Bibliografías temáticas / Porous silicas

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Literatura académica sobre el tema "Porous silicas"

Autor: Grafiati
Publicado: 25 de mayo de 2024

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Artículos de revistas sobre el tema "Porous silicas"

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Yan, Xiang, Aurélie Cayla, Eric Devaux y Fabien Salaün. "Microstructure Evolution of Immiscible PP-PVA Blends Tuned by Polymer Ratio and Silica Nanoparticles". Polymers 10, n.º 9 (17 de septiembre de 2018): 1031. http://dx.doi.org/10.3390/polym10091031.

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Composites of polypropylene (PP) and water soluble poly(vinyl alcohol) (PVA) can become an environmentally friendly precursor in preparing porous material, and their biphasic morphology needs to be manipulated. In this work, PP-PVA extrudates were prepared with a twin-screw extruder, and different PP/PVA ratios were employed to manipulate the morphology of the blends. Afterwards, different silicas were imbedded within the blends to further regulate the biphasic microstructure. PVA continuity, as a vital parameter in obtaining porous material, was determined by selective extraction measurement, and PP-PVA biphasic morphology was characterized by scanning microscopy analyses (SEM). Rheological measurement was also performed to correlate the microstructure evolution of the blends. First, it was found that with the increment of PVA proportion, PVA continuity is raised gradually, and the microstructure of blends containing 40–50 wt % of PVA is approaching co-continuous. Second, the localization of silicas was predicted based on the wettability of silica and polymers, and it was also confirmed by TEM that different silicas showed selective distribution. It is inspiring that R972 nanoparticles were found mainly distributed at the interface, which gives a possibility in preparing a surface-modified porous material. The shape distribution and average size of PVA nodules were examined by analyzing the SEM images. It is indicated that silicas with different wettabilities play disparate roles in tuning the biphasic microstructures, leading to heterogeneous PVA continuity.
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Choma, Jerzy y Mietek Jaroniec. "Adsorption Potential Distributions for Silicas and Organosilicas". Adsorption Science & Technology 25, n.º 8 (octubre de 2007): 573–81. http://dx.doi.org/10.1260/0263-6174.25.8.573.

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Adsorption potential distributions (APDs) were calculated from nitrogen adsorption isotherms for macroporous silicas, and for disordered and ordered mesoporous silicas without and with organic groups attached to the surface. It was shown that the APDs for porous silicas and organosilicas differ significantly from those obtained for carbonaceous materials, especially in the range of high adsorption potentials which correspond to low relative pressures. Although the high adsorption potential portions of APDs for porous siliceous materials are less informative than those for carbons, they are still useful for monitoring the changes in the surface properties due to the attachment of various organic groups.
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Weinberger, Christian, Tatjana Heckel, Patrick Schnippering, Markus Schmitz, Anpeng Guo, Waldemar Keil, Heinrich C. Marsmann, Claudia Schmidt, Michael Tiemann y René Wilhelm. "Straightforward Immobilization of Phosphonic Acids and Phosphoric Acid Esters on Mesoporous Silica and Their Application in an Asymmetric Aldol Reaction". Nanomaterials 9, n.º 2 (12 de febrero de 2019): 249. http://dx.doi.org/10.3390/nano9020249.

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The combined benefits of moisture-stable phosphonic acids and mesoporous silica materials (SBA-15 and MCM-41) as large-surface-area solid supports offer new opportunities for several applications, such as catalysis or drug delivery. We present a comprehensive study of a straightforward synthesis method via direct immobilization of several phosphonic acids and phosphoric acid esters on various mesoporous silicas in a Dean–Stark apparatus with toluene as the solvent. Due to the utilization of azeotropic distillation, there was no need to dry phosphonic acids, phosphoric acid esters, solvents, or silicas prior to synthesis. In addition to modeling phosphonic acids, immobilization of the important biomolecule adenosine monophosphate (AMP) on the porous supports was also investigated. Due to the high surface area of the mesoporous silicas, a possible catalytic application based on immobilization of an organocatalyst for an asymmetric aldol reaction is discussed.
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Ramsay, John D. F. y Christiane Poinsignon. "Neutron scattering investigations of porous silicas and water silica interfaces". Langmuir 3, n.º 3 (mayo de 1987): 320–26. http://dx.doi.org/10.1021/la00075a006.

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Charmas, Barbara, Karolina Kucio, Volodymyr Sydorchuk, Svitlana Khalameida, Magdalena Zięzio y Aldona Nowicka. "Characterization of Multimodal Silicas Using TG/DTG/DTA, Q-TG, and DSC Methods". Colloids and Interfaces 3, n.º 1 (28 de diciembre de 2018): 6. http://dx.doi.org/10.3390/colloids3010006.

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The formation of hierarchical, multimodal porosity materials with controlled shape and size of pores is the essential challenge in materials science. Properties of silica materials depend largely on different features: crystal structure, dispersity, surface composition, and porosity as well as the method of preparation and possible modification. In this paper, multimodal silicas obtained using different additives are presented. A-50 and A-380 aerosils and wide-porous SiO2 milled at 300 rpm were used as the additives in the sol stage at 20 °C, the sol–gel stage followed by hydrothermal modification (HTT) at 200 °C, or in the mechanochemical treatment (MChT) process. The characterizations were made by application of N2 adsorption/desorption, SEM imaging, quasi-isothermal thermogravimetry (Q-TG), dynamic thermogravimetry/derivative thermogravimetry/differential thermal analysis (TG/DTG/DTA), and cryoporometry differential scanning calorimetry (DSC) methods. Results showed that such a one-step preparation method is convenient and makes it possible to obtain multimodal silicas of differentiated porous structures and surface chemistry.
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Hustings, A. M. L. y J. J. F. Scholten. "The Effect of Pressure on Pore Structure in Mercury Porosimetry". Adsorption Science & Technology 4, n.º 4 (diciembre de 1987): 241–50. http://dx.doi.org/10.1177/026361748700400404.

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The pore volume distributions of chrysotile, Mg3(OH)4. Si2O5, ZrO2 and of four samples of silica with pore volumes from 1.45 to 2.70 cm3/g have been measured by means of nitrogen capillary condensation and mercury penetration. It is shown that compaction of the porous structures can occur under the influence of the high mercury pressures applied. The degree of compaction depends on the mechanical strength of the sample, its initial porosity and the magnitude of the mercury pressure. The extremely strong ZrO2 sample, with its low pore volume of 0.18 cm3/g does not show any sign of cracking up to pressures as high as 190 MPa. Hollow chrysotile needles compact in the pressure range from 100 to 400 MPa. Highly porous silicas all show severe compaction. In accordance with Brown & Lard (Brown & Lard, 1974) it is concluded that silicas with pore volumes larger than 1.2 cm3/g are not suitable for study by mercury porosimetry.
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Gorgol, Marek, Agnieszka Kierys y Radosław Zaleski. "Positron Lifetime Annihilation Study of Porous Composites and Silicas Synthesized Using Polymer Templates". Defect and Diffusion Forum 373 (marzo de 2017): 280–83. http://dx.doi.org/10.4028/www.scientific.net/ddf.373.280.

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The porous structure of polymer-silica composites, based on three polymer templates, which differ in a porosity and hydrophobicity, was examined using positron annihilation lifetime spectroscopy. Additionally, the investigation of silicas obtained after removal of polymers during calcination of composite materials, was performed. In composites based on hydrophobic polymers, silica condensates only in larger free volumes, while SiO2 deeply penetrates spaces between polymer chains, when the template is polar. Moreover, the structure of the silica gel, obtained after polymer removal, depends on chemical character of the template, rather than its porosity.
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Crean, Abina M., Robert J. Ahern, Rakesh Dontireddy, Walid Faisil, John P. Hanrahan, Brendan T. Griffin y Katie B. Ryan. "Porous Silicas for Enhanced Drug Release". Advances in Science and Technology 91 (octubre de 2014): 79–81. http://dx.doi.org/10.4028/www.scientific.net/ast.91.79.

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Low drug water-solubility is a major challenge to overcome in the development of tablet or capsule dosage forms for a large number of promising drug candidates. Strategies to improve drug solubility and dissolution involve chemical, physical and formulation approaches. An emerging formulation approach to increase drug dissolution and solubility involves the creation of solid dispersions of drug molecules on to a high surface area inorganic carrier, such as porous silica. The combined benefits of a hydrophilic inorganic substrate, increased drug surface area and a high-energy drug form facilitate rapid drug dissolution into aqueous based media and can create supersaturated drug solutions. The work presented provides a brief overview of the silica grades investigated, processes employed to load drugs onto the silica substrates, provide some examples of the ability of silica to enhance drug dissolution and highlight some of the challenges in the development of these novel drug delivery systems.
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BENEDETTI, A., S. CICCARIELLO, F. PINNA y G. STRUKUL. "SAXS study of coated porous silicas". Le Journal de Physique IV 03, n.º C8 (diciembre de 1993): C8–463—C8–466. http://dx.doi.org/10.1051/jp4:1993896.

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Guiton, T. A. y C. G. Pantano. "Infrared reflectance spectroscopy of porous silicas". Colloids and Surfaces A: Physicochemical and Engineering Aspects 74, n.º 1 (julio de 1993): 33–46. http://dx.doi.org/10.1016/0927-7757(93)80396-v.

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Tesis sobre el tema "Porous silicas"

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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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3

Lazaro, A., J. W. Geus y 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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4

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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5

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
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.
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
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
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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9

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
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
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.
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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Libros sobre el tema "Porous silicas"

1

Chuan, Feng Zhe y Tsu Raphael, eds. Porous silicon. Singapore: World Scientific, 1994.

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2

Stiebahl, Korinna Christine. Porous anodised silicon. Birmingham: University of Birmingham, 1991.

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T, Canham Leigh y INSPEC, eds. Properties of porous silicon. London: INSPEC, 1987.

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T, Canham Leigh y INSPEC (Information service), eds. Properties of porous silicon. London: INSPEC, 1997.

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Canham, Leigh, ed. Handbook of Porous Silicon. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-319-04508-5.

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Sailor, Michael J. Porous Silicon in Practice. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2011. http://dx.doi.org/10.1002/9783527641901.

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Gardelis, S. Light emission from porous silicon. Manchester: UMIST, 1993.

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8

Vial, Jean-Claude y Jacques Derrien, eds. Porous Silicon Science and Technology. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-662-03120-9.

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Santos, Hélder A. Porous silicon for biomedical applications. Amsterdam: Elsevier/WP Woodhead Publishing, Woodhead Publishing is an imprint of Elsevier, 2014.

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Koker, Lynne. Photoelectrochemical formation of porous silicon. Birmingham: University of Birmingham, 2001.

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Capítulos de libros sobre el tema "Porous silicas"

1

Kenny, Martyn B. y Kenneth S. W. Sing. "Adsorptive Properties of Porous Silicas". En Advances in Chemistry, 506–15. Washington DC: American Chemical Society, 1994. http://dx.doi.org/10.1021/ba-1994-0234.ch025.

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Unger, K. K. "Surface Structure of Amorphous and Crystalline Porous Silicas". En Advances in Chemistry, 165–81. Washington DC: American Chemical Society, 1994. http://dx.doi.org/10.1021/ba-1994-0234.ch008.

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Drake, J. M., J. Klafter y P. Levitz. "Studies on the Structure of Porous Silicas: The Fractal Dilemma". En The Jerusalem Symposia on Quantum Chemistry and Biochemistry, 379–86. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-4001-7_33.

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Canham, Leigh. "Porous Silicon Formation by Porous Silica Reduction". En Handbook of Porous Silicon, 1–8. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04508-5_8-1.

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Canham, Leigh. "Porous Silicon Formation by Porous Silica Reduction". En Handbook of Porous Silicon, 1–12. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-04508-5_8-2.

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Canham, Leigh. "Porous Silicon Formation by Porous Silica Reduction". En Handbook of Porous Silicon, 85–92. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-05744-6_8.

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Canham, Leigh. "Porous Silicon Formation by Porous Silica Reduction". En Handbook of Porous Silicon, 99–109. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-71381-6_8.

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Courtens, Eric y René Vacher. "Porous Silica". En Amorphous Insulators and Semiconductors, 255–88. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-015-8832-4_12.

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Edler, Karen J. "Mesoporous Silicates". En Porous Materials, 69–145. Chichester, UK: John Wiley & Sons, Ltd, 2010. http://dx.doi.org/10.1002/9780470711385.ch2.

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Bettotti, Paolo. "Porous Silicon". En Springer Handbook of Nanomaterials, 883–902. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-20595-8_24.

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Actas de conferencias sobre el tema "Porous silicas"

1

PIKUS, S., E. OLSZEWSKA y M. KOZAK. "SAS CHARACTERIZATION OF ORGANIC FILM DEPOSITED ON POROUS SILICAS". En Proceedings of the XIX Conference. WORLD SCIENTIFIC, 2004. http://dx.doi.org/10.1142/9789812702913_0069.

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Suciu, Claudiu Valentin. "Experimental Investigations on the Nano-Damping Durability". En 2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems. ASMEDC, 2008. http://dx.doi.org/10.1115/micronano2008-70018.

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Connected to the nano-technological development, solid-liquid interfaces have been used to dissipate surface energies, in systems where the solid is liquid-repellent. Such interfaces are able to store, release or transform the mechanical energy. For instance, some modified silicas and zeolites in association with water have been used to build efficient ecological dampers and springs. Regarding this attractive kind of storage and loss of energy, some practical aspects, such as the endurance limits need to be clarified, and measures to augment the nano-damping durability to values required by usual machine elements (106−107 working cycles) await validation. Thus, in this work endurance tests are performed on nano-porous silica gel micro-particles by using a compression-decompression chamber. When the colloidal mixture of water and silica gel was supplied directly into the test chamber, the nano-damping performances abruptly reduced at augmentation of the number of working cycles due to the colloid leakage at the seals. Such severe leakage occurred since the clearance between the piston and cylinder (hundreds of microns), prescribed by the seals makers, was one order of magnitude larger than the diameter of silica gel particles (tens of microns); accordingly, a few layers of silica gel penetrated the gap, producing damage by abrasive wear of the seals and even of the piston surface during about 105 working cycles. In order to augment the nano-damping durability, colloidal mixture of water and silica gel is introduced inside of a tank that is separated by micro-filters from the main cylinder, in which only water is supplied. One discusses the influence of filtration on the nano-damping performances and the variation of durability versus the ratio of the filter pore’s diameter to the mean size of the silica gel particles. During a few working cycles the silica gel grains are not damaged, since the uniform pressure distribution in the liquid surrounding the particles prevent them from premature fracture, even at high-pressurization. However, silica gel grains that undergo gradually fatigue fracture are able to pass the filter and then, to escape at the test chamber seals; this produces a continuous reduction of the silica gel quantity inside of the pressurization chamber and accordingly, a proportional reduction of dissipation. On a logarithmic scale, a slight linear decreasing of the damping occurs until a critical number of working cycles; this is followed by an abrupt linear reduction of dissipation, with a slope that decreases when the diameter of the filter orifices is diminished. Despite the undesired decreasing of the nano-damping performances at augmentation of the number of working cycles, using appropriate filters the durability can be extended to reach the required life of an actual machine element.
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Yao, Shuhuai, Alan M. Myers, Jonathan D. Posner y Juan G. Santiago. "Electroosmotic Pumps Fabricated From Porous Silicon Membranes". En ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-61350.

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Large flow rates per applied potential are obtained from electroosmotic (EO) pumps fabricated from n-type porous silicon. Porous silicon membranes have ideal geometries for EO pumping. These membranes have hexagonally packed, uniform pores with near-unity tortuosity and are well suited to maximize flow rate for a given applied voltage. The 350 μm thick membranes were passivated with a SiO2 layer and exhibit a maximum flow rate of 1.2 ml/min/cm2/V. This is 4.4 times higher than previously demonstrated silica-based frit EO pumps. LPCVD polysilicon deposition followed by wet oxidation was used to control the pore size. The impact of these coatings on the pump performance has also been characterized.
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El Moutaouakil, Amine, Mahmoud Al Ahmad, Abdul Kareem K. Soopy y Adel Najar. "Porous Silicon NWs with FiTC-doped Silica Nanoparticles". En 2021 6th International Conference on Renewable Energy: Generation and Applications (ICREGA). IEEE, 2021. http://dx.doi.org/10.1109/icrega50506.2021.9388287.

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Fang, Jin, Laurent Pilon, Chris B. Kang y Sarah H. Tolbert. "Thermal Conductivity of Ordered Mesoporous Silicon Thin Films Made From Magnesium Reduction of Polymer Templated Silica". En ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-64784.

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This paper reports the cross-plane thermal conductivity of ordered polycrystalline mesoporous silicon thin films between 30 and 320 K. The films were produced by a combination of evaporation induced self-assembly (EISA) of mesoporous silica followed by magnesium reduction. The periodic ordering of pores in mesoporous silicon was characterized by a combination of 1D X-ray diffraction, 2D small angle X-ray scattering, and direct SEM imaging. The average crystallite size, porosity, and film thickness were about 13–18 nm, 25–35%, and 140–260 nm, respectively. The pores were arranged in a face-centered cubic lattice. Finally, the cross-plane thermal conductivity of the meso-porous silicon thin films was measured using the 3ω method. The measured thermal conductivity was about 3 to 5 orders of magnitude smaller than that of the bulk dense crystalline silicon for the temperature range considered. The effects of temperature and film thickness on the thermal conductivity were investigated.
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Tamada, Makio y Yuta Sunami. "Establishment of Mass Production Method of Mesoporous Silica Thin Film and Development of Porous Carbon Thin Film Using 1,4-Dihydroxyanthraquinone As Carbon Source". En ASME 2019 28th Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/isps2019-7468.

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Abstract Porous materials typified by mesoporous silica and porous carbon are expected to be applied in various fields such as adsorption, ion exchange, and engineering. In this research, we focused on mesoporous silica thin films and porous carbon thin films. For the mesoporous silica thin film, mass creation method was established the by introducing the roll-to-roll fabrication method. In this method, the pore size could be controlled by changing the molar ratio of the precursor solution, and the thickness of mesoporous silica film is controlled by changing the peripheral speed ratio. In the development of porous carbon thin film, we succeeded to express pores by using 1,4-dihydroxyanthraquinone as a carbon source. X-ray analysis and arithmetic mean roughness measurements were made on the fabricated carbon thin film. As a result, it was confirmed that the porous carbon thin film prepared in this study has a higher specific surface area than the porous carbon thin film synthesized by the conventional manufacturing method.
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Fardad, M. A., Eric M. Yeatman y Emma J. Dawnay. "Porous films for nonlinear silica-on-silicon integrated optics". En SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, editado por John D. Mackenzie. SPIE, 1994. http://dx.doi.org/10.1117/12.188938.

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GAVRILOV, S. A., Yu N. KORKISHKO, V. A. FEDOROV y V. A. KARAVANSKII. "STRUCTURE OF PORES IN THERMALLY OXIDIZED POROUS SILICON WAVEGUIDES". En Reviews and Short Notes to Nanomeeting '99. WORLD SCIENTIFIC, 1999. http://dx.doi.org/10.1142/9789812817990_0078.

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Canham, L. "Porous silicon". En The European Conference on Lasers and Electro-Optics. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/cleo_europe.1994.cwk2.

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RHULE, DAVIN, ANIRBAN MONDAL, MRINAL C. SAHA, LAURA CUMMINGS y THOMAS ROBISON. "EFFECT OF SILICA AND MIXING TIME ON MICROSTRUCTURES OF POROUS POLYMER COMPOSITE BY EMULSION TEMPLATING". En Proceedings for the American Society for Composites-Thirty Eighth Technical Conference. Destech Publications, Inc., 2023. http://dx.doi.org/10.12783/asc38/36668.

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Porous polymer composite with tailored porosity is applied in the myriads of areas such as energy storage, oil/water absorption, bioengineering, and advanced areas of material science. The emulsion templating technology is one of the most popular methods for synthesizing porous polymer composite. It involves solidifying a two-phase mixture of porogen and polymer, then removing porogen to create pores within the continuous emulsion phase by polymerization or curing. The surfactant plays a pivotal role in accomplishing a stable emulsion, a key factor in designing the internal porous structure. This study highlights the effect of silica filler and mixing time on pore morphology, i.e., shape, size, and distribution. on polydimethylsiloxane (PDMS) porous structure utilizing the water-in-oil emulsion templating method. Span® 80 is used as a surfactant to reduce the surface tension between water, silica, and PDMS and simultaneously create a strong foaming effect. Different weight concentrations of silica (1-10 wt%) were chosen while keeping the internal phase, i.e., water (50 wt%) constant. The designed porous structures were further characterized through scanning electron microscopy (SEM). Porous composite specimens fabricated with higher silica content and mixing time consistently exhibit smaller pore sizes than specimens fabricated with lower mixing time and silica content. A breakthrough of pore morphology is seen at silica content higher than 5wt% at 1 min mixing, however, pore morphology drastically changes when mixing time increases from 1 min to 6 min. Variation of finer mixing time beyond 1 min shows stepwise changes in pore morphology from a large single-phase porous structure to a bi-modal porous structure which eventually become a smaller single-mode porous structure. Thus, the emulsion templating technique, in combination with different filler content and mixing time, will effectively aid in designing engineered porous polymer composite with varying stiffness and pore morphology.
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Informes sobre el tema "Porous silicas"

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Penczek, John y Rosemary L. Smith. Electroluminescing Porous Silicon Device. Fort Belvoir, VA: Defense Technical Information Center, agosto de 1995. http://dx.doi.org/10.21236/ada299433.

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Levine, Louis B., Matthew H. Ervin y Wayne A. Churaman. Energy Harvesting from Energetic Porous Silicon. Fort Belvoir, VA: Defense Technical Information Center, julio de 2016. http://dx.doi.org/10.21236/ad1011610.

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Aurora, Peter. Commercially Scalable Process to Fabricate Porous Silicon. Office of Scientific and Technical Information (OSTI), septiembre de 2017. http://dx.doi.org/10.2172/1395497.

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Anderson, R., R. Muller y C. Tobias. Investigation of porous silicon for vapor sensing. Office of Scientific and Technical Information (OSTI), octubre de 1989. http://dx.doi.org/10.2172/5234679.

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Solanki, R. Lighting research - porous silicon phosphors. Final technical report. Office of Scientific and Technical Information (OSTI), julio de 1995. http://dx.doi.org/10.2172/83842.

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Syyuan Shieh. The processing and potential applications of porous silicon. Office of Scientific and Technical Information (OSTI), julio de 1992. http://dx.doi.org/10.2172/7253171.

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Shieh, Syyuan. The processing and potential applications of porous silicon. Office of Scientific and Technical Information (OSTI), julio de 1992. http://dx.doi.org/10.2172/10180756.

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Becker, Collin, Luke Currano y Wayne Churaman. Characterization and Improvements to Porous Silicon Processing for Nanoenergetics. Fort Belvoir, VA: Defense Technical Information Center, febrero de 2009. http://dx.doi.org/10.21236/ada494952.

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Tallant, D. R., M. J. Kelly, T. R. Guilinger y R. L. Simpson. Porous silicon structural evolution from in-situ luminescence and Raman measurements. Office of Scientific and Technical Information (OSTI), mayo de 1996. http://dx.doi.org/10.2172/231693.

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Gupta, P., A. C. Dillon, A. S. Bracker y S. M. George. FTIR Studies of H2O and D2O Decomposition on Porous Silicon Surfaces. Fort Belvoir, VA: Defense Technical Information Center, julio de 1990. http://dx.doi.org/10.21236/ada226581.

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