Processing

The intrinsic properties of materials depend on bonding and crystal structure. For ceramics, the microstructure that results from the processing cycle also has a strong influence on performance. Because a majority of commercial ceramic parts are fabricated from fine powdered precursors, microstructure development during densification must be understood to control the performance of the final part. The steps in the process include powder synthesis, consolidation of powders/shaping, and densification. Powder synthesis methods range from the traditional “heat and beat” approach that uses repeated calcination and mechanical grinding steps [33] to more sophisticated reaction-based and chemical preparation methods [34]. Powder synthesis has been the subject of technical articles and reviews and will not be discussed further in this chapter. Likewise, the consolidation methods used to shape powders such as dry pressing and isostatic pressing are well documented elsewhere [35]. This section will review some key issues related to microstructure development during densification. Typical microstructures produced by solid-state sintering will be contrasted with those formed by liquid phase sintering to highlight the potential effects on performance.