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Optimization of chemical vapor infiltration with simultaneous powder formationa)

Published online by Cambridge University Press:  31 January 2011

A. Ditkowski ,
D. Gottlieb  and
B. W. Sheldon
A. Ditkowski
Affiliation:
Division of Applied Mathematics, Brown University, Providence, Rhode Island 02912
D. Gottlieb
Affiliation:
Division of Applied Mathematics, Brown University, Providence, Rhode Island 02912
B. W. Sheldon
Affiliation:
Division of Engineering, Brown University, Providence, Rhode Island, 02912
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Abstract

A key difficulty in isothermal, isobaric chemical vapor infiltration is the long processing times that are typically required. With this in mind, it was important to minimize infiltration times. This optimization problem was addressed here, using a relatively simple model for dilute gases. The results provided useful asymptotic expressions for the minimum time and corresponding conditions. These approximations were quantitatively accurate for most cases of interest, where relatively uniform infiltration was required. They also provided useful quantitative insight in cases where less uniformity was required. The effects of homogeneous nucleation were also investigated. This does not effect the governing equations for infiltration of a porous body; however, powder formation can restrict the range of permissible infiltration conditions. This was analyzed for the case of carbon infiltration from methane.

Type
Articles
Information
Journal of Materials Research , Volume 15 , Issue 12 , December 2000 , pp. 2695 - 2705
Copyright
Copyright © Materials Research Society 2000

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