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Proceedings Paper

Directional solidification of mercury cadmium telluride during the second United States microgravity payload mission (USMP-2)
Author(s): Donald C. Gillies; Sandor L. Lehoczky; Frank R. Szofran; Dale A. Watring; Helga A. Alexander; Gregory A. Jerman
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Paper Abstract

As a solid solution semiconductor having a large separation between liquidus and solidus, mercury cadmium telluride (MCT) presents a formidable challenge to crystal growers desiring an alloy of high compositional uniformity. To avoid constitutional supercooling during Bridgman crystal growth it is necessary to solidify slowly in a high temperature gradient region. The necessary translation rate of less than 1mm/hr results in a situation where fluid flow induced by gravity on earth is a significant factor in material transport. The advanced automated directional solidification furnace (AADSF) is equipped to provide the stable thermal environment with a high gradient, and the required slow translation rate needed. Ground based experiments in AADSF show clearly the dominance of flow driven transport. The first flight of AADSF in low gravity on USMP-2 provided an opportunity to test theories of fluid flow in MCT and showed several solidification regimes which are very different from those observed on earth. Residual acceleration vectors in the orbiter during the mission were measured by the orbital acceleration research experiment, and correlated well with observed compositional differences in the samples.

Paper Details

Date Published: 12 July 1996
PDF: 10 pages
Proc. SPIE 2809, Space Processing of Materials, (12 July 1996); doi: 10.1117/12.244326
Show Author Affiliations
Donald C. Gillies, NASA Marshall Space Flight Ctr. (United States)
Sandor L. Lehoczky, NASA Marshall Space Flight Ctr. (United States)
Frank R. Szofran, NASA Marshall Space Flight Ctr. (United States)
Dale A. Watring, NASA Marshall Space Flight Ctr. (United States)
Helga A. Alexander, Universities Space Research Association (United States)
Gregory A. Jerman, NASA Marshall Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 2809:
Space Processing of Materials
Narayanan Ramachandran, Editor(s)

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