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Oxidation Behavior of Hot‐Pressed Si 3 N 4
Author(s) -
KIEHLE A. J.,
HEUNG L. K.,
GIELISSE P. J.,
ROCKETT T. J.
Publication year - 1975
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.1151-2916.1975.tb18972.x
Subject(s) - cristobalite , scanning electron microscope , amorphous solid , magnesium , impurity , materials science , mineralogy , chemical stability , diffraction , analytical chemistry (journal) , chemistry , chemical engineering , crystallography , metallurgy , quartz , composite material , optics , organic chemistry , chromatography , physics , engineering
The high‐temperature chemical stability of hot‐pressed Si 3 N 4 was studied between 600° and 1450°C. Reactions were followed by X‐ray diffraction and scanning electron microscopy. In air, this material begins to oxidize at 700° to 750°C; a distinct amorphous siO 2 surface layer results after 24 h at 750°C‐Concomitant formation of cristobalite occurs, depending on exposure time, and is enhanced as temperature is Increased. Magnesium and calcium magnesium silicates form above 1000°C. The data suggest that impurities, e.g. Mg, Ca, and Fe, greatly lower the oxidation resistance of Si 3 N 4 in air.