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Compositionally graded mullite-based chemical vapor deposited coatings

Published online by Cambridge University Press:  31 January 2011

Tushar Kulkarni ,
H.Z. Wang ,
S.N. Basu  and
V.K. Sarin
Tushar Kulkarni*
Affiliation:
Division of Materials Science and Engineering, Boston University, Brookline, Massachusetts 02446
H.Z. Wang
Affiliation:
Division of Materials Science and Engineering, Boston University, Brookline, Massachusetts 02446; and Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467
V.K. Sarin
Affiliation:
Division of Materials Science and Engineering, Boston University, Brookline, Massachusetts 02446; and Department of Mechanical Engineering, Boston University, Boston, Massachusetts 02215
*
a) Address all correspondence to this author. e-mail: tushark@bu.edu
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Abstract

Dense, crystalline mullite (3Al2O3ċ2SiO2) coatings have been deposited by chemical vapor deposition on Si-based substrates using the AlCl3–SiCl4–CO2–H2 system. A graded coating composition has been achieved in the coatings, with the Al/Si ratio being stoichiometric (∼3) at the coating/substrate interface, and increasing monotonically toward the outer coating surface. The highest reported Al-rich mullite has been deposited in the process. At high Al/Si ratios, the mullite structure breaks down and an aluminosilicate phase similar to the metastable δ* Al2O3 is nucleated. Experimental evidence is presented in this study that this phase has some Si-incorporation in it and has been called δ*(Si)Al2O3. Like the other known aluminosilicates, δ*(Si)Al2O3 converts to mullite on heating at elevated temperatures.

Keywords

CeramicChemical vapor deposition (CVD) (deposition)Coating
Type
Articles
Information
Journal of Materials Research , Volume 24 , Issue 2 , February 2009 , pp. 470 - 474
Copyright
Copyright © Materials Research Society 2009

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References

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