Chapter 47. Effect of Green Microstructure on Microwave Processing of Alumina: Effect of Particle Size

Summary

The role of green microstructure, especially particle size, in microwave processing of alumina was investigated. Compacts of high purity, submicron alumina powders of different particle sizes were prepared by cold pressing. These were then fired in an industrial microwave oven under identical processing conditions. The resulting microstructures and densities were examined and the resulting data correlated with conventional sintering, in order to gain an insight into the role of particle size on the microwave sintering phenomena. Fast firing by conventional (isothermal heating in a resistance furnace) techniques, as well as by microwave heating, was carried out under similar state (temperature, time) conditions. The resulting microstructures were then compared using stereological (quantitative microscopy) techniques. Although the effect of particle size on microwave sintering was found to be analogous to conventional sintering, our results demonstrate that microwave heating culminates in accelerated densification with a better uniformity and homogeneity of microstructural vis-à-vis conventional fast firing. This holds promise for the fabrication of bulk monoliths/composites with uniform, homogeneous microstructures, and consequently, enhanced mechanical properties and reliability.