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Oxidation Behavior of SiC‐Whisker‐Reinforced Alumina‐Zirconia Composites
Author(s) -
BackhausRicoult Monika
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.tb07790.x
Subject(s) - whisker , materials science , mullite , whiskers , silicon carbide , monocrystalline whisker , composite material , cubic zirconia , microstructure , graphite , grain boundary , scanning electron microscope , silicon monoxide , silicon , ceramic , metallurgy
During high‐temperature oxidation in air, SiC‐whisker‐reinforced Al 2 O 3 —ZrO 2 composites degrade by the formation of a whisker‐depleted mullite‐zirconia scale. The reaction kinetics have been studied as a function of time and temperature for composites with whiskers preoxidized for different times. The evolution of the microstructure has been investigated by optical, scanning and transmission electron microscopy. Possible reaction mechanisms have been discussed. A model compatible with our observations on Al 2 O 3 —ZrO 2 —SiC and the results reported in the literature for Al 2 O 3 —SiC whisker composites is proposed: The oxidation occurs at an internal reaction front. Oxygen diffuses along dislocations and grain boundaries through the mullite scale to react at this front with silicon carbide, thereby forming amorphous silica and graphite. Silica penetrates grain boundaries and further reacts with alumina and zirconia to form mullite and zircon, while the second reaction product, graphite, is oxidized into carbon monoxide when the reaction front moves deeper into the sample.