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Nucleation mechanisms in chemically vapor-deposited mullite coatings on SiC

Published online by Cambridge University Press:  31 January 2011

Ping Hou ,
S. N. Basu  and
V. K. Sarin
Ping Hou
Affiliation:
Department of Manufacturing Engineering, Boston University, 15 St. Mary's Street, Boston, Massachusetts 02215
S. N. Basu*
Affiliation:
Department of Manufacturing Engineering, Boston University, 15 St. Mary's Street, Boston, Massachusetts 02215
V. K. Sarin
Affiliation:
Department of Manufacturing Engineering, Boston University, 15 St. Mary's Street, Boston, Massachusetts 02215
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

Dense, uniform, and adherent chemically vapor-deposited mullite coatings were deposited on SiC substrates using the AlCl3–SiCl4–H2–CO2 system. Typical coating morphology consisted of a thin interfacial layer of γ–Al2O3 nanocrystallites embedded within a vitreous SiO2-based matrix. When a critical Al/Si ratio of 3.2 ± 0.29 was reached within this nanocrystalline layer, mullite crystals nucleated and grew as columnar grains. The thickness of the nanocrystalline layer decreased as the input AlCl3/SiCl4 ratio was increased. In all cases, the Al/Si composition in the coating increased from the coating/substrate interface to the coating surface. Critical factors leading to the nucleation and growth of mullite crystals are discussed in this article.

Type
Articles
Information
Journal of Materials Research , Volume 14 , Issue 7 , July 1999 , pp. 2952 - 2958
Copyright
Copyright © Materials Research Society 1999

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References

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