Design Principles for Microwave Heating and Sintering

Abstract

AbstractMicrowave heating equations are shown to have a complex functional dependence on material and process parameters such as composition, density, temperature, frequency and geometry. Power flow and its deposition in the presence of simple material shapes are used to illustrate relevant electromagnetic boundary conditions. Various types of applicator design using standing wave and travelling wave structures are discussed with respect to the results on power density, process efficiency and controllability. The problem of measuring and controlling the temperature inside a microwave system is addressed with emphasis on the use of thermocouples and infrared thermometry. Some of the problems peculiar to high temperature processing are considered. A review of the dielectric and magnetic property variation with temperature and frequency is given in order to understand the complexity and difficulty of uniformity of heating even with microwaves. The use of combination processing, for example, microwaves and infrared heating, is discussed. A short bibliography is presented listing some important publications in the field.