Dissertations / Theses on the topic 'Sol-gel Synthesi'
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1
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 La0.67Ca0.33MnO3 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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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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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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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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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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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 orThe 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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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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Bheemala, Veera Manesh. "Sol-Gel Synthesis of Lanthanide-Doped Aluminosilicate Glasses." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1601351.
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Doping Praseodymium into Al-Si glass has potential applications in permanent holographic data storage and other optical devices. For this we are using the sol-gel method to produce glass monoliths at relatively low temperatures. The silicon precursor is tetraethylorthosilicate (TEOS) and aluminum tri-sec butoxide (ATSB) is the aluminum precursor. TEOS is hydrolyzed in ethanol with HCl as a catalyst. ATSB is then added, as well as praseodymium chloride in water. To prevent cracking we use dimethyl formamide (DMF) as a drying control chemical additive (DCCA). The solution is poured into a polymethylpentene cylinder and maintained at 40°C and the temperature is raised to 150°C to dry and shrink the sample. Samples prepared by this method are amorphous, as indicated by X-ray diffraction. The final aim of this research is to produce optically clear, fracture less monoliths by varying aging, shape and drying conditions.
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Yakovlev, A. V., and A. V. Vinogradov. "Inkjetready Sol-gel Synthesis of Nanocrystalline Titania Colloids." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42582.
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Materials based on titanium dioxide produced as a highly photoactive catalysts, attracted the attention of many researchers because of the environmentally friendly destruction of substantially all organic contaminants. In this study, the inkjet titania films with hierarchical structures were prepared by a combined sol–gel and inkjet method. The X-ray powder diffraction (XRD) result indicated that the synthesized titania
nanoproducts were of pure anatase phase. The data of low-temperature nitrogen adsorption-desorption and TEM (SEM) images demonstrate that the formed nanocolloids had a narrow particle size distribution with average diameter of 15 nm and were composed of nanocrystals with about 7 nm in diameter. The Brunauer–Emmett–Teller (BET) results showed that the titania inkjet layers have high surface area
(110-127 m2/g) and lots of mesopores.
10
Kaur, Rajvinder. "Non-hydrolytic Sol-gel Synthesis of Tin Sulfides." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1404243055.
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Wuttke, Stefan. "Sol-Gel-Synthese und Charakterisierung nanoskopischer Magnesiumfluorid-Phasen." Berlin mbv, Mensch-und-Buch-Verl, 2009. http://d-nb.info/995893306/04.
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Schiavon, Giovanni. "Sol-gel derived nanocomposites synthesis, spectroscopy, atomic force microscopy /." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962035424.
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Čižauskaitė, Sigutė. "Sol-gel synthesis of perovskite structure aluminates and cobaltates." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20091202_112230-17664.
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In the present thesis the reported results let us to conclude that the developed aqueous sol–gel procedure could be successfully used for the low-temperature synthesis of monophasic perovskite gadolinium aluminate ceramics. It was also demonstrated that the selection of raw materials for the sol–gel processing should be done with care. Monophasic perovskite structure gadolinium aluminate GdAlO3 has been synthesized by sol gel synthesis method at 1000 oC, using gadolinium oxide as gadolinium raw material and 1.2 ethanediol, natural tartaric acid, citric acid or mixture of citric acid and ethanolamine as complexing agent. According to the XRD results, the Gd2O3 instead of Gd(NO3)36H2O preferably should be used as starting material for the preparation of GdAlO3. Monophasic perovskite structure strontium substituted gadolinium aluminate Gd0.90Sr0.10AlO3– was synthesized by the same sol gel synthesis method at 1000 oC, using gadolinium oxide as gadolinium raw material, strontium nitrate as strontium ion source and EDTA as complexing agent. It was proved that better gadolinium ion source is gadolinium oxide than gadolinium nitate hexahydrate, better complexing agent – EDTA than natural tartaric acid in the synthesis of GdAlO3 and strontium substituted Gd1–xSrxAlO3– (x = 0.10, 0.25, 0.50, 0.75) samples. According to the XRD results, increasing amount of strontium reduces amount of peaks of perovskite structure gadolinium aluminate. Besides, 800 ºC temperature is too low for the... [to full text]Šiame darbe vienfazis perovskito struktūros gadolinio aliuminatas GdAlO3 zolių-gelių metodu buvo gautas 1000 oC temperatūroje, gadolinio jonų šaltiniu naudojant Gd2O3, kompleksus sudarančiu reagentu – 1,2 etandiolį, natūralią vyno rūgštį, citrinų rūgštį arba citrinų rūgšties ir etanolamino mišinį. Sintetinant GdAlO3, gautų tyrimų rezultatai parodė, kaip yra svarbu zolių gelių procese pasirinkti tinkamas pradines medžiagas bei kompleksus su metalais sudarančius reagentus: gadolinio jonų šaltiniu naudojant Gd2O3 buvo gauti geresni rezultatai nei naudojant Gd(NO3)3•6H2O, vienfazis GdAlO3 gali būti sėkmingai susintetintas kompleksus sudarančiu reagentu naudojant tiek natūralią vyno rūgštį, tiek 1,2 etandiolį, tiek citrinų rūgštį, tiek citrinų rūgšties ir etanolamino mišinį. Nustatyta, kad sintetinant stronciu pakeistus gadolinio aliuminatus Gd1–xSrxAlO3– (x = 0,10, 0,25, 0,50, 0,75), tinkamesnis gadolinio jonų šaltinis yra gadolinio oksidas nei gadolinio nitratas heksahidratas, kompleksus sudarantis reagentas – EDTA nei natūrali vyno rūgštis. Vienfazis perovskito struktūros stronciu pakeistas gadolinio aliuminatas Gd0,90Sr0,10AlO3– buvo susintetintas zolių-gelių metodu 1000 oC temperatūroje, gadolinio jonų šaltiniu naudojant Gd2O3, stroncio jonų šaltiniu – Sr(NO3)2, kompleksus sudarančiu reagentu – EDTA. Be to, 800 ºC iškaitinimo temperatūra yra per maža šiems junginiams sintetinti. Pirmą kartą pasiūlytas vandeninis zolių gelių metodas lantano ir gadolinio kobaltatams... [toliau žr. visą tekstą]
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Dubnikova, Natalija. "Sol-gel synthesis and characterization of lanthanide aluminium garnets." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20111227_092034-78155.
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The development and application of advanced materials is a very important task of today's information society. Garnet crystal structure compounds because of their specific physical and chemical properties are widely used in information technology, manufacturing of solid-state lasers and optical equipments, medical equipments and many other areas. Therefore, these materials because of their unique properties and characteristics are of high interest so far.
For the first time Ce-Al-O, Pr-Al-O, Nd-Al-O, Tb-Al-O, Dy-Al-O, Ho-Al-O, Er-Al-O, Tm-Al-O, Yb-Al-O, Lu-Al-O, Y(Nd)-Al-O and Y(Sm)-Al-O acetate-nitrate-glycolate gels have been synthesized using environmentally friendly, economical and simple aqueous sol-gel method. They were used as starting materials for the synthesis of appropriate lanthanide aluminium garnets. The results of X-ray difraction analysis have indicated that single-phase terbium aluminium garnet (Tb3Al5O12), dysprosium aluminium garnet (Dy3Al5O12), holmium aluminium garnet (Ho3Al5O12), erbium aluminium garnet (Er3Al5O12), thulium aluminium garnet (Tm3Al5O12), ytterbium aluminium garnet (Yb3Al5O12) and lutetium aluminium garnet (Lu3Al5O12) have been synthesized by annealing Tb-Al-O, Dy-Al-O, Ho-Al-O, Er-Al-O, Tm-Al-O, Yb-Al-O and Lu-Al-O precursor gels for 10 hours at 1000 °C, respectively. For the first time these garnet structure compounds were synthesized using sol-gel method. Moreover, these lanthanide aluminium garnets were synthesized at relatively low... [to full text]Pažangių medžiagų bei technologijų kūrimas ir taikymas - tai labai svarbus šiandieninės informacinės visuomenės uždavinys. Granato kristalinės struktūros medžiagos, pasižymėdamos ypatingomis fizikinėmis bei cheminėmis savybėmis, yra plačiai naudojamos informacinių technologijų, kietafazių lazerių, optikos įrenginių gamybose, medicinos įrangose, bei daugelyje kitų sričių. Todėl jos dėl savo unikalių savybių ir plačiai tebetyrinėjamos iki šiol. Šiame darbe pirmą kartą buvo susintetinti Ce-Al-O, Pr-Al-O, Nd-Al-O, Tb-Al-O, Dy-Al-O, Ho-Al-O, Er-Al-O, Tm-Al-O, Yb-Al-O, Lu-Al-O, Y(Nd)-Al-O ir Y(Sm)-Al-O acetatiniai-nitratiniai-glikoliatiniai geliai zolių-gelių metodu vandeniniuose tirpaluose. Jie buvo panaudoti pradinėmis medžiagomis atitinkamų lantanoidų aliuminio granatų sintezei. Vienfaziai terbio aliuminio granatas (Tb3Al5O12), disprozio aliuminio granatas (Dy3Al5O12), holmio aliuminio granatas (Ho3Al5O12), erbio aliuminio granatas (Er3Al5O12), tulio aliuminio granatas (Tm3Al5O12), iterbio aliuminio granatas (Yb3Al5O12) ir liutecio aliuminio granatas (Lu3Al5O12) buvo gauti, terbio jonų šaltiniu naudojant terbio oksidą, disprozio – disprozio oksidą, holmio – holmio oksidą, erbio – erbio oksidą, tulio – tulio oksidą, iterbio – iterbio oksidą, lutecio – liutecio oksidą, kompleksus sudarančiu reagentu 1,2-etandiolį. Tyrimų rezultatai parodė, kad šių lantanoidų aliuminio granatai gauti santykinai žemoje temperatūroje (1000°C). Zolių-gelių metodu sintetinant cerio aliuminio granatą... [toliau žr. visą tekstą]
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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.Includes bibliographical references (p. 26-27).
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.
by Andrew William Sparks.
S.B.
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Rane, Neelesh Janardan. "Sol-Gel Synthesis and Characterization of Mesoporous Ceria Membranes." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1046381173.
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Eltanany, Gehan. "Sol-gel synthesis and properties of nanoscopic aluminum fluoride." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15679.
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Aluminiumfluorid (HS-AlF3), das mit Hilfe des Sol-Gel-Verfahrens unter nicht-wässrigen Bedingungen hergestellt wird, weist eine extrem große Oberfläche und eine hohe Lewis-Acidität auf, die mit den stärksten bekannten Lewis-Säuren wie SbF5 und ACF vergleichbar ist. Diese ungewöhnlichen Eigenschaften werden im Ergebnis einer neuen Sol-Gel-Synthese erhalten, die die Fluorolyse eines Aluminium-Alkoxids durch wasserfreien Fluorwasserstoff in organischen Lösungsmitteln zur Grundlage hat. Das zunächst in einer amorphen, katalytisch inaktiven Vorstufe mit großer Oberfläche gebildete Gel wird nach anschließender Trocknung mit gasförmigen Fluorierungsmitteln nachfluoriert, wobei die aktive Form des HS-AlF3 erhalten wird. Im Rahmen der vorliegenden Arbeit wurden alle Schritte dieses Syntheseweges untersucht und die Ergebnisse einschließlich einer detaillierten Analyse der erhaltenen Materialien diskutiert. Des Weiteren wurde HS-AlF3 durch eine Imprägnierungs-Methode auf das Trägermaterial Al2O3 aufgetragen, wobei verschiedene Beladungen mit HS-AlF3 getestet wurden. Die Eigenschaften des HS-AlF3/Al2O3 als Lewis-Säure-Katalysator wurden mittels der Dismutierung von CHClF2 und der Isomerisierung von CBrF2CBrFCF3 bestimmt. Die Herstellung von AlFyOx mit Hilfe des Sol-Gel-Verfahrens ist ebenfalls beschrieben, wobei das Produkt amorph ist und eine große Oberfläche von bis zu 240 m2/g aufweist.Aluminum fluoride (HS-AlF3) prepared via sol-gel synthesis route under non-aqueous conditions exhibits high surface area and an extremely strong Lewis acidity, comparable with some of the strongest known Lewis acids such as SbF5 and ACF. The basis of its unusual properties is the sol-gel fluorination of aluminum alkoxide with anhydrous HF in organic solvents yielding first an amorphous catalytically inactive precursor with high surface area, which can be dried and eventually post-fluorinated to get HS-AlF3. In this thesis, all steps of the synthesis route were thoroughly investigated. The results of these investigations together with detailed analysis of the obtained materials are reported and discussed. HS-AlF3 supported on Al2O3 with different HS-AlF3 loadings was prepared by wet impregnation method. The properties of the HS-AlF3/Al2O3 samples as Lewis acid catalyst were evaluated for CHClF2 dismutation and CBrF2CBrFCF3 isomerization. The preparation of AlFyOx via sol-gel method is also reported. AlFyOx prepared is amorphous and have high surface are up to 240 m2/g.
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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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Foroutan, F. "Sol-gel synthesis of phosphate-based glasses for biomedical applications." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1470766/.
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This thesis concerns the development of a new and facile sol-gel synthesis route for production of phosphate-based glasses for biomedical applications including; tissue engineering, imaging contrast agents and drug delivery systems. The structure of the prepared samples was probed by XRD, 31P MAS-NMR, EDX and FTIR spectroscopy that confirmed successful synthesis and production of phosphate based glasses via the sol-gel method. In this study, for the first time, quaternary phosphate-based sol-gel derived glasses in the P2O5-CaO-Na2O-TiO2 system with a high TiO2 content of up to 30 mol% were synthesised. While incorporating a high percentage of titanium into the phosphate network is non-trivial via traditional melt quench methods. Investigation of quaternary glasses with the general formula of (P2O5)55-(CaO)25-(Na2O)(20-x)-(TiO2)x, where X = 0, 5, 10 or 15 revealed, substituting titanium in place of sodium significantly improves the stability and prolongs the degradation of these glasses, which opens up a number of potential biomedical applications. Cell studies on titanium-stabilised glasses suggested glasses containing 5 or 10 mol% TiO2 have optimal potential for bone tissue engineering applications. Electrospraying was used to prepare (P2O5)55-(CaO)30- (Na2O)15 glass nanospheres with a diameter size range of 200-500 nm. These glass nano spheres were used as a transient contrast agent for ultrasound imaging to label mesenchymal stem cells and it was determined in vitro and in vivo that these nanospheres had a detection limit of 5 and 9 μg.mL-1, respectively. Cell counts down to 4000 could be measured with ultrasound imaging with no cytotoxicity at doses required for imaging. Glass nanospheres were also used as a carrier for drug delivery applications with a linear release of tetracycline hydrochloride molecules within the first 4 hours of the study period. Importantly, ion release studies confirmed these glass nanospheres biodegrade into an aqueous medium with degradation products that can be easily metabolised in the body. To the knowledge of the author, this is the first report of sol-gel synthesis and electrospraying to prepare glass nanospheres at low processing temperature and the first use of such a system for both diagnostic and therapeutic purposes.
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Bogdanoviciene, I., A. Kareiva, M. Misevicius, L. Bauermeistere, A. Viksna, K. A. Gross, and A. Beganskiene. "Sol-Gel Synthesis and Characterization of Cerium Substituted Calcium Hydroxyapatite." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34936.
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In this study, an aqueous sol-gel chemistry route based on phosphoric acid as the phosphorus precursor,
calcium acetate monohydrate and cerium (III) nitrate hexahydrate as source of calcium and cerium
ions, respectively, have been used to prepare cerium-substituted calcium hydroxyapatite (CHAp) powders.
The tartaric acid was used as complexing agent in the sol-gel processing. The final products were obtained
by calcination of the dry precursor gels for 5 h at 1000 °C. The phase transformations, composition, and
structural changes in the polycrystalline samples were studied by infrared spectroscopy (IR), X-ray powder
diffraction analysis (XRD), scanning electron microscopy (SEM), UV-visible reflection spectroscopy and
luminescence measurements. It was demonstrated, however, that the high substitution of calcium by cerium
does not proceed in the CHAp. The reflectance spectra of Ce substituted CHAp show nearly 100% reflection
in the wavelength range of 450-800 nm. The luminescent properties of these samples were also investigated.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34936
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Kabre, Tushar Shriram. "Co3O4 Thin Films: Sol-Gel Synthesis, Electrocatalytic Properties & Photoelectrochemistry." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316552072.
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Liao, Haidong. "Sol-gel Synthesis and Photocatalytic Characterization of Immobilized TiO2 Films." Licentiate thesis, Stockholm : Skolan för kemivetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10683.
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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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BROUDIC, JEAN-CHARLES. "Syntheses et caracterisation de cordierites obtenues par voie sol-gel." Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13116.
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On a utilise differents precurseurs organometalliques et sels permettant d'abaisser les temperatures de cristallisation et de densification des ceramiques, les rendant compatibles avec des encres au cuivre. On a etudie les phenomenes favorisant ou inhibant la cristallisation de la phase -cordierite a basse temperature en mettant en evidence des heterogeneites de quelques nanometres existant des le stade xerogel. On a etabli des correlations entre les phases cristallographiques obtenues et les microstructures des ceramiques, ainsi qu'entre les phases cristallographiques et les proprietes physico-chimiques (constante dielectrique, coefficient d'expansion thermique)
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Belon, Cindy. "Synthèse de revêtements hybrides organique-inorganique par photopolymérisation sol-gel." Thesis, Mulhouse, 2010. http://www.theses.fr/2010MULH3908.
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L'objectif de cette thèse a été de démontrer la pertinence du procédé sol-gel photoinduit pour la synthèse de films nanocomposites originaux à partir de précurseurs hybrides mono- et bis-silylés. Bien que mentionné dans la littérature, ce procédé basé sur une catalyse via des super-acides de Bronsted créés par la photolyse d'un photogénérateur d'acides reste à ce jour très marginal. Selon la nature des précurseurs mis en oeuvre, la photopolymérisation sol-gel a parfois été combinée à une photopolymérisation organique pour mener à l'obtention en une seule étape de réseaux hybrides organique-inorganique. Au cours de ces travaux, l'accent a tout d'abord été mis sur la caractérisation structurale des matériaux synthétisés. Pour cela, des mesures par spectroscopie infrarouge à transformée de Fourier, résonance magnétique nucléaire du 29Si et du 13C en phase solide et diffraction des rayons X ont été réalisées. Ces études ont permis de révéler les nombreux avantages liés à la voie photochimique tels que la forte réactivité, le caractère vivant de la réaction, l'absence d'eau ou de solvant et l'obtention de matériaux organisés à l'échelle locale. Enfin, l'originalité de cette étude a également résidé dans la mise en œuvre de nombreuses techniques de caractérisation thermo-mécanique des films : analyse mécanique dynamique, calorimétrie différentielle à balayage, nanoindentation, tribologie et tests de résistance à la rayure. L'influence de la nature chimique de la fonctionnalité organique du précurseur employé a ainsi pu être soulignée et des corrélations entre microstructure et propriétés finales des matériaux photopolymérisés ont été établiesThe present work questioned the interest of sol-gel photopolymerization as a novel route to synthesize nanocomposite films from hybrid mono- and bis-silylated precursors. The potentialities of this process that is based on a catalysis promoted by photogenerated Bronsted superacids have been poorly investigated so far. Depending on the precursor nature, the sol-gel photopolymerization was possibly combined with an organic photopolymerization in a view to generate the dual crosslinking of the organic and inorganic networks in a single step. A first aspect of this work concemed the structural properties of the hybrid films: Fourier transformed IR spectroscopy, 29Si and 13C solid state Nuclear Magnetic Resonance spectroscopy and X-rays analysis were thus implemented. These experiments highlighted the numerous advantages of the photoinduced sol-gel process: its high reactivity, its living character, the absence of water or solvent and the local organization in the resulting films. Finally, the thermo-mechanical properties of the UV cured materials were assessed by using a wide range of characterization techniques: dynamic mechanical analysis, differentia!scanning calorimetry, nanoindentation, tribological and scratch tests. The effect of the organic moiety functionality of the precursors was thus evidenced and relationships between microstructure and properties ofthe hybrid films were established
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Chowdhury, Anirban. "Synthesis and Characterisation of Ferroelectric Thin Films via Sol-Gel Routes." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505084.
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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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O'Callaghan, Samantha Ann. "Sol-gel synthesis of nanosized sodium potassium niobate-based piezoelectric ceramics." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707999.
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Varcoe, John Robert. "Synthesis and characterisation of novel inorganic polymer electrolytes." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302667.
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Casanova, Martínez Ana. "Synthetic strategies for the preparation of nanoporous carbons with improved electrical conductivity." Thesis, Orléans, 2020. http://www.theses.fr/2020ORLE3093.
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A côté d’une grande variété de concurrents tels que les métaux (nobles ou non) ou les oxydes métalliques, les carbones nanoporeux apparaissent comme des matériaux clés dans de nombreuses applications électrochimiques. Ils permettent une grande diversité d’architectures de pores contrôlées combinées à des nombreuses propriétés, en particulier, la stabilité chimique et mécanique, la biocompatibilité, une chimie de surface riche et, surtout, une conductivité électrique relativement élevée.Bien que certains carbones (comme le graphite ou le graphène) présentent des propriétés électroniques proches de celles des électrodes métalliques, cette caractéristique dépend fortement de la disposition spatiale des atomes de carbone. En effet, la plupart des carbones nanoporeux sont des matériaux avec un faible degré d'ordre structurel et, par conséquent, avec une conductivité limitée. En vue d’améliorer cette conductivité, des efforts sont donc nécessaires pour préparer des carbones nanoporeux avec un degré élevé d’organisation structurale sans compromettre la structure poreuse.Pour cela, plusieurs stratégies ont été explorées: (i) le dopage des hétéroatomes; (ii) le revêtement avec une phase conductrice; (iii) la synthèse d'architectures 3D de type graphène nanoporeux, et (iv) l'incorporation d'un additif conducteur dans les encres appliquées pour la préparation des électrodes. Cette dernière option est pratique courante dans la plupart des applications électrochimiques, le noir de carbone étant l'additif conducteur le plus utilisé.Ce doctorat a consisté à explorer diverses approches synthétiques pour obtenir à la fois, des carbones nanoporeux avec des réseaux très poreux et une conductivité accrue en incorporant diverses nanostructures de carbone comme additifs conducteurs. Dans une première approche, l'additif a été incorporé pendant la synthèse des carbones nanoporeux eux-mêmes. Dans une seconde approche, des structures 3D de type graphène nanoporeux ont été obtenues par des approches hydrothermiques.Les carbones nanoporeux ont été obtenus modifiant la polycondensation des mélanges de résorcinol et de formaldéhyde décrite dans la littérature. Cette approche permet d'obtenir des matériaux très poreux avec des propriétés accordables, ce qui représente un avantage par rapport aux méthodes conventionnelles qui génèrent des matériaux avec une distribution de taille de pores plus large. Afin d’améliorer leur conductivité électrique, diverses nanostructures de carbone ont été utilisées comme additifs conducteurs: noir de carbone, graphite, graphène et dérivés d'oxyde de graphène.L'effet de divers paramètres tels que la nature, la quantité, le caractère hydrophobe et la composition de l'additif a été évalué. L'étude a révélé le rôle important de la nature de l'additif, non seulement sur la conductivité du composite gel de carbone/additif, mais aussi sur le développement de la porosité. Les additifs carbonés de nature hydrophobe favorisent le développement d'architectures de pores multimodales avec une prédominance des grands mésopores. Les additifs hydrophiles rendent les matériaux moins poreux. Concernant la conductivité, les composites ont montré des valeurs améliorées avec des seuils de percolation d'environ 8 wt.% pour le noir de carbone.Dans la seconde approche, différents carbones nanostructurés ont été soumis à un traitement hydrothermal pour améliorer leur porosité. Tout d'abord, la synthèse du graphène par décomposition par plasma de l'éthanol a été optimisée avec de bons taux de production et de qualité pour des débits de 2 à 4 g/h. L'oxyde de graphène a également été synthétisé par une méthode Hummers modifiée.Dans l'ensemble, des carbones nanoporeux avec une porosité élevée et une conductivité améliorée ont été obtenus par l’incorporation de faibles quantités de noir de carbone, graphite et graphène pendant la synthèse. Ces matériaux présentent un intérêt en tant qu'électrodes dans les applications électrochimiquesNanoporous carbons are key materials in many electrochemical applications over a wide variety of competitors (such as noble metals, non-noble metals or metal oxides) due to the diversity of materials with controlled pore architectures combined with adequate properties; particularly, chemical and mechanical stability, biocompatibility, rich surface chemistry and, most importantly, relatively high electronic conductivity.Although some carbons (e.g., graphite, graphene) present electronic properties close to those of metallic electrodes, this feature depends strongly on the spatial arrangement of the carbon atoms. Indeed, most nanoporous carbons are non-polycrystalline materials with a low degree of structural order and, as a consequence, with limited conductivity. Thus, efforts are yet needed to prepare nanoporous carbons with high and well defined pore architectures combining high electrical conductivity without compromising the porous structure.To increase the conductivity of nanoporous carbon electrodes without compromising the porosity, several strategies have been explored such as: (i) heteroatoms’ doping; (ii) coating with a conductive phase; (iii) synthesizing 3D nanoporous graphene-like architectures, and (iv) incorporating a conductive additive in the formulation of carbon electrodes inks. The latter is the common practice for the manufacturing of the electrodes in electrochemical applications, being carbon black the most popular conductive additive.The approach in this PhD consisted in exploring various synthetic approaches to obtain nanoporous carbons with high porous networks and enhanced conductivity upon incorporating various carbon nanostructures as conductive additives. In a first approach, the additive was incorporated during the synthesis of the nanoporous carbon material itself, rather than as percolator in the inks typically used in the preparation of electrodes (e.g., carbon material, binder and percolator). In a second approach, 3D nanoporous graphene-like architectures were obtained by hydrothermal approaches.The synthesis of the nanoporous carbons was carried out by a modification of the polycondensation of resorcinol and formaldehyde mixtures well reported in the literature for the preparation of carbon gels. This approach allows obtaining highly porous materials with tuneable properties compared to conventional activation methods that usually render materials with broad pore size distributions. To overcome the drawback of their low electrical conductivity, various carbon nanostructures were used as conductive additives: carbon black, graphite, graphene and graphene oxide derivatives.The effect of various parameters such as the type, amount, hydrophobic/hydrophilic character and composition of the additive was explored. The study revealed the important role of the nature of the additive not only on the conductivity of the carbon gel/additive composite, but also on the development of the porosity during the synthesis. Carbon additives of hydrophobic nature act as a porogen, favouring the development of multimodal pore architectures, with predominance of large mesopores. Hydrophilic additives rendered materials with lower porosity. Regarding conductivity, the composites showed enhanced values, with percolation thresholds of ca. 8 wt.% for carbon black.In the second approach, various nanostructured carbons were subjected to a hydrothermal treatment. First, graphene synthesis by plasma decomposition of ethanol was optimized, with good production rates and quality for flows of 2-4 g/h. Graphene oxide was also synthesized by a modified Hummers method. The hydrothermal treatment rendered materials with improved porosity.Overall, highly nanoporous carbons with controlled mesopore architectures and enhanced conductivity were obtained. Such materials are of interest as electrodes in electrochemical applications (e.g, energy storage, supercapacitors, electrochemical sensors)
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Didier, Benoît. "Synthèse d'un matériau hybride polyimide/silice par voie sol-gel : Etude structure/propriétés." Chambéry, 2005. http://www.theses.fr/2005CHAMS022.
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Ce travail a consisté à synthétiser un matériau hybride polyimide/silice par voie sol-gel. La préparation de ces matériaux pose un problème de compatibilité entre les phases organique et inorganique. La silice et le polymère n'ont pas d'affinité particulière et ont tendance a créer une forte ségrégation de phase. Pour éviter ce phénomène plusieurs solutions ont été reportées dans la littérature, comme l'utilisation d'agent de couplage. Dans notre cas, nous avons réduit ce phénomène en créant des liens covalents entre le. . . Celles-ci vont réagir avec la silice lors du procédé sol-gel. Nous avons fait varier différents paramètres tels que le taux de greffage entre les phases, ou le catalyseur utilisé lors du procédé sol-gel. La suite du travail a consisté à étudier les différentes morphologies obtenues en fonction de l'évolution des paramètres de synthèse. Pour cela, nous avons utilisé différentes techniques tel que l'analyse thermogravimétrique, la détermination de densité, la spectroscopie infrarouge, ou la microscopie. Ce travail nous a permis de déterminer les taux de silice, la taille des particules au sein de la matrice et leur état de dispersion. Nous avons également étudié la microstructure de nos matériaux par spectroscopie mécanique dynamique. En effet, les différentes morphologies conduisent a des effets sur le renforcement de la phase silice sur les propriétés mécaniques de nos matériaux. Nous avons ainsi pu identifier des phénomènes de percolation pour certains de nos matériaux. Dans un dernier temps, nous avons étudié les propriétés de perméation gazeuse de nos matériaux, afin de tirer les grandes évolutions des coefficients de perméabilité et de sélectivité en fonction du taux de silice et du taux de greffage entre la phase organique et inorganique. Nous avons ainsi montré que l'introduction de la silice et le greffage de celle-ci avec le polymère conduisaient à des matériaux moins perméable, mais généralement plus sélectifThis work consisted to synthesize a hybrid material polyimide/silica by sol-gel process. The preparation of these materials has a problem of compatibility between the phases organic and inorganic. Silica and polymer do not have particular affinity and tend to create strong phase segregation. To avoid this phenomenon several solutions were reported ln the literature, like the use of coupling agent. In our case, we reduced this phenomenon by creating covalent bonds between polyimide and silica. For that, we fixed along the backbone of polyimide some functions alkoxysilanes which are reactive with silica functions. These functions will react with silica during the sol-gel process. We varied various parameters such as the grafting rate between polymer and silica, or catalyst used at the time of the sol-gel process. The continuation of work consisted in studying the various morphologies obtained according to the evolution of the parameters of synthesis. For that, we used various techniques such as the thermogravimetric analysis, the determination of density, the infra-red spectroscopy, or microscopy. This work enabled us to determine the silica rates, the size of the particles within the matrix and their state of dispersion. We also studied the microstructure of our materials per dynamic mechanical spectroscopy. Indeed, different morphologies have various effects on the reinforcement of silica. We thus could identify phenomena of percolation for some of our materials. In a last time, we studied the properties of gas permeation of our materials, in order to draw the great evolutions from the coefficients of permeability and selectivity according to the silica rate and from the rate of grafting between the organic and inorganic phase. We thus showed that the introduction of silica and the grafting of this one with polymer conducted to materials less permeable, but generally more selective
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Roux, Richard. "Synthèse de phase stationnaires monolithiques de silice hybrides pour les techniques séparatives miniaturisées." Thesis, Lyon 1, 2009. http://www.theses.fr/2009LYO10208.
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Ce manuscrit est consacré à la synthèse par procédé sol-gel et à la caractérisation de matériaux monolithiques de silice hybrides pour les techniques séparatives miniaturisées : nano-chromatographie en phase liquide (nano-CPL), électrochromatographie capillaire (ECC) et microsystèmes séparatifs. La partie bibliographique situe les axes de développement récents des techniques séparatives : l’augmentation de l’efficacité par unité de temps, l’augmentation de la capacité de pics et la miniaturisation de ces techniques. Après un descriptif détaillé de l’évolution des techniques séparatives lors de ces dernières années, une attention particulière est portée sur les phases stationnaires monolithiques à base de silice. Enfin, une étude approfondie des différentes fonctionnalisations de ces monolithes de silice met en évidence l’intérêt porté aux monolithes de silice hybrides en termes de simplification du protocole de synthèse. La partie expérimentale est ainsi axée sur le développement et la caractérisation de ces monolithes de silice hybrides dédiés à la chromatographie à polarités de phases inversée. Dans un premier temps, la synthèse de monolithes de silice hybrides C3 illustre la possibilité de synthétiser par voie sol-gel (100% aqueux) un monolithe de silice fonctionnalisé et performant en une seule étape (« one pot »). Dans un second temps, ce type de procédé est employé et optimisé afin de synthétiser des capillaires monolithiques de silice hybrides C8 présentant des performances équivalentes à leurs homologues C8 préparés en deux étapes (synthèse puis greffage) et comparables à des colonnes particulaires (d particules 5 μm)This manuscript is dedicated to the synthesis (via sol-gel process) and caracterization of hybrid monolithic silica for miniaturized separation techniques : nano-liquid chromatography (nano-LC), capillary electrochromatography (CEC) and microchips. The bibliography part deals with the recent axis of development of these separatives techniques : increase of efficiency per time unit, increase of peak capacity and miniaturisation of these techniques. After an overview of this evolution, the manuscript is focused on the silica monolithic stationnary phases. Finally, a detailed study on the different kinds of protocol fonctionnalization of these silica monoliths highlights the advantage of simplifying the synthesis using a single step protocol (« one pot »). The experimental part is also focused on this kind of single step protocol so as to synthesize hybrid silica monoliths dedicated to the reversed phase mode in chromatography. First, the synthesis of hybrid C3 silica monoliths shows the ability to synthesize a functionnalized silica monolith via a single step sol gel process (« one pot »). Then, this kind of process is used and optimized in order to synthesize a hybrid C8 silica monolithic into capillaries. These stationary phases allowed reaching performances similar to those synthesized in two steps (sol-gel process and grafting) and to the particulate columns (5 μm)
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Martin, Julie. "Design and direct synthesis of peptide-branched polysiloxane. Towards new generation of hybrid biomaterials." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS093.
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Les travaux de recherches de cette thèse concernent la conception et la synthèse de nouveaux matériaux hybrides basés sur un squelette polysiloxane. Pour cela, plusieurs molécules ont été silylées dans le but d’être incorporées dans une chaine de silicone multifonctionnel. En effet, au contraire des approches de post-greffages, nous avons mis au point une copolymérisation directe de ces macromonomères hybrides présentant une fonction methyldihydroxysilane avec du dichlorodimethylsilane (DCDMS). Plusieurs types de biomolécules ont été silylées : peptides, médicaments, sondes pour l’imagerie, chacune de ces molécules apportant des propriétés particulières au matériau final. Trois principales applications sont présentées : (i) la synthèse directe de film de silicone réticulés bioactifs, (ii) la préparation de nanoparticules (NPs) de silicone multifunctionnel (iii) ou des polyplexes. Des films de PDMS bioactifs (antibactériens ou promouvant l’adhésion cellulaire) réticulés ont été obtenus par copolymérisation de macromonomères hybrides peptidiques avec du DCMS et des monomères silane ou vinyl silane permettant une réticulation par hydrosilylation. Les NPs de silicone hybride sont issues de l’introduction de plusieurs macromonomères hydrophiles de 0.5 à 1mol% par rapport au DCDMS. Des ligands peptidiques ciblant les cellules cancéreuses, du PEG et du méthotrexate, tous trois silylés, ont été préparés et copolymérisés. Enfin, nous présentons les résultats préliminaires obtenus pour la préparation de polyplexes de siRNA basés sur la polymérisation in situ de peptides hybrides possédant des séquences riches en histidine et lysineThe purpose of this PhD work was the design and synthesis of new hybrid biomaterials based on a polysiloxane backbone. To do so, several biomolecules were silylated, in order to be incorporated in a multifunctional silicone backbone by a bottom-up strategy. Indeed, in contrast to post-grafting approaches, we set up the direct copolymerization of hybrid biomolecule macromonomers presenting a methyldihydroxysilyl moiety, with the dichlorodimethylsilane (DCDMS). Different types of biomolecules have been silylated: peptides, drugs and imaging probes, each of them affording specific properties to the final bioorganic silicone material. Three main applications are described: (i) the design and synthesis of bioactive PDMS cross-linked materials, (ii) silicone-based nanoparticules (NPs) and (iii) silicone-based polyplexes. PDMS materials with biological properties, either antimicrobial or cell adhesion, were obtained by copolymerization of hybrid peptide macromonomer with DCDMS, vinyl and silane reagents followed by hydrosilylation. Silicone-based NPs resulted from the introduction of several hydrophilic macromonomers at 0.5 to 1 mol% compared to DCDMS. Hybrid peptide ligands targeting cancer cell receptors, PEG and a drug model (Methotrexate) were prepared and copolymerized. At last, we investigated the preparation of siRNA polyplexes involving LysHis-based hybrid peptide macromonomers by an in situ polymerization method
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Le, Bail Nicolas. "Conception, synthèse par chimie douce et caractérisation de revêtements sol-gel hybrides multifonctionnels sur polycarbonate." Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0040/document.
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Le polycarbonate (PC) est un matériau polymère très répandu, fort apprécié pour sa faible densité, sa transparence, ses bonnes propriétés mécaniques et surtout pour son faible coût. Même s’il présente quelques limites essentiellement liées à sa faible résistance à l’abrasion, à la rayure et à sa dégradation dans le temps (sous UV ou hydrolyse), le PC trouve sa place dans un large spectre d’applications (bâtiment, automobile, médical, optique…). Il reste à ce jour indispensable sur ce marché car aucun autre polymère ne présente d’aussi bonnes propriétés mécaniques à prix égal. C’est dans ce contexte que ces travaux de thèse ont permis de développer une solution permettant de protéger le PC de toute agression extérieure par le dépôt d’un revêtement protecteur. L’étude s’est orientée vers le dépôt d’un film hydride organique / inorganique à base de silice, préparé par voie sol-gel, ce procédé permettant une élaboration à une température compatible avec la température de transition vitreuse du PC (Tg) (148°C). Les solutions retenues pour obtenir un revêtement performant sont basées sur la synthèse de revêtements hybrides à base d’oxydes de silicium et de zirconium. Une attention particulière a été portée sur l’augmentation de l’adhérence du film au substrat d’une part, et l’optimisation du procédé (synthèse et traitement de densification), d’autre part. Les résultats sont présentés d’un point de vue physico-chimique (IR, XRR, RMN) et mécanique (nanoindentation, adhésion et test à la rayure)The polycarbonate is a widespread polymer material, highly appreciated for its low density, its transparency and its good mechanical properties. This material is used for divert applications (automotive, medical, optical...) and is very competitive in terms of quality and prices. However, it displays some weaknesses, essentially due to its poor abrasion and scratch resistance and its possible degradation under UV or hydrolysis. In this context, the PhD aim is to design and develop a new hybrid organic / inorganic protective coating with silica and zirconia based precursors prepared by the sol gel process, which allow a curing compatible with the polycarbonate's Tg (148°C). Here, it is discussed on the solutions retained to obtain a scratch resistant, hydrophobic and transparent coating. It is showed that, scratch resistant protective coatings can be deposited on pristine PC thanks to a performing hybrid organic / inorganic coating by modulating its bulk properties. Moreover, results demonstrate the key role played by a phenylsilane precursor in enhancing the adherence. Nanoindentation, scratch-test, NMR and FTIR analysis will be discussed
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Morigi, Francesca. "A green approach to mesoporous silica particles synthesis by sol-gel chemistry." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13434/.
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Mesoporous silica materials have a wide variety of applications in different sectors depending on their characteristic porosity, particle dimensions and functionalization. They are used as heterogeneous catalyst agents in industrial synthesis, stationary phase in chromatography or in biomedical applications as drug delivery systems. Consequently a significant number of studies have focused on the development of preparation methods that allow the regulation of the pore size and pore morphology of the silica. This thesis work, conducted at UCC (University College Cork, Ireland), aims to find a “greener” path than the one traditionally used to synthesize good quality mesoporous silica particles. It is a preliminary work whose purpose is to determine if it can be considered viable to start further systematic research in this direction. Nowadays it is impossible to ignore the need of an environmentally sustainable approach towards chemical synthesis and processes design. Green Chemistry and its Twelve Principles are central to the development of the mesoporous silica material preparation procedure utilized within this research. A modified Stöber sol-gel method of synthesis was chosen for its intrinsically green features: it is a batch process, the reaction takes place at room temperature and one of the main solvents is water. This study focuses on changing those aspects of the “standard” procedure which are not so environmentally friendly: the second solvent (alcohol), the surfactant (most commonly CTAB) and the post synthesis hydrothermal treatment. In particular Sodium Alginate, a polysaccharide extracted from the cell wall of brown seaweed, is the surfactant of choice. Until now no works have been reported on the use of alginate as a direct anionic surfactant template. Characterization of obtained silica particles was performed employing N2 sorption for information about porosity and SEM and TEM imaging to evaluate particles aggregation, aspect and size.
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Tan, Bing. "Controlled synthesis and functionalization of nanoporous sol-gel silica particles and gels." Lexington, Ky. : [University of Kentucky Libraries], 2005. http://lib.uky.edu/ETD/ukychen2005d00329/etd.pdf.
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Thesis (Ph. D.)--University of Kentucky, 2005.Title from document title page (viewed on November 2, 2005). Document formatted into pages; contains xix, 336 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 331-334).
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Wiener, Matthias. "Synthese und Charakterisierung Sol-Gel-basierter Kohlenstoff-Materialien für die Hochtemperatur-Wärmedämmung." kostenfrei, 2009. http://www.opus-bayern.de/uni-wuerzburg/volltexte/2010/4424/.
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Raval, Hema M. "Non-hydrolytic sol-gel synthesis of inorganic oxides and organic-inorganic hybrids." Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326496.
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Cheikh, Ibrahim Ajfane. "Synthèse des matériaux hybrides organiques inorganiques multifonctionnalisés." Thesis, Montpellier 2, 2012. http://www.theses.fr/2012MON20067/document.
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L'objet de cette thèse a été l'étude de la structuration et de la fonctionnalisation de matériaux hybrides organiques-inorganiques par le procédé sol-gel.La synthèse et la caractérisation de nouvelles membranes à conduction protonique, pour pile à combustible à membrane échangeuse de protons, ont été réalisées dans la première partie. Des membranes hybrides à base de polyéthylène glycol hautement fonctionnalisées par de l'acide sulfonique ont été synthétisées et caractérisées d'un point de vue physicochimique et conductivité protonique. Elles présentent des bonnes propriétés mécaniques, une stabilité chimique suffisante et une conductivité protonique pertinente pour être utilisées comme électrolyte dans les piles à combustible à membrane échangeuse de proton.Dans une seconde partie, nous avons développé des matériaux hybrides mésoporeux et multifonctionnalisés dans les pores en présence de tensioactif de type copolymère block non-ionique (P123). Deux sondes ont été utilisées pour cette étude: la capacité d'échange protonique et le contrôle de la croissance des nanoparticules d'or dans les poresThe aim of this work was focused on the structuration and the functionalization of organic-inorganic hybrid materials by the sol-gel process.The synthesis and characterization of new proton conductive membranes for fuel cell proton exchange membrane (PMFC), was prepared in the first part. Hybrid membranes based on polyethylene glycol highly functionalized with sulfonic acid have been synthesized and characterized through a physicochemical and proton conductivity. They have good mechanical properties, a sufficient chemical stability and a performant proton conductivity to be used as an electrolyte in fuel cell proton exchange membrane.In the second part, we have developed hybrid mesoporous materials with porous multifunctionalized in the presence of surfactant nonionic block copolymer (P123). Two probes were used for this study: the proton exchange capacity and the control of the growth of gold nanoparticles in the pores
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Gossard, Alban. "Synthèse d'oxydes par voie sol-gel colloïdale : application aux précurseurs de combustibles nucléaires." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2014. http://www.theses.fr/2014ENCM0010/document.
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Le recyclage des actinides mineurs produits en réacteur nucléaire est un point clé pour les cycles du combustible du futur. Différentes options sont ainsi envisagées : leur réintégration au sein d'un nouveau combustible « refabriqué » ou leur transmutation dans le but de réduire significativement la radiotoxicité des déchets ultimes. Dans ces deux cas de figure, la synthèse de matériaux innovants intégrant les actinides mineurs de manière homogène est nécessaire.En ce sens, les voies sol-gel présentent des avantages certains par rapport aux autres voies de synthèse (co-précipitation, métallurgie des poudres) tels que l'organisation du matériau à l'échelle colloïdale ou la création de porosité de manière contrôlée grâce à l'utilisation d'un « template ». De plus, la possibilité de travailler en milieu humide, de la solution précurseur au matériau final, permet d'éviter la formation de poudres pulvérulentes et contaminantes, point essentiel dans le cas de matériaux incorporant des éléments radioactifs. Cette thèse vise à démontrer l'adaptabilité de ce type de procédé au domaine du nucléaire. Dans un premier temps, une méthodologie de synthèse par voie sol-gel colloïdale et de caractérisation sur un système non-actif à base de zirconium a été mise en place et a permis la compréhension des mécanismes mis en jeu au cours de cette synthèse. Suite à cela, des études de mise en forme, et notamment d'insertion de porosité, ont été réalisées. Des monolithes de zircone ont de cette manière pu être obtenus grâce au couplage entre le procédé sol-gel colloïdal et la formation d'une émulsion stabilisée par des clusters de particules solides.Finalement, une transposition de ces travaux sur un système à base d'uranium a été initiée, soulevant différentes perspectives prometteuses concernant les possibilités de mise en forme du matériau finalOne of the main objectives for the future nuclear fuel cycle is the recycling of the minor actinides. Different options are considered: their integration into a new fuel for a prospect of a closed fuel cycle or their transmutation in order to significantly decrease the long-term radiotoxicity of ultimate wastes. In both cases, the synthesis of new advanced materials integrating the actinides jointly is required.Sol-gel processes allow the organization of the material at the colloidal scale or the insertion of controlled porosity using « templates ». Furthermore, the possibility to work in a « wet environment » prevents the formation of pulverulent powders which are contaminant in the case of materials incorporating radioactive elements. The main purpose of this work is to demonstrate the adaptability of this route to the nuclear field.Firstly, a methodology of synthesis from a colloidal sol-gel route was set up on a non-radioactive zirconium-based system in order to characterize and understand of the different mechanisms of this synthesis. Then, studies on shaping, including insertion of porosity, were performed. Zirconia monoliths have been obtained thanks to a coupling between a colloidal sol-gel process and the formation of an emulsion stabilized by clusters of solid particles. Finally, a transposition of this work to an uranium-based system was introduced, pointing out different promising perspectives specially concerning the possibilities of shaping of the final material
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Puy, Guillaume. "Synthèse et caractérisation de phases stationnaires monolithiques de silice pour les techniques séparatives miniaturisées." Lyon 1, 2006. http://www.theses.fr/2006LYO10282.
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Grund, Silke. "Synthese anorganisch-organischer Polyfurfurylalkohol-Nanokomposite durch die Zwillingspolymerisation." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-63440.
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In der vorliegenden Arbeit wird die kationische Polymerisation neuer Furanmonomere beschrieben, die zu anorganisch-organischen Nanokompositen führt. Die kationische Polymerisation des Tetrafurfuryloxysilans steht dabei im Vordergrund. Ausgehend von den synthetisierten Kompositen wird die Herstellung von anorganischen Oxiden durch thermische Oxidation und von Kohlenstoffmaterialien durch thermische Behandlung in Schutzgasatmosphäre beschrieben. Die Charakterisierung der Komposite, Oxide und Kohlenstoffmaterialien erfolgt mittels Festkörper-NMR-Spektroskopie, Röntgenbeugung und Elektronenmikroskopie. Das Prinzip der neu entdeckten Zwillingspolymerisation wird vorgestellt und anhand verschiedener Beispiele auf seine weitere Anwendbarkeit zur Synthese anorganisch-organischer Kompositmaterialien überprüft.
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Misso, Ágatha Matos. "Síntese e caracterização de fósforos a base de silicatos de cálcio e magnésio dopados com európio e disprósio." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-10042017-143712/.
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Fósforos a base de silicatos de Ca e Mg foram preparados pelo método sol-gel combinado com o processo de sais fundidos. O gel de sílica foi obtido a partir da solução de Na2SiO3 usando soluções de cloretos de európio, disprósio, cálcio e magnésio. Assim, estes cloretos foram homogeneamente distribuídos no gel. O gel obtido foi seco e tratado termicamente a 900°C por 1h para permitir a fusão dos sais presentes. Em seguida o material foi lavado com água até teste negativo para íons Cl- e seco em estufa a 80°C. A redução do európio para Eu2+ foi realizada em um forno sob atmosfera de 5% de H2 e 95% de Ar a 900°C por 3h para obter os fósforos de CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+. Nos difratogramas de DRX das amostras, a diopsita foi identificada como fase cristalina principal e quartzo, como a secundária. Micrografias obtidas por MEV (microscopia eletrônica de varredura), das amostras, mostraram morfologia acicular, esférica, folhas e bastonetes das partículas e dos aglomerados . Curva de análise térmica (TGA-DTGA) revelou que a temperatura de cristalização do CaMgSi2O6:Eu2+ é próxima de 765°C. Estudos de espectroscopia de fotoluminescência foram baseados nas transições interconfiguracionais 4fN → 4fN-1 5d do íon Eu2+. O espectro de excitação apresentou banda larga relativa à transição de transferência de carga ligante metal (LMCT) O2- (2p) → Eu3+ na região de 250 nm e bandas finas oriundas das transições 4f → 4f do íon Eu3+ , mostrando a transição 7F0 → 5L6 em 393 nm quando a emissão é monitorada em 583,5 nm. E o espectro de emissão com excitação monitorada em 393 nm apresentou picos finos entre 570 e 750 nm característicos das transições 5D0 → 7 FJ (J = 0 - 5) do íon Eu3+ , indicando que o íon Eu3+ se encontra em um sítio com centro de inversão. Os resultados obtidos indicam que o método desenvolvido é viável na síntese de fóforos, CaMgSi2O6:Eu2+ e CaMgSi2O6:Eu2+:Dy3+ como foi proposto.Ca and Mg silicates based phosphors were prepared by sol-gel method combined with the molten salts process. The gel of silica was obtained from Na2SiO3 solution by using europium, dysprosium, calcium and magnesium chloride solutions. Therefore, those chlorides were homogenously dispersed into the gel. The obtained gel was dried and heat treated to 900° C for 1h to allow the fusion of the present salts. Then it was water washed until negative test for Cl-, and dried. The reduction of the europium to Eu2+ was performed under atmosphere of 5% of H2 and 95% of Ar to 900° C for 3h, to reach CaMgSi2O6:Eu2+ and CaMgSi2O6:Eu2+:Dy3+ phosphors. Diopside was identified as main crystalline phase and quartz, as secondary phase from XRD (X-ray diffraction) patterns. SEM (scanning electron microscopy) micrographs, of the samples showed needles, spheres, leaves and rods of particles and agglomerates. Thermal analysis (TGA-DTGA) curves revealed that the crystallization temperature of CaMgSi2O6:Eu2+ lies around 765° C. Photoluminescence spectroscopy of the phosphors was studied based on interconfigurational 4fN → 4fN-1 5d transition of Eu2+ ion. The spectra of excitation showed 4fN → 4fN-1 5d transition of Eu2+ ion broad band, related to the ligand to metal charge transfer transition (LMCT) O2- (2p) → Eu3+ in the 250 nm region, when the emission is monitored at 583,5 nm. It also presents the 4f ↔ 4f transitions of Eu3+ ion bands, showing the 7F0 → 5L6 transition at 393 nm. From emission spectra with excitation monitored at 393 nm, it can be observed fine peaks between 570 and 750 nm which are characteristics of 5D0 7FJ (J = 0 - 5) transition of Eu3+ ion, indicating that the Eu3+ ion occupies a site with center of inversion. Finally, the obtained results indicate that the developed method is suitable to synthesize CaMgSi2O6:Eu2+ and CaMgSi2O6:Eu2+:Dy3+ phosphors, as it has been proposed.
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Cristini-Robbe, Odile. "Synthèse de poudres céramiques conductrices par procédé sol-gel assisté par du Co2 supercritique : étude des caractéristiques morphologiques, structurales et électriques." Montpellier 2, 2003. http://www.theses.fr/2003MON20195.
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Bieri, Fabian. "Sol-Gel Synthese von Vanadiumoxid-Nanoröhren und Eisenoxidnanopartikeln sowie deren Charakterisierung und Mikrostrukturierung /." [S.l.] : [s.n.], 2003. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15301.
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Matsuoka, Jun. "STUDIES ON SOL-GEL SYNTHESIS AND PROPERTIES OF GOLD MICROCRYSTAL-DOPED OXIDE FILMS." Kyoto University, 1998. http://hdl.handle.net/2433/157042.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・論文博士
博士(工学)
乙第9845号
論工博第3335号
新制||工||1116(附属図書館)
UT51-98-G444
(主査)教授 曾我 直弘, 教授 小久保 正, 教授 横尾 俊信
学位規則第4条第2項該当
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ZNAIDI, LAMINA. "Synthese des bronzes de vanadium pour procedes sol-gel : caracterisation structurale et proprietes." Paris 6, 1989. http://www.theses.fr/1989PA066530.
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Dans ce travail, nous avons montre que l'on peut preparer des bronzes de vanadium a partir des procedes sol-gel. On utilise a ce propos les proprietes d'intervalation du xerogel de v#2o#5. Les bronzes de vanadium sont obtenus par traitement thermique des xerogels intercales. L'interet de cette methode est d'augmenter l'anisotropie initiale du materiau et d'ameliorer sa reactivite chimique. On obtient en effet des materiaux en couche a orientation preferentielle extremement marquee. L'influence de cette orientation sur les proprietes electriques et electrochimiques fait l'objet de la derniere partie de ce travail; on a montre en particulier que le bronze de vanadium au sodium pouvaient etre utilise comme cathode reversible de generateurs electrochimiques au lithium
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Di, Giampaolo Anna Rita. "Elaboration de cordierite a basse temperature : synthese par voie sol-gel et densification." Limoges, 1987. http://www.theses.fr/1987LIMOA034.
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On a utilise deux methodes de preparation du sol colloidal basees sur l'hydrolyse et la polycondensation d'alcoolates metalliques en milieu acide. Les parametres ont ete optimises pour favoriser la densification et la recristallisation a basse temperature. Les echantillons ont ete caracterises par analyse thermique, dilatometrie, mesure de densite, diffraction et diffusion rx centrale. Les xerogels presentent des densites relatives faibles dues a la presence d'une porosite a l'echelle macromoleculaire formee lors de l'evacuation du solvant. Pour y remedier, on a utilise une methode de sechage hypercritique. L'aerogel resultant est un materiau de tres faible compacite, constitue de particules elementaires denses. L'evolution de la porosite entre les particules, lors du traitement thermique, conduit a l'obtention d'un materiau amorphe dense. Une ceramique constituee essentiellement de cordierite est obtenue en dessous de 1000 non= c
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In, Martin. "Chimie des procedes sol-gel appliquee a la synthese de copolymeres organiques-inorganiques." Paris 6, 1994. http://www.theses.fr/1994PA066154.
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La chimie des procedes sol-gel a multiplie les voies d'elaboration de materiaux hybrides organiques-inorganiques. Mais jusqu'a present, ce domaine s'est cantonne a la chimie du silicium. Dans ce travail, nous proposons un mode de synthese de materiaux hybrides dont la composante minerale est constituee d'oxyde de zirconium. La difficulte de synthese d'un tel materiau est liee a la fragilite de la liaison metal-carbone dans le cas des metaux de transition. Elle est contournee par l'utilisation de precurseurs metallo-organiques heterofonctionnels. De facon generale, la polycondensation des alcoxydes de metaux de transition est moins comprise que celle des alcoxydes de silicium. La premiere partie de l'etude lui est consacree. Nous montrons que malgre leur tres grande reactivite, les alcoxydes de metaux de transition sont impliques dans des reactions equilibrees d'hydrolyse et condensation. Cela conduit aux consequences importantes suivantes: les polycondensats formes sont encore riches en ligands organiques ; leur croissance est localement anisotrope et aboutit a la formation de tiges rigides. La presence de ligands organiques a l'issue de la polycondensation minerale permet d'envisager la synthese de materiaux hybrides. La premiere etape de cette synthese est la preparation de precurseurs heterofonctionnels. Ceux-la sont obtenus en substituant a une partie des ligands monodentates (or) du propoxyde de zirconium, des ligands chelatants polymerisables par voie radicalaire. Dans ce travail, le ligand polymerisable est l'acetoacetoxyethylmethacrylate. Les precurseurs heterofonctionnels obtenus sont ensuite mis en situation de polymeriser simultanement par polycondensation inorganique (activee par addition d'eau) et polyaddition radicalaire (initiee par l'aibn). Les polymeres ont ete caracterises en solution et a l'etat solide dans le but de prouver la realisation des deux types de polymerisation et aussi la conservation du lien chimique entre motifs organiques et mineraux. Le caractere mixte organique-mineral a l'echelle nanometrique est la consequence d'un antagonisme entre les deux types de polymerisation
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Zhou, Xiuquan. "Non-hydrolytic Sol-gel (NHSG) Synthesis of Transition Metal Sulfides and Theoretical Investigations." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365030696.
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