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Sintering and Deformation of Nanocrystalline Ceramics

Published online by Cambridge University Press:  28 February 2011

H. Hahn ,
R. S. Averback ,
H. J. Hofler  and
J. Logas
H. Hahn
Affiliation:
Department of Mechanics and Materials Science, Rutgers University, P.O.Box 909, Piscataway, NJ 08909 Department of Materials Science and Engineering, University of Illinois, 1304 W. Green Street, Urbana, IL 61801
R. S. Averback
Affiliation:
Department of Materials Science and Engineering, University of Illinois, 1304 W. Green Street, Urbana, IL 61801
H. J. Hofler
Affiliation:
Department of Materials Science and Engineering, University of Illinois, 1304 W. Green Street, Urbana, IL 61801
J. Logas
Affiliation:
Department of Materials Science and Engineering, University of Illinois, 1304 W. Green Street, Urbana, IL 61801 department of Engineering and Composite Science, Winona State University, Winona, MN
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Abstract

Nanocrystalline ceramics have been produced by the method of inert gas condensation of ultra-small particles and in situ consolidation. Sintering characteristics and microstructural parameter such as grain size, porosity and pore size distributions have been investigated by a variety of techniques, including: X-ray diffraction, gravimetry, nitrogen adsorption, scanning electron microscopy and small angle neutron scattering. In pure TiO2, the sintering temperatures are drastically lowered compared to conventional ceramics, however, extensive grain growth occurs before full densification is achieved. High density, nanocrystalline ceramics can be prepared by pressure assisted sintering, doping and additions of second phases. High temperature microhardness and creep deformation in compression were measured and it was found that creep processes occur at lower temperatures than in ceramics with larger grain sizes. Nanocrystalline TiO2 with densities > 99 % can be deformed plastically without fracture at temperatures below half the melting point. The total strains exceed 0.6 at strain rates as high as 10−3 s−1. The stress exponent of the strain rate, n, is approximately 3 and the grain size dependence is G-q with q in the range of 1 – 1.5. It is concluded that the creep deformation occurs by an interface reaction controlled mechanism.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 206: Symposium G – Clusters and Cluster-Assembled Materials , 1990 , 569
Copyright
Copyright © Materials Research Society 1991

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References

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