<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)

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.

Iron-cobalt (FeCo) and its various alloys have many applications where soft magnetic materials are needed, especially in high temperature applications. Recent research has looked into the nanocrystallization of amorphous alloys of FeCo and very briefly into the oxidation of FeCo nanoparticles and bulk materials. Attempts will be made to more carefully investigate the oxidation of FeCo and its alloys utilizing nanoparticles, and thin films with (100), (110), and (211) texture to observe the kinetics of oxidation. Thin film epitaxial relationships between the substrate and thin films have been determined, and this will be extended to the oxide and thin film. The role of alloying has been discussed, especially in the context of oxidation of FeCo. The composition of the oxide at different oxidizing temperatures is also proposed. FeCo-based nanoparticles have been analyzed to understand their change in magnetization and oxide phase as a function of temperature. The oxide thickness has been measured at various temperatures, along with the observation of a voided core. This research has been coupled with thin film work to show that the core gets richer in cobalt as oxidation progresses, with Fe acting as the mobile species. Oxygen may diffuse early in the oxidation, but only until a certain oxide thickness has been established. The oxidation kinetics seen in the nanoparticles is slower than that seen in thin films, and it has currently been analyzed to follow a logarithmic rate law at lower temperatures. To understand the formation of faceted nanoparticles, nucleation and growth has been modeled for both BCC and FCC systems showing the surface energy ratios necessary to produce different faceting of nanoparticles. It has been shown that the critical nuclei are the same as the growth shapes. To extend the basic science research into the applications field, thin film work on CoCrPt has been performed to achieve out-of-plane anisotropy in thicker films for use in a portable AGFM. While this has been achieved, further study is necessary to improve the remnant magnetization and make it more comparable to SmCo, which is the current standard. The magnetic properties have been measured as a function of temperature and film thickness to begin understanding the system better to produce the desired thin film properties for a biomedical sensor.

Environmental microorganisms are implicated as the causative agents in a significant portion of healthcare associated infections (HAI) and antimicrobial resistant infections (AMR), which result in increased costs and suffering around the world. Furthermore, common environmental microorganisms participate in microbiological degradation of materials and the bio-fouling of various systems. This also results in a tremendous amount of damage in many different materials and many different sectors. The focus of this dissertation was the development of an additive that could be easily added to common materials to make them self-disinfecting and to protect them from microbial damage. The ultimate goal was to develop an additive that could be added using standard techniques and without adversely affecting the final material. Cuprous iodide (CuI) was determined to be an ideal starting material for the development of improved antimicrobial materials because of its neutral appearance and high antimicrobial activity as compared to other silver and copper materials. It was found that the antimicrobial efficacy of CuI could be amplified if prepared as a small particle and especially in the presence of vinylpyrrolidone polymers. A comminution process was then developed to produce these small particles. By using select copolymers, various CuI small particles formulation were developed to be compatible with a variety of different matrices. The efficacy of these CuI containing matrices was dependent on the compatibility of the CuI formulation with the matrix. A variety of applications were demonstrated with good antimicrobial efficacy where the particles were easily added to the finished material with minimal or no change in appearance.

The deposition and characterization of HfO2 films for potential application as a high-k gate dielectric in MOS devices has been investigated. DC magnetron reactive sputtering was utilized to prepare the HfO2 films. Structural, chemical, and electrical analyses were performed to characterize the various physical, chemical and electrical properties of the sputtered HfO2 films. The sputtered HfO2 films were annealed to simulate the dopant activation process used in semiconductor processing, and to study the thermal stability of the high-k films. The changes in the film properties due to the annealing are also discussed in this work.Glancing angle XRD was used to analyse the atomic scale structure of the films. The as deposit films are amorphous, regardless of the film thickness. During postdeposition annealing, the thicker films crystallized at lower temperature 600 C, and ultra-Thin (5.8 nm) film crystallized at higher temperature (600 - 720 C). The crystalline phase which formed depended on the thickness of the films. The low temperature phase (monoclinic) formed in the $10-20$ nm annealed films, and high temperature phase (tetragonal) formed in the ultra--thin annealed HfO2 film. The TEM cross-section studies of as deposited samples show the interfacial layer (&lt; 1nm) exists between HfO2/Si for all film thicknesses. The interfacial layer grows thicker during heat treatment, and grows more rapidly when grain boundaries are present. XPS surface analysis shows the as deposited films are fully oxidized with an excess of oxygen. Interfacial chemistry analysis indicated that the interfacial layer is a silicon-rich silicate layer, which tends to transform to silica-like layer during heat treatment.I-V measurements show the leakage current density of the Al/as deposit-HfO2/Si MOS diode is of the order of 10^{-3} A/cm^2, which is two orders of magnitude lower than that of ZrO2 film with similar physical thickness. Carrier transport is dominated by Schottky emission at lower electric fields, and by Frenkel-Poole emission in the higher electric field region. After annealing, the leakage current density decreases significantly as the structure remains amorphous structure. It is suggested that this decrease is assorted with the densification and defect healing which accures when the porous as-deposited amorphous structure is annealed. The leakage current density increases of the HfO2 layer crystallizes on annealing, which is attributed to the presence of grain boundaries. C-V measurements of the as deposited film shows typical C-V characteristics, with negligible hystersis, a small flat band voltage shift, but great frequency dispersion. The relative permittivity of HfO2/interfacial layer stack obtained from the capacitance at accumulation is 15, which corresponds to EOT (equivalent oxide thickness)= 1.66 nm. After annealing, the frequency dispersion is greatly enhanced, and the C-V curve is shifted toward negative voltage. Reliability tests show that the HfO2* 0films which remain amorphous after annealing possess superior resistance to constant voltage stress and ambient aging.This study concluded that the sputtered HfO2 films are amorphous as deposited. The postdeposition annealing alters the crystallinity, interfacial properties, and electrical characteristics. The HfO2 films which remain amorphous structure after annealing possess the best electrical properties.

Ammonia-peroxide mixture (APM) is a widely used wet chemical system for particle removal from silicon surfaces. The conventional APM solution in a volume ratio of 1:1:5 (NH4OH:H2O2:H2O) is employed at elevated temperatures of 70-80 °C. At these temperatures, APM solution etches silicon at a rate of ~3 Å/min, which is unacceptable for current technology node. Additionally, APM solutions are unstable due to the decomposition of hydrogen peroxide and evaporative loss of ammonium hydroxide resulting in the change in APM solution composition. This has generated interest in the use of dilute APM solutions. However, dilution ratios are chosen without any established fundamental relationship between particle-wafer interactions and APM solutions.Atomic force microscopy has been used to measure interaction forces between H-terminated Si surface and Si tip in APM solutions of different compositions. The approach force curves results show attractive forces in DI-water, NH4OH:H2O (1:100) and H2O2:H2O (1:100) solutions at separation distances of less than 10 nm for all immersion times (2, 10 and 60 min) investigated. In the case of dilute APM solutions, the forces are purely repulsive within 2 min of immersion time. During retraction, the adhesion force between Si surface and Si tip was in the range of 0.8 nN to 10.0 nN. In dilute APM solutions, no adhesion force is measured between Si surfaces and repulsive forces dominated at all distances. These results show that even in very dilute APM solutions, repulsive forces exist between Si surface and particle re-deposition can be prevented.The stability of APM solutions has been investigated as a function of temperature (24 - 65 °C), dilution ratio (1:1:5 - 1:2:100), solution pH (8.0 - 9.7) and Fe2+ concentration (0 - 10 ppb) using an optical concentration monitor. The results show that the rate of H2O2 decomposition increased with an increase in temperature, solution pH and Fe2+ concentration. The kinetic analysis showed that the H2O2 decomposition follows a first order kinetics with respect to both H2O2 and OH- concentrations. In the presence of Fe2+, hydrogen peroxide decomposition follows a first order reaction kinetics with respect to H2O2 concentration.