Compositionally graded mullite-based chemical vapor deposited coatings

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 inte...

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Bibliographic Details
Published in:Journal of materials research 2009-02, Vol.24 (2), p.470-474
Main Authors: Kulkarni, Tushar, Wang, H.Z., Basu, S.N., Sarin, V.K.
Format: Article
Language:English
Subjects:
Applied and Technical Physics
Biomaterials
Ceramic
Chemical vapor deposition (CVD) (deposition)
Coating
Inorganic Chemistry
Materials Engineering
Materials Science
Nanotechnology
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Summary: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.
ISSN:0884-2914
2044-5326
DOI:10.1557/JMR.2009.0062