Tensile Creep in the Next Generation Silicon Nitride

Published

January 1, 2001

Author(s)

F Lofaj, Sheldon M. Wiederhorn, Gabrielle G. Long, P R. Jemian

Abstract

The tensile creep behavior of a Lu-containing silicon nitride (SN 281) was characterized in the temperature range of 1350oC to 1550oC for test periods up to 10000h. For the same test conditions, the minimum strain rates were several orders of magnitude less than that of other commercial grades of silicon nitride. The creep rate had an exponential dependence on applied stress and dependence on temperature with activation energy of 784 (plus/minus) 105kJ/mol. No change in secondary phase compositon was found after creep in for 10 000 h at 1400oC. TEM and anamalous ultra small angle X-ray scattering data revealed only very low concentration of multigrain junction cavities. The creep behavior was discussed in terms of parameters that are important to the cavitation creep model suggested by Luecke and Wiederhorn. It was found that the increase in creep resistance in SN 281 considerably exceeds predictions based on extrapolation from the properties of silicon nitride ceramics sintered with other lanthanides. The most probable mechanism for the effect is a significant suppression of cavitation via an increase of the effective viscosity of the secondary phases and/or an increase of the threshold stress for cavitation.

Proceedings Title

Composites, Advanced Ceramics, Materials, and Structures, Annual Conference | 25th | | American Ceramic Society

Volume

22

Issue

No. 3

Conference Dates

January 1, 2001

Conference Location

Undefined

Conference Title

Ceramic Engineering and Science Proceedings

Pub Type

Conferences

Keywords

cavitation, lutetium, silicon nitride, tensile creep

Citation

Lofaj, F. , Wiederhorn, S. , Long, G. and Jemian, P. (2001), Tensile Creep in the Next Generation Silicon Nitride, Composites, Advanced Ceramics, Materials, and Structures, Annual Conference | 25th | | American Ceramic Society, Undefined (Accessed December 14, 2024)