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Effects of buoyancy-driven flow and thermal boundary conditions on physical vapor transportA 2D numerical model was developed in order to ascertain if reduced gravity conditions are beneficial to physical vapor transport (PVT) and to determine its tolerance limits to residual accelerations. This was solved using the PHOENICS finite-volume code. Reduction of gravitational accelerations to less than 0.1 g0 was found to be sufficient to suppress buoyancy-driven convection to an extent that diffusion was the dominant transport mode, whence a greater uniformity in the growth rate could be obtained. It is shown that a uniform temperature gradient on the ampoule walls causes the vapor to be supersaturated throughout the ampoule, potentially resulting in undesirable nucleation at the walls. A 'hump' in the wall temperature profile can be used to avoid this. The prevailing transport conditions determine the size of the hump needed.
Document ID
19920048985
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Nadarajah, Arunan
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Rosenberger, Franz
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Alexander, J. I. D.
(Alabama, University Huntsville, United States)
Date Acquired
August 15, 2013
Publication Date
March 1, 1992
Publication Information
Publication: Journal of Crystal Growth
Volume: 118
ISSN: 0022-0248
Subject Category
Materials Processing
Accession Number
92A31609
Funding Number(s)
CONTRACT_GRANT: NAG8-684
Distribution Limits
Public
Copyright
Other

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