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Phase Separation in Alumina-Chromia

Published online by Cambridge University Press:  01 February 2011

M. S. McIntosh ,
T. H. Sanders Jr  and
J. M. Hampikian
M. S. McIntosh
Affiliation:
School of Materials Science and Engineering Georgia Institute of Technology Atlanta, Georgia 30332-0245
T. H. Sanders Jr
Affiliation:
School of Materials Science and Engineering Georgia Institute of Technology Atlanta, Georgia 30332-0245
J. M. Hampikian
Affiliation:
School of Materials Science and Engineering Georgia Institute of Technology Atlanta, Georgia 30332-0245
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Abstract

The alumina-chromia system shows complete mutual solubility and is represented by an isomorphous phase diagram. However, the alumina-chromia system exhibits an asymmetric miscibility gap under 1300°C. Using existing data from the literature, the alumina-chromia system was assessed using thermodynamic modeling by Kim and Sanders [1]. Regular and subregular solution models for the liquid and solid phases were used to define the phase boundaries for the miscibility gap in this system. Using this thermodynamic representation of the miscibility gap to select temperatures of interest, 75 mole percent Al2O3samples were synthesized via combustion of powders, followed by pressing into pellets and heat-treated for various times and temperatures. Both X-ray and TEM analysis showed evidence of spinodal decomposition after heat-treatment. X-ray analysis showed that decreasing the heat-treatment temperature increases the compositional difference between the phases present. The experimentally observed microstructures exhibit lamella-like structures that vary in spacing from 8nm to 3nm as the heat-treatment temperature varies from 400°C to 800°C.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 731: Symposium W – Modeling and Numerical Simulation of Materials Behavior and Evolution , 2002 , W8.7
Copyright
Copyright © Materials Research Society 2002

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