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Si 3 N 4 /SiC‐Whisker Composites without Sintering Aids: III, High‐Temperature Behavior
Author(s) -
Pezzotti Giuseppe,
Tanaka Isao,
Okamoto Taira
Publication year - 1991
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.1151-2916.1991.tb06883.x
Subject(s) - whiskers , whisker , materials science , sintering , composite material , hot isostatic pressing , composite number , dwell time , transgranular fracture , hot pressing , grain boundary , monocrystalline whisker , intergranular corrosion , microstructure , silicon carbide , intergranular fracture , medicine , clinical psychology
The fracture behavior at high temperature of a Si 3 N 4 ‐based SiC‐whisker composite fabricated by hot isostatic pressing without sintering aids is compared with that of other highly refractory materials. Particular attention is directed toward evaluating the slow‐crack‐growth resistance of the composite up to 1440°C and relating this resistance to the microfracture behavior of Si 3 N 4 grains, SiC whiskers, and the intergranular, glassy SiO 2 phase. Only thick whiskers operate to bridge the wake of the crack; these whiskers may make a positive contribution to the slow‐crack‐growth resistance. Impurities detected by EDX microanalysis at the grain boundary, however, apparently degrade the high‐temperature properties, a finding supported by internal‐friction measurements. Nevertheless, the high potential of the system without sintering aids for high‐temperature structural applications has been demonstrated by the time to failure estimated from the measured slow‐crack‐growth resistance for a fixed flaw size.