High Temperature Creep of Ceramics.
Final technical rept. 1 Feb 73-31 Jan 76,
BATTELLE COLUMBUS LABS OHIO
Pagination or Media Count:
Tensile and compression creep measurements were made on yttria-stabilized zirconia YSZ, hot-pressed silicon nitride and silicon materials, in atmospheres including air, nitrogen, argon and vacuum. For relatively fine-grained YSZ below 40 microns, the 1.5 power of the applied stress at low stresses and with the stress cubed at high stresses, but results for coarse grained specimens can generally be fitted by the cube dependence. Creep activation energies for YSZ are found to be 128 kcalmole independent of yttria content, impurity level, grain size and porosity distribution. For the silicon compounds, at least two different creep mechanisms are operative in the range of temperatures and stresses employed in this study. A grain boundary sliding mechanism, characterized by a stress dependence of two and an activation energy of 168 kcalmole, appears to be operative for hot-pressed silicon nitride but a viscous creep mechanism predominates for some SiAlON materials, where a linear stress dependence and an activation energy of 94 kcalmole have been measured. Author
- Ceramics, Refractories and Glass