COMPACTION AND GRAIN-GROWTH IN ALUMINA CERAMICS UNDER MICROWAVE SINTERING

The laws governing the transformations of the porous and grain structu res that occur in Al2O3-based ceramics during microwave sintering are investigated. These processes are very similar to analogous processes that occur during coherent compaction of powders. Under microwave sint ering the ceramic preforms retain a wide range of porosity and microst ructure for a long time. As a result strong capillary forces exist thr oughout the process, causing active compaction. On the basis of the ex perimental data we suggest that the heating rate and the bulk mode of the heating are not the only factors that accelerate the consolidation of the ceramics under microwave sintering.