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A model for microwave processing of compositionally changing ceramic systems

Published online by Cambridge University Press:  03 March 2011

Daniel J. Skamser ,
Jeffrey J. Thomas ,
Hamlin M. Jennings  and
D. Lynn Johnson
Daniel J. Skamser
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive/MLSF 2036, Evanston, Illinois 60208-3108
Jeffrey J. Thomas
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive/MLSF 2036, Evanston, Illinois 60208-3108
Hamlin M. Jennings
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive/MLSF 2036, Evanston, Illinois 60208-3108
D. Lynn Johnson
Affiliation:
Department of Materials Science and Engineering, Northwestern University, 2225 North Campus Drive/MLSF 2036, Evanston, Illinois 60208-3108
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Abstract

A finite-difference model was used to simulate the temperature and composition distributions produced inside a specimen heated with microwave energy during a process involving a change in composition. The dielectric properties of the specimen change with composition, resulting in nonuniform microwave power absorption and steady-state temperature gradients. When the specimen becomes less lossy as it reacts, or if the changes in the microwave heating properties are gradual, the reaction proceeds relatively uniformly and the volumetric microwave heating creates an inside-out reaction profile leading to increased conversions for processes such as reaction bonding and chemical vapor infiltration (CVI). If the specimen becomes more lossy as it reacts, then the reaction proceeds nonuniformly with rapid reaction rates in the hottest parts of the specimen and little or no reaction in the cooler areas. The process may then occur as a reaction front which moves along the specimen, as with combustion synthesis. This type of processing has potential advantages and disadvantages depending on the system.

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Articles
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Journal of Materials Research , Volume 10 , Issue 12 , December 1995 , pp. 3160 - 3178
Copyright
Copyright © Materials Research Society 1995

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References

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