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The Influence of Random Defect Density on the Thermal Stability of Kaolinites
Author(s) -
He Hongping,
Yuan Peng,
Guo Jiugao,
Zhu Jianxi,
Hu Cheng
Publication year - 2005
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.1551-2916.2005.00194.x
Subject(s) - mullite , kaolinite , orthorhombic crystal system , materials science , microstructure , thermal stability , mineralogy , composite material , chemical engineering , crystallography , metallurgy , chemistry , crystal structure , ceramic , engineering
The thermal stability of kaolinite and the microstructure of its thermal products strongly depend on random defects ( R 2 ) rather than crystalline defects (HI). Kaolinite with a lower random defect density is more stable than that with higher defect density during dehydroxylation and the derived metakaolinite can be directly transformed into orthorhombic mullite (3/2‐mullite). However, for kaolinite with higher random defect density, there is a cubic phase occurring in the transformation from metakaolinite to primary mullite. Primary mullite will be transformed into orthorhombic mullite as temperature increases. Al V is universally present in the metakaolinite and the relative amounts of Al VI , Al V , and Al IV vary with the random defect density of the parent kaolinite.