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“Alumina” Surface Modification of Silicon Nitride for Colloidal Processing
Author(s) -
Luther Erik E,
Lange Fred F.,
Pearson Dale S.
Publication year - 1995
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.1151-2916.1995.tb08611.x
Subject(s) - slurry , materials science , aqueous solution , chemical engineering , silicon nitride , silicon , colloid , rheology , precipitation , colloidal silica , mineralogy , inorganic chemistry , metallurgy , composite material , chemistry , organic chemistry , engineering , physics , meteorology , coating
Two different methods are used to coat silicon nitride particles with an alumina precursor to make Si 3 N 4 behave like Al 2 O 3 in aqueous slurries. The first method involves the precipitation of an aluminum hydroxycarbonate from dissolved Al(NO 3 ) 3 during the decomposition of urea. In the second method, dry silicon nitride powder is reacted with aluminum tri‐ sec ‐butoxide in hexane at room temperature. Both methods produce a coated powder in which the electrophoretic and rheological properties of aqueous slurries mimic those of alumina. When salt is added to slurries consisting of coated Si 3 N 4 powder, all rheological evidence suggests the presence of a short‐range repulsive potential that produces a weakly attractive particle network similar to that previously reported for Al 2 O 3 powder. Although electrophoretic and rheological data showed that the coated powder behaved like Al 2 O 3 , consolidation data indicated that slurries of coated powder with added salt did not pack to high density. In addition, these bodies were not plastic as found for bodies consolidated from dispersed and salt‐added Al 2 O 3 slurries.