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Stability of Boron Nitride Coatings on Ceramic Substrates

Published online by Cambridge University Press:  28 February 2011

Abhaya K. Datye ,
Xiaomei Qui ,
Theodore T. Borek ,
Robert T. Paine  and
Lawrence F. Allard
Abhaya K. Datye
Affiliation:
Center for Microengineered Ceramics, University of New Mexico, Albuquerque, NM 87131.
Xiaomei Qui
Affiliation:
Center for Microengineered Ceramics, University of New Mexico, Albuquerque, NM 87131.
Theodore T. Borek
Affiliation:
Center for Microengineered Ceramics, University of New Mexico, Albuquerque, NM 87131.
Robert T. Paine
Affiliation:
Center for Microengineered Ceramics, University of New Mexico, Albuquerque, NM 87131.
Lawrence F. Allard
Affiliation:
High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, TN 37831.
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Abstract

When BN is synthesized via polymeric precursors and applied to ceramic substrates, tough adherent coatings of hexagonal-BN (h-BN) are obtained after annealing at 1200°C in N2. The study of these coatings is facilitated by using nonporous oxide powders containing single crystal particles of submicron size (e.g. cubes of MgO) as model ceramic substrates. These oxide powders permit high resolution TEM examination of the BN coatings with no further sample preparation. In this study, samples of BN/MgO cubes containing 50 wt% BN were heated in air at elevated temperatures for 16 hours to study the oxidation resistance of BN coatings. The BN coating was found to be stable at 600°C, but the 700°C-treated sample showed evidence for partial amorphization of the coating and reaction with MgO. A significant fraction of the MgO in the 800°C-treated sample had transformed to Mg2B2O5. The reaction of MgO with the BN coating under oxidizing ambients leads to loss of the cubic morphology in the precursor powder.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 180: Symposium A – Better Ceramics Through Chemistry IV , 1990 , 807
Copyright
Copyright © Materials Research Society 1990

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References

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