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Ceramics in the System NbB2 – CrB2

Published online by Cambridge University Press:  15 February 2011

I. G. Talmy ,
E. J. Wuchina ,
J. A. Zaykoski  and
M. M. Opeka
I. G. Talmy
Affiliation:
Naval Surface Warfare Center, 10901 New Hampshire Avenue, Silver Spring, MD 20903-5640
E. J. Wuchina
Affiliation:
Naval Surface Warfare Center, 10901 New Hampshire Avenue, Silver Spring, MD 20903-5640
J. A. Zaykoski
Affiliation:
Naval Surface Warfare Center, 10901 New Hampshire Avenue, Silver Spring, MD 20903-5640
M. M. Opeka
Affiliation:
Naval Surface Warfare Center, 10901 New Hampshire Avenue, Silver Spring, MD 20903-5640
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Abstract

Phase equilibria and properties of ceramics in the NbB2 – CrB2 system were studied. Continuous solid solutions were found showing high activation energy (96 kcal'mol) of formation which is due to large disparity of atomic radii between Cr and Nb. Pure NbB2 and CrB2 ceramics were prepared by hot pressing at 2100 and 1800°C, respectively, at 20 MPa for 0.5 hour. Both materials exhibited closed porosity which was eliminated by the addition of Al2O3 and SiC. Thermogravimetric studies showed different mechanisms of oxidation of the diborides. The presence of Al2O3 and SiC improved the oxidation resistance, hardness, and fracture toughness of CrB2 ceramics. The additives increased the hardness of NbB2 ceramics but did not significantly affect their toughness.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 365: Symposium M – Ceramic Matrix Composites–Advanced High-Temperature Structural Materials , 1994 , 81
Copyright
Copyright © Materials Research Society 1995

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