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Thermal Behavior of Alumina—Silica Xerogels During Calcination
Author(s) -
Hsi ChiShiung,
Lu HongYang,
Yen FuSu
Publication year - 1989
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1989.tb06063.x
Subject(s) - mullite , calcination , spinel , materials science , kaolinite , chemical engineering , aluminium silicate , phase (matter) , amorphous solid , aluminosilicate , mineralogy , chemistry , catalysis , metallurgy , crystallography , ceramic , organic chemistry , engineering
Xerogels of 3Al 2 O 3 ·2SiO 2 mullite were prepared by hydrolyzing Al(NO 3 ) 3 ·9H 2 O and Si(OC 2 H 5 ) 4 solutions with pH values of 8.3, 9.4, 10.1, and 10.4; the xerogels were composed of a combination of singlephase and diphasic materials. A strong alkaline solution enhanced bayerite formation in the gels. Mullite from the diphasic xerogels was produced by reacting θ‐Al 2 O 3 with amorphous SiO 2 , whereas mullite from the single‐phase xerogels was transformed from Al‐Si spinel. For the single‐phase xerogel, the DTA curve closely resembled the kaolinite‐to‐ mullite reaction. For the diphasic xerogels, the Al 3+ ‐containing solution gelled to pseudoboehmite, which transformed to bayerite in solution. The bayerite then decomposed to η‐Al 2 O 3 and to θ‐Al 2 O 3 sequentially on heating.