<p> An experimental investigation has been conducted into the reduction of iron oxides under blast furnace conditions. The necessary equipment has been designed, constructed and tested, and a program of study on two types of prereduced ore materials has been completed.</p> / Thesis / Master of Science (MSc)

<p> This thesis is concerned with the determination of the thermodynamics of the Fe-V-O system. </p> <p> In the first part the thermodynamics of liquid Fe-V-O alloys were studied in the temperature range of 1550-1700ºC using H₂O/H₂ equilibrium and/or an oxygen probe. 1st and 2nd order interaction parameters between V and O were determined, and the deoxidation reactions occurring when V is used as a deoxidizer were studied. Deoxidation diagrams are presented for V concentrations up to 12 wt. %. </p> <p> In the second part the thermodynamic equilibria between the lower oxides of vanadium (V - VO₀ٜ₂₋ₓ, VO₀ٜ₂₊ₓ - VO₁₋ᵧ, VO₁₊ᵧ - VO₁ٜ₅) were determined in the range 800-1400ºC using a solid state EMF technique, and the free energy of the formation of the oxides VO₀ٜ₂₊₍₋₎ₓ, VO₁₊₍₋₎ᵧ, VO₁ٜ₅ was estimated. </p> / Thesis / Doctor of Philosophy (PhD)

Experiments were carried out on the solidification of iron-manganese alloys containing sulphur and carbon. The alloys were solidified under controlled conditions in a travelling furnace constructed especially for the investigation. Qualitative and quantitative metallography and electron-probe microanalysis were used to determine the solidification structure, dendrite arm spacings, solute concentration profiles and inclusion compositions. The results were interpreted in the light of existing knowledge and concepts especially developed for the purpose of this investigation. / Thesis / Doctor of Philosophy (PhD)

<p> An experimental evaluation of three desulphurisers for pig iron has been conducted. Sodium vapor, blast furnace slag enriched with cerium oxide and a rare earth alloy named misch metal have been used. </p> / Thesis / Master of Engineering (MEngr)

<p> Small scale tests were utilized in order to obtain characteristic fracture mechanics parameters such as the crack opening displacement (C.O.D.) and the J-integral. Two main types of steels were used (H.S.L.A. and AISI 4340) in obtaining data over a wide range of yield strengths and ductilities. Tests were done to see the effect of both notch geometry and sample geometry·in one of the H.S.L.A. steels, and it is verified that the minimum value of C.O.D., at crack initiation in plane strain, is independent of the geometry and plastic zone size. Further the development of a simple single specimen J-integral test method is done during this work. In terms of the data obtained both the minimum C.O.D.i values and the Jlc values increase with increasing ductility of the materials tested. In the attempt to relate the magnitude of the fracture toughness with microstructural parameters and the limiting processes occuring at the crack tip prior to fracture, the concept of the process zone is discussed. For this study a simple plain carbon steel spheroidized with different carbon contents was examined in addition to the H.S.L.A. and 4340 steels. From the data obtained the minimum C.O.D.i at crack initiation was found to be approximately equal to the product of the materials plain strain ductility and a characteristic distance scaling with the spacing between large non metallic inclusions or the spacing between the bands of the sulphides. </p> / Thesis / Master of Engineering (MEngr)

<p> The diffusion coefficient of Co has been measured as a function of temperature in the body-centered-cubic phase of 99.99% zirconium. The diffusion rates are extraordinarily large, and follow the relation D = [3.26 ± 2.77] x 10^(-3) exp -(21,820 ± 960/RT) cm^2 /sec over the range 900 to 1600°C. </p> <p> The Arrhenius plot has a positive curvature above 1600°C. The influence of cobalt additions on the diffusion of 95 ZR and 60 Co in dilute Zr-Co alloys was studied from 0 -2 at.% cobalt at 933°C. A theoretical model was developed to relate the effect to the solute correlation factor. It is established that diffusion in these systems cannot be accounted for in terms of a vacancy mechanism alone. Other models are discussed. </p> / Thesis / Doctor of Philosophy (PhD)

<p> The oxidation kinetics of a 1.5 ʷ/ₒ silicon-iron alloy in atmospheres of carbon dioxide - carbon monoxide at 890ºC and 1000ºC have been determined with a gravimetric balance as a function of gas composition. The reaction was observed to proceed in three stages. </p> <p> In The initial stage simultaneous growth of wustite-fayalite nodules and an amorphous silica film on different regions of the specimen was observed and this mixed reaction continued until complete coverage by a uniform scale was achieved. A model involving bother lateral and vertical growth of the oxide nodules and vertical growth of the silica film has been proposed to rationalize these kinetics. </p> <p> The second stage involving fluctuations in the reaction rate was observed in atmospheres of low oxidizing potential. These fluctuations were associated with the formation of massive fayalite bands, brought about by silicon supersaturation of the wustite and alloy. At high oxidizing potentials, this stage was not observed. </p> <p> At long times, a third stage consisting of linear reaction kinetics was observed. A model based on gas-oxide interfacial reaction control, involving the dissociation of carbon dioxide and incorporation of the chemisorbed oxygen into the wustite lattice has been advanced to describe these kinetics. The observed gas pressure dependence of the linear rate constants is consistent with the model. </p> / Thesis / Doctor of Philosophy (PhD)

<p> The objectives of the present study were to investigate the reaction mechanisms and the effects of certain physical variables on the overall reaction rate of the conversion of aqueous Na2S to gaseous H2S by bubbling with CO2 gas, which is a simultaneous absorption-desorption reaction.</p> <p> The dependence of reaction rate on the physical variables investigated were the volumetric flow rate and the CO2 partial pressure of inlet gas and reaction temperature. Potential advantages of a pressurized reaction system were also studied. It was found that the effect of reaction temperature on the overall reaction rate was relatively small as compared to that of inlet gas flow rate and CO2 partial pressure.</p> <p> Gas-liquid interfacial area was estimated and the overall reaction rate constant determined. It was found that the carbonation conversion of Na2S is first order with respect to both the HS- ion concentration of the liquid phase and the CO2 partial pressure of the inlet gas.</p> <p> The rate limiting step of the overall conversion reaction, under the present laboratory conditions, appeared to be the desorption of hydrogen sulfide.</p> / Thesis / Master of Science (MSc)

Title: The Effect in Strain Path on Mechanical Behaviour of an Al-Cu Alloy, Author: Nicole D.W. Martin, Location: Thode / <p>The primary objective of the present study was to examine the effect of a 90° change in strain path, on the mechanical behaviour of an alloy, and its relation to the microstructure. In order to achieve this, the mechanical behaviour in uniaxial tension and compression of three different heat treatments of an Al 3.6 wt% Cu alloy and of pure aluminum were investigated. The heat treatments include a solid solution, a peak aged and an averaged condition. The results show a large 'Bauschinger' type effect in the overaged Al-Cu after 15% pre strain.</p> <p>The differences in mechanical behaviour in the materials studied were rationalized with the aid of transmission electron microscopy observations, and work hardening models from the literature. A simple model which relates the work hardening behaviour to a measurable microstructural feature via the initial obstacle spacing, is presented and compared with the experimental data.</p> <p>The fracture behaviour of each of the materials was also observed. The results are documented in a generalized form of a plane stress map, and discussed in terms of the movement of the material as yield surface in stress space as it work hardens. The potential use of this type of map for representing ductile fracture processes as well as intergranular surfaces ( for a wide range of stress states ) is discussed.</p> / Thesis / Master of Science (MS)

Title: The Oxidation Properties of Iron-Nickel Alloys in CarbonDioxide-Carbon Monoxide Atmospheres at 1000°C, Author: Larry A. Morris, Location: Thode / <p>In this thesis, the results of oxidation tests carried out on iron-nickel alloys in carbon dioxide - carbon monoxide atmospheres at 1000°C are presented. Linear oxidation kinetics were observed for the formation of wustite on alloys containing up to 50 weight % nickel. Spinel oxides appear on alloys containing greater them 50% nickel. A subscale developed in all alloys investigated. An oxidation model is presented for the constant uptake of oxygen based on detailed balancing of the individuol reaction steps, assuming thet dissociation of carbon dioxide is the rate controlling process. The subscale formation mechanism is based on the principles of diffusion in multicomponent metallic systems . Theoretical relationships are presented which adequately account for the experimental observation</p> / Thesis / Doctor of Philosophy (PhD)