Abstract
In this paper, the effect of powder processing conditions on the fracture strength of advanced ceramics is discussed. Manufacturing processes of silicon nitride ceramics and alumina ceramics are utilized to explain the relationship between powder processing conditions and major fracture origin in the ceramics. The preparation conditions of powder slurry are found affecting the structure and strength of powder granules, which can influence the properties of green compact and thus the quality of sintered ceramics. These phenomena can be investigated by using new characterization tools such as the liquid immersion method and the observation technique using thinned ceramics specimen under the transmission mode. Also, very small amount of coarse particles contained in the powder slurry is found starting the fracture in ceramics by using wet sieve analysis and the observation technique with thinned ceramic specimen. As a result, it is found that the major ceramics fracture is originated from the large pores and coarse particles in powder granules, green compact and sintered ceramics. They can be unintentionally introduced in the manufacturing steps of ceramics, such as powder slurry preparation, spray drying, and forming process of green compact. By making use of these characterization tools, effective processing conditions to eliminate the large pores and coarse particles can be identified for producing high quality advanced ceramics.
