Engineering ceramics – the process problem

Abstract

The main problem to be solved before advanced engineering ceramics can become industrial reality is that components having reliable and consistent properties cannot be made, and rejection rates can be as high as 95%, in stark contrast to the situation with metals and polymers. This results from the small size of defect sufficient to cause failure in a ceramic and the variability in the population density of such defects. It is unlikely that sufficiently sensitive non-destructive testing and diagnostic techniques will become available, and so success will depend on the development of intrinsically reliable process technology. The nature and origin of defects in ceramics are discussed and related to raw material characteristics and process technology. The changes that are needed in raw materials and processes are outlined, and the various approaches to intrinsically reliable techniques (such as the colloidal processing of submicrometre powders, sol–gel methods, etc.) are critically assessed in the light of the need for industrially realistic processes. An attempt is made to assess likely future developments such as ceramic fibre reinforced ceramics. MST/409