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Coprecipitation and Processing of Mullite Precursor Phases
Author(s) -
Zhou Minghua,
Ferreira José M. F.,
Fonseca António T.,
Baptista João L.
Publication year - 1996
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.1151-2916.1996.tb07992.x
Subject(s) - coprecipitation , mullite , materials science , microstructure , silicic acid , equiaxed crystals , metallurgy , chemical engineering , slurry , aluminium , mineralogy , precipitation , inorganic chemistry , ceramic , chemistry , composite material , physics , meteorology , engineering
Ultrafine powders of aluminum‐rich mullite precursor phases were prepared by spraying mixed acid solutions of silicic acid and aluminum chloride into ammonium hydroxide at different pH values. The aluminum‐rich composition was chosen to avoid abnormal grain growth of the mullite grains caused by silica‐rich liquid phases. The influence of coprecipitation pH on particle size, zeta potential, and the mixing degree of aluminum and silicon in the precipitated powders and on the sintered microstructures have been described. In the basic pH region, the degree of mixing of both components increased as the pH of coprecipitation decreased. Under these conditions, direct slip casting of the coprecipitated slurries was possible, and fine and equiaxed microstructures could be obtained in the sintered bodies.