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The low temperature hexagonal to orthorhombic transformation in Si3N4 reinforced BAS matrix composites

Published online by Cambridge University Press:  03 March 2011

A. Bandyopadhyay
Affiliation:
Department of Mechanical and Aerospace Engineering and Materials Science and Engineering Program. University of Texas at Arlington, Arlington, Texas 76019-0031
P.B. Aswath
Affiliation:
Department of Mechanical and Aerospace Engineering and Materials Science and Engineering Program. University of Texas at Arlington, Arlington, Texas 76019-0031
W.D. Porter
Affiliation:
High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6064
O.B. Cavin
Affiliation:
High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6064
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Abstract

The amount of Si3N4 in a Si3N4-BaO · Al2O3 · 2SiO2 (BAS) composite and the time of sintering was examined in the context of the low temperature hexagonal to orthorhombic transformation in BAS. It was found that with increasing amounts of Si3N4 in the composite, the temperature of the hexagonal to orthorhombic transformation was decreased. As the sintering time was increased for a given composite composition, a drop in the temperature of the hexagonal to orthorhombic transformation was observed. which was linked to an increase in the β-Si3N4 content in the composite. In addition, as the Si3N4 content in the composite was increased, a resultant drop in the coefficient of thermal expansion of the composite occurred. The extent of the linear dimensional change of the composite during the BAS hexagonal to orthorhombic transformation is reported.

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Articles
Copyright
Copyright © Materials Research Society 1995

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References

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