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Influence of grain size on the tensile creep behavior of ytterbium-containing silicon nitride

Wiederhorn, S. M.; Lopez, A. R.D.; Luecke, W. E.; Hoffmann, M. J.; Hockey, B. J.; French, J. D.; Yoon, K. J.

Abstract:
The effect of grain size on the tensile creep of silicon nitride was
investigated on two materials, one containing 5% by volume Yb2O3, the
other containing 5% by volume Yb2O3 and 0.5% by mass Al2O3. Annealing
of the Al2O3-free silicon nitride for a longer period during processing
increased the grain size by a factor of 2. This increase did not affect
the tensile creep rate; the grain size exponent of the creep rate
differed little from zero, p = -0.20 +/- 1.37 (95% confidence level).
This finding supports the more recent theories of tensile creep for
which p = 0 or -1 and rejects the more classical theory of
solution-precipitation. In compression, a more limited data set showed
p = -1.89 +/- 1.72 (95 % confidence level). In contrast to the
Al2O3-free material, a longer term anneal of the Al2O3-containing
material during processing did not increase its grain size. Despite
this, the longer-annealed Al2O3-containing material crept 10 to 100
times slower than the short-annealed material. The enhancement of creep
resistance may be a consequence of SiAlON formation during the
additional annealing, which reduces the Al cont ... mehr


Zugehörige Institution(en) am KIT Institut für Keramik im Maschinenbau (IKM)
Publikationstyp Zeitschriftenaufsatz
Jahr 2004
Sprache Englisch
Identifikator ISSN: 0002-7820
KITopen-ID: 1000007662
Erschienen in Journal of the American Ceramic Society
Band 87
Heft 3
Seiten 421-430
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