Mechanical properties of hot isostatically pressed Si[sub 3]N[sub 4] and Si[sub 3]N[sub 4]/SiC composites

Journal Article · Mon Mar 01 00:00:00 EST 1993 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1993.0626· OSTI ID:6710718

Unal, O ^[1]; Petrovic, J J ^[2]; Mitchell, T E ^[1]

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1. Center for Materials Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

The mechanical properties of hot isostatically pressed monolithic Si[sub 3]N[sub 4] and Si[sub 3]N[sub 4]--20 vol. % SiC composites have been studied by microindentation at temperatures up to 1400 [degree]C. Indentation crack patterns and microstructures have been examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. It is shown that dense Si[sub 3]N[sub 4] base materials can be synthesized by HIPing without densification aids. Both the monolithic Si[sub 3]N[sub 4] and the Si[sub 3]N[sub 4]/SiC composites exhibit high hardness values which gradually decrease with increasing temperature. Both types of material show low fracture toughness values apparently because of strong interfacial bonding. On the other hand, the fracture toughness of the composite is about 40% higher than that of the monolithic material, due to the presence of the 20 vol. % SiC whiskers. A crack deflection/debonding mechanism is likely to be responsible for the higher toughness observed in the composite. High resolution electron microscopy shows that the grain boundaries in both samples contain a thin SiO[sub 2] layer.

• OSTI ID: 6710718
• Journal Information: Journal of Materials Research; (United States), Vol. 8:3; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
MECHANICAL PROPERTIES
SILICON CARBIDES
MICROSTRUCTURE
SILICON NITRIDES
FRACTURE PROPERTIES
GRAIN BOUNDARIES
HOT PRESSING
MICROSCOPY
SILICON OXIDES
TEMPERATURE RANGE 1000-4000 K
WHISKERS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
FABRICATION
MATERIALS
MATERIALS WORKING
MONOCRYSTALS
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
PRESSING
SILICON COMPOUNDS
TEMPERATURE RANGE
360603* - Materials- Properties