W/Si3N4 composite ceramics reinforced with core‐shell W‐crystallized oxynitride phase

Abstract

AbstractThe introduction of a reinforced phase is an effective way to toughen silicon nitride ceramics. However, the residual stress caused by thermal expansion mismatch between the reinforced phase and Si3N4 ceramics may generate interfacial defects and deteriorate the strength of silicon nitride ceramics. Therefore, a novel strategy for optimizing interface structure to reinforceW/Si3N4 composite ceramics has been proposed. After introducing (Y2O3, Al2O3, W) particles in the W/Si3N4 ceramics, the melted liquid phase encompasses the W particles at high temperature and in situ‐generates the core‐shell structural W‐crystallized oxynitride phase as the material cools. As a result, the interfacial defect was inhibited after the core‐shell W‐crystallized oxynitride phase was introduced. With the increase of W addition from 0 to 4 wt%, the flexural strength of the W/Si3N4 ceramics with introducing core‐shell structural W‐crystallized oxynitride phase increases from 985 to 1168 MPa, and the fracture toughness improves from 6.5 to 9.0 MPa m1/2.