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Formation of Silicon‐Aluminum Spinel
Author(s) -
CHAKRABORTY AKSHOY KUMAR
Publication year - 1979
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.1151-2916.1979.tb19034.x
Subject(s) - mullite , spinel , crystallization , materials science , amorphous solid , phase (matter) , silicon , aluminium , chemical engineering , alkali metal , mineralogy , crystallography , analytical chemistry (journal) , chemistry , metallurgy , chromatography , ceramic , organic chemistry , engineering
Characterization of the intermediate cubic phase formed during the transformation of coprecipitated SiO 2 ‐Al 2 O 3 gel on heating was studied and X‐ray diffraction methods are reviewed and criticized. Coprecipitated gels of different SiO 2 /Al 2 O 3 ratios were prepared; all showed a 980°C exotherm followed by crystallization of the cubic phase and liberation of SiO 2 . Alkali extraction of SiO 2 showed two types present in the 980°‐heated product. One variety is free amorphous SiO 2 and the other, chemically bonded to alumina in the crystalline cubic phase, was isolated and characterized as Si‐Al spinel with the same composition as mullite. Thus, its formation from the gel of mullite composition shows the highest exotherm and the measured density agrees approximately with the theoretically calculated value.