Dissertations / Theses on the topic 'Bi2WO6'
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Zhang, Ziyang. "Facile Synthesis of ZnWO4/Bi2WO6, FeWO4/Bi2WO6, and TiO2/Bi2WO6 Nanocomposites via a Modified Pechini Sol-gel Method and their Photocatalytic Performance for Bisphenol A Degradation." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613753216804191.
Full textQin, Hanna. "Preparation, Characterization and Testing for Photocatalytic Activities of Bi2WO6-based Materials." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23583.
Full textHu, Xiaoyue. "Synthesis and Characterization of Graphene Oxide-modified Bi2WO6 and Its Use as Photocatalyst." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31459.
Full textQiao, Yu. "Preparation, Characterization, and Evaluation of Photocatalytic Properties of a Novel NaNbO3/Bi2WO6 Heterostructure Photocatalyst for Water Treatment." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38080.
Full textSilva, Renata Martins da. "SÍNTESE DE MATERIAL PARTICULADO AMARELO A BASE DE TiO2 CONTENDO MoO3 E Bi2O3." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2013. http://tede2.uepg.br/jspui/handle/prefix/1431.
Full textCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Was synthesized particulate material based on containing a small amount of bismuth compounds and molybdenum with satisfactory reproducibility. The material was produced starting from a composition of 99% (mol %) of rutile TiO2 and 1% of MoO3, which were previously mixed and calcined at 1200ºC. The composition studied consisted of 99.8% of the above mixture and 0.2% of bismuth subnitrate hexahydrate, Bi5O(OH)9 NO3)4.6H2O. This powder mixture [(99.8% of TiO2+MoO3 and 0.2% of Bi5O(OH)9 (NO3)4.6H2O)] was homogenized and calcined in tubular furnace at 1200ºC using four different heating rates: 1, 30, 40 e 60 °C/min. The ascalcined powder was characterized by X-ray diffraction (XRD) for identification of the phases resulting, scanning electron microscopy (SEM) to evaluate the microstructure and degree of gglomeration of powders and particle size was estimated by laser scattering technique. The color properties were expressed as CIEL*a*b* coordinates. X-ray patterns indicated the presence of TiO2, Bi2O3, γ-Bi2MoO6, Bi2Ti2O7, Bi2Ti4O11 depending on the heating rate. The yellow color was attributed to the presence of α-Bi2O3, Bi2MoO6 e Bi2Ti2O7. The different heating rates showed no relevant influence on the powder morphology, but the particle size of the powder was suitable for using the material as an inorganic pigment.
Foi sintetizado um material particulado a base de TiO2, contendo uma pequena quantidade de compostos de bismuto e de molibdênio apresentando boa reprodutibilidade. O material foi produzido a partir de uma composição de 99% (mol%) de rutilo TiO2 e 1% de MoO3, previamente misturados e calcinado a 1200 °C. A composição estudada consistia de 99,8% da mistura acima e 0,2% de subnitrato de bismuto hexahidratado, Bi5O(OH)9 (NO3)4.6H2O. Esta mistura em pó [(99,8% de TiO2 + MoO3 e 0,2% de Bi5O(OH)9 (NO3) 4.6H2O)], foi homogeneizada e calcinada em forno tubular a 1200 ºC, utilizando-se quatro taxas de aquecimento diferentes: 1, 30, 40 e 60 °C /min. O pó calcinado foi caracterizado por difração de raios X (DRX) para identificação das fases resultantes, por microscopia eletrônica de varredura (MEV) para avaliação da microestrutura e grau de aglomeração dos pós, o tamanho de partículas foi estimado por espectroscopia de fotocorrelação (PCS) e as propriedades colorimétricas através das coordenadas CIEL*a*b* . O DRX indicou a presença das fases TiO2, α-Bi2O3, γ-Bi2MoO6, Bi2Ti2O7, Bi2Ti4O11 sendo estas dependentes das taxas de aquecimento utilizadas. A cor amarela foi atribuída à presença de α-Bi2O3, -Bi2MoO6 e Bi2Ti2O7. As taxas de aquecimento diferentes não apresentaram nenhuma influência relevante sobre a morfologia do pó, porém o tamanho de partícula do pó mostrou-se adequado para a utilização do material, como um pigmento inorgânico.
Laurent, Kévin. "Etude expérimentale de la microstructure et des propriétés électriques et optiques de couches minces et de nanofils d'oxydes métalliques (d-Bi2O3 et ZnO) synthétisés par voie électrochimique." Phd thesis, Université Paris-Est, 2008. http://tel.archives-ouvertes.fr/tel-00470542.
Full textMATOS, Lucyene Nascimento. "Estudo de fases cristalinas no sistema Bi2O3-Tb4O7." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/821.
Full textA systematic study concerning the crystalline phases in the Bi2O3-rich region of the system Bi2O3-Tb4O7 was made. X-ray powder diffraction method, differential thermal analysis (DTA) and differential scanning calorimetry (DSC) were used in the study of the obtained crystalline phases. Sixteen samples with composition in the range of 4.21 to 33.33 mol% of Tb4O7 were synthesized at 800oC by solid state reaction synthesis. Three distinct crystalline phases were initially identified: a tetragonal phase in the composition range of 4.21 to 5.69 mol% of Tb4O7, a cubic phase for compositions between 6.12 and 29.03 mol% of Tb4O7, and a monoclinic one with 33.33 mol% of Tb4O7. The thermal stability of these compositions was rigorously investigated and the results shown that they are metastable phases in almost all studied range. Under thermal annealing at 500oC, tetragonal phase undergoes decomposition into two phases, monoclinic and rhombohedral ones. The cubic phase, under the same thermal annealing, decomposes partially into a rhombohedral one, except for the interval between 25.0 and 29.1 mol% of Tb4O7. In this case, there was not decomposition under thermal annealing at 500oC during 373 hours, suggesting the cubic phase is stable in this composition range. The monoclinic phase was also tested concerning its thermal stability, but no phase transition was verified. The existence of a possible composition range in the system Bi2O3-Tb4O7 with stable cubic -Bi2O3 type structure is a new and promise result, because of the high ionic conductivity presented by this phase
Um estudo sistemático das fases cristalinas na região mais rica em óxido de bismuto no sistema Bi2O3-Tb4O7 foi realizado. As técnicas de Difração de Raios X pelo método do pó, Análise Térmica Diferencial (DTA) e Calorimetria Diferencial de Varredura (DSC) foram utilizadas no estudo das fases cristalinas obtidas. Dezesseis amostras com composição entre 4,21 e 33,33 mol% de Tb4O7 foram preparadas através de síntese por reação no estado sólido a 800oC. Três fases cristalinas distintas foram inicialmente identificadas: uma tetragonal, presente nas composições entre 4,21 e 5,69 mol% de Tb4O7, uma cúbica, para as composições entre 6,12 e 29,03 mol% de Tb4O7 e uma monoclínica com composição de 33,33 mol% de Tb4O7. Essas composições foram rigorosamente testadas quanto à sua estabilidade térmicas e os resultados indicaram que elas são metaestáveis em quase todo o intervalo investigado. Sob tratamento térmico a 500oC, a fase tetragonal se decompôs em duas fases, uma romboédrica e outra monoclínica. A fase cúbica, sob o mesmo tratamento térmico, se decompôs parcialmente em uma fase romboédrica, exceto para o intervalo compreendido entre 25,0 e 29,1 mol% de Tb4O7. Neste caso não houve decomposição sob tratamento térmico a 500oC durante 373 horas, indicando que a fase cúbica é estável neste intervalo de composição. A fase monoclínica também foi testada quanto à sua estabilidade, não tendo sido verificada nenhuma transição estrutural. A existência de uma possível faixa de composição no sistema Bi2O3-Tb4O7 com estrutura cúbica do tipo -Bi2O3 estável é um resultado inédito e promissor devido ela apresentar elevada condutividade iônica
Silva, Fernanda Garcia e. [UNESP]. "Estudo do efeito de CdO e Bi2O3 no processo de nucleação e crescimento de cristais em matrizes vítreas [TeO2WO3] (CdO;Bi2O3)." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/91980.
Full textConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Apresentamos os resultados de estudos de cristalização de possíveis crescimentos de cristais semicondutores de óxido de telúrio (CdTe) e óxido de bismuto (Bi2O3) no sistema de vidro 20WO3-80TeO2 (TW). Estes trabalho configura-se como um estagio anterior aos estudos de crescimentos de semicondutores em dimensões nanométricas(nanocristais “NCs”) em vidros teluritos. Com este objetivo foi sintetizada a amostra: dopadas com óxido de cadmio e óxido de bismuto, em diversas proporções em suas composições, e estas foram submetidas ou não a ambientes redutores. As amostras foram tratadas termicamente a diferentes temperaturas na região de transição vítrea (Tg ~ 350° C) e analisados utilizando as técnicas de DRX, DSC, FTIR e UV-Vis. Resultados de DRX mostram que acima do recozimento 400°C estimulou o crescimento de trigonal bipiramidal-estruturas conhecidas como α-TeO2 em ambas as amostras, e para as amostras TW dopadas com óxido de bismuto, o tratamento térmico induz a formação de cristais semicondutores de óxido de bismuto. Espectroscopia no infravermelho também mostrou a presença de estruturas Bi2O3. Absorção óptica UV-Vis indica que a presença de cádmio e bismuto em vidro TW sem serem submetidos a tratamento térmico não muda os valores de gap óptico, sendo que este corresponde a uma energia de ~2,8 eV
The present work shows the studies of possible crystallization growth of crystals oxide semiconductors of tellurium (CdTe) and bismuth oxide (Bi2O3) in the glass system 20WO3- 80TeO2 (TW). This work consists in the first steps of initial growth of semiconductors in nanometrics dimensions (nanocrystals “NCs”) in glasses teluritos. The sample was synthecized: doped with oxide of cadmium and bismuth oxide, in diverse ratios of its compositions, and these had been submitted or not it reducing enviroments. The samples had been thermally dealt with the different temperatures in the region glass transition (Tg ~ 350° C) and analyzed using the techniques of DRX, DSC, FTIR and UV-Vis. Results of DRX showed that up to the annealing 400°C it stimulated the trigonal growth known bipiramidal-structures as α-TeO2 in both the samples, and for samples TW (B), the thermal treatment induced the crystal formation bismuth oxide semiconductors. Spectroscopy in the infra-red ray also showed the presence of Bi2O3 structures in samples TW (B). Optic absorption UV-Vis indicated that the presence of cadmium and bismuth in glass TW without being submitted not dumb the thermal treatment the values of optic gap, being that this corresponds to an energy of ~2,8 eV
Silva, Fernanda Garcia e. "Estudo do efeito de CdO e Bi2O3 no processo de nucleação e crescimento de cristais em matrizes vítreas [TeO2WO3] (CdO;Bi2O3) /." Ilha Solteira, 2012. http://hdl.handle.net/11449/91980.
Full textBanca: Ezequiel Costa Siqueira
Banca: Américo Sheitiro Tabata
Resumo: Apresentamos os resultados de estudos de cristalização de possíveis crescimentos de cristais semicondutores de óxido de telúrio (CdTe) e óxido de bismuto (Bi2O3) no sistema de vidro 20WO3-80TeO2 (TW). Estes trabalho configura-se como um estagio anterior aos estudos de crescimentos de semicondutores em dimensões nanométricas(nanocristais "NCs") em vidros teluritos. Com este objetivo foi sintetizada a amostra: dopadas com óxido de cadmio e óxido de bismuto, em diversas proporções em suas composições, e estas foram submetidas ou não a ambientes redutores. As amostras foram tratadas termicamente a diferentes temperaturas na região de transição vítrea (Tg ~ 350° C) e analisados utilizando as técnicas de DRX, DSC, FTIR e UV-Vis. Resultados de DRX mostram que acima do recozimento 400°C estimulou o crescimento de trigonal bipiramidal-estruturas conhecidas como α-TeO2 em ambas as amostras, e para as amostras TW dopadas com óxido de bismuto, o tratamento térmico induz a formação de cristais semicondutores de óxido de bismuto. Espectroscopia no infravermelho também mostrou a presença de estruturas Bi2O3. Absorção óptica UV-Vis indica que a presença de cádmio e bismuto em vidro TW sem serem submetidos a tratamento térmico não muda os valores de "gap" óptico, sendo que este corresponde a uma energia de ~2,8 eV
Abstract: The present work shows the studies of possible crystallization growth of crystals oxide semiconductors of tellurium (CdTe) and bismuth oxide (Bi2O3) in the glass system 20WO3- 80TeO2 (TW). This work consists in the first steps of initial growth of semiconductors in nanometrics dimensions (nanocrystals "NCs") in glasses teluritos. The sample was synthecized: doped with oxide of cadmium and bismuth oxide, in diverse ratios of its compositions, and these had been submitted or not it reducing enviroments. The samples had been thermally dealt with the different temperatures in the region glass transition (Tg ~ 350° C) and analyzed using the techniques of DRX, DSC, FTIR and UV-Vis. Results of DRX showed that up to the annealing 400°C it stimulated the trigonal growth known bipiramidal-structures as α-TeO2 in both the samples, and for samples TW (B), the thermal treatment induced the crystal formation bismuth oxide semiconductors. Spectroscopy in the infra-red ray also showed the presence of Bi2O3 structures in samples TW (B). Optic absorption UV-Vis indicated that the presence of cadmium and bismuth in glass TW without being submitted not dumb the thermal treatment the values of optic " gap", being that this corresponds to an energy of ~2,8 eV
Mestre
Kotsantonis, Sotirios. "Oxygen transport in novel electrolyte materials based on Bi2O3." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.529367.
Full textMoore, Katharine. "Preparation and characterisation of mixed CeO2-Nb2O5-Bi2O3 nanoparticles." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252691.
Full textOudich, Fayssal. "Contribution à l’étude thermodynamique du système Pb-Bi-(Hg)-Fe-(Al,Cr)-O : étude des systèmes Bi2O3–PbO–Al2O3 et Bi2O3–PbO–Fe2O3." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0273/document.
Full textThis research work takes part in a global project whose aim is to understand and solve a corrosion problem of a steel called T91 caused by a liquid mixture of lead-bismuth. It presents a great interest for the nuclear community who aims to develop a new generation of reactors called ADS. This study is a contribution to the thermodynamic study of a complex system involving several elements such as Al, Bi, Pb, Fe, Cr and oxygen. More precisely, it was focused on mixtures of the following oxides Bi2O3 + PbO + Al2O3 and Bi2O3 + PbO + Fe2O3. A long experimental work had been accomplished, in which mixtures of different proportions of these oxides were prepared and heated above 600 °C for several days, followed by samples analyses by use of accurate and advanced techniques. It allowed discovering the different products formed within the different experimental conditions. The results have been modeled using a computer tool. All this allowed a better understanding and anticipating the corrosion products formation of the T91 steel by the metallic liquid
Ren, Yuxuan. "Synthesis, Characterization and Testing of Bi2MoO6-Based Semiconductors Applied in Photocatalytic Water Treatment." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/38901.
Full textBourja, Lamia. "Étude du système CeO2-Bi2O3 pour applications catalytiques et conductimétriques." Phd thesis, Toulon, 2011. http://tel.archives-ouvertes.fr/tel-00659119.
Full textWebster, Nathan A. S. "New fluorite-type Bi2O3-based solid electrolytes : characterisation, conductivity and crystallography." University of Western Australia. School of Biomedical and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0092.
Full textBégué, Pascale. "Matériaux originaux en relation avec Bi2MoO6 : nouvelles voies de synthèse, études structurales et propriétés électriques." Toulouse 3, 2001. http://www.theses.fr/2001TOU30017.
Full textFERREIRA, Katiúscia Daiane. "ESTUDO DE FASES E CRESCIMENTO DE MONOCRISTAIS NO SISTEMA Bi2O3 - TiO2 - ZrO2." Universidade Federal de Goiás, 2008. http://repositorio.bc.ufg.br/tede/handle/tde/1044.
Full textI n this work a systematic study on the phase formation and stability in the system Bi2O3-ZrO2 was realized, the solubility of the Zr4+ ion in Bi12TiO20 (BTO) was investigated and Zr-doped BTO crystals (BTO:Zr) were grown and optically characterized. It was verified that a tetragonal phase was formed in the following wide composition interval: (6-x)Bi2O3:(1+x)ZrO2, with x = 0.5, 0.3, 0.2, 0.1, 0, -0.1, -0.2, -0.3, -0.5, -0.65 e -0.7. The phases were synthesized by solid state reaction and the powders were characterized by Xray diffraction and diferential thermal analysis. The formed tetragonal phase, however, was metastable for all investigated compositions and its preparation was dependent on the sample thermal history. The stable phase at room temperature was a monoclinic one. A low solubility of Zr4+ in BTO was verified, but BTO:Zr single crystals were grown by Top Seeded Solution Growth (TSSG) technique. Good quality crystalline samples were prepared and characterized by chemical compositon and by optical activity, photoconductivity and electro-optical measurements. The results shown that Zr-doping produced a decreasing in the crystal photosensitivity, and almost no changes in the optical activity and electro-optical coefficient were generated.
Neste trabalho foi realizado um estudo sistemático das condições de preparação e estabilidade de fases no sistema Bi2O3-ZrO2, a solubilidade do íon Zr4+ no Bi12TiO20 (BTO) foi investigada e cristais de BTO dopados com Zr4+ (BTO:Zr) foram crescidos e caracterizados opticamente. Verificou-se que uma fase tetragonal é formada no amplo intervalo de composições (6- x)Bi2O3:(1+x)ZrO2, com x = 0,5, 0,3, 0,2, 0,1, 0, -0,1, -0.2, -0,3, -0,5, -0,65 e - 0,7. As fases foram sintetizadas por reação no estado sólido e os pós foram caracterizados por difração de raios-X e análise térmica diferencial. A fase tetragonal formada, no entanto, é metaestável em todo o intervalo de composições investigadas, sendo sua obtenção condicionada à história térmica da amostra. A fase estável à temperatura ambiente é monoclínica. Foi constatado que a solubilidade do Zr4+ no BTO é baixa, mas cristais de BTO:Zr foram crescidos através da técnica Top Seeded Solution Growth (TSSG). Amostras cristalinas de boa qualidade óptica e estrutural foram preparadas e caracterizadas quanto à composição química e através de medidas de atividade óptica, fotocondutividade e coeficiente eletro-óptico. Os resultados demonstram que o Zr produz uma diminuição na fotosensibilidade do cristal, provocando pouca alteração nos valores de atividade óptica e coeficiente eletro-óptico
Almeida, Patricia Matos Viana de. "Caracterização estrutural e dielétrica da matriz BaBi4Ti4O15(BBT) com adição de Bi2O3." Universidade Federal de Mato Grosso, 2015. http://ri.ufmt.br/handle/1/709.
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CAPES
As cerâmicas compostas por óxidos ferroelétricos da família dos Aurivillius possuem destacadamente propriedades, como anisotropia natural, propriedades eletro-ópticas e propriedades piezoelétricas que são necessárias para dispositivos da área tecnológica eletrônica de sensores, semicondutores, circuitos integrados, osciladores, capacitores, baterias, transdutores para alta temperatura, etc. O BaBi4Ti4O15 (BBT) pertence a família dos Aurivillius e estes são estruturas que contém perovskitas em seu interior separada por camadas de fluorita. As perovskitas são uma classe de óxidos que contem íons pequenos e com grande carga, que formam um octaedro de oxigênio ligado pelas extremidades formando cadeias continuas de oxigênio-metal-oxigênio e esse arranjo é que favorece a ferroeletricidade. As propriedades estruturais, elétricas e ferroelétricas do BaBi4Ti4O15 são analisadas mediante acréscimo de íons em sua estrutura pura tais como Pb2+, Al3+, Ga3+, In3+, Ta5+ entre outros, afim de melhorar tais propriedades. Este trabalho propõe investigar o BaBi4Ti4O15 com adição de óxido de Bismuto (Bi2O3), averiguando suas propriedades estruturais e dielétricas através de técnicas de difração de Raios-X, espectroscopia raman, espectroscopia de impedância, e ainda buscar aprimoramento da síntese quanto ao tempo para formação de fase e homogeneização das partículas do material. Os resultados de caracterização estrutural através da Difração de Raios-X e do refinamento Rietveld das amostras cerâmicas de BaBi4Ti4O15 com diferentes concentrações molares (1, 2, 5 e 10%) de Bi2O3 nos confirmaram a formação de uma única fase e a presença de todos os componentes de BaBi4Ti4O15, não encontrando impurezas (dentro das limitações técnicas do programa). A caracterização estrutural através da espectroscopia raman nos mostrou picos característicos (274,7 cm-1 e 552,75 cm-1) de uma estrutura com octaedros, caracterizando uma estrutura Perovskita. Na picnometria, a análise da densidade, mostrou que a presença de Bi2O3 dependendo de sua porcentagem pode aumentar ou diminuir a densidade da amostra de BaBi4Ti4O15, sendo que a compactação maior foi na quantidade de 10% de fundente, em torno de 6g/cm3. Já através da espectroscopia de impedância dielétrica os dados obtidos se mostraram coerentes com os resultados encontrados na literatura. Foi encontrada uma transição de fase ferroelétrica entre 420ºC e 450ºC, verificada nos gráficos do mecanismo do módulo dielétrico, da energia de ativação e da Constante dielétrica; também se verificou que o BBT tem um comportamento dielétrico que não segue o modelo de Debye, além disso, foram observadas cargas de transportes de longo e curto alcance em um mecanismo de condução ativado termicamente e ainda foi encontrada uma contribuição de uma condução iônica no material.
The composed ceramics for ferroelectrics oxides of the family of the Aurivillius possess properties prominently, as natural anisotropy, optic properties electro and piezoelétricas properties that are necessary for devices of electronic the technological area of sensors, integrated semiconductors, circuits, oscillators, capacitors, batteries, transducers for high temperature, etc. The BaBi4Ti4O15 (BBT) belongs the family of the Aurivillius and these are structures, which contain perovskitas in its separate interior for flourite layers. The perovskitas are a small oxide classroom that will count ions e with great load, which chains form one octahedro of on oxygen for the extremities forming continue of oxygen-metal-oxygen and this arrangement is that it favors the ferroelectricity. The structural, electric and ferroelectrics properties of the BaBi4Ti4O15 are analyzed by means of addition of ions in its pure such as Pb2+, Al3+, Ga3+, In3+, You5+, among others similar structure to improve such properties. This work considers to investigate the BaBi4Ti4O15 with Bismuth oxide addition (Bi2O3), inquiring its structural and dielectric properties through techniques of diffraction of Ray, spectroscopy Raman, spectroscopy of impedance, and still to search improvement of the synthesis how much to the time for formation of phase and homogenization of particles of the material. The results of structural characterization through the diffraction de Ray and of the Rietveld refinement of the ceramic samples of BaBi4Ti4O15 with different molar concentrations (1, 2, 5 and 10%) of Bi2O3 in had confirmed the formation of an only phase and the presence to them of all the components of BaBi4Ti4O15, not finding impurities (inside of the limitations techniques of the program). The structural characterization through the spectroscopy raman in showed to characteristic peaks (274,7 cm-1 and 552,75 cm-1) of a structure with octahedro, characterizing a perovskite structure to them. In the picnometria, the analysis of the density, showed that the presence of Bi2O3 depending on its percentage can increase or diminish the density of the sample of BaBi4Ti4O15, being that the compacting biggest was in the amount of 10% of fondant, around 6g/cm3. Already through the spectroscopy of dielectric impedance the gotten data if had shown coherent with the results found in literature. A transition of ferroelectric phase between 420ºC and 450ºC was found, verified in the graphs of the mechanism of the dielectric module, the energy of activation and the dielectric Constant; also if it verified that the BBT has a dielectric behavior that does not follow the model of Debye, moreover, had been observed loads of transports of long and short reach in a mechanism of conduction activated thermally and still was found a contribution of an ionic conduction in the material.
Sirota, Ben. "Synthesis and Characterization of ZnO and Bi2O3 Nanowires Grown by Magnetron Sputtering." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/766.
Full textDurand, Olivier. "Propriétés structurales et vibrationnelles des phases désordonnées dans le système TeO2-Bi2O3." Limoges, 2006. http://aurore.unilim.fr/theses/nxfile/default/25dc7b11-f659-4f3e-93fb-e0700525f254/blobholder:0/2006LIMO0045.pdf.
Full textThis work aimed at elucidating crystalline structure of disordered metastable compounds, evidenced in the TeO2 rich part of the TeO2-Bi2O3 system. For this study, we used mostly Raman scattering, total neutron scattering and Reverse Monte-Carlo modelling. The structures of such phases exhibit a cubic average symmetry and are composed of TeO4 and TeO3 polyhedra. The arrangement of those polyhedra leads the cations to form a well defined FCC lattice up to distances of hundreds of nanometers. Nevertheless, the anionic lattice is almost entirely disordered. The analysis of X-ray diffraction line broadening shows that the cationic lattice is less and less defined while increasing the TeO2 content. Beyond some TeO2 threshold, the structures evolve towards an orthorhombic average symmetry and can be described by polymerised chains of TeO3 polyhedra. This evolution is associated with the apparition of non-linear optics activity : Second Harmonic Generation was evidenced for such materials
Helfen, Arnaud. "Elaboration et caractérisation d'un nouvel électrolyte solide pour les piles à combustible : δ-Bi2O3". Phd thesis, Université de Marne la Vallée, 2004. http://tel.archives-ouvertes.fr/tel-00351659.
Full textLeandro, Silvana Castro. "Síntese e caracterização óptica de vidros da família TeO2 -B2O3 -(Bi2O3 ou WO3) /." Ilha Solteira, 2018. http://hdl.handle.net/11449/157392.
Full textResumo: Vidros a base de óxidos de metais pesados (TeO2, WO3, Bi2O3) apresentam alto índice de refração, altos valores de não-linearidade óptica e alta constante dielétrica. Essas propriedades físicas possibilitam diversas aplicações, como, por exemplo, para comutação ultrarrápida em dispositivos ópticos e, exibem, quando dopados com terras raras, importantes propriedades de luminescência [1]. Vidros dos sistemas ternários xTeO2 – yB2O3 – zWO3 e xTeO2 – yB2O3 – kBi2O3 foram preparados pelo método “melt-quenching” com x de 70 a 45%mol, y de 40 a 10%mol, z de 30 a 15%mol e k com variação de 20 a 10%mol. Introduzimos o óxido de Boro para dar maior viscosidade ao material e aumentar a estabilidade térmica. Foram obtidas amostras homogêneas e transparentes para as seguintes composições: 70TeO2–10B2O3–20WO3, 70TeO2–20B2O3–10Bi2O3 e 55TeO2 –30B2O3–15Bi2O3. Dados de espectroscopia de IR revelaram que a rede dos vidros consiste basicamente das seguintes unidades estruturais: [TeO4], [WO4], [WO6], [BO4], [BO3] e Te-O-W para o sistema TeO2 – B2O3 – WO3 e de [TeO4], [BiO3], [BiO6], [BO4], [BO3] para o sistema TeO2 – B2O3 – Bi2O3. Medidas de absorção óptica das amostras foram realizadas antes e após a exposição a irradiação gama em doses de 10Gy, 1kGy, 10kGy e 50kGy e forneceram valores das bordas de absorção no intervalo de 378 a 449 nm. Obtiveram-se índices de refração da ordem de n > 2 em 633 nm através do equipamento Interferômetro de Michelson e método do ângulo de Brewster. As energias do g... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Glasses based on heavy metal oxides (TeO2, WO3, Bi2O3) have high refractive index, high values of optical nonlinearity and high dielectric constant. These physical properties enable a variety of applications, such as for ultrafast switching in optical devices and, when doped with rare earths, exhibit important luminescence [1]. Glasses in the ternary systems xTeO2–yB2O3–zWO3 and xTeO2–yB2O3–kBi2O3 were prepared from melt quenching method with x from 70 to 45 mol%, y from 40 to 10 mol%, z from 30 to 15 mol% and k with variation from 20 to 10 mol%. We introduce the Boron oxide to give a higher viscosity to the material, ie, higher thermal stability. Homogeneous and transparent samples were obtained for the following compositions: 70TeO2–10B2O3–20WO3, 70TeO2–20B2O3–10Bi2O3 and 55TeO2 –30B2O3–15Bi2O3. FTIR spectroscopy data revealed that the glass basically consists of the following structural units: [TeO4], [WO4], [WO6], [BO4], [BO3] and Te-O-W to the system TeO2–B2O3–WO3 and [TeO4], [BiO3], [BiO6], [BO4], [BO3] to the system TeO2–B2O3–Bi2O3. Optical absorption measurements of the samples were performed before and after exposure to gamma irradiation at doses of 10Gy, 1kGy, 10kGy and 50kGy and provided absorption edge values in the range of 378 to 449 nm. Were obtained refractive index of the order of n> 2 at 633 nm through the equipment Michelson´s Interferometer and Brewster's angle method. The optical gap energies obtained from these glasses are of the order of ≈ 2 to 3 eV.
Doutor
Follet-Houttemane, Claudine. "Les phases oxyfluorées du système Bi2O3-PbO-PbF2 : stabilité - propriétés électriques - caractéristiques structurales." Lille 1, 1987. http://www.theses.fr/1987LIL10215.
Full textLabidi, Olfa. "RELATIONS STRUCTURES-PROPRIETES DANS LE SYSTEME Bi2O3-PbO-V2O5 : SURSTRUCTURES, POLYMORPHISME, INCOMMENSURABILITE et CONDUCTIVITE." Phd thesis, Université des Sciences et Technologie de Lille - Lille I, 2006. http://tel.archives-ouvertes.fr/tel-00199221.
Full textL'étude s'est prolongée au sein du binaire BiVO4-nPbO. Une transition de phase α→β a été caractérisée pour le terme n=1, PbBiVO5. Les structures des cristaux «maclés» ont été résolues à l'ambiante et à 530°C. PbBiPO5 subit une transition analogue. PbBiAsO5 cristallise dès l'ambiante dans la forme β.
Pb2BiVO6 (n=2) subit plusieurs transitions structurales α, β et δ. Les structures des formes α et β ont été déterminées sur monocristal ; la résolution de la structure de β a nécessité l'emploi d'un formalisme 4D. Deux nouvelles formes α' et δ' ont été obtenues par substitution du V par Mn ou P. Leurs structures découlent des phases α à l'ambiante, et δ à 680°C. La conductivité électrique des matériaux a été étudiée et des corrélations propriétés de conduction - caractéristiques structurales proposées.
Schmidt, Samara [UNESP]. "Estudo da modificação da fotoluminescência em α-Bi2O3 após tratamento térmico assistido por pressão". Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/136399.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este estudo avaliou o efeito de um tratamento térmico assistido por pressão sobre as propriedades de fotoluminescência do óxido de bismuto (α-Bi2O3) sintetizado pelo método hidrotérmico assistido por micro-ondas (HAM). O α-Bi2O3 teve sua estrutura determinada através da técnica de Difração de raios X, e com o auxílio de refinamentos pelo método de Rietveld foi possível visualizar que a amostra tratada com pressão possui um ângulo entre os clusters [BiO6]-[BiO6] ligeiramente maior. As técnicas de microscopia eletrônica de varredura e transmissão possibilitaram a definição da morfologia acicular, tamanho e direção de crescimento dos cristais. A composição química dos materiais foi avaliada pelas espectroscopias Raman e de Fotoelétrons excitados por raios X, onde os espectros Raman mostraram um aumento da intensidade nos modos acima de 284cm-1 na amostra tratada com pressão, sugerindo uma alteração na densidade eletrônica. Os espectros XPS em ambas amostras não mostraram a presença de contaminantes, fase secundária ou íons Bi2+. Ambas as técnicas mostraram que as emissões PL do α-Bi2O3 na região de baixa energia (inferior a 2,1 eV) são atribuídas a lacunas de oxigênio que formam estados doadores. As propriedades óticas dos materiais foram avaliadas e comparadas com o auxílio da técnica de espectroscopia Uv-vis, onde não foi possível verificar nenhuma alteração significativa nas amostras. As propriedades fotoluminescentes das amostras também foram medidas e comparadas. Foi possível verificar que o tratamento térmico assistido por pressão causou um aumento angular entre os clusters [BiO6] - [BiO6] do α-Bi2O3, resultando num aumento significativo da intensidade da emissão PL na amostra tratada com pressão. Cálculos teóricos foram utilizados para simular as bandas de valência e condução dos materiais assim como a densidade eletrônica média nessas bandas. Através dos cálculos foi possível visualizar como a distorção dos clusters altera a polarização dos estados O 2p, e consequentemente a densidade eletrônica dos cristais.
This research evaluated the effect of a pressure-assisted heat treatment (PAHT) on the photoluminescent (PL) properties of bismuth oxide (α-Bi2O3), which was synthesized by a microwave-assisted hydrothermal (MAH) method. α-Bi2O3 crystal structure was characterized X-ray diffraction, and Rietveld refinements showed the pressure-assisted heat treatment caused an angular increase between the [BiO6]– [BiO6] clusters of α-Bi2O3. Scanning and transmission electron microscopies allowed defining the morphology (acicular), size and crystal growth direction of crystals. Chemical composition of samples was evaluated by Raman and X-ray photoelectron (XPS) spectroscopies. Raman spectra showed an increase in the spectrum intensity for frequencies higher than 284 cm-1 for PAHT samples, which suggests an alteration in the electronic density of crystals. XPS spectra of samples did not show the presence of contaminants, secondary phases and Bi2+ ions. Both Raman and XPS spectra also showed that the α-Bi2O3 PL emissions in the low-energy region (below 2.1 eV) are attributed to oxygen vacancies that form defect donor states. UV–vis absorption spectra showed no significant difference between samples. The angular increase between [BiO6]–[BiO6] clusters of α-Bi2O3 promoted a significant rise in the electronic density of the material, which was considered as the cause for the increase in PL emission intensity in PAHT samples. First-principles total-energy calculations were carried out within the periodic density-functional-theory (DFT) to simulate valence and conduction bands, and the average electronic density in these bands. Theoretical results showed how cluster distortion alters the polarization of O 2p states, and consequently, the electronic density of crystals.
Schmidt, Samara. "Estudo da modificação na fotoluminescência em α-Bi2O3 após tratamento térmico assistido por pressão /". Araraquara, 2016. http://hdl.handle.net/11449/136399.
Full textCo-orientador: Sergio Mazurek Tebcherani
Co-orientador: Diogo Pascoalini Volanti
Banca: Sonia Maria Zanetti
Banca: Marco Aurélio Cebim
Banca: Maximo Siu Li
Resumo: Este estudo avaliou o efeito de um tratamento tér mico assistido por pr essão sobre as propriedades de fotoluminescência do óxido de bismuto ( α - Bi 2 O 3 ) sintetizado pelo método hidrotérmi co assistido por micro - ondas (HAM ) . O α - Bi 2 O 3 teve sua estrutura determinada através da técnica de Difração de raios X, e com o auxílio de refinamentos pelo método de Rietveld foi possível visualizar que a amostra tratada com pressão possui um ângulo entre os cluster s [BiO 6 ] - [BiO 6 ] ligeiramente maior. A s técnicas de microsc opia el etr ônica de varredura e transmissão possibilitaram a definição da morfologia acicular, tamanho e direção de crescimento dos cristais. A composição química dos materiais foi avaliada pelas espectroscopias Raman e de Fotoelétrons excitados por raios X, onde os espectros Raman mostraram um aumento da intensidade nos modos acima de 284cm - 1 na amostra tratada com pressão, sugerindo uma alteração na densidade eletr ônica. Os espectros XPS em ambas amostras não mostraram a presença de contaminantes, fase secundári a ou íons Bi 2+ . Ambas as técnicas mostraram que as emissões PL do α - Bi 2 O 3 na região de baixa energia (inferior a 2,1 eV) são atribuída s a lacunas de oxigênio que formam estados doadores. As propriedades óticas dos materiais foram avaliadas e comparadas co m o auxílio da técnica de espectroscopia Uv - vis, onde não foi possível verificar nenhuma alteraç ão significativa nas amostras. As propriedades fotoluminescentes das amostras também foram medidas e comparadas . F oi possível verificar que o tratamento térmico assistido por pressão ca usou um aumento angular entre os clusters [BiO 6 ] - [BiO 6 ] do α - Bi 2 O 3, resultando num aumento significativo da intensidade da emissão PL na amostra tratada com pressão . Cálculos teóricos foram utilizados para simular as bandas de va lência e condução dos ma...
Abstract: This research evaluated the effect of a pressure - assisted heat treatment (PAHT) on the photoluminescent (PL) properties of bismuth oxide ( α - Bi 2 O 3 ), which was synthesized by a microwave - assisted hydrothermal (MAH) method. α - Bi 2 O 3 crystal structure was characterized X - ray diffraction, and Rietveld refinements showed the pressure - assisted heat treatment caused an angular increase between the [BiO 6 ] - [B iO 6 ] clusters of α - Bi 2 O 3 . Scanning and transmission electron microscopies allowed defining the morphology (acicular), size and crystal growth direction of crystals. Chemical composition of samples was evaluated by Raman and X - ray photoelectron (XPS) spectr oscopies. Raman spectra showed an increase in the spectrum intensity for frequencies higher than 284 cm - 1 for PAHT samples, which suggests an alteration in the electronic density of crystals. XPS spectra of samples did not show the presence of contaminants, secondary phases and Bi 2+ ions. Both Raman and XPS spectra also showed that the α - Bi 2 O 3 PL emissions in the low - energy region (below 2.1 eV) are attributed to oxygen vacancies that form defect donor states. UV - vis absorption spectra showed no significant difference between samples. The angular increase between [BiO 6 ] - [BiO 6 ] clusters of α - Bi 2 O 3 promoted a significant rise in the electronic density of the material, which was considered as the cause for the increase in PL emission intensity in PAHT samples. F irst - principles total - energy calculations were carried out within the periodic density - functional - theory (DFT) to simulate valence and conduction bands, and the average electronic density in these bands. Theoretical results showed how cluster distortion a lters the polarization of O 2p states, and consequently, the electronic density of crystals.
Banca: Carlos Frederico de Oliveira Graeff
Doutor
Helfen, Arnaud. "Élaboration et caractérisation d'un nouvel électrolyte solide pour les piles à combustible : δ-Bi2O3". Marne-la-Vallée, 2004. https://tel.archives-ouvertes.fr/tel-00351659.
Full textWith an aim of finding a new electrolyte for the SOFC functioning at lower temperatures, we were interested in the new electrochemical synthesis of the delta phase of bismuth oxide. δ-Bi2O3 is a well-know high oxide-ion conducting material, but its narrow temperature range of stability, 729-825°C, had limited its application. The electrochemical method suggested by Switzer et al. Enables to stabilize this phase at room temperature. The study of δ-Bi2O3 becomes interesting again for an application such as solid electrolyte in full cell. Firstly, the influence of the electrochemical synthesis parameters of the δ-Bi2O3 thin layers was studied. It was deduced that a temperature of more than 50°C was necessary and that the optimal temperature deposition was 65°C. The bath pH value must be higher than 14. The current density, during the electrodeposition, was about 2. 25 and 3 mA/cm2. Using the XRD and TEM, the polycristalline structure of δ-Bi2O3 was confirmed. Both XRD measurements and TEM observations indicated an existence of a grain size of about 100 nm in these films. HRTEM images revealed nanocrystallites 10-20 nm in size. Their nanocrystalline natures stabilize the δ-Bi2O3 at room temperature. Using the EQCM, we have shown that the thickness of electrodeposited -Bi2O3 could not exceed 2 µm. Our stability study shown that the electrodeposited δ-Bi2O3 films exhibit a high long-time stability and that the δ-Bi2O3 keeps its fcc structure up to an annealing temperature of 340°C, above which it transforms into the sillenite structure. We have shown also that it is possible to make single crystalline nanowires of δ-Bi2O3, but the optimal conditions of electrodeposition synthesis were not determined. Lastly, the first measurements of conductivity were carried out. The preliminary results shown an ionic behaviour of our deposits, but we have some preoccupations for the reproducibility
El, Harrak Amin. "Synthèse, stabilité et propriétés électriques de phases conductrices anioniques du système Bi2O3-CaO-PbO." Lille 1, 1990. http://www.theses.fr/1990LIL10106.
Full textLaabidi, Olfa. "Relations structures-propriétés dans le système Bi2O3-PbO-V2O5 : surstructures, polymorphisme, incommensurabilité et conductivité." Lille 1, 2006. https://pepite-depot.univ-lille.fr/RESTREINT/Th_Num/2006/50376_2006_286.pdf.
Full textGong, Yuxuan. "Dielectric and Structural Study of Bi2O3-BaO-CuO Glass Flux Additives Sintered Barium Titanate for Multilayer Capacitor Applications." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1368086374.
Full textRocha, Marta Jussara Souza da. "Estudo das caracteristicas estruturais e elÃtricas do SrBi2Nb2O9 (SBN) dopado com La2O3, PbO e Bi2O3." Universidade Federal do CearÃ, 2009. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2611.
Full textCerÃmica Aurivillius sÃo conhecidas por sua excelente resistÃncia à fadiga e a sua alta temperatura de Curie, a qual apresenta cÃlula unitÃria ortorrÃmbica. A cerÃmica a ser estudada, SrBi2Nb2O9 (SBN), à matÃria-prima potencial na fabricaÃÃo de memÃrias ferroelÃtricas, com polarizaÃÃo espontÃnea e bons coeficientes piezelÃtricos. Dentro deste grupo cerÃmico, o SrBi2Nb2O9 (SBN) à o material com menor estrutura octaÃdrica distorcida. Apesar disto, o SBN sofre de perda dielÃtrica elevada, devido à evaporaÃÃo de Ãxido de bismuto durante a preparaÃÃo, vindo a limitar sua utilizaÃÃo. A ativaÃÃo mecÃnica usada foi a de moinho planetÃrio, que nos permite calcinar o composto por temperaturas mais baixas que as geralmente apresentadas na literatura. ApÃs a calcinaÃÃo, moemos por mais duas horas, e obtemos um pà de boa densidade e reduzida temperatura de sinterizaÃÃo. Este fato previne a perda de elementos volÃteis (Pb ou Bi) e controla o crescimento do grÃo que à produzido quando a alta temperatura à necessÃria para a obtenÃÃo dessa cerÃmica. No presente trabalho, esta cerÃmica Aurivillius serà estudada em suas propriedades estruturais e dielÃtricas com dopagem de Ãxido de lantÃnio, de bismuto e de chumbo, em diversas porcentagens. Adicionalmente, houve a necessidade de um estudo comparativo com respeito a diferentes tipos de ligantes, e os testes obedeceram Ãs dopagens mencionadas acima. Os resultados foram obtidos pelo mÃtodo Hakki & Coleman, pela Espectroscopia de ImpedÃncia e medidas de RadiofreqÃÃncia, para a caracterizaÃÃo elÃtrica. DifraÃÃo de Raios-X, juntamente com o Refinamento Rietveld, Espectroscopia Raman e de Infravermelho, para anÃlise estrutural, dentre outras medidas e mÃtodos.
Aurivillius ceramic are know by is excellent resistence to high use and itÂs high Curie temperature, in wich it presents unicell ortorrÃmbic. The ceramic to be study SrBi2Nb2O9 (SBN), is a potential prime-mater in the production of ironelectric memories with sponteneous polarization and good piezelectric coeficient. Within this ceramic group, SrBi2Nb2O9 (SBN) is the material with less twisted octaÃdric structure. Even so, SBN, have high loss of dielectric, due to the evaporation of bismut oxide during preparation, inposing a limit to is use. The mechanical activation used was of a planetarium will, that allows us to calcinate the compost by very low temperatures that are presented in literature. After the calcination, we will it for two more hours and have dust that have good density and low sinterization temperature. That fact privine us the lost of volatile elements ( Pb or Bi ) and controls the grow of the seed wich is produced when high Temperature is needed to obtain this ceramic . In the present work, this Aurivillius ceramic wil be studyed in is dielectric and structure properties with dopage of lantÃnium oxide, lead oxide and bismut oxide, on different percentages. In addiction there was necessety of a comparative study, regarding the different types of leagues and tests obay the dopage already menttionated. The results were obtained by the Hakki & Coleman method by the Impendence Espectroscopic and radiofrequense mesures, to the electric caracterization . X-rays Defraction with Rictveld refiament , Raman and infrared espectroscopic, to structural analises , within other mesures and methods .
Arantes, Neto Moisés de Souza [UNESP]. "Estudo da cinética de nucleação e crescimento de cristais na matriz vítrea TeO2-WO3-Bi2O3." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/143915.
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O avanço tecnológico das últimas décadas proporcionou avanços significativos tanto na obtenção quanto nas aplicações dos vidros. Estes materiais possuem aspectos fundamentais, as quais os colocam como alternativas viáveis para aplicações na óptica, em espelhos primários de telescópios e até dispositivos fotônicos de fibras em escala nanométricas. Os vidros à base de óxido de telúrio são uma opção para substituir ou melhorar as características de sistemas vítreos convencionais como os vidros silicatos. As propriedades ópticas e estruturais dos vidros teluritos têm direcionado as pesquisas para diversas aplicações. Neste trabalho amostras de vidros teluritos foram obtidas a partir da matriz 80TeO2•(20 – x)WO3 •(x)Bi2O3(mol %) preparadas pelo método de fusão/resfriamento. Estas amostras foram caracterizadas térmica e estruturalmente como objetivo de estudar o controle e distribuição do tamanho dos cristais na matriz vítrea por meio de duas etapas de tratamento térmico, estudar os processos de nucleação e crescimento de cristais e também estudar a cristalização induzida no vidro. Usando duas etapas de tratamento térmico obteve-se vitrocerâmicas com distribuição uniforme dos tamanhos dos cristais. Com a técnica de análise térmica diferencial (ATD), associada ao método de Matusita, os resultados indicaram que as amostras foram nucleadas durante o recozimento usado para retirar as tensões mecânicas remanescentes do processo de fusão/resfriamento. A cristalização induzida foi estudada usando a difração de Raios–X (DRX). Os resultados possibilitaram observar a formação de duas fases cristalinas após o tratamento térmico na temperatura de 400°C, a fase δ–Te0,95W0,05O2,05e a fase δ–Bi2O3. Com os tratamentos posteriores também foram formadas as fases α–TeO2 e γ–TeO2.O estudo da cristalização induzida também foi acompanhado pela Espectroscopia Raman, que possibilitou a identificação dos modos vibracionais dos polimorfos do TeO2.
The technological advance of the last decades has provided significant advances both in obtaining and in the applications of glass. These materials have fundamental aspects, which put them as viable alternatives for applications in optics, in primary mirrors of telescopes and even photonic devices fibers in nanometric scale. The glasses of tellurium oxide base are an option to replace or enhance the characteristics of conventional vitreous systems such as silicate glasses. Optical and structural properties of tellurite glasses have directed research for various applications. In this work, samples of tellurite glasses were obtained from the matrix 80TeO2•(20 – x)WO3•(x)Bi2O3(mol%) prepared by the method of melting/cooling. These samples were characterized by thermal and structurally in order to study the control and size distribution of crystals in the glass matrix by two-step heat treatment, study the nucleation process and growth of crystals and study induced crystallization in the glass. Using two-step heat treatment was obtainedglass-ceramics with uniform distribution of crystal sizes. With the differential thermal analysis (DTA) associated with Matusita method, the results indicated that the samples were nucleated during annealing used to remove the remaining mechanical stresses of the melting/cooling process. The induced crystallization was studied using X-ray diffraction (XRD). It was possible to observe the formation of two crystalline phases after the heat treatment at 400°C, the δ–Te0,95W0,05O2,05 and δ–Bi2O3 phases.With subsequent treatments were also formed the α–TeO2 and γ–TeO2 phases. The induced crystallization of the study was accompanied by Raman spectroscopy, which allowed the identification of vibrational modes of polymorphs of TeO2.
Arantes, Neto Moisés de Souza. "Estudo da cinética de nucleação e crescimento de cristais na matriz vítrea TeO2 – WO3 – Bi2O3." Ilha Solteira, 2016. http://hdl.handle.net/11449/143915.
Full textResumo: O avanço tecnológico das últimas décadas proporcionou avanços significativos tanto na obtenção quanto nas aplicações dos vidros. Estes materiais possuem aspectos fundamentais, as quais os colocam como alternativas viáveis para aplicações na óptica, em espelhos primários de telescópios e até dispositivos fotônicos de fibras em escala nanométricas. Os vidros à base de óxido de telúrio são uma opção para substituir ou melhorar as características de sistemas vítreos convencionais como os vidros silicatos. As propriedades ópticas e estruturais dos vidros teluritos têm direcionado as pesquisas para diversas aplicações. Neste trabalho amostras de vidros teluritos foram obtidas a partir da matriz 80TeO2•(20 – x)WO3 •(x)Bi2O3(mol %) preparadas pelo método de fusão/resfriamento. Estas amostras foram caracterizadas térmica e estruturalmente como objetivo de estudar o controle e distribuição do tamanho dos cristais na matriz vítrea por meio de duas etapas de tratamento térmico, estudar os processos de nucleação e crescimento de cristais e também estudar a cristalização induzida no vidro. Usando duas etapas de tratamento térmico obteve-se vitrocerâmicas com distribuição uniforme dos tamanhos dos cristais. Com a técnica de análise térmica diferencial (ATD), associada ao método de Matusita, os resultados indicaram que as amostras foram nucleadas durante o recozimento usado para retirar as tensões mecânicas remanescentes do processo de fusão/resfriamento. A cristalização induzida foi estudad... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor
Berkaïne, Nabil. "Propriétés optiques non-linéaires de composés métastables du système TeO2 - Bi2O3 : apports de la chimie quantique." Limoges, 2009. https://aurore.unilim.fr/theses/nxfile/default/0553a07f-6261-48b5-a299-9696b78cdb0b/blobholder:0/2009LIMO4029.pdf.
Full textThis work consisted in the study of non-linear optical properties of orthorhombic metastable phases in the TeO2 rich part of the TeO2 - Bi2O phase diagram. After characterizing the structure of these phases, we focused on the study of their 2nd order non-linear optical properties (NLO) by performing second harmonic generation (SHG) experimental measurements. A surprising variation of the SHG efficiency with TeO2 rate was noted. In order to explain it, the 2nd NLO susceptibility for each TeO2 rate was calculated by applying a theoretical method based on the density functional theory (DFT). Such model was first validated. This method was also applied to α and γ TeO2 crystalline phases and cristobalite SiO2. We evidenced some relationships between the 3rd order NLO properties of tellurites and their structural arrangements (entities connection, tellurium lone pair)
Thompson, Maria. "Synthesis and characterisation of d-Bi2O3 related materials stabilised by substitutions of Ca, Ga, Nb and Re." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1185/.
Full textJacobsoone, Virginie. "Synthèse et caractérisation de phases oxyfluorées de type BIMEVOX et de verres oxyfluorés à base de Bi2O3." Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-15.pdf.
Full textCompte tenu de la formule chimique des échantillons appartenant à ce domaine, un excès de Zn est nécessairement présent, mais aucune trace d’oxyde de zinc n’a pu être détectée sur les clichés de idffraction des rayons X sur poudre. La spectroscopie de diffusion Raman a permis de mettre en évidence une continuité entre les phases cristallisée et vitreuse. En accord avec l’évolution progressive et continue des spectres lorsque l’on passe de la phase cristallisée à la phase vitreuse, l’hypothèse la plus problable conduit à la délocalisation des ions Zn2+ à la périphérie du feuillet pérovskite. Cette hypothèse est en accord avec la forte augmentation du paramètre c. Par recuit, la phase G se transforme progressivement en phase de type C. Les échantillons de la phase G partiellement recristallisée présentent en mesures électriques une augmentation importante des valeurs de Sigma sont 50 fois supérieures à celles des échantillons vitreux correspondants (Sigma=4. 10-4 S. Cm-1 à 260 °C pour Bi0,65Zn1,215V0,135O1,313F2,43). Une étude des systèmes Bi3O3-PbO-PbF2 et Bi2O3-PbO-CdF2 a également été réalisée. Les synthèses ont été effectuées en creusets de quartz et ont permis d’isoler un large domaine vitreux s’étendant vers le binaire Bi2O3-PbO. Les analyses par fluorescence X ont montré que tous les échantillons incorporent une grande quantité de silice durant la synthèse. Les mesures de conductivité réalisées par spectroscopie d’impédance ont révélé une augmentation de Sigma avec le nombre d’ions F-
Li, Rong. "Preparation and ion conductivity of nano to micron grains size Bi2O3-Ln2O3 (Ln=Dy, Y, Er) ceramics." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10141/document.
Full textThe aim of this work was the study of the effect of the grain size of bismuth based oxide ceramics on the ionic properties. With the aim to prepare dense ceramics with controlled grain size at the nano-scale, nano-powders of (Bi2O3)0.75(Dy2O3)0.25, (Bi2O3)0.75(Er2O3)0.25, (Bi2O3)0.75(Y2O3)0.25 and (Bi2O3)0.75(Er2O3)0.125(Y2O3)0.125 compositions were successfully prepared by a reverse chemical titration method. As shown by XRD and TEM, after annealing for 3 hours at 500°C, powders with single crystal grains with size of about 20nm were obtained. At that stage, a b-form was evidenced for all compositions.Then, conditions of sintering were optimized. Two techniques were used: pressureless sintering in a conventional furnace and Spark Plasma Sintering (SPS). In both methods, it led to ceramics with relative density higher than 94%. The grain size was only 20nm by SPS. It ranges from 60nm to 500nm by conventional sintering, for which it was shown that the grain growth was controlled by mass transport through the grain boundaries. The effect of grain size on total ionic conductivity was studied by impedance spectroscopy for all compositions. For most compositions, a decrease of total ionic conductivity with grain size was observed due to a predominant blocking effect of grain boundary when grain size decreases. However (Bi2O3)0.75(Y2O3)0.25 with grain size of 22nm showed a better conductivity than ceramics with grain size of 62nm and a better separation of bulk and grain boundary response. At such a low size, the space charge layers effect between grains can not be neglected anymore and the observed increase in conductivity is likely the results of an increase of the conductivity in this space charge layers
Medeiros, Marta Eloisa. "Estudo de materiais a base de bismuto (III) : sistema Bi2O3-V2O5 modificado pela incorporação de metais alcalinos terrosos." [s.n.], 1995. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249025.
Full textTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
Omari, Mahmoud. "Matériaux conducteurs anioniques au sein des systèmes Bi2O3-M2O3-Pb0 (M=Y, Sm) : Stabilité thermique et propriétés électriques." Lille 1, 1989. http://www.theses.fr/1989LIL10160.
Full textGiraud, Sophie. "Nouvelles phases du système PbO-Bi2O3-M2O5 (M=P) : synthèses, structures, caractérisations et phases homologues (M=V, As)." Lille 1, 1999. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1999/50376-1999-335.pdf.
Full text設樂, 一希. "Bi2O3およびその固溶体における酸化物イオン伝導". Kyoto University, 2015. http://hdl.handle.net/2433/199516.
Full textLIU, CHUAN-YU, and 劉荃予. "Bi2WO6/Bi2O3 composites synthesis and the photocatalytic properties evaluation." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/u8p6g7.
Full text國立高雄應用科技大學
化學工程與材料工程系博碩士班
104
This study synthesized bismuth tungstate (Bi2WO6) via the solvothermal method, ethylene glycol was used as the solvent, bismuth nitrate and sodium tungstate were the precursors. Moreover, this study employed the excess addition of bismuth nitrate to form Bi2O3 during the synthesis of Bi2WO6, the modified photocatalyst was Bi2O3/Bi2WO6. The mole of Bi2O3/Bi2WO6 at 0.05, 0.1, 0.25, 0.5 and 1 was denoted as 0.05BB, 0.1BB, 0.25BB, 0.5BB and 1BB, respectively. The photocatalytic activity of the Bi2O3/Bi2WO6 was determined by the photodegradation of C.I. Reactive Red 2 (RR2). The effects of pH value and RR2 concentration on RR2 decolorization were also evaluated herein. The surface properties of Bi2O3/Bi2WO6 were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy (UV-vis), photoluminescence (PL), zeta potential meter, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The crystallinity of Bi2O3/Bi2WO6 powders was characterized by XRD. The specific surface area and the grain size of Bi2O3/Bi2WO6 composites decreased with the increasing of the Bi2O3 concentration. The diffraction pattern of pure Bi2O3 showed two crystal structures, α- Bi2O3 and β-Bi2O3. However, only β-Bi2O3 was identified in Bi2O3/Bi2WO6. The zero point charge of Bi2WO6 and 0.5BB was 2.2 and 3.3, respectively; hence, the adsorption of RR2 could be enhanced on the surface of 0.5BB. After 60 min reaction, the RR2 removal efficiency of Bi2WO6 under UV-Visible light and visible light was 49.7% and 17.1%, respectively; additionally, that of 0.5BB under UV-Visible light and visible light was 95.5% and 63.8%, respectively. Under UV-Visible light irradiation, the RR2 degradation rate constants of Bi2WO6 and 0.5BB were 0.0258 and 0.1952 min-1, respectively. The RR2 degradation rate constants of Bi2WO6 and 0.5BB under visible light irradiation were 0.002 and 0.0434 min-1, respectively. The RR2 adsorption efficiency increased after Bi2WO6 was modified by Bi2O3; hence, the photocatalytic activity of Bi2O3/Bi2WO6 was greater than Bi2WO6. The results of active species trapping experiment revealed that the role of hydroxyl radicals could be ignored herein and the photogenerated hole (h+) maybe was the main active species in the photocatalytic process of Bi2O3/Bi2WO6.
HUANG, WAN-JING, and 黃菀淨. "Synthesis of SnO2 Modified Bi2WO6 and the Evaluation of Photocatalytic Activity." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/d66wv8.
Full text國立高雄應用科技大學
化學工程與材料工程系博碩士班
104
This study prepared Bi2WO6 via the solvothermal method and modified Bi2WO6 by tin oxide (SnO2) doping to from SnO2/Bi2WO6. The photocatalytic activity of Bi2WO6 and SnO2/Bi2WO6 was determined by the photodegradation of C.I. Reactive Red 2 (RR2) under a 400 W Xe lamp irradiation. The surface characteristics of prepared photocatalysts were determined by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy (UV-vis), zeta potential meter, Fourier-transform infrared spectrometer (FTIR), and photoluminescence spectrometer (PL). The results of XRD indicated that all of the diffraction peaks of prepared photocatalysts match the standard data of Bi2WO6. After the SnO2 doping, the intensity of SnO2 diffraction peak gradually increases with the increasing of SnO2 content. The specific surface area of Bi2WO6 decreased with the increase of added SnO2 does in solvothermal method. The UV-Vis spectra of SnO2/Bi2WO6 displayed a blue shift in the band gap transition. The results of PL indicated that SnO2 doping to form SnO2/Bi2WO6 decreased the recombination of photogenerated electrons and holes in Bi2WO6. The zero point charge (ZPC) of Bi2WO6 and SnO2/Bi2WO6 (at Sn/W = 0.5) was 2.2 and 3.4, respectively. After 60 min reaction, the RR2 photodegradation efficiency of Bi2WO6 and SnO2/Bi2WO6 (at Sn/W = 0.5) was 82.9% and 94.6%, respectively; moreover, the RR2 photodegradation rate constants of Bi2WO6 and SnO2/Bi2WO6 (at Sn/W = 0.5) were 0.0258 and 0.0463 min-1, respectively. The results of active species trapping experiments revealed that photogenerated hole (h+) was the major active species in the photocatalytic process of Bi2WO6 and SnO2/Bi2WO6. The recycling runs of RR2 photodegradation over Bi2WO6 and SnO2/Bi2WO6 were performed to evaluate their photocatalytic stability. The RR2 photodegradation in Bi2WO6 and SnO2/Bi2WO6 (at Sn/W = 0.5) systems decreased from 82.9% to 63.9% and 94.6% to 89.3% after three recycling runs. The reusability and stability of SnO2/Bi2WO6 exceeded that of Bi2WO6.
Hsu, Ming-Ju, and 許銘儒. "Synthesis of Nonmetal Modified Bi2WO6 and the Evaluation of Photocatalytic Activity." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/29898838371761964946.
Full text國立高雄應用科技大學
化學工程與材料工程系博碩士班
103
This study synthesized Bi2WO6 via the hydrothermal method. The effects of reaction solvent, pH value, heating temperature and time in hydrothermal method were evaluated. In order to enhance photocatalytic activity, Bi2WO6 was modified by boron (B) or carbon nanotube (CNT) doping. The photocatalytic activity of Bi2WO6 was determined by the photocatalytic degradation of C.I. Reactive Red 2 (RR2) under visible light (450 W Xe lamp) irradiation. The prepared photocatalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectroscopy (UV-vis), photoluminescence (PL), zeta potential meter, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). According to the calculation of Scherrer equation, the grain sizes of Bi2WO6 prepared by ethylene glycol (EG) and water as solvent was 17.5 and 8.0 nm, respectively. The specific surface area of Bi2WO6 increased with the increase of added EG dose in hydrothermal method. The PL results showed that B and CNT doping decreased the recombination rate of photogenerated electrons and holes in Bi2WO6. The zero point charge (ZPC) of Bi2WO6 that modified by B and CNT was 3.7 and 4.6, respectively. The optima condition to prepare Bi2WO6 was used EG as solvent and heated at 160 ℃ for 12 hours. The RR2 removal efficiency of prepared Bi2WO6 was 95% after 60 min reaction. The RR2 removal efficiency was enhanced to 95.9 and 98.9% after Bi2WO6 was modified by B and CNT doping, respectively. The RR2 degradation rate constants of Bi2WO6, B and CNT modified Bi2WO6 were 0.049, 0.098 and 0.074 min-1, respectively. The results of active species trapping experiment revealed that photogenerated hole (h+) was the main active species in the photocatalytic process of Bi2WO6.
LAN, WANG-NING, and 藍婉寧. "Catalytic performance for methanol steam reforming over CuO/Bi2WO6 catalyst effect of oxygen vacancies." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/67844976532928637401.
Full text東吳大學
化學系
105
In this thesis, copper as an active center to prepare CuO/Bi2WO6 catalyst over steam reforming of methanol reaction (SRM) is used. Bi2WO6 is selected as a functional support based on its oxygen vacancy nature, these oxygen vacancies can provide oxygen atoms to yield reaction intermediates and further improve reaction activity. In this research, we use impregnation method to prepare two series of catalysts that denoted as m•CuO/Bi2WO6_8hr and m•CuO/Bi2WO6_20hr (m = 5, 10, 20, 30, 40 wt%, CuO weight %), respectively. The crystalline, surface area, morphology, reduction properties, surface composition and catalytic activity can be characterized by PXRD, BET, GCMS TPR, SEM and XPS. Before steam reforming of methanol reaction, all catalysts were pretreated with 7% H2/N2 gas-flow at 340oC for 1h to make sure all copper oxides (Cu2+) were reduced into metallic copper (Cu0-1). The SRM reactions were carried out over m•CuO/Bi2WO6 catalysts under temperature ranged from 160 to 300oC. During SRM reaction, methanol molecules adsorb over Cu-Bi2WO6 interface then transforms into methoxy ions and undergo dehydrogenation to yield formate ions. By adding oxygen atoms, provided form Bi2WO6 support, this step can significantly reduce the RDS activation energy of the reaction and produce intermediates, which in turn produce H2 and CO2 to complete the reaction. Keywords : CuO, Bi2WO6, Steam reforming of methanol reaction (SRM), Hydrogen production
WANG, CHIEN-WEI, and 王建緯. "Application of Ag-doped Bi2WO6/graphene and flower-like CuS/ZnS composite for photocatalytic H2 production." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3y6v9y.
Full text逢甲大學
化學工程學系
106
In the first part of this study, Ag doped Bi2WO6/graphene composite photocatalyst was prepared by solvothermal method. Ag-doped Bi2WO6-graphene based photocatalysts were found to exhibit hydrogen production activity. The performance of Bi2WO6-graphene based photocatalysts were investigated and optimized in this study. The activity can be further improved by Ag-doping. The morphology, surface chemistry, and phase structure of the photocatalysts were investigated by Field emission scanning electron microscopy, Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectra, and X-ray diffraction. UV−vis diffuse reflectance spectroscopy and zeta potential were measured to study the optical properties, bandgap and dispersion stability of the photocatalysts. The effects of forming Bi2WO6-graphene contact and Ag doping on the light absorption, band gap, dispersion stability, and photocatalytic H2 production performance of the composite photocatalysts were evaluated. The improved photocatalytic performance is mainly owing to the Ag doping and high electrical conductivity of graphene. In the second part of this study, a flower-like CuS/ZnS composite photocatalyst was prepared. Its crystal structure, morphology, surface chemistry, optical properties, photocurrent, and photocatalytic hydrogen production activity were investigated. The TEM image shows that the flower-like CuS and ZnS have good interface contact, which can promote the migration of photoelectrons and holes and improve the photocatalytic activity. The formation of p-n junction of flower-like CuS/ZnS leads to the enhanced separation of photogenerated electron-hole pairs and improved photocatalytic hydrogen production efficiency. The optimized flower-like CuS/ZnS photocatalyst (C-Z75) exhibits the maximum hydrogen production efficiency of 2931 μmol h-1g-1, which is 2.28 times higher than that of pure ZnS.
I-TingChen and 陳俋廷. "High Pressure Photoreduction of CO2: g-C3N4/Bi2WO6/rGO prepared by a microwave-assisted-hydrothermal method." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/t7u47v.
Full text國立成功大學
環境工程學系
107
In recent years, the greenhouses gases (i.e., excessive CO2 emission) led to serious global climate change problems, e.g., greenhouse effect and extreme climate. Among various techniques for reduction of CO2 emissions, the photocatalytic conversion of CO2 into chemicals or fuels is considered one of the promising strategies to address this problem. Thus, it is important to explore a photocatalyst with stability, high efficiency, and low cost. In addition, considering most of the research about CO2 photoconversion was conducted at normal pressure, the effects of high pressure on photoreduction of CO2 are investigated in this study. In this work, photocatalytic reduction of CO2 to CO using modified GCN (denoted as MCN) and 3%rGO/MCN/Bi2WO6-Y% (Y = 25, 50, 75, 100) which are prepared via a microwave-assisted route is reported. The physical-chemical properties and morphology of the photocatalysts are characterized by various analytic tools and spectroscopies, including XRD, XPS, TEM, SEM, PL, FTIR, and UV-visible spectroscopy. For MCN samples, structure and morphology of the GCN can easily be modified by a microwave-assisted hydrothermal method in an ammonia solution at different temperatures (130, 150, 170, 190) for 60 min. The obtained pale-yellow samples, MCN-X are used as photocatalysts in the CO2 photoreduction under the light irradiation. Among the samples, the MCN130 sample shows the highest CO yield of 4.22 μmol/g. For the heterostructured catalysts, 3%rGO/MCN/Bi2WO6-Y% (Y = 25, 50, 75, 100) samples are also successfully synthesized through a microwave system. In the photocatalytic CO2 reduction experiments, it was found that the 3%rGO/MCN/Bi2WO6-100% possesses the superior activity (CO yield = 13.5 μmol/g) within 12 h. The reason may be due to the 3%rGO/MCN/Bi2WO6-100% possesses a smaller band gap, and higher surface area compared to other 3%rGO/MCN/Bi2WO6-Y% (Y= 25, 50, 75). In addition, the effects of different operating pressures on the photoreduction of CO2 catalyzed by 3%rGO/MCN/Bi2WO6-100% are also discussed.
Wen-TingTang and 湯雯婷. "Microwave-assisted synthesis of g-C3N4/ Bi2WO6/ rGO for photocatalytic degradation of ibuprofen under visible light." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/mq43xf.
Full textCheng, Meichun, and 鄭美君. "Synthesis and properties of nano Bi2WO6 photocatalysts and peroxymonosulfate advanced oxidation processes degradation with triphenylmethane dyes about efficiency and mechanisms." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/77441204729821280150.
Full text國立臺中教育大學
科學應用與推廣學系科學教育碩士班
99
Two topics were discussed in this study, including homogeneous and heterogeneous reactions in the degradation of dyes. In the first part, the sulfate radical-based advanced oxidation technology was shown significant potential for environmental remediation to treat dye wastewater. The AOPs proceeded by Cobalt (Ⅱ) activation of peroxymonosulfate (PMS), i.e. Oxone for the Acid Blue 1 (AB1) dye, was studied in this work. It was observed that the degradation of AB1 in the Co2+/PMS system proceeded very fast and just required small amount of oxidant. It was found that the reaction rate of AB1 was influenced by the concentration of dye and the oxidant PMS. In order to obtain a better understanding of the mechanistic details of AB1 dye degradation reaction in the Co2+/PMS system, the intermediates were separated, identified and characterized by HPLC-PDA-ESI-MS technique. According to the following chromatogram and spectrum of TIC, at the 35-50minutes, there was no UV-absorption and the intermediates might be a definite opportunity to further collide with another radical intermediate (R• or ROO•) to yield a macro-molecule. Probable degradation pathways were proposed and discussed. Second, Bi(NO3)3‧5H2O and H2WO4 were prepared as the starting materials, and the reaction mixture were kept at 160℃ for 24h, 48h and 72h for hydrothermal and autoclave hydrothermal methods. The Microwave hydrothermal method was also treated at 160℃ but for 15min, 30min, 1h and 1.5h. The as-prepared samples were characterized by field emission scanning electron microscopy- energy dispersive X-ray spectrometer (FESEM-EDS), X-ray diffraction technique (XRD), and High resolution X-ray photoelectron spectroscopy (HRXPS). Sheet-like flowers, square-plates, irregular nanoplates, and nanopowders bismuth tungsten oxide photocatalyst, Bi2WO6, was successfully synthesized by different hydrothermal methods, including autoclave hydrothermal (AH), microwave hydrothermal (MH), and hydrothermal (H) respectively. The characteristic binding energy value of 159.0 eV for Bi 4f7/2 revealed a trivalent oxidation state for bismuth. The binding energy shift of 156.4 eV for Bi 4f7/2 was clearly observed, suggesting the Bi(+3-x) formal oxidation state being attributed to the substoichiometric forms of Bi within the Bi2O2 layer for sheet-like flowers and square-plates structures. The photocatalytic activities of the as-synthesized samples were evaluated by the photodegradation of crystal violet (CV) dye under UV-light irradiation (365 nm). Both the hydrothermal reaction temperature and time affected the crystallinity and morphology of the prepared catalysts, which in turn affected their degradation efficiency. A large number of the photodegradation intermediates were separated and characterized by HPLC-PDA-ESI-MS techniques. Based on these products, the probable degradation pathways were proposed and discussed. In this study, the topic is to compare the difference of photocatalytic efficiency and mechanisms of CV with these three different Synthesis methods.
Chang, Yu-Hsueh, and 張鈺雪. "Stabilization of Bi2O3 High Temperature Phase." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/36340447212717411983.
Full text國立臺灣海洋大學
材料工程研究所
103
The stabilization of high temperature equilibrium δ-Bi2O3 phase to room temperature was carried out by high energy ball milling of Ta- or Ta2O5-doped α-Bi2O3 powder mixtures under environment with different oxygen level. The structures of the as-milled Bi2O3-based powder were examined by X-ray diffraction analysis, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The experiments performed under 21% O2 atmospheric environment revealed that new crystalline phases formed inside as-milled 5 wt % Ta2O5-doped α-Bi2O3 powder at different milling times via the sequence of β-Bi7.8Ta0.2O12.2 δ-Bi2O3 and β-Bi7.8Ta0.2O12.2 δ-Bi2O3 δ-Bi3TaO7 for as-milled 20 wt % Ta2O5-doped α-Bi2O3 powder. For the powders milling inside an oxygen-free glove box environment, the new crystalline phase formed for 5 wt % Ta-doped α-Bi2O3 powder is β-Bi7.8Ta0.2O12.2 and that for 20 wt % Ta-doped α-Bi2O3 powders is δ-Bi3TaO7 and Bi. Doping Ta2O5 or increasing milling time can facilitated the formation of β-type (Bi7.8Ta0.2O12.2, β-Bi2O3) and δ-type (δ-Bi2O3, and δ-Bi3TaO7) phases, which are only stable at ambient temperature. Moreover, the oxygen of milling environment was favor for the phase change of α-Bi2O3 β-Bi7.8Ta0.2O12.2. For the Ta- or Ta2O5-doped powders milling under environment with different oxygen level, Ta can promotes the formation of Bi as well as high temperature stable β-Bi7.8Ta0.2O12.2, δ-Bi2O3 and δ-Bi3TaO7 phases in a short milling period. Furthermore, increasing the amount of Ta or Ta2O5 can shorten the milling time for producing δ-Bi2O3 or δ-Bi3TaO7. The formation sequences of new crystalline phases (β-Bi7.8Ta0.2O12.2 δ-Bi2O3 δ-Bi3TaO7) inferred that the phase stability of these phases is δ-Bi3TaO7 > δ-Bi2O3 > β-Bi7.8Ta0.2O12.2. Formation of β-Bi7.8Ta0.2O12.2 crystalline phase in the beginning of milling process was attributed to only a small amount of Ta or Ta+5 ions entering the α-Bi2O3 lattice to substitute Bi+3 ions, resulting in the β-Bi7.8Ta0.2O12.2 crystalline phase with low Ta composition. With increasing milling time, more Ta or Ta+5 ions can entered the α-Bi2O3 lattice, and eventually lead to the formation of δ-Bi3TaO7 and δ-Bi2O3 phases with high Ta content. Finally, the appearance of pure Bi phase inside as-milled Ta-doped α-Bi2O3 powders indicates the reduction ability of Ta is higher than that of Ta+5 ions.