Abstract
The multi-layered silicon nitride with dense/porous layers achieved high strength and high damage tolerance at the same time. The porous layers derived from various starting powders, i.e., whiskers, coarse/fine powder mixture and seed crystal were applied to control the porous structure and to attain the aimed mechanical properties. The effects of microstructure on the properties, the oxidation behavior and the strength at 1400 degree Celsius, were surveyed to optimize the layered structure. The developed material showed little strength degradation after the thermal cycle test. This study is supported by METI, Japan, under the Synergy Ceramics Project.
