The thermomigration of Au195 and Sb125 in gold and Ni59 in nickel
Mock, Willis
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Permalink
https://hdl.handle.net/2142/25751
Description
Title
The thermomigration of Au195 and Sb125 in gold and Ni59 in nickel
Author(s)
Mock, Willis
Issue Date
1968
Doctoral Committee Chair(s)
Lazarus, David
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
thermomigration
gold
nickel
large thermal gradients
mass transport
Language
en
Abstract
The effect of large thermal gradients on the mass transport of
Au195 and Sb
125
in gold and Ni59 in nickel has been investigated. Specimens
in the form of rods containing two welded interfaces separated by
l/8-inch were fabricated. Each interface contained a layer of the appropriate tracer an an inert radioactive Hf181O2 marker. The specimens
were annealed in a vacuum furnace which provided a temperature gradient
of approximately 300°C/cm. The radioactive penetration profiles at the
hot and cold interfaces were determined experimentally by sectioning the
specimen on a lathe and assaying the radioactivity in each section. The
penetration profiles, which were skewed gaussians, were curve fit by the
method of least squares. The temperature at each interface and the temperature
gradient were determined from the measured D values and the
known tracer self-diffusion coefficient.
During the temperature gradient anneal the maximum of the tracer
profile at the hot interface shifted with respect to the Hf18l02 marker.
Using the measured shift values, the heat of transport of Au
195
in gold
was measured to be Q*Au = 0.80 ± 0.27 eV. This value supports Huntingtods
theory of the thermomigration of solvent atoms in single band metals.
The theory predicts that the static temperature gradient contribution to
the heat of transport is approximately equal to the atomic migration
energy and is two orders of magnitude larger than the thermoelectric
field and charge carrier-ion interaction effects.
The heat of transport of Ni59 in nickel was estimated to be
Q*Ni = 1.3 ± 7.2 eV. Because the measured value for the shift was within
the experimental error, a large uncertainty in Q*Ni resulted. It is
therefore not possible to draw conclusions concerning the magnitude of
the charge carrier-ion interaction.
The experimentally determined value of the Sb
125
heat of transport
in gold was found to be Q*Sb = -2.02 ± 0.23 eV. According to Gerl's
theory for dilute impurity thermomigration, this. large negative number
indicates that the charge carrier-impurity ion interaction is the dominant
driving force for Sb125 impurity thermomigration in gold, because
the cold electrons moving up the temperature gradient impare more momentum
to the impurity atom than the hot electrons moving down the temperature
gradient. Q*Sb compares favorably with the theoretically calculated
value for the heat carrier-impurity ion interaction of Q* = -0.5 eV for
antimony thermomigration in silver.
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