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Strengthening of Alumina by Formation of a Mullite/Glass Layer on the Surface
Author(s) -
Kim HyounEe,
Moorhead A. J.,
Kim SangHak
Publication year - 1997
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.1151-2916.1997.tb03064.x
Subject(s) - mullite , materials science , layer (electronics) , ceramic , composite material , abrasive , aluminium silicate , diamond , substrate (aquarium) , silicate , reducing atmosphere , metallurgy , chemical engineering , oceanography , engineering , geology
A layer composed of mullite and silicate glass was caused to form on the surface of a high‐purity alumina ceramic in order to enhance the strength of the material. The layer was formed by exposing the specimens above a bed of SiC platelets at 1400°3C to a flowing H 2 atmosphere containing ∼0.1% H 2 O. A reaction between the SiC platelets and the H 2 O in the environment resulted in the generation of SiO gas. Some of the SiO gas subsequently reacted with ambient H 2 O in the atmosphere, forming SiO 2 “smoke” which was deposited on, and reacted with, the alumina substrate. The strength of the ceramic was significantly improved by the reaction layer, which was found to be comprised of mullite and silicate glass. The increases in strength (about 60% above that of the material in the “as‐polished” condition) was attributed to the blunting of surface cracks. A similar strengthening effect was observed in samples of the material which had been ground with a 220‐grit diamond abrasive wheel (as had all of the samples) but not polished.