Die steigende Anzahl an Verfahren, in denen eine Filtration und eine Aufreinigung des gebildeten Filterkuchens durch Waschung notwendig ist, und die Steigerung deren Effizienz und Wirtschaftlichkeit verlangen nach einer Optimierung der Prozesse. Die Erarbeitung eines grundlegenden Verständnisses der Verdrängungsprozesse zwischen polaren und unpolaren Flüssigkeiten in einem Haufwerk schafft Erkenntnisse, die bei der Auswahl der verwendeten Lösungsmittel/Feststoffkombinationen während des Syntheseweges hilfreich sind. Durch die Verwendung von Silanen als Beschichtung kann die Oberflächeneigenschaft der Partikel variiert werden, während granulometrische Eigenschaften konstant bleiben. So dienen die Partikelsysteme als Basis der Untersuchungen zum Einfluss der Benetzungseigenschaften auf die Waschung unter Ausschluss anderer prozessbestimmender Variablen. Bei der Waschung der Partikelsysteme muss die Bedeutung der sich ausbildenden Phasengrenze herausgestellt werden. Sind Wasch- und Porenflüssigkeit nicht mischbar, bestimmt die auftretende Flüssig/Flüssig-Phasengrenze die Phänomenologie und die Effizienz des Prozesses. Das Auftreten einer Phasengrenze zwischen beiden Flüssigkeiten erlaubt die Aufnahme einer Flüssig/Flüssig-Kapillardruckkurve, die als Grenzkurve die zu erwartenden technischen Waschergebnisse darstellt. So kann eine Aussage darüber getroffen werden, welche Austauschverhältnisse und Restgehalte an Verunreinigung im Kuchen bei der Auswaschung mit nichtmischbaren Flüssigkeiten maximal zu erwarten ist.:ABBILDUNGSVERZEICHNIS SYMBOLVERZEICHNIS 1 EINLEITUNG 2 GRUNDLAGEN 2.1 FILTRATION 2.1.1 Kuchenbildung 2.1.2 Entfeuchtung 2.2 FILTERKUCHENWASCHUNG 2.3 SYSTEMEIGENSCHAFTEN 2.3.1 Feststoffe 2.3.2 Flüssigkeiten 2.3.3 Suspension 2.3.4 Haufwerk- und Kuchenstruktur 2.4 GRENZFLÄCHEN UND BENETZUNG DISPERSER SYSTEME 2.4.1 Oberflächenenergie 2.4.2 Benetzung 2.4.3 Kapillarität 2.5 BENETZUNG UND KAPILLARITÄT IN BEZUG ZUR FILTRATION 2.5.1 Die Kapillardruckkurve 2.5.2 Zusammenspiel von Benetzung und Filtration 2.5.3 Die Umnetzungskurve 2.6 SILANE – AUFBAU UND FUNKTION 3 MATERIALIEN UND METHODEN 3.1 STOFFSYSTEME 3.1.1 Partikelsystem 3.1.2 Flüssigkeiten 3.1.3 Silane 3.2 SILANISIERUNG ZUR VARIATION ZUR BENETZUNG 3.3 FESTSTOFFCHARAKTERISIERUNG 3.3.1 Laserbeugung 3.3.2 Statische Bildanalyse 3.3.3 Rasterelektronenmikroskopie 3.3.4 Energiedispersive Röntgenspektroskopie 3.3.5 Stickstoffadsorption 3.3.6 Thermogravimetrische Analyse 3.3.7 Ellipsometrie 3.3.8 Goniometrie 3.4 PROZESSRELEVANTE FLUID- UND SUSPENSIONSCHARAKTERISIERUNG 3.4.1 Tensiometrie 3.4.2 Grenzflächenrheometrie 3.4.3 Sedimentations- und Kompressionsmessung 3.5 VERSUCHSDURCHFÜHRUNG 3.5.1 Filtration 3.5.2 Waschung 3.5.3 Bestimmung Filtrat- und Retentatkonzentration 3.5.4 Kapillardruckkurve 3.5.5 Umnetzungskurve 4 OBERFLÄCHENKONFIGURATION DER PARTIKELSYSTEME MITTELS SILANEN 4.1 VARIATION DER OBERFLÄCHENENERGIE 4.2 AUSBILDUNG DER SILANSCHICHT 4.3 KONSISTENZ DER DISPERSEN FESTSTOFFEIGENSCHAFTEN 5 BENETZUNGSEFFEKTE BEI DER WASCHUNG VON FILTERKUCHEN 5.1 STRUKTURBILDUNG BEI DER FILTRATION 5.1.1 Sedimentationseigenschaften 5.1.2 Filterkuchenbildung 5.2 KUCHENWASCHUNG 5.2.1 Kuchenwaschung mit mischbaren Systemen 5.2.2 Kuchenwaschung mit nichtmischbaren Systemen 5.2.3 Viskositätsdifferenz 5.2.4 Nachweis der aufgestellten Theorien 6 DARSTELLUNG DES WASCHUNGSGLEICHGEWICHTES ÜBER EINE UMNETZUNGSKURVE 6.1 MESSTECHNISCHE ERFASSUNG 6.1.1 Technische Methode 6.1.2 Druckmethode 6.2 HAUPTEINFLUSSPARAMETER AUF DIE UMNETZUNGSKURVE 6.2.1 Variation der Benetzung 6.2.2 Variation der Partikelform 6.2.3 Variation der Partikelgröße 6.3 VERGLEICH: UMNETZUNGS- UND KAPILLARDRUCKKURVEN 7 SCHLUSSWORT LITERATURVERZEICHNIS ANHANG

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

Semiconductor quantum dots (QDs), particles several nanometers in diameter, exhibit a range of interesting properties that arise as a result of quantum confinement. Among these characteristics is photoluminescence, and unlike traditional fluorophores, the fluorescence emission of QDs is characterized by broad absorption and narrow emission that is a function of the particle diameter. This allows high spatial resolution to be achieved using spectral discrimination of closely spaced QDs.We propose applying QD fluorescence as a tool to sense the local environment of the QD to achieve wide-field sensing at high-resolution. Many factors influence QD fluorescence from the growth parameters and choice of ligand to the local environment of the QD post-fabrication. Nano-materials in the local QD environment influence the spectral or temporal characteristics of the QD fluorescence and detecting these changes enables identification of the location and motion of these nanoparticles with resolution on the order of a few nanometers.We have fabricated aqueous colloidal cadmium telluride QDs, experimenting with the choice of thiol-based ligand to influence the chemistry in post-processing and application. A wide range of tools have been used to characterize the spectral and physical properties of the QDs. We have successfully immobilized QDs on a variety of substrates including glass coverslips, silicon and indium tin oxide coated glass. Immobilization is achieved with even and consistent distributions of QDs on the substrate by using self-assembly of the colloidal particles onto substrates functionalized with N1-(3-Trimethoxysilylpropyl)diethylenetriamine (DETA) silane.Using fluorescence microscopy we have successfully demonstrated the detection of interactions between QDs and other nano-materials including green fluorescent protein and gold seed particles, demonstrating that QDs may, in principle, be used in a wide field microscopy technique to sense nano-materials with high resolution.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Siew-Hoon Lee. / M.S.

The first two chapters of this thesis are devoted to exploring the reactivity of electron rich molybdenum and tungsten trimethylphosphine complexes with hydrosilanes. These complexes, Mo(PMe3)6 and W(PMe3)4(n2-CH2PMe2)H, have been shown to be highly reactive species that undergo a number of bond cleavage reactions. In the presence of the hydrosilanes PhxSiH4-x (x = 0 - 4), Mo(PMe3)6 and W(PMe3)4(n2-CH2PMe2)H effect Si-H and Si-C bond cleavage, along with Si-Si bond formation; however, the products derived from these reactions are drastically different for Mo(PMe3)6 and W(PMe3)4(n2-CH2PMe2)H and are highly dependent on the substitution of the silane. Mo(PMe3)6 reacts with SiH4, PhSiH3, and Ph2SiH2 to afford novel silyl, hypervalent silyl, silane, and disilane complexes, as respectively illustrated by Mo(PMe3)4H2(SiH3)2, Mo(PMe3)4H(k2-H2-H2SiPh2H), Mo(PMe3)3H4(s-HSiHPh2), and Mo(PMe3)3H2(k2-H2-H2Si2Ph4). Mo(PMe3)4H(k2-H2-H2SiPh2H) is the first example of a complex with a hypervalent [H2SiPh2H] ligand, and Mo(PMe3)3H2(k2-H2-H2Si2Ph4) represents the first structurally characterized disilane complex. In addition to being structurally unique, these complexes also possess interesting reactivity. For example, Mo(PMe3)4(SiH3)2H2 undergoes isotope exchange with SiD4, and NMR spectroscopic analysis of the SiHxD4-x isotopologues released indicates that the reaction occurs via a sigma bond metathesis pathway. In contrast, W(PMe3)4(n2-CH2PMe2)H affords a range of products that includes metallacycle, disilyl, silane, and bridging silylene complexes. The disilyl compounds, W(PMe3)4H3(SiH2SiHPh2) and W(PMe3)3H4(SiH2Ph)(SiH2SiHPh2), exhibit the ability of W(PMe3)4(n2-CH2PMe2)H to cause both redistribution and Si-Si bond formation. A mechanism involving silylene intermediates is proposed for the generation of these complexes, and this mechanism is supported computationally. Additional support for the presence of intermediates comes from the isolation of a unique complex with a bridging silylene ligand, "WSiW". The bridging silylene bonding motif is unprecedented. The reactivity of the simplest hydrosilane, SiH4, was also examined with IrCl(CO)(PPh3)2 (i.e. Vaska's compound). Previous reports on this reaction have assigned the product as trans-IrH(SiH3)(Cl)(CO)(PPh3)2, in which the hydride and silyl ligands are mutually trans. It is noteworthy, therefore, that we have now obtained a crystal structure of the product of this reaction in which the hydride and silyl ligands are cis, namely cis-IrH(SiH3)(Cl)(CO)(PPh3)2. Calculated energies of the isomeric species also suggest that the product of this reaction was originally misassigned. These results, and the analogous reactions with germane (GeH4), are described in Chapter 4. Chapter 4 also discusses some reactions of transition metal phosphine complexes, including Ru(PMe3)4H2, Mo(PMe3)6, W(PMe3)4(n2-CH2PMe2)H, and Mo(PMe3)4(n2-CH2PMe2)H, with industrially relevant substrates. Ru(PMe3)4H2 effects the water gas shift reaction of CO and H2O to form CO2 and H2. Furthermore, Ru(PMe3)4H2 reacts with CO2, CS2, and H2S to respectively form formate, thiocarbonate, and hydrosulfido complexes. The reactivity of Mo(PMe3)6 and W(PMe3)4(n2-CH2PMe2)H towards molecules relevant to the hydrodeoxygenation industry, including dihydrofuran and benzofuran, was studied. The products of these reactions exhibit hydrogenation of unsaturated bonds and C-O bond cleavage, both of which are essential to the hydrodeoxygenation process. Mo(PMe3)4(n2-CH2PMe2)H reacts with PhI to form an alkylidyne species, [Mo(PMe3)4(CPMe2Ph)I]I, which was structurally characterized by X-ray diffraction. W(PMe3)4(n2-CH2PMe2)H forms a k2-adduct when treated with 2-seleno-2-methylbenzimidazole, namely W(PMe3)4(sebenzimMe)H. Chapter 3 discusses the development of two new ruthenaboratrane complexes, [k4-B(mimBut)3]Ru(CO)(PR3) (R = Ph, Me). The structures of these complexes are described, and their d6 metal configuration is supported by both Fenske-Hall and Natural Bond Orbital calculations. Some reactivity of these complexes was also explored. For example, [k4-B(mimBut)3]Ru(CO)(PMe3) appears to add MeI across the Ru-B bond. Finally, as an extension of the work that we have done on tungsten trimethylphosphine complexes, the structure of W(PMe3)3H6 in solution was investigated, and the results are presented in Chapter 5. T1 measurements of the hydride ligands and deuterium isotope effect shifts both confirm that this complex exists as a classical hydride in solution, which is in accord with the classical hydride formulation in the solid state that was previously determined by X-ray diffraction.

A proteção contra a corrosão do aço galvanizado com um tratamento via cromatização, apesar de apresentar desempenho superior à outras alternativas, gera efluentes tóxicos ao meio ambiente e em especial aos seres humanos. Dentre as alternativas apresentadas até o presente momento, que incluem diversos tipos de tratamentos para esse substrato, um deles é o revestimento com silanos. Apesar desse revestimento ter um satisfatório desempenho, vem se utilizando incorporações em seu preparo, para se potencializar seu desempenho. A incorporação escolhida nesse trabalho foi a do tanino, um inibidor de corrosão natural, extraído de vegetais. O objetivo desse trabalho é avaliar um revestimento do silano Ortossilicato de tetraetila (TEOS) junto de um tanino para o aço galvanizado destinado a aplicações onde não há pintura. Essa sinergia deve proteger a superfície até que o zinco consiga de forma natural desenvolver sua pátina protetora, formando uma barreira entre substrato e eletrólito. Foram revestidas chapas de aço galvanizado com períodos de imersão que variaram entre 2 e 10 minutos, com soluções na concentração de tanino de 2g/L e 10g/L com diferentes valores de pH, em uma solução previamente preparada de TEOS em concentração de 2%, água 49% e etanol 49%. Realizou-se análise comparativa entre os diferentes parâmetros de tratamento proposto neste trabalho com aço galvanizado somente desengraxado e aço galvanizado cromatizado nas seguintes técnicas: espectroscopia de impedância eletroquímica, polarização potenciodinâmica, microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva, e ensaios de corrosão acelerada em câmara úmida e névoa salina. Os resultados apresentados indicam que diferentes concentrações de tanino e tempos de imersão não são significativos para causar diferenças relevantes entre os desempenhos e que os substratos tratados demonstraram um desempenho superior comparado às amostras que não tinham nenhum tipo de tratamento e inferiores às amostras cromatizadas. / The corrosion protection of galvanized steel with a chromatized treatment, despite superior performance to other alternatives, generates effluents toxic to the environment and especially to humans. Among the alternatives presented to date, which include several types of treatments for this substrate, one of them is the coating with silanes. Although this coating has a satisfactory performance, it has been using incorporations in its preparation, to enhance its performance. The incorporation chosen in this work was that of tannin, a natural corrosion inhibitor, extracted from plants. The objective of this work is to evaluate a coating of silane tetraethyl orthosilicate (TEOS) with tannin for galvanized steel, for applications where there is no paint. This synergy should protect the surface until zinc can naturally develop its protective patina, forming a barrier between substrate and electrolyte. Galvanized steel plates were coated with immersion times ranging from 2 to 10 minutes, with solutions at tannin concentration of 2 g/L and 10 g/L with different pH values, in a previously prepared solution of TEOS at a concentration of 2% , 49% of water and 49% of ethanol. A comparative analysis was performed between the different treatment parameters proposed in this work with galvanized steel only degreased and galvanized steel chromatized in the following techniques: electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning electron microscopy coupled to dispersive energy spectroscopy, and corrosion tests accelerated in humid chamber and saline mist. The results indicated that different concentrations of tannin and immersion times are not significant to cause relevant differences between the performances and that the substrates demonstrated superior performance compared to the samples that had no type of treatment, and inferior to the samples chromatized.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Cet ouvrage s'inscrit dans le but de comprendre les mécanismes liés à la morphogenèse des nanostructures de silicium hydrogéné dans un réacteur plasma par des techniques de modélisation. Dans un premier temps les technologies actuelles sont passées en revue afin de répondre aux attentes actuelles qui leurs sont propres. Vient ensuite un rappel des possibilités d'étude qui sont utilisables dans ce contexte particulier. Les différentes techniques qui permettent de simuler les trajectoires des atomes par dynamique moléculaire sont rappelées. Les méthodes quantiques de calcul de potentiel d'interaction entre les espèces chimiques sont ensuite développées pour conclure que seules des méthodes quantiques semi-empiriques sont suffisament rapides pour pouvoir implémenter un algorithme de dynamique moléculaire quantique sur des échelles de temps raisonnables. A partir des outils introduits, une réfléxion sur la nature des états moléculaires énergétiquement métastables est présentée sur un cas théorique de croissance autoorganise d'une chaîne linéaire d'atomes. Ce modèle qui consiste à faire croître une chaîne par l'ajout successif de l'atome qui augmente le moins l'énergie électronique de la chaîne montre que le niveau de Fermi est un paramètre essentiel à l'autoorganisation de la croissance. Ce modèle montre aussi que la structure formée n'est pas forcément une structure de minimum global d'énergie. A partir de tous ces outils numériques, la croissance d'agrégats moléculaire peut être simulée en utilisant comme paramètres les données issues de calculs de magnétohydrodynamique des conditions reignant au sein des réacteurs plasma ( concentrations des espèces, intervalle de temps entre les réactions chimiques, énergie d'impact des réactifs ...). La formation d'agrégats de silicium hydrogéné est ainsi simulée par captures successives de molécules de silane. Les structures formées en simulation aux températures de fonctionnement des réacteurs plasma prédisent la formation d'agrégats sphériques constitués d'un coeur de silicium amorphe recouvert par de l'hydrogène. Ces structures ne sont donc pas dans un état de minimum d'énergie contrairement à certains résultats expérimentaux. Ces résultats ont cependant été obtenus sans la prise en compte de la présense d'hydrogène atomique dans le plasma. Une étude approfondie de l'effet de l'hydrogène atomique sur les structures métastables produites en simulation est donc effectuée. L'étude de l'interaction de l'hydrogène atomique sur la surface de l'agrégat permet de trouver des proportions de mécanismes (désorption d'hydrogène de type Eley-Rideal, atome chaud ou absorption sur la surface de l'agrégat) en accord avec des experiences de recombinaison sur des surfaces de silicium. Les interactions de l'hydrogène atomique avec la surface des agrégats induisent aussi une modification de l'organisation interne des atomes de silicium. L'organisation des atomes de silicium interne à agrégats en fonction de la taille de l'agrégat (nombre magique) permet de comprendre pourquoi les observations expérimentales indiquent la présence de structures cristallines. Enfin cette étude mène à la prédiction d'une structure particulièrement stable qui pourrait servir de germe de croissance pour les nanofils de silicium.

Thèse de doctorat : Chimie organique : Strasbourg 1 : 2008. / Titre provenant de l'écran-titre. Bibliogr. p. 105-110.

Thèse doctorat : Génie des Matériaux : Villeurbanne, INSA : 2004. / Titre provenant de l'écran-titre. Réf. bibliogr. à la fin de chaque chapitre.