Thermal Cycling Effects on Dynamic Mechanical Properties and Crystallographic Structures of Silicon Nitride-Based Structural Ceramics

Thermal cycling effects on dynamic mechanical properties of hot pressed silicon nitride (HPSN) based structural ceramics were investigated in a simulated thermal cycling environment from room temperature up to 1100°C. Two monolithic silicon nitrides and two silicon nitride composites reinforced with silicon carbide whiskers were studied in such an environment. Experiments show that the dynamic mechanical properties of the tested materials are influenced by thermal cycle. The materials stiffened slightly while damping capacity decreased slightly during each thermal cycle. X-ray diffraction (XRD) was subsequently used to examine the corresponding crystallographic alterations. The XRD patterns show that the amorphous glass phases in the silicon nitride matrix were partially crystallized during thermal cycling.