Calcium aluminate cement in castable alumina: From hydrate bonding to the in situ formation of calcium hexaluminate

Autor(es)

Salomao, Rafael ^[1] ; Kawamura, Mirian A. ^[1] ; Emilio, V, Ana B. ; Sakihama, Jose ^{[2, 3]} ; Segadaes, Ana M. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Sao Carlos Sch Engn, Mat Engn Dept, Ave Trabalhador Sao Carlense 400, Sao Carlos - Brazil

^[2] Emilio, Ana B., V, Univ Sao Paulo, Sao Carlos Sch Engn, Mat Engn Dept, Ave Trabalhador Sao Carlense 400, Sao Carlos - Brazil

^[3] Pontificia Univ Catolica Peru, Mech Engn Dept, Ave Univ 1801, Lima - Peru

^[4] Univ Aveiro, Dept Mat & Ceram Engn CICECO, Aveiro - Portugal

• Tipo de documento: Artigo Científico
• Fonte: CERAMICS INTERNATIONAL; v. 47, n. 11, p. 15082-15093, JUN 1 2021.
• Citações Web of Science: 1

Resumo

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. (AU)

• Processo FAPESP: 18/19773-3 - Refratários microporosos moldáveis no sistema Al2O3-MgO-CaO para isolamento térmico acima de 1200ºC
• Beneficiário: Rafael Salomão
• Modalidade de apoio: Bolsas no Exterior - Pesquisa