Flexible design of cellular Al2TiO5 and Al2TiO5-Al2O3 composite monoliths by reactive firing

Publication date: 5 October 2017
Source:Materials & Design, Volume 131
Author(s): Eleonora Lalli, Nuno M.D. Vitorino, Carla A.M. Portugal, João G. Crespo, Cristiana Boi, Jorge R. Frade, Andrei V. Kovalevsky
Cellular Al2TiO5 and Al2TiO5 – Al2O3 composite ceramics were obtained by emulsification of liquid paraffin in aqueous suspensions of mixed TiO2+Al2O3 powders, with subsequent burnout of the organic phase and 2-step reactive firing at high temperatures. The reactants ratio and paraffin to suspension volume ratio were used as primary parameters to control the phase composition and relevant microstructural features, while firing conditions were also adjusted for greater flexibility in designing Al2TiO5-based cellular materials. Taguchi experimental planning was used to assess the relevant impacts of 2-step firing parameters on phase composition and porosity, characterized by detailed XRD/SEM/EDS studies. The results emphasized the positive effects of Al2O3 excess in Al2TiO5 – Al2O3 composite ceramics on stabilization of the Al2TiO5 phase and also for flexible design of cellular materials with controlled porosity and phase distributions. Analysis of correlation matrixes identified the 2-step firing parameters with greatest impact on the porosity and phase composition, and these trends were confirmed by multivariate linear regression. The observed trends indicated significant differences in reactivity and densification mechanisms between compositions with nominal Al2TiO5 stoichiometry and composite materials. These differences were most obvious for samples with significant residual fractions of unreacted titania.

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