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Mathematical Model of Thermal Spikes in Microwave Heating of Oxide Ceramic Fibers

Published online by Cambridge University Press:  15 February 2011

J. R. Thomas Jr ,
Wesley P. Unruh  and
Gerald J. Vogt
J. R. Thomas Jr
Affiliation:
Los Alamos National Laboratory, Los Alamos, NM 87545
Wesley P. Unruh
Affiliation:
Los Alamos National Laboratory, Los Alamos, NM 87545
Gerald J. Vogt
Affiliation:
Los Alamos National Laboratory, Los Alamos, NM 87545
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Abstract

Experiments on microwave sintering of ceramic fibers in a single-mode cavity have revealed the presence of thermal spikes and “hot spots” which sometimes travel along the fiber and eventually disappear. They are triggered by relatively small increases in microwave power, and thus have obvious implications for the development of practical microwave-based fiber processing systems. These hot spots are conjectured to originate at slight irregularities in the tow morphology, and propagate as the result of solid phase transitions which take place at elevated temperatures and reduce the dielectric loss coefficient є”.

An elementary mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena, thus lending support to our conjecture. This model is based on the assumption of one-dimensional heat conduction along the axis of the fiber tow, and radiation losses at the surface.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 347: Symposium O – Microwave Processing of Materials IV , 1994 , 363
Copyright
Copyright © Materials Research Society 1994

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References

1. Vogt, Gerald J., Unruh, Wesley P., and Thomas, J. R. Jr, “Experimental Observations of Thermal Spikes in Microwave Processing of Ceramic Oxide Fibers” (This Proceedings)Google Scholar
2. Xi, Weiguo and Tinga, W. R., in Microwave Processing of Materials III, edited by Beatty, R. L., Sutton, W. H., and Iskander, M. F. (Mater. Res. Soc. Proc. 269, Pittsburgh, PA, 1992) pp. 569–577.Google Scholar
3. Tinga, W. R., unpublished data (private communication).Google Scholar
4. “Properties of Nextel™ 312, 440, & 480 Ceramic Fibers”, 3M Ceramic Materials Department, St. Paul, MN (1989).Google Scholar