Surface tension anisotropy of succinonitrile and pivalic acid: New measurements and comparison with microscopic solvability theory.
Item
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Title
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Surface tension anisotropy of succinonitrile and pivalic acid: New measurements and comparison with microscopic solvability theory.
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Identifier
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AAI9224842
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identifier
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9224842
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Creator
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Muschol, Martin.
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Contributor
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Adviser: Herman Z. Cummins
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Date
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1992
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physics, Condensed Matter
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Abstract
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Careful determinations of the surface tension anisotropy parameter {dollar}\varepsilon\sb4{dollar} for succinonitrile (SCN), pivalic acid (PVA) and a PVA/1% ethanol mixture are reported. The size of the higher harmonic {dollar}\varepsilon\sb8{dollar} is estimated. Our measurements are based on the observations of equilibrium shapes of isolated, single crystals in contact with their melts. The influence of thermal gradients on the measurements as well as orientation effects are analyzed in detail. Numerical interpolation routines, previously employed by Dougherty and Gollub, are utilized to enhance the optical resolution in our experiments. The anisotropy values found for SCN, PVA and PVA/1% ethanol are {dollar}\varepsilon\sb4{dollar} = 0.0055 {dollar}\pm{dollar} 0.0015, 0.025 {dollar}\pm{dollar} 0.002, and 0.026 {dollar}\pm{dollar} 0.002 respectively. From these values, the selection parameter {dollar}\sigma\sp*\sb{lcub}\rm th{rcub}{dollar} predicted by microscopic solvability theory for the three-dimensional axisymmetric case was computed and compared to the {dollar}\sigma\sp*\sb{lcub}\rm exp{rcub}{dollar} values determined directly from previous dendritic growth experiments. We find that {dollar}\sigma\sp*\sb{lcub}\rm th{rcub}/\sigma\sp*\sb{lcub}\rm exp{rcub}{dollar} is 0.56 {dollar}\pm{dollar} 0.2 for SCN and 2.14 {dollar}\pm{dollar} 0.5 for PVA. Possible sources for these discrepancies are discussed.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
