Characterization of Microporous Ceramics Based on Calcium Hexaluminate “In Situ” Produced by Direct Molding

Author(s)

V. M. C. Leite ^[1] ; R. Salomão ^[2] ; G. L. B. Cardoso ^[3] ; F. S. Ortega ^[4] ; I. R. Oliveira ^[5]

Affiliation

^[1] Universidade do Vale do Paraíba. Instituto de Pesquisa e Desenvolvimento - Brasil

^[2] Universidade de São Paulo. Escola de Engenharia de São Carlos - Brasil

^[3] Universidade do Vale do Paraíba. Instituto de Pesquisa e Desenvolvimento - Brasil

^[4] Universidade do Vale do Paraíba. Instituto de Pesquisa e Desenvolvimento - Brasil

^[5] Universidade do Vale do Paraíba. Instituto de Pesquisa e Desenvolvimento - Brasil

• Document type: Journal article
• Source: MATERIALS RESEARCH-IBERO-AMERICAN JOURNAL OF MATERIALS; v. 27, 2024-11-11.

Abstract

Calcium hexaluminate (CA6) presents a wide application in high-temperature thermal insulation. Despite the high porosity levels achieved, the use of carbonated precursors in its synthesis inevitably produces CO2 as a by-product. CA6 was produced by combining different sources of alumina (α-Al2O3 and ρ-Al2O3) and lime (CaCO3, Ca(OH)2, and CaO) in aqueous suspensions that were cast and sintered to evaluate these routes on its physical properties. The products attained after sintering at 1550 and 1600 °C were characterized for crystal phases, real density, particle morphology, uniaxial compressive strength, apparent porosity, and pore size distribution. Part of the samples sintered at 1600 °C was subjected to a thermal shock test and was then evaluated for residual strength under diametrical compression, apparent porosity, pore size distribution, and flexural elastic modulus. The CA6 samples produced from α-Al2O3 presented lower pore fraction and higher mechanical strength and modulus of elasticity. The superior properties of the materials produced with α-alumina were maintained after thermal shock. The acicular geometry of the CA6 particles is related to their excellent thermal shock resistance and mechanical performance. The results indicated a more environmentally friendly system produced from α-Al2O3-CaO for industrial applications of high-temperature thermal insulation resistant to thermal shock damage. (AU)

• FAPESP's process: 15/01541-0 - Characterization of insulating ceramic material based on calcium hexaluminate
• Grantee: Vitoria Marques Cesar Leite
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• 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