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Thermal Runaway and its Control in Microwave Heated Ceramics

Published online by Cambridge University Press:  25 February 2011

Gregory A. Kriegsmann
Gregory A. Kriegsmann*
Affiliation:
Department of Mathematics Center for Applied Mathematics and Statistics New Jersey Institute of Technology Newark, NJ 07102
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Abstract

The heating of a ceramic slab under TEM illumination is modeled and analyzed in the small Biot number regime. The temperature distribution is almost spatially uniform in this limit and its evolution in time is governed by a first order nonlinear amplitude equation. This equation admits a time independent solution which is a multivalued function of the microwave power. The dynamics of the heating process are deduced, from the amplitude equation and the multivalued response, and are dependent upon the microwave power and initial conditions. The results of this analysis give a plausible explanation of certain difficulties arising in sintering experiments, such as thermal runaway. A simple control process is presented and analyzed which mitigates against these deleterious effects. Abbreviated parameter studies are performed showing trends in the controlled heating process.

A quasi-three-dimensional problem modeling the heating process of a thin cylindrical sample in a waveguide applicator is also presented. For certain excitations the physical phenomenon deduced from this model and the required control process are the same as those obtained for the slab. For other excitations there is a strong spatial structure along the axis of the sample. For a certain choice of parameters the middle portion of the sample is at an elevated temperature while the remaining portion is at a much lower temperature. This phenomenon may be useful in joining applications.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 269: Symposium L – Microwave Processing of Materials III , 1992 , 257
Copyright
Copyright © Materials Research Society 1992

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References

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