Mechanism of pore generation in calcium hexaluminate (CA6) ceramics formed in situ from calcined alumina and calcium carbonate aggregates
| Autor: | Ivone Regina de Oliveira, Rafael Salomão, Veridiana Lopes Ferreira, Adriane D.V. Souza, Wagner Rafael Correr |
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| Rok vydání: | 2016 |
| Předmět: |
Materials science
Sintering chemistry.chemical_element Mineralogy 02 engineering and technology Calcium 01 natural sciences law.invention chemistry.chemical_compound law 0103 physical sciences Materials Chemistry MATERIAIS POROSOS SINTERIZAÇÃO Calcination Crystallization Porosity Eutectic system 010302 applied physics 021001 nanoscience & nanotechnology Microstructure Calcium carbonate chemistry Chemical engineering Ceramics and Composites 0210 nano-technology |
| Zdroj: | Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual) Universidade de São Paulo (USP) instacron:USP |
| ISSN: | 0955-2219 |
| DOI: | 10.1016/j.jeurceramsoc.2016.05.026 |
| Popis: | Porous structures of calcium hexaluminate (CaAl 12 O 19 or CA 6 ) are resistant to densification, chemical attack and thermal shock and have been widely employed in thermal insulators for high temperatures (above 1400 °C). Despite its technological importance, little is known corcerning the in situ formation of CA 6 from the early calcination temperatures (500–900 °C) up to full sintering (above 1000 °C). This study investigated the mechanisms of pores generation in in situ CA 6 obtained from a mixture of calcined alumina (α-Al 2 O 3 ) and chemically precipitated calcium carbonate (CaCO 3 ) aggregates. The evolution of the microstructure was followed by scanning electron microscopy, X-ray diffraction, dilatometric analysis, and measurements of physical properties, in the 500–1500 °C temperature range. Samples of 50-40% total porosity and different degrees of linear expansion were obtained after sintering at 1100–1500 °C, respectively. The crystallization of liquid phases of eutectic composition played a major role in the formation and maintenance of pores after CaCO 3 decomposition. |
| Databáze: | OpenAIRE |
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