Title: Analysis of crystal growth of high temperature materials in a plasma furnace
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00097882/00001
 Material Information
Title: Analysis of crystal growth of high temperature materials in a plasma furnace
Physical Description: xiv, 138 l. : illus. ; 28 cm.
Language: English
Creator: Smith, William Austin, 1927- ( Dissertant )
Williams, D. T. ( Thesis advisor )
Farber, E. A. ( Reviewer )
Smith, W. O. ( Reviewer )
Clarkson, M. H. ( Reviewer )
Millsaps, K. T. ( Reviewer )
Myers, O. E. ( Reviewer )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 1966
Copyright Date: 1966
Subjects / Keywords: Crystal growth   ( lcsh )
Plasma (Ionized gases)   ( lcsh )
Heat engineering   ( lcsh )
Aerospace Engineering thesis Ph. D
Dissertations, Academic -- Aerospace Engineering -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
theses   ( marcgt )
Abstract: The increased understanding of electron behavior in solids has stimulated research into developing ways of growing specialized crystals having electrical properties particularly suited to a given application. One special field of interest is in crystals of refractory materials for use in applications where high temperatures are either encountered or desired. One such case is that of the thermoelements located directly in the core of a nuclear reactor. This dissertation contains an analysis of the crystal growth mechanism of refractory materials taking place in the fireball of a plasma-heated Verneuil- type furnace. The fireball temperature is estimated at well over 9,000 K. On the basis of this analysis predictions can be made for properly adjusting the furnace environment to one that is conducive to the growth of high quality, single crystals of various refractory materials. Such parameters as the powder feed rate, thermal gradient at the liquid-solid interface, rf power level, powder grain size, geometry of the boule tip with respect to the powder probe and fireball, powder-gas flow rate and the presence of a diatomic gas are investigated and their effects on crystal growth and quality are determined. It was found that the large radiation heat loss from the side of the boule dominates the thermal conditions during crystal growth. When the rf power is low, the boule is cool and the thermal gradients are large. As the boule increases in length, the rf power must be boosted in order to maintain a molten cap. If the power were not boosted the molten cap would eventually vanish as the boule grew longer, at which point all growth would stop. The large radiant heat losses from the side of the boule are not always as important as was found in the case of growing aluminum oxide crystals. If materials of a lower melting point are involved, radiation losses become less important. If materials of higher melting points are involved, clearly the importance of the radiation losses becomes much more critical. The importance of a diatomic gas as a means of heat transfer to the boule was an interesting observation. The use of such gases is not, of course, original with this work. On the other hand, the dramatic increase in the heat transfer rate from the plasma when diatomic gases are used constitutes an important improvement in this application. The effect of loss of heat due to the introduction of fine powder grains into the plasma is another observation not originally anticipated. The study here clarifies and rationalizes the observations. It was further found that the parameters- important to crystal quality are the ratio of the thermal gradient at the liquid-solid- interface to the powder feed rate and the average temperature of the molten cap. Crystal quality was generally better at the periphery than at the core of a boule. It is concluded that the work reported on contributes to a more effective use of the plasma-Verneuil furnace in growing crystals of refractory materials.
Thesis: Thesis--University of Florida.
Bibliography: Bibliography: l. 134-136.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
 Record Information
Bibliographic ID: UF00097882
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000423885
oclc - 11023088
notis - ACH2290


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