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Residual Gases in Crystal Growth SystemsResidual gases present in closed ampoules may affect different crystal growth processes. That seems to be particularly true under microgravity conditions where, due to weightlessness of the melt, the gases may lead to detached solidification and/or formation of voids and bubbles, as observed in the past. For that reason a good understanding and control of formation of residual gases is important for an optimum design and meaningful interpretation of crystal growth experiments. Our extensive experimental and theoretical studies of the subject, summarized in this paper, include degassing of silica glass and generation of gases from different source materials. Different materials processing conditions, like outgassing under vacuum, annealing in hydrogen, resublimation, different material preparation procedures, multiple annealings, different processing times, and others were applied and their effect on the amount and composition of gas were analyzed. The experimental results were interpreted based on theoretical calculations on diffusion in silica glass and source materials and thermochemistry of the system. Procedures for a reduction of the amount of gas are also discussed.
Document ID
20030106652
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Palosz, W.
(Universities Space Research Association Huntsville, AL, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Solid-State Physics
Meeting Information
Meeting: CI Microgravity Transport Processes in Fluid, Thermal, Biological, and Materials Sciences Conference III
Location: Davos
Country: Switzerland
Start Date: September 14, 2003
End Date: September 19, 2003
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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