MSc., Faculty of Science, University of the Witwatersrand, 2011 / This research focuses on the study of the impurities in low-strain high pressure, high temperature (HPHT) synthetic diamonds. The dominant characterisation methods are synchrotron-based x-ray techniques, supported by other conventional laboratory techniques. The research identifies the role of defects in generating long-range strain. A software programme based on the dynamical theory of x-ray diffraction has specially been developed to quantify the local changes in the lattice parameter and the local lattice inclinations (combined as the “effective misorientation” or local Bragg angle change). In recent measurements, the strain sensitivity of the (quantitative) x-ray plane-wave monochromatic topography was increased to the level of 10−8. This level of sensitivity was achieved using the double crystal technique with successively higher order reflections and correspondingly, higher energy x-rays. This is a level which has never previously been accessed for diamond. Preliminary results for this research have already contributed immensely to driving a technological development of a new range of diamond-based x-ray optical elements for modern third and fourth-generation x-ray sources like synchrotron storage rings and Free Electron Lasers (FEL), where industry (industrial diamond growers) and end-users (the synchrotrons of the world) participate collaboratively in a research and development programme.

No description available.

Thesis (Ph.D.)--University of Melbourne, Dept. , 19. / Typescript (photocopy). Includes bibliographical references.

No description available.

Thesis (M.Sc.(Chemistry))--University of Pretoria, 2001. / Summaries in Afrikaans and English.

A thesis submitted to the Faculty of engineering. University of Witwatersrand. Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy Pretoria, 1995 / This thesis describes a study of the friction and wear characteristics of a range of oxide and silicon-based ceramics sliding against AlSI 440C stainless steel, as well as various sliding combinations of two types of De Beers polycrystalline diamond (PCD), namely Syndite and Syndax, To facilitate the former work, a high-speed reciprocating sliding test machine with computerized data acquisition and control was developed. It was confirmed that under water-lubricated sliding, the oxide ceramics (alumina, PSZ, 3YTZP, and Ce-TZP) showed higher friction coefficients and Weal' rates than the silicon-based ceramics (Sialon and silicon nitride). This was related to different levels of adhesion and the formation of metallic transfer films. For the zirconia ceramics, increased transformation toughening was associated with increased surface fracture damage and metallic film formation. In general, the metallic transfer films were beneficial, protecting the underlying ceramic and dominating the friction and wear behaviour. The superior performance of the silicon-based ceramics was related to the formation of lubricious tribofilms containing silicon oxides and hydroxides. Experiments with synthetic mine water as lubricant demonstrated that the presence of significant amounts of chloride and sulphate in the water generally reduced friction and wear. This was tentatively explained in terms of reduced adhesion and the promotion of iron oxide and hydroxide formation. It is suggested that the influence of sulphate may be more important in thi'3 regard than that of chloride. The tribological behaviour of self-mated Syndite PCD sliding couples is dominated by the formation of Co-rich trlbofilms, which nrc associated with increased friction coefficients and reduced load carrying capacity (LCC). Syndax, which employs silicon as the binder phase, shows lower friction coefficients anti higher LCe under both dry and water-lubricated sliding conditions. Mixed Syndax/Syndite couples show superior performance to self-mated Synditc tinder dry sliding conditions, but 110 improvements in the presence of water. The former effect is related to the preferential removal of Co 11'0111 the Syndite surface to the Syndax / GR 2017

Thesis (MEng(MiningEngineering))--University of South Australia, 2001.

Thesis (M.Eng.)--University of Wollongong. / Typescript. Includes bibliographical references: leaf 131-135.

This memorandum outlines the role of De Beers and its leading position in the international diamond industry. It is designed to give a brief overview of the “diamond pipeline” that leads from prospecting and mining of diamonds in remote parts of Africa and elsewhere to glamorous jewellers’ shops the world oven It looks particularly at the unique and important role South Africa plays in the diamond pipeline.