Thesis (M.S.)--Mississippi State University. Department of Agricultural and Biological Engineering. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Agricultural and Biological Engineering. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Michigan, 1979.

Thesis (doctoral)--Georg-August-Universität zu Göttingen, 1933.

Thesis (doctoral)--Georg-August-Universität zu Göttingen, 1933.

<p>This investigation is primarily concerned with the development of a suitable high-precision sectioning technique to be employed in studies of depth distributions of energetic ions in Mo and V. It consists of two main parts.</p> <p>In the first part, uniform anodic oxide films of controlled thicknesses have been grown on poiycrystalline V, Mo, and W (the latter, primarily for comparison with earlier works on W) in acetic acid-sodium tetraborate solutions containing small quantities of water. These anodic films which show bright characteristic interference colours when formed at >10 volts, are shown to be rapidly soluble in a dilute solution of KOH whereas the underlying metal is attacked at a rate of less than ~100Å per day. The thickness of the anodic films per volt has been established using ellipsometry and conventional weight-loss measurements.</p> <p>Kinetics of anodization have been studied at constant-current and constant-voltage. An analysis of these data shows the composition of the films on Mo and W to be close to Mo0₃ and W0₃ respectively while those on V were intermediate between V₂0₄ and V₂0₅. The density of the films on Mo and the differential field strength, E_d, for films on Mo and W have also been determined.</p> <p>In the second part, a theoretical background consisting of an outline of the theory of Lindhard, Scharff and Schiøtt, has been provided; in the absence of experimental data, this theory is generally used to estimate the depth distribution of ions in amorphous targets. Experimental range profiles have been determined for 5-30 keV Kr⁸⁵ in polycrystalline Mo using the technique developed in the first part and the results obtained show a large discrepancy when compared with Lindhard theory. The extent of disagreement with theory is similar to that obtained by previous workers with targets such as Al or W.</p> <p>Evidence is presented to show that this large discrepancy may be attributted to crystal-lattice effects (i.e. channelling). For example, it is shown that the discrpency is not due to the anodizing-stripping sequence being sensitive to bombardment. Also, it is demonstrated that the Mo used had a pronounced preferred orientation such that the open directiors <100>, <211>, and <111> were normal to the surface.</p> <p>An important part of future work will be to extend techniques such as those described here to the metal Be, for Be is the lightest target material that can be conveniently worked with.</p> / Master of Science (MS)

<p> The stress relieving mechanisms in two different batches of thermal-shock resistant calcia-PSZ have been investigated. The nature of the stress relief in the two materials appears to result from the transformation of the pure ZrO₂ component of the microstructure at temperatures below, within, and above the normal transformation temperature range. In the batch #1 material, which contains a larger volume fraction of monoclinic phase, the cubic matrix material behaves in a "brittle" fashion resulting in the production of a high density of microcracks in the body. The density of these cracks is such that the level of energy that can be stored in the body is limited and thermal shock resistance results. The batch #2 material contains considerably less monoclinic material and the evidence suggests that the cubic matrix within it can act in a ductile fashion. This ductility together with the twinning of the monoclinic component of the microstructure possibly relieves the stresses developed in the material on thermal shock. </p> <p> In the batch #2 material, large platelets were observed to develop following thermal cycling from temperatures above those of the normal transformation. It has been demonstrated that stress plays a major role in the development of these features. In view of the possible ductility of the cubic matrix in this material it is suggested that the thermal cycling "works" the material, texturing the pure zirconia component in it, so leading to the development of the observed platelets. </p> / Thesis / Master of Engineering (ME)

<p> The Fe-C-Mn phase diagram has been calculated from thermodynamic data. Experimentally determined tie-lines are in good agreement with the calculated diagram. </p> <p> It has been shown that the assumption that the austenite-ferrite interface is in a local equilibrium condition during the late stages of the transformation in highly supersaturated alloys and at all times in alloys in an area of low supersaturation is justified. The approximate solution to the diffusion equations correctly predicts the experimentally determined manganese concentration profiles. </p> <p> Hillert's concept of paraequilibrium has been examined and explicitly defined. The concentration given by a paraequilibrium calculation correctly predicts the experimentally observed growth rates of Kinsman and Aaronson (1967) for very highly supersaturated alloys. </p> <p> A convolution technique for use in the interpretation of strongly localized concentration changes determined by electron beam microanalysis has been developed. </p> / Thesis / Doctor of Philosophy (PhD)