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Spontaneous Cracking in Unfired Magnesia Compacts Upon Standing in Air
Author(s) -
DAVIES MYRON O.,
GRIMES HUBERT H.,
MAY CHARLES E.
Publication year - 1961
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.1151-2916.1961.tb15351.x
Subject(s) - cracking , materials science , magnesium , metallurgy , pressing , carbonate , composite material , oxide , water vapor , carbon dioxide , chemistry , organic chemistry
Analytical‐grade magnesium oxide powder without binder was compressed hydrostatically to 50,000 lb. per sq. in. to form compacts. When exposed to moist air immediately after pressing, these compacts developed irregularly shaped cracks. Controlled tests, in which these compacts were exposed for various lengths of time to various atmospheres, indicated that in general water vapor, carbon dioxide, and residual stresses had to be present if cracking was to occur. The probable cause of the cracking was the formation of a less dense and mechanically weak basic carbonate of magnesium at crystallite surface points of high stress concentration which developed during the compacting. The adsorption of dry CO 2 at such sites prevented subsequent delayed fracture.