High-temperature stiffness and damping measurements to monitor the glassy intergranular phase in liquid-phase-sintered silicon carbides

Detailed stiffness and internal friction (Q(-1)) versus temperature curves were obtained for liquid-phase-sintered silicon carbides using advanced resonant beam analysis up to 1400 degrees C. As-sintered materials display a stable Q(-1)-peak near 1100 degrees C, superimposed on an increasing background. The change of stiffness associated with the damping peak is quantitatively related to the amount of matter in pockets of the amorphous intergranular phase in which the refractory SiC matrix grains are embedded. The successful removal of the amorphous pockets by annealing at 1900 degrees C is deduced from the disappearance of the damping peak and confirmed with transmission electron microscopy.status: publishe