<p>Steel-clad calcium wire was fed into 40 kg heats of AISI steel with various sulphur and aluminum contents under argon atmosphere. Samples were taken continuously during and after calcium injection for chemical and inclusion analysis from more than twelve heats of injection. Calcium dissolution was found to be enhanced by instantaneous reactions with oxygen and sulfur in the boundary layer. The unreacted calcium diffuses through the gas-liquid film into the melt for oxide and sulfide inclusion modification. The overall interaction between oxides and sulfides with the bulk drives towards the equilibrium of (CaO) + S = (CaS) + O. The system paths from the initial state to the final state were kinetically studied with the assistance of a_CaS-a_MnS diagrams, which were calculated by applying a regular solution model to the solid phase and an ideal model to the liquid phase of the CaS-MnS phase diagram at various steelmaking temperatures. A mathematical model for the multiphase kinetics was developed to interpret the calcium dissolution, deoxidation, desulphurization, oxide and sulfide inclusion modification during and after calcium injection. The implications for full-scale operation were discussed.</p> / Doctor of Philosophy (PhD)

<p>Measurements by dielectric spectroscopy, ultrasonics and calorimetry ofseveral low viscosity monomeric liquids undergoing spontaneous chemical reaction, to form three new, linear chain polymers under isothermal conditions, have been used to determine how the number ofcovalent bonds formed during the growth of a linear chain affects the dielectric and ultrasonic properties, their respective relaxation times, and their spectral shape. The dielectric properties changed in the following manner. During this reaction, the static permittivity decreased and the relaxation time increased towards limiting values. As the number of covalent bonds increased towards the Avogadro number, the change in the complex permittivity as measured for a fixed frequency was phenomenologically similar to that observed on varying the frequency, although the exact formalisms in both cases differed. In both cases the relaxation function could be well described by a stretched exponential or sum ofexponentials, characterized by a temperature and system dependent exponent that decreased as the state of the system changed from a monomeric liquid to a fully reacted polymer. At later stages of chemical reaction a second relaxation process at higher frequencies is revealed. The dielectric manifestation of the irreversible process of covalent bond formation is remarkably similar to that observed on supercooling a molecular or polymeric liquid.</p> <p>Longitudinal velocity and attenuation of ultrasonic waves travelling through the three molecular liquids at different temperatures have been measured as its molecules combine irreversibly to form large entities and thereby decrease the diffusivity and increase the configurational restrictions to their dynamics. From these data, the longitudinal modulus and compliance are calculated, and the molecular relaxation time and related properties are deduced and interpreted in terms ofthe number of covalent bonds formed, by a formalism that connects the size ofthe molecules in the liquid with its elastic behaviour. This relaxation time increases monotonically with increase in the molecule's size, tending to infinity as the number ofcovalent bonds formed approaches Avogadro's number. The complex plane plots ofthe modulus and compliance have a shape which is described by a skewed arc function, with a temperature dependent exponent ϒ, that ranges in values from 0.33- 0.31 for modulus and 0.39-0.45 for compliance. Departure from this shape is shown to be due to contributions from non-zero shear viscosity for relatively small size of molecules, and contributions from a faster, or sub Tg-relaxation process when the molecular size is large, which is similar to the behaviour for the dielectric properties. Simulation of the data suggests that this sub Tg-relaxation process, which is progressively more separated from the main relaxation process as the molecular size increases, contributes significantly to the high frequency elastic properties. The measured longitudinal modulus has been deconvoluted to show that the increase in the bulk modulus, and not the shear modulus, dominates the elastic properties when the molecular size increases. Comparison ofthe calculated relaxation times for the longitudinal modulus and compliance with the dielectric relaxation time show that the compliance and dielectric data change in a remarkably similar manner with increasing time of chemical reaction, which is unexpected owing to their different mechanisms.</p> <p>In the last part of this work, the dipolar diffusion in the glassy and supercooled liquid states of 9 additional molecular liquids and oftheir linear chain or network polymerized states formed by condensation-polymerization at different temperatures and times have been studied by measuring the dielectric properties for a fixed ac frequency of 1 kHz. The study showed that as the extent of polymerization increased with increasing isothermal temperature of polymerization, the sub-Tg relaxation peak due to localized molecular motions in the molecular state became gradually extinct, and a corresponding peak at a higher temperature evolved and reached its maximum height. The temperature of the sub-Tg relaxation peak in the polymerized state differed from that of the α-relaxation peak of the supercooled molecular liquid by as much as 70K, but, in several cases, the two temperatures were similar. Reasons for the latter occurrence are given in phenomenogical terms. It is concluded that the localized relaxation modes of the polar segments of the macromolecule are not related to the modes of molecular diffusion in the monomeric liquid state above its Tg. The localized relaxation characteristic of the glassy molecular state persists in the incompletely polymerized state, where it is seen as a ϒ-relaxation.</p> / Doctor of Philosophy (PhD)

<p>The central argument of this paper is that efforts to rationalise the European defence industrial base are both pre-requisite to and incompatible with the broader goal of Alliance wide specialisation and rationalisation, at least withiin NATO as it is presently configured. Broadly, the contention is that rising weapons costs in the context of stable or shrinking defence budgets are moving the NATO alliance toward structural disarmament. In response to this trend, the Alliance has been forced to consider means of reforming the highly wasteful defence industrial effort so that the price of military preparedness can be kept within reasonable limits. From a simple economic perspective, the creation of a NATO-wide free-trade regime in defence goods wold seem to be the optimal approach to this program. Free trade, however, is fraught with political hazards that make it largely unacceptable to most Alliance governments.</p> <p>An apparently attainable alternative to free trade in this connexion is "managed specialisation." Managed specialisation, however, also has its limitations. Put simply, in order to rationalise the Allied development and production effort, Europe must first of all "get itself together" and begin producing competitive equipment at competitive prices. In order to achieve this, however, Europe must reform its own domestic market in order to realise US-scale production economies and capitalisation rates. The crux of the problem is that this necessarily requires greater European collaboration and protectionism, and ultimately suggests that Europe will begin to offer the US more global competition. As this is unlikely to sit well with the Americans, it would seem that--contrary to the original intent--European rationalisation seems destined to result in more, not less, fracture within the Alliance defence industrial base. Although the verdict is not yet final, the Eurofighter programme would seem to confirm this hypothesis.</p> / Master of Arts (MA)

<p>In this thesis, solutions to the problem of low power density caused by pH<br />deviation in anode and cathode of a glucose/oxygen based enzymatic fuel cell using GOx and FMCA are provided. Moreover, conclusive evidence of a large active area in this type of fuel cell is determined using a transient state study. The complete process of electrical double layers formation is described.<br />A survey of the solutions to low power density caused by pH deviation is conducted and two feasible alternatives are suggested. The first alternative, using Tris buffer with no alkaline ions resulted in even larger pH gradient. The second alternative: using anion exchange membrane (AEM) successfully reduced the pH gradient by introducing lower power density than the biofuel cells using a Nafion membrane. It was proven that the high internal resistance of the AEM is responsible for the drop in energy output ofthe biofuel cell.<br />A transient study was conducted on the biofuel cells in order to investigate the<br />internal resistance of the components. A discrepancy was found when applying the<br />rarely-mentioned internal circuit model to biofuel cells. The model predicted a much<br />larger surface area for the electrode than was physically measured for the cells. It is<br />therefore concluded that the proposed electrochemical double layers are in the electrolyte as well as on the interface. Finally, a detailed description of electron/proton double layer in the electrolyte associated with each reaction step is given, assuming that double layers can be found on the enzymes and mediators.<br />A complete list of requirements for equivalent circuit is portrayed for our glucose/oxygen enzymatic biofuel cell. The equivalent circuit suggests a possible<br />direction for future biofuel cell research.</p> / Master of Applied Science (MASc)

<p>AI-Mg sheets (5xxx series) for body-in-white (BIW) application are mostly<br />used for automotive structural parts due to their specific combination of<br />formability and strength. The limiting behavior for the wide application of AA5754<br />sheets is strain localization. The effect of microstructure inhomogeneties on<br />strain localization have recently been attracting a great deal of interest but not<br />fully understood. In this present work, the effect of grain-level microstructure<br />inhomogeneties in AA 5754 sheets is investigated.<br />Uniaxial tensile experiments combined with two 2-dimensional Digital<br />image correlation (DIG) techniques have been performed on coarse-grained<br />specimens to evaluate the deformations of individual grains. Grain orientations<br />and their evolution were measured by the electron backscattered diffraction<br />(EBSD) technique, and surface features such as slip traces were observed by<br />optical microscopy.<br />The regions of high local strain ('hot spots') within coarse-grained samples<br />nucleate at a very early stage of deformation and most of them continuously<br />grow throughout most deformation stages. 'Hot spots' are correlated with 'soft'<br />grains (i.e. grains with high Schmid factors) and soft-evolution grains (i.e. grains<br />with the <101> direction close to tensile axis).</p> / Master of Applied Science (MASc)

<p> A new paradigm in biomedical engineering calls for biologically active implants that are absorbed by the body over time. One popular application for this concept is in the engineering of endovascular stents that are delivered concurrently with balloon angioplasty. These devices enable the injured vessels to remain patent during healing, but are not needed for more than a few months after the procedure. Early studies of iron- and magnesium-based stents have concluded that magnesium is a potentially suitable base material for such a device; alloys can achieve acceptable mechanical properties and do not seem to harm the artery during degradation.</p><p> Research done up to the onset of research contained in this dissertation, for the most part, failed to define realistic physiological corrosion mechanisms, and failed to correlate degradation rates between <i>in vitro</i> and <i>in vivo</i> environments. Six previously published works form the basis of this dissertation. The topics of these papers include (1) a method by which tensile testing may be applied to evaluate biomaterial degradation; (2) a suite of approaches that can be used to screen candidate absorbable magnesium biomaterials; (3) <i>in vivo-in vitro</i> environmental correlations based on mechanical behavior; (4) a similar correlation on the basis of penetration rate; (5) a mid-to-late stage physiological corrosion mechanism for magnesium in an arterial environment; and (6) the identification of corrosion products in degradable magnesium using transmission electron microscopy.</p>

Hypersonic vehicles require material systems that can withstand the extreme environment they experience during flight. Carbon-based materials and ultra-high temperature ceramics are candidates for materials systems that will protect hypersonic vehicles. In order to study the material response, an oxyacetylene torch facility and thermal gravimetric analysis are used to investigate the gas-solid interactions under conditions that simulate aspects of flight. The oxyacetylene torch facility is characterized as a function of position from the tip for heat flux and oxygen content. By understanding the local heat flux and oxygen conditions, experiments are designed so that graphite ablation rates can be measured as a function of heat flux and partial pressure of oxygen. Further investigation shows that composition of the material influences the temperature response where ultra-high temperature ceramics exhibit the lowest surface temperatures. Using thermal gravimetric analysis, the isothermal oxidation behavior of ultra-high temperature ceramics from 1000-1600°C is investigated using a Dynamic Non- Equilibrium method in order to understand the reaction kinetics of ZrB₂-SiC where parabolic rate constants are determined. Isothermal oxidation behavior is compared to non-isothermal mass gain and oxide scale formation where specimens oxidized isothermally gain 3 times more mass and have oxide scales 4 times as thick. Finally, the effect of SiC content in ZrB₂ on temperature during oxyacetylene torch testing is determined. Increasing the amount of SiC results in lower front face temperatures because more heat is absorbed due to the endothermic reactions of evaporation of SiO₂.

<p> The objective of this research was to characterize the seawater transport and its effect on the transverse tensile strength of a carbon/vinylester composite. The moisture contents of neat vinylester and unidirectional carbon/vinylester composite panels immersed in seawater were monitored until saturation. A model for moisture up-take was developed based on superposition of Fickian diffusion, and Darcy&rsquo;s law for capillary transport of water. Both the predicted and measured saturation times increased with increasing panel size, however the diffusion model predicts much longer times while the capillary model predicts shorter time than observed experimentally. It was also found that the saturation moisture content decreased with increasing panel size. Testing of macroscopic and miniature composite transverse tensile specimens, and SEM failure inspection revealed more fiber/matrix debonding in the seawater saturated composite than the dry composite, consistent with a slightly reduced transverse tensile strength. </p>

<p> The tensile strength of the fiber/matrix interface was determined through the development of an innovative test procedure. A miniature tensile coupon with a through-thickness oriented, embedded single fiber was designed. Tensile testing was conducted in a scanning electron microscope (SEM) while the failure process could be observed. Finite element stress analysis was conducted to determine the state of stress at the fiber/matrix interface in the tensile loaded specimen, and the strength of the interface. Test specimens consisting of dry E-glass/epoxy and dry and seawater saturated carbon/vinylester 510A were prepared and tested. The load at the onset of debonding was combined with the radial stress distribution near the free surface of the specimen to reduce the interfacial tensile strength (&sigma;<i>_i</i>). For glass/epoxy, &sigma;<i>_i</i> was 36.7&#129;&plusmn;8.8 MPa. For the dry and seawater saturated carbon/vinylester specimens the tensile strengths of the interface were 23.0&#129;&plusmn;6.6 and 25.2&#129;&plusmn;4.1 MPa, respectively. The difference is not significant.</p>

<p> For galvanized or galvannealed steels to be commercially successful, they must exhibit several attributes: (i) easy and inexpensive processing in the hot mill, cold mill and on the coating line, (ii) high strength with good formability and spot weldability, and (iii) good corrosion resistance. At the beginning of this thesis, compositions with a common base but containing various additions of V or Nb with or without high N were designed and subjected to Gleeble simulations of different galvanizing(GI), galvannealing(GA) and supercooling processing. The results revealed the phase balance was strongly influenced by the different microalloying additions, while the strengths of each phase were somewhat less affected. Our research revealed that the amount of austenite formed during intercritical annealing can be strongly influenced by the annealing temperature and the pre-annealing conditions of the hot band (coiling temperature) and cold band (% cold reduction). In the late part of this thesis, the base composition was a low carbon steel which would exhibit good spot weldability. To this steel were added two levels of Cr and Mo for strengthening the ferrite and increasing the hardenability of intercritically formed austenite. Also, these steels were produced with and without the addition of vanadium in an effort to further increase the strength. Since earlier studies revealed a relationship between the nature of the starting cold rolled microstructure and the response to CGL processing, the variables of hot band coiling temperature and level of cold reduction prior to annealing were also studied. Finally, in an effort to increase strength and ductility of both the final sheet (general formability) and the sheared edges of cold punched holes (local formability), a new thermal path was developed that replaced the conventional GI ferrite-martensite microstructure with a new ferrite-martensite-tempered martensite and retained austenite microstructure. The new microstructure exhibited a somewhat lower strength but much high general and local formabilities. In this thesis, both the physical and mechanical metallurgy of these steels and processes will be discussed. This research has shown that simple compositions and processes can result in DP steels with so-called Generation III properties. </p>