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A Crystalline Si3N4/Amorphous Si3N4 Composite
Author(s) -
Reimanis Ivar E.,
Petrovic John J.,
Suematsu Hisayuki,
Mitchell Terrence E.
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.tb08134.x
Subject(s) - materials science , indentation , amorphous solid , crystallite , composite material , fracture toughness , microstructure , composite number , indentation hardness , vickers hardness test , chemical vapor deposition , amorphous carbon , metallurgy , crystallography , nanotechnology , chemistry
A composite consisting of elongated α‐Si 3 N 4 crystallites (5–50 (Am in diameter) embedded in an amorphous Si 3 N 4 matrix was synthesized by chemical vapor deposition. The hardness and indentation fracture toughness of the amorphous matrix and of the composite have been evaluated at temperatures from ambient to 1200°C. It was found that the crystallites have relatively little influence on the hardness and indentation fracture toughness when the surrounding matrix is amorphous. However, a 1400°C heat treatment of the material results in a matrix consisting of small crystals (100 nm in diameter) surrounded by carbon‐containing regions which appear to be amorphous in the TEM; TEM and EELS in nearby triple points revealed the presence of amorphous carbon. After heat treatment, the indentation fracture toughness at ambient and at 1200°C is increased due to extensive microcracking. The Vickers hardness at 1200°C also increased significantly as a result of the heat treatment. The relationship between the mechanical properties and the microstructure is discussed.