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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Development of an Environmentally Benign Anticorrosion Coating for Aluminum Alloy Using Green Pigments and Organofunctional Silanes

Yin, Zhangzhang January 2009 (has links)
No description available.
102

Substituent Effects and Trends in the Formation and Characterization of Cyclopentadienyl Bisphosphine Ruthenium(II) Silyl and Eta-2 Silane Complexes

Freeman, Samuel T.N. 28 October 2002 (has links)
No description available.
103

Evaluation of Water Absorption and Mechanical Properties of Natural Fiber Composites Made with Silane Treated Kenaf Fibers

Shen, Yan 12 May 2012 (has links)
The objective of this research was to investigate the hydrophilic and mechanical properties of kenaf fiber treated with vinyl tris(2-ethoxymethoxy) silane (VTEMS) and the resulting fiber/resin composite. The hypothesis was that silane-modified kenaf fibers, when used to make Sheet Molding Compounds (SMCs), would improve the water resistance and mechanical properties compared to unmodified kenaf fibers, and these potentially improved SMCs may be a useful material for the automotive and other industries. Fourier transform infrared (FTIR) spectroscopy was used to analyze the modified fibers and the resulting SMCs, and some silica-lignocellulosic bonding was observed. The water absorption of composites decreased as the loading of the silane reagent increased. The MOR and MOE mechanical properties of the SMCs also initially improved as the silane reagent levels increased from 0 (untreated) to 10% silane, but at levels above 10% VTEMS no further enhancement in the mechanical properties was obtained.
104

Contribution à l'étude des silanes absorbés sur le mica

Caron, Serge 12 December 2018 (has links)
"Ce Mémoire présente les études que nous avons effectué sur la nature d’organosilanes adsorbés sur le mica. Nous avons d’abord cherché à déterminer par quel processus les organosilanes établissent des liaisons covalentes avec le mica qui ne possède pas intrinsèquement à sa surface les groupements hydroxyle nécessaires. Ainsi, nous avons observé que le mica adsorbe, dans le milieu réactionnel aqueux, des ions hydronium (ou hydrogène) en libérant des ions potassium. Nous croyons que l’adsorption de ces ions peut entraîner la création de groupements hydroxyle intermédiaires qui peuvent, par la suite, réagir avec les silanes. Ce caractère basique du mica est une des causes de l’orientation normale des molécules de silane à sa surface. Le mica n’adsorbe pas les organosilanes de la même façon que le gel de silice Cab-O-Sil qui a une surface hydroxylée. Ce dernier n’adsorbe qu’une monocouche de silane qui est fortement retenue à la surface, et les molécules y sont dans une position parallèle. Nous attribuons cette différence de comportement entre le mica et le Cab-O-Sil au caractère acido-basique propre à chacune des deux surfaces; le mica a plus d’affinité avec les groupements silanol des organosilanes que le Cab-O-Sil qui a, de son côté, plus d’affinité avec les groupements ammonium. Nous avons aussi cherché à déterminer la structure des différentes monocouches des silane adsorbées sur le mica. A cause de la nature floconneuse des échantillons, la spectroscopie infrarouge à transformée de Fourier en transmission, en réflexion totale atténuée et en réflectance diffuse s’est avérée peu efficace. Pour sa part, la spectroscopie ESCA a permis de démontrer que les aminosilanes adsorbés sur le mica possèdent des groupements amine libres et protonés. La variation dans la proportion relative de ces deux types de groupements entraîne probablement une variation de l’énergie de surface du mica recouvert de silane. D’un autre côté, la spectroscopie ESCA n ’a permis de détecter qu’une seule monocouche de silane. Nous avons conséquemment émis l’hypothèse qu’une certaine quantité de silane peut être adsorbée à l’intérieur des cristaux de mica. Enfin, nous avons remis en question le modèle de Favis et coll. (J. Appl. Polym. Sc., 28, 1235, 1983) concernant l’orientation des mono­ couches d’organosilanes sur le mica. En effet, ces auteurs ont proposé que les molécules de monocouches successives ont des orientations opposées; par exemple, selon ce modèle, la deuxième monocouche du silane CVBS doit présenter une surface hydrophile composée de groupements silanol. Or, nous avons observé que cette deuxième monocouche est hydrophobe, ce qui est en contradiction avec les prédictions du modèle. Nous attribuons alors la variation, observée par Velazquez (Thèse de maîtrise, Université Laval, 1985), de l’énergie de surface avec le nombre de monocouches de silane adsorbé sur le mica à une variation de la quantité de groupements amine et ammonium, telle qu’observée en spectroscopie ESCA." / Québec Université Laval, Bibliothèque 2018
105

The development of a continuous process for the production of phenyltrichlorosilane from the vapor phase reaction of benzene and silicon tetrachloride

Brooks, John Granville January 1949 (has links)
M.S.
106

Mechanisms of Action of Silane-Substituted Anti-Cancer Imidazotetrazines

Summers, H.S., Bradshaw, T.D., Stevens, M.F.G., Wheelhouse, Richard T. January 2017 (has links)
Yes / Silane-substituted imidazotetrazines 1,2 were investigated for their activity as anticancer prodrugs related to temozolomide (TMZ). The TMS-derivative 1 showed an activity profile against TMZ susceptible and resistant cell lines very similar to TMZ; in contrast, the SEM-derivative 2 showed activity irrespective of MGMT expression or MMR deficiency (Table). Probing the prodrug activation mechanism by NMR kinetic studies determined that the TMS compound 1 follows a reaction pathway and time-course very similar to temozolomide. 1H-NMR spectra of the reaction mixture showed considerable incorporation of deuterium into the final alkylation products of the reaction (methanol and methyl phosphate) as had previously been shown for temozolomide (Wheelhouse, R.T., et al. Chem. Commun. 1993, 15, 1177–1178). The SEM-derivative 2 reacted more rapidly than TMZ or TMS-derivative 1. Somewhat surprisingly, the silane remained intact throughout the experiment and the observed reaction was the hydrolysis of the imidazo-tetrazine to ultimately release formaldehyde hydrate and 2-TMS-ethanol. In conclusion, TMS-derivative 1 is a diazomethane precursor with prodrug activation mechanism, kinetics and anti-cancer activity in vitro similar to TMZ. In contrast, the SEM derivative 2 was more rapidly hydrolysed, a precursor of 2-TMS-ethanol and had activity in vitro different from TMZ. 2-TMS-ethanol was previously reported as a non-toxic compound in mice (Voronkov, M.G., et al. Dokl. Akad. Nauk SSSR 1976, 229, 1011–1013) and is known as a substrate for alcohol dehydrogenase (Zong, M.-H., et al. Appl. Microbiol. Biotechnol. 1991, 36, 40–43) and as a modest inhibitor of acetylcholinesterase (Aberman, A., et al. Biochim. Biophys. Acta 1984, 791, 278–280; Cohen, S.G., et al. J. Med. Chem. 1985, 28, 1309–1313).
107

Mechanistic Study of Silane Assisted Rubber to Brass Bonding and the Effect of Alkaline Pre Treatment of Aluminum 2024 T3 on Silane Performance

Nookala, RamaKrishna 21 July 2006 (has links)
No description available.
108

Atmospheric pressure plasma jet deposition of Si-based coupling films as surface preparation for structural adhesive bonding in the aircraft industry

Bringmann, Philipp 23 May 2016 (has links) (PDF)
Damages of metallic aircraft structures that occur during manufacturing, assembly and in service require local repair. Especially with current service-life extensions of ageing aircraft fleets, the importance of such repair methods is increasing. Typically, the repair of smaller damages on aluminium fuselage or wing skins is done by riveting a patch onto the flawed structure. However, the use of rivets reduces the strength of the structure and promotes fatigue. Joining the patch by adhesive bonding would not only offer more homogenous load distribution and weight savings, but even an increase of structural integrity. Metal adhesive bonding is commonly used in aeronautics, but requires elaborated surface treatments of the adherends, employing hazardous chemicals like chromates, due to the high durability demands. Furthermore, these treatments are usually tank processes that are not suitable for local repairs. Hence, there is a strong need for locally applicable surface preparation methods that allow safe and reliable adhesive bonding of primary aircraft structures. The aim of this thesis is to assess the – still emerging – method of atmospheric pressure plasma deposition of silicon (Si) containing compounds concerning its suitability as surface preparation for adhesive bonding of aluminium aerostructures. Atmospheric plasma deposition is not yet used in the aircraft industry, and the knowledge on functionality of this technology concerning bonding of aluminium parts is limited. Moreover, the durability requirements of the aircraft industry greatly exceed the standards in other industries. Hence, special attention is paid to a thorough analysis of the key characteristics of the deposited coupling films and their effectiveness in terms of adhesion promotion as well as joint durability under particularly hostile conditions. In order to do so, the altering mechanisms of the treated joints and the behaviour of the coupling films during accelerated ageing will be investigated in detail for the first time in this thesis. Furthermore, the influence of the aluminium surface pre-treatment (i.e. topography and oxide properties of the substrate) on the overall joint performance after coupling film deposition is thoroughly examined. Based on these findings, the surface preparation is optimised, and a process is developed to achieve maximal joint performance. As alternative local surface treatments prior to adhesive bonding, solution derived deposition of silane and sol-gel films have already been widely investigated and can be considered as reference, even though these techniques are rarely used in civil aeronautics. The knowledge on their effectiveness and capabilities in corrosive atmosphere is still very limited. Therefore, all analyses of degradation mechanisms are conducted for both plasma deposition and wet-chemical reference treatments to reveal the differences and communalities of the two Si-based coupling films. Physical and chemical analysis of the films, the oxides and the interfaces reveal differing, but interdependent failure mechanisms that are inhibited differently by the individual coupling films. Using the optimum deposition parameters, plasma films of only several nanometres in thickness significantly enlarge the corrosion resistance of bonded joints, reaching almost the level of anodising treatments with several micrometres thick oxides and strongly outperforming solution derived silane treatments. However, plasma film performance is found to be largely dependent on the precursor selection. With plasma deposition of 3-glycidoxypropyltrimethoxysilane, which has not been reported before, highest joint stability is achieved. Moreover, it is discovered that the properties of plasma and solution derived silane based films are complementary. It is shown that an optimised combined plasma and wet-chemical treatment process provides even superior resistance to bondline corrosion than state-of-the-art anodising techniques.
109

Etude de couches hybrides photopolymérisables de type vinyl éther silane : Application à la fabrication de composants optiques intégrés / Study of hybrid films based on vinyl ether silane : Applications to photonic devices fabrication

Yaacoub, Saly 29 October 2013 (has links)
Depuis plusieurs dizaines d'années, les matériaux hybrides organiques-inorganiques constituent une classe de matériaux particulièrement bien adaptée aux applications en optique intégrée. Le réseau minéral, élaboré par procédé sol-gel, confère au matériau la tenue mécanique. Quant au réseau organique, qui est réticulable par voie photochimique, il permet la formation des systèmes guidants. Des travaux antérieurs réalisés au sein de notre laboratoire ont montré le potentiel d'un matériau à base d'un précurseur hybride 2-(3,4 epoxycyclohexylethyltrimethoxysilane) (EETMOS) pour l'application en optique intégrée. Bien que la qualité des composants réalisés à 1,31µm se soit révélée satisfaisante, un problème subsiste : une trop forte atténuation à 1,55 µm. La transmission optique autour de ces longueurs d'ondes est limitée par la présence des groupements OH et CH aliphatiques.L'objectif principal de ce travail est de développer une nouvelle génération de matériaux hybrides avec une très grande réactivité et de diminuer la quantité de groupements impliqués dans l'atténuation. Nous avons choisi la fonction vinyl éther comme fonction organique grâce à sa grande réactivité par voie cationique en comparaison avec la fonction époxyde. Nous avons étudié la double fonctionnalité de polymérisation du nouveau matériau hybride à base d'un vinyl éther silane. En premier lieu, les réactions d'hydrolyse et de polycondensation du sol ont été suivies par la spectroscopie RMN liquide du Si-29 en fonction du temps, de la température et du pH de l'eau impliquée dans l'hydrolyse. Le but était d'obtenir le plus haut taux d'oligomère multifonctionnel possible et le minium de groupement OH. La photopolymérisation de type cationique de la fonction vinyl éther a ensuite été étudiée, en utilisant la spectroscopie d'absorption dans l'infrarouge moyen. En présence du photoamorceur diaryliodonium, la photopolymérisation a été étudiée en suivant l'évolution de la bande d'absorption de la double liaison vinyl éther avant et après irradiation. La photopolymérisation cationique est rapidement initiée dès le début de l'exposition aux UV, ce qui prouve la réactivité important de la fonction vinyl éther. En utilisant la spectroscopie d'absorption dans le proche infrarouge, les résultats montrent des niveaux d'atténuation très prometteurs pour l'utilisation de ce matériau en optique intégré à 1,31 et 1,55 µm. / In the last few years, organic-inorganic hybrid materials were particularly attractive for integrated optical circuits. Hybrid network could be prepared by the formation of inorganic and organic network simultaneously through sol-gel technique and photopolymerization process.A composition based on [2-(3, 4 epoxycyclohexylethyltrimethoxysilane)] has already allowed the fabrication of optical integrated devices. The organic polymerization is on a cationic way. Results show the contributions of OH and aliphatic CH groups to the attenuation in the third telecommunication window located at 1,55 µm.The main objective of this work is to remove this difficulty by developing a new generation of hybrid materials with a very high reactivity and low amount of groups involved in the attenuation. We have chosen vinyl ether function as an organic part because of their well known high polymerization rates via cationic way which are faster than the epoxide function and which lead to no OH groups generation and a very low aliphatic CH groups introduction.In this work, we study the dual functional structure of a new vinyl ether alkoxysilane hybrid precursor. Firstly, hydrolysis and polycondensation of vinyl ether based solution are followed by liquid and solid Si-NMR spectroscopy. The kinetic reaction is followed as a function of time, temperature and pH of the water involved in the hydrolysis, in order to obtain the highest reactive multifunctional oligomer and the lowest OH groups. Secondly, results of the cationic photopolymerization of vinyl ether- based monomers are also reported, using middle infrared spectroscopy. In the presence of diaryliodonium photoinitator, the photopolymerization is studied by monitoring the absorption band of vinyl ether double bond before and after irradiation. The cationic photopolymerization occurs rapidly upon UV-exposure and vinyl ether monomers proved to be very effective monomers. Using near infrared spectroscopy, results show promising attenuation for the use of this material in integrated optic at 1,31 µmand 1,55 µm.
110

Photoinduced n-alkylsilsesquioxane based hybrid films : peering into corrosion protection and self-assembly / Films hybrides n-alkylsilsesquioxane par voie sol-gel photoinduite : propriétés anti-corrosion et auto-assemblage

Ni, Lingli 23 November 2012 (has links)
Les composés hybrides organiques-inorganiques représentent une classe intéressante de matériaux dotés d'un très large éventail d'applications potentielles dans les revêtements protecteurs, les micro-optiques, conducteurs ioniques, membrane échangeuse de protons etc. Depuis le début des années 1990, le développement de la chimie sol-gel, dite «Chimie Douce», a donné naissance à une nouvelle ère de matériaux hybrides, où des conditions douces de synthèse ont permis un accès simplifié aux matériaux nanocomposites. Parmi les divers précurseurs sol-gel, des organoalkoxysilanes sont très attractifs en raison de leur stabilité, leur faible toxicité et de leur accessibilité. Mais l'insolubilité de ces précurseurs a jusqu'à présent limité leur utilisation dans un procédé sol-gel conventionnel.L'essentiel de la chimie détaillée dans cette thèse porte sur la formation de films hybrides à partir de n-alkylsilanes. Tout d'abord, la partie linéaire et alkyle hydrophobe peut fournir des propriétés barrières à la pénétration de l'eau et des ions, ce qui est un élément clé dans la protection contre la corrosion de substrats métalliques. Deuxièmement, les alkylsilanes possèdent la géométrie et la composition appropriée à un auto-assemblage pour générer des nanostructures périodiquement ordonnées. Récemment, la recherche menée dans le LPIM à Mulhouse démontré le potentiel d’une photopolymérisation inorganique sans solvant. Basée sur la photogénération de superacides par photolyse de sels d'onium qui sont photoamorceurs cationiques classiques, cette voie offre une chance pour étudier l’aptitude de film à base d’alkylsilanes pour la protection des métaux (Partie I) et l'assemblage supramoléculaire (Partie II). / Hybrid organic-inorganic materials have attracted tremendous attention due to their wide range of potential applications in protective coatings, micro-optics, ionic conductors, proton-exchange membrane and so on. Since the early 1990s, the development of sol-gel chemistry (“Chimie Douce”) has given birth to a new age of hybrid materials, where mild synthetic conditions allowed a simplified access to well dispersed and chemically designed nanocomposite materials. Among various sol-gel precursors, organo alkoxysilanes are very attractive because of their superior stability compared to other hybrid precursors, low toxicity and accessibility. However, their insolubility in polar solvents and water has so far limited their use in conventional classic hydrolytic sol-gel procedure.In this thesis, the combination of a UV-driven solvent-free sol-gel process simultaneously to organic photopolymerization has been introduced to form hybrid films based on simple n-alkylsilane building blocks. Based on the photogeneration of superacids under photolysis of onium salts that are conventional photoinitiators, this pathway offers a new chance to investigate alkylsilanes in metal corrosion protection (Part I) and supramolecular assembly (Part II). As the linear and hydrophobic alkyl moiety can provide barrier-properties to the penetration of water and ions, which is a key feature in the corrosion protection of metallic substrates, in part I, the effect of alkyl chain structure of the alkylsilanes as well as their proportions on the corrosion resistance properties has been studied by Salt spray tests and Electron impendence spectroscopy. Furthermore, an effort to correlate the corrosion resistance and coating structure was made as a range of characterization techniques have been implemented (Real time FTIR, 29Si solid state NMR and contact angle measurement). Secondly, alkylsilanes have the proper geometry and composition to self-assemble and generate periodically ordered nanostructures. In part II, the influence on the mesostructure, alkyl chain packing arrangement and its conformational order, which come from alkyl chain length of the silane precursors and the experimental conditions (light intensity, temperature and humidity), has been investigated depending on various characterization techniques (X ray diffraction, microscope, solid state NMR, RT-FTIR). As an application example, a patterned 3D multilayer crystalline organosilica film has been amplified via a facile photopattrerning pathway.

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