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Grain Growth in Microwave‐Annealed Alumina
Author(s) -
Janney Mark A.,
Kimrey Hal D.,
Schmidt Monica A.,
Kiggans James O.
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.tb07159.x
Subject(s) - materials science , grain growth , microwave , microstructure , grain size , annealing (glass) , ceramic , activation energy , metallurgy , growth rate , aluminium , mineralogy , composite material , chemistry , physics , geometry , organic chemistry , mathematics , quantum mechanics
Normal grain growth in dense, fine‐grained, aluminum oxide‐0.1 wt% MgO was studied under both conventional furnace and 28‐GHz microwave furnace annealing conditions. The microstructural changes that occurred were the same for both sets of samples; soap bubble microstructures were observed and the aspect ratios and shape factors did not change during the anneals. The kinetics of grain growth were greatly increased by the 28‐GHz microwave anneals; e.g., the grain growth rate at 1500°C in the microwave furnace was the same as the rate at 1700°C in the conventional furnace. Also, the activation energy for grain growth was reduced by the microwave anneal from 590 kJ/mol (conventional) to 480 kJ/mol (microwave). Finally, these results demonstrate that a “microwave effect” can exist in a dense ceramic body and that no free pore‐solid interfaces are necessary.