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Strength of Hot Isostatically Pressed Si 3 N 4 After Heat Treatment in Ar‐O 2 and H 2 ‐H 2 O
Author(s) -
Kim HyounEe,
Moorhead Arthur J.
Publication year - 1990
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.1151-2916.1990.tb05223.x
Subject(s) - flexural strength , limiting , oxygen , partial pressure , materials science , analytical chemistry (journal) , water vapor , chemistry , composite material , metallurgy , mineralogy , mechanical engineering , organic chemistry , engineering , chromatography
The effects of heat treatment in Ar‐O 2 and H 2 ‐H 2 O atmospheres on the flexural strength of hot isostatically pressed Si 3 N 4 were investigated. Increases in room‐temperature strength, to values significantly above that of the aspolished material, were observed when the Si 3 N 4 was exposed at 1400°C to (1) H 2 with water vapor pressure ( P H2O ) greater than 1 × 10 −4 MPa or (2) Ar with oxygen partial pressure ( P O2 ) of between 7 × 10 −6 and 1.5 × 10 −5 MPa. However, the strength of the material was degraded when the P H2O in H 2 was lower than 1 × 10 −4 MPa, and essentially unaffected when the P O2 in Ar was higher than 1.5 × 10 −5 MPa. We suggest that the observed strength increases are the result of strength‐limiting surface flaws being healed by a Y 2 Si 2 O 7 layer formed during exposure.