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Doctoral Thesis
DOI
10.11606/T.88.2002.tde-18082015-165454
Document
Author
Full name
Érika Regina Manoel Andreeta
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2002
Supervisor
Committee
Hernandes, Antonio Carlos (President)
Baldochi, Sonia Licia
Carvalho, Jesiel Freitas
Li, Maximo Siu
Rodrigues, José de Anchieta
Title in Portuguese
Solidificação direcional de compostos eutéticos de óxidos refratários usando o método de fusão a laser
Keywords in Portuguese
Compositos
Eutético
Fibras
Fusão a laser
Oxidos
Abstract in Portuguese
Compósitos eutéticos de óxidos de Al2O3⁄GdAlO3 livres de poros foram produzidos na forma de fibras empregando-se a técnica de fusão a laser denominada laser heated pedestal growth LHPG. A microestrutura analisada ao microscópio eletrônico de varredura MEV foi denominado como do tipo irregular escrita chinesa, com a presença de padrões fibrosos em amostras com taxa de puxamento superior a 24mm⁄h. A despeito da sua complexidade, a microestrutura desse compósito foi controlada e a relação entre o espaçamento médio entre as fases e a taxa de puxamento λv = constante = (40 ± 1)µm3⁄s foi mantida em todo o intervalo de taxas de puxamento utilizado. Resultados de espectroscopia microRaman possibilitam indexar as fases presentes e revelaram uma maior continuidade da fase GdAlO3 fibrosa, em comparação à escrita chinesa. Ensaios de flexão a três pontos resultaram em valores de módulo de ruptura no intervalo de 490MPa a 1320MPa, superiores aos da alumina policristalina. Também foram puxadas com sucesso através da técnica LHPG, fibras oxidas eutéticas de ZrO2⁄MgO, ZrO2⁄CaZrO3 e Eu2O3⁄EuAlO3, utilizando-se diferentes velocidades de puxamento. Essas fibras apresentaram descontinuidades no padrão eutético, em marcas com o formato da interface sólido-líquido, que puderam ser diminuídas, à exceção do Eu2O3⁄EuAlO3, com o aumento da taxa de puxamento das amostras e no caso do ZrO2⁄MgO, essas marcas foram diminuídas também com a mudança da composição
Title in English
Not available
Keywords in English
Not available
Abstract in English
Pore-free eutectic oxides fibers of Al2O3⁄GdAlO3 were produced using the laser heated pedestal growth technique - LHPG. The microstructure analyzed in the scanning electronic microscope (SEM) was determined as the "Chinese script" irregular type, with the presence of fibrous pattern samples with pulling rates above 24mm⁄h. In spite of its complexity, the microstructure of this eutectic was controlled and the relation between the phase spacing and the pulling rate λv = constant = (40 ± 1)µm3⁄s was maintained over the entire used pulling rate range. MicroRaman spectroscopy results allowed the phase indexation and revealed a larger continuity of the GdAI03 fibrous phase, compared to the "Chinese script" type. Three point bending tests result in modulus of rupture (MOR) in the range of 490MPa to 1320MPa, superior to the polycrystalline alumina. The eutectic oxide fibers of ZrO2⁄MgO, ZrO2⁄CaZrO3 and Eu2O3⁄EuAlO3 were successful pulled using the LHPG technique, for different pulling rates and their microstructures were observed. These fibers presented discontinuities on the eutectic pattern which turned out to be marks with the solid-liquid interface shape. The frequency of these marks could be decreased with the increase of the pulling rate, except for the Eu2O3⁄EuAlO3 fibers. In the case of the ZrO2⁄MgO, the continuity of the eutectic pattern was also increased with a change in the pedestal composition
 
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Publishing Date
2015-08-19
 
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