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Title:The thermomigration of Au195 and Sb125 in gold and Ni59 in nickel
Author(s):Mock, Willis
Doctoral Committee Chair(s):Lazarus, David
Department / Program:Physics
large thermal gradients
mass transport
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.
Issue Date:1968
Genre:Dissertation / Thesis
Rights Information:1968 Willis Mock, Jr.
Date Available in IDEALS:2011-07-11
Identifier in Online Catalog:6085755

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