Calcium aluminate cement in castable alumina: from hydrate bonding to the in situ formation of calcium hexaluminate
| Autor: | Mirian A. Kawamura, José Sakihama, Ana M. Segadães, Ana B.V. Emilio, Rafael Salomão |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Materials science
Porous ceramics Aluminate Alumina chemistry.chemical_element Sintering 02 engineering and technology Calcium 01 natural sciences Calcium hexaluminate law.invention chemistry.chemical_compound law Calcium aluminate cement 0103 physical sciences Materials Chemistry Calcination Porosity 010302 applied physics Cement Process Chemistry and Technology 021001 nanoscience & nanotechnology Microstructure Surfaces Coatings and Films Electronic Optical and Magnetic Materials chemistry Chemical engineering Ceramics and Composites 0210 nano-technology Hydrate |
| Popis: | Calcium hexaluminate (CA6) is an intrinsically densification-resistant material, therefore, its porous structures are key materials for applications as high-temperature thermal insulators. This article reports on the combination of calcined alumina and calcium aluminate cement (CAC) in castable aqueous suspensions for the in situ production of porous CA6. The CAC content (10–34 vol%) and the curing conditions ensure structural integrity prior to sintering and maximize the development of hydrated phases. Changes in physical properties, crystalline phases, and microstructure were investigated after isothermal treatments (120–1500 °C), and three sequential porogenic events were observed. The hydration of CAC preserved the water-derived pores (up to 120 °C), and the dehydroxylation of CAC hydrates (250–700 °C) generated inter-particles pores. Moreover, the in situ expansive formation of CA2 and CA6 (900–1500 °C) hindered densification and generated intra-particle pores. Such events differed from those observed with other CaO sources, and resulted in significantly higher pores content and lower thermal conductivity. |
| Databáze: | OpenAIRE |
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