Characterization of porous calcium hexaluminate ceramics produced from calcined alumina and microspheres of Vaterite (mu-CaCO3)

Author(s)

Costa, Ligia M. M. ^[1] ; Sakihama, Jose ^[1] ; Salomao, R. ^[1]

Affiliation

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

• Document type: Journal article
• Source: Journal of the European Ceramic Society; v. 38, n. 15, p. 5208-5218, DEC 2018.
• Web of Science Citations: 2

Abstract

The evolution in the microstructure of porous calcium hexaluminate (CaAl12O19 or CA(6)) formed in situ is significantly affected by the characteristics of precursor raw materials. In this study, microspheres of Vaterite (mu-CaCO3) of different average sizes (5, 7 and 15 mu m) were mixed with fine alpha-Al2O3 and sintered. During heating (590-753 degrees C), the Vaterite particles collapsed and produced spherical pores surrounded by regions of high CaO concentration. Different quantities of low-density-and-melting-point calcium aluminates (C(12)A(7), CA and CA(2)) were formed above 1100 degrees C. Small portions of a liquid phase were observed for samples containing thin Vaterite particles, which resulted in a denser structure comprised of CA(6). The samples prepared with coarse Vaterite significantly expanded and the asymmetric shape of the CA(6) crystals prevented densification and generated highly porous structures. Therefore, the tailoring of Vaterite particles' characteristics enables the design of physical properties of CA(6) porous structures according to the application aimed. (AU)

• FAPESP's process: 10/19274-5 - Novel methodology for hydrotalcite (Mg6Al2(OH)16CO3.4H2O) synthesis from aqueous suspensions of magnesium oxide (MgO) and aluminum hydroxide (Al(OH)3) and its application in porous ceramics for high temperature thermal insulation
• Grantee: Rafael Salomão
• Support Opportunities: Research Grants - Young Investigators Grants