A crystalline Si{sub 3}N{sub 4}/amorphous Si{sub 3}N{sub 4} composite

Journal Article · Thu Feb 01 04:00:00 EST 1996 · Journal of the American Ceramic Society

DOI:https://doi.org/10.1111/j.1151-2916.1996.tb08134.x· OSTI ID:211698

Reimanis, I E; Petrovic, J J; Suematsu, Hisayuki; Mitchell, T E ^[1]

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1. Los Alamos National Lab., NM (United States)

A composite consisting of elongated {alpha}-Si{sub 3}N{sub 4} crystallites (5--50 {micro}m in diameter) embedded in an amorphous Si{sub 3}N{sub 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 1,200 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 1,400 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 1,200 C is increased due to extensive microcracking. The Vickers hardness at 1,200 C also increased significantly as a result of the heat treatment. The relationship between the mechanical properties and the microstructure is discussed.

• Sponsoring Organization: USDOE
• OSTI ID: 211698
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 2 Vol. 79; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AMMONIA
CHEMICAL VAPOR DEPOSITION
COMPOSITE MATERIALS
ENERGY-LOSS SPECTROSCOPY
FRACTURE PROPERTIES
HARDNESS
HEAT TREATMENTS
HYDROGEN
MICROSTRUCTURE
OPTICAL MICROSCOPY
SILICON CHLORIDES
SILICON NITRIDES
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION