The propagation and absorption of electromagnetic waves in porous ceramic materials

Summary form only given. One of the most critical technical issues associated with the microwave processing of ceramics is understanding the propagation of electromagnetic waves within the physical structure and the interaction mechanisms of the fields with the materials that make up the green body. These factors directly determine the types of components and possible new materials that can be effectively and uniquely processed. The physical size scales of interest for this problem span a very large range. On the macroscopic level one is dealing with the overall part shape, and the principle concern is modeling the energy deposition distribution and thermal flow inside a complex shaped part under very high heating rates. The goals of such procedures are to optimize the absorption of energy and simultaneously minimize thermal gradients. Methods and examples of this large-scale modeling, using finite difference EM codes and time-dependent thermal codes, will be described. However, during the vast majority of the sintering cycle, the ceramic is porous and the dielectric properties (which determine the behavior of microwaves within the structure, including the power absorption) are quite different from those of a fully dense body.