Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)

Detalhes bibliográficos
Ano de defesa: 2008
Autor(a) principal: Colombo, Luciléia Aparecida
Orientador(a): Noronha, Eduardo Garuti lattes
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Universidade Federal de São Carlos
Programa de Pós-Graduação: Programa de Pós-Graduação em Ciência Política - PPGPol
Departamento: Não Informado pela instituição
País: BR
Palavras-chave em Português:
Área do conhecimento CNPq:
Link de acesso: https://repositorio.ufscar.br/handle/ufscar/968
Resumo: Nowadays, the flux method is one of the most widely used techniques promote growth of YBa2Cu3O7-ä single crystal superconductor. By using the material in a melted state, the reactions due to temperature are possible. To prepare single crystal superconductors of the family Y-Ba-Cu-O, a long period of time is necessary to melt the material in adequate conditions. In order to do this a satisfactory performance of the crucible is required; it must be resistant to any kind of chemical attack. In this work some materials used were investigated in crucibles. Platinum, gold (noble metals), oxides like Al2O3, ZrO2 showed problems when used in processing Y123 superconductors. To avoid this problem the zirconiaytria system is largely applied. Some authors have investigated the SnO2 crucible, but they found problems related to the densification of the SnO2. Recently, it was discovered that SnO2 can be densified without liquid phase, showing 99,7% of the theoretical density when sinterized up to 1300°C. Then, this condition was used to produce crucibles by slip casting to form the YBa2Cu3O7-ä single crystal superconductors without contamination. It was observed, in a first instance, that SnO2 crucibles are resistant to chemical attack of the flux that is rich in barium and copper. During the process it was observed an interface wall between the vial and the flux formed by BaSnO3. This protection is formed after heat treatment at 1025°C during 4, 17 and 24 hours. By increasing the treatment time (up to 24 hours), it was observed that the wall thickness increased too and it was possible stablish a relation between treatment time/thickness wall (that defines the resistance of chemical attack). This enabled the determination of the SnO2 crucible resistance to corrosion, under the flux condition. The second part of this work involved the Y123 single crystal growth. After produced, they were analysed by x-ray diffraction and SEM with microanalysis in cross sections of the crucibles to observe the BaSnO3 interface. It was observed that single crystals were not contaminated by tin, and they were analyzed through measuring magnetization vs. Temperature. The single crystal showed a critical temperature (Tc) around 90,5K with a transition width (Tc) around 19,5K before treatment with an oxygen flux at 450°C. After seven days of a second treatment under the same conditions, the Tc was increased to 92K with a decreasing to 4,5K in Tc. The results showed that SnO2 vials are resistant to BaO-CuO flux and appropriate to single crystal growth in YBa2Cu3O7-ä superconductors without external.
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spelling Colombo, Luciléia AparecidaNoronha, Eduardo Garutihttp://lattes.cnpq.br/6908348693613769http://lattes.cnpq.br/942154975535884109bd02c2-28a7-42d1-8ec1-66e2e47d5b6d2016-06-02T19:14:52Z2008-08-212016-06-02T19:14:52Z2008-02-20COLOMBO, Luciléia Aparecida. Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002). 2008. 236 f. Dissertação (Mestrado em Ciências Humanas) - Universidade Federal de São Carlos, São Carlos, 2008.https://repositorio.ufscar.br/handle/ufscar/968Nowadays, the flux method is one of the most widely used techniques promote growth of YBa2Cu3O7-ä single crystal superconductor. By using the material in a melted state, the reactions due to temperature are possible. To prepare single crystal superconductors of the family Y-Ba-Cu-O, a long period of time is necessary to melt the material in adequate conditions. In order to do this a satisfactory performance of the crucible is required; it must be resistant to any kind of chemical attack. In this work some materials used were investigated in crucibles. Platinum, gold (noble metals), oxides like Al2O3, ZrO2 showed problems when used in processing Y123 superconductors. To avoid this problem the zirconiaytria system is largely applied. Some authors have investigated the SnO2 crucible, but they found problems related to the densification of the SnO2. Recently, it was discovered that SnO2 can be densified without liquid phase, showing 99,7% of the theoretical density when sinterized up to 1300°C. Then, this condition was used to produce crucibles by slip casting to form the YBa2Cu3O7-ä single crystal superconductors without contamination. It was observed, in a first instance, that SnO2 crucibles are resistant to chemical attack of the flux that is rich in barium and copper. During the process it was observed an interface wall between the vial and the flux formed by BaSnO3. This protection is formed after heat treatment at 1025°C during 4, 17 and 24 hours. By increasing the treatment time (up to 24 hours), it was observed that the wall thickness increased too and it was possible stablish a relation between treatment time/thickness wall (that defines the resistance of chemical attack). This enabled the determination of the SnO2 crucible resistance to corrosion, under the flux condition. The second part of this work involved the Y123 single crystal growth. After produced, they were analysed by x-ray diffraction and SEM with microanalysis in cross sections of the crucibles to observe the BaSnO3 interface. It was observed that single crystals were not contaminated by tin, and they were analyzed through measuring magnetization vs. Temperature. The single crystal showed a critical temperature (Tc) around 90,5K with a transition width (Tc) around 19,5K before treatment with an oxygen flux at 450°C. After seven days of a second treatment under the same conditions, the Tc was increased to 92K with a decreasing to 4,5K in Tc. The results showed that SnO2 vials are resistant to BaO-CuO flux and appropriate to single crystal growth in YBa2Cu3O7-ä superconductors without external.O método do fluxo tem se tornado uma das técnicas mais usadas, quando se trata de crescimento de monocristais supercondutores de YBa2Cu3O7-ä. A técnica processa o material no estado fundido e isto acarreta temperaturas nas quais reações podem acontecer. Na preparação de monocristais supercondutores da família Y-Ba-Cu-O, mais especificamente, YBa2Cu3O7-ä, é preciso de tempos prolongados para fundir o material nas temperaturas de crescimento, em algum recipiente (cadinho) que os tenha. Este cadinho deve ser resistente, ao ponto de conter o fundido (fluxo) a altas temperaturas e resistir a possíveis ataques químicos do próprio fluxo com o cadinho. Porém qual material suportaria a agressividade de um fluxo rico em BaO-CuO. Somente poderia ser um cadinho inerte ou pouco reativo às condições do fluxo em questão. São utilizados vários tipos de cadinhos para o crescimento dos monocristais de YBa2Cu3O7-ä (Y123, como também é conhecido este material). Alguns metais nobres, como a platina e o ouro; óxidos, como a alumina, o óxido de zircônio e outros, são atacados, corroídos, quando utilizados no processamento de materiais supercondutores. Trabalhos mais recentes demonstraram que cadinhos de zircônia-ítria são resistentes ao ataque do fluxo. Poucos autores utilizaram cadinhos de óxido de estanho para o crescimento de supercondutores de Y123, porém este tipo de cadinhos apresentaram problemas de densificação. Recentemente observou-se que o óxido de estanho (SnO2) pode densificar sem a formação de fase líquida (ponto suscetível ao ataque do fluxo rico em BaO-CuO). Esse material, o SnO2, densificou acima de 99,7% da densidade teórica quando sinterizado acima de 1300ºC. Foi, efetivamente, o escolhido para a fabricação de cadinhos por colagem de barbotina e para produzir monocristais supercondutores de YBa2Cu3O7-ä com baixa ou nenhuma contaminação do fluxo e dos monocristais. vi Numa primeira etapa do trabalho, demonstrou-se que o cadinho de SnO2 resiste à corrosão do fluxo com excesso de bário e cobre. Houve a formação de uma interface entre a parede do cadinho e o fluxo, identificada como "camada protetora" de estanato de bário (BaSnO3), após tratamento térmico a 1025ºC por 4, 17 e 24 horas. Acredita-se que esta fase formou-se pela reação entre o BaO e o SnO2. A espessura dessa camada aumentou com o incremento do tempo do tratamento (até 24 horas). Isto permitiu definir a resistência à corrosão do cadinho de SnO2, perante as condições agressivas do próprio fluxo. Procedeu-se, então, ao crescimento dos monocristais de Y123, segunda etapa desta dissertação. A preparação dos monocristais foi descrita, técnicas de análises por difração de raios-X (DRX) e microscopia eletrônica de varredura (MEV) com microanálises foram feitas em seções transversais dos cadinhos, para melhor detalhar o ocorrido com a interface de BaSnO3, formada entre o cadinho e o fluxo. Pôde-se avaliar a não contaminação dos monocristais pelo estanho e analisá-los a partir de medidas de magnetização vs. temperatura. O monocristal apresentou uma temperatura crítica (Tc) em torno de 90,5K com uma largura de transição (Tc) de, aproximadamente, 19,5K, antes de ser tratado com fluxo de oxigênio a 450ºC. Após 7 dias no tratamento, a Tc sofreu um aumento para 92K com um decréscimo da Tc para 4,5K. Os resultados demonstraram que os cadinhos de SnO2 são resistentes à corrosão do fluxo rico em BaO-CuO e apropriados para o crescimento de monocristais supercondutores de YBa2Cu3O7-ä sem impurezas advindas do próprio cadinho.Universidade Federal de Minas Geraisapplication/pdfporUniversidade Federal de São CarlosPrograma de Pós-Graduação em Ciência Política - PPGPolUFSCarBRSupercondutoresMonocristalSnO2CorrosãoYBa2Cu3O7-8CrescimentoCIENCIAS HUMANAS::CIENCIA POLITICAFederalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/masterThesis-1-152b30830-0c44-4bd7-bf35-8d84e96c0baainfo:eu-repo/semantics/openAccessreponame:Repositório Institucional da UFSCARinstname:Universidade Federal de São Carlos (UFSCAR)instacron:UFSCARORIGINAL1937.pdfapplication/pdf1710021https://repositorio.ufscar.br/bitstream/ufscar/968/1/1937.pdf22c07dce6c6624be220556f18c1f0150MD51THUMBNAIL1937.pdf.jpg1937.pdf.jpgIM Thumbnailimage/jpeg6023https://repositorio.ufscar.br/bitstream/ufscar/968/2/1937.pdf.jpgea7a32b6e9f7ce56e7415bc5367152b4MD52ufscar/9682023-09-18 18:31:39.026oai:repositorio.ufscar.br:ufscar/968Repositório InstitucionalPUBhttps://repositorio.ufscar.br/oai/requestopendoar:43222023-09-18T18:31:39Repositório Institucional da UFSCAR - Universidade Federal de São Carlos (UFSCAR)false
dc.title.por.fl_str_mv Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
title Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
spellingShingle Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
Colombo, Luciléia Aparecida
Supercondutores
Monocristal
SnO2
Corrosão
YBa2Cu3O7-8
Crescimento
CIENCIAS HUMANAS::CIENCIA POLITICA
title_short Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
title_full Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
title_fullStr Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
title_full_unstemmed Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
title_sort Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002)
author Colombo, Luciléia Aparecida
author_facet Colombo, Luciléia Aparecida
author_role author
dc.contributor.authorlattes.por.fl_str_mv http://lattes.cnpq.br/9421549755358841
dc.contributor.author.fl_str_mv Colombo, Luciléia Aparecida
dc.contributor.advisor1.fl_str_mv Noronha, Eduardo Garuti
dc.contributor.advisor1Lattes.fl_str_mv http://lattes.cnpq.br/6908348693613769
dc.contributor.authorID.fl_str_mv 09bd02c2-28a7-42d1-8ec1-66e2e47d5b6d
contributor_str_mv Noronha, Eduardo Garuti
dc.subject.por.fl_str_mv Supercondutores
Monocristal
SnO2
Corrosão
YBa2Cu3O7-8
Crescimento
topic Supercondutores
Monocristal
SnO2
Corrosão
YBa2Cu3O7-8
Crescimento
CIENCIAS HUMANAS::CIENCIA POLITICA
dc.subject.cnpq.fl_str_mv CIENCIAS HUMANAS::CIENCIA POLITICA
description Nowadays, the flux method is one of the most widely used techniques promote growth of YBa2Cu3O7-ä single crystal superconductor. By using the material in a melted state, the reactions due to temperature are possible. To prepare single crystal superconductors of the family Y-Ba-Cu-O, a long period of time is necessary to melt the material in adequate conditions. In order to do this a satisfactory performance of the crucible is required; it must be resistant to any kind of chemical attack. In this work some materials used were investigated in crucibles. Platinum, gold (noble metals), oxides like Al2O3, ZrO2 showed problems when used in processing Y123 superconductors. To avoid this problem the zirconiaytria system is largely applied. Some authors have investigated the SnO2 crucible, but they found problems related to the densification of the SnO2. Recently, it was discovered that SnO2 can be densified without liquid phase, showing 99,7% of the theoretical density when sinterized up to 1300°C. Then, this condition was used to produce crucibles by slip casting to form the YBa2Cu3O7-ä single crystal superconductors without contamination. It was observed, in a first instance, that SnO2 crucibles are resistant to chemical attack of the flux that is rich in barium and copper. During the process it was observed an interface wall between the vial and the flux formed by BaSnO3. This protection is formed after heat treatment at 1025°C during 4, 17 and 24 hours. By increasing the treatment time (up to 24 hours), it was observed that the wall thickness increased too and it was possible stablish a relation between treatment time/thickness wall (that defines the resistance of chemical attack). This enabled the determination of the SnO2 crucible resistance to corrosion, under the flux condition. The second part of this work involved the Y123 single crystal growth. After produced, they were analysed by x-ray diffraction and SEM with microanalysis in cross sections of the crucibles to observe the BaSnO3 interface. It was observed that single crystals were not contaminated by tin, and they were analyzed through measuring magnetization vs. Temperature. The single crystal showed a critical temperature (Tc) around 90,5K with a transition width (Tc) around 19,5K before treatment with an oxygen flux at 450°C. After seven days of a second treatment under the same conditions, the Tc was increased to 92K with a decreasing to 4,5K in Tc. The results showed that SnO2 vials are resistant to BaO-CuO flux and appropriate to single crystal growth in YBa2Cu3O7-ä superconductors without external.
publishDate 2008
dc.date.available.fl_str_mv 2008-08-21
2016-06-02T19:14:52Z
dc.date.issued.fl_str_mv 2008-02-20
dc.date.accessioned.fl_str_mv 2016-06-02T19:14:52Z
dc.type.status.fl_str_mv info:eu-repo/semantics/publishedVersion
dc.type.driver.fl_str_mv info:eu-repo/semantics/masterThesis
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dc.identifier.citation.fl_str_mv COLOMBO, Luciléia Aparecida. Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002). 2008. 236 f. Dissertação (Mestrado em Ciências Humanas) - Universidade Federal de São Carlos, São Carlos, 2008.
dc.identifier.uri.fl_str_mv https://repositorio.ufscar.br/handle/ufscar/968
identifier_str_mv COLOMBO, Luciléia Aparecida. Federalismo e reforma tributária no governo de Fernando Henrique Cardoso (1994-2002). 2008. 236 f. Dissertação (Mestrado em Ciências Humanas) - Universidade Federal de São Carlos, São Carlos, 2008.
url https://repositorio.ufscar.br/handle/ufscar/968
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