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Jakobsson, Lars Klemet. "Distribution of boron between silicon and CaO-SiO2, MgO-SiO2,CaO-MgO-SiO2 and CaO-Al2O3-SiO2 slags at 1600°C." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-24010.
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New energy sources are needed for a sustainable future. Solar cells have a huge potential as a sustainable energy source but further development of this technology is needed for solar cells to become cost-competitive with other energy sources. Silicon produced by metallurgical refining methods has the potential of reducing the cost of crystalline silicon solar cells significantly but boron has proven to be hard to remove from silicon by these methods. Slag refining is however a promising refining method for removal of boron from silicon. The aim of this thesis was to determine accurate data for the distribution of boron between silicon and selected slags. All published values of the distribution coefficient of boron have been critically reviewed in this work. The thermodynamic properties and distribution of other major components of the system have also been reviewed. Several experiments with silicon and CaO-SiO2, MgO-SiO2, CaO-MgO-SiO2 and CaO-Al2O3-SiO2 slags have been conducted at 1600 °C under argon atmosphere. A series of experiments with ferrosilicon and CaO-SiO2 slags have also been carried out. Accurate data for the distribution of boron between silicon and CaO-SiO2, MgO-SiO2, CaO-MgO-SiO2 and CaO-Al2O3-SiO2 slags at 1600 °C has been determined. The distribution of other major slag components between slag and silicon has also been found in these slag systems. The distribution of calcium and boron between ferrosilicon and CaO-SiO2 slags at 1600 °C has been determined. Activities of slag forming components have been determined in the CaO-SiO2, MgO-SiO2 and CaO-MgO-SiO2 systems. The activity coefficient of BO1.5 at infinite dilution in these slags has also been determined. Activity coefficients of calcium, magnesium and aluminium at infinite dilution in silicon and the activity coefficient of calcium and boron at infinite dilution in ferrosilicon have been determined. An alternative equation for mass transfer has been derived and the mass transfer coefficient of boron in a 37.9%CaO-62.1%SiO2 slag has been estimated to be ks = 5.2 · 10-7m/s. The refining efficiency of CaO-MgO-SiO2 slags has been found to be approximately the same independently of slag composition with a distribution coefficient of boron between 2 and 2.5. This also includes the binary CaO-SiO2 and MgO-SiO2 systems. The activity coefficient of BO1.5 at infinite dilution in CaO-MgO-SiO2 slags, including the binary CaO-SiO2 and MgO-SiO2 systems, has been found to follow the activity coefficient of SiO2 where . A linear decrease of the distribution coefficient was found with increasing Al2O3 content in a ternary CaO-Al2O3-SiO2 slag. This has been found to be caused by an increasing activity coefficient of BO1.5 at infinite dilution in slag relative to the activity coefficient of SiO2 where
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Cardoso, William da Silva. "Oxido misto de SiO2/SnO2,SiO2/SnO2/Fosfato : propriedades e aplicações." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249698.
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Orientador: Yoshitaka GushikemTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
Quimica Inorganica
Doutor em Ciências
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Atik, Mohamed. "La cavitation et ses effets dans la synthèse des matériaux composites (SiO2-SiO2) et (SiO2-SiO2)(B2O3) : étude détaillée du processus du frittage et effets des inclusions rigides." Montpellier 2, 1990. http://www.theses.fr/1990MON20205.
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Synthese des gels composites (sio#2-sio#2) et (sio#2-sio#2) (b#2o#3) a partir des dispersions de teos-aerosil et teos-teb-aerosil par les techniques de sonocatalyse. Mise en forme des materiaux resultants et leur conversion en verre par frittage conventionnel. Le frittage des materiaux composites a ete etudie en detail; notamment l'influence des inclusions sur la cinetique de densification. La croissance des filaments de (nh#4cl) (sio#2) a ete observee au cours du sechage de ces gels composites
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Andrianainarivelo, Mahandrimanana. "Homogénéité d'oxydes mixtes SiO2-ZrO2, SiO2-TiO2, TiO2-ZrO2, Al2O3-TiO2 et Al2O3-SiO2 préparés par sol-gel non hydrolytiques." Montpellier 2, 1996. http://www.theses.fr/1996MON20077.
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Dans ce travail, nous avons prepare des oxydes mixtes: sio#2-zro#2, sio#2-tio#2, tio#2-zro#2, al#2o#3-tio#2 et al#2o#3-sio#2 par un procede sol-gel non hydrolytique base sur la condensation des chlorures metalliques et les alcoxydes metalliques ou entre des chlorures metalliques et des donneurs d'oxygene tels que les ethers. Les rendements en oxydes obtenus apres elimination des groupements organiques residuels sont eleves. Edx et icp nous ont permis de montrer que la composition des oxydes finaux dependait directement de la stoechiometrie des precurseurs. L'homogeneite des gels a ete determinee par leur comportement a la cristallisation et par rmn du #2#9si et ir. Les gels bicomposants obtenus par la voie sol-gel non hydrolytique sont homogenes sauf lorsque le taux de titane est superieur a 8. 5% dans le systeme sio#2/tio#2
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Inagaki, Camila Suemi. "Síntese, caracterização e propriedades fotocatalíticas dos nanocompósitos SiO2/TiO2 e SiO2/TiO2/ZnO." Universidade Estadual de Londrina. Centro de Ciências Exatas. Programa de Pós-Graduação em Química, 2014. http://www.bibliotecadigital.uel.br/document/?code=vtls000193784.
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Este trabalho relata a preparação dos materiais nanoestruturados SiO2/TiO2 (ST) e SiO2/TiO2/ZnO (STZ) pelo método sol-gel em catálise ácida. Os materiais ST foram preparados em diferentes proporções de Si:Ti e Si:Ti:Zn. A caracterização dos materiais ST e STZ foi realizada por análises químicas e por diversas técnicas como: microscopia eletrônica de varredura, espectroscopia de energia dispersiva, medida da área superficial específica, refletância difusa, microscopia eletrônica de transmissão em alta resolução, difração de raios-X e espectroscopia Raman. Pela caracterização foi possível constatar que os materiais são nanocristalinos com domínios entre 4 e 5 nm e com característica estrutural microporosa. No material ST foi identificado apenas domínios cristalinos da fase anatase (TiO2), enquanto no material STZ as fases nanocristalinas identificadas foram: a anatase e o rutilo (TiO2), a wurtzita (ZnO), o espinélio invertido titanato de zinco (Zn2TiO4) e na superfície do material STZ com maiores quantidades de Ti e Zn a fase α-quartzo. As propriedades fotocatalíticas destes materiais nanocristalinos foram estudadas utilizando-se corantes têxteis catiônicos e a luz solar natural sem a utilização de oxidantes fortes adicionais. O material STZ na maior proporção Ti:Zn apresentou a maior eficiência fotocatalítica, sendo capaz de degradar totalmente o corante azul de metileno após 30 minutos, o corante amarelo ouro GL após 150 minutos e o corante azul royal GRL após 180 minutos de irradiação solar natural. A mineralização total das moléculas orgânicas em solução aquosa foi confirmada pela análise de carbono orgânico total que mostrou resultado negativo no extrato após a irradiação solar. A cinética de fotodegradação dos corantes têxteis segue o modelo matemático de primeira ordem aparente.This work reports the preparation of the SiO2/ZnO (ST) and SiO2/TiO2/ZnO (STZ) nanocomposites by the sol-gel in acid catalysis method. The ST materials were prepared in different Si:Ti and SI:Ti:Zn proportions. The characterization of the ST and STZ materials was made with chemical analysis and with several techniques such as: scanning electron microscopy, energy-dispersive spectroscopy, measurement of the specific surface area, difuse reflectance, high-resolution transmission electron microscopy, X-ray diffraction and Raman spectroscopy. It was possible with the characterization to verify that the materials are nanocrystalline with domains between 4 and 5 nm and with a microporous structural characteristic. In the ST material only crystalline domains of the anatase phase (TiO2) were identified, while in the STZ material the nanocrystalline phases identified were: anatase and rutile (TiO2), wurtzite (ZnO), the inverted zinc titanate spinel (Zn2TiO4) and in the surface of the STZ material with greater quantities of Ti and Zn in α-quartz phase. The photocatalytical properties of these nanocrystalline materials were studied using cationic textile dyes and natural sunlight without the use of additional strong oxidizers. The STZ material in the greater Ti:Zn proportion presented the greatest photocatalytical efficiency, being capable of completely degrade the methylene blue dye after 30 minutes, the yellow gold GL dye after 150 minutes and the royal blue GRL after 180 minutes of natural sunlight irradiation. The total mineralization of the organic molecules in aqueous solution was confirmed by the total organic carbon analysis which showed negative results in the extract after solar irradiation. The photodegradation kinetics of the textile dyes follows the mathematical model of apparent first order.
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Salvado, Isabel. "Preparação pelo processo "sol-gel" e caracterização de materiais dos sistemas SiO2-ZrO2, SiO2-TiO2 e SiO2-Al2O3. Aplicação como revestimentos protectores." Doctoral thesis, Universidade de Aveiro, 1990. http://hdl.handle.net/10773/15523.
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Stankevič, Marta. "Krūvio pernešimo mechanizmų Al-SiO2-n/Si ir Al-SiO2-n/GaAS dariniuose tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2005. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2005~D_20050616_153138-50492.
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In this work was investigate the charge transport mechanism in Al–SiO2–n/Si and Al–SiO2-n/GaAs formations and compared data of experiment with theory. A lot of works are write about this problem, but the electric current transmit mechanism in this formations is still not clear known. In other works is discrepancy of data witch shows relation between electrics juice and electric field juice or temperature. In this work was carry out an experiment witch could explain what is mechanism in real. The new methods that were used in experiments let us definite get electric field juice in potential barrier and t interaction constant of electron and phonon and density of electrons. The data of real experiment was compared with theoretical data gathered with ‘Mathematica’.
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Rebohle, L. "Lumineszenzeigenschaften ionenimplantierter nanokristalliner SiO2-Schichten." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30099.
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Rebohle, L. "Lumineszenzeigenschaften ionenimplantierter nanokristalliner SiO2-Schichten." Forschungszentrum Rossendorf, 1999. https://hzdr.qucosa.de/id/qucosa%3A21836.
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Cho, Eun Chel Electrical Engineering UNSW. "Optical transitions in SiO2/crystalline Si/SiO2 quantum wells and nanocrystalline silicon (nc-Si)/SiO2 superlattice fabrication (Restricted for 24 months until Feb. 2006)." Awarded by:University of New South Wales. Electrical Engineering, 2003. http://handle.unsw.edu.au/1959.4/22492.
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Innovation in photovoltaic technology may offer cost competitive options to other energy sources and become a viable solution for the energy and environmental challenges of the 21st century. One proposed innovative technology is based on all-silicon tandem cells, which are constructed using superlattices consisting of environmental friendly Si and its compounds. The well and barrier materials in superlattices are restricted to silicon and silicon oxide during the present study. Single crystalline Si/SiO2 quantum wells (QWs) have been fabricated by thermal oxidation of silicon-on-insulator (SOI) wafers. It is found that oxide properties in QWs are important for SOI wafers prepared by the SIMOX (Separation by Implantation of Oxygen) technique. However, QWs fabricated from SOI wafers prepared by the ELTRAN (Epitaxial Layer TRANsfer) approach show the effect of quantum confinement without evidence of strong oxide interfacial transitions. In these wafers, evidence for an apparently ordered silicon oxide was found with 1.92?atomic fringe spacing along the (110) direction of the Si structure and with the thickness about 17?along the (100) direction of the Si structure. Luminescence wavelength ranges are from 700nm to 918nm depending on the Si thickness. The luminescence measurements on other positions of the sample show peak and shoulder spectra, which are explained by monolayer fluctuations in QW thicknesses, previously observed in III-V QWs and II-VI QWs. Si/SiO2 superlattices are fabricated by RF magnetron sputtering. Si density is the key issue in crystallizing the superlattice. High-density Si layers crystallize either under high temperature furnace annealing or rapid thermal process annealing. However, low density Si would not crystallize even at high temperature. Crystallized nanocrystals in the Si layers are observed by high resolution transmission electron microscopy (HRTEM) when the Si layer is thicker than 3nm. When Si layers are thinner than 3nm, the Si layers are discontinuous and finally deteriorate into small nanocrystals. The suitability of such superlattices for surface passivation and antireflection coatings is reviewed. Initial attempts to fabricate heterojunctions between Si wafers and Si/SiO2 superlattices resulted in open circuit voltage of 252mV. However, it is expected that better results would be obtained if Si/SiO2 superlattices were fully crystallized.
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Marr, Robert A. (Robert Allen) 1965. "The Na2O-ZrO2-SiO2 and CaO-ZrO2-SiO2 systems : theoretical petrogenetic grids and synthesis experiments." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56671.
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Fixed-slope P$ rm sb{s}$-$ mu sb{ rm H2O}$ diagrams have been generated for the pseudoternary systems $ rm SiO sb2$-$ rm Na sb2 ZrO sb3$-$ rm H sb2O$ and $ rm SiO sb2$-$ rm CaZrO sb3$-$ rm H sb2O$ as first approximations to P-T phase relations for the Na- and Ca-zirconosilicates, respectively. Two possible topologies were determined for each pseudoternary based on an interchange of stable and metastable invariant points. Although for the $ rm SiO sb2$-$ rm Na sb2 ZrO sb3$-$ rm H sb2O$ system the correct topology cannot yet be resolved, owing to a lack of constraints from experimental and field observations, chemographic analysis reveals that the critical observation would be either the coexistence or incompatibility of the divariant mineral assemblage: elpidite + parakeldyshite.The observed replacement of armstrongite by gittinsite + quartz in the Strange Lake peralkaline complex, Canada, suggests that the preferred topology for the $ rm SiO sb2$-$ rm CaZrO sb3$-$ rm H sb2O$ system may be the one in which the calcium catapleiite-, quartz- and calciohilairite-absent invariant points are stable.
Synthesis experiments in the $ rm SiO sb2$-$ rm CaZrO sb3$-$ rm H sb2O$ system resulted in the formation of the compound $ rm{Ca sb2 ZrSi sb4 O sb{12}}$ as well as zircon, baddeleyite, xonotlite and wollastonite under various conditions, but synthesis of naturally-occurring Ca-zirconosilicates remained elusive.
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Primera, Ferrer Juan. "Synthèse, structure et propriétés de transport des gels composites SiO2-SiO2 : étude expérimentale et simulation." Montpellier 2, 2002. http://www.theses.fr/2002MON20157.
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Bernardes, Arthur Alaím. "Encapsulamento de metalocenos em óxidos binários tipo SiO2-CrO3, SiO2-MoO3 e SiO2-WO3 através do método sol-gel não-hidrolítico : sistemas modificados com grupos organosilanos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/117613.
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Este trabalho relata a síntese e caracterização de materiais à base de sílica (SiO2- CrO3, SiO2-MoO3, SiO2-WO3), com e sem metalocenos encapsulados, usando o processo de sol-gel não-hidrolítico. Os catalisadores foram avaliados na polimerização de etileno e os polímeros formados foram analisados por calorimetria diferencial de varredura (DSC) e cromatografia de permeação em gel (GPC). Investigou-se o efeito da presença de grupos ácidos e/ou grupos orgânicos no catalisador com a atividade catalítica e o efeito dos catalisadores nas reações de polimerização e no polímero gerado. Utilizando o processo sol-gel não-hidrolítico foi possível preparar catalisadores de polimerização de olefinas com características distintas, os quais permitem controlar as propriedades dos polímeros tanto pela alteração da acidez do suporte, quanto pela adição de grupamentos orgânicos na estrutura do mesmo. Tanto a presença de sítios ácidos no suporte (dotados de átomos de Cr, Mo, W), quanto à presença de grupos organo-alcoxisilanos (MTMS, OTES e VTMS) afetam a atividade, pois regulam a quantidade de metaloceno retido ou liberado para o meio reacional. Algumas características dos materiais são bastante dependentes do tipo de metal incorporado à sílica e do tipo de organosilano, tais como: teor de metaloceno encapsulado, área específica e estrutura de rede. Os materiais sintetizados foram caracterizados através de uma série de técnicas analíticas, tais como: Porosimetria de N2, SAXS, MEV, EDX, FTIR, DRS-UV-Vis, Raman, XPS, EXAFS, DPV. O ambiente interno dos poros do suporte apresenta influência sobre a estrutura molecular do metaloceno encapsulado. A maior atividade desses catalisadores está relacionada a uma melhor interação entre o suporte e o sítio ativo do metaloceno. A interação entre o suporte e o metaloceno imobilizado reduz a densidade eletrônica em torno do Zr permitindo a ativação com concentrações mais baixas de co-catalisador. A densidade eletrônica do Zr nos sistemas encapsulados pode ser ajustada tendo como base o tipo de metal (Cr, Mo, W) e o tipo de alcoxisilano incorporado à rede de sílica. De acordo com medidas de XPS, foram observadas energias de ligação do Zr mais altas quando comparadas ao metaloceno não encapsulado. Além disso, a atividade catalítica mostrou uma relação direta com o tamanho e forma dos fractais. Os catalisadores sintetizados produziram polímeros com massa molar média ponderal (Mw) superior àquela obtida com catalisador homogêneo.This work describes the synthesis and characterization of materials (SiO2-CrO3, SiO2-MoO3, SiO2-WO3) with and without entrapped metallocenes using the nonhydrolytic sol-gel process. The catalysts were evaluated in ethylene polymerization and the resulting polymers formed were analyzed by differential scanning calorimetry (DSC) and gel permeation chromatography (GPC). The effect of the presence of acidic groups and/or organic groups in the catalyst with catalytic activity and the effect of the catalysts in polymerization reactions and in the resulting polymer were investigated. Using the non-hydrolytic sol-gel process it was possible to prepare catalysts for olefin polymerization with different characteristics, which allow to control both the properties of the polymer by altering the acidity of the support, and by addition of organic groups in the same structure. Either the presence of acid sites on the support (Cr, Mo, W) or the presences of organo-alkoxysilanes groups (MTMS, OTES and VTMS) affect the activity, by regulating the loaded or released amount of metallocene for the reaction medium. Some characteristics of the material are highly dependent on the type of incorporated metal into silica and on organosilane type, such as metallocene entrapped content, surface area and network structure. The synthesized materials were characterized by complementary techniques, namely nitrogen porosimetry, SAXS, SEM, EDX, FTIR, DRS-UV-Vis, Raman, XPS, EXAFS, DPV. The internal environment of the pores of the support has influenced the molecular structure of the metallocene encapsulated. The highest activity of these catalysts is related to better interaction between the support and the active sites of the metallocene. The interaction between the support and the entrapped metallocene reduce the electron density around the Zr allowing activation at lower concentrations of cocatalyst. The electron density of Zr entrapped systems can be adjusted based on the type of metal (Cr, Mo, W) and the type of alkoxysilane incorporated into the silica network. According to XPS measurements, Zr highest binding energies were observed when compared to free metallocene. In addition, the catalytic activity showed a direct relationship the size and shape of fractals. The synthesized catalysts produced polymers with weight averaged molecular weight (Mw) higher than obtained by homogeneous catalyst.
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Brito, Rafael da Costa. "Síntese e caracterização de nanoestruturas de TiO2/SiO2 E SiO2/TiO2 para aplicação em dispositivos fotoeletroquímicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/151492.
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Neste trabalho apresentamos a síntese e caracterização de nanoestruturas core/shell de TiO2/SiO2 e SiO2/TiO2. Visando aumentar a eficiência de DSSC’s, foi investigado o efeito das interfaces SiO2|TiO2 na diminuição de defeitos estruturais (trapping states) no TiO2, sem resultar no bloqueio da transferência de carga entre as partículas no fotoanodo. Foram obtidas nanoestruturas sintetizadas por diferentes períodos, pH, e tratamentos térmicos utilizando-se cores cristalinos e amorfos de SiO2 e TiO2. As amostras foram caracterizadas por Microscopia Eletrônica de Transmissão, UV-VIS, FTIR-ATR, Difratometria de Raios-X, Cronopotenciometria, Voltametria Linear e Impedância. Foram obtidos cores de TiO2 de cerca de 30 nm de diâmetro e shells de SiO2 de cerca de 5 nm de espessura, também obtivemos cores de SiO2 de 10 e 70 nm em diâmetro e encapsuladas com shell de TiO2 de 5 nm de espessura. Os resultados obtidos mostraram que há uma influência da fase polimorfica do material componente do core na fase polimorfica do material que compõe o shell, havendo um significativo retardo nas temperaturas de mudança de fase. Observou-se também uma correlação da fase polimórfica do TiO2 e a camada de SiO2 no bandgap das amostras. Constatamos que estruturas core/shell são eficientes na passivação de defeitos superficiais, embora a espessura da camada isolante deva ser controlada para não influenciar nos parâmetros elétricos do dispositivo.In this work, we present the synthesis and characterization of core/shell structures of TiO2/SiO2 and SiO2/TiO2 nanoparticles. Aiming to improve the efficiency of DSSCs, the effect of SiO2|TiO2 interfaces to reduce the amount of trapping states on TiO2, without blocking charge transfer among nanoparticles across the photoanode, was investigated. Nanostructures were obtained trough different reaction periods, pH and thermal treatment temperatures using crystalline and amorphous cores of TiO2 and SiO2. The samples were characterized by transmission electron microscopy, UV-Vis, x-ray diffractometry, chronopotentiometry, linear sweep voltammetry and electrochemical impedance spectroscopy. TiO2 cores of ca. 30 nm in diameter were obtained an were encapsulated with a 5 nm thick SiO2 shell. SiO2 cores of ca. 70 nm in diameter were obtained and encapsulated in ca. 5 nm thick TiO2 shell. The results show an influence of polymorphic phase of the core material on the polymorphic phase of the shell material, resulting in a significative change in the phase transition temperatures. It was also determined a correlation between the polymorphic phase of TiO2 and the insulator layer on the samples bandgap. Finally we show that, even though core/shell structures are efficient in trapping states passivation, the thickness of the insulator layer must be controlled in order to not jeperdize the electric parameters of the photoelectrochemical device.
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Hutlová, Alzbeta. "Preparation fo magnetic nanocomposites spinel/SiO2 and garnet/SiO2 by sol-gel method and their characterization." Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13229.
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Lira, Claudia. "Obtenção de esmaltes vitrocerâmicos de elevado desempenho nos sistemas MgO-Al2O3-SiO2 e CaO-Al2O3-SiO2." Florianópolis, SC, 2002. http://repositorio.ufsc.br/xmlui/handle/123456789/84173.
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Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência e Engenharia de Materiais.Made available in DSpace on 2012-10-20T06:57:41Z (GMT). No. of bitstreams: 0Bitstream added on 2014-09-26T02:20:11Z : No. of bitstreams: 1 190170.pdf: 33566657 bytes, checksum: c675bd5bf55bac6ed81d265a5a165e9b (MD5)
Este trabalho estudou a viabilidade tecnológica de obtenção de esmaltes vitrocerâmicos de elevado desempenho, caracterizando uma alta resistência à abrasão, resistência ao manchamento e ao ataque químico. Inicialmente, procedeu-se à seleção de composições adequadas para a obtenção de fritas. Esta seleção foi realizada a partir de sistemas com cristalização de fases de alta dureza e baixo coeficiente de dilatação térmica, além da facilidade de obtenção e utilização industrial das matérias-primas. Foram investigadas diversas composições nos sistemas MgO-Al2O3-SiO2 e CaO-Al2O3-SiO2, com relação ao seu comportamento térmico de sinterização e cristalização, caracterização microestrutural e dilatométrica. Foram selecionadas duas composições com características mais adequadas à obtenção de esmaltes, segundo os critérios: formação das fases cristalinas cordierita e anortita, baixa porosidade e coeficiente de dilatação térmica adequado aos suportes cerâmicos comerciais. As composições selecionadas para a obtenção de fritas foram: Mg-C2 7% Na2O (composição aproximada: 20%MgO, 24%Al2O3, 49%SiO2, 7%Na2O, % em massa), do sistema MgO-Al2O3-SiO2 e Ca-Z1 do sistema CaO-Al2O3-SiO2 (composição aproximada: 31%CaO, 13%Al2O3, 52%SiO2, 4%ZnO, % em massa). As fritas obtidas a partir das composições selecionadas foram utilizadas na formulação de esmaltes e aplicadas sobre suportes cerâmicos de grês-porcelanato para monoqueima. Para a definição dos parâmetros mais adequados de formulação do esmalte e condições de tratamento térmico foram realizados diversos testes de aplicação, segundo um delineamento experimental pelo método Taguchi. Os esmaltes testados foram avaliados com relação às características visuais, porosidade, medidas de dureza ao risco, dureza Vickers e dureza Mohs. O esmalte obtido a partir da frita Mg-C2 7% Na2O, utilizando queima à temperatura máxima de 1200°C obteve o melhor desempenho na avaliação. Este esmalte apresentou características de elevada dureza ao risco (» 15 GPa), baixa porosidade (» 2%), elevada resistência à abrasão (PEI 5), ao manchamento (classe 5) e ao ataque químico (classe GA e GLA). Estas características se mostraram compatíveis e, em muitos casos, superiores a outros materiais como vitrocerâmicos sinterizados, granito, grês-porcelanato e revestimento para piso classe PEI 5, utilizados como referência. Desta forma, o esmalte vitrocerâmico desenvolvido demonstrou características adequadas a um revestimento cerâmico de alto desempenho, com viabilidade de obtenção segundo os processos convencionais de produção em monoqueima de revestimentos cerâmicos esmaltados.
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Canevari, Thiago da Cruz 1980. "Construção de sensores eletroquímicos utilizando como matriz materiais cerâmicos SI 'O IND. 2'/ 'M IND. X' 'O IND. Y', e materiais cerâmicos eletricamento condutores SI 'O IND. 2'/ C/'M IND. X' 'O IND. Y', preparados pelo processo sol-gel." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249700.
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Orientador: Yoshitaka GushikemTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Este trabalho tem como objetivo sintetizar e caracterizar três materiais diferentes obtidos pelo processo sol-gel: SiO2/SnO2, SiO2/SnO2/Sb2O5 e o filme de Nb2O5 formado sobre a superfície do material cerâmico SiO2/C e utilizá-los como matriz no desenvolvimento de sensores eletroquímicos. O óxido misto, SiO2/SnO2, foi sintetizado utilizando como fonte de SnO2, SnCl4.5H2O, utilizando diferentes catalisadores ácidos HCl e HF (F-). As diferenças estruturais e morfológicas apresentadas pelos óxidos mistos, SiO2/SnO2, em virtude do uso de diferentes catalisadores ácidos, foram investigadas por meio das isotermas de adsorção/dessorção de N2, espectroscopia de fluorescência de raios X, difração de raios X, espectroscopia na região do infravermelho, microscopia eletrônica de transmissão, espectroscopia fotoeletrônica de raios X (XPS), medidas de condutividade elétrica e medidas eletroquímicas visando a utilização destes óxidos mistos como matriz suporte para desenvolvimento de sensores eletroquímicos. O material, SiO2/SnO2/Sb2O5, foi obtido por meio da incorporação do Sb2O5 sobre a superfície do óxido misto, SiO2/SnO2, previamente sintetizado utilizando como fonte de SnO2, o dibutildiacetato de estanho. Este recobrimento foi realizado utilizando, CH2Cl2 seco, em atmosfera inerte, pela técnica de "Enxerto¿. O material, SiO2/SnO2/Sb2O5, foi caracterizado por meio da isoterma de adsorção/dessorção de N2, espectroscopia de fluorescência de raios X, microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e espectroscopia fotoeletrônica de raios X (XPS). Sobre este material foi imobilizado o corante catiônico, azul de meldola, no qual foi preparado um eletrodo de disco rígido com objetivo de estudar a eletrooxidação do cofator NADH utilizando as técnicas de voltametria cíclica e cronoamperometria visando o desenvolvimento de um biossensor eletroquímico. A formação do filme de Nb2O5 sobre a superfície do material carbono cerâmico SiO2/C, utilizando a técnica de spin-coating, foi realizado após o material SiO2/C ser sintetizado utilizando o processo sol-gel. O filme de Nb2O5 preparado foi caracterizado utilizando a técnica de microscopia eletrônica de varredura (MEV), espectroscopia de energia dispersiva (EDS) e espectroscopia fotoeletrônica de raios X (XPS). Com este material foi preparado um eletrodo de disco rígido com objetivo de estudar a eletrooxidação dos isômeros fenólicos, hidroquinona e catecol na presença de resorcinol utilizando a técnica de voltametria de pulso diferencial
Abstract: This work describes the synthesis and characterization of three different materials: SiO2/SnO2, SiO2/SnO2/Sb2O5 and the film of Nb2O5 formed on the surface of the ceramic material SiO2/C obtained by sol-gel process and to use them as matrix in the development of electrochemical sensors. The mixed oxides, SiO2/SnO2, were synthesized using as source of SnO2, SnCl4.5H2O, using different acid catalysts HCl and HF (F). The structural and morphological differences provided by mixed oxides, SiO2/SnO2, due to the use of different catalysts were evaluated by using several like area superficial BET technique, ray X fluorescence spectroscopic, ray X diffraction, IV spectroscopic, transmission electron microscopic (TEM), ray X spectroscopic photoelectron excited (XPS) and electrical conductivity and electrochemical measurements in order to use these mixed oxides as matrix support for development of electrochemical sensors. The material SiO2/SnO2/Sb2O5 was obtained by incorporation of Sb2O5 on the surface of the mixed oxide SiO2/SnO2, previously synthesized using as source of SnO2, dibutildiacetate of tin. This coating was performed using, CH2Cl2 dry, in inert atmosphere, using the technique of "Grafting." The SiO2/SnO2/Sb2O5 material was characterized using area superficial BET technique, ray X fluorescence spectroscopic, scanning electron microscopic (SEM), energy dispersive spectroscopic (EDS) and ray X spectroscopic photoelectron excited (XPS). On this material was immobilized on the cationic dye Meldola Blue, which was prepared in a rigid disk electrode to study the electrooxidation of the cofactor NADH using cyclic voltammetry and chronoamperometry technique for the development of an electrochemical biosensor. The formation of Nb2O5 film on the surface carbon ceramic material SiO2/C, using the technique of spin-coating was carried out after material for SiO2/C is synthesized using the sol-gel process. Nb2O5 film prepared was characterized using scanning electron microscopic (SEM), energy dispersive spectroscopic (EDS) and ray X spectroscopic photoelectron excited (XPS). With this material was prepared a disc rigid electrode in order to study the electrooxidation of phenolic isomers, hydroquinone and catechol in the presence of resorcinol using differential pulse voltammetry technique
Doutorado
Quimica Inorganica
Doutor em Ciências
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Eickhoff, Thorsten. "Photoemissionsuntersuchungen an vergrabenen Grenzschichten SiO2-Si, SiO2-SiC und Thiolen auf Gold mit 3,0-5,5-keV-Röntgenstrahlung." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965866017.
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Gonçalves, José Eduardo. "Estudo, caracterização, propriedade e aplicações do oxido binario SiO2/TiO2 e antimonatos dos oxidos binarios SiO2/TiO2." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249713.
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Orientadores : Yoshitaka Gushikem, Sandra C. de CastroTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
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Latef, Ahmed. "Caractérisation de catalyseurs Mo/SiO2 et Pt-Mo/SiO2 par R. P. E. Et S. P. X." Lille 1, 1987. http://www.theses.fr/1987LIL10014.
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Ben, Kacem Ilyes. "Du cristal au plomb jusqu'aux déchets domestiques : rôle du plomb dans les verres et les vitrocéramiques : étude des systèmes PbO-SiO2, PbO-CaO-SiO2 et PbO-Al2O3-SiO2." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1030/document.
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Ce travail porte sur l’immobilisation du plomb dans les verres et les vitrocéramiques. Le premier volet de cette étude porte sur l’effet de l’incorporation du plomb sur la structure et les propriétés des verres silicatés. Il a été réalisé à partir de compositions de verre simples dans le binaire PbO-SiO2 et les deux ternaires PbO-CaO-SiO2 et PbO-Al2O3-SiO2. Le choix de ces compositions a permis de clarifier le rôle (Modificateur/formateur) du plomb dans ces verres. Des mesures de viscosité, de densité et de la température de transition vitreuse ont été effectuées sur les trois systèmes. Les résultats de ces analyses ont été complétés par des études spectroscopiques (spectroscopies Raman & d’absorption des rayons X) afin de lier les propriétés macroscopiques aux informations structurales dans un ordre à courte- et moyenne-distance. Le deuxième volet de cette étude porte sur la mise en œuvre et la caractérisation de vitrocéramiques obtenues par dévitrification. Les tests de dévitrification ont été effectués principalement sur quelques compositions issues des deux systèmes ternaires PbO-Al2O3-SiO2 et PbO-CaO-SiO2This thesis deals with the immobilization of lead in glasses and glass-ceramics. The first part of this study deals with the effect of the incorporation of lead on the structure and properties of silicate glass. It was conducted on simple glass compositions, in the binary PbO-SiO2 and the two ternaries PbO-CaO-SiO2 and PbO-Al2O3-SiO2. The choice of these compositions made it possible to clarify the role of lead (modifier / former) in these glasses. Measurements of viscosity, density and glass transition temperature were carried out on the three systems. The results of these analysis have been supplemented by spectroscopic studies (Raman and X-ray absorption spectroscopy) in order to link macroscopic properties to structural information in a short- and medium-range order. The second part of this study concerns the implementation and characterization of glass-ceramics obtained by devitrification. The devitrification tests were carried out mainly on some compositions resulting from the two ternary systems PbO-Al2O3-SiO2 and PbO-CaO-SiO2
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Verdaasdonk, Bart Willem. "Physics of trap generation and electrical breakdown in ultra-thin SiO2 and SiON gate dielectric materials." Enschede : University of Twente {Host], 2007. http://doc.utwente.nl/58722.
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Amorim, Camila Almeida. "Efeitos da radiação ionizante nas propriedades de compósitos de poliamida 6 com dióxido de silício coloidal (AEROSIL®)." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/85/85131/tde-07122017-094709/.
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Os polímeros têm sido usados em áreas diferentes, como indústrias automotivas, eletrônicas e de construção civil. A poliamida 6 (PA 6) é um dos principais plásticos de engenharia com aplicações em diversas áreas produtivas, devido as suas propriedades térmicas, mecânicas e a estabilidade dimensional. O objetivo principal deste trabalho foi estudar a potencialidade do uso do dióxido de silício coloidal (SiO2) como carga em substituição ao talco, estudando o efeito da radiação ionizante em suas propriedades. O SiO2 é uma substância amorfa com baixa densidade que tem potencial para ser usado como carga mineral em substituição ao talco na matriz da resina de PA 6. Atualmente o talco é a carga mineral mais utilizada pelas indústrias, por isto vem sofrendo redução de suas reservas ao longo dos anos. Este estudo foi desenvolvido a partir da preparação de um \"masterbeach\" de PA 6 com SiO2. Posteriormente, este \"masterbeach\" foi fracionado em diferentes porcentagens em uma matriz de PA 6. Os corpos de prova das amostras foram processados em uma extrusora dupla rosca, injetados e irradiados no acelerador de elétrons para estudar o efeito da radiação ionizante no compósito de PA 6 com diferentes porcentagens de SiO2. Assim sendo, as propriedades destes compósitos foram analisadas e comparadas com as propriedades das amostras de PA6 com talco. Os resultados mostraram que a utilização do SiO2 como carga para a poliamida 6 é tecnicamente viável, uma vez que suas propriedades foram semelhantes ao compósito de PA 6 com talco. A irradiação dos compósitos estudados apresentou melhorias principalmente nas propriedades térmicas e mecânicas.Polymers have been used in different fields, such as automotive, civil construction and electronics industries. Polyamide 6 (PA 6) is one of the main engineering plastics with several productive applications areas. By the same token, there was an interest in improving their thermal, mechanical and dimensional stability properties. The main objective of this work was to study the potentiality of colloidal silicon dioxide such as filler. According to literature, SiO2 is an amorphous substance with low density. In addition, this material has the potential to be used as a mineral filler to replace the talc in the PA 6 resin matrix. Therefore, SiO2 load was compared to the mineral filler talc which is currently used by industries. Consequently, their reservations are decreasing all over the years. Indeed, these studies were developed from colloidal silicon dioxide with PA 6 the masterbatch elaboration. In addition, the masterbatch was fractionated in different percentages in a PA 6 matrix. It is important to emphasize that all samples were injected and irradiated by an electrons accelerator. Furthermore, the effect of ionizing radiation on the PA 6 composite in different SiO2 percentages was studied. In short, radiation interacts with the polymer by transferring energy to a polymer chain causing modifications that are interfering with its properties. Thus, the mechanical and thermal properties of these composites were measured. In this manner, the irradiation composite studied in that research brought improvements in the thermal and mechanical properties evaluated. In conclusion, results have shown that the use of colloidal silicon dioxide in polyamide 6 composite is technically feasible load to replace talc.
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Chauvin, Jeanne. "Etude de la Structure et des Propriétés Superficielles et Catalytiques des Systèmes WOx/SiO2 et WOx/Ir/SiO2." Caen, 2013. http://www.theses.fr/2013CAEN2037.
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L’objectif de la thèse est d’arriver à une meilleure compréhension du système bifonctionnel métal acide (WOx/Ir/SiO2) par l’examen des propriétés superficielles et catalytiques de ses composantes métal (Ir/SiO2) et acide (WOx/SiO2). Une série de catalyseurs WOx/SiO2 de teneurs variables en W (0 - 2,4 at. W/nm²) obtenue par calcination à 673 K, a été étudiée par XRD, spectroscopies Raman et UV, adsorption de molécules sondes suivie par spectroscopie infrarouge (FTIR) et par test catalytique. Les résultats indiquent que pour des densités superficielles en W inférieures à 1 atome/nm², le W se trouve sous forme d’une phase superficielle. Pour des teneurs en W plus élevées, on observe le développement d’une phase massique amorphe de WO3. Des sites acides de Brønsted relativement forts se forment dès les premiers ajouts de W. L’abondance de ces sites est corrélée à l’activité catalytique en déshydratation de l’isopropanol. Les propriétés des catalyseurs WOx/SiO2 ont été comparées à celles des solides WOx/Al2O3. Le système bifonctionnel (WOx/Ir/SiO2) a été obtenu par le dépôt de la même quantité de W (0,3 at. W/nm²) sur une série de catalyseurs Ir/SiO2 contenant la même teneur en Ir (1 % en masse d’Ir) mais de dispersions variables. La phase métallique a été caractérisée par chimisorption de H2 et de CO, XRD et activité catalytique pour la réaction d’hydrogénation de toluène. Les résultats indiquent que le dépôt de W entraine la même perte d’activité et de capacité de chimisorption de CO (75-80 %) mais ne modifie pas la taille des cristallites d’Ir. Ceci suggère que la chute de l’activité est due au recouvrement partiel de l’Ir par des espèces WOxThe objective of the thesis was to gain some insight into the behavior of bifunctional metal acid system (WOx/Ir/SiO2) by examining the surface structure and catalytic properties of its monofunctional metal (Ir/SiO2) and acid (WOx/SiO2) components. A series of WOx/SiO2 catalysts containing up to 2. 4 at. W/nm² and obtained by low temperature calcination (T = 673 K) was investigated by XRD, Raman and UV spectroscopies, adsorption of probe molecules monitored by infrared spectroscopy (FTIR) and catalytic test. The results indicated that the W surface phase was the only species detected for W surface densities lower than 1 at. W/nm². For higher W content, evidences of the formation of an amorphous WO3 were found. Relatively strong Brønsted acid sites were detected with initial W addition and their evolution with W surface density correlated with the catalytic activity for propan-2-ol dehydration. The behavior of the WOx/SiO2 catalysts was compared with that of the WOx/Al2O3 system. A series of Ir/SiO2 catalysts containing 1 wt % Ir and exhibiting different dispersions was prepared. The bifunctional system WOx/Ir/SiO2 was obtained by W deposition (0. 3 at. W/nm²) on the Ir/SiO2 solids. The Ir metal phase was characterized by H2 and CO chemisorption, XRD Line Broadening and catalytic activity for toluene hydrogenation. A 75-80 % decrease in activity was observed for all solids on W deposition with no concomitant change in the Ir crystallites size. The observed decrease in activity was, however, similar to that measured for CO chemisorption. This suggests that the decline in activity was due to a partial coverage of the Ir metal phase by WOx moieties
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McConkie, Thomas O. "Curious Growth of a Buried SiO2 Layer." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3755.
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Initial investigation of Moxtek wire grid polarizers composed of Al and coated with SiO2 - SiX - SiO2 (where SiX is used to indicate a Si rich layer whose complete composition is not to be disclosed for proprietary reasons) showed a growth of 3x in the inner (closest to Al) SiO2 layer after baking. Upon removing the X and varying rib composition and layering composition and geometries in 12 sets of before and after samples, no obvious growth was observed. Even baking the original unbaked sample yielded no growth. Our data suggest that the initial conclusion of buried oxide growth was flawed and that the observed changes in optical properties upon baking are either very sensitive to layer thicknesses (smaller than we can confidently observe) or due to some other mechanism. Here we present our sample preparation and analysis using the Focused Ion Beam (FIB), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Xray Spectroscopy (EDXS).
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Andrade, Gessie Maria Silva de. "Oxidação parcial de metano a compostos oxigenados (HCHO e CH3OH) sobre catalizadores oxidos MoOx/MgO-SiO2 e VOx-SiO2." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267468.
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Orientador: Gustavo Paim ValençaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: A utilização cada vez maior do gás natural como combustível deve-se ao aumento da demanda de energia nos países em crescimento acompanhado da disponibilidade crescente das reservas de gás em relação às de petróleo, o que pode tomá-Io uma fonte de energia de grande importância neste século XXI. O metano é o componente presente em maior quantidade no gás natural, constituindo mais de 90% da fração dos hidrocarbonetos. Um dos processos mais utilizados para funcionalização das moléculas de hidrocarbonetos, tais como o metano, é a oxidação parcial. Desta forma, no presente estudo foi realizada a oxidação parcial do metano a compostos oxigenados (HCHO e CH30H) a pressão atmosférica utilizando catalisadores de óxidos redutíveis de MoOx/MgO-Si02 e VOx/MgO-Si02 com a finalidade de investigar a influência da introdução de MgO no suporte dos catalisadores e da concentração superficial de Mo+n e V+n na atividade e seletividade destes catalisadores, assim como o efeito da razão CH4:O2 na cinética desta reação. Os óxidos mistos de MgO- Si02 foram preparados em razões atômicas preestabelecidas (Mg:Si = 1:0, 3:1,2:1, 1:1, 1:3, 1:2 e 0:1), secos e calcinados a 400 K por 12 horas e 1050 K por 5 horas, respectivamente. O método para a introdução da fase ativa Mo ou V nos suportes foi a impregnação incipiente, obedecendo-se seis diferentes percentagens em peso de Mo+6 ou V+5 nos sólidos finais: 0,1%, 1,67%, 2,2 %, 3,25%, 4,82%, 6,4%, os quais foram caracterizados por difração de raios-X, adsorção de N2 e adsorção seletiva de O2. Os principais produtos observados para a reação em estudo foram HCHO, CO, CO2, sendo que HCHO e CH30H (produtos de oxidação parcial) foram favorecidos por altas razões molares de CH4:O2. A formação de CH3OH foi observada em teores moderados de óxidos metálicos (0:l[Mg:Si]/0,I%Mo e 0:1[Mg:Si]/3,25%Mo), os quais apresentaram consideráveis seletividades para esse produto (32% e 18%, respectivamente). Os resultados obtidos para as constantes de velocidade demonstraram que para baixas conversões, a seletividade para HCHO se aproxima de 100%, enquanto a seletividade para CO2 se manteve em valores baixos, próximos de zero, mostrando que em condições diferenciais (conversão de CH4 < 10%) a velocidade de formação de HCHO é maior que a velocidade de formação de CO2
Abstract: Methane is the major component of natural gas, often present as more than 90% of the gas. Current1y it is primarily used as a fuel. In the chemical industry it is used in the production of synthesis gas, hydrogen, and in the manufacture of the halogen derivatives of methane, acetylene, hydrogen cyanide, technical carbon, and many other products. The direct conversion of methane to formaldehyde and methanol in a single catalytic step in sufficient1y high yield would give rise to new opportunities in the conversion of natural gas to other useful fuels and chemicals. Both the homogeneous and heterogeneous processes have been studied under various conditions although progress toward obtaining a yield that would make such a process industrially viable has been very slow. The majority of these studies have involved metal oxide catalysts. In this work, the selective oxidation of methane to oxygenated compounds (HCHO e CH3OH) at atmospheric pressure was studied on MoOxfMgO-SiO2 and VOx/MgO-SiO2. The mixed oxides of magnesia and silica were prepared in different atom ratios (Mg:Si = 1:0, 3:1,2:1, 1:1, 1:3, 1:2 or 0:1), dried at 400 K for 12 h and calcined at 1050 K for 5 h. The active phase, Mo (H24Mo7N6O24) or V (H4NO3 V), was added to the supports by the incipient wetness method. The percentages of Mo or V added to the mixed oxides were 0,1%, 1,67%,2,2%,3,25%,4,82% or 6,4%. The solids were characterized by X-ray diffraction, BET surface area and oxygen chemisorption. The objective of the present work was to study the influence of the introduction of MgO in the supports, of the amount of Mo and V on the surface of the supports and of the CH4:O2 molar ratios. Both supported Mo and V oxides were active in the conversion of methane to C1-oxygenates and Cox. The main products of the oxidation reaction were HCHO, CO and CO2. The partial oxidation products (HCHO, CH30H) were favored by high CH4:O2 molar ratios and formaldehyde was the first oxidation product, which was further oxidized to CO. The vanadium oxide catalysts were more active than the molybdenum oxide catalysts in conversion of methane. However, the higher reaction rate also resulted in a further oxidation of HCHO to CO
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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Costa, Zurel Siqueira. "Influência do SiO2 nas propriedades mecânicas da DGEBA." Universidade Federal de Sergipe, 2009. http://ri.ufs.br:8080/xmlui/handle/123456789/3502.
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In this study we used a different route, simple and economical: the dissolution of the SiO2 powder DGEBA with a hardener to base polymercaptan ( aradur 90 ). Analysis was
performed micro hardness in different percentages of the concentration of SiO2. The hardness of multicomponent solid is approximately equal to the average hardness of the
material composition and is also related to the fraction of crystalline phase present in these materials. Since the hardness of the material a decisive factor for its implementation, it is interesting to see how this property varies depending on the composition of multicomponent
solid. Was used to DGEBA Araldite GY 279 and hardener aradur 90 provided by Huntsman. We prepared several samples with different concentrations of SiO2 (3%, 5%, 10%, 20%, 30%, 40% and 50%) compared to the total mass of Araldite-Aradur Mixtures spent 24 hours at ambient temperature and then became a cure at 100 ° C, 120 ° C, 140 ° C, 160 ° C and 180 ° C for 4 h in an oven at ambient pressure. For the determination of hardness, we used a
Shimadzu micro hardness tester equipped with an indenter Vickers. Several tests were performed and it was observed that the micro hardness was a sharp increase with increasing temperature and the concentration of SiO2. This behavior is
associated mainly to the oxidation of the surface and also due to the higher concentration of SiO2, forming a kind of composite with a thermosetting characteristics of high rigidity.
There was a significant growth type reaching a 500 % increase in Vickers hardness between the sample with 50 % SiO2 and pure to a cure of 180 °C. Were also carried out
measurements of elastic modulus and pure sample was obtained a score of 1.65 x107 Pa for the sample with 50 % had a value of 8x107 Pa. The growth of the elastic modulus
accompanied the growth of the hardness, around 480 %.
The presence of SiO2 in the epoxy resin causes a change in the mechanical properties of DGEBA and a concentration of 50% at 180 ° C for a cure for 4 h, a significant increase of the same. It was also observed at high homogeneity powder of silicon oxide to Araldite and Aradur These results indicate that the composite DGEBA/SiO2 can be a good candidate to be used in covering of metals, for example, duct that demand a good hardness.Neste trabalho foi utilizado uma rota diferente, simples e econômica: a dissolução do pó de SiO2 na DGEBA com um endurecedor a base de polimercapitana. Foi feita análise de microdureza nos diferentes percentuais da concentração de SiO2. A dureza em sólidos multicomponentes é aproximadamente igual à média aritmética das durezas dos materiais constituintes e está ainda relacionada com a fração da fase cristalina presentes nestes materiais. Sendo a dureza do material um fator decisivo para a aplicação do mesmo, torna-se interessante verificar como esta propriedade varia em função da composição em sólidos multicomponentes. Foi utilizado a DGEBA Araldite GY 279 e o endurecedor Aradur 90 fornecido pela Huntsman. Foram preparadas diversas amostras com concentrações diferentes de SiO2 (3 %, 5 %, 10 %, 20 %, 30 %, 40 % e 50 % ) em relação a massa total de Araldite-Aradur. As misturas passaram 24 h à temperatura ambiente e depois fez-se uma cura a 100 °C, 120 °C, 140 °C, 160 °C e 180 °C, durante 4 h em uma estufa em pressão ambiente. Para a determinação da microdureza, utilizou-se um microdurômetro da Shimadzu equipado com um identador Vickers. Diversas análises foram realizadas e foi observado que a microdureza teve um crescimento acentuado em função do aumento da temperatura e da concentração de SiO2. Este comportamento está associado, principalmente, à oxidação da superfície e também devido à maior concentração de SiO2, formando uma espécie de compósito com características de um termofixo de alta rigidez. Encontrou-se um crescimento tipo significante chegando a um aumento de 500% na dureza Vickers entre a amostra com 50% de SiO2 e a pura a uma cura de 180 °C. Foram realizadas também medidas do módulo elástico e para amostra pura obteve-se um resultado de 1,65x107 Pa e para a amostra com 50% apresentou um valor de 8x107 Pa. O crescimento do módulo de elasticidade acompanhou o crescimento da dureza, em torno de 480%. A presença do SiO2 na resina epóxi causa alteração nas propriedades mecânicas da DGEBA e que numa concentração de 50 % a 180 °C, durante uma cura de 4 h, houve um aumento significante das mesmas. Foi observado também a alta homogeinidade do pó de óxido de silício com o Araldite e o Aradur. Estes resultados indicam que o compósito DGEBA/SiO2 pode ser um bom candidato para ser utilizado em revestimento de metais, por exemplo, dutos que exijam uma boa dureza.
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Bloess, Harald. "Erzeugung und Charakterisierung von SiO2-Nanostrukturen auf Silizium." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96345286X.
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Wahl, Claudia. "Charakterisierung innerer Grenzflächen in mikrokristallinem SiO2 mit Transmissionselektronenmikroskopie." [S.l.] : [s.n.], 2002. http://elib.tu-darmstadt.de/diss/000197.
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Rubin, P. "Lokalʹnye defektnye sostoi︠a︡nii︠a︡ v SiO2 ploskosti︠a︡kh vysokotemperaturnykh sverkhprovodnikov." Tartu : Tartu ülikool, 1994. http://catalog.hathitrust.org/api/volumes/oclc/33854212.html.
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Kahler, Uwe. "Darstellung, Charakterisierung und Oberflächenmodifizierung von Siliziumnanopartikeln in SiO2." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962346810.
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Hezel, Dominik. "Die Bildung SiO2-reicher Phasen im frühen Sonnensystem." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969513054.
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Karalas, Charilaos-Kimonas. "Process optimization for the 4H-SiC/SiO2 interface." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-174842.
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This thesis aims to optimize the process for the 4H-SiC/SiO2 interface formations. The experiments are made on metal-oxide-semiconductor (MOS) structures, where the semiconductor is an n-type epitaxially grown 4H-SiC thin film. The oxide is fabricated either with thermal oxidation, or by using plasma-enhanced chemical vapour deposition (PeCVD), utilising two different tools, Precision 5000 Mark II (P5000) and Plasmalab 80Plus system (Pekka). The deposition temperature is varied for the thermally grown oxide, while power, pressure and gas ratio of N2O/SiH4 is investigated for the PeCVD method. Also the post deposition annealing (PDA) temperature is studied for both techniques. The oxide formation and PDA is done in N2O ambient in order to study the effect of nitrogen passivation of the traps that exist at the interface of 4H-SiC/SiO2. After the dielectric formation the structures are electrically and structurally characterized. The electrical characterization is done by capacitance-voltage (CV) and current-voltage (IV) measurements while the structural characterization is done with atomic force microscopy (AFM). The density of interface traps (Dits) is extracted using the Terman method from CV data. It is observed that the flatband voltage drops almost to zero when the samples are annealed in nitrogen rich ambient, resulting in a more electrically uniform oxide. Also, Dits can also be reduced by nitrogen treatment when the oxide is deposited by the PeCVD technique. However, it appears that the Terman method cannot determine the amount of traps along the entire bandgap and it is clear that a large amount of Dits are still present closer to the conduction band. Finally, it is found that there is a larger spread in the data extracted from the samples deposited by P5000 in comparison to Pekka, indicating that Pekka is a more reliable tool for oxide deposition in SiC substrate.
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Lian, Cheng-Wei, and 連承偉. "A Buried Silicon Nanocrystal Based High Gain Coefficient SiO2/SiOX/SiO2 Strip-Loaded Waveguide Amplifier on the Si Substrate." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/39948804785714057250.
Full textAbstract:
碩士國立臺灣大學
光電工程學研究所
96
In this thesis, we simulate the SiO2/SiOX/SiO2/Quartz-substrate strip-loaded waveguide and the SiO2/SiOX/SiO2/Si-substrate strip-loaded waveguide. The Effective-Index Method (EIM), the Beam Propagation Method (BPM), and the Finite Element Method (FEM) are used to simulate the waveguide structure. Subsequently, we fabricate these two type waveguides and measure the optical gain and loss coefficients by fitting the one dimensional amplifier equation of the Variable Stripe Length (VSL) method. We observe that the Si-rich SiOX strip-loaded waveguide with silicon (Si) nanocrystal contributed amplified spontaneous emission (ASE) at 750-850 nm with the associated spectral linewidth of 140 nm is characterized. The ASE spectrum is red-shifted 6 nm to PL spectrum because of mode guiding. The peak wavelength of ASE spectrum is blue shift with longer pumping length. Because of the longer pumping length, the mode guiding is stronger and the peak wavelength becomes stable. The optical gain and loss coefficients of the SiO2/SiOX/SiO2/Quartz-substrate strip-loaded waveguide are 70 and 5 cm-1, respectively. The optical gain and loss coefficients of the SiO2/SiOX/SiO2/Si-substrate strip-loaded waveguide are 106.7 and 21 cm-1, respectively. The optical loss coefficient of the Si-substrate device is larger than the Quartz-substrate device which is due to the optical mode leakage to Si substrate. The optical net modal gain coefficient of Si-substrate device is larger than Quartz-substrate device which is due to the better mode confinement. The small-signal amplification of up to 11.73 dB for 795 nm small laser signal under He-Cd laser pumping of 43.7 mW at the wavelength of 325 nm is obtained from the SiO2/SiOX/SiO2/Si-substrate strip-loaded waveguide amplifier with a length of 1 cm.
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Lian, Cheng-Wei. "A Buried Silicon Nanocrystal Based High Gain Coefficient SiO2/SiOX/SiO2 Strip-Loaded Waveguide Amplifier on the Si Substrate." 2008. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-3007200823324700.
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Wang, Chih-Hao, and 王致皓. "porous SiO2." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/18372150403206315560.
Full textAbstract:
碩士國立清華大學
電子工程研究所
87
The porous SiO2 films were fabricated by sol-gel method. The various ratio of C2H5OH, H2O, HCl, NH4OH to TEOS were prepared. Spin-coating, aging, drying and thermal treatment were applied. After the porous SiO2 films were formed, ellipsometer, Rutherford backscattering spectrometer ( RBS ), BOE etchant, C-V measurement, Auger electron spectrometer ( AES ), I-V measurement, Fourier transform infrared spectrometer ( FTIR ), transmission electron microscope ( TEM ), and scanning electron microscope ( SEM ) were employed to study the refractive index, density, porosity, etching rate, dielectric constant, thermal stability, breakdown electric filed, chemical bond, pore size, and planarization of porous SiO2 films. From above measurements, we found that the refractive index, density and dielectric constant rise with the ratio of H2O/TEOS. The porosity behaviors opposite. The etching rate with BOE etchant would increase with the ratio of C2H5OH /TEOS. In the aspect of chemical bond, -OH bond and bond including C would increase with the increasing of H2O and C2H5OH respectively. The electric breakdown field has tendency to rise with the increasing of porosity. For thermal stability study, TiN with thickness ~600A can succeed in obstructing the diffusion of Cu into the porous SiO2 at 400℃ sintering process. In this thesis, the porosity of porous SiO2 as high as 45% can be obtained. The pore size was approximately about 20nm or less. The dielectric constant of the film can be reduced to 2.6. The planarization of spin-coating process was also under control.
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Hou, Chao-ming, and 侯朝明. "A Study on Photoluminescence Mechanism of SiO2/Ru/SiO2." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/63556511574401802964.
Full textAbstract:
碩士義守大學
材料科學與工程學系碩士班
97
Experiments of this study was divided into two parts, first, to sol-gel preparation of colloidal solution Ru/SiO2, using of spin coating made of film, access to H2 or N2 to do heat treatment under hight temperature ; Second, the market SiO2 (10 nm, 30 nm, 250 nm, 1.5μm) acid washing the surface with OH-, the use of chemical reduction method to reduction Ru particles on the surface of silica, using of Sol-Gel coating layer of SiO2. Study of these two parts experiments photoluminescence mechanism of Ru/SiO2. Ru/SiO2 thin films by different concentrations RuCl3 and gases atmosphere under hight temperature, discussing influence of the PL spectra; SiO2/Ru/SiO2 nanoparticles, using different sizes silica and different concentrations RuCl3 for the PL spectrum influenceon. Experimental analysis use of PL wavelength of fluorescent radiation, XRD structure identification, SEM analysis of surface patterns, TEM observation of microstructure. The experimental results show that thin-film heat treatment in H2 access, with the increase in PL of precursors concentrations. but increased above to 10 mmol of precursors concentrations, the PL intensity is down. H2 gas heat can pass Ru precipitation structure enhanced PL intensity. SiO2/Ru particles coated by a layer of SiO2, the PL intensity increased, and the greater size and strong fluorescence intensity. With the increase of PL intensity RuCl3 concentration increased, but the concentration above 0.05 M of PL intensity is down.
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Cho, Eun Chel. "Optical transitions in SiO2/crystalline Si/SiO2 quantum wells and nanocrystalline silicon (nc-Si)/SiO2 superlattice fabrication /." 2003. http://www.library.unsw.edu.au/~thesis/adt-NUN/public/adt-NUN20040105.171835/index.html.
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"Oxido misto de SiO2/SnO2,SiO2/SnO2/Fosfato : propriedades e aplicações." Tese, Biblioteca Digital da Unicamp, 2005. http://libdigi.unicamp.br/document/?code=vtls000366324.
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Qiu, Yi Xing, and 邱毅興. "CaO-Ga2O3-SiO2與Cu-SiO2玻璃之研究." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/99830115767992222238.
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chia, Feng Chen, and 馮振嘉. "Synthesis Characterization and properties of Epoxy/SiO2 and Polyimide/SiO2 nanocomposites." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/75578600510569203918.
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碩士國立中興大學
化學工程學系
93
A novel phosphorus-containing tri-ethoxysilane (dopo-icteos) was synthesized from the addition reaction of 9,10-dihydro-9-oxa -10-phosphaphenanthrene 10-oxide (dopo) and 3-(trieoxysilyl) isocyanate (icteos ). The structure was confirmed by IR spectrum，1H、13C、and 31P-NMR。Epoxy/SiO2 and PI/SiO2 nanocomposites were obtained from the in-situ curing of diglycidyl ether of bisphenol A /4,4-diaminodiphenylmethane /dopoicteos and poly amic acid /dopo-icteos，respectively。The resulted epoxy/SiO2 nanocomposites revealed exhibit higher glass transition temperatures (161~169℃) and char yield (21%~26%)。The phase separation of epoxy/SiO2 observed by SEM is not so obvious compared with the of Polyimide/SiO2 nanocomposites due to the dehydration reaction between hydroxyl group (－C-OH) of epoxy resin and the silanol group (－Si-OH) of silicon network。 From AFM images，the particle size of SiO2 is 20 nm in diameter , implying nanocomposites were achieved。The moisture absorption was lowered (1.2%~0.7%)，and dielectrical constant was also lowered (3.29~3.17)。For PI/SiO2 system，from AFM images，the particle size of SiO2 is 20 nm in diameter，observed by AFM。
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Yang, Tsung-Ying. "Synthesis and Characterization of SiO2, SiO2/Ta2O5 Core-Shell, and Ta2O5 Nanowires." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709302044.
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Yang, Tsung-Ying, and 楊宗穎. "Synthesis and Characterization of SiO2, SiO2/Ta2O5 Core-Shell, and Ta2O5 Nanowires." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/93012430999311526374.
Full textAbstract:
碩士國立清華大學
材料科學工程學系
94
In the first part of experiment, amorphous SiO2 nanowires could be synthesized via carbothermal reduction at 1100 ℃ with Ar flow gas and Fe2O3/C mixed powders, and the ratio of source powders and the flux of Ar flow gas would significant influence the diameter, twisty shape, and density of SiO2 nanowires. Several ratio of Fe2O3/C mixed powders and different Ar flow rate were considered in this study, and it is observed that ultra-high density SiO2 nanowires with high aspect ratio are formed with a suitable ratio of source powders and Ar flux. The growth of SiO2 nanowires is originated by the reaction between SiO and O2 vapor and following the VS growth mechanism, while SiO vapor is formed by CO2 reacting with Si substrate as well as O2 vapor comes from the source powders. Furthermore, lots of neutral oxygen vacancy causes the SiO2 nanowires revealing the strong emitting peak of 450 nm in the cathodoluminescence analysis. In the second part of experiment, poly-crystal Ta2O5 nanowires can be synthesized via annealing SiO2 nanowires at 950℃ in a reductive Ta vapor ambient for 32 hours. To realize the formation process of Ta2O5 nanowires, the influence of different annealing was considered in this study. The Ta2O5 phase is formed by Ta reducing SiO2, and the formation of Ta2O5 nanowires starts with nucleation and grain growth of Ta2O5 crystal forming SiO2/Ta2O5 core-shell structure, and then continuous growth of shell layer. The growth process is dominated by diffusion through the ash layer control, and the diffusion of Ta atoms through shell layer would be the rate-controlling step of the diffusion controlled growth mechanism. In addition, Ta2O5 nanotubes could be synthesized by etching SiO2/Ta2O5 core-shell nanowires with dilute HF solution. It is also observed that the crystalline of Ta2O5 nanowires by vacuum annealing process rather than RTA process. Furthermore, the field-emission character and the cathodoluminescence (CL) property, resulting form the neutral oxygen vacancy, are considered in this study.
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Chang, Chin-Fa, and 張進發. "Investigation of SiO2, TiO2 and TiO2-SiO2 films for anti-reflection properties." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/43173931338520088577.
Full textAbstract:
碩士明道大學
材料科學與工程學系碩士班
99
Investigation of anti-reflection coating using sol-gel method and dip coating technique were deposited on glass. We selected a sol-gel of TiO2(T)、SiO2 (S) and TiO2-SiO2(TS) mixture solution which different ratios of TiO2 and SiO2 solution were mixed. We main Research (1) changes withdrawal speed of different sol-gel solution thin film thickness. (2) influence of thin film thickness and adhesion on glass of changes baking temperature. (3) get the higher transmittance at vision region using different optical thickness stacking. Experimental results found that increase of withdrawal speed cause the film thickness increase but the film was non-uniform, increase of baking temperature cause the thin film thickness down and adhesion raise. SiO2 anti-reflection coating on glass substrate which the optical property the average transmission, was 96.3 % in wavelength range 400-800 nm and 93.8 % in wavelength range 400-1200 nm, and the highest transmittance at 558 nm with 98.3%. SiO2/TiO2-SiO2 double layer anti-reflection coating on glass substrate which the optical property the average transmission, was 96.8 % in wavelength range 400-800 nm and 94.4 % in wavelength range 400-1200 nm, and the highest transmittance at 544 nm with 97.9 %. These results show anti-reflection coating on glass assured increase transmission. Therefore expected to use sol-gel method on solar cell of anti-reflection coating on package glass and increase solar cell Efficiency.
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Lee, Cheng-Tse, and 李承澤. "First-principles Analyses of Unusual Ferromagnetism Observed in CoSi (Core)/SiO2 (Shell),CrSi2 (Core)/SiO2 and FeSi (Core)/SiO2 (Shell) Nanocables." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/29762703539216291910.
Full textAbstract:
碩士國立清華大學
材料科學工程學系
99
First-principles density functional theory-based with spin-polarized calculations were used to investigate CoSi/SiO2 ,CrSi2/SiO2 and FeSi/SiO2 nanowires. The CoSi,CrSi2 and FeSi in bulk are diamagnetic and paramagnetic , but the ferromagnetism in CoSi/SiO2 ,CrSi2/SiO2 and FeSi/SiO2 nanowires was observed. Due to the distorted /dangling bonds in surface , the electron spin up and spin down in d-orbital from transitional metal atoms become asymmetric. Nanowires grows direction and side direction is determined by high resolution TEM and set side direction linking with amorphous SiO2 to bulid a close nanowire surface structure to simulate by first-principle. The cubic CoSi B20 type (P213) nanowires grow along [211] direction. Magnetization is not only from Co atom in surface , but also caused by internal defect. Set the defect in CoSi to simulate and assign total internal magnetization to the surface Co atom, simulation value is pretty consistent with experimental result. The hexagonal CrSi2 C40 type (P6222) nanowires grows along [0001] direction. The ferromagnetism is caused by distorted/dangling bonds in surface. The simulations are very consistent with measurements by further considering the effects of interfacial roughness and distribution of oxygen around the interface. The cubic FeSi B20 type (P213) nanowires grow along [111] direction. The ferromagnetism is also caused by distorted/dangling bonds in surface. The distance from surface to up and down plane Fe atom is different largely, so the magnetization is different largely, too. To understand the ferromagnetism source in transitional metal silicides can investigate the application in ferromagnetic semiconductor.
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Yang, Li-Lan, and 楊歷嵐. "Fabrication and Characterization of SiO2-TiO2 and SiO2-TiO2-Er optical thin films." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/77491076312215264975.
Full textAbstract:
碩士國立成功大學
材料科學及工程學系碩博士班
93
SiO2/Si-based integrated optic devices and circuits have a great benefit to the high-speed telecommunication according to the small thermal expansion mismatches of SiO2 on Si substrate, excellent compatibility with microelectronics, and the high transparency in the major communication windows of optical fiber transmission (1.3 and 1.55 μm wavelength). The derivative optical component such as Erbium-doped fiber amplifier is based on the foundation of these properties. Thin films of SiO2-TiO2 composite oxides with various SiO2:TiO2 compositions were prepared by sol-gel method, using tetraethylortho- silicate (TEOS) and titanium tetraisopropoxide (TTIP) as precursors. The composition, crystal structure and chemical bonding configuration of the as-deposited and annealed SiO2-TiO2 thin films were analyzed by using Rutherford backscattering spectrometry (RBS), glancing incident angle X-ray diffraction (GIAXRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Optical properties of the films were characterized by spectroscopic ellipsometry and ultraviolet-visible spectrophotometry. The Si/Ti ratios in the SiO2-TiO2 films agree with the TEOS/TTIP molar ratio in the sol-gel precursor. When the TEOS/(TEOS+ TTIP) ratio is greater than 40%, the SiO2-TiO2 thin films remain amorphous after annealing at temperature as high as 700oC. FTIR spectra indicate that the quantity of Si-O-Ti bonding can be maximized when the TEOS:TTIP in the precursor is 80%:20%. The refractive index of the SiO2-TiO2 films increases approximately linearly to the mixing ratio of TTIP/(TEOS+TTIP). However, SiO2-rich films possess higher ultraviolet-visible transmittance than the TiO2-rich films. Er-doped SiO2-TiO2-Er thin films were also prepared by sol-gel method, using TEOS and TTIP as precursors with addition of Erbium nitrate pentahydrate powder. According to the investigation on the SiO2-TiO2 thin films, the 80SiO2-20TiO2 film is selected to dope Erbium. Optical properties of the films were characterized by micro-photoluminescence (Micro-PL). Atomic coordination structure of Erbium was defined by Extended X-ray absorption fine structure spectrometry (EXAFS). XPS and FTIR analyses reveal that the main bonding structures of SiO2-TiO2 thin films are not sensitive to the Er doping. All the atoms adjacent to Erbium are oxygen in various doping concentrations. However, the first-neighbor-shell coordination number of Erbium has influence to the optical properties. The annealed 80%SiO2-20%TiO2-1.0%Er with extremely high PL intensity has lowest coordination number as well. Modification of microstructure in the SiO2-TiO2-Er films and its influence on the optical properties are discussed.
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Kundu, Tias. "Study of Si/SiO2 interface passivation and SiO2 reliability on deuterium implanted silicon." Thesis, 2005. http://library1.njit.edu/etd/fromwebvoyage.cfm?id=njit-etd2005-129.
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Chan, Pei-min, and 詹佩旻. "The Thermal Property of SiO2/Fe3O4/SiO2 Magnetic Composite Nanoparticles under Magnetic Field." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/52114076292218571139.
Full textAbstract:
碩士逢甲大學
纖維與複合材料學系
100
In this study, we prepared silica nanoparticles by Stober method and combined with Fe3O4 particles prepare by co-precipitation method to form a novel three-layer structure of composite particles of SiO2/ Fe3O4 / SiO2 magnetic nanocomposite particles. Synthesis method is divided into three parts: (1) by a coupling agent APTES bind to the surface of silicon particles with functional groups to the formation of ammonia modified silica nanoparticles；(2)add surfactants to supply protective effect with Fe3O4 particles, then synthesize with ammonia modified silica nanoparticles to the formation of SiO2/ Fe3O4 core-shell nanoparticles；(3) at the outer of SiO2/ Fe3O4 core-shell nanoparticles generated silica layer to the formation of magnetic nanocomposite particles use sol-gel method by hydrolysis and condensation reaction. The results indicate that, the SiO2/ Fe3O4 core-shell nanoparticles made from Fe3O4 nanoparticles combine to ammonia modified silica nanoparticles showed a complete coating structure, could improve the thermal stability effectively and controlled the particle size easily；the SiO2/ Fe3O4 / SiO2 magnetic nanoparticles successfully made from coating silica layer, and the role of magnetic can improve temperature cause heat-sensitive tumor cell decease about 41~42 ℃ under magnetic field. Finally, we used SiO2/ Fe3O4 / SiO2 magnetic nanocomposite particles that possess thermolysis slowly feature, that can shorten the course of treatment and mitigation of discomfort on biomedical system.Successful in vivo experiments was discussed for the future.
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Wang, Yu-Zhou, and 王宇宙. "Optical Simulation, Optimized Design and Fabrication for SiO2/Ti/SiO2 Solar Selective Absorber Layers." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/79399296102833156265.
Full textAbstract:
碩士國立高雄第一科技大學
光電工程研究所
97
In this study, using simulation and assistance design solar selective absober formula programming by MATLAB to determine film structure is SiO2/Ti/SiO2 (multilayer absorber) to deposit on the Si substrate. According to this initial condition, carries on various films parameter simulation. It may obtain the optimization of film thickness condition (df1=83nm, df2=9.5nm, df3=102nm).And using the multi-target magnetic enhanced sputter system to fabricate solar selective absorber. We use formula of fitting thickness to confirm thickness of the samples we made. By way of UV/VIS spectroscope measure reflection spectrum, and compute thickness and absorptance（α）of samples. Best absorptance of solar selective absorber in this study may achieve 0.942.
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Pozo, López Gabriela del Valle. "Procesos de magnetización en nanocompuestos granulares de ferrita de NiZn/SiO2 y Fe/SiO2 /." Doctoral thesis, 2011. http://hdl.handle.net/11086/115.
Full textAbstract:
Tesis (Doctor en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2008.En el presente trabajo, se estudió el comportamiento magnético de diferentes sistemas granulares nanoestructurados y los mecanismos de reversión de la magnetización operantes, relacionándolos con la naturaleza, tamaño medio de grano, relativa abundancia de las fases presentes e interacción entre ellas. Dos conjuntos de sistemas magnéticos granulares fueron sintetizados: uno, formado por partículas nanocristalinas de Ni0,5 Zn0,5 Fe2O4 inmersas en una matriz de SiO2, fabricado mediante la técnica de molienda de alta energía y técnicas de química húmeda, como sol-gel e impregnación, y el otro conjunto, consistente de partículas nanocristalinas de óxidos de hierro inmersas, también, en una matriz de SiO2, pero sintetizado por aleado mecánico.
The aim of this work is to study the magnetic behavior of granular nanostructured systems and the involved magnetization reversal mechanisms, relating them with the resulting microstructure. For this purpose, two groups of granular magnetic systems were synthesized. One of them is formed by Ni0,5 Zn0,5 Fe2O4 nanocrystalline particles immersed in a SiO2 matrix synthesized by mechanical alloying and chemical methods, such as sol-gel and wet impregnation techniques. The other group of samples, consisting of nanocrystalline particles of iron oxides also dispersed in a SiO2 matrix, was synthesized by mechanical alloying. From the structural and magnetic characterization, it is found that NiZnFe2O4/SiO2 systems are formed by monodomain particles of NiZn ferrite, having a broad particle-size distribution and a high degree of agglomeration. Such agglomerates of ferrite, strongly coupled by the exchange interaction, are surrounded by the silica phase. The magnetization reversal mechanism operating in these particles is the coherent rotation in all the composites studied, with the exception of those synthesized by the wet impregnation method. In this later case, two reversal modes are acting simultaneously: coherent rotation, for smaller particles, and nucleation and propagation of inverse domains, for those of bigger sizes. For the granular system composed of iron oxides and silica, synthesized by mechanical alloying, the structural and magnetic evolution of the composites during the mechanical milling is studied. The milling process promotes the formation of different iron oxides, resulting in nanocomposites with magnetic properties strongly dependent on the phases formed and their microstructure.
Gabriela del Valle Pozo López ; directora Silvia Patricia Silvetti.
Fil: Pozo López, Gabriela del Valle.Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.