Effect of thermal treatment on the structural evolution of 3:2 and 2:1 mullite monophasic gels

Single phase mullite gels with composition 3Al 2O 3 · 2SiO 2 (3:2) and 2Al 2O 3 · SiO 2 (2:1) were prepared by the semialkoxide method using aluminum nitrate nonahydrate and tetraethylorthosilicate as reagents. The influence of the thermal processing conditions on the reaction sequence was investiga...

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Bibliographic Details
Published in:Journal of non-crystalline solids 2005-05, Vol.351 (14), p.1202-1209
Main Authors: Ruiz de Sola, Esther, Estevan, Francisco, Torres, Francisco Jose, Alarcón, Javier
Format: Article
Language:English
Subjects:
Exact sciences and technology
Physics
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Summary:Single phase mullite gels with composition 3Al 2O 3 · 2SiO 2 (3:2) and 2Al 2O 3 · SiO 2 (2:1) were prepared by the semialkoxide method using aluminum nitrate nonahydrate and tetraethylorthosilicate as reagents. The influence of the thermal processing conditions on the reaction sequence was investigated. Both 3:2 and 2:1 mullite gels formed orthorhombic mullite under fast heating (40 °C/min) at 900 °C. Slow heatings delayed the formation of mullite in both gel compositions but no formation of spinel was detected between 1000 °C and 1100 °C. The slow transformation of pentacoordinated aluminum to octahedral and tetrahedral arrangements probably depends on the larger size and extent of the alumina-rich inhomogeneities in gels slowly heated.
ISSN:0022-3093
1873-4812
DOI:10.1016/j.jnoncrysol.2005.02.017