Strength of hot isostatically pressed Si sub 3 N sub 4 after heat treatment in Ar-O sub 2 and H sub 2 -H sub 2 O

Journal Article · Tue May 01 00:00:00 EDT 1990 · Journal of the American Ceramic Society; (USA)

DOI:https://doi.org/10.1111/j.1151-2916.1990.tb05223.x· OSTI ID:5996217

Kim, H E; Moorhead, A J ^[1]

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1. Oak Ridge National Lab., TN (USA). Metals and Ceramics Div.

The effects of heat treatment in Ar-O{sub 2} and H{sub 2}-H{sub 2}O atmospheres on the flexural strength of hot isostatically pressed Si{sub 3}N{sub 4} were investigated. Increases in room-temperature strength, to values significantly above that of the aspolished material, were observed when the Si{sub 3}N{sub 4} was exposed at 1400{degrees}C to (1) H{sub 2} with water vapor pressure (P{sub H{sub 2}O}) greater than 1 {times} 10{sup {minus}4} MPa or (2) Ar with oxygen partial pressure (P{sub 02}) of between 7x{sup {minus}6} and 1.5 {times} 10{sup {minus}5} MPa. However, the strength of the material was degraded when the P{sub H{sub 2}O} in H{sub 2} was lower than 1 {times} 10{sup {minus}4} ZMPa, and essentially unaffected when the P{sub 02} in Ar was higher than 1.5 {times} 10{sup {minus}5} MPa. The authors suggest that the observed strength increases are the result of strength-limiting surface flaws being healed by a Y{sub 2}Si{sub 2}O{sub 7} layer formed during exposure.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5996217
• Journal Information: Journal of the American Ceramic Society; (USA), Vol. 73:5; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
OXYGEN
PARTIAL PRESSURE
SILICON NITRIDES
FLEXURAL STRENGTH
HEAT TREATMENTS
HOT PRESSING
ARGON IONS
HYDROGEN
OXIDATION
VERY HIGH TEMPERATURE
WATER VAPOR
CHARGED PARTICLES
CHEMICAL REACTIONS
ELEMENTS
FABRICATION
FLUIDS
GASES
IONS
MATERIALS WORKING
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
PNICTIDES
PRESSING
SILICON COMPOUNDS
VAPORS
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