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High‐Temperature Strength and Cavitation Threshold of Silicon Nitride–Silica Ceramics
Author(s) -
Zeng Jianren,
Tanaka Isao,
Miyamoto Yoshinari,
Yamada Osamu,
Niihara Koichi
Publication year - 1992
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.1151-2916.1992.tb05464.x
Subject(s) - materials science , flexural strength , intergranular corrosion , composite material , cavitation , phase (matter) , silicon nitride , deformation (meteorology) , ceramic , mineralogy , microstructure , thermodynamics , chemistry , physics , organic chemistry , layer (electronics)
The role of high‐purity silica in the fracture of Si 3 N 4 at high temperatures has been investigated. The flexural strength at 1400°C was found to be greater than that at room temperature. Little plastic deformation was observed even when 10 wt% SiO 2 was added and the strain rate was decreased 2 orders of magnitude from that for a standard bend test. Microstructural observations revealed that the glassy phase was localized at intergranular pockets when SiO 2 additions were ≤ 10 wt%. High strength at 1400°C despite the presence of a fairly large amount of glassy phase is attributed to a high cavitation threshold in such glassy pockets consisting of high‐purity SiO 2 . However, the deformation behavior changed abruptly for SiO 2 additions of 10 and 20 wt%, which is explained by the morphological change of the glassy phase to thicker intergranular layers which allow macroscopic viscous flow.