Accession Number:

ADA371595

Title:

The Synthesis, Processing, Deformation and Failure of Superplastic Nanocrystalline Ceramic Composites

Descriptive Note:

Final rept. 1 Dec 95-30 Nov 97

Corporate Author:

INDIAN INST OF SCIENCE BANGALORE

Personal Author(s):

Report Date:

1999-12-14

Pagination or Media Count:

23.0

Abstract:

Commercially available nanocrystalline 3 mol yttria stabilized tetragonal zirconia powders with a crystallite size of 40 nm were processed using a colloidal technique. Essentially, the powders were dispersed in de-ionized water, and the pH of the solution was adjusted to approx. 2 to disperse the powders. The solution was ultrasonicated and then pressure filtered to produce a green body with a relative density of approx. 50. The densification and grain growth characteristics of zirconia were examined during the free sintering and sinter-forging sintering with the application of a compressive uniaxial stress without any lateral constraints at temperatures in the range of approx. 1600 to 1750 K. It was demonstrated that it is possible to produce fully dense compacts with a grain size of approx. 175 nm using this technique. During sinter-forging, both densification and creep processes occur simultaneously the measurement of density and axial strain enable to separation of the kinetics of the two processes. It was shown that deformation during densification occurs by an identical process as in fully dense materials mainly grain boundary sliding. Furthermore, the differences in the stress exponents for creep and densification indicated that densification was not controlled directly by deformation.

Subject Categories:

  • Ceramics, Refractories and Glass

Distribution Statement:

APPROVED FOR PUBLIC RELEASE