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Preparation of β‐Silicon Nitride Seeds for Self‐Reinforced Silicon Nitride Ceramics
Author(s) -
Ramesh Peelamedu D.,
Oberacker Rainer,
Hoffmann Michael J.
Publication year - 1999
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.1151-2916.1999.tb01969.x
Subject(s) - silicon nitride , materials science , dissolution , phosphoric acid , precipitation , grain boundary , nitride , ceramic , liquid phase , phase (matter) , liquid nitrogen , chemical engineering , silicon , analytical chemistry (journal) , metallurgy , composite material , chemistry , microstructure , chromatography , thermodynamics , organic chemistry , physics , layer (electronics) , meteorology , engineering
This paper describes a method for the preparation of silicon nitride (Si 3 N 4 ) seeds that have an average aspect ratio of ∼4. The seeds are prepared via heat treatment of a powder mixture that contains alpha‐phase‐rich Si 3 N 4 and 0.5 wt% Y 2 O 3 at a temperature of 1800°C and a nitrogen pressure of 35 kPa. A Y‐Si‐O‐N liquid forms during heat treatment; this liquid acts as a flux for seed precipitation. During cooling, the Y‐Si‐O‐N liquid transforms to a thin intergranular grain‐boundary phase and causes strong agglomeration of the seeds. The seeds can be isolated by dissolving the grain‐boundary phase in hot phosphoric acid, followed by an ultrasonic treatment (for 30 min). The method can be used to produce large quantities of seeds.