Dissertationen zum Thema „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.
Der volle Inhalt der QuelleHondow, 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.
Der volle Inhalt der QuelleLazaro, A., J. W. Geus und 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.
Der volle Inhalt der QuelleZhou, 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.
Der volle Inhalt der QuelleZhou, 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.
Der volle Inhalt der QuelleNovel 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
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/.
Der volle Inhalt der QuelleMullite 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.
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.
Der volle Inhalt der QuelleThe 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
Menard, Samuel. „Périphérie triac à base de silicum poreux“. Thesis, Tours, 2014. http://www.theses.fr/2014TOUR4022/document.
Der volle Inhalt der QuelleThis 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
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.
Der volle Inhalt der QuellePhenols 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
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.
Der volle Inhalt der QuelleA 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.
Mueller, Paul S. „Synthesis of silica based porous nanomaterials“. Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1368.
Der volle Inhalt der QuelleKarlsson, Linda. „Biomolecular interactions with porous silicon /“. Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek804s.pdf.
Der volle Inhalt der QuelleWielgosz, R. I. „Electrochemical studies of porous silicon“. Thesis, University of Bath, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296302.
Der volle Inhalt der QuelleBoswell, Emily. „Field emission from porous silicon“. Thesis, University of Oxford, 1997. http://ora.ox.ac.uk/objects/uuid:a4344196-7fc2-4713-b47b-85920b137759.
Der volle Inhalt der QuelleKoker, Lynne. „Photoelectrochemical formation of porous silicon“. Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368290.
Der volle Inhalt der QuelleZheng, Wan Hua. „Photoluminescence study of porous silicon“. HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/138.
Der volle Inhalt der QuelleNgan, Mei Lun. „Photoluminescence excitation of porous silicon“. HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/139.
Der volle Inhalt der QuelleDEMONTIS, VALERIA. „Porous Silicon applications in biotechnology“. Doctoral thesis, Università degli Studi di Cagliari, 2007. http://hdl.handle.net/11584/266040.
Der volle Inhalt der QuelleStupakova, 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.
Der volle Inhalt der QuelleAtradus 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]
Riachy, Philippe. „Hierarchically Porous Silica Materials for the Encapsulation of Molecules of Interest“. Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0013/document.
Der volle Inhalt der QuelleThis 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
Flower, Andrew. „Polymer adsorption at a porous interface“. Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343309.
Der volle Inhalt der QuelleMabrook, Mohammed Fadhil. „Fabrication and characterisation of porous silicon“. Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/19990/.
Der volle Inhalt der QuelleSquire, E. K. „Light emitting microstructures in porous silicon“. Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285287.
Der volle Inhalt der QuelleBen, 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.
Der volle Inhalt der QuelleOrganic 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
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.
Der volle Inhalt der QuelleFowler, 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.
Der volle Inhalt der QuelleFedeyko, 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.
Der volle Inhalt der QuelleNoble, 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.
Der volle Inhalt der QuelleEzzeddine, Zeinab. „Divalent heavy metals adsorption on various porous materials : removal efficiency and application“. Thesis, Poitiers, 2014. http://www.theses.fr/2014POIT2315/document.
Der volle Inhalt der QuelleAccess 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
DeBoer, John Raymond. „Evaluation Methods for Porous Silicon Gas Sensors“. Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4971.
Der volle Inhalt der QuellePap, A. E. (Andrea Edit). „Investigation of pristine and oxidized porous silicon“. Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514277759.
Der volle Inhalt der Quelle余家訓 und 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.
Der volle Inhalt der QuelleBarker, 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.
Der volle Inhalt der QuelleChang, Wai-Kit. „Porous silicon surface passivation and optical properties“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41426.
Der volle Inhalt der Quelle"June 1996."
Includes bibliographical references (leaves 84-85).
by Wai-Kit Chang.
S.M.
To, Wai Keung. „Tunable wavelength from porous silicon-based devices“. HKBU Institutional Repository, 2009. http://repository.hkbu.edu.hk/etd_ra/1094.
Der volle Inhalt der QuelleTsuboi, Takashi. „Structure and Properties of Porous Silicon Surface“. Kyoto University, 1999. http://hdl.handle.net/2433/181681.
Der volle Inhalt der QuelleTobail, Osama. „Porous silicon for thin solar cell fabrication“. Aachen Shaker, 2008. http://d-nb.info/992052904/04.
Der volle Inhalt der QuelleKodumuri, 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.
Der volle Inhalt der QuelleGoubert-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.
Der volle Inhalt der QuelleDithiocarbamate- 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)
Li, Wenle. „Study of Freeze-Cast Porous Silica Nanoparticle-Based Composites“. Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/38770.
Der volle Inhalt der QuellePh. D.
Chen, Chien-Cheng. „OPTICAL MEASUREMENT OF ENVIRONMENTAL URANIUM USING POROUS SILICA MATERIALS“. VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2241.
Der volle Inhalt der QuelleSilva, 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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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.
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.
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.
Der volle Inhalt der QuelleCervantes, 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.
Der volle Inhalt der QuelleThe 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
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.
Der volle Inhalt der QuelleAlvarez, 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.
Der volle Inhalt der QuelleTitle from first page of PDF file (viewed Jan. 13, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 126-141).
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.
Der volle Inhalt der QuelleNewby, Pascal. „Fabrication de semiconducteurs poreux pour améliorer l'isolation thermique des MEMS“. Thèse, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/98.
Der volle Inhalt der QuelleAl-Ajili, Adwan Nayef Hameed. „Photoluminescence of nanostructured silicon“. Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/26999.
Der volle Inhalt der QuelleCALABRESE, 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.
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