Microfocusing and Polarization Effects in Spherical Neck
Ceramic Microstructures During Microwave Processing
A. Birnboim, J. P. Calame,1 and Y. Carmel
Institute for Plasma Research
University of Maryland, College Park, Maryland 20742
1Naval Research Laboratory, Washington, DC 20375
101st Annual Meeting & Exposition, The American Ceramic Society
Indianapolis, IN, April 25-28, 1999
ABSTRACT. During microwave sintering of compacted ceramic powders, the electric field distribution within the ceramic body on a macroscale is determined by a combination of the operating frequency, the sample shape and its permittivity. In contrast, our studies show that on a microscopic scale, the local electric fields are disproportionally intense close to grain boundaries and rough surfaces due to strong focusing. Also, the electric field in the inter-particle contact zone exhibits preferred polarization directions despite illumination by a randomly polarized wave. This can lead to a highly nonuniform energy deposition and accelerated mass transfer rates via ponderomotive diffusion and/or plasma generation.
Work supported by AFOSR, Ceramic Materials Program, Grant No. F496209710270.