A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. May 2016. / Tungsten carbide cobalt (WC-Co) cemented carbides are widely used for cutting, drilling, machining and as wear resistant materials due to the combination of high hardness and fracture toughness. In this work, we report on as-milled and as-sintered WC-10Co-20Fe samples which were ball milled for 15 hrs and sintered using liquid phase sintering (LPS). These samples were investigated by Vickers hardness test, microstructural analysis, X-ray diffraction (XRD), transmission Mössbauer spectroscopy (TMS) and conversion electron Mössbauer spectroscopy (CEMS) techniques. A mean hardness value of 1160 ± 42 HV was obtained for WC-10Co sample while a value of 776 ± 35 HV was determined for the WC-10Co-20Fe using the Vickers hardness tester. The lower hardness value for WC-10Co-20Fe is attributed to the high volume of the binders (10% Co and 20 %Fe) incorporated in the sample. The microstructural analysis of the as-sintered WC-10Co and WC-10Co-20Fe samples reveals that the light regions represent the WC phases and the dark regions signify the presence of the Co and CoFe phases in the as-sintered WC-10Co and WC-10Co-20Fe samples, respectively. The energy dispersive spectroscopy (EDS) of the as-sintered samples shows the presence of the starting powders used (WC, Co and Fe) and some Cr contamination resulting from either the production process or the starting powders. / GR 2016

This research project is a preliminary investigation of the effect of SiC abrasive breakdown on the wear rate of a WC-12wt%Co mining alloy. Wear tests were carried out on a two body-sliding wear apparatus under (a) “Ideal” (replacing the SiC paper periodically to ensure continual exposure to fresh abrasives), (b) “No debris” (removing the wear debris periodically) and (c) “With debris” (retaining the wear debris for the entire wear test) wear conditions. The WC-12wt%Co specimens and SiC abrasive grits were examined before and after the wear tests using optical, stereo and electron microscopy. As wear progressed, the SiC abrasives blunted thereby increasing the abrasive/specimen contact area, resulting in a reduction in the WC-12wt%Co wear rate. Wear debris clogging the interstices between the abrasive grits caused a further reduction in the WC-12wt%Co wear rate by adding to the abrasive/specimen contact area already created by blunting. Increasing the applied load resulted in an increase in the WC-12wt%Co wear rate under “Ideal” wear conditions. Under the remaining wear conditions, the increased load resulted in a faster deterioration of the SiC grits. The dominant wear mechanisms under all conditions are characterized by hard abrasive wear that caused extensive grooving, Co binder extrusion and cracking and fragmentation of WC grains.

本論文主要研究了鹼性添加劑促進二價鈷卟啉絡合物(Co{U+1D35}{U+1D35}(por))在苯溶劑中與溴代苯及其衍生物(ArX)的反應及鹼性條件下，該絡合物催化溴代苯及其衍生物的脫鹵反應。 / 第一部分主要介紹了在KOH和{U+1D57}BuOH存在下，Co{U+1D35}{U+1D35}(por)斷裂碳-溴鍵（Ar-Br）形成各種三價鈷卟啉芳基絡合物（Co{U+1D35}{U+1D35}{U+1D35}(por)Ar）(eq. 1)。 / 機理研究顯示，Co{U+1D35}{U+1D35}(por)首先從ArBr中得到Br·形成芳基自由基（Ar·）及Co{U+1D35}{U+1D35}{U+1D35}(por)Br (Scheme 1, i). Ar 與另一個Co{U+1D35}{U+1D35}(por)反應得到Co{U+1D35}{U+1D35}{U+1D35}(por)Ar (Scheme 1, ii)。在鹼性條件中，Co{U+1D35}{U+1D35}{U+1D35}(por)Br 最終形成CoII(por)從而繼續反應 (Scheme 1, iii-iv)。 / 第二部份主要介紹了在200 ºC時， 鹼性條件下Co{U+1D35}{U+1D35}(por)催化鹵代苯及其衍生物脫鹵形成對應芳烴的反應 (eq. 2)。 該反應在四氫呋喃（THF）及異丙醇 ({U+2071}PrOH) 中都可以進行。 / 機理研究顯示， Co{U+1D35}{U+1D35}(ttp) 首先與ArBr反應得到Ar· 和Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br (Scheme 2, i)。 Ar 從溶劑（THF 或者 {U+2071}PrOH）得到一個氫原子從而形成芳烴 (ArH) (Scheme 2, ii)。 Ar 也可以與另一個Co{U+1D35}{U+1D35}(ttp) 反應得到Co{U+1D35}{U+1D35}{U+1D35}(ttp)Ar。 在鹼性條件下， Co{U+1D35}{U+1D35}{U+1D35}(ttp)Ar水解形成ArH 和 Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH (Scheme 2, iii)。 Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br 與KOH進行取代反應得到Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH, 并最終形成催化劑Co{U+1D35}{U+1D35}(ttp) (Scheme 1, iii-iv)。所以， 溶劑 （THF 或者 {U+2071}PrOH）及H₂O 都可以作為Co{U+1D35}{U+1D35}(ttp) 催化鹵代苯脫鹵形成芳烴的氫的來源。 / This thesis focuses on (1) the base-promoted aryl bromine bond (Ar-Br) cleavages by cobalt(II) porphyrins and (2) catalytic hydrodehalogenation of aryl bromides by cobalt(II) porphyrin in alkaline conditions. / Part I describes the aryl bromine bond cleavage with cobalt(II) porphyrin (Co{U+1D35}{U+1D35}(por)) in the presence of KOH and {U+1D57}BuOH in benzene at 150ºC to give cobalt(III) porphyrin aryls (Co{U+1D35}{U+1D35}{U+1D35}(por)Ar) (eq. 1). / [With images] / Mechanistic studies suggest that CoII(por) first abstracts the bromine atom from the aryl bromide to form aryl radical (Ar) and Co{U+1D35}{U+1D35}{U+1D35}(por)Br (Scheme 1, i). Ar· further reacts with Co{U+1D35}{U+1D35}(por) to generate Co{U+1D35}{U+1D35}{U+1D35}(por)Ar (Scheme 1, ii). Co{U+1D35}{U+1D35}{U+1D35}(por)Br undergoes ligand substitution with KOH to form Co{U+1D35}{U+1D35}{U+1D35}(por)OH, which quickly gives Co{U+1D35}{U+1D35}(por) and H₂O₂ (Scheme 1, iii). H₂O₂ undergoes base-promoted decomposition to form H₂O and O₂ (Scheme 1, iv). / [With images] / Scheme 1 Reaction Mechanism of Base-promoted Ar-Br Cleavage with Co{U+1D35}{U+1D35}(por) / Part II describes the catalytic hydrodehalogenation of aryl bromides by Co{U+1D35}{U+1D35}(ttp) at 200 ºC in alkaline conditions to generate arenes (eq. 2). The reaction can occur in both THF and {U+2071}PrOH. / [With images] / Mechanistic studies suggest that Co{U+1D35}{U+1D35}(ttp) also first abstracts the bromine atom from the aryl bromide in the presence of KOH to form Ar· and Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br (Scheme 2, i). Ar· can abstract a hydrogen atom from the solvent (THF or {U+2071}PrOH) to form arenes (Scheme 2, ii). Ar also could be trapped by Co{U+1D35}{U+1D35}(ttp) to give Co{U+1D35}{U+1D35}{U+1D35}(ttp)Ar, which undergoes hydrolysis in the presence of OH⁻ to the arene (ArH) and Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH (Scheme 2, iii). Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br gives Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH by ligand substitution with KOH and Co{U+1D35}{U+1D35}{U+1D35}(ttp)OH regenerates the catalyst Co{U+1D35}{U+1D35}(ttp) (Scheme 1, iii-iv). The solvent (THF or {U+2071}PrOH) and H₂O are the hydrogen sources for the catalytic dehalogenation of aryl bromides by Co{U+1D35}{U+1D35}(ttp). / Scheme 2 Mechanism of Catalytic Dehalogentaion of ArBr by CoII(ttp) in Alkaline Media / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Liu, Chunran. / "October 2012." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves ). / Abstracts also in Chinese. / Chapter Table of Contents --- p.i / Chapter Acknowledgements --- p.iv / Chapter Abbreviations --- p.v / Chapter Abstract --- p.vi / Chapter Part I --- The Base-promoted Aryl Bromine Bond Cleavage of Aryl Bromides by Cobalt(II) Porphyrins / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1.1 --- Introduction to Porphyrins and Group 9 metalloporphyrins --- p.1 / Chapter 1.1.1 --- Porphyrin Ligand --- p.1 / Chapter 1.1.2 --- Group 9 metalloporphyrins --- p.2 / Chapter 1.1.3 --- Chemistry of Group 9 Metalloporphyrin --- p.3 / Chapter 1.1.3.1 --- Chemsitry of M{U+1D35}(por) --- p.3 / Chapter 1.1.3.2 --- Chemsitry of M{U+1D35}{U+1D35}(por) --- p.4 / Chapter 1.1.3.3 --- Chemsitry of M{U+1D35}{U+1D35}{U+1D35}{U+1D35}(por) --- p.4 / Chapter 1.1.3.4 --- Chemsitry of M{U+1D35}{U+1D35}{U+1D35}{U+1D35}(por)OH --- p.6 / Chapter 1.2 --- Physical Properties of Aryl Halides --- p.9 / Chapter 1.3 --- Synthesis of Metalloporphyrin Aryl --- p.10 / Chapter 1.4 --- Modes of Reactivity of Aryl Carbon-Halogen Bond Cleavage by Transition Metal Complexes --- p.11 / Chapter 1.4.1 --- Oxidative Addition (OA) --- p.11 / Chapter 1.4.2 --- Nucleophilic Aromatic Substitution (SNA) --- p.14 / Chapter 1.4.3 --- Halogen Atom Transfer (HXA) --- p.14 / Chapter 1.4.4 --- Radical ipso-Substitution --- p.15 / Chapter 1.5 --- Scope of Part I --- p.16 / Chapter Chapter 2 --- Base-promoted Aryl Bromine Bond Cleavage of Aryl Bromides by Cobalt(II) Porphyrins / Chapter 2.1 --- Introduction --- p.17 / Chapter 2.2 --- Objectives of the Work --- p.18 / Chapter 2.3 --- Preparation of Starting Materials --- p.18 / Chapter 2.3.1 --- Synthesis of Porphyrin --- p.18 / Chapter 2.3.2 --- Synthesis of Cobalt(II) Porphyrin --- p.18 / Chapter 2.3.3 --- Synthesis of Co{U+1D35}{U+1D35}{U+1D35}(ttp)Br --- p.19 / Chapter 2.4 --- Discovery of Ph-Br Bond Cleavage by Co{U+1D35}{U+1D35}(ttp) with KOH --- p.19 / Chapter 2.5 --- Optimization of Reaction Conditions --- p.20 / Chapter 2.5.1 --- {U+1D57}BuOH Effect --- p.20 / Chapter 2.5.2 --- Solvent Effect --- p.21 / Chapter 2.5.3 --- Temperature Effect --- p.21 / Chapter 2.5.4 --- Base Loading Effect --- p.22 / Chapter 2.6 --- Summary of Optimization of the Base-promoted Ph-Br Bond Cleavage by Co{U+1D35}{U+1D35}(ttp) --- p.22 / Chapter 2.7 --- Porphyrin Ligand Effect --- p.23 / Chapter 2.8 --- Substrate Scope of Aryl Bromides --- p.24 / Chapter 2.9 --- Mechanistic Studies --- p.25 / Chapter 2.9.1 --- Possible Pathways of Ar-Br Bond Cleavage --- p.25 / Chapter 2.9.1.1 --- Oxidative Addition (OA) --- p.26 / Chapter 2.9.1.2 --- Nucleophilic Aromatic Substitution (SNA) --- p.27 / Chapter 2.9.1.3 --- Radical ipso-Substitution --- p.28 / Chapter 2.9.1.4 --- Halogen Atom Transfer (HXA) --- p.28 / Chapter 2.9.2 --- Electronic Effect of 4-Substituted ArBr by Hammett Plot --- p.29 / Chapter 2.9.3 --- Proposed Mechanism --- p.32 / Chapter 2.9.4 --- Evidence for Halogen Atom Transfer --- p.33 / Chapter 2.10 --- Conclusion --- p.35 / Chapter Chapter 3 --- Experimental Section --- p.36 / Reference --- p.53 / Chapter Part II --- Catalytic Hydrodehalogenation of Aryl Bromides by Cobalt(II) Porphyrin in Alkaline Conditions / Chapter Chapter 4 --- General Introduction --- p.58 / Chapter 4.1 --- Introduction --- p.58 / Chapter 4.1.1 --- Properties of Halogenated Aromatic Compounds --- p.58 / Chapter 4.1.2 --- Reactivity of Aryl Carbon-Halogen Bond --- p.59 / Chapter 4.2 --- Hydrodehalogenation of Aryl Halides by Transiton Metal Complexes --- p.59 / Chapter 4.2.1 --- Molecular Hydrogen (H₂) --- p.60 / Chapter 4.2.2 --- Alcohols and Metal Alkoxides --- p.61 / Chapter 4.2.3 --- Dimethyformamide (DMF) --- p.64 / Chapter 4.2.4 --- Hydrazine (NH₂-NH₂) --- p.65 / Chapter 4.2.5 --- Metal Hydrides --- p.65 / Chapter 4.2.6 --- Alkyl Grignard Reagents --- p.67 / Chapter 4.2.7 --- Formic Acid and Its Salts --- p.67 / Chapter 4.3 --- Common Reducing Agents --- p.69 / Chapter 4.3 --- Scope of Part II --- p.69 / Chapter Chapter 5 --- Catalytic Hydrodehalogenation of Aryl Bromides by Cobalt(II) Porphyrin in Alkaline Conditions / Chapter 5.1 --- Introduction --- p.70 / Chapter 5.2 --- Objectives of the Work --- p.71 / Chapter 5.3 --- Optimization of Reaction Conditions --- p.71 / Chapter 5.3.1 --- Solvent Effect --- p.71 / Chapter 5.3.2 --- Temperature Effect --- p.72 / Chapter 5.3.3 --- Base Loading Effect --- p.73 / Chapter 5.3.4 --- Porphyrin Loading Effect --- p.73 / Chapter 5.3.5 --- Atmosphere Effect --- p.74 / Chapter 5.4 --- Summary of Optimization of Hydrodehalogention of Aryl Bromides by Co{U+1D35}{U+1D35}(ttp) --- p.74 / Chapter 5.5 --- Substrate Scope of Aryl Bromides --- p.75 / Chapter 5.5.1 --- THF as the Solvent --- p.75 / Chapter 5.5.2 --- {U+2071}PrOH as the Solvent --- p.76 / Chapter 5.6 --- Catalytic Reactivity of Co{U+1D35}{U+1D35}(ttp) as the Catalyst --- p.77 / Chapter 5.7 --- Mechanistic Studies --- p.78 / Chapter 5.7.1 --- Proposed Mechanism of Hydrodehalogenation of Aryl Bromides by Co{U+1D35}{U+1D35}(ttp) --- p.78 / Chapter 5.7.2 --- Hydrogen Source Investigation --- p.80 / Chapter 5.8 --- Conclusion --- p.83 / Chapter Chapter 6 --- Experimental Section --- p.84 / Reference --- p.92 / Chapter Appendix --- Appendix I --- p.101 / Appendix II --- p.112 / Appendix III --- p.118

This thesis outlines the results of an occupational hygiene monitoring program implemented at Minara Resources' Murrin Murrin mine site. The research was conducted as part of a collaborative agreement between Edith Cowan University and Minara Resources, the title of which was

Typewritten copy / 1 v. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1953

Fischer-Tropsch synthesis is a commercial technology that allows converting synthesis gas, a mixture of CO and H2, into fuels and chemicals. This process could be one of the actors in the reduction of oil dependency of the transportation sector. In fact, it has great potential for producing synthetic fuels also from renewable sources, such as biomass, after its thermochemical conversion (gasification) into synthesis gas. Concerning the quality of a diesel fuel produced with this technology, it has a lower local environmental impact than conventional diesel, since it is practically free of sulphur and nitrogen compounds and yields lower exhaust emissions of hydrocarbons, CO and particulates. The present study focuses on the use of cobalt-based catalysts for the production of diesel. In particular, it looks upon correlation between product selectivities when varying the catalyst properties and the effect of process parameters, such as a low H2/CO ratio, typical of a biomass-derived synthesis gas, and the water partial pressure. Different cobalt-based catalysts, with different properties, such as conventional 3-dimensional porous network supports (γ-Al2O3, α-Al2O3, TiO2, SiO2), Co-loading, preparation technique, etc., were investigated in the Fischer–Tropsch reaction at industrially relevant process conditions. For a set of process conditions, a linear relationship seems to exist between the selectivity to methane (and other light products) and higher hydrocarbons (identified by the industrially relevant parameter SC5+, selectivity to hydrocarbons with more than 4 carbon atoms) indicating a common precursor. Ordered mesoporous materials (SBA-15), characterized by a 1-dimensional mesoporous network, were tested as model supports and showed the possibility of occurrence of CO-diffusion limitations at diffusion distances much shorter than those required for conventional 3-dimensional porous network supports. The linear relationship mentioned above, derived for conventional supports, was shown to be an efficient tool for indicating whether measured selectivities are affected by CO-diffusion limitations. Some of the catalysts were exposed to H2-poor syngas and to external water addition and the effects on the selectivity relationships were investigated. Furthermore, the possibility of internal water-gas shift of a H2-poor syngas with mixtures of Co/γ-Al2O3 and a Cu/ZnO/Al2O3 catalyst was investigated both as a technical solution for direct use of a model bio-syngas in the Fischer-Tropsch synthesis, and as a means to study the effect of indigenous water removal on the reaction rate to hydrocarbons. It was found that removal of indigenously produced water slows down the reaction rate significantly. Lastly, the effect of water partial pressure on the Fischer–Tropsch rate of the Co catalyst supported on narrow-pore γ-Al2O3, on its own, was studied. Inlet water partial pressure was varied by external water vapor addition at different H2/CO molar ratios ranging from 1 to 3. The effect of water showed to be positive on the rate for all the H2/CO ratios, but more significantly at H2-poor conditions. The nature of this positive effect on the rate seems to be unrelated to changes in amounts of amorphous polymeric carbon detectable by temperature-programmed hydrogenation of the spent catalyst. / <p>QC 20120914</p>

Thèse de doctorat : Chimie : Paris 12 : 2004. / Titre provenant de l'écran-titre.

Thèse de doctorat : Électrochimie : Paris 12 : 2004. / Titre provenant de l'écran-titre.

Reproduction de : Thèse de doctorat : Toxicologie : Metz : 1978. / Titre provenant de l'écran-titre. Notes bibliographiques. Index.

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2001. / "February, 2001." "Funding was provided by a grant from the National Science Foundation (OCE-9618729), the National Science Foundation Coastal Traineeship (DGE-9454129), and by an Environmental Protection Agency STAR Graduate Fellowship (U-914966-01-0)." Includes bibliographical references.