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152 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1973

Thesis (M.S.)--Virginia Polytechnic Institute. / Also available via the Internet.

Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1973.

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Thesis (M.S.)--Rochester Institute of Technology, 1995. / Typescript. Bibliography: leaf 54.

The nature of diffusion along thin evaporated films has been studied by optical and transmission electron microscopy. The thicknesses of the films were measured by multiple-beam interferometry. A preliminary survey of some 22 binary metal systems showed that only four - Ag-Se, Cu-Se, Cu-Te, and Ag-Te - diffused measurably at room temperature. In these four systems it was found possible to study only the diffusion of Cu or Ag into Se and Te; the reverse diffusion experiments failed, presumably because of extensive Kirkendall porosity which developed on the Se or Te side of the diffusion couples, impeding the motion of these atoms. The room temperature growth rates in each system were observed to be higher when the structure of the Se or Te consisted of isolated islands with a highly disordered inter-island network. This effect was attributed to a short circuit diffusion process analogous to grain boundary diffusion which took place in the inter-island channels. The effect was more pronounced in Cu-Te and Ag-Te where electron microscopy observations of the phase boundary interfaces showed a marked tendency for grain boundary diffusion to occur at all Se and Te thicknesses. For continuous films of Se and Te, the growth rates were found to be independent of the absolute thickness. Because of the evaporation geometry used in depositing the couples, there was a critical thickness ratio of Ag or Cu to Se or Te that had to be exceeded in order for diffusion to proceed. Theoretical treatment of the problem, based on the stoichiometry of the phases formed during diffusion, gave predictions of the critical ratio that were generally in good agreement with the experimental values obtained. In each system the critical ratio was found to be independent of the absolute Se or Te thickness. It was also possible to predict the composition of the phase formed during diffusion using the critical ratio. In every system but Cu-Te, the composition determined in this way was in agreement with that given by electron diffraction analysis of the diffusion zone. The activation energies for diffusion in Ag-Se, Cu-Te, and Ag-Te were fairly low suggesting that short circuit diffusion was the predominant mechanism in these systems. The activation energy in Cu-Se was quite large (23 kcal/mole), and it appears that the diffusion mechanism in this case is not consistent with that in the other systems. An interesting observation made during electron microscopy studies in Cu-Se was the formation of a second phase when high electron beam intensities were used. This phase (Cu₃Se₂), not observed in normal diffusion experiments up to 5 0°C, grew dendritically in the presence of the electron beam. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

This theoretical study has been undertaken in order to provide insights into the steady two-dimensional laminar film condensation heat transfer on an isothermal vertical flat wall and a cylindrical surface. Condensation is given to both the pure water vapor and water vapor-air mixture. Only the saturated state of the bulk vapor is considered. The effects of liquid-vapor resistance, gas-solubility in the condensate, thermal diffusion and diffusion thermo are neglected. The presence of air as non-condensing gas has been fully accounted for in this study. The physical properties of the condensate liquid are taken to be those of saturated water at the appropriate temperature. The properties of the vapor region are considered to be constant except for the density of the mixture. The method of solution is based on the numerical techniques of laminar boundary layer theory. By using liquid-vapor interface matching, an approximate integral solution is obtained. In this study, it was found that the presence of a small amount of air as a non-condensing gas in the water vapor-air mixture plays a decisive role in decreasing the condensation heat transfer. The decrease is more pronounced at lower bulk temperature, TV, and higher values of (TV-TW). As the mass fraction of air in the bulk, W∞, increases, the heat transfer decreases monotonically.