Accession Number:

ADA429617

Title:

Tailoring of Grain Boundary Chemistry to Produce Super Creep-Resistant Alumina

Descriptive Note:

Final rept. 1 Apr 2001-30 Sep 2004

Corporate Author:

LEHIGH UNIV BETHLEHEM PA CENTER FOR ADVANCED MATERIALS AND NANOTECHNOLOGY

Report Date:

2004-12-12

Pagination or Media Count:

98.0

Abstract:

The Lehigh group has performed experimental and computational studies to determine the impact of dopants, especially rare earth elements, on the high temperature transport properties including creep and densification of alumina. We discovered, along with other groups , that the addition of trace amounts 1000 ppm of rare earth dopants, such as yttrium, lanthanum and neodymium, to fine-grained alumina i.e., 1-3 micron grain size reduces the creep rate by several orders of magnitude. The consensus emerging from this work is that these dopants segregate to grain boundaries due to a mismatch in ionic size and hinder diffusional transport and thereby Coble creep. Further investigation suggests that the observed behavior is associated with a solid solution effect. Complementary simulational work employing atomistic models confirms the propensity for dopant segregation and the increase in activation barriers for boundary diffusion that attend segregation. Furthermore, microstructural models reflect the interplay among transport and mechanical properties during creep. Finally, from our results, we have developed several doping strategies i.e., selective codoping to enhance creep resistance.

Subject Categories:

  • Inorganic Chemistry
  • Metallurgy and Metallography
  • Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE