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The Effect of Structure on the Thermal Conductivity of Plasma Sprayed Alumina

Published online by Cambridge University Press:  15 February 2011

H.C. Fiedler
H.C. Fiedler*
Affiliation:
Metallurgy Laboratory, General Electric Company, Corporate Research and Development, Schenectady, New York 12301
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Abstract

Plasma sprayed deposits of alumina are normally of the metastable gamma phase, which transforms to alpha upon heating to an elevated temperature. The poor thermal conductivity of gamma phase is improved by transforming to alpha, but the improvement is restricted by the fragmented nature of the structure, a consequence of alpha being a denser phase than gamma.

Alpha phase has been reported to form when deposits are made on preheated substrates. It was found that reducing the distance between gun and deposition surface, thereby raising the temperature of the latter, resulted in transforming gamma to alpha, and as the temperature continued to rise, alpha formed directly from the liquid. The thermal conductivity of alpha formed directly from the liquid is 0.27 Watt/cm K at 323 K, which approaches the thermal conductivity given for 99.5% pure, 98% dense, polycrystalline alpha alumina.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 30: Symposium L – Plasma Processing and Synthesis of Materials I , 1983 , 173
Copyright
Copyright © Materials Research Society 1984

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References

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