Effect of sol-gel mixing on mullite microstructure and phase equilibria in the. cap alpha. -Al/sub 2/O/sub 3/-SiO/sub 2/ system

Journal Article · Thu Oct 01 04:00:00 EDT 1987 · J. Am. Ceram. Soc.; (United States)

DOI:https://doi.org/10.1111/j.1151-2916.1987.tb04867.x· OSTI ID:5046610

Pask, J A; Zhang, X W; Tomsia, A P; Yoldas, B E

Starting powders containing 72 wt% Al/sub 2/O/sub 3/ and 28 wt% SiO/sub 2/ were prepared by sol-gel methods classified as colloidal and polymeric. Compacts fired at 1700/sup 0/C showed significant differences in microstructure. The specimens formed with the colloidal powder had mullite grains of prismatic shape and liquid phase; with polymeric powder, mullite grains were granular with no liquid phase present. It is shown that the mullite grains in the first case are higher in Al/sub 2/O/sub 3/ content, resulting in an excess of SiO/sub 2/ which is the base for the liquid phase. In the second case, the mullite grains have the same Al/sub 2/O/sub 3/ content as the starting powders. The presence of a liquid phase in the first case is considered to be metastable, resulting from the nature of the starting materials and processing conditions employed.

• Research Organization: Dept. of Materials Science and Mineral Engineering, Univ. of California, Berkeley, CA (US)
• OSTI ID: 5046610
• Journal Information: J. Am. Ceram. Soc.; (United States), Journal Name: J. Am. Ceram. Soc.; (United States) Vol. 70:10; ISSN JACTA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COLLOIDS
CRYSTAL STRUCTURE
DISPERSIONS
FLUIDS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
LIQUIDS
MATERIALS
MICROSTRUCTURE
MINERALS
MULLITE
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
POLYMERIZATION
POWDERS
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SOL-GEL PROCESS
VERY HIGH TEMPERATURE