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Mullite Crystallization from SiO 2 ‐Al 2 O 3 Melts
Author(s) -
RISBUD SUBHASH H.,
PASK JOSEPH A.
Publication year - 1978
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.1151-2916.1978.tb09232.x
Subject(s) - mullite , crystallization , materials science , molybdenum , mineralogy , spinodal decomposition , analytical chemistry (journal) , metallurgy , chemistry , phase (matter) , chromatography , ceramic , organic chemistry
SiO 2 ‐Al 2 O 3 melts containing 42 and 60 wt% A1 2 O 3 were homogenized at 2090°C (∼10°) and crystallized by various heat treatment schedules in sealed molybdenum crucibles. Mullite containing ∼78 wt% A1 2 O 3 precipitated from the 60 wt% A1 2 O 3 melts at ∼1325°± 20°C, which is the boundary of a previously calculated liquid miscibility gap. When the homogenized melts were heat‐treated within this gap, the A1 2 O 3 in the mullite decreased with a corresponding increase in the Al 2 O 3 content of the glass. A similar decrease of Al 2 O 3 in mullite was observed when crystallized melts were reheated at 1725°± 10°C; the lowest A1 2 O 3 content (∼73.5 wt%) was in melts that were reheated for 110 h. All melts indicated that the composition of the precipitating mullite was sensitive to the heat treatment of the melts.