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In the present investigation, measurements were made at liquid-helium temperatures on single-crystal bismuth samples which had a stair-step geometry in order to study several thicknesses during one helium run. These samples were also thinned to extend the thickness range of the steps to a thinner region. In addition J.E. Parrott's theory is extended to include a diagonal anisotropic relaxation-time tensor and the effect of holes on the size effect. A discussion of the theory of Parrott, and the extension of Parrott's theory in connection with the experimental results is presented.

Bismuth(III) has been used in the medicinal industry for many years, but its mechanism of action is not fully understood and there is very little information on thermodynamic and kinetic parameters for complex formation. Amino acids are the building blocks of life and so, by initially simply determining the complexing ability of various amino acids with bismuth, an indication of how bismuth could interact in the body can slowly be developed and could assist in the eventual development and design of more effective bismuth containing drugs.

Bulk and thin film samples of Bi₂₋[subscript x]Pb[subscript x]Sr₂Ca₂Cu₃O[subscript y] compounds were prepared by suitable methods. The thin film and bulk samples were exposed to argon gas at temperatures of about 2000 °C and pressures of about 300 atm. in a ballistic compressor (BC) and then cooled at a rate of about 10⁵ °C/sec. The samples before and after this treatment were examined and compared using a transmission electron microscope (TEM), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS) , and an x-ray diffractometer (XRD). Resistance and magnetic susceptibility measurements were made to determine changes in superconducting temperature Tc. Resistance and AC susceptibility measurements of bulk and thin film samples demonstrated that the Tc increased 3- 6 K after the BC treatment, and step-shaped curves were often observed in the resistance versus temperature graphs. The x-ray diffraction study revealed that the relative intensities of lines of the two high Tc phases clearly increased, and the relative intensities of lines of the low Tc phase decreased after the BC treatment. Scanning electron micrographs of the exposed samples showed that surface melting had occurred, and the BC treatment affected the surface of samples to a depth of about 10 μm. Energy dispersive spectral analysis showed that oxygen loss occurred in the exposure process. Transmission electron diffraction patterns showed that the crystal structure of the Bi-based compounds have an incommensurate modulation along the b-axis with different periods of 25.4 Å, 38.7 Å and 72.6 Å. After the BC treatment, the lattice parameters of superconductors did not change, but the relative intensities of spots changed, the modulation of 72.6 Å disappeared, and the density of twist boundaries increased. These observations suggest that the treatment changed the density of structural defects and the atomic arrangement. These studies tentatively indicate that the increase in structural defects was caused by oxygen loss. A very small oxygen loss increases the fraction of copper in CU‴ oxidation state, and thus increases the density of hole carriers in the Cu-O planes. This may be the reason why the Tc of Bi-based cuprate superconductors increased after the BC treatment.

An experimental search based on previous published theoretical work was made for de Haas-van Alphen-like quantum oscillations in field emission current. The study was motivated by the possible applicability of de Haas-van Alphen measurements to the study of Fermi surfaces near real surfaces, Field emitters were fabricated from bismuth single crystals grown from the melt by a modified Bridgeman technique. Field emission current was measured with the field emitter cooled by contact with a liquid helium bath. Most measurements were made at 4.2° K, although a few measurements were made at 2.02°K; Fowler-Nordheim plots of the experimental current-voltage data were linear over several orders of magnitude. The field emission current was measured as a function of magnetic field strength to twenty kilogauss and as a function of direction, with respect to the emitter axis, for a steady field of ten kilogauss. The results of measurements on four field emitter crystals are reported in this thesis. In most of this work, de Haas-van Alphen-like quantum oscillations were not observed. In one set of data, however, de Haas-van Alphen-like oscillations having a period of 0.50 x 10⁻⁵ G⁻¹ appear to be present. The published theoretical work was reevaluated. As a result of a large effective Dingle temperature for field emitters, and because the effective masses of carriers in bismuth are anisotropic, the de Haas-van Alphen effect in field emission current could be several times smaller than has been suggested in the literature. The sensitivity of the experiments reported in this thesis was not sufficient to allow unambiguous identification of quantum oscillations at the reduced level. An outline of an experimental procedure suitable for observation of the de Haas-van Alphen-like effect in field emission current at the reduced level is provided in the final chapter.

Bismuth nanoparticles (Bi NPs) for use as an X-ray contrast material have gained significant traction in recent years due to the high atomic number and generally accepted biological tolerance of bismuth. However, to be considered a viable candidate for use in this application, water solubility is a necessity, which poses a challenge, since bismuth tends to readily oxidize. For this reason, research into the direct aqueous synthesis of Bi NPs is still in its infancy and can be very difficult, as described in Chapter 1. The remaining chapters of the thesis describe the direct aqueous synthesis of Bi NPs starting from a water-soluble bismuth tartrate (Bix(D-TA)y) precursor. Syntheses were carried out in an aerobic environment using a variety of pH and temperature conditions, from biologically compatible and inexpensive chemical reagents. Chapter 2 describes initial studies that sought to use glucose as the reducing agent and its oxidation product, gluconic acid, as the surface-stabilizing species. These studies showed glucose to be ineffective as a reducing agent for bismuth, as reactions progressed slowly and resulting particles lacked size and shape uniformity. The addition of a co-reductant, borane morpholine, was observed to result in an increased reaction rate, which yielded particles that exhibited improved size and shape uniformity. However, due to lack of surface stabilization, resulting particles were often observed to undergo oxidative dissolution upon quenching of the reaction. To better stabilize particle surfaces, glucose was replaced with 300 MW poly(ethylene glycol) (PEG 300). This change resulted in an overall decrease in the rate of reaction. The majority of syntheses using PEG as a surfactant resulted in Bi NPs that were equally unstable, as particle colloids were often observed to dissolve when quenching the reaction. For samples in which oxidative dissolution did not occur, the resulting Bi NPs were observed to be crystalline, aggregated nanostructures lacking any size or shape uniformity. For samples that underwent immediate oxidative dissolution and were afterwards left in a closed container absent of light for ~96 hours at room temperature, regrowth of Bi NPs was observed, where particle growth was thought to occur through a seed-mediated pathway. Through this seed-mediated growth method, resulting Bi NPs were observed to have significantly improved size and shape uniformity, as well as aqueous colloidal stability. Chapter 3 describes additional syntheses that yielded highly stable and relatively size uniform aqueous Bi NPs, which were prepared by chemical reduction of the same Bix(D-TA)y precursor. In these studies, hexamethylenediamine (HMD) was used as the surface-stabilizing agent in place of PEG 300. Analysis via FTIR revealed the presence of the ligand tartrate, which facilitated a simple acid/base titration method of particle isolation. With the addition of HCl, particle colloids would flocculate, allowing for ease of separation from the reaction medium by centrifugation. The Bi NPs could then be re-dispersed in aqueous solution with the addition of NaOH.

Reproduction de : Thèse doctorat : électrochimie / chimie des matériaux : Metz : 2003. / Titre provenant de l'écran-titre. Notes bibliographiques.

Thesis (Ph. D.)--University of Michigan, 1931. / Cover title. Reprinted from an article, by Russell A. Fisher and S. Goudsmit, published in Physical review, v. 37, no. 9, May 1, 1931.

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