase in compressive modulus; (VI) soluble water repellent was incorporated to prepare hydrophobic aerogel composites with contact angles of 140°; and (VII) Organosilanes and isocyanates are combined with a water repellent to generate highly functional clay aerogel composites. Overall this thesis paves the way for the industrialisation of functional clay-aerogel insulation materials for construction and other sectors.

Preparació i caracterització d'aerogels nanocomposats amb metalls. Aplicacions en catàlisi

Martínez Crespiera, Sandra 26 October 2006 (has links)
En la present tesi doctoral es descriu la preparació de diferents tipus d'aerogels (aerogels de sílice, híbrids orgànic-inorgànics, orgànics i de carbó) nanocomposats amb ferro, níquel, pal·ladi o europi.Per tal d'introduir aquests metalls a l'interior de l'aerogel s'han utilitzat dos tècniques diferents: la cogelificació, en la que el metall s'introdueix a l'hora que té lloc la síntesi del gel mitjançant el procés sol-gel, i la impregnació, en la que el metall s'introdueix després d'haver-se format el gel. A continuació i per tal d'obtenir els aerogels a partir dels corresponents gels dopats amb metall s'ha realitzat dos tipus d'assecats supercrítics diferents: l'assecat supercrític a elevada temperatura (en el que l'etanol es porta a les condicions supercrítiques) i l'assecat supercrític a baixa temperatura (en el que el CO2 es porta a les condicions supercrítiques).Aquests aerogels preparats s'han caracteritzat a partir de les següents tècniques: la Microscopia de Transmissió Electrònica (TEM) , la Difracció de Raigs X en pols (p-XRD), les Mesures d'Adsorció-Desorció de Nitrogen (BET) i les Anàlisis Químiques. A partir de la caracterització d'aquests aerogels s'ha procedit al seu assaig com a catalitzadors recuperables i reutilitzables en les reaccions d'addició de Michael i les reaccions de Mizoroki-Heck.Durant la realització de la present tesi també s'han preparat i caracteritzat aerogels fluorats amb els següents objectius: per una banda la obtenció d'un material superhidrofòbic i per l'altre banda la obtenció d'aerogels per evaporació del dissolvent del gel a temperatura ambient i sense un assecat supercrític. La preparació d'aquests aerogels es realitza mitjançant la fluoració dels gels de sílice amb el 1H,1H,2H,2H-perfluorooctildimetilclorosilà. Així doncs per una banda, l'assecat d'aquests aerogels a temperatura ambient dóna lloc a uns materials que, tot i que presenten una àrea superficial inferior a la dels aerogels, són porosos i mantenen l'estructura monolítica prèvia dels gels. Per altra banda els aerogels assecats en condicions supercrítiques mostren un caràcter superhidrofòbic. / In the present thesis the preparation of different kind of aerogels (silica aerogels, hybrid organic-inorganic aerogels, organic and carbon aerogels) doped with iron, nickel, palladium or europium is described.In order to introduce these metals inside the aerogels two different techniques have been applied: the cogelation process in which the metal is introduced at the same time that the gel is formed and the impregnation process in which the metal is introduced after the gel is formed. The next step is the supercritical drying of the gels to obtain the aerogels. Two different kind of dryings have been done: at high temperatures with ethanol and at low temperatures with CO2.These aerogels have been characterize with the following techniques: Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (p-XRD), BET and Elemental Analysis.These aerogels have been assaied as recoverable and reusable catalysts in Michael addition reactions and in Mizoroki-Heck reactions.Florinated aerogels have also been prepared through fluorination of silica gels with 1H, 1H, 2H, 2H-perfluorooctyldimethylchlorosilane. These aerogels have shown to be superhydrophobics. The drying of these aerogels at room temperature and under ambient pressure generates a material which is porous and it maintains its monolithity.

Carbon cryogel based nanomaterials for efficient energy storage /

Feaver, Aaron. January 2007 (has links)
Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 196-206).

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