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Formation of Mullite from Sol‐Gel Mixtures and Kaolinite
Author(s) -
Pask Joseph A.,
Tomsia Antoni P.
Publication year - 1991
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.1151-2916.1991.tb06770.x
Subject(s) - mullite , kaolinite , crystallinity , homogeneity (statistics) , materials science , orthorhombic crystal system , tetragonal crystal system , nucleation , mineralogy , aluminium silicate , chemical engineering , cristobalite , impurity , bauxite , inorganic chemistry , chemistry , crystallography , quartz , metallurgy , ceramic , crystal structure , composite material , organic chemistry , statistics , mathematics , engineering
Critical analyses of published reaction studies on kaolinite, and sol‐gel and powder mixtures equivalent to 3Al 2 O 3 ·2SiO 2 mullite, were made. Supplementary experiments on reactions of kaolinite at different rates of heating were analyzed. Complete atomic homogeneity of precursors results in formation of tetragonal mullite. Colloidal precursors initially form spinel which reacts with the remaining silica by a diffusion‐nucleation mechanism to form orthorhombic mullite. Precursors with intermediate atomic homogeneity follow both reaction paths. Kaolinite with a layer lattice structure has two‐dimensional atomic homogeneity. Both reaction routes are followed and their degree of interaction is dependent on the crystallinity and impurities of the kaolinite.