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Master's Dissertation
DOI
10.11606/D.88.1997.tde-25112014-160127
Document
Author
Full name
Eiji Harima
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1997
Supervisor
Committee
Souza, Milton Ferreira de (President)
Hernandes, Antonio Carlos
Rodrigues, José de Anchieta
Title in Portuguese
Estabilização da fase β e obtenção da fase α da cristobalita a partir do resíduo da casca de arroz queimada
Keywords in Portuguese
Cristobalita
Estabilização
Abstract in Portuguese
A sílica obtida da queima de casca de arroz foi convertida nas fases α e β. A estabilização da fase β foi obtida pela introdução de alumínio e cálcio na rede de sílica, 10001100 °C, na proporção CaO:2Al2O3:38SiO2. Foi observado que a transição de fase α→β da cristobalita α tem sua temperatura de transição reduzida de 175°C bem como sua entalpia de transição, de 16,0 J/g para 7,0 J/g. Esse efeito é causado pela introdução de íon K+, presente na casca de arroz, na estrutura da sílica. O processamento empregado nessa conversão usa equipamentos normalmente encontrados em empresas de cerâmica tradicional moinho, atomizador, prensa e forno
Title in English
Cristobalite formed from rice shell burning: α, formation and β-fase stabilization
Keywords in English
Cristobalite
Silica
Stabilization
Abstract in English
Silica generated from burned rice shells has been converted to the β and α phases of cristobalite. The β phase stabilization was acomplished by instilling aluminum and calcium into the silica structure, at 1000-1100 °C, in the following proportion CaO:2Al2O3:38SiO2. The phase transition α→β of the α-cristobalite has a lower transition temperature, as compared with cristobalite made from pure silica, from 270°C to 170°C. Also the transition entalphy was reduced from 16,0 J/g to 7,0 J/g. These changes were attributed to the K+ ion present in the silica structure of the burned silica. The process used in this convertion makes use of standard equipments, regularly used in ceramic producing companies mill, spray dryer, furnaces, and press.
 
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Publishing Date
2014-11-26
 
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