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1
Kothalawala, Kothalawalage Nuwan. "Nanoporous high surface area silicas with chelating groups for heavy metal ion adsorption from aqueous solution /." View online, 2010. http://repository.eiu.edu/theses/docs/32211131524422.pdf.
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Hondow, Nicole S. "The synthesis of new heterogeneous Fischer-Tropsch catalysts : the incorporation of metal aggregates in mesoporous silicas." University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0083.
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Transition metals have been extensively studied as catalysts, and certain metals are known to be highly selective and active for certain processes. It is possible to use metal clusters as models for reactions occurring at metal surfaces, but it is often found that in practical applications these complexes are unstable and break down. It is possible to support or stabilise a metal species on, or in, an inorganic framework, making heterogeneous catalysts. A study of metal cluster chemistry with mixed-donor phosphine ligands was conducted, with several new ruthenium complexes synthesised. The chemistry of metal-sulfur interactions is applicable to the removal of sulfur from crude oil, and in an investigation to this chemistry, the bifunctional ligand HSCH2CH2PPhH was added to ruthenium clusters (Chapter 2). The addition of this sulfur-phosphine ligand to the cluster [Ru3([mu]-dppm)(CO)10] produced the carbonyl substituted cluster [Ru3([mu]-dppm)(H)(CO)7(SCH2CH2PPhH)] and the bridged complex [Ru3([mu]-dppm)(H)(CO)8(SCH2CH2PPhH)Ru3([mu]-dppm)(CO)9], as well as recovery of the starting material. Further reactions with this ligand were examined with [Ru3(CO)12] and other complexes were synthesised with different clusters and ligands (Chapter 2). The M41S materials, MCM-41 and MCM-48, are well ordered porous materials with high surface areas (Chapter 3). The incorporation of three different types of metal species, metallosurfactants, metal clusters and nanoparticles, into these materials was examined in an attempt to make heterogeneous catalysts for the Fischer-Tropsch process. The success of this was studied using characterisation techniques such as powder X-ray diffraction, transmission electron microscopy and BET surface area measurements. Metallosurfactants containing either copper or cobalt were added directly to the synthesis of the porous materials in an attempt to incorporate the metals into the framework structure of the porous silica (Chapter 3). This resulted in well ordered iv porous materials, but the successful incorporation of the metal species was found to be dependent on several factors. Organometallic clusters containing metals such as copper, iron and ruthenium, with supporting carbonyl ligands, were added post-synthesis to MCM-41 and MCM-48 (Chapter 4). Various reaction conditions were examined in attempts to ensure small particle formation. The optimum incorporation of nanoparticles containing iron and platinum was found to occur when a suspension of pre-made and purified nanoparticles was added post-synthesis to the M41S materials (Chapter 4). These materials resulted in porous silicas with well dispersed, small metal particles. The optimum conditions for the calcination of these new materials were determined, in an attempt to remove the ligands and stabilisers and retain the small metal particle size (Chapter 5). Testing for the Fischer-Tropsch process was conducted in a fixed bed reactor through which a flow of synthesis gas containing carbon monoxide and hydrogen could pass over the material (Chapter 5). Analysis by gas chromatography showed that the major product produced by all materials tested was methane, but other hydrocarbons were produced in small amounts, including hexane.
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Lazaro, A., J. W. Geus, and H. J. H. Brouwers. "Influence of the Production Process Conditions on the Specific Surface Area of Olivine Nano-Silicas." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34893.
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The production of nano-silica by the olivine route is a cheaper and greener method than the commercial methods (neutralization of sodium silicate solutions and the flame hydrolysis) because of the low cost
of raw materials and the low energy requirements. The produced olivine nano-silica has a specific surface
area between 100-400 m2/g and primary particles between 10 to 25 nm (agglomerated in clusters). The process conditions and the ripening process influence the properties of nano-silica in the following ways i) the
cleaner the nano-silica is the higher the specific surface area is; ii) the higher the filtration pressure is the
higher the surface area is (unless the pressure is so high that the voids of the material collapse reducing
drastically the SSA); iii) the ripening process diminishes the specific surface of nano-silica by two thirds
and could be even further reduced. Thus, modifying the process conditions and/or adding an Ostwald ripening process, nano-silicas with different specific surface areas can be synthesized.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34893
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Zhou, Wen-Juan. "Polyamine and Schiff base metal complexes incorporated in mesostructured templated porous silicas : tentative application in selective oxidation." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2009. http://tel.archives-ouvertes.fr/tel-00533599.
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De nouveaux matériaux ont été conçus à partir de matériaux hybrides organique-inorganiques mésoporeux renfermant des complexes de Cu(II). Ils ont été mis en œuvre comme catalyseurs dans des réactions d'oxydation sélective. La localisation des sites du métal a été contrôlée en utilisant trois ligands synthétiques le type organosilane et deux stratégies différentes, c. àd.,une synthèse dite "one-pot", et un greffage post-synthètique. Les organosilanes ont été le N-(2-aminoéthyl)-3-aminopropyltriméthoxysilane (L1), le N-propylamine-salicylaldimine-triméthoxy-silane (L2) et le de N-(salicylaldimine)- (N'-propyltriméthoxylsilane)-diéthylènetriamine (L3). En outre, l'ion Ni(II) a été utilisé comme sonde structurale. Selon la synthèse "one-pot", les complexes Ni(II)-L1, Cu(II)-L1 et Cu(II)-L2 ont été co-condensés avec du silicate de sodium en présence d'un tensoactif, le cé-tyltriméthylammonium tosylate. Ce dernier avait le rôle de gabarit structurant pour la cons-truction d'organosilices mésoporeuses périodiques (PMOs), de structure bien ordonnée de type MCM-41. Ces matériaux ont ensuite été soumis à des traitements mis au point pour pré-server la structure mésoporeuse utilisant un mélange de chlorotriméthylsilane et hexaméthyl-disilazane ou une quantité appropriée de HCl aqueux (lavage) pour extraire le tensio-actif. Dans les greffages post synthétiques, les complexes Ni(II)-L1, Cu(II)-L1 ou Cu(II)-L3 ont été liés de façon covalent à la surface de silice mésoporeuse préformée selon une distribution uniforme mettant en œuvre une technique dite de pochoir moléculaire. Une caractérisation multitechnique approfondie fut mener pour vérifier la structure et la morphologie du matériau et pour déterminer le site de coordination du métal (XRD, TEM, isothermes d'adsorp-tion-désorption d'azote, analyse élémentaire, ATG, spectroscopies DRUV, FT-IR et RPE). De plus, l'accessibilité chimique du site métallique et le relargage du métal ont été testés en utili-sant 1) l'isothiocyanate (SCN-) comme ligand sonde, 2) l' échange des ions Ni(II) par les ions Cu (II) d'ions ou encore 3) la résistance à la lixiviation acide. Outre les sites métalliques des canaux obtenus par greffage et trés ressemblant à des sites "en solution", deux autres sites ont été mis en évidence. Ils sont tous les deux situés dans les murs des pores. L'un non accessible, est appelé “site enlisé”, l'autre est “site émergenant”. L'activité catalytique en hydroxylation du phénol par le peroxyde d'hydrogène et oxydation du catéchol par le dioxygène dépend de la localisation du métal. Les complexes Cu(II)-L3 greffés présentent les meilleures activités catalytiques et fonctionnent dans l'eau. La conversion et la sélectivité en produits valorisables comme le catéchol et l'hydroquinone, ont été étudiées en fonction du temps, de la température, du pH et du rapport substrat /oxydant. Enfin, le recyclage du catalyseur a également été étu-dié.
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Zhou, Wen-Juan. "Polyamine and Schiff base metal complexes incorporated in mesostructured templated porous silicas : tentative application in selective oxidation." Phd thesis, Lyon, École normale supérieure (sciences), 2009. http://www.theses.fr/2009ENSL0527.
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De nouveaux matériaux ont été conçus à partir des matériaux hybrides organique-inorganiques mésoporeux renfermant des complexes de Cu(II). Ils ont été mis en œuvre comme catalyseurs dans des réactions d'oxydation sélective. La localisation des sites du métal a été contrôlée en utilisant trois ligands synthétiques le type organosilane et deux stratégies différentes, c'est-à-dire, une synthèse dite « one-pot », et un greffage post-synthètique. Les organosilanes ont été le N-(2-aminoéthyl)-3-aminopropyltriméthoxysilane (L1), le N-propylamine-salicylaldimine-triméthoxy-silane (L2) et le de N-(salicylaldimine)- (N'-propyltriméthoxylsilane)- diéthylènetriamine (L3). En outre, l'ion Ni(II) a été utilisé comme sonde structurale. Selon la synthèse « one-pot », les complexes Ni(II)-L1, Cu(II)-L1 et Cu(II)-L2 ont été co-condensés avec du silicate de sodium en présence d'un tensoactif, le cétyltriméthylammonium tosylate. Ce dernier avait le rôle de gabarit structurant pour la construction d'organosilices mésoporeuses périodiques (PMOs), de structure bien ordonnée de type MCM-41. Ces matériaux ont ensuite été soumis à des traitements mis au point pour préserver la structure mésoporeuse utilisant un mélange de chlorotriméthylsilane et hexaméthyldisilazane ou une quantité approprié de HCI aqueux (lavage) pour extraire le tensio-actif. Dans les greffages post synthétiques, les complexes Ni(II)-L1, Cu(II)-L1 ou Cu(II)-L3 ont été liés de façon covalent à la surface de silice mésoporeuse préformée selon une distribution uniforme mettant en œuvre une technique dite de pochoir moléculaire. Une caractérisation multitechnique approfondie fut mener pour vérifier la structure et la morphologie du matériau et pour déterminer le site de coordination du métal (XRD, TEM, isothermes d'adsorption-désorption d'azote, analyse élémentaire, ATG, spectroscopies DRUV, FT-IR et RPE). De plus, l'accessibilité chimique du site métallique et le relargage du métal ont été testés en utilisant 1) l'isothiocyanate (SCN-) comme ligand sonde, 2) l'échange des ions Ni(II) par les ions Cu(II) d'ions ou encore 3) la résistance à la lixiviation acide. Outre les sites métalliques des canaux obtenus par greffage et très ressemblant à des sites « en solution », deux autres sites ont été mis en évidence. Ils sont tous les deux situés dans les murs des pores. L'un non accessible, est appelé « site enlisé », l'autre est « site émergenant ». L'activité catalytique en hydroxylation du phénol par le peroxyde d'hydrogène et oxydation du catéchol par le dioxygène dépend de la localisation du métal. Les complexes Cu(II)-L3 greffés présentent les meilleures activités catalytiques et fonctionnent dans l'eau. La conversion et la sélectivité en produits valorisables comme le catéchol et l'hydroquinone, ont été étudiées en fonction du temps, de la température, du pH et du rapport substrat/oxydant. Enfin, le recyclage du catalyseur a également été étudié<br>Novel materials were designed from hybrid organic-inorganic silica-based mesoporous materials containing Cu(II) complexes and were applied in selective oxidation reactions. The localization of the metal sites xas controlled using three different organosilane-ligands and two different synthétic routes, either the one-pot synthésis or the post-synthésis grafting. The Organosilanes were :N-(2-aminoéthyl)-3-aminopropyltriméthoxysilane (L1), N-salicylaldimine-propylamine-triméthoxysilane (L2) and N-(salicylaldimine) -(N'-propyltrimethoxyl silane)- diethylenetriamine, (L3). In addition, Ni(II) ion was used as structural probe. The Ni(II)-L1, Cu(II)-L1 and Cu(II)-L2 complexes were co-condensed with sodium silicate using the one-pot synthetic route in the presence of cetyltriméthylammonium tosylate as templating agent to built well-ordered periodix mesoporous organosilicas (PMOs) of MCM-41 type. The as-made materials were submitted to treatments using a mixture of chlorotriméthylsilane and hexamethyldisilazane or an appropriate amount of HCI washing to extract template and maintain the mesoporous structure. The Ni(II)-L1, Cu(II)-L1 or Cu(II)-L3 complexes have been also grafted in the performed mesoporous silica and evenly distributed using the a molecular stencil patterning technique. A multiple technique approach has been applied to thoroughly investigate the structure and morphology of the material as well as the coordination of the metal sites, using XRD, TEM, N2 sorption isotherms, elemental analysis, TGA, DRUV, FT-IR and EPR spectroscopies. In addition, the chemical accessibility and the leaching properties of the metal sites were tested using isothiocyanate (SCN-) as a ligand probe, metal displacemement of Ni(II) by Cu(II) ions or resistance to acidic leaching. Apart from the know channel species obtained from grafting that are solution-like, two different frame-work species were identified from their structural and chemical properties : the accessible and non-accessible ones, named « embedded » and « showing on » sites, respectively. The catalytic activity in phenol hydroxylation using hydrogen peroxide as oxiant and catechol oxidation reactions using dioxygen as oxidant depends on the metal location. Te grafted Cu(II)-L3 complex exhibited the best catalytic activities and was working in water solutions. The con- version and selectivity into valuable products, catechol and hydroquinone, were investigated in function of time, temperature, pH and substrate to oxidant ration. Catalyst recycling has been also investigated
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Fernandes, Leandro. "Desenvolvimento e controle da microestrutura de cerâmicas porosas à base de mulita para aplicações em isolamento térmico de alta temperatura." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-05092018-084646/.
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Mulita é um aluminosilicato com aplicações em sistemas de altas temperaturas como filtração de gases, elemento estrutural, suporte catalítico e isolante térmico. Na natureza, a mulita é pouco abundante e por este motivo é sintetizada via reação do estado sólido entre precursores contendo alumina e sílica. Nesta tese foi estudado o efeito de diferentes tipos de sílicas amorfas sintéticas (sílica precipitada, microssílica, sílica da casca de arroz e sílica da cinza da casca de arroz). Resultados obtidos demonstraram que quanto maior for a porosidade interna das partículas maior é o ganho em módulo de ruptura em flexão. No caso da microssílica, a presença de contaminantes foi determinante para obter a formação de fase vítrea viscosa, obtendo um material com baixa porosidade e elevado módulo elástico e de ruptura em flexão. Com o objetivo de aumentar a porosidade das estruturas de mulita, utilizou-se sílica com elevado tamanho médio de partículas (> 5 μm) e com (> 99%). Os resultados demonstraram que a porosidade obteve valor entre 20 a 30%, com ganho em módulo de ruptura em flexão (72 MPa). Apesar dessa baixa porosidade, a vantagem é que estes poros são revestidos pela sílica o que confere controle da microestrutura e estabilidade frente a sinterização, além de ser reprodutível. Diferentes proporções molares de sílica foram estudadas (de 3A-0S até 3A-2S), dois diferentes tamanhos de partículas de alumina calcinada, uma fina e outra grossa. Os resultados mostraram que utilizando alumina grossa é possível obter uma porosidade maior contudo com menores propriedades mecânicas. Diferentemente dos resultados mostrados em outros trabalhos, verificou-se que uma pequena quantidade de sílica (0,25% em mol ou 3A-0,25S), já prejudica a densificação da alumina, tal efeito foi explicado pelo concentração de fase viscosa nos contornos de grão que dificulta a densificação das partículas de alumina. Utilizando hidróxido de alumínio, e fazendo a sua pré-sinterização foi possível obter estruturas de mulita com porosidade de 55%, e com módulo de ruptura em flexão de 16 MPa e com retração linear térmica de 5%, desta forma, aliou alta porosidade com boas propriedades mecânicas, sem necessidade de uso de agentes porogênicos ou geradores de vapores tóxicos, e tecnologicamente formou um produto com grande potencial para uso em isolamento térmico primário.<br>Mullite is an aluminosilicate with applications in high-temperature systems such as gas filtration, structural element, catalytic support and thermal insulation. In nature, mullite is not abundant and is therefore synthesized via the solid-state reaction between precursors containing alumina and silica. In this thesis, the effect of different types of synthetic amorphous silicas (precipitated silica, microsilica, silica from rice husk and silica from rice husk ash) was studied. Results obtained showed that the larger the internal porosity of the particles, the greater the gain in modulus of rupture in flexion. In the case of the microsilica, the presence of contaminants was determinant to obtain the formation of viscous glassy phase, obtaining a material with low porosity and high elastic modulus and rupture in flexion. In order to increase the porosity of the mullite structures, high particle size (> 5 μm) and (> 99%) silica were used. The results showed that the porosity obtained a value between 20 to 30%, with the gain in modulus of rupture in flexion (72 MPa). In spite of this low porosity, the advantage is that these pores are coated by silica, which gives control of the microstructure and stability to sintering, in addition to being reproducible. Different molar ratios of silica were studied (from 3A-0S to 3A-2S), two different particle sizes of calcined alumina, one fine and one coarse. The results showed that using coarse alumina it is possible to obtain a higher porosity with lower mechanical properties. Differently, from the results shown in other works, it was verified that a small amount of silica (0.25 mol% or 3A-0.25 S), already affects the densification of alumina, this effect was explained by the concentration of viscous phase in the contours of grain which hinders the densification of the alumina particles. Using aluminum hydroxide, it was possible to obtain mullite structures with 55% porosity and with a modulus of rupture in flexion of 16 MPa and linear thermal retraction of 5%, thus allying high porosity with good mechanical properties, no need for porogenic agents or toxic vapors, and technologically formed a product with great potential for use in primary thermal insulation.
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Maouacine, Koceila. "Matériaux hybrides poreux silice/polymère comme électrolytes pour batterie lithium-ion tout solide." Electronic Thesis or Diss., Aix-Marseille, 2023. http://www.theses.fr/2023AIXM0024.
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La conception de batteries lithium-ion utilisant un électrolyte solide est actuellement l’une des voies les plus étudiées pour s’affranchir des problèmes de sécurité lié à ces dispositifs. Dans ces travaux de thèse, nous proposons une nouvelle approche d'élaboration d'un électrolyte hybride poreux silice/polymère, contenant une fraction massique plus élevée de silice mésoporeuse que de polymère. Deux morphologies de matériaux hybrides de silice ont été étudiées : sous forme de poudres compressées (pastilles) et sous forme de films minces. Dans la première partie du travail, une poudre de silice hybride a été synthétisée puis calcinée pour libérer la porosité. La silice mésoporeuse a, ensuite, été fonctionnalisée par imprégnation en solution avec différents polymères de type PEG de faible poids moléculaire puis, par un sel de lithium, le LiTFSI. Les poudres hybrides ont été compressées sous forme de pastilles, présentant une porosité inter- et intraparticulaire. Il a été montré que, les pastilles hybrides présentent des propriétés de conductivité ionique prometteuse lorsque les porosités inter et intraparticulaires sont remplies par le complexe PEG-LiTFSI pour PEG de faible masse molaire (300-600 g/mol). Dans la seconde partie, des films de silice mésoporeuse ont été déposés sur une électrode de carbone vitreux en utilisant une électrode à disque rotatif (RDE). Après avoir caractérisé ces films du point des propriétés texturales et de la microstructure, ces derniers ont été fonctionnalisés par le complexe PEG-LiTFSI via un procédé d’imprégnation et l’étude préliminaire de leur conductivité ionique a été réalisée<br>The design of lithium-ion batteries using a solid electrolyte is currently one of the most studied ways to overcome safety problem of these devices. In this thesis work, we propose a new approach to develop a porous silica/polymer hybrid electrolyte, containing a higher weight fraction of mesoporous silica than polymer. Two morphologies of silica hybrid materials were studied: as compressed powders (pellets) and as thin films. In the first part of the work, a hybrid silica powder was synthesized and then calcined to liberate the porosity. The mesoporous silica was then functionalized with different polymers of PEG of low molecular weight then by a simple solution impregnation. The hybrid powders were shaped as pellets, presenting inter- and intra-particle porosity. It was shown that the hybrid pellets present promising ionic conductivity properties when the inter- and intraparticle porosities are filled with the PEG-LiTFSI complex for PEG of low molar mass (300-600 g/mol). In the second part, mesoporous silica films were deposited on a glassy carbon electrode using a rotating disc electrode (RDE). After the characterization of these films from a textural properties and a microstructure point of view, they were functionalized by the PEG-LiTFSI complex via an impregnation process and the preliminary study of their ionic conductivity was performed
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Menard, Samuel. "Périphérie triac à base de silicum poreux." Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4022/document.
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Ces travaux de thèse portent sur le développement d’une périphérie innovante de TRIAC exploitant le caractère semiisolant du silicium poreux (PS). L’intégration de caissons PS type P à partir des profils de dopage du TRIAC est en effet accessible. Une revue des propriétés électriques du PS type P réalisée à partir de nos propres échantillons méso voire micro-poreux a donc été entreprise. Des mesures de capacités et des relevés I-V ont ainsi permis de déterminer l’évolution de la constante diélectrique relative du PS ainsi que sa résistivité en fonction de la porosité. Plus cette dernière est élevée et plus les propriétés diélectriques du PS se rapprochent de celles d’un isolant. L’analyse des résultats a également permis de clarifier les mécanismes de transport des porteurs au sein de la couche de PS. Des prototypes de TRIACs avec une terminaison de jonction à base de PS ont ensuite été conçus, fabriqués et étudiés. La localisation du PS et la gestion des contraintes mécaniques résultant de la formation du PS sont apparus comme les principaux verrous technologiques à surmonter. Des solutions ont été proposées, néanmoins les tenues en blocage atteintes se sont avérées insuffisantes. Des courants de fuite supérieurs à la dizaine de milliampères ont en effet été mesurés et ce pour des tensions de polarisation de l’ordre de 100 V. La géométrie des caissons PS et/ou la présence de charges fixes à l’interface PS / Silicium sont jugées responsables des résultats. Enfin, en s’appuyant sur un modèle macroscopique du PS, une nouvelle structure plus optimisée a été suggérée<br>This PhD thesis deals with the development of a novel TRIAC periphery, exploiting the semi-insulating nature of porous silicon (PS). It is namely accessible to integrate P type PS wells through the doping profiles encountered in the TRIAC. Thus, a review of the P type PS electrical properties was achieved through dedicated samples. In this context, capacitance measurements and I-V plots were used to determine the evolution of the PS relative dielectric constant and its resistivity with the porosity. Higher the latter is, more insulating the PS is. By analyzing all the results, it was also possible to clarify the carrier transport mechanisms in the PS. Some TRIAC prototypes with a PS based junction termination were then designed, processed and studied. The stress coming from the PS formation and the PS masking were the main technological steps to solve. First solutions were proposed, nevertheless insufficient blocking performances were reached. Leakage currents higher than 10 mA were demonstrated while the bias voltage was only 100 V. The presence of fixed charges at the PS / Silicon interface and/or the geometry of the PS wells may explain these results. Finally, with the help of a macroscopic PS model, a more optimized structure was proposed
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Raachini, Rita. "Nanoparticles of Ni strongly embedded in porous silica : towards the design of efficient catalysts for lignin hydrogenolysis." Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS540.
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Les phénols peuvent être obtenus à partir de la lignine plutôt que du pétrole. Notre principale préoccupation était d’améliorer la conversion de la lignine par hydrogénolyse, tout en limitant l’hydrogénation des phénols produits en utilisant des catalyseurs à base de Ni au lieu de métaux nobles. Des matériaux constitués de Ni hautement dispersés sur la silice ont été synthétisés de différentes matières, caractérisés avant et après réduction sous H2, puis testés dans l'hydrogénolyse de trois composés comportant des liaisons C-OAryl, comme dans liaison β-O-4 de la lignine, en utilisant l’isopropanol comme solvant donneur d’hydrogène. Dans une première série de matériaux, le Ni a été introduit par imprégnation d’Aerosil-380 en présence d’ammoniaque et des matériaux similaires ont été préparés avec le Rh. Le catalyseur à base de Rh favorise la formation de phénol mais entraine un lent clivage, le catalyseur le plus actif, mais le moins sélectif pour le phénol s’est avéré initialement être à base de Ni. La productivité du phénol a été réalisée en réduisant le catalyseur à base de Ni à haute température. Contrairement au Ni, Rh-phyllosilicates n’ont pas été détectées, ceci peut être relié au contre-ion dans le précurseur et au métal lui-même. Deuxièmement, la conception de monolithes mésoporeux à base de nickel hautement dispersés avec différentes structures de pores (Sx) (structures de pores vermiculaire, hexagonale ou cubique) par le biais d’une méthode sol-gel. Des différences ont été observées entre les formes réduites de NiII@Sx, avec de meilleurs rendements avec la structure cubique. Les solides obtenus ont été comparés à deux matériaux obtenus par imprégnation de la silice aérosil ou d’un monolithe de silice hexagonale par du nickel en présence d’ammoniaque afin d’étudier l’effet du support et de la méthode d’incorporation. Le meilleur catalyseur vis-à-vis la sélectivité du phénol, évitant son hydrogénation en cyclohexanol était la silice aérosil à base de Ni. Enfin, l’effet de l’ajout d’un second métal avec Ni (le Co ou Fe) par trois méthodes, une imprégnation de Co ou Fe sur le monolithe Ni@SBA-15, une introduction directe des deux métaux par synthèse one-pot ou une co-imprégnation des deux métaux Ni et Co ou Fe sur un monolithe hexagonale vierge. L’incorporation de Co ou Fe par la méthode des deux solvants sur le monolithe type Ni@SBA-15 a conduit à une meilleure activité catalytique en termes de sélectivité vis-à-vis du phénol. En fait, toutes les espèces actives n’ont pas été suffisamment réduites et il serait intéressant d’augmenter la température de réduction de ces solides et d’optimiser les conditions de réaction<br>Phenols may be obtained from lignin instead of petroleum. Here, improving lignin conversion by hydrogenolysis, while limiting side hydrogenation of produced phenols using nickel-based catalysts instead of noble metals, was our main concern. Porous materials made of highly dispersed nickel onto silica were synthesized by different ways, characterized before and after reduction under H2, then tested in the hydrogenolysis of three compounds bearing C-OAr bonds, as in the β-O-4 linkage of lignin, using isopropanol as H-donor. In a first series of materials, Ni was introduced by the impregnation of Aerosil-380 in the presence of ammonia and similar materials were prepared with Rh. The latter favored phenol formation but resulted in much slower C-OAr cleavage. In fact, the most active catalyst was found to be the Ni-based one, affording high phenol productivity could be reached by reducing the Ni-based catalyst at high temperature. Unlike Ni, no Rh-phyllosilicates were detected, this was related to the counterion in the precursor and the metal itself. Secondly, designing highly dispersed nickel-based mesoporous monoliths with different pore structures (Sx) (wormlike, hexagonal or cubic pore structures) through an original sol-gel method. Divergences were observed between the reduced forms of NiII@Sx, with better yields with the more open cubic structure. The resulting solids were compared to two materials obtained by the impregnation of either aerosil silica or a hexagonal silica monolith with Ni(II) in the presence of ammonia in order to study the effect of the support and the incorporation method. the best catalyst with respect to phenol selectivity, avoiding its hydrogenation to cyclohexanol, was Ni-based aerosil silica. Lastly, studying the effect of adding a second metal with Ni (Co or Fe) by three methods, impregnation of Co or Fe on Ni@SBA-15 like monolith, a direct one-pot synthesis introduction or co-impregnation of both metals Ni and Co or Fe on blank SBA-15 like monolith. The incorporation method of metals is the most critical parameter. Incorporation Co or Fe by “two-solvents” method on Ni@SBA-15 like monolith led to the best catalytic activity in terms of selectivity towards phenol. In fact, not all active species were sufficiently reduced and it would be interesting to increase the reduction temperature of these solids and to optimize the reaction conditions
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Azevedo, Raquel Cristina de Souza. "Síntese e caracterização de um sistema multifuncional SBA-16/Nanopartículas magnéticas/gel polimérico para bioaplicações." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2014. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=316.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>A combinação do material mesoporoso SBA-16 com o gel polimérico poli(N-isopropilacrilamida) contendo nanopartículas magnéticas pode conduzir à formação de um material híbrido interessante para aplicação em magnetohipertemia e liberação controlada de fármacos. Neste trabalho, foi explorada a estratégia de síntese de um sistema multifuncional, constituído por SBA-16/Fe3O4/P(N-iPAAm) com o objetivo de avaliar sua potencialidade de geração de calor a partir da magnetita e sua contribuição nos estudos de liberação controlada de fármacos. A caracterização dos materiais foi feita por Microscopia Eletrônica de Varredura (MEV), Microscopia Eletrônica de Transmissão (MET), Adsorção de Nitrogênio, Espalhamento de Raios X a Baixos Ângulos (SAXS), Análise Termogravimétrica (TG), Análise Elementar (CHN), Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR), Difração de Raios X (DRX), Espectroscopia Mössbauer, Medidas Magnéticas e Espectroscopia de Fotoelétrons Excitados por Raios X (XPS). Através da análise dos resultados obtidos foi possível confirmar a formação do híbrido, e elucidar as propriedades físico-químicas, estruturais e magnéticas das amostras. Medidas das propriedades de geração de calor mostraram que o híbrido apresentou uma variação de temperatura (T) de 11 e 35C nas concentrações de 10 e de 20 mg/mL, respectivamente, no campo magnético alternado de 126 Oe; e apresentou uma variação de temperatura (T) de 32 e 39C nas concentrações de 10 e de 20 mg/mL, respectivamente, no campo magnético alternado de 168 Oe. Este resultado demonstrou que este sistema multifuncional apresenta potencial como agente de hipertermia para o tratamento do câncer. Por fim, foi feito o estudo da influência dessas nanopartículas magnéticas com a presença do gel na cinética de liberação do fármaco Doxorrubicina (DOX) sob condições in vitro. A liberação foi estudada na ausência e na presença de um campo magnético alternado de 126 Oe, que se constatou a influência do campo magnético no aumento da taxa de liberação da DOX. Este resultado demonstrou que a propriedade da magnetita de gerar calor aliada às propriedades do P(N-iPAAm) de transição de fases (contração) contribuiu para uma melhor taxa de liberação da DOX.<br>The combination of SBA-16 mesoporous materials with gel polymer poly (N-isopropylacrylamide) containing magnetic nanoparticles can lead to the formation of an interesting hybrid material for use in hybrid magnetic hyperthermia and controlled drug release. In this study, we explored the strategy of synthesis of a multifunctional system consisting of SBA-16/Fe3O4/P(N-iPAAm) in order to assess its potential for heat generation from magnetite and its contribution in the controlled drug release. The materials were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Nitrogen Adsorption, Small Angle X Ray Scattering (SAXS), Thermogravimetric Analysis (TG), Elemental Analysis (CHN), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), 57Fe Mössbauer spectroscopy, magnetic measures and X-Ray Photoeletron Spectroscopy (XPS). Through the analysis of the results it was possible to confirm the formation of the hybrid system, and elucidate the physicochemical, structural and magnetic properties of the samples. Measurements of the properties of heat generation showed that the hybrid presents a temperature variation (T) of 11 and 35C in concentrations of 10 and 20 mg/mL, respectively, in the alternating magnetic field of 126 Oe, and presents a temperature variation (T) 32 and 39C at concentrations of 10 and 20 mg/mL, respectively, in alternating magnetic field of 168 Oe. This result indicates that the multifunctional system shows great potential as a hyperthermia agent for cancer treatment. Finally, the study of the influence of these magnetic particles in the kinetics of release of the doxorubicin (DOX) was made in the presence of gel under in vitro conditions. The release was studied in the absence and in the presence of an alternating magnetic field of 126 Oe; it was found that the presence of magnetic field increased the release rate of DOX. This result demonstrated that the property of heat generate from magnetite combined with phase transition (contraction) properties of P(N-iPAAm) contributed to a better control of release of DOX from hybrid system.
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Mueller, Paul S. "Synthesis of silica based porous nanomaterials." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1368.
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Silica is one of the most abundant elements on the planet, has flexible bonding properties and generally excellent stability. Because of these properties, silica has been a vital component in technologies ranging from ancient glassware to modern supercomputers. Silica is able to form a wide range of materials both alone and as a component of larger material frameworks. Porous silica based nanomaterials are rapidly growing in importance because of their many applications in a wide variety of fields. This thesis focuses on the synthesis of silica based porous nanomaterials: nanocrystalline zeolites, mesoporous silica nanoparticles, and iron oxide core/shell nanocomposites. The synthetic conditions of these materials were varied in order to maximize efficiency, minimize environmental impact, and produce high quality material with far reaching potential applications. The materials were characterized by physicochemical techniques including Transmission Electron Microscopy, Dynamic Light Scattering, Powder X-Ray Diffraction, Solid State NMR, and Nitrogen Adsorption Isotherms. The materials were evaluated and conditions were controlled to produce high yields of quality nanomaterials and hypothesize methods for further synthetic control. The products will be used in studies involving nanoparticle toxicity, environmental remediation, and drug delivery.
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Karlsson, Linda. "Biomolecular interactions with porous silicon /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek804s.pdf.
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Wielgosz, R. I. "Electrochemical studies of porous silicon." Thesis, University of Bath, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296302.
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Boswell, Emily. "Field emission from porous silicon." Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:a4344196-7fc2-4713-b47b-85920b137759.
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Vacuum microelectronic (VME) devices are of interest for the development of flat-screen displays and microwave devices. In many cases, their operation depends on the field emission of electrons from micron-sized cathodes (semiconductor or metal), into a vacuum. Major challenges to be met before these devices can be fully exploited include obtaining - low operating voltages, high maximum emission currents, uniform emission characteristics, and long-term emission stability. The research in this thesis concerns the production of silicon field emitters and the improvement of their emission properties by the process of anodisation. Anodisation was carried out for short times, in order to form a very thin layer of porous silicon (PS) at the surface of both p and p<sup>+</sup>-type silicon emitters. The aim in doing this was to form a high density of asperities over the surface of the emitters. It was the intention that these asperities, rather than the "macroscopic" apex of the emitter, would control emission. This was the first work of its kind to be carried out. Transmission electron microscopy was used to characterise the morphology of p and p<sup>+</sup>-type silicon emitters before and after anodisation. Both the structure and arrangement of the surface fibrils, the thickness of the PS layers at the apex and nature of PS cross-sections were studied. The morphology was correlated to subsequent field emission measurements. Field emission characteristics, before and after anodisation, were obtained using a scanning electron microscope adapted for field emission measurements, and a field emission microscope. Extensive measurements showed that, following anodisation, there was substantial improvement in emission behaviour. After anodisation, the following was found to be true: i) The starting voltage was reduced by up to 50% (with p<sup>+</sup -type PS emitters exhibiting a greater reduction in starting voltage than p-type PS emitters). ii) Number of emitting tips per array was increased. iii) Higher maximum currents (up to 3 times higher) were obtained before tips underwent destruction. iv) The resistive effect of the PS layer at the apex was important in determining the maximum current obtained from a tip. In addition, both field emission and field ion microscopy were used to identify the emission source following anodisation. It was shown that individual fibrils on the emission surface caused an increase in field enhancement over a flat plane, leading to emission at lower voltage. Overall, porous silicon appears to be a very promising material for field emission displays.
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Koker, Lynne. "Photoelectrochemical formation of porous silicon." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368290.
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Zheng, Wan Hua. "Photoluminescence study of porous silicon." HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/138.
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Ngan, Mei Lun. "Photoluminescence excitation of porous silicon." HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/139.
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DEMONTIS, VALERIA. "Porous Silicon applications in biotechnology." Doctoral thesis, Università degli Studi di Cagliari, 2007. http://hdl.handle.net/11584/266040.
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Biotechnology is a field in great expansion and the continuous boost for obtaining smaller and more efficient devices stimulates the increase of interest from the research community. Nanostructured materials, and among them porous silicon (PS), appear to be good candidates for coupling with biological molecules because of their peculiar characteristics. In the case of porous silicon, the most noticeable are the very large specific area, which allows the loading of large amounts of biological material in a very small volume, and the possibility to easily tailor the pore size and morphology as function of the kind of molecules to be introduced.
Besides, the proven biocompatibility and non toxicity of PS allow the development of electronic devices to be directly implanted into living organisms without risk of rejection.
In this thesis we mainly focus our attention on the fabrication and characterization of a porous silicon-based potentiometric biosensor for triglycerides analysis, made of a lipase immobilized on a mesoporous Si matrix. Prototypes, realized on 1 x 1 cm n+-type silicon wafers, show a very high enzymatic activity. Moreover the properties of these biosensors have been shown to be stable in a several months time interval, clearly showing their advantages with respect to traditional triglycerides detection systems. The Michaelis Menten curve is obtained to demonstrate the absence of diffusion problems. Potentiometric measurements are also shown.
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Stupakova, Jolanta. "Physical properties of porous silicon nanostructures under influence of microwave radiation." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080207_161717-66613.
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Just after discovery of porous silicon (PSi) there was clarified that its wide application in various fields opens new unexpected possibilities. One of the possibilities of products of porous silicon in microwave (MW) technique is carried out in the USA now. The propagation of MWs in PSi layers is under investigation. It has been shown that radio and optoelectronic connectors made from this material have low losses and can be applied to improve technique of cellular phone communication as well as other high frequency technique. It is obvious that the next element following the connector has to be the sensor of microwave radiation. The most practicable way would be to use porous silicon in the production of it. There are known MW detectors of crystal silicon for operating under the effects of hot charge carriers. Sensitivity of the sensors usually depends on the dimensions of separate parts of it. In general, sensitivity increases while reducing the mentioned above dimensions. The technology of porous silicon presents the advantage since the specific dimensions of PSi stem could be reduced up to the nanometre sizes. After having introduced PSi technology in production of sensors which require certain diminutive dimensions, it is possible to expect significant increase of the sensitivity of such sensors. Additional advantages are expected to be achieved from the quantum confinement effect. To realize promises of application of PSi in MW technique it is of relevance to... [to full text]<br>Atradus akytąjį silicį (ASi) paaiškėjo, kad daugelyje sričių jo panaudojimas atveria naujas netikėtas galimybes. Viena galimybių panaudoti akytojo silicio gaminius mikrobangų technikoje tiriama JAV. Tiriamas mikrobangų sklidimas ASi sluoksniuose. Parodyta, kad radijo- ir optoelektroninės jungtys iš šios medžiagos yra mažų nuostolių ir tinka panaudojimui tobulinant mobilaus ryšio ir kitą superaukštų dažnių techniką. Sekantis po jungties elementas turėtų būti superaukšto dažnio spinduliuotės jutiklis. Patogiausiai būtų jį gaminti iš tos pačios medžiagos – akytojo silicio. Yra žinomi kristalinio silicio mikrobangų spinduliuotės detektoriai, kurių fizinis veikimo pagrindas – karštųjų krūvininkų efektai. Jutiklių jautris priklauso nuo tam tikrų jo dalių matmenų. Jautris didėja mažinant minėtus matmenis. Akytojo silicio technologija suteikia tą privalumą, kad ją pritaikius ASi kamieno charakteringieji matmenys gali būti sumažinami iki nanometrų dydžio. Pritaikius ASi gamybos technologiją jutikliuose, kuriuose pageidaujama kaip galima mažesnių tam tikrų matmenų, galima tikėtis žymiai padidinti tokių jutiklių jautrį. Papildomų privalumų galima laukti ir iš pasireiškiančio ASi erdvinio kvantinio ribojimo (pagavimo) efekto. Tam, kad galima būtų spręsti apie ASi darinių panaudojimo superaukšto dažnio (SAD) technikoje perspektyvą, aktualu ištirti ASi sluoksnių ir darinių fizines savybes, veikiant juos SAD spinduliuotės lauku. Nei superaukšto dažnio spinduliuotės poveikis ASi savybėms... [toliau žr. visą tekstą]
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Riachy, Philippe. "Hierarchically Porous Silica Materials for the Encapsulation of Molecules of Interest." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0013/document.
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Ce travail porte sur la préparation de matériaux silicatés à porosité hiérarchisée pour l'encapsulation de molécules d'intérêt dans le domaine de la pharmacie et en tant que biocatalyseur. Afin d’atteindre cet objectif, les nano-émulsions sont choisies comme empreinte pour créer les macropores du matériau en raison de la taille homogène et réduite des gouttelettes de l’émulsion (inférieure à 100 nm). Pour cela le système Remcopal 4/décane/eau est investi en déterminant les conditions les plus optimales de formation de nano-émulsion, via les méthodes d'inversion de phases. L’ajout de micelles aux nano-émulsions ne déstabilise pas les émulsions et permet la formation d’un réseau de mésopores organisés selon une symétrie hexagonale. Les matériaux hybrides issus des matériaux poreux contenant encore la phase organique sont dopés par le ketoprofène en vue d’étudier la libération de ce dernier. Celle-ci se révèle sensible au pH. De plus, cette étude de la libération du kétoprofène à partir du matériau méso-macroporeux indique qu'elle est assistée par les micelles qui sont solubilisées dans la solution réceptrice. Le deuxième objectif de ce travail est d'utiliser ces matériaux poreux en tant que biocatalyseur pour la synthèse de biodiesel à partir d'huile de colza. Pour cette application, il est nécessaire que les matériaux résistent à l’immersion dans des milieux aqueux. L’étude de la stabilité hydrothermale a montré que le matériau calciné présente la meilleure stabilité dans l’eau bouillante. Par ailleurs, le matériau peut résister jusqu’à 550°C, la structure ne subissant que des dégradations mineures. Nous avons également utilisé un matériau silicaté à double mésoporosité préparé à partir de micelles fluorées et hydrogénées coexistant dans une même solution. L'évaluation thermique et hydrothermale indique que ces matériaux présentent deux cinétiques de déstructuration qui correspondent à chacune des deux matrices ayant deux tailles de pores différents. L’immobilisation de la lipase Mml est étudiée sur le matériau méso-macroporeux calciné et sur le matériau à double mésoporosité. Les isothermes d'adsorption ont permis de mettre en évidence que le matériau à double mésoporosité peut encapsuler plus d’enzymes que son homologue méso-macroporeux. L’activité enzymatique, au regard des réactions de transestérification, est de façon inverse plus importante avec le matériau méso-macroporeux calciné<br>This work concerns the preparation of silica materials with hierarchical porosity for the encapsulation of molecules of interest in the field of drug delivery and as biocatalysts. In order to reach this goal, the nano-emulsions were chosen as templates for the macropores of the material because of the homogeneous and small size of the emulsion droplets (less than 100 nm). The system Remcopal 4/decane/water was investigated and the optimal conditions for which nano-emulsion is formed via the phase inversion methods were determined. Adding micelles to the nano-emulsions does not affect its stability and can form a network of mesopores organized with a hexagonal symmetry. Hybrid materials which are hierarchically porous materials where the organic phase is still present, were doped with ketoprofen to study its release, which proved to be pH sensitive. Moreover, the study of the release of ketoprofen from the meso-macroporous material indicates that it is assisted by the micelles which are solubilized in the release medium. The second objective of this work was to use these porous materials as a biocatalyst for biodiesel synthesis from colza oil. For this application it was necessary that the materials are resistant to immersion in aqueous media. The study of the hydrothermal stability shows that the calcined material has the best stability in boiling water. Moreover, the material can withstand up to 550 ° C, the structure undergoes only minor damages. We also used a dual-mesoporous silica material prepared from hydrogenated and fluorinated micelles coexisting in the same solution. Thermal and hydrothermal evaluation indicates that these materials have two different decay kinetics corresponding to each of the two matrices having different pore sizes. The immobilization of lipase Mml was studied on the meso-macroporous calcined material and the dual-mesoporous material. The adsorption isotherms were used to demonstrate that the dual-mesoporous material can encapsulate more enzymes than its meso-macroporous counterpart. On the other hand, the enzyme activity, evaluated by the transesterification reactions, is more important for the calcined meso-macroporous material
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Flower, Andrew. "Polymer adsorption at a porous interface." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343309.
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Mabrook, Mohammed Fadhil. "Fabrication and characterisation of porous silicon." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/19990/.
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A systematic study has been made of the electrical conduction processes through electrically etched porous silicon (PS) films sandwiched between two metal electrodes. The PS layers were formed by anodisation of p-type silicon wafers in a hydrofluoric (HF) acid solution. The effect of fabrication conditions on the structural and electrical properties of PS have been investigated. The thickness of PS layers was found to depend on the anodisation time, whereas porosity was regarded to be controlled by the current density and HF acid concentration. The dark current-voltage I(V) characteristics at fixed temperature and the variation of current as a function of temperature have been established. The characteristics for all devices, regardless the metal contact, show a rectifying behaviour with ideality factor close to unity. It was found that PS films fabricated from p-type silicon substrates behave like n-type silicon due to the depletion of electronic holes. The results suggest that a pn heterojunction between PS and p-Si is responsible for the rectifying behaviour. A value of 0.7 eV was obtained for the barrier height at the interface between PS and p-Si at room temperature. The barrier height was found to increase with rising temperature. Recombination conduction process was found to be dominant at low temperatures as the activation energy did not exceed 0.22 eV. At high temperatures, thermionic emission diffusion process was found to be responsible for the current transport in the PS structures. A band model was proposed for metal/PS/p-Si/metal structures in order to explain the observed characteristics. A.c. dark current measurements revealed that the a.c. conductivity varies as ws where w is the angular frequency and s' is an index which depends on temperature and having a value less than unity. A.c. activation energy was interpreted in terms of hopping conduction at low temperatures (less than 200 K) and diffusion transport of charge carriers through PS layers at higher temperatures. Measurements of capacitance as a function of frequency and temperature showed a decrease with increasing frequency and increase with increasing temperature. The photoconduction behaviour of PS was characterised by high dark resistivity, a clear photosensitivity for visible light, and a bias voltage dependence of the spectral response.
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Squire, E. K. "Light emitting microstructures in porous silicon." Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285287.
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Ben, Ghozi-Bouvrande Justine. "Les liquides poreux : un nouveau concept pour la séparation chimique." Thesis, Montpellier, Ecole nationale supérieure de chimie, 2022. http://theses.enscm.fr/ENSCM_2022_BENGHOZI-BOUVRANDE.pdf.
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Les composés organiques volatiles étant un problème environnemental majeur, des alternatives à l’extraction liquide-liquide qui utilisent des solvants en grande quantité sont au cœur des recherches. Les liquides poreux à base de silice sont un nouveau type de matériau liquide, original et versatile, composés de nanoparticules greffées par des fonctions ioniques. De par leur forte versatilité et leur volatilité nulle, ce type de liquide représente un candidat prometteur pour remplacer les phases organiques de l’extraction liquide-liquide. Après un état de l’art des différents types de liquides poreux, ce manuscrit de thèse décrit la synthèse d’un liquide poreux de type I et la caractérisation de ce matériau à toutes les étapes de sa synthèse. Cette étude visant à démontrer la possibilité d’utiliser les liquides poreux pour l’extraction de métaux, la perméabilité de ces matériaux aux gaz et à des solutions aqueuses a été étudiée par diffusion des neutrons aux petits angles. Grâce à une expérience in situ originale, il a été montré que toute la porosité n’est pas accessible aux gaz lorsque les nanosphères de silice sont greffées pour être rendues liquides. Néanmoins, une étude par variation de contraste a montré que les nanosphères solides et les liquides poreux sont perméables aux solutions aqueuses. Des premiers tests d’extraction ont permis de prouver que grâce à cette perméabilité, les matériaux peuvent extraire des cations comme le plomb ou l’uranium dans des proportions intéressantes et via des modes d’extraction différents. Ces travaux ont montré que l’extraction de métaux par des liquides poreux est possible et ouvert ce sujet à de nombreuses perspectives d’optimisation<br>Organic volatile compounds are an important environmental stake. As liquid-liquid extraction is using huge quantities of organic solvents, finding an alternative process is the focus of many scientific research. Silica based porous liquids are made up with ionic functions grafted on silica nanoparticles. Thanks to their substantial versatility and low volatility, this type of porous liquid is considered in this thesis as a promising candidate to substitute organic phases of liquid-liquid extraction. After a state of the art describing the different types of porous liquids, this thesis describes the synthesis of the selected type I porous liquid and its complete characterization. Effect of several synthesis parameters on structure and porosity was also studied. In order to evaluate the possibility to use such porous liquid to extract metals, their permeability to gas and liquids was studied with small angles neutrons scattering. Thanks to an original in situ experiment coupling neutron scattering and contrast matching gas sorption, it was shown that porosity is not fully accessible to gas when the solid nanospheres are grafted to become liquid. However, a contrast matching study showed that both solid nanospheres and porous liquids are permeable to aqueous solutions. Preliminary extraction tests showed that thanks to this permeability, these materials are able to extract cations such as lead, lanthanum or uranium with interesting proportions. Different extraction mechanisms as sorption, precipitation or chelation on functional groups were obtained. This work shows that extraction of metal species by porous liquid is possible and opens many perspectives for optimization
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Gao, Wei. "Oxidation of nitride-bonded silicon carbide (NBSC) and hot rod silicon carbide with coatings." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366751.
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Fowler, Christabel Emma. "Templating strategies for the formation of porous silica." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364903.
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Fedeyko, Joseph M. "Silica phase behavior and the formation of microporous and mesoporous materials." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 5.93 Mb., 258 p, 2006. http://proquest.umi.com/pqdlink?did=1172110321&Fmt=7&clientId=79356&RQT=309&VName=PQD.
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Noble, Kate. "Preparation of organically modified mesoporous materials via sol-gel processing." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340139.
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Ezzeddine, Zeinab. "Divalent heavy metals adsorption on various porous materials : removal efficiency and application." Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2315/document.
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L'accès à l'eau potable est indispensable au développement de la vie. La pollution, liée aux activités anthropiques, constitue une menace pour la santé humaine et pour les espèces sauvages. Parmi les nombreux polluants retrouvés dans les eaux, la pollution par les métaux lourds constitue un problème environnemental d'intérêt mondial en raison de leur toxicité élevée, même à des concentrations très faibles, et de leur persistance dans la nature. De nombreuses méthodes peuvent être mises en oeuvre pour l'élimination des métaux lourds dans l'eau. Parmi elles, les procédés d'adsorption sont très attractifs car très efficaces et peu couteux. Les zéolithes sont des matériaux bien connus pour leurs propriétés d'échange. Les matériaux mésoporeux modifiés ou adsorbants carbonés sont également très attractifs du fait de leur importante surface spécifique. Dans ce manuscrit, les performances d'adsorption de cations métalliques en phase aqueuse sur des matériaux mésoporeux, silices SBA-15, SBA-16, KIT-6 modifiées par l'EDTA et carbone CMK-3 obtenu par réplication ont été étudiées et comparées avec celles de la zéolithe NaX. Les propriétés physico-chimiques de l'ensemble des matériaux ont été caractérisées par plusieurs techniques d'analyses. L'influence des paramètres expérimentaux (pH, temps de contact, température, concentration des ions métalliques et de la présence d'ions concurrents) sur l'adsorption a été étudiée en mode batch. L'efficacité de ces matériaux a également été étudiée dans un réacteur dynamique à lit fixe. Les résultats obtenus ont montré que tous les matériaux étudiés éliminent efficacement et rapidement les métaux divalents dans les eaux même à faible concentration. Néanmoins, le carbone CMK-3 s'avère être le meilleur adsorbant du fait de sa grande capacité d'adsorption même en présence d'espèces compétitrices<br>Access to sustainable and clean drinking water is a main concern as the Earth's human population continues its steady growth. Unfortunately, many of the available water resources are becoming increasingly polluted as a result of the direct discharge of industrial effluents. Heavy metals pollution, in particular, is an environmental problem of global interest due to their high toxicity, even at very low concentrations, and persistence in nature. Many methods are available for metal ions removal including adsorption which is attracting a lot of attention recently. Zeolites are well known for having very high exchange capacities. On the other hand, many researchers are studying the removal of heavy metals by modified mesoporous materials or carbonaceous adsorbents. In this thesis, the adsorption efficiencies of several materials for heavy metal removal in aqueous phase were investigated and compared to those of the faujasite NaX zeolite. Mesoporous silica SBA-15, SBA-16, KIT-6 were synthesized and modified with EDTA. Moreover, CMK-3 carbon was nano-casted from SBA-15 then the physic-chemical properties of these materials were characterized by different techniques. The effects of several experimental conditions on adsorption such as pH, contact time, temperature, metal ions concentration and the presence of competitors were studied in batch experiments. Then the efficiency of all these materials was also studied in a dynamic fixed bed reactor. Based on the obtained results, it could be said that all these materials are good candidates for divalent heavy metals removal from waste water even at low concentration. However, CMK-3 material has a high sorption capacity even in presence of competitor species
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DeBoer, John Raymond. "Evaluation Methods for Porous Silicon Gas Sensors." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4971.
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This study investigated the behavior of porous silicon gas sensors under exposure to CO, NO, and NH3 gas at the part per million level. Parameters of interest in this study included the electrical, environmental, and chemi-resistive performance associated with various porous silicon morphologies. Based upon the variability of preliminary results, a gas pulsing method was combined with signal processing in order to analyze small impedance changes in an environment of substantial noise. With this technique, sensors could be effectively screened and characterized. Finally this method was combined with various post-treatments in order to improve the sensitivity and selectivity of individual sensors.
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Pap, A. E. (Andrea Edit). "Investigation of pristine and oxidized porous silicon." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514277759.
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Abstract
While numerous publications deal with the properties and applications of porous silicon (PS), some of the related topics are not complete or could be investigated from different aspects. Therefore, the main objective of this thesis is to provide novel information associated with the optical and chemical properties of PS.
For the investigations, various PS samples are manufactured by electrochemical dark etching of boron-doped p+-type Si wafers. Amongst others, (i) the wavelength-dependent refractive indices of freestanding PS monolayers having different porosities were obtained from optical transmission and reflection spectra in the 700–1700 nm wavelength range, and compared to those calculated from Bruggeman's effective medium approximation (EMA). The refractive indices of the PS samples are shown to be described well with the EMA. In addition, optical scattering at the air-PS interface was demonstrated. (ii) Multilayer stacks are created by alternating the porosities of PS layers within the same sample to form Bragg filters. The Bragg conditions of the filters are calculated and compared to optical transmission measurements. (iii) The oxidation of PS membranes in dry air is investigated with emphases on the reaction kinetics and on the structural changes of the porous matter. As revealed, oxidation proceeds faster in PS than in Si bulk. The formed SiO2 is amorphous and causes stress in the lattice of the residual Si skeleton. (iv) The effect of oxidation extent of PS layers on the growth mechanism of multi-walled carbon nanotubes (CNTs) is investigated. The density of the CNT network is found proportional to the oxidation extent of the substrates. (v) Finally, the chemically-reductive nature of PS is studied and exploited via the immersion plating method to deposit palladium and silver nanoparticles in the nanopores and on the surface of PS samples.
The presented novel results have potential in silicon-based technologies, including integrated active and passive optical components (waveguides, filters, antireflection coatings, optical gas/liquid sensors), electronic devices (electrochemical gas/liquid sensors, diodes, field effect devices) and selective chemical catalysis (substrates, growth templates).
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余家訓 and Ka-fan Yu. "Scanning probe microscopy of porous silicon formation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31222110.
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Barker, Carolyn Marie. "Catalytic processes in porous transition metal silicates." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271958.
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Chang, Wai-Kit. "Porous silicon surface passivation and optical properties." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41426.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.<br>"June 1996."<br>Includes bibliographical references (leaves 84-85).<br>by Wai-Kit Chang.<br>S.M.
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To, Wai Keung. "Tunable wavelength from porous silicon-based devices." HKBU Institutional Repository, 2009. http://repository.hkbu.edu.hk/etd_ra/1094.
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Tsuboi, Takashi. "Structure and Properties of Porous Silicon Surface." Kyoto University, 1999. http://hdl.handle.net/2433/181681.
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Tobail, Osama. "Porous silicon for thin solar cell fabrication." Aachen Shaker, 2008. http://d-nb.info/992052904/04.
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Kodumuri, Pradeep. "IN-SITU GROWTH OF POROUS ALUMINO-SILICATES AND FABRICATION OF NANO-POROUS MEMBRANES." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243304850.
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Goubert-Renaudin, Stéphanie. "Synthèse, caractérisation et réactivité en milieu aqueux de matériaux à base de silice fonctionnalisée par des ligands dithiocarbamate et cyclame." Thesis, Nancy 1, 2007. http://www.theses.fr/2007NAN10127/document.
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La fonctionnalisation de silices mésoporeuses par des ligands dithiocarbamate et cyclame a été réalisée. La réactivité des solides en milieu aqueux a été étudiée afin d’évaluer leur potentiel pour des applications de type capteurs électrochimiques. La synthèse originale de siloxydithiocarbamates a conduit à une nouvelle voie de préparation de silices fonctionnalisées par greffage direct du dérivé silylé sur le matériau. Des silices mésoporeuses ordonnées ou non (K60, SBA15, MCM41) portant des fonctions dithiocarbamate ont ainsi été obtenues. Des matériaux analogues ont aussi été préparés selon l’unique route décrite dans la littérature (réaction de CS2 sur une silice aminée). L’intérêt de la nouvelle approche proposée est l’accès direct à une silice portant des groupes dithiocarbamate dépourvue d’amines résiduelles, sans altération de sa mésoporosité. De plus, les matériaux ainsi préparés ont des propriétés de complexation accrues envers Hg(II). Trois dérivés du cyclame portant 1, 2 ou 4 bras silylés ont été greffés sur des silices K60 et SBA15. L’augmentation du degré de silylation entraine une stabilité accrue du solide en solution sans s’affranchir du relargage de l’organosilane classiquement observé pour les silices aminées. Ce gain de stabilité s’accompagne d’une baisse de réactivité du matériau, révélant l’existence d’une balance réactivité - stabilité. La fixation de Cu(II) sur la silice est essentiellement limitée par la vitesse de formation du complexe plutôt que la cinétique de diffusion des espèces. Un capteur ampérométrique sélectif de Cu(II) a été mis au point grâce aux propriétés complexantes de ces silices incorporées au sein d’électrodes à pâte de carbone<br>Dithiocarbamate- and cyclame-functionalized mesoporous silicas have been prepared and characterized. Their reactivity in aqueous medium has been investigated to evaluate their potential use as electrochemical sensors. A novel one-step route towards dithiocarbamate-silicas has been developed thanks to the original synthesis of siloxydithiocarbamate precursors. This is based on the direct grafting of the precursor onto the silica surface. Mesoporous silicas (ordered or not, i.e., K60, SBA15, MCM41) functionalized with dithiocarbamate moieties have thus been obtained. Analogous materials have also been prepared according to the sole two-step procedure available to date in the literature (reaction of CS2 onto an amino-silica). The interest of the proposed approach compared to the one previously reported is to access undamaged dithiocarbamate-modified silicas, free of remaining amino groups, displaying better efficiencies for Hg(II) uptake. Three cyclam derivatives bearing 1, 2 or 4 silylated arms have been grafted onto mesoporous silicas (K60 and SBA15). Increasing the silylation degree improves the material stability in aqueous medium without preventing the leaching of the organic moiety usually observed for amino-silicas. Higher stability of the material, poorer reactivity towards protons and Cu(II) binding have been noticed. Cu(II) uptake process seems to be rate-limited by the kinetics associated to complex formation rather than mass-transfer rates into the porous matrix. Incorporation of these materials into carbon paste electrodes has led to a selective amperometric sensor for Cu(II)
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Li, Wenle. "Study of Freeze-Cast Porous Silica Nanoparticle-Based Composites." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/38770.
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Porous silica-based nanocomposites are promising ceramics, as they exhibit high specific surface area, highly porous network, and a surface that can be easily functionalized. This dissertation describes the results of a study on the formation and properties of porous silica nanoparticle-based composites, using techniques of freeze casting and sintering. Kaolinite platelets and silica nanorods were added into the nanoparticle system, and their effects on modifying the porous microstructures and physical properties were investigated.
During freeze casting, homogeneous microstructures with highly interconnected porosity are fabricated. Kaolinite addition results in large and more interconnected pores, while added silica nanorods cause a pore morphology evolution from circular to elongated spherical pores with increasing aspect ratio. The specific surface areas (area/mass) of the particles are conserved during freeze casting and values for the resulting composites can be accurately predicted using the area and mass of the components assuming conservation of area. Both kaolinite platelets and silica nanorods effectively improved the strength of the freeze cast green composites as they distribute any applied stress over a larger portion of the sample.
Upon sintering, added kaolinite is found to modify the sintering behavior of the silica nanoparticles and a transitioning interfacial phase is identified when sintering temperature is above 1250 °C. This new phase contributes to the further enhancement of strength and this strengthening effect depends on composition and initial solids loading. After sintering at 1250 °C for 1 h, a ceramic containing 10 vol% kaolinite and 8 vol% silica has a maximum strength while maintaining a ~69% porosity. The kaolinite-silica composites with lower solids loading exhibit faster sintering (e.g. larger shrinkage, more extensive thickening of the pore walls), which, in turn, results in a rapid increase in mechanical strength.
Based on the understanding of the composite properties and the underlying principles, a novel method for creating nanocomposites with precisely controllable specific surface area is developed. With repeated nanoparticle suspension infiltration, freeze drying, and sintering, the specific surface area can be varied from less than one to well over 100 m2/g, demonstrating potential application as liquid membranes.<br>Ph. D.
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Chen, Chien-Cheng. "OPTICAL MEASUREMENT OF ENVIRONMENTAL URANIUM USING POROUS SILICA MATERIALS." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2241.
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The focus of this research is on the optical measurement of uranyl in a solid matrix using fluorescence spectroscopy. Nanoporous silica-based materials were used to extract uranyl from contaminated soil and to enhance the fluorescence intensity and lifetime. The fluorescence lifetime and intensity of uranyl ions adsorbed on porous silica-based materials of varying pore size was measured as a function of pH and in the presence of fluoride. The feasibility of uranyl fluorescence detection on the top of soil by silica gel is carried out by four types of natural soil. The results show that the uranyl fluorescence intensity can be enhanced by approximately two orders of magnitude by the silica nanoporous matrix from pH 4-12 with the greatest enhancement occurring from pH 4-7. The enhanced fluorescence lifetime can be used in time-gated measurements to help minimize the influence of background environmental fluorophores. The pH and the fluoride variation causes different uranyl speciation and results in a peak shift in the fluorescence spectrum. The mechanism of the uranyl ion on the silica nanoporous matrix was studied through 15 different silica materials with different water content ratios and various concentrations of uranium on different silica structures. The result shows that the particle size, pore size, water content and uranyl concentration on silica surfaces are all important factors for optimizing the fluorescence intensity. The spacing between silica materials, either the pore inside materials or the space between particles, causes the variety of uranyl distribution on the material surface and changes the fluorescence performance. Also, X-Ray Photoelectron Spectroscopy (XPS) is used to identify the possible uranyl surface species on silica. The fluorescence emission spectra from silica materials and the XPS results are consistent with the presence of two different uranyl compounds. The specific surface area of silica materials plays an important role on uranyl adsorption mechanism. To further enhance the sensitivity, an optical ball lens was used to preferentially direct the fluorescence signal toward the excitation source in standoff measurements. The application of the ball lens was found to increase the detection distance up to 14 times.
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Silva, Francisco Wellery Nunes. "Transporte eletrônico em semicondutores porosos baseado na equação de Schrodinger dependente do tempo." reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/11710.
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SILVA, Francisco Wellery Nunes. Transporte eletrônico em semicondutores porosos baseado na equação de Schrodinger dependente do tempo. 2012. 77 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2012.<br>Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-04-23T21:11:22Z
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Previous issue date: 2012<br>We propose in this work a theoretical study, of the properties of a electronic pulse, injected under a external bias, on a porous silicon layer, so that we could define fundamentally the shape of T X V and R X V curves, where T is the transmission coefficient and R is the reflection coefficient of the wave packet, trough the porous region. With this, we could make a simple calculation and obtain information about the electrical current in this material, using the very simple model I=Q/t, where we defined the time of transmission, as the time interval necessary for the electronic pulse to be consumed completely. This kind of approach is already known in the literature, propose by Lebedev and co-workers (1998). Using the definition of charge carrier mobility, we obtained information about it, since the principal aim of this work is the electronic transport in this kind of material, that despite a strong research on porous silicon, since the beginning of the nineties, the transport properties still remains a relatively unexplored area. The major incentive for this study is due to the strong possibility of application of this material in new optoelectronic devices such as LEDs. Along the development of this dissertation, we applied well known techniques for the computational modelling such as effective mass theory, for example, associated with methods like the periodic boundary conditions, and the absorbing boundary conditions. Treating of a quantum system, we begin all the work solving the time dependent Schröedinger equation. To do this task, we have used the numerical method known as Split-Operator, in order to obtain the solutions for this equation. Initially, the calculations in this dissertation where based in an isotropic effective mass, in order to optimise the calculation parameters. After this, we made calculations using an anisotropic effective mass for the different valleys of silicon. All these things leads us to believe that this work have a great importance regarding the contribution to the understanding of transport in electronic systems based on porous silicon, to maintain for some time the applications of this kind of material that was so revolutionary in the twentieth.<br>Neste trabalho, propomos um uma pesquisa teórica onde estudamos as propriedades de um pulso eletrônico em uma camada de silício poroso, injetado sob uma certa voltagem externa V. Desta forma, podemos definir fundamentalmente a forma das curvas T X V e R X V, onde T é o coeficiente de transmissão e R é o coeficiente de reflexão do pacote de onda através da região porosa. Aliado a estes dados, podemos fazer um cálculo simples e obter informações a respeito da corrente elétrica que atravessa o material, utilizando o modelo I=Q/t, onde definimos o tempo como o intervalo necessário para que o pulso seja consumido completamente, como proposto por Lebedev e colaboradores (1998). Utilizando a definição para mobilidade de portadores de carga, obtivemos informações sobre a mesma, pois este trabalho foca-se principalmente no estudo do transporte eletrônico neste tipo de material poroso, que apesar de um estudo intenso em silício poroso desde o início da década de noventa, as propriedades de transporte ainda permanecem um pouco inexploradas. O principal incentivo para que estudemos este material é devido à grande possibilidade da criação de dispositivos em opto-eletrônica tais como LEDs (Light Emissor Diode). Ao longo do desenvolvimento, empregamos técnicas já bem conhecidas para a modelagem de semicondutores, como a teoria da massa efetiva, por exemplo, associadas a técnicas de modelagem computacional, como o emprego de condições periódicas de contorno e condições de contorno absorvente. Por se tratar de um sistema quântico, tudo parte da solução da equação de Schrödinger dependente do tempo, e para executar esta tarefa fizemos uso de um método numérico conhecido como Split-Operator. Assim obtemos as soluções para a equação. Inicialmente, os cálculos realizados neste trabalho foram baseados em uma massa efetiva isotrópica, a fim de otimizar os parâmetros de cálculo, e só em seguida foram feitos cálculos baseando-se em massa efetiva anisotrópica para os diversos vales do silício poroso. Tudo isto nos leva a crer que este trabalho possui uma grande importância no que diz respeito à contribuição para o entendimento do transporte eletrônico em sistemas baseados em silício poroso, de forma a manter por mais algum tempo a aplicação deste tipo de material que foi tão revolucionário no século XX.
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Haryadi, Haryadi Chemistry Faculty of Science UNSW. "Porous hybrid organic-inorganic silica materials: preparation, structural and transport properties." Awarded by:University of New South Wales. School of Chemistry, 2005. http://handle.unsw.edu.au/1959.4/28806.
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The aim of this project was to prepare a series of silica materials based on sol-gel processing of alkoxysilanes using glucose and glycerol as templates for potential applications in membrane design for pervaporation. The materials were characterized using structural and dynamic techniques to gain information about the effect of the templates on the formation of micro- and mesoporous silicates. The interaction between templates and silica matrices were investigated using FTIR, Raman Spectroscopy, Solid State NMR Spectroscopy, Physisorption and SEM. Close contact between templates and silica networks was observed by NMR cross polarization studies. The chemistry was then extended to prepare hybrid organic-inorganic silica materials by introducing organic ligands, with glycerol as a template to control the porosity of the hybrid materials. By varying the ligand as well as the template, the physical properties of the gel can be controlled. Composites of hydroxypropylcellulose, HPC, and silica were also prepared and characterized. There was no phase separation during sol-gel processing suggesting HPC was dispersed homogenously in the silica matrices. This was also confirmed by solid state NMR. Temperature dependence showed some indications of conformational change in the HPC within the silicate, above 308K. The transport properties of the hybrid materials were observed by monitoring the diffusion behaviour of water and several selected solvents using Pulsed Field Gradient NMR. The self-diffusion of water and the organic solvents in the hybrid silica materials were two to three orders of magnitude smaller than in the liquid bulk suggesting restricted diffusion at the pore surface. The effect of surface polarity also contributed to water and solvents diffusivities. The temperature dependence of diffusion was useful to derive the activation energy whereas the dependence on NMR observation time provided information on both tortuosity and pore connectivity of the hybrid silica materials. The hybrid silica membranes were prepared by spin coating of polymeric silica sol on top of a macroporous alumina support after being occluded by colloidal silica. It was then used for pervaporation of water ethanol mixtures. The results implied that separation factor increased as the temperature increased. However permeate fluxes were less affected.
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Cervantes, Martínez Claudia Violeta. "Porous and hybrid silica from biocompatible systems : application to drug release." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0295.
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L'objectif de ce travail se concentre sur la préparation de matériaux poreux silicatés hybrides et dopés avec un principe actif, à base de composants biocompatibles pour des applications pharmaceutiques, en tant que systèmes d’administration de médicaments. La motivation de cette étude est liée à la nécessité de répondre à la demande croissante de médicaments plus efficaces. Le premier point d'intérêt de cette étude concerne les composés utilisés qui sont biocompatibles, peu coûteux, et qui, sont de bons candidats pour la formation de matériaux mésostructurés. Le tensioactif utilisé était le Kolliphor EL (KEL) et les huiles retenues étaient le Miglyol 812N (Mig), et le Myristate d’Isopropyl (IM). Le principe actif le Kétoprofène (KTP) a été choisi comme molécule modèle pour l’évaluation de les essaies de libération. En fin, les cellules HeLa, un type particulier de cellules cancéreuses, ont été utilisées pour évaluer la toxicité des matériaux synthétisés. Le premier chapitre est consacré à l'état de l'art des structures moléculaires à partir des tensioactifs non-ioniques, en particulière le KEL. Ensuite, les principales publications relatives aux matériaux poreux et hybrides en tant que vecteurs de drogues sont résumées. À la fin de ce chapitre, les modèles cinétiques de libération et les équations correspondantes sont présentées. Le second chapitre rassemble les modes opératoires et les techniques de caractérisation utilisés Le troisième chapitre étude le comportement de phase du système binaire KEL/eau étudié dans le cadre de ce travail est décrit. Les différents domaines à 1 et 2 phases ont été déterminés et caractérisés par inspection visuel, à l’aide de la microscopie optique à lumière polarisée et les structures aux des cristaux liquides par SAXS. Ensuite, l'influence de l'addition d’huile dans le système KEL/eau a été étudié à 25 °C Les diagrammes de phase ternaire ont été établis avec Miglyol (Mig) et Isopropyl Myristate (IM). À partir de ces systèmes à base de Mig et IM, des matériaux mésoporeux ont été préparés. Avec des conditions de synthèse optimisées, on a réussi à structurer le réseau mésoporeux dans les deux cas. Dans le quatrième chapitre l’influence de l’addition d’un copolymère block, le P123 dans le système KEL/eau est reportée et le diagramme de phase est présente. Il a permis d'évaluer la synergie des deux tensioactifs pour former des micelles et des cristaux liquides. Ensuite, l’effet de l’addition de micelles de P123 dans les émulsions fines á base d’Isopropyl Myristate sur les caractéristiques des matériaux poreux ainsi préparés en utilisant différentes teneurs de micelles de P123, il est possible de faire varier le degré de porosité des matériaux. Pour des proportions émulsions (Em)/micelles P123 inférieures à 50/50, on obtient des silices mésoporeuses avec deux tailles de pores. Lorsque le rapport Em/P123 augmente, est possible de contrôler la porosité des matériaux. Le cinquième chapitre concerne sur l'étude de l'encapsulation de KTP dans différents systèmes et de sa libération. Des émulsions concentrées ainsi que des matériaux hybrides à base de solutions micellaires et d'émulsions fines ont été sélectionnés. Les études de libération ont été effectuées avec une solution de PbS a différents pH :7,4; 1,2 et 4,6. Les résultats ont montré que, dans des conditions neutres, le KTP libéré par les matériaux hybrides à base des solutions micellaires atteint 38% au bout de 24h et l’effet du pH permet d’augmenter la quantité de KTP libéré. Ensuite, la libération dans une solution réceptrice avec diffèrent concentrations de P123 a été étudié. Les résultats montrent que la quantité de KTP libéré en présence de 5% de P123, atteindre 65% au bout de 24h. Dans la dernière partie, la toxicité des matériaux et des systèmes hybrides dopés a été évalué. Les résultats montrent que la matrice de silice protège les cellules car la viabilité cellulaire est augmentée, de 64 à presque 80% avec les matériaux hybrides<br>The objective of this work focuses on the preparation of porous, hybrid silicate materials doped with an active ingredient, based on biocompatible components for pharmaceutical applications, as drug delivery systems. The motivation for this study is related to the need to meet the growing demand for more effective drugs. The first point of interest of this study concerns the compounds used which are biocompatible, low-cost, and which are good candidates for the formation of mesostructured materials. The surfactant used was Kolliphor EL (KEL) and the oils were Miglyol 812N (Mig), and Isopropyl Myristate (IM). The active ingredient Ketoprofen (KTP) was chosen as the molecule model for the evaluation of release assays. Finally, HeLa cells, a cancer cell, were used to assess the toxicity of the synthesized materials. The first chapter is devoted to the state of the art of molecular structures based on non-ionic surfactants as KEL. Then, the main publications relating to porous and hybrid materials as drug carriers are summarized. At the end of this chapter, the kinetic release models and corresponding equations are presented. The second chapter brings together the methods and characterization techniques used. The third chapter studies the phase behaviour of the KEL/water binary system studied in this work and is described. The different 1- and 2-phase domains were determined and characterized by visual inspection, using polarized light optical microscopy and liquid crystal structures by SAXS. Then, the influence of oil addition in the KEL/water system was studied at 25°C. Ternary phase diagrams were established with Miglyol (Mig) and Isopropyl Myristate (IM). From these Mig and IM-based systems, mesoporous materials were prepared. With optimized synthesis conditions, the mesoporous network was structured in both cases. In the fourth chapter the influence of the addition of a block copolymer, the P123 in the KEL/water system is reported and the phase diagram is present. It evaluated the synergy of the two surfactants to form micelles and liquid crystals. Then, the effect of the addition of P123 micelles in Isopropyl Myristate based fine emulsions on the characteristics of the porous materials thus prepared using different P123 micelle contents, it is possible to vary the degree of porosity of the materials. For emulsion (Em)/micelle P123 proportions less than 50/50, mesoporous silicas with two pore sizes are obtained. When the Em/P123 ratio increases, it is possible to control the porosity of the materials. The fifth chapter concerns the study of the encapsulation of KTP in different systems and its release. Concentrated emulsions as well as hybrid materials based on micellar solutions and fine emulsions have been selected. Release studies were performed with a PbS solution at different pH levels: 7.4; 1.2 and 4.6. The results showed that, under neutral conditions, the KTP released by hybrid materials based on micellar solutions reaches 38% after 24 hours and the pH effect increases the amount of KTP released. Then, the release into a receptor solution with different concentrations of P123 was studied. The results show that the amount of KTP released in the presence of 5% P123, reach 65% after 24 hours. In the last part, the toxicity of doped materials and hybrid systems was assessed. The results show that the silica matrix protects the cells because cell viability is increased, from 64 to almost 80% with hybrid materials
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Coleman, Nicholas Richard Boldero. "Direct liquid crystal templating of mesoporous silica and platinum." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302011.
Full text
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Alvarez, Sara D. "Stability and biocompatability of porous silicon and porous alumina for cell and biomolecular sensing." Diss., [La Jolla, Calif.] : University of California, San Diego, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3338847.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2008.<br>Title from first page of PDF file (viewed Jan. 13, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 126-141).
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Newby, Pascal. "Fabrication de semiconducteurs poreux pour am??liorer l'isolation thermique des MEMS." Thèse, Universit?? de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/98.
Full textAbstract:
R??sum?? : L???isolation thermique est essentielle dans de nombreux types de MEMS (micro-syst??mes ??lectro-m??caniques). Elle permet de r??duire la consommation d?????nergie, am??liorer leurs performances, ou encore isoler la zone chaude du reste du dispositif, ce qui est essentiel dans les syst??mes sur puce. Il existe quelques mat??riaux et techniques d???isolation pour les MEMS, mais ils sont limit??s. En effet, soit ils ne proposent pas un niveau d???isolation suffisant, sont trop fragiles, ou imposent des contraintes trop importantes sur la conception du dispositif et sont difficiles ?? int??grer.
Une approche int??ressante pour l???isolation, d??montr??e dans la litt??rature, est de fabriquer des pores de taille nanom??trique dans le silicium par gravure ??lectrochimique. En nanostructurant le silicium ainsi, on peut diviser sa conductivit?? thermique par un facteur de 100 ?? 1000, le transformant en isolant thermique. Cette solution est id??ale pour l???int??gration dans les proc??d??s de fabrication existants des MEMS, car on garde le silicium qui est d??j?? utilis?? pour leur fabrication, mais en le nanostructurant localement, on le rend isolant l?? o?? on en a besoin. Par contre sa porosit?? cause des probl??mes : mauvaise r??sistance chimique, structure instable au-del?? de 400??C, et tenue m??canique r??duite. La facilit?? d???int??gration des semiconducteurs poreux est un atout majeur, nous visons donc de r??duire les d??savantages de ces mat??riaux afin de favoriser leur int??gration dans des dispositifs en silicium. Nous avons identifi?? deux approches
pour atteindre cet objectif : i) am??liorer le Si poreux ou ii) d??velopper un nouveau mat??riau.
La premi??re approche consiste ?? amorphiser le Si poreux en l???irradiant avec des ions ?? haute ??nergie (uranium, 110 MeV). Nous avons montr?? que l???amorphisation, m??me partielle, du Si poreux entra??ne une diminution de sa conductivit?? thermique, sans endommager sa structure poreuse. Cette technique r??duit sa conductivit?? thermique jusqu????? un facteur de trois, et peut ??tre combin??e avec une pr??-oxydation afin d???atteindre une r??duction d???un facteur cinq. Donc cette m??thode permet de r??duire la porosit?? du Si poreux, et d???att??nuer ainsi les probl??mes de fragilit?? m??canique caus??s par la porosit?? ??lev??e, tout en gardant un niveau d???isolation ??gal.
La seconde approche est de d??velopper un nouveau mat??riau. Nous avons choisi le SiC poreux : le SiC massif a des propri??t??s physiques sup??rieures ?? celles du Si, et donc ?? priori le SiC poreux devrait conserver cette sup??riorit??. La fabrication du SiC poreux a d??j?? ??t?? d??montr??e dans la litt??rature, mais avec peu d?????tudes d??taill??es du proc??d??. Sa conductivit?? thermique et tenue m??canique n???ont pas ??t?? caract??ris??es, et sa tenue en temp??rature que de fa??on incompl??te.
Nous avons men?? une ??tude syst??matique de la porosification du SiC en fonction de la concentration en HF et le courant. Nous avons impl??ment?? un banc de mesure de la conductivit?? thermique par la m??thode ?? 3 om??ga ?? et l???avons utilis?? pour mesurer la conductivit?? thermique du SiC poreux. Nous avons montr?? qu???elle est environ deux ordres de grandeur plus faible que celle du SiC massif. Nous avons aussi montr?? que le SiC poreux est r??sistant ?? tous les produits chimiques typiquement utilis??s en microfabrication sur silicium. D???apr??s nos r??sultats il est stable jusqu????? au moins 1000??C et nous avons obtenu des r??sultats qualitatifs encourageants quant ?? sa tenue m??canique. Nos r??sultats signifient donc que le SiC poreux est compatible avec la microfabrication, et peut ??tre int??gr?? dans les MEMS comme isolant thermique. // Abstract : Thermal insulation is essential in several types of MEMS (micro electro-mechanical systems). It can help reduce power consumption, improve performance, and can also isolate the hot area from the rest of the device, which is essential in a system-on-chip. A few materials and techniques currently exist for thermal insulation in MEMS, but these are limited. Indeed, either they don???t have provide a sufficient level of insulation, are too fragile, or restrict design of the device and are difficult to integrate.
A potentially interesting technique for thermal insulation, which has been demonstrated in
the literature, is to make nanometer-scale pores in silicon by electrochemical etching. By
nanostructuring silicon in this way, its thermal conductivity is reduced by a factor of 100 to
1000, transforming it into a thermal insulator. This solution is ideal for integration in existing MEMS fabrication processes, as it is based on the silicon substrates which are already used for their fabrication. By locally nanostructuring these substrates, silicon is made insulating wherever necessary. However the porosity also causes problems : poor chemical resistance, an unstable structure above 400???C, and reduced mechanical properties. The ease of integration of porous semiconductors is a major advantage, so we aim to reduce the disadvantages of these materials in order to encourage their integration in silicon-based devices. We have pursued two approaches in order to reach this goal : i) improve porous Si, or ii) develop a new material.
The first approach uses irradiation with high energy ions (100 MeV uranium) to amorphise
porous Si. We have shown that amorphisation, even partial, of porous Si leads to a reduction of its thermal conductivity, without damaging its porous structure. This technique can reduce the thermal conductivity of porous Si by up to a factor of three, and can be combined with a pre-oxidation to achieve a five-fold reduction of thermal conductivity. Therefore, by using this method we can use porous Si layers with lower porosity, thus reducing the problems caused by the fragility of high-porosity layers, whilst keeping an equal level of thermal insulation.
The second approach is to develop a new material. We have chosen porous SiC: bulk SiC has exceptional physical properties and is superior to bulk Si, so porous SiC should be superior to porous Si. Fabrication of porous SiC has been demonstrated in the literature, but detailed studies of the process are lacking. Its thermal conductivity and mechanical properties have never been measured and its high-temperature behaviour has only been partially characterised.
We have carried out a systematic study of the effects of HF concentration and current on
the porosification process. We have implemented a thermal conductivity measurement setup using the ???3 omega??? method and used it to measure the thermal conductivity of porous SiC. We have shown that it is about two orders of magnitude lower than that of bulk SiC. We have also shown that porous SiC is chemically inert in the most commonly used solutions for microfabrication. Our results show that porous SiC is stable up to at least 1000???C and we have obtained encouraging qualitative results regarding its mechanical properties. This means that porous SiC is compatible with microfabrication processes, and can be integrated in MEMS as a thermal insulation material.
48
Newby, Pascal. "Fabrication de semiconducteurs poreux pour améliorer l'isolation thermique des MEMS." Thèse, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/98.
Full textAbstract:
Résumé : L’isolation thermique est essentielle dans de nombreux types de MEMS (micro-systèmes électro-mécaniques). Elle permet de réduire la consommation d’énergie, améliorer leurs performances, ou encore isoler la zone chaude du reste du dispositif, ce qui est essentiel dans les systèmes sur puce. Il existe quelques matériaux et techniques d’isolation pour les MEMS, mais ils sont limités. En effet, soit ils ne proposent pas un niveau d’isolation suffisant, sont trop fragiles, ou imposent des contraintes trop importantes sur la conception du dispositif et sont difficiles à intégrer.
Une approche intéressante pour l’isolation, démontrée dans la littérature, est de fabriquer des pores de taille nanométrique dans le silicium par gravure électrochimique. En nanostructurant le silicium ainsi, on peut diviser sa conductivité thermique par un facteur de 100 à 1000, le transformant en isolant thermique. Cette solution est idéale pour l’intégration dans les procédés de fabrication existants des MEMS, car on garde le silicium qui est déjà utilisé pour leur fabrication, mais en le nanostructurant localement, on le rend isolant là où on en a besoin. Par contre sa porosité cause des problèmes : mauvaise résistance chimique, structure instable au-delà de 400°C, et tenue mécanique réduite. La facilité d’intégration des semiconducteurs poreux est un atout majeur, nous visons donc de réduire les désavantages de ces matériaux afin de favoriser leur intégration dans des dispositifs en silicium. Nous avons identifié deux approches
pour atteindre cet objectif : i) améliorer le Si poreux ou ii) développer un nouveau matériau.
La première approche consiste à amorphiser le Si poreux en l’irradiant avec des ions à haute énergie (uranium, 110 MeV). Nous avons montré que l’amorphisation, même partielle, du Si poreux entraîne une diminution de sa conductivité thermique, sans endommager sa structure poreuse. Cette technique réduit sa conductivité thermique jusqu’à un facteur de trois, et peut être combinée avec une pré-oxydation afin d’atteindre une réduction d’un facteur cinq. Donc cette méthode permet de réduire la porosité du Si poreux, et d’atténuer ainsi les problèmes de fragilité mécanique causés par la porosité élevée, tout en gardant un niveau d’isolation égal.
La seconde approche est de développer un nouveau matériau. Nous avons choisi le SiC poreux : le SiC massif a des propriétés physiques supérieures à celles du Si, et donc à priori le SiC poreux devrait conserver cette supériorité. La fabrication du SiC poreux a déjà été démontrée dans la littérature, mais avec peu d’études détaillées du procédé. Sa conductivité thermique et tenue mécanique n’ont pas été caractérisées, et sa tenue en température que de façon incomplète.
Nous avons mené une étude systématique de la porosification du SiC en fonction de la concentration en HF et le courant. Nous avons implémenté un banc de mesure de la conductivité thermique par la méthode « 3 oméga » et l’avons utilisé pour mesurer la conductivité thermique du SiC poreux. Nous avons montré qu’elle est environ deux ordres de grandeur plus faible que celle du SiC massif. Nous avons aussi montré que le SiC poreux est résistant à tous les produits chimiques typiquement utilisés en microfabrication sur silicium. D’après nos résultats il est stable jusqu’à au moins 1000°C et nous avons obtenu des résultats qualitatifs encourageants quant à sa tenue mécanique. Nos résultats signifient donc que le SiC poreux est compatible avec la microfabrication, et peut être intégré dans les MEMS comme isolant thermique. // Abstract : Thermal insulation is essential in several types of MEMS (micro electro-mechanical systems). It can help reduce power consumption, improve performance, and can also isolate the hot area from the rest of the device, which is essential in a system-on-chip. A few materials and techniques currently exist for thermal insulation in MEMS, but these are limited. Indeed, either they don’t have provide a sufficient level of insulation, are too fragile, or restrict design of the device and are difficult to integrate.
A potentially interesting technique for thermal insulation, which has been demonstrated in
the literature, is to make nanometer-scale pores in silicon by electrochemical etching. By
nanostructuring silicon in this way, its thermal conductivity is reduced by a factor of 100 to
1000, transforming it into a thermal insulator. This solution is ideal for integration in existing MEMS fabrication processes, as it is based on the silicon substrates which are already used for their fabrication. By locally nanostructuring these substrates, silicon is made insulating wherever necessary. However the porosity also causes problems : poor chemical resistance, an unstable structure above 400◦C, and reduced mechanical properties. The ease of integration of porous semiconductors is a major advantage, so we aim to reduce the disadvantages of these materials in order to encourage their integration in silicon-based devices. We have pursued two approaches in order to reach this goal : i) improve porous Si, or ii) develop a new material.
The first approach uses irradiation with high energy ions (100 MeV uranium) to amorphise
porous Si. We have shown that amorphisation, even partial, of porous Si leads to a reduction of its thermal conductivity, without damaging its porous structure. This technique can reduce the thermal conductivity of porous Si by up to a factor of three, and can be combined with a pre-oxidation to achieve a five-fold reduction of thermal conductivity. Therefore, by using this method we can use porous Si layers with lower porosity, thus reducing the problems caused by the fragility of high-porosity layers, whilst keeping an equal level of thermal insulation.
The second approach is to develop a new material. We have chosen porous SiC: bulk SiC has exceptional physical properties and is superior to bulk Si, so porous SiC should be superior to porous Si. Fabrication of porous SiC has been demonstrated in the literature, but detailed studies of the process are lacking. Its thermal conductivity and mechanical properties have never been measured and its high-temperature behaviour has only been partially characterised.
We have carried out a systematic study of the effects of HF concentration and current on
the porosification process. We have implemented a thermal conductivity measurement setup using the “3 omega” method and used it to measure the thermal conductivity of porous SiC. We have shown that it is about two orders of magnitude lower than that of bulk SiC. We have also shown that porous SiC is chemically inert in the most commonly used solutions for microfabrication. Our results show that porous SiC is stable up to at least 1000◦C and we have obtained encouraging qualitative results regarding its mechanical properties. This means that porous SiC is compatible with microfabrication processes, and can be integrated in MEMS as a thermal insulation material.
49
Al-Ajili, Adwan Nayef Hameed. "Photoluminescence of nanostructured silicon." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/26999.
Full textAbstract:
The photoluminescence (PL) emitted by porous silicon has been investigated under different conditions of excitation using a pulsed nitrogen laser source, and the continuous tunable DV synchrotron source at Daresbury Laboratory. The project involved sample preparation, and PL measurements using a custom-built optical laser-based system for lifetime measurements. This in itself necessitated software and hardware development to enable interfacing and data-logging using an IBM-compatible PC. The equipment development formed a major part of the project.
50
CALABRESE, Gabriele. "Relaxed germanium epilayers on porous silicon buffers for low dislocation content Ge on Si virtual substrates." Doctoral thesis, Università degli studi di Ferrara, 2015. http://hdl.handle.net/11392/2389093.
Full textAbstract:
While silicon represents the dominant material in the semiconductor industry, the continuous improvement in the performance of Si based devices is reaching its upper bound due to the approaching of insuperable physical limitations intrinsic to Si, which requires the introduction of new semiconductor materials and the development of new assembly techniques to guarantee the future performance improvement and reduction in fabrication costs. The integration of high-quality germanium epilayers on Si substrates has received great attention from the semiconductor community due to the chance to extend the range of performance offered by Si-based technology by taking advantage of both the superior properties of Ge such as a higher carrier mobility, a lattice constant close to that of GaAs which enables III-V epitaxy and a quasi-direct bandgap, and of the possibility of strain and bandgap engineering offered by the formation of a heterojunction.
To overcome the 4.2% lattice constant mismatch existing between Ge and Si which hamper the direct integration approach, this thesis investigates a novel technique for the realization of high-quality Ge on Si virtual substrates (VSs), consisting in the introduction of a porous silicon (pSi) buffer layer in between Ge and Si. pSi is a versatile, self-assembled, nanomaterial which can be realized at very high growth rates through electrochemical etching of Si. Thanks to its reduced Young’s and shear moduli pSi can deform during epitaxy, potentially alleviating part of the lattice mismatch between Ge and Si and reducing the density of misfit dislocations and associated threading segments necessary for complete Ge relaxation. Together with the very high throughput of the anodization process, other fundamental advantages of the proposed approach are its low cost, its simple scalability to large area Si substrates and the possibility to lift-off the grown epilayers from the starting substrates, giving Ge on pSi VSs the possibility to outperform other existing techniques for Ge integration on Si.
During the course of this work, several Ge on pSi VSs have been grown through low energy plasma enhanced chemical vapor deposition (LEPECVD) technique, and the resulting crystalline quality has been compared to that of Ge on Si VSs. Using X-ray diffraction techniques, together with electron microscopy analysis and selective etching techniques, it will be shown how the main physical parameters of pSi buffers affect the crystalline quality of Ge heteroepilayers. Finally, it will be demonstrated that strong threading dislocation reduction is possible in Ge grown on low porosity pSi buffers compared to Ge on bulk Si, at parity of experimental conditions, and the main mechanisms responsible for crystalline quality improvement in Ge grown on pSi will be uncovered.