Anomalously Low Surface Area and Density in the Silica-Alumina Gel System

A range of composition/processing conditions that yield xerogel surface areas 2 orders of magnitude lower than expected along with low skeletal densities has been discovered. For xerogel compositions in the vicinity of 50 wt% Al2O3, surface areas are 1 to 5 m2/g and skeletal densities are 2.1 to 2.2...

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Veröffentlicht in:	Journal of the American Ceramic Society 1989-12, Vol.72 (12), p.2354-2358
Hauptverfasser:	Hietala, Susan L., Smith, Douglas M., Golden, Johnny L., Brinker, C. Jeffrey
Format:	Artikel
Sprache:	eng
Schlagworte:	360201 - Ceramics, Cermets, & Refractories- Preparation & Fabrication 360202 - Ceramics, Cermets, & Refractories- Structure & Phase Studies alumina ALUMINIUM COMPOUNDS ALUMINIUM OXIDES CHALCOGENIDES CHEMICAL COMPOSITION Chemistry Colloidal state and disperse state COLLOIDS DENSITY DISPERSIONS Emulsions. Microemulsions. Foams Exact sciences and technology GELS General and physical chemistry HEAT TREATMENTS MATERIALS SCIENCE OXIDES OXYGEN COMPOUNDS PHYSICAL PROPERTIES processing silica SILICON COMPOUNDS SILICON OXIDES surface area
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Zusammenfassung:	A range of composition/processing conditions that yield xerogel surface areas 2 orders of magnitude lower than expected along with low skeletal densities has been discovered. For xerogel compositions in the vicinity of 50 wt% Al2O3, surface areas are 1 to 5 m2/g and skeletal densities are 2.1 to 2.2 g/cm3, as compared to the expected values of ∼300 m2/g and ∼2.6 g / cm3, respectively. This behavior is observed over a wide range of heat treatment temperatures (373 to 1073 K) and appears to be the result of closed porosity which evolves during gel drying.
ISSN:	0002-7820 1551-2916
DOI:	10.1111/j.1151-2916.1989.tb06088.x