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Fundamentals of Microwave-Material Interactions and Sintering

Published online by Cambridge University Press:  21 February 2011

Wayne R. Tinga*
Affiliation:
Department of Electrical Engineering, 238 Civil/Electrical Building, University of Alberta, Edmonton, Alberta, T6G 2G7, Canada
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Abstract

Basic interaction mechanisms are shown to depend strongly on the dielectric and magnetic properties of a process material. This causes a strong dependence of power absorption on frequency, material particle size, shape, temperature, and density. Sintering dynamics cause the microstructure of the treated material to change resulting in a change in microwave (1W) heating uniformity and rate. The concept of dielectric mixtures is introduced to predict the dielectric and heating properties of a host material with its inclusions in the form of shells, ellipsoids, spheres, disks and needles. Simplified models are described to give a process designer some insight into the behavior of MW sintering. Microwave power, by its very nature, gives better heating control and efficiency and provides internal heat to aid the material transport during sintering. No inherent temperature limit exists for MW sintering although refractory materials used to contain the process material create an artificial upper limit. It is shown that very high (1500–2000°C) temperatures in small samples can be readily achieved using commercial microwave ovens if appropriate MW transparent sample holders are used.

Type
Research Article
Copyright
Copyright © Materials Research Society 1988

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