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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.
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Qin, 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.
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PdCl2/Bi2WO6 and Pd/Bi2WO6 composite photocatalysts were synthesized via a template free hydrothermal process and the respective photocatalytic activities were investigated by degradation of Rhodamine B. The new catalyst composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet visible (UV-vis) light diffuse reflectance spectra, respectively. By XRD, it was found that the loaded Pd species did not alter the crystal lattice of Bi2WO6 photocatalyst. Through the XPS spectra, it was found that the PdCl2/Bi2WO6 was successfully reduced by chemical reducing agents CH2O and N2H4, respectively, and palladium was present in the form of both metallic Pd and Pd ion spe-cies (Pd0 and Pd2+), while the Pd species in a NaBH4-reduced composite exhibited only metallic Pd species (Pd0). For the SEM images, it was observed that both classes of composites were constructed from plenty of nanoplates, which were closed packed with hierarchical structures. Furthermore, the removal efficiency of Rhodamine B was found to be influenced by parameters such as catalyst dosage, pollutant concentration and solution pH.
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Hu, 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.
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The control of environmental pollution, particularly in wastewater treatment, is one of the major concerns of the 21st century. Among the currently available pollution control technologies, photocatalysis is one of the most promising and efficient approaches to the reduction of pollutants. Graphene, a carbon nanomaterial with specific physical and chemical properties, has been reported as a promising potential new catalyst material in this field.
A Bi2WO6 photocatalyst modified with graphene oxide was synthesized in a two-step hydrothermal process. Compared with pure Bi2WO6, the modified photocatalyst with 1.2 wt% graphene oxide improved photoactivity during the degradation of rhodamine-B (RhB) dye pollutant, by facilitating the dissociation of photogenerated excitons, which in turn results in more O2- radicals.
XRD characterization showed that the modification of Bi2WO6 with graphene oxide does not affect its structure or morphology. The adsorption properties of graphene also contribute to the improvement of photoactivity. Other parameters such as catalyst dosage, temperature and solution pH are studied, with the aim to improve the efficiency of RhB removal.
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Qiao, 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.
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Semiconductor-based heterogeneous photocatalysis, as one of the advanced oxidation processes that makes use of semiconductors and inexhaustible solar light, has recently been extensively studied and applied to water decontamination. However, due to low light absorption efficiencies and severe electron-hole recombination, modifications on semiconductor structures are required in order to enhance their photocatalytic performance. Heterogeneous photocatalyst composites, taking advantage of the improved light absorption efficiency as well as the facilitated electron-hole separation at the interface between different semiconductors, have been proven to be a promising strategy. In this study, novel NaNbO3/Bi2WO6 photocatalyst composites with a type-II heterogeneous alignment were successfully prepared via a facile wet impregnation method. The as-prepared photocatalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-Vis spectroscopy (DRS), photocurrent (PC) and electrochemical impedance spectroscopy (EIS) analyses. The 30 wt% NaNbO3/Bi2WO6 composite exhibited the best performance for degrading an RhB (rhodamine B) aqueous solution under visible light irradiation (λ > 410 nm), which was ca. 40 times and ca. 2.5 times that of the pristine NaNbO3 and Bi2WO6, respectively. The improved photocatalytic activity may be attributed to the enhanced electron-hole separation efficiency in Bi2WO6 with the assistance of NaNbO_3, as well as the dye-sensitization effect of RhB itself. Radical quenching experiments revealed that h+ played the predominant role, and O2•- functioned as well to some degree. The produced intermediates during the reaction and RhB degradation pathway were speculated and investigated as well. The excellent stability and reusability were verified by repetitively running for five times. Based on experimental results, a plausible functioning mechanism was proposed. Effects of several operation parameters on the catalyst performance including initial RhB concentration, catalyst dosage, reaction temperature and initial pH were also discussed. This study provides solid evidence for NaNbO3 to be a promising candidate for photocatalysis and gives out a novel photocatalytic mechanism of Bi2WO6-based type-II heterostructures.
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Silva, 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.
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Previous issue date: 2013-02-22<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>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.<br>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.
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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.
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L'intérêt porté sur la miniaturisation des systèmes par la communauté scientifique est grand, que ce soit pour des raisons de mobilité, d'économie d'énergie ou d'innovation technologique. L'objectif de cette thèse est de déterminer les caractéristiques physiques et structurales des couches minces et des nanofils d'oxydes métalliques synthétisés par la méthode électrochimique. La première partie de cette thèse est consacrée à l'oxyde de bismuth en phase delta. Les couches minces élaborés par électrochimie sont de très bonne qualité cristalline, et seul la phase delta- Bi2O3 est présente. Le caractère nano structuré des couches minces est mis en évidence par les expériences de microscopie électronique en transmission (MET) et participe à la stabilisation de cette phase à température ambiante. Les mesures de conductivité réalisées par spectroscopie d'impédance complexe montrent un comportement différent selon la nature du substrat utilisé. Nous observons une excellente conductivité électrique des dépôts réalisés sur les substrats en argent doré (4*10-3 S*cm-1), alors que les dépôts obtenus sur l'inox montre un comportement très résistif (10-7 S*cm-1). La seconde partie de cette étude concerne l'oxyde de zinc. Les conditions d'élaboration par électrochimie influence les propriétés structurales et physiques des couches minces obtenues. Les différents traitements thermiques réalisés sur les couches minces de ZnO ont permis d'améliorer la qualité optique des couches et de modifier la structure du ZnO par incorporation d'azote lors de recuit dans l'ammoniaque. La dernière partie est consacrée à la synthèse et à la caractérisation de nanofils de ZnO élaborés par la méthode " template ". Cette méthode nous a permis de confiner la croissance par électrochimie dans des pores de différents diamètres. Les observations réalisés par MET et MET en Haute Résolution montrent que les nanofils obtenus sont monocristallins et de bonne qualité. Les propriétés d'émission observées en PL sont très proches des propriétés d'émission des couches minces
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MATOS, Lucyene Nascimento. "Estudo de fases cristalinas no sistema Bi2O3-Tb4O7." Universidade Federal de Goiás, 2009. http://repositorio.bc.ufg.br/tede/handle/tde/821.
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Previous issue date: 2009-08-25<br>A 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<br>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
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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.
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silva_fg_me_ilha.pdf: 1536045 bytes, checksum: 5e52a7e90e9528b73306cfd4b593e9d3 (MD5)<br>Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)<br>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<br>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
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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.
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Orientador: Keizo Yukimitu<br>Banca: Ezequiel Costa Siqueira<br>Banca: Américo Sheitiro Tabata<br>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<br>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<br>Mestre
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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.
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Moore, Katharine. "Preparation and characterisation of mixed CeO2-Nb2O5-Bi2O3 nanoparticles." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252691.
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Mixed metal oxides are ionic compounds containing at least two metal ions within an oxide structure. The literature contains a plethora of examples of mixed metal oxides on the bulk scale, which have been well characterised, however, mixed metal oxides on the nanoscale are far less well understood. The work presented here investigates the Bi2O3-CeO2-Nb2O5 mixed oxide system and characterises the resulting nanoparticles and crystal structures. Although the parent oxides are well known and much work has previously been done in analysing their crystal structures, combinations of these oxides have not been well characterised, especially on the nanoscale. Using high resolution electron microscopy (HRTEM), powder X-ray diffraction (PXRD), electron dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) as analytical tools, the structures of the nanoparticles in this system have been explored. As each of the parent oxides possess useful properties, which have been utilised in industrial applications such as electrolyte components in solid oxide fuel cells and as catalysts in a range of chemical reactions, it was hypothesised that if all three metal ions could be contained in one particle they could show novel and interesting characteristics. It was proposed that due to the more relaxed crystal structure in nanoparticles, the solid solubility of the metal ions should be increased, and a solid solution of ions would form. This work presents results showing the synthesis of binary and ternary oxides in the nano-form within the Bi2O3-CeO2-Nb2O5 system, including quantitative analysis of these particles. Secondly, and most importantly, it presents the first successful synthesis of quaternary oxide nanoparticles containing bismuth, cerium and niobium using the low temperature resin-gel method. Finally, the work attempts to explain how and why the ions are ordered in a given arrangement, with bismuth showing a preference for surface site occupation, as shown by XPS data, and describes some preliminary computational results which corroborate the experimental data.
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Oudich, 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.
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Le présent travail de recherche s’inscrit dans un projet global, dont le but est de comprendre et résoudre un problème de corrosion d’un acier dit T91 par un mélange métallique liquide de plomb et bismuth. Il présente un intérêt pour la communauté nucléaire qui envisage de développer une nouvelle génération de réacteurs dits ADS. Ce travail est une contribution à l’étude thermodynamique d’un système plus complexe composé de plusieurs éléments : Al, Bi, Pb, Fe, Cr et l’oxygène. Plus précisément, il a été focalisé sur les systèmes à base de mélanges d’oxydes Bi2O3 + PbO + Al2O3 et Bi2O3 + PbO + Fe2O3. Un travail expérimental a été accompli, au cours duquel ces mélanges à différentes proportions ont été recuits à une température supérieure à 600 °C pendant plusieurs jours, suivi de l’analyse des échantillons par des techniques de pointe. Il a permis de découvrir les différents produits formés dans les différentes conditions de température, de compositions et atmosphères. Les résultats ont permis de faire aussi une modélisation à l’aide d’un outil informatique. Tout cela aide à mieux comprendre et anticiper la formation des produits de corrosion de l’acier par le mélange métallique liquide<br>This 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
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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.
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Photocatalysis has received increasing attention in recent years as an effective technology in wastewater treatment applications. In this project, bismuth molybdate (Bi2MoO6), which is a popular visible-light-driven photocatalyst, was prepared by solvothermal and hydrothermal methods. The synthesis conditions, including thermal reaction temperature, synthesis duration, and precursor stirring time of the solvothermal method were optimized based on the photodegradation of Rhodamine B (RhB) under visible light irradiation. Furthermore, the CeO2/Bi2MoO6 composites with different CeO2 loading content were successfully prepared by the wet impregnation route and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS) and diffuse-reflection spectroscopy (DRS). The photodecomposition of RhB aqueous solution under visible light irradiation indicated that composites showed enhancements in degradation activity and 20 wt% CeO2/Bi2MoO6 exhibited the highest photocatalytic activity which was 24.13% and 83.33% higher than those of Bi2MoO6 and CeO2, respectively. This enhancement could be attributed to the formation of heterojunctions that effectively suppressed the recombination of holes and electrons. Quenching experiments revealed that photo-induced holes and superoxide radicals (O2•-) were the main active species during the degradation process. Reusability was assessed by a set of 5 cycling degradation experiments and the results indicated that the composite could be applied long-term. Moreover, the effect of some operating parameters including temperature, initial pH, catalyst dosage and initial substrate concentration were investigated.
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Bourja, Lamia. "Étude du système CeO2-Bi2O3 pour applications catalytiques et conductimétriques." Phd thesis, Toulon, 2011. http://tel.archives-ouvertes.fr/tel-00659119.
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Dans le cadre général des études de matériaux multifonctionnels, électrolytiques et catalytiques, susceptibles d'être utilisés au sein de dispositifs de détection de gaz, un système d'oxydes (1-x)CeO2. x/2Bi2O3 avec 0≤x≤1 a été élaboré par coprécipitation puis traitement thermique à 600°C. Le système ainsi obtenu correspondrait à un diagramme de phases original, constitué d'un domaine de solutions solides (Ce1-xBixO2-z pour x ≤ 0,20), d'un domaine multiphasé pour 0,3≤x≤0,7 comportant une phase de type quadratique b'-Bi2O3 et une phase cubique substituée limite (x=0,20), d'un autre domaine multiphasé pour les compositions 0,8≤x≤1, comportant une phase quadratique b-Bi2O3 et une phase monoclinique. Ces deux phases ont déjà été considérées dans la littérature comme phases métastables résultant de divers modes de refroidissement de la phase pure Bi2O3. Dans le cas présent, la stabilisation de ces deux phases b' et b en présence d'une phase substituée cubique Ce1-xBixO2-z pourrait être due à la présence d'ions cérium au sein duréseau cristallin de Bi2O3. Les interactions catalytiques entre des échantillons polycristallins de ce système avec x variable et des mélanges air-CO et air CH4 ont été étudiées par spectroscopie infrarouge à transformée de Fourier dans le domaine 100 à 525°C. Il apparait que les composés riches en cérium ou riches en bismuth n'ont pas la même réactivité vis-à-vis des gaz CH4 ou CO. Cette diversité de propriétés catalytiques pourrait être utilisée au sein de systèmes multicapteurs de gaz.Une étude de la conduction électrique du système pour x variable a été effectuée par spectroscopie d'impédance électrique entre 100 et 750°C. Les représentations Nyquist des impédances électriques ont été interprétées en mettant en jeu des modèles de type élément de phase constante ou de type Warburg pour prendre en compte l'hétérogénéité des échantillons ainsi que les phénomènes de réaction-diffusion aux électrodes. La conductivité en volume (coeur de grains) augmente avec la composition, avec deux types d'évolutions distinctes : une évolution caractéristique de la phase substituée liée à l'augmentation du taux de lacunes, une évolution dans le système biphasé avec une forte augmentation de conductivité au-dessus de x=0,3 et un maximum atteint pour x=0,7. La phase quadratique de type b'-Bi2O3 connue comme phase métastable est ainsi stabilisée au sein de ce système mixte, au moins à 600°C: elle serait à l'origine de la forte conductivité ionique observée pour la composition proche de x = 0,7.
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Webster, 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.
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[Truncated abstract] New, double-doped, Bi2O3-based materials in the Bi2O3 Ln2O3 PbO (Ln = La, Nd, Er and Yb) and Bi2O3 WO3 PbO systems were prepared using solid-state reactions. For the Bi2O3 Er2O3 PbO and Bi2O3 Yb2O3 PbO systems, the air-quenchable compositional domain of the fcc fluorite-type phase was partially established. Temperature dependent conductivity measurements were performed on these quenched-in fluorite-type materials using AC impedance spectroscopy. Conductivity at 750[degrees Celsius] generally increased with increasing Pb2+/Ln3+ and decreasing (Ln3++Pb2+)/Bi3+ ratios. The material (BiO1.5)0.70(ErO1.5)0.15(PbO)0.15 had a conductivity of 0.66 [plus-minus] 0.05 S cm-1 at 750[degrees Celsius], placing it among the most highly conductive Bi2O3-based materials, and was the best new fluorite-type material from a combined conductivity and structural stability viewpoint. Some of the new materials in the Bi2O3 La2O3 PbO and Bi2O3 Nd2O3 PbO systems appeared to have the quenched-in fluorite type structure based on powder X-ray diffraction data. These materials had very high conductivities at 750[degrees Celsius] of `~ 1 S cm-1, but underwent rapid symmetry lowering transformations during heating, thus making them unsuitable for use as solid electrolytes. The fluorite-type structure was not air-quenchable in the Bi2O3 WO3 PbO system, for the compositions synthesised. Room temperature neutron powder diffraction data were collected for quenched-in fluorite-type materials in the (BiO1.5)0.80(LnO1.5)0.20-x(PbO)x, Ln = Er and Yb, x = 0, 0.03, 0.06 and 0.09, and (BiO1.5)0.97-y(ErO1.5)y(PbO)0.03, y = 0.27, 0.17 and 0.12, series. ... This suggests that Pb2+ dopant cations occupy face-centre positions in the fcc unit cell, and the Pb2+ lone pair electrons are likely to be orientated towards an oxide ion vacancy in an adjacent tetrahedral site. Pb2+/oxide ion vacancy interactions affect the migration of oxide ions/oxide ion vacancies through the structure, and are responsible for the significantly larger activation energy for oxide ion migration in the Pb2+-doped materials relative to the Pb2+-free materials. For example, the activation energies of (BiO1.5)0.80(ErO1.5)0.20-x(PbO)x, x = 0.03 and 0.06, were 1.50 [plus-minus] 0.02 and 1.54 [plus-minus] 0.02 eV, respectively, while the activation energy for (BiO1.5)0.80(ErO1.5)0.20 was 1.25 [plus-minus] 0.04 eV. Long-term annealing of the quenched in fluorite-type materials in the Bi2O3 Er2O3 PbO and Bi2O3 Yb2O3 PbO systems at 500 and 600[degrees Celsius] resulted in conductivity lowering structural transformations, making these materials unsuitable for practical use as solid electrolytes at these temperatures. For example, the materials (BiO1.5)0.80(ErO1.5)0.20-x(PbO)x, x = 0.03, 0.06 and 0.09, underwent a fluorite-type to tetragonal transformation during annealing at 500[degrees Celsius] due to <100> oxide ion vacancy ordering, and the rate of conductivity decay at 500[degrees Celsius] increased with increasing Pb2+/Er3+ ratio. Long-term annealing experiments at 500[degrees Celsius] performed on air quenched (Bi2O3)0.705(Er2O3)0.245(WO3)0.050 showed that the disordered fluorite-type structure of this material was not fully stabilised, as evidenced by the presence of superlattice reflections in selected area electron diffraction patterns for the material annealed for 2000 hours, and a gradual conductivity decay after ~ 150 hours annealing.
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Bégué, Pascale. "Matériaux originaux en relation avec Bi2MoO6 : nouvelles voies de synthèse, études structurales et propriétés électriques." Toulouse 3, 2001. http://www.theses.fr/2001TOU30017.
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FERREIRA, 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.
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Previous issue date: 2008-08-18<br>I
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.<br>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
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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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Previous issue date: 2015-06-15<br>CAPES<br>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.<br>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.
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Sirota, Ben. "Synthesis and Characterization of ZnO and Bi2O3 Nanowires Grown by Magnetron Sputtering." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/766.
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Nanowires of Zinc oxide and bismuth oxide were grown on silicon substrates using vapor-liquid-solid (VLS) and unbalanced magnetron sputtering. Characterization using x-ray diffraction (XRD) and scanning electron microscopy (SEM) was conducted to investigate how growth conditions influence the structural and morphological properties of the materials. Optical properties were investigated using photoluminescence (PL), direct absorption spectra and cyclic voltammetry. The physical properties of sputtered ZnO were found to be dependent on oxygen flow rate, temperature, and the initial foreign metal catalysis seed layer. Nanowires were grown using a two-step process whereby an initial Au layer was deposited followed by Zn with oxygen. Doped ZnO-TiO2 nanostructures were created by sputtering Ti and Zn simultaneously. Homo- and hetero-structured ZnO-ZnO and ZnO-TiO2 were created using additional sputtering cycles. A systematic approach was taken to produce nanoarrays of Bi2O3 by adjusting initial seed layer thickness and oxygen flow rates. A two step process involving variable oxygen flow rates was found to create the highest density of Bi2O3 nanowires in the array. Top-view and cross-sectional SEM micrographs suggested that the resulting Bi2O3 nanowires were approximately 300 nm in length with diameters of 100 nm at the base and 30 nm at the top. Investigation into the growth method suggests a self-catalytic VLS-like process. Degradation tests using rhodamine 6G dye were compared to SEM images. Samples of ZnO and Bi2O3 displayed a direct correlation between nanowire density and photocatalytic efficiency.
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Durand, 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.
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Ce travail visait à élucider la structure de composés métastables désordonnés mis en évidence dans la partie riche en TeO2 du système TeO2-Bi2O3. L’étude a été menée principalement par diffusion Raman, diffusion totale des neutrons et modélisation structurale par la méthode de Monte Carlo inverse. Ces phases possèdent des structures de symétrie moyenne cubique, constituées d’entités TeO4 et TeO3, enchaînées de sorte que les cations forment un réseau CFC bien défini jusqu’à des distances de quelques centaines de nm. Le réseau d’anions est presque totalement désordonné. L’analyse de la largeur des raies de DRX montre qu’avec le taux croissant en TeO2, le réseau cationique est de moins en moins bien formé. Au-delà d’un certain taux de TeO2, ces phases évoluent vers des phases de symétrie moyenne orthorhombique constituées de chaînes polymérisées d’entités TeO3. Cette évolution s’accompagne de l’apparition de la propriété de génération de seconde harmonique<br>This 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
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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.
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Dans le but de trouver un nouvel électrolyte pour les piles à combustible SOFC fonctionnant à basses températures, nous nous sommes intéressés au nouveau mode de synthèse électrochimique de la phase delta de l'oxyde de bismuth. d-Bi2O3 est connu comme le meilleur conducteur ionique, mais sa gamme de stabilité thermique réduite (729 ? 825°C) a freiné son utilisation. La méthode proposée par Switzer et al. permet de stabiliser cette phase à température ambiante. Cela relance l'intérêt d'étude pour ce matériau en vue d'une application comme électrolyte solide des piles à combustible. Nous avons tout d'abord étudié l'influence des paramètres de la synthèse de couches minces. Nous en avons déduit qu'une température de plus de 50°C était nécessaire et que les conditions étaient optimales avec une température de 65°C. La valeur du pH du bain doit être supérieure à 14. Pour l'électrodéposition, nous avons retenu un courant imposé constant entre 400 et 600 µA. Nous avons réalisé cette synthèse sur des substrats de nature variée (platine, inox, inox doré, or massif, argent doré). A l'aide de la diffraction des rayons X et de la microscopie électronique en transmission à haute résolution, nous avons confirmé la structure polycristalline de d-Bi2O3. Ces méthodes nous ont également permis de montrer que tous les grains ont une taille qui varie entre 10 et 170 nm. Ces cristallites de taille nanométrique joue un rôle essentiel dans la stabilité de d- Bi2O3 à température ambiante. A l'aide de la microbalance à quartz, nous avons montré que le dépôt de d-Bi2O3 ne pouvait pas dépasser 2 µm. Nous avons montré la stabilité du dépôt d-Bi2O3 électrodéposé pour une conservation à température ambiante. Par ailleurs, l'étude de la stabilité thermique a montré que la taille des cristallites diminue avec la température de recuit et que la structure est modifiée à partir de 360°C en une structure sillenite. Nous avons montré qu'il est possible de réaliser des nanofils de d-Bi2O3. Nous n'avons pas pu déterminer des conditions optimales qui nous auraient permis de synthétiser uniquement d- Bi2O3 en plus grand nombre. Enfin, nous avons réalisé des premières mesures de conductivité. Les résultats préliminaires nous montrent un comportement ionique de nos dépôts, mais ils ne sont pas tout à fait reproductibles.
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Leandro, Silvana Castro. "Síntese e caracterização óptica de vidros da família TeO2 -B2O3 -(Bi2O3 ou WO3) /." Ilha Solteira, 2018. http://hdl.handle.net/11449/157392.
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Orientador: Keizo Yukimitu<br>Resumo: 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)<br>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.<br>Doutor
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Follet-Houttemane, Claudine. "Les phases oxyfluorées du système Bi2O3-PbO-PbF2 : stabilité - propriétés électriques - caractéristiques structurales." Lille 1, 1987. http://www.theses.fr/1987LIL10215.
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Mise en évidence de deux solutions solides ternaires : l'une de symétrie quadratique dans la partie riche en Bi2O3 du diagramme, l'autre de symétrie rhomboédrique possédant un domaine de stabilité plus étendu. Mesures de conductivité électrique effectuées par spectroscopie d'impédance : les valeurs atteintes par les matériaux de la phase quadratique sont toujours faibles, celles atteintes par ceux de la phase rhomboédrique dépendent fortement de la composition. Etudes structurales réalisées pour plusieurs compositions du domaine rhomboédrique par diffraction Rx sur monocristal et diffraction des neutrons sur poudre en fonction de la température
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Labidi, 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.
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Ce travail concerne la recherche de nouveaux matériaux à base de bismuth à propriétés spécifiques plus performantes, ou l'amélioration de propriétés de matériaux connus telles que la conduction ionique pour leur intérêt, en particulier dans le domaine énergétique. Dans le système Bi2O3-PbO-V2O5, notre travail a porté tout d'abord sur le domaine riche en bismuth. La structure du composé PbBi6V2O15 a été déterminée. Le problème de discernement par diffraction X de Bi3+ et de Pb2+ a été abordé par le remplacement du plomb par d'autres cations M2+ tels que Sr2+, Ca2+ et Cd2+. Les déterminations structurales sur monocristaux ont révélé des solutions solides. Partant de la structure connue Pb5Bi18V4O42, le remplacement du Pb par Sr, Ca et Cd a abouti à de nouvelles phases cristallines non stoechiométriques. Il s'agit dans ces différents cas de surstructures dérivées de Bi2O3-δ.<br /> L'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.<br /> 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.
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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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Previous issue date: 2016-03-04<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>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.<br>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.
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Schmidt, Samara. "Estudo da modificação na fotoluminescência em α-Bi2O3 após tratamento térmico assistido por pressão /". Araraquara, 2016. http://hdl.handle.net/11449/136399.
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Orientador: José Arana Varela<br>Co-orientador: Sergio Mazurek Tebcherani<br>Co-orientador: Diogo Pascoalini Volanti<br>Banca: Sonia Maria Zanetti<br>Banca: Marco Aurélio Cebim<br>Banca: Maximo Siu Li<br>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...<br>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.<br>Banca: Carlos Frederico de Oliveira Graeff<br>Doutor
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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.
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Afin de trouver un nouvel électrolyte pour les piles à combustible SOFC fonctionnant à basses températures, nous nous sommes intéressés au nouveau mode de synthèse électrochimique de la phase delta de l’oxyde de bismuth. -Bi2O3 est connu comme le meilleur conducteur d'ion oxygène, mais sa gamme de stabilité thermique réduite (729 – 825°C) a freiné son utilisation. La méthode électrochimique permet de stabiliser cette phase à température ambiante. Nous avons tout d’abord étudié l’influence des paramètres de la synthèse de couches minces de δ-Bi2O3. Nous en avons déduit qu’une température de plus de 50°C était nécessaire et que les conditions étaient optimales avec une température de 65°C. La valeur du pH du bain doit être supérieure à 14. Pour l’électrodéposition, nous avons retenu le mode intensiostatique avec une densité de courant comprise entre 2,25 et 3 mA/cm2. La structure polycristalline de -Bi2O3 a été confirmée par DRX et METHR. Ces méthodes nous ont également permis de montrer que tous les grains ont une taille qui varie entre 10 et 170 nm. Ces nanocristallites stabilisent δ-Bi2O3 à température ambiante. A l’aide de la microbalance à quartz, nous avons montré que le dépôt de δ-Bi2O3 ne pouvait pas dépasser 2 µm dû à son caractère isolant. Nous avons montré la stabilité des couches minces δ-Bi2O3 électrodéposées pour une conservation à température ambiante. Par ailleurs, l’étude de la stabilité thermique a montré que la taille des cristallites diminue avec la température de recuit et que la structure est modifiée à partir de 360°C en une structure sillenite. Nous avons montré qu’il est possible de réaliser des nanofils monocristallins de δ-Bi2O3. Cependant les conditions optimales d'élaboration n'ont pas été déterminées. Enfin, nous avons réalisé des premières mesures de conductivité. Les résultats préliminaires nous montrent un comportement ionique de nos dépôts. Ils montrent aussi que -Bi2O3 est un excellent conducteur, mais ils ne sont pas tout à fait reproductibles<br>With 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
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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.
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L'étude du système Bi2O3-CaO-PbO par synthèse à l'état solide, diffraction X à température variable et analyse thermique différentielle a permis la caractérisation de quatre solutions solides. La solution solide de symétrie cubique, réseau F Delta dérive de la variété Delta de Bi2O3. Béta 1 et Béta 2, de symétrie rhomboédrique, réseau I, est caractéristique d'une structure de type anti-AgI Alfa. Seule Béta 2 est stable à température ambiante. Les variétés Béta 1 et Delta peuvent être préservées, sous forme métastable, par trempe à l'air dans des domaines de composition dont les limites ont été déterminées. L'évolution de ces phases en fonction de la température a été décrite à partir des résultats de diffraction X. L'étude de leur conductivité a été réalisée par spectroscopie d'impédance sur échantillons frittés. Toutes présentent une mobilité anionique dont l'importance relative a été déterminée par des mesures de nombre de transport de O² à partir de piles de concentration en oxygène. A haute température, (phases Béta 1 et Delta) le nombre de transport est égal à l’unité. En dessous de 300°C les phénomènes sont plus complexes. Les temps de réponse aux variations de pression partielle d'oxygène sont extrêmement courts. Les valeurs des différences de potentiel sont très supérieures aux valeurs attendues. Un mécanisme de dissociation aux électrodes faisant intervenir des ions peroxydes a été proposé. Les caractéristiques des matériaux particulièrement à basse température, leur confèrent un intérêt tout particulier pour la réalisation de capteurs, soit comme électrolytes, soit comme électrodes.
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Laabidi, 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.
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Ce travail concerne la recherche de nouveaux matériaux à base de bismuth à propriétés spécifiques plus performantes, ou l'amélioration de propriétés de matériaux connus telles que la conduction ionique pour son intérêt en particulier dans le domaine énergétique. Dans le système Bi2O3-PbO-V2O5, notre travail a porté tout d'abord sur le domaine riche en bismuth. La structure du composé PbBi6V2O15 a été déterminée. Le problème de discernement par diffraction X de Bi3+ et de Pb2+ a été abordé par le remplacement du plomb par d'autres cations M2+ tels que Sr2+, Ca2+ et Cd2+. Les déterminations structurales sur monocristaux ont révélé des solutions solides. Partant de la structure connue Pb5Bi18V4O42. Le remplacement du Pb par Sr. Ca et Cd a abouti à de nouvelles phases cristallines non stoechiométriques. Il s'agit dans ces différents cas de surstructures dérivées de Bi2O3-ð[delta]. L'étude s'est prolongée au sein du binaire Bi VO4-nPbO. Une transition de phase α→β a été caractérisée pour Ie terme n=1, PbBiVO5. Les structures des cristaux «macIés» 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 ð. Les structures des formes α et β ont été déterminées sur monocristal : la résolution de la struture de β a nécessité l'emploi d'un formalisme 4D. Deux nouvelles formes α' et ð' ont été obtenues par substitution du V par Mn ou P. Leurs structures découlent des phases α à l'ambiante, et ð à 680°C. La conductivité électrique des matériaux a été étudiée et des corrélations propriétés de conduction - caractéristiques structurales proposées.
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Gong, 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.
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Rocha, 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.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior<br>CerÃmica 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.<br>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 .
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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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Previous issue date: 2016-08-18<br>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.<br>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.
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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.
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Orientador: Keizo Yukimitu<br>Resumo: 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)<br>Doutor
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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.
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Ce travail porte sur l’étude des propriétés optiques non-linéaires des phases métastables orthorhombiques dans la partie riche en TeO2 du système TeO2 - Bi2O3. Après une étude structurale de ces phases, nous nous sommes intéressés à leurs propriétés optiques non-linéaires (ONL) du 2nd ordre en effectuant des mesures expérimentales de génération de seconde harmonique (GSH). Une variation surprenante de l’intensité de GSH de ces phases avec la composition a été observée. Afin d’en expliquer l’origine, la susceptibilité ONL de 2nd ordre de ces phases a été calculée en appliquant une méthode, préalablement validée, basée sur la théorie de la fonctionnelle de la densité (DFT). Cette méthode a aussi été appliquée aux polymorphes α et γ de TeO2 et à la cristobalite SiO2 et a permis de mettre en évidence des relations entre les propriétés ONL du 3me ordre des tellurites et leurs arrangements structuraux (les entités, leurs enchaînements, la paire libre de l’atome Te)<br>This 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)
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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/.
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The work reported in this thesis is based around substitutions into bismuth oxide, which has proven to be highly adaptable chemically as it can accommodate a wide variety of substituents. The synthesis and characterisation of stabilised δ-Bi₂O₃ related materials containing small amounts of Ca, Ga, Nb and Re are described. A body of work is presented exploring the structural and physical properties of such materials, characterised by neutron powder diffraction, X-ray powder diffraction, electron diffraction, extended X-ray absorption of fine structure measurements, differential thermal analysis and impedance spectroscopy. The structure of two new fluorite-related materials, Bi₆Ca₃ReO₁₅.₅ and Bi₁₀Ca₅ReO₂₃.₅, were studied. Bi₆Ca₃ReO₁₅.₅ formed a face-centred cubic fluorite-related structure and Bi₁₀Ca₅ReO₂₃.₅ a body-centred cubic material that is a 4 x 4 x 4 superstructure of the Bi₆Ca₃ReO₁₅.₅ phase. The structure of novel isostructural materials Bi₂₀Ca₇NbO₃₉.₅ and Bi₁₀.₇₅Ca₄.₃₇₅GaO₂₂ were also investigated. Both materials formed distorted δ-Bi₂O₃ related superstructures, derived as a monoclinic supercell based on a fluorite-related hexagonal subcell. Detailed structural analysis and local environments of cations in the ordered monoclinic fluorite-related superstructure of Bi₉ReO₁₇ are also explored. All materials synthesised in this thesis have structures related to that of δ-Bi₂O₃, which is known to have high oxide ion conducting properties at elevated temperatures. Oxide ion conducting properties are therefore also described.
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Jacobsoone, 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.
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L’étude du système Bi2O3-V2O5-ZnF2 a été pour la première fois réalisée en tubes d’or scellés. Par cette méthode de synthèse, une solution solide oxyfluorée a été mise en évidence au voisinage de Bi4V2O11. Les investigations structurales réalisées par diffraction des rayons X sur poudre et par affinement de Rietveld ont montré que les échantillons appartenant à ce domaine présentaient une structure proche de celle des phases BIMEVOX. Les ions fluorures sont localisés dans les feuillets de conduction de type pérovskite. Cependant, en raison de la faible proportion d’ions F- dans tous les échantillons, la conductivité électrique reste contrôlée par la migration des ions O2-. En utilisant des creusets de quartz au lieu de tubes d’or lors de la synthèse, une phase vitreuse G et une phase cristallisée C ont été mises en évidence. L’absence de silice dans les échantillons a été contrôlée par fluorescence X. Les investigations structurales réalisées sur la phase C ont confirmé que, en accord avec l’allure des clichés de diffraction X sur poudre, la structure est apparentée à celle des phases BIMEVOX mais, des différences significatives sont aussi apparues. Tout d’abord, les ions fluorures sont apparus comme étant principalement localisés dans les feuillets pyramidaux conduisant à la formation de couches Bi2F2 4+. Le reste des ions sont localisés dans les feuillets de type pérovskite<br>Compte 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-
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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.
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L’objectif de ce travail était l’étude de l’effet de la taille des grains de céramiques à base d’oxyde de bismuth sur les propriétés de conduction ionique. Avec pour objectif la préparation de céramiques denses avec des grains de taille nanométrique, des poudres de composition (Bi2O3)0.75(Dy2O3)0.25, (Bi2O3)0.75(Er2O3)0.25, (Bi2O3)0.75(Y2O3)0.25 et (Bi2O3)0.75(Er2O3)0.125(Y2O3)0.125 ont été préparées avec succès par une méthode de dosage en retour. Des poudres avec des grains mono-cristallins d’environ 20 nm ont été obtenues, à partir desquelles, des céramiques denses ont ensuite été préparées par frittage conventionnel et par « Spark Plasma Sintering ». Par les deux méthodes, des céramiques de densités relatives supérieures à 94% sont obtenues. Par SPS, la taille des grains est de 20nm seulement. Elle varie de 60 à 500nm par frittage conventionnel pour lequel une croissance des grains contrôlée par le transport de matière aux joints de grain est démontrée.L’effet de la taille des grains sur la conductivité a finalement été étudié par spectroscopie d’impédance. Une diminution de la conductivité avec la taille des grains est généralement observée, probablement due au caractère bloquant des joints de grain. En revanche, la composition (Bi2O3)0.75(Dy2O3)0.25 avec des grains de 22nm présente des conductivités au dessus de celles de la céramique de même composition avec des grains de 62nm et une meilleure séparation des réponses dues aux grains et aux joints de grains. Pour des tailles de grains aussi faibles, les couches d’espace de charge entre les grains ne peuvent plus être négligées et le phénomène observé est probablement dû à une augmentation de la conductivité dans ces couches<br>The 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
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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.
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Orientador: Oswaldo Luiz Alves<br>Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica<br>Made available in DSpace on 2018-07-20T17:15:35Z (GMT). No. of bitstreams: 1
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Previous issue date: 1995<br>Doutorado
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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.
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Les investigations réalisées au sein du tertiaire Bi2O3-M2O3-Pb0 ont permis la mise en évidence d'une solution solide de symétrie cubique à faces centrées, lacunaires en ions O2, de type delta-Bi2O3. Par trempe à l'air, celle-ci peut être préservée à température ambiante dans un large domaine de composition. La diffraction x en fonction de la température a permis de montrer que, pour des concentrations en Y3+ et Pb2+ suffisante, la structure delta Bi2O3 était conservée lors du chauffage jusqu'au domaine d'équilibre à haute température. Il existe cependant une rupture de pente sur la courbe de variation du paramètre de maille, caractérisant l'existence d'un léger réarrangement structural. Les mesures de conductivité électrique et de nombre de transport des ions O2 ont permis de mettre en évidence une conductivité anionique importante (sigma=0,43 /ohm /xcm pour Bi1,53Pb0,27Y0,2O2,622 à 720°C). L'évolution de la conductivité en fonction de la température est en bon accord avec la présence de deux variétés de la solution solide delta. L'effet potentialisateur de Pb2+ a été mis en évidence par l'augmentation de la conductivité et de la stabilité lorsque le rapport Pb2+/(Pb2+ + Y3+) s'accroit. Une étude du système Bi2O3-Sm2O3-Pb0, a permis également de mettre en évidence une solution solide de type delta-Bi2O3. Alors que le domaine de trempe est un peu plus étendu qu'avec Y2O3, le sous-domaine au sein duquel les échantillons gardent au chauffage la structure delta est beaucoup plus restreint. L'évolution relative de sigma en fonction de la composition reflète celle rencontrée au sein du précèdent système
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Giraud, 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.
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Plusieurs nouveaux oxyphosphates de bismuth et de plomb ont été synthétisés lors de l'étude du système ternaire PbO-Bi2O3-P2O5 ; des études structurales par diffraction des rayons X ont été essentiellement effectuées. Pb4BiPO8 cristallise dans une maille triclinique (groupe d'espace P 1) et sa structure présente de nombreuses similitudes avec celles de alpha-PbO et Pb5SO8. L'utilisation d'un rayonnement à courte longueur d'onde (source synchrotron) permet de s'affranchir du phénomène d'absorption et augmente la précision des résultats. PbBiPO5, de symétrie triclinique, subit une transformation allotropique à 725°C. La forme haute température possède une maille monoclinique C. L'existence du compose PbBi6P4O20 a été confirmée et sa structure affinée sur poudre à partir des données structurales de la phase haute température isotype Bi6,67P4O 20. L'atome de plomb occupe alors totalement le site occupe aux 2/3 par un atome de bismuth dans la structure de Bi6,67P4O20. Les homologues isomorphes PbBi6V4O20 et PbBi6As4O 20 ont été mis en évidence. Pb5Bi18P4O42, surstructure de la phase fluorine delta-Bi2O3, cristallise dans une maille monoclinique I. La structure a été résolue dans le groupe d'espace I2/m à partir de données collectées au synchrotron (à courte longueur d'onde). Les atomes de plomb, bismuth et phosphore occupent sensiblement les mêmes positions que ceux du bismuth dans delta-Bi2O3. Pb10Bi33,33P10O85, de maille monoclinique centrée, présente également une surstructure de delta-Bi2O3. La substitution totale du phosphore par le vanadium et l'arsenic conduit à des composés isomorphes Pb5Bi18V4O42, Pb5Bi18As4O42, ainsi que Pb10Bi33,33V10O85 et Pb10Bi33,33As10O85. La conductivité de toutes ces phases a été mesurée. Les vanadates présentent une meilleure conductivité que leurs homologues isoformulaires. Les phases plus riches en bismuth et structurellement liées à delta-Bi2O3 sont meilleures conductrices.
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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.
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LIU, CHUAN-YU, and 劉荃予. "Bi2WO6/Bi2O3 composites synthesis and the photocatalytic properties evaluation." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/u8p6g7.
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碩士<br>國立高雄應用科技大學<br>化學工程與材料工程系博碩士班<br>104<br>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.
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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.
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碩士<br>國立高雄應用科技大學<br>化學工程與材料工程系博碩士班<br>104<br>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.
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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.
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碩士<br>國立高雄應用科技大學<br>化學工程與材料工程系博碩士班<br>103<br>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.
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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.
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碩士<br>東吳大學<br>化學系<br>105<br>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
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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.
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碩士<br>逢甲大學<br>化學工程學系<br>106<br>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.
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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.
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碩士<br>國立成功大學<br>環境工程學系<br>107<br>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.
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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.
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Cheng, 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.
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碩士<br>國立臺中教育大學<br>科學應用與推廣學系科學教育碩士班<br>99<br>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.
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Chang, Yu-Hsueh, and 張鈺雪. "Stabilization of Bi2O3 High Temperature Phase." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/36340447212717411983.
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碩士<br>國立臺灣海洋大學<br>材料工程研究所<br>103<br>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.