Comportement thermomécanique des céramiques étudié par spectroscopie mécanique

Abstract

High temperature plastic or even superplastic deformation of fine-grained ceramics is usually

interpreted as due to grain boundary sliding. As grain boundary sliding dissipates energy, mechanical

spectroscopy is well suited to study such a mechanism. In fine-grained tetragonal zirconia, the

mechanical loss exhibits an exponential increase athigh temperature, which accounts for creep

appearance in the material. In silicon nitride, a mechanical loss peak related to dissipation in the

glassy phase pockets has been observed. This peak disappears after annealing leading to the

recrystallization of the amorphous pockets, leadingto a better creep resistance. Silicon nitride sintered

under gas pressure contains a very small amount of glassy phase and consequently exhibits a very

small mechanical loss peak and consequently a strong resistance to deformation until 1450°C.