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Growth of α‐AI 2 O 3 Platelets in the HF‐γy‐AI 2 O 3 System
Author(s) -
Shaklee Charles A.,
Messing Gary L.
Publication year - 1994
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.1151-2916.1994.tb04534.x
Subject(s) - nucleation , supersaturation , seeding , platelet , chemistry , particle size , particle (ecology) , crystallography , materials science , chemical engineering , mineralogy , analytical chemistry (journal) , thermodynamics , chromatography , physics , oceanography , organic chemistry , biology , engineering , immunology , geology
In the presence of a fluorine mineralizer, highly aggregated, <5 μm α‐Al 2 O 3 platelet particles form by vapor transport during the thermal transformation of γ‐alumina. Platelet aggregation was determined to occur by platelet inter‐growth and by edge nucleation on primary α‐Al 2 0 3 platelets. The addition of 10 10 α‐alumina seed particles/cm 3 γ–Al 2 O 3 resulted in the development of discrete particles during the initial stage of transformation. Impingement of the growing platelets during the latter stage of transformation, however, resulted in intergrowth, a process which was not changed by seeding. Particle size distribution broadening was observed to increase with increasing HF and H 2 O concentrations because vapor reactant supersaturation increases the degree of edge nucleation. When initially low HF and H 2 O concentrations were used in seeded systems, however, essentially aggregate‐free α‐Al 2 O 3 platelets of 10–15 μm were obtained.