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Iron platinum (FePt) has attracted growing interest because of its high Curie temperature, magneto-crystalline anisotropy and chemical stability. Nanoparticles (NPs) made of this alloy are promising candidates for a wide range of biomedical applications including magnetic separation, magnetic targeted drug delivery, hyperthermia for cancer therapy and also as magnetic resonance imaging (MRI) contrast agents. This thesis presents the synthesis, functionalization and characterization of FePt NPs along with a toxicity study and an investigation into their application as MRI contrast agents. Regarding their synthesis, different approaches have been explored including the co-reduction of Fe and Pt precursors in an aqueous media, the thermal decomposition in a conventional high-boiling solvent such as benzyl ether, and in low-melting organic salts (ionic liquids). The data revealed an inhomogeneous composition distribution of Fe and Pt between particles obtained in aqueous media, due to the iron salts hydrolysis, and a mismatch in the co-reduction kinetic of the two metal precursors. While the iron content in the NPs could be increased by using more hydrolytically stable iron precursors or stronger reducing agents, there are remaining limiting parameters which prevent further Fe content increase in NPs. In contrast, by excluding the water from the reaction system and using a Fe²⁻ iron precursor, homogenous 1:1 Fe to Pt ratio NPs can be obtained through a modified thermal decomposition pathway in benzyl ether. Based on the study of synthesis in this conventional chemical, the potential of ionic liquids (ILs) to be used as novel solvents for FePt NPs synthesis was further explored. It was then demonstrated that ionic liquids (ILs) can not only be used as a solvent for synthesis of FePt NPs, but also can provide an exciting alternative pathway to direct synthesis fct-FePt NPs. In the context of the bioapplication of FePt NPs, a family of FePt NPs was specifically designed to enhance their MRI contrast agents properties. In contrast with previous reports, this thesis demonstrates that FePt NPs can be made non-toxic and provides the first data on their cellular uptake mechanisms. A six times increase in the FePt based T₂ contrast properties compared to clinical iron oxide NPs is reported. The relationship between the MRI contrast properties and the NPs architecture is explored and rationalised as the basis for the design of NPs as enhanced MRI contrast agents. Finally, the first observations of cellular and in vivo MR imaging with FePt NPs is also reported. This study opens the way for several applications of FePt NPs such as regenerative medicine and stem cell therapy, thus providing a bio-platform to develop novel diagnostic and therapeutic agents.

The thesis is primarily concerned with the design, construction and preliminary commissioning of a novel polarimeter for full three-dimensional analysis of electron spin polarisation. The polarimeter is described in detail, together with the theoretical basis for its operation. Studies of an amorphous ferromagnetic alloy, Co66Fe4Ni1B14Si15, and its application as a secondary standard are presented. Finally, a design study of a GaAs polarised electron source, capable of providing both longitudinal and transverse polarisations, is detailed.

Estimations of bulk hardness from nanoindentation are frequently subject to considerable uncertainties due to indentation size effects (ISE), pileup effects, and potential influence of surface quality or test methods. This study examined materials science principles of the nanoindentation test method to enable accurate prediction of bulk hardness from nano scale, and correlated microstructure with mechanical properties. The research started by developing a scientific nanoindentation test protocol on a series of high purity Fe and Fe-(3-25 wt. %) Cr alloys. These materials were tested in as-annealed and thermally aged (100-900 hours at 475 ℃ to produce Cr-rich a’ precipitates) conditions. Nanoindentation with a Berkovich indenter at constant strain rate (0.05 to 0.5 /s) and constant loading rate conditions provided comparable bulk equivalent hardness (H0) extracted by Nix-Gao model, indicating a weak strain rate sensitivity at room temperature. Results from electropolished and fine mechanically polished samples gave comparable measured hardness. Pileup corrections produced a 5-14% correction to H0 which agreed with the experimental bulk Vickers hardness within ~10% for most tested materials. The microstructural model-predicted and measured strength values agreed for aged samples. A derived analytic expression demonstrates that an ISE error, associated with inappropriate methods such as hardness ratios or changes at a reference depth, can be as large as 60% in estimated bulk hardness for the investigated Fe-Cr alloys. Subsequently, the nanoindentation protocol was applied to ion irradiated binary Fe18Cr alloys. The microstructure was characterized by APT, S/TEM and EDS to understand the irradiation effects on the mechanical properties. An accurate way to calculate the strength factor was provided based on the size of the defects. A newly refined hardening model with superposition method was applied to correlate the microstructures with the mechanical properties, which further demonstrated the consistency between model prediction and nanoindentation measurement. This study also provides insight into the fidelity of ion irradiation as a surrogate of neutron irradiation based on the dual ion irradiated and neutron irradiated T91 and HT9 ferritic/ martensitic steels. Microstructures and mechanical properties were quantified and compared according to the protocol developed in the thermally aged and ion irradiated binary alloys.

Earth’s core is impossible to sample or directly observe and yet is fundamentally important to the properties of, and our continued existence on, this planet. Indeed, planetary cores literally underlie every other area of geoscientific inquiry, and core properties controlled the development of Earth, Mars, and likely every other terrestrial planet. As this importance has become evident over the last century, several methods of indirectly investigating planetary cores have been developed. These include the use of mineral physics experiments to measure materials at ultra-high pressures and temperatures, seismic observations to constrain bulk physical properties, and numerical simulations to turn such data into comprehensive models of planetary interiors. In this dissertation, I present results from several studies that combine these methods in various ways to advance our understanding of the formation and evolution of the cores of Earth and Mars. Chapter 1 (General Introduction) gives a brief synopsis of the study of the deep Earth (and Mars). This includes the history of the field, the major research methodologies that appear in subsequent chapters, and the current scientific consensus concerning planetary cores. Chapter 2 (Martian Core Formation and the Geophysical Properties of Deep Mars) presents a simulation of Mars’ growth and core-mantle differentiation, parameterized by metal-silicate partitioning experiments and geophysical data measured by spacecraft. The model was able to reproduce the canonical Martian mantle composition in scenarios where Mars was built from oxidized primordial material that was highly equilibrated in a magma ocean of intermediate depth, resulting in a sulfur-rich core. This model allowed us to evaluate various physical properties of the deep Martian interior and generate predictions of observable seismic properties. We determined that to maintain consistency with measured physical parameters, the core must constitute about half of Mars’ radius, a size later confirmed by the groundbreaking seismic measurements of the InSight mission. Chapter 3 (Timing of Martian Accretion and Core Formation) extends the model described in Chapter 2 by incorporating realistic Martian accretion histories from dynamical simulations of solar system formation and constraints from the hafnium–tungsten (Hf–W) radioisotopic system. The evolution of Mars’ Hf–W signature is sensitive to a variety of accretionary conditions, especially the oxidation of primordial material. With the right conditions, it is possible to match the Martian signature for a variety of accretion histories, including ones which continue for many times longer than the previously supposed maximum growth period. Additionally, there does not appear to be a relationship between the final orbits of Mars-like bodies and the material that formed them. This implies that Mars might have accreted from a single geochemical reservoir somewhere in the protoplanetary disk before being gravitationally scattered to its modern location. Chapter 4 (Deformation Properties of Earth’s Inner Core) presents the results of diamond anvil cell radial X-ray diffraction experiments that investigated the yield strength and deformation texture of alloys similar in composition to Earth’s core. These are the first such experiments on alloys containing a light element, which we found increased alloy strength by up to an order of magnitude. The texture produced upon plastic deformation was consistent with that found by previous studies and believed to exist in Earth’s inner core. However, the enhanced mechanical strength of the alloy may imply that this texture developed by a mechanism other than deformation.

Amorphous alloys have a range of desirable ferromagnetic, electrical, mechanical and chemical properties. For instance, the application of Fe-based soft ferromagnetic amorphous alloys as transformer core materials can cut the transformer core losses to about 1/4, with considerable energy saving. However, during manufacture, heat treatment and in service, amorphous alloys may need to be exposed to moderately high temperatures for a period of time, with possible degradation caused by oxidation and crystallisation. There has been almost no previous study of oxidation behaviour and the relationship between oxidation and crystallisation in amorphous alloys. Eight important amorphous alloys and an industrial crystalline silicon steel have been studied in the present work; amorphous Fe78Si9Bl3, Fe40Ni40B20, Fe40Ni40P14B6, Co58NilOFe5SillB16, Fe32Ni36Crl4P12B6, Co66Fe4NilSil5B14, Co76Fe2Mn4Si6B12 and Ni78Si8B14, and crystalline Fe94Si6. A combination of thermogravimetry, optical and electron microscopy, electron probe microanalysis, X-ray diffractometry and differential scanning calorimetry has been used to investigate the oxidation and crystallisation kinetics, oxide structure and composition, oxidation and crystallisation mechanisms and the effect of crystallisation on the oxidation behaviour. The results show that the oxidation resistance at 350 C in air increases in the order Fe40Ni40- P14B6 < Fe94Si6 < Co66Fe4NilSil5B14 < Co58NilOFe5SillB16 < Co76MnFe2- Si6B12 < Fe40Ni40B20 < Si78Si9B13 < Ni78Si8B14 < Fe32Ni36Crl4P12B6. Most of the amorphous alloys obey a parabolic oxidation rate law, but the oxidation kinetics, oxide growth mechanism and resulting oxide structure change sharply when crystallisation takes place in the amorphous alloys. Amorphous Fe78Si9B13 and Fe40Ni40B20 have better oxidation resistance than the corresponding crystalline alloys, while amorphous Fe40Ni40P14B6 and Co58NilOFe5Sil1B16 have poorer oxidation resistance than the crystalline counterparts. Most of the crystalline alloys also obey a parabolic oxidation rate law, except for the crystalline Co based alloys and Fe40Ni40B20, which obey a logarithmic rate law. In most cases, the amorphous and crystalline alloys oxidise to form a fine-scale multiphase oxide scale, except for amorphous Fe40Ni40P14B6, which oxidises to form a whisker-like thick layer of Fe203- In general, ion diffusion through fast transport paths such as grain boundaries and dislocations is the rate controlling process for oxide growth. Different oxidation kinetics and oxide growth mechanisms in amorphous and crystalline alloys of the same composition are caused by micro-chemical segregation of the alloying elements during crystallisation.

This research is concerned with identifying and characterizing four solid-state precipitation reactions in the W-Ni-Fe system that can be induced by appropriate heat treatments. Previous work in this area is reviewed, and a general overview of the research on this system that may, directly or indirectly, further the understanding of microstructure/mechanical property relationships in the W-Ni-Fe heavy alloy is presented. The many metallographic and analytical techniques that have been employed in the course of this investigation are also briefly reviewed. The specific precipitation reactions studied in the 90W-5Ni-5Fe heavy alloy are listed and briefly described. Interfacial precipitation - interfacial precipitates at the W-andgamma; and andgamma;-andgamma; boundaries were found to be andeta;-carbides. This morphology is expected to severely embrittle the alloy. Matrix-phase precipitation - discontinuous precipitation of W was observed in the matrix region. W-W grain boundary precipitation - W-W grain boundary allotriomorphs (andgamma;-phase) were identified and characterized. W-phase precipitation hardening - fine scale precipitation in the W-phase was found to strengthen the alloy. Deformation prior to aging significantly increased the rate of precipitate nucleation. TEM contrast analysis showed the precipitates to be plate-like with a {100} habit plane, and the strain in the W lattice normal to the precipitates was found to be tensile in nature. Matrix-composition alloys were manufactured to simulate the andgamma;-phase in the 90W-5Ni-5Fe alloy. Metallographic observations of these alloys furthered the understanding of reactions 1) and 2) above. These results are discussed in terms of (a) current theories of solid-state precipitation and (b) the influence of the various morphologies on mechanical properties.

Electroless Deposition of Amorphous Iron-Alloy CoatingsAbstractbyJacob K. BlickensderferAmorphous iron alloys are a potentially benign alternative for replacing nickel-phosphorus films commonly used in electronics and surface finishing applications. In addition to being environmentally friendly, the amorphous iron alloys provide excellent corrosion resistance, solderability and micro hardness. In this work, electroless deposition of two such iron alloys, i.e., iron boron (FeB) and iron phosphorus (FeP), is investigated.A process for electroless deposition of FeB without the use of substrate activation is developed. Mixed potential behavior and polarization behavior of individual half-reactions occurring during electroless FeB deposition are characterized, and then used to elucidate the process conditions necessary for activation-free electroless FeB deposition. Corrosion resistance of amorphous FeB films deposited using this newly developed process is tested and the corrosion current is determined to be 31.1 µA/cm2, which is an order of magnitude lower than that typical of crystalline Fe deposits.Unlike FeB deposition, electroless FeP plating critically needs substrate activation by palladium (Pd). The role of substrate (Cu) activation by Pd in enabling electroless FeP deposition is studied in depth. Specifically, it is demonstrated that a critical Pd surface coverage of 10.6% is essential for spontaneous electroless FeP deposition to commence. Below this critical Pd coverage, the surface is catalytically inactive for FeP deposition. A mechanistic model that incorporates surface heterogeneity due to partial Pd coverage of Cu and the effect of this heterogeneity on electrocatalysis of the reductant oxidation reaction during electroless deposition is presented. Model predictions are compared to experimental observations of the electroless surface mixed potential to gain insights into the mechanism by which Pd catalyzes electroless FeP deposition. Implications of these findings to the optimization of pretreatment and activation processes commonly used in electroless deposition systems is discussed.