Search

Considering factors such as the ageing population, growing demand for mobility at later stages in life, and co-morbidities such as obesity, the incidence of joint replacements will rise considerably in the next decades. However, the enormous mechanical mismatch between orthopaedical titanium implants and bone tissue has a critical impact on the integration of the device in the living tissues, leading to abnormal bone resorption and implant loosening. Because the life-in-service of titanium implants is typically limited to 25 years, secondary surgical revisions are a common occurrence and have a low rate of success compared to the primary surgeries, increasing the rate of mortality among the patients and placing an immense financial burden on the national healthcare system. In this dissertation two different approaches were used to improve the mechanical and osteointegrative properties of titanium implants aiming to increase their life-in-service. These approaches involved the control of the pore size, porosity and alloy composition respectively. The biological properties of these replacements were tested using a murine osteoblast cell line MC3T3-E1 established from mouse calvaria. Addressing the first approach, porous titanium scaffolds were manufactured via powder metallurgy and space holder technique in two different porosities (55% and 70% vol.) to replicate the microstructure of cortical and trabecular bone respectively. Thus, the impact of pore sizes ranging from 45 to 500 μm, were found to influence the biological response of MC3T3-E1 pre-osteoblast cell line in different ways depending on the size of the pore. The results suggest that 70% of porosity scaffolds benefit the osteoblasts differentiation in single pore size scaffolds. Moreover, an increase in transcription of gene marker osteocalcin was detected in pores ranging from 300 to 500 μm. Among the 55% porosity scaffolds, pore size ranging from 106 to 212 μm exhibited good osteogenic performances. Therefore, these two pore size ranges were identified as the most performant. In particular, extensive osteogenic properties were displayed when pores ranging from 300-500 and 106-212 μm were combined in multimodal porous scaffolds. Our results demonstrate that, even though pore size and porosity are dependent on each other, they must be considered as separate structural parameters, as the combination of these two variables influences the general outcome of the implant performances. To deal with the second approach, three innovative titanium alloys were designed using Nb and Sn as alloying elements. Tin (Sn) is a cost-effective and promising alloying element which is often combined with Niobium (Nb) to produce alloys with mechanical properties closer to bone. However, little attention has been paid to the effect of Sn and the combination of Sn and Nb on osteoblastic behaviour. The results showed that the binary Sn and ternary Sn-Nb alloys supported cell differentiation and metabolism, demonstrating the suitability of Sn as an element to enhance the performance of titanium implants. The outcome from this research intends to provide guidelines to increase the life-in-service and successful implantation of orthopaedic load-bearing replacements and minimise the need for revision surgeries, yielding overall benefits to the patient's quality of life, the healthcare system, and to society.

This thesis describes selected reactivity studies of the N-heterocyclic carbene, IPr, towards a range of main group compounds. The synthesis and characterisation of sixty-three compounds, all of which incorporate IPr as a ligand in one of three coordination modes, are detailed herein. The deprotonation of IPr allowed for the isolation of an anionic source of the aIPr: ligand which was synthesised as a novel potassium salt and along with the previously reported lithium salt, was employed in reactions with group 12 and 14 bis(trimethylsilyl)amides and tetrahalides. The further chemistry of such novel products was investigated towards both electrophilic and nucleophilic reagents making use of both the pendant nucleophilic carbene functionality and the electrophilic main group centre. An alternative route to such species was investigated by the spontaneous isomerisation of IPr in the coordination sphere of group 14 tetrabromides and group 15 tribromides. The scope of this reactivity was subsequently investigated and was found to provide a simpler route to access the abnormal coordination mode of IPr. The aIPr ligand which is generated may be deprotonated by additional IPr thereby affording aIPr: ligands. The addition of halide abstracting agents allowed for the synthesis of cationic species stabilised by the coordination of either IPr or aIPr ligands. A unique, spontaneous reductive coupling of two phosphorus centres was discovered to take place upon heating a THF solution of (IPr)PBr3. This allowed for the isolation of a bromide bridged P–P bond with reduced phosphorus centres. This facile reduction chemistry was further explored by reaction with mild reducing agents which provide access to low oxidation state phosphorus compounds in high yields. This chemistry was found to be possible (and more effective) due to the presence of the weaker phosphorus bond to bromine relative to the commonly employed chlorine ligands.

The physics of two-phase systems is explored here, particularly magneto-transport and low temperature d.c. conductivity in thin films. The extraordinary magnetoresistance (EMR) effect was analysed in the context of previous experimental and theoretical considerations. The magnetoresistance (MR) may be enhanced by up to two orders of magnitude by changing the geometry. This was investigated using finite element analysis. Thin film samples consisting of a layered structure of Germanium-Tin-Germanium (Ge-Sn-Ge) were created in collaboration with Shandong University in China. Ge layers were kept at a constant thickness across all samples, with variable Sn thickness. Regions of Sn form island-like shapes ten times larger than the average film thickness, as is seen in scanning electron microscope (SEM) images. Raman spectroscopy was conducted on these samples, from which it is concluded that the Ge layers are amorphous in nature. It was seen that there is a relationship between the electrical resistance and the film thickness which is indicative of a metal-insulator transition (MIT). The temperature dependence of resistivity was subsequently investigated. The temperature coefficient of resistivity (TCR) of the samples is seen to become negative as the thickness of the Sn layer is reduced below a certain critical thickness. Depending on their thickness, samples were designated as metallic or insulator, and various models associated with metals and insulators fitted to the data. While it is impossible to be absolutely certain of the validity of each of the models, some are a better fit than others. The same temperature dependence of resistivity was measured with an applied magnetic field. This is compared with the previous EMR investigation, however the MR of the samples is only of the order of a few percent which corresponds to ordinary MR, seen in most metals. The magnetic field measurements suppress a resistivity down-turn at very low temperatures (T < 10K) which suggests the presence of superconductivity. Analysis of dr=dT shows that the onset of superconductivity is lower for samples with a lower Sn thickness. Additionally, the deposition rate of the Sn layer affects the resistivity significantly; a higher deposition rate causes a decrease in resistivity. It is supposed that this is due to a change in the microstructure of the film. Finally, piezo-resistivity was considered by applying mechanical compression to the samples. The added pressure causes a drop in resistivity.

Abstract: Microalloyed steels are high strength steels with low alloying additions of Ti, Nb, and V. These microalloying elements form carbonitride precipitates during thermomechanical controlled processing (TMCP), which enhance the mechanical properties of steel. TiN is one of the first precipitates to form during steel production. It forms in the liquid during solidification and is coarse. It can also precipitate with other elements and form TiN-rich precipitate complexes. A precipitate analysis was performed to quantify and characterize two types of coarse titanium precipitates in seven titanium rich microalloyed steels. The steels varied in titanium (Ti) and niobium (Nb) contents, ranging from 0.047 – 0.122 wt% Ti and 0.015 – 0.088 wt% Nb. The Ti precipitates studied were titanium nitride (TiN) precipitating on calcium sulfide (CaS) inclusions and TiN-rich precipitates that have Nb precipitating on them, forming (Ti,Nb)N. Electron microprobe analysis (EMPA) mapping of the steel samples was undertaken to quantify the prevalence of TiN nucleation on CaS inclusions and Nb on TiN to form (Ti,Nb)N. Elemental maps for Ti, Nb, Mn, Ca, and S were generated through the thickness of the microalloyed steels. Each elemental map consisted of approximately 300,000 – 900,000 pixels. The greyscale intensity and location of each element through the thickness of the strips were obtained using a custom developed code. The greyscale elemental maps were correlated with EMPA line scan data to quantify the greyscale intensities into an approximate wt% value. For a given Ti pixel concentration, co-precipitates of TiN and CaS, including spatial locations, were counted. It was found that the total amount of TiN-CaS precipitates was relatively low compared to the total amount of Ti precipitates in the sample. For the amount of CaS inclusions in the samples, approximately 85-90% were nucleation sites for TiN and formed TiN-CaS precipitates. Steels with higher Ti contents (4372, 4175, and 4280) exhibited the largest amounts of TiN precipitating on CaS inclusions. Most TiN-CaS precipitates were found at the steel quarter thickness or near the surface. Similarly, for a given Ti and Nb pixel concentrations, co-precipitates of Ti and Nb, including spatial locations, were counted. For (Ti,Nb)N, steels 4372 and 4280, which had the highest Ti and Nb concentrations exhibited the largest counts. The number of (Ti,Nb)N throughout the thickness of the steels was almost constant in all samples. Scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy were used to verify the presence and composition of TiN-CaS assemblages and (Ti,Nb)N at a number of specific locations in the steels. SEM was also used to capture micrographs of Ti precipitates to develop size distributions. A size analysis was done on sample 4280 to explore the difference in size between TiN/(Ti,Nb)N and TiN-CaS. The analysis showed that TiN that nucleated on CaS inclusions was approximately 4 μm larger than TiN or (Ti,Nb)N that nucleated on its own. Another size analysis was performed on samples 4280, 4175, 4052, and 4093 to study the size difference between TiN and (Ti,Nb)N. Results showed that (Ti,Nb)N particles were approximately 1.6 μm in size, and TiN particles were approximately 2.7-3.8 μm in size. The size of TiN was constant across the different samples.

Organic frameworks with rigid backbones, such as acenaphthene, are highly suitable for the study of interatomic interactions. The short “natural” peri-distance (2.44 Å) and the rigidity of the aromatic system causes considerable steric strain between peri-substituted heteroatoms. As a consequence, substitution at both peri-positions leads to in- and out-of-plane distortions, which often result in buckling of the ring system. In order to relax this geometric strain, weak bonding interactions can also exist between the peri-substituents. This thesis focuses on the synthesis, structural characterisation and investigation of a range of sterically crowded peri-substituted acenaphthene compounds. This involves the study of the acenaphthene geometry, through X-ray crystallography when different peri-substituents occupy the close 5,6-positions; our main focus is to study weak non-bonded interactions that can occur across the peri-gap, for example weakly attractive three-centre four-electron (3c-4e) type interactions which are known to prevail in such compounds under the appropriate conditions. Repulsion within these systems, resulting from the steric crowding of the peri-space is also investigated, employing changes in bond lengths, bay-region angle splay, displacement of atoms from the mean plane and central acenaphthene torsion angles to help quantify the degree of acenaphthene distortion, which are all conveniently probed by the peri-distance. To this end we have synthesised a range of novel sterically crowded mixed bromo-tin acenaphthene derivatives (Chapter 3), chalcogen-tin acenaphthene molecules (Chapter 4), phosphorus–tin derivatives (Chapter 5) and a series of homologous tin-tin acenaphthenes (Chapter 6). All the compounds studied in this thesis were characterised by multinuclear NMR spectroscopy and X-ray crystallography in an effort to gain a greater understanding of the deformation that occurs when disparate functionalities are located in close proximity and explore the potential for weak non-covalent intramolecular interactions to occur.

This research project offers new knowledge in the field of artificial patination and extends the application of colour to metals that have previously not been exploited for their colouring properties, specifically pewter and its main constituent, tin. The investigation defines, refines and applies new and evolved processes and techniques that provide novel opportunities for both craft and industry through the development of new products, particularly jewellery and tableware items. The thesis details the actions taken to substantiate the hypothesis that pewter and tin may be coloured by chemical means. This includes the interpretation, exploitation and creative application of developed processes to the design and production of new works. It also discusses the research method applied and the rationales that have informed decision making. The research project is reviewed in separate chapters discussing each phase of the investigation. These phases are:  The selection, testing and analysis of chemical colouring processes within the workshop and laboratory.  Investigation into working properties of the coloured material and surface pattern development.  The creative application of outcomes from the above two phases to new works.  Evaluation of the research outcomes in relation to creative practice and their potential for wider commercial application The chemical exploration and design development phases of the research have been conducted in association with the International Tin Research Institute (ITRI Ltd) and the manufacturing industry, which has confirmed the validity of results. The model of collaboration adopted and associated outcomes are also discussed. Finally, the thesis considers the impact of the research outcomes on the material, creative practice and implications for further investigation including the potential for wider commercial application of the patination procedures developed.

Artefacts relating to tin smelting from tin mills or 'blowing houses' in Devon and Cornwall, plus material from smelting sites that cover a range of dates from the Bronze Age through to the 19th Century, were examined: these include metallic tin, furnace linings, ore samples and slag. Analysis of tin slags from over forty sites was carried out, to determine microstructure and chemical composition. Techniques employed included optical and scanning electron microscopy, X-ray fluorescence and ICP mass spectrometry. Analysis indicates that slag appearance and composition are heavily influenced by local geology. Composition, particularly iron content, is shown to have a strong effect on slag melting point and viscosity, and the implications for the purity of metal produced are discussed. Bringing together the evidence provided by slag chemistry, documentary sources and smelting remains in the archaeological record, changes in tin smelting technology through time, and the consequences thereof, are considered.

Materials with potential for high temperature inorganic pigment applications (e.g. ceramics) have been synthesised using solid state methods and characterised using powder X-ray and neutron diffraction, magic angle spinning NMR, Mossbauer spectroscopy, UVNis spectroscopy and colour measurement techniques. A number of compounds containing tin (H) and niobium (V) have been modified and doped with various constituents to tailor and widen the colour properties of the bright yellow parent phases. The dark yellow (L*(91.28), a*(13.74), b*(54.76)) tin niobium oxide pyrochlores have been re-characterised using neutron diffraction techniques. These materials exhibit both cation and anion disorder caused by a stereoactive lone pair on the tin (H) metal centres. Solid state NMR and Mossbauer studies have shown the presence of tin (IV) on a symmetric site within the primary phase of the pure oxide pyrochlore and methods have been investigated to minimise the tin (H) disproportion method from where the tin (IV) is derived.

Detailed, accurate measurements of critical current density and resistivity to determine the upper critical field have been made on a technological NbsAl conductor in magnetic fields up to 15 T, temperatures from 4.2 K up to the critical temperature and in the strain range from -1.8% to 0.7%. The uncertainty in temperature above 4.2 K was equivalent to ± 100 mK with a stability during the measurements of < 5 mK up to a limiting current of 80 A and a typical noise level of 1 µ Vm(^-1).When B(_c2){T,ε) is defined at 5%pn, 50%pn or 95%/%pn, an empirical relation is found where and an approximate relation, holds. The Jε data were parameterised using F(_p) = J(_E)B = A(ε)[Bc(_2)](^n)b(^p)(1-b)(^9) where b = B/B(_c2)(T,ε). When B(_c2)(T,ε) is constrained to be the value at 50%pn or 95%pn, the scaling law for F(_p) breaks down such that p and q are strong functions of temperature and q is also a strong function of strain. However, when B(_c2)(T,ε) is defined at 5%pn, there is good scaling where p and q are constants independent of temperature and strain. F(_p) can also be approximated by a Kramer form where the Ginzburg-Landau constant is γ is the electronic density of states and is interpreted as the average B(_c2) for the bulk where percolative current flow occurs. The critical current density of Hot Isostatic Pressed (HIP'ed) and unHIP'ed Nb(_3)Sn Modified Jelly Roll wires has also been measured at 4.2 K. The critical current and upper critical field were decreased for the HIP'ed sample. The reduced upper critical field of the HIP'ed wire was found to be less sensitive to strain than the unHIP'ed wire. The exponent of B(_c2) in the flux pinning scaling law increased from 0.86 to 2.14 as a result of the HIP processing.

In this study, the anti-plaque activities of amine and tin fluorides were investigated in laboratory models that were designed to simulate specific components of microbial ecology in the oral cavity. The efficacy of the agents applied topically in the form of a solution was determined. The influence of growth mode and sucrose on the bactericidal activity towards Streptococcus sanguis was determined using a constant depth film fermenter (CDFF). S. sanguis cultures growing as biofilms were less susceptible to the amine fluorides than planktonic cultures. When sucrose was added to the growth medium, the susceptibility of both planktonic and biofilm cultures were reduced. The smallest kills, which were measured in sucrose-grown biofilms, were not significantly different from control groups. Inorganic fluorides had no bactericidal effect on S. sanguis biofilms regardless of the presence of sucrose in the growth medium. The CDFF was also used to investigate the effect of olaflur/tin fluoride on the formation of microcosm biofilms over a 12 hour period. In the absence of sucrose, the structures of control and test group biofilms were observably different. A parallel flow cell system was developed to investigate the anti-adhesion properties of the amine and tin fluorides. The effect on the net adhesion of S. sanguis to mucin-conditioned surfaces over a one hour period was determined. Only one of the amine fluorides tested was able to reduce the net adhesion of S. sanguis over a one hour period. Tin (II) and tin (IV) fluorides were found to reduce the net adhesion after one hour of culture flow. The flow cell system was also used to investigate the effects of olaflur/tin fluoride on bacterial desorption and co-adhesion. The amine/tin combination had no effect on either the level of Streptococcus gordonii desorption, or the co-adhesion of the streptococci with Actinomyces naeslundii. In summary, the study has shown that the CDFF model was useful in determining the effect of anti-plaque agents on the susceptibility of intact biofilms of oral bacteria. The parallel flow cell system was a good model for investigating processes involved in adhesion of oral bacteria to conditioned surfaces and enabled the determination of the effects of the anti-plaque agents on bacterial adhesion, desorption and co-adhesion. Additionally, the system allowed the comparison of the substantivity of the different anti-plaque agents.

This thesis is concerned with theoretical calculations of the properties of electronic bound states in semiconductor heterostructures. The complex band structure empirical pseudopotential method (EPM) is used as the foundation of the work. Spin orbit coupling and strain effects (due to lattice mismatch) are included in familiar ways, as is the transfer matrix method, allowing the study of arbitrarily configured heterostructures. These techniques are used to investigate the unusually deep InAs/AlSb conduction band well. The strong possibility of intraband transitions at electro magnetic wavelengths around 1.55µm is predicted, with corresponding enhanced momentum matrix elements and joint density of states over interband transitions. An InAs/GaSb/AlSb asymmetric well is investigated, paying particular attention to the bound states in the vicinity of the InAs/GaSb band overlap. The electron-like states are found to cross with heavy hole and anti-cross with light hole-like states, as a function of heterostructure dimension or applied electrostatic field. This is analogous to the hybridisation of states in the in-plane band structure, except that for zero in-plane wave vector there can be no appreciable hybridisation of electron and heavy hole states. A technique is described that has been developed to extract envelope functions from heterostructure wavefunctions calculated using the realistic complex band structure EPM approach. These envelope functions conform to Burt’s theory (M. G. Burt, J. Phys.: Condens. Matt. 4, 6651 (1992)) in that they are uniquely defined, continuous and smooth over all space. Comparisons with traditional effective mass envelope functions are made. The extracted envelope functions are used to demonstrate conclusively Burt's predictions (M. G. Burt, Superlatt. Mi- crostruct. 17, 335 (1995)) concerning the inadequacy of certain approximations for the calculation of interband dipole matrix elements and charge oscillation. Finally, the issue of k • p operator ordering is convincingly settled, in favour of 'ordered' over 'symmetrised' Hamiltonians, by comparison to EPM calculations, and using EPM derived k • p parameters.

Abstract: The work in this Thesis strives to form a bridge in the understanding between the thriving field of Main Group element stabilization with N-heterocyclic carbenes and developments in thin film deposition for technological applications. Previous work in the Rivard group has excelled at applying Lewis acid-base stabilization to isolate reactive intermediates of Group 14 hydrides, and the work in this Thesis builds upon these established synthetic methods and framework to controllably liberate germanium and tin hydride moieties for pure element thin film deposition at low temperatures in solution. The first research Chapter in this Thesis presents a synthetic method for the isolation of a high wt% germanium complex using an N-heterocyclic carbene. This germanium complex undergoes thermolysis at 100 °C to deposit amorphous Ge thin films on a variety of substrates, most notably silicon wafers. The germanium complex and similar derivatives were investigated experimentally and computationally, with decomposition occuring through direct cleavage of dative bonds to release Ge and soluble by-products. In the following Chapter, N-heterocyclic carbenes prove to be a hinderance in the hydrogermylation of germanium alkoxides en route to semi-crystalline germanium thin films. The germanium alkoxide studied is able to produce two interesting materials when combined with a mild hydride source: 1) a branched oligogermane is obtained with a remarkable degree of hydride substitution at germanium and 2) thin microcrystalline Ge0 films which can be controllably deposited at low temperatures. Finally, an analogous tin alkoxide species is shown to undergo rapid hydrostannylation at room temperature to give crystalline Sn.

Abstract: Microalloyed steels derive their superior properties from the introduction of microalloying elements (titanium (Ti), niobium (Nb), and vanadium (V)). These elements form various carbonitride particles at different stages of production. Titanium nitride (TiN) has the lowest solubility limit in the liquid and solid, resulting in the formation of coarse TiN-rich particles (micron size) in the liquid during solidification and fine TiN-rich particles (some tens of nanometers in size) in austenite. The coarse TiN-rich particles decrease the toughness of microalloyed steels by acting as initiation sites for cleavage cracks. Conversely, the fine TiN-rich particles increase the toughness of microalloyed steels by hindering austenite grain growth during homogenization and welding. This study considers the effect of Ti and N concentrations on the sizes, compositions, and volume fractions of the coarse and fine TiN-rich particles in several as-rolled steels. Also, the type of precipitates in an as-cast steel was studied. Scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) analysis was used to measure the sizes and compositions of the coarse TiN-rich particles. Scanning transmission electron microscopy (STEM) equipped with EDX was employed to measure the sizes and compositions of the fine TiN-rich particles. Matrix dissolution was performed to extract the coarse and fine TiN-rich particles and measure the concentration of Ti in the matrix through inductively coupled plasma (ICP) analysis of the supernatant solutions. Quantitative X-ray diffraction (QXRD) analysis was conducted on the XRD patterns of the particles extracted via matrix dissolution to measure the volume fractions of the particles. The Scheil-Gulliver solidification model was employed to gain insight into the coarse TiN-rich particle characteristics. The results showed that an increase in the product of the nominal Ti and N concentrations led to an increase in the size and volume fraction of the coarse TiN-rich particles. The compositional analysis indicated that the coarse TiN-rich particles were not pure TiN but contained Nb. The amounts of Ti and N bound in the coarse TiN-rich particles were subtracted from the nominal concentrations to obtain the adjusted Ti and N concentrations. An increase in the product of the adjusted Ti and N concentrations led to a decrease in the size and an increase in the volume fraction of the fine TiN-rich particles. The compositional analysis indicated that the fine TiN-rich particles contained a larger concentration of Nb in comparison with the coarse TiN-rich particles. The characteristics of the coarse or fine TiN-rich particles at the quarterline and centerline locations were compared, and no significant differences were observed. The study of the precipitates in the as-cast steel showed that the fine TiN-rich particles were absent in the as-cast steel, indicating that they form during the reheating (homogenization) stage. The measured volume fractions of the coarse TiN-rich particles were in good agreement with the predicted values obtained using the Scheil-Gulliver solidification model, except for the steel with the lowest nominal Ti and N concentration product.

There is not much research done regarding metal oxide and graphene composites. However, there have been some studies done regarding zinc oxide and graphene, and this paper delves into research done regarding tin (IV) oxide, magnesium oxide, and iron (III) oxide to add to the ever-growing body of scientific research. These metal oxides were synthesized from precursors in situ directly onto graphene. Each metal oxide and graphene composite was then analyzed using XPS, while tin (IV) oxide was analyzed using XRD as well. Due to the presence of metal to oxygen to carbon bridges, it has been shown that these composites were successfully synthesized.

Metal-oxo clusters are discrete molecular metal-oxides that are important for applications in catalysis, medicine, precursors for thin film deposition, flash memory devices, switchable transparent films, and high-resolution nanopatterning, to name a few. There are many factors that control the solution stability of metal-oxo clusters; the internal chemistry of the coordination complex as well as the solution conditions can influence the thermodynamic stability of the species. Currently, there is a lack of understanding surrounding how to best manipulate these factors in order to achieve a specific isomer, geometry, or size of metal-oxo cluster in solution. Therefore, the work presented in this dissertation contains an evaluation of the influence of heteroatoms, caps, ligands, pH, electrochemical potential, metal ion concentration, and counterions on stabilizing metal-oxo clusters. Quantum chemical computations were employed to model tin-based and zirconium-based clusters with varying factors, to determine their hydrolysis Gibbs free energies and electronic structures. Sn-oxo clusters, specifically of Keggin geometry, have been shown to be an excellent photoresist candidate for next-generation extreme ultraviolet lithography manufacturing of advanced integrated circuits. I showed how changing the Sn-Keggin heteroatom, caps, and ligands impact the stability ordering of the five known Keggin isomers. This Sn-Keggin ion represents the only Keggin ion family thus far, that favors the lower-symmetry isomers. The computational results provide a means to isolate a single isomer to promote a pure and stable material for advanced lithography. Zr-oxo clusters, specifically the Zr hexamer, has been shown to be a good node for a metal- organic framework (MOF) which is a 3D porous network that can act as a nanoscale carrying device. However the ”green” manufacturing of Zr-based MOFs requires that the Zr hexamer stabilize in an aqueous solution without organic ligation, which has yet to be successfully accomplished. I examined how the pH, electrochemical potential, metal ion concentration, and counterions all influence the aqueous solution stability of Zr(IV) ions clusters and solids. This study successfully elucidates the magnitude of and reason for the thermodynamic instability of the hypothetical Zr hexamer compared to the ubiquitous Zr tetramer. The knowledge gained from these computational studies on Sn-oxo and Zr-oxo clusters can expedite experimental syntheses through implementation of the strategic tuning of chemistry and solution conditions.

Computational work was performed to support several synthetic projects in the Doerrer lab. The new luminescent cerium complexes [K(THF)6][Ce(OC4F9)4(THF)2] (20) and [K(THF)2][Ce(pinF)2(THF)3] (22) were structurally optimized in the gas phase, and their uncommonly blue-shifted absorption spectra were simulated by TD-DFT. Electronic structure analysis elucidated the 4f→5d transitions responsible for the absorption peaks, showing the involvement of the fluorinated alkoxide ligands in the composition of the donor orbitals. The [pinF]2− ligand was also coordinated to Sn(II) and Sn(IV). The structures of the new compounds [K]2[Sn(pinF)2] (31) and [K]2[Sn(pinF)3] (32) were optimized by DFT and their electronic structures examined, revealing a sterically exposed lone pair in the case of 31, and for 32 showing that its unusually twisted six-coordinate geometry (azimuthal angle ~30°) is maintained in the absence of counterions. Metal-metal interactions were investigated in the diamagnetic lantern compounds [PtM(SOCR)4(OH2)] (R = CH3, M = Mg (1), Zn (56); R = C6H5, M = Mg (2), Ca (3), Zn (4)). 195Pt NMR spectra calculated for these lanterns and the precursor ion [Pt(SAc)4]2− (42) demonstrate the electronic effect of coordinating these Lewis acidic metals to the electron-rich Pt(II) center. Canonical and NBO analyses show that the {PtZn} lanterns 41 and 56 possess dative bonds between Pt and Zn, while Ca and Mg feature purely ionic interactions with Pt. A new class of heterobimetallic lantern complexes of the form [PtM(pipCOS)4(py)] (M = Mn (43), Co (44), Ni (45), and Zn (46)) were synthesized. These species exhibit strong absorption in the visible range that was investigated by DFT. Structural and electronic analyses reveal donation from the lone pair on the piperidine N atom into the delocalized ligand system in the ground state, indicating the potential for LMCT to occur upon excitation. A new bidentate ligand, a condensed thioamide, was bound to a Pt(II) center in the complexes [Pt(ctaPhMe)2] (57) and [Pt(ctaPhMe)2]2− (59). DFT analysis of these and the hypothetical ion [Pt(ctaPhMe)2]− (58) showed that reduction occurs on the ligands themselves, with the added electron density concentrated on carbon atoms in the ring, and that the doubly reduced species exists in the high-spin state.

As the demand for wearable devices and mobile technology is increasing rapidly, a smaller but more powerful integrated circuit (IC) is needed. However, as the chip technology has reached its limit to extend Moore’s law, the 3D packaging technology is currently the most promising way to improve transistor density while fulfilling the downsizing requirement of a silicon chip. Compared to currently applied 2D IC system, one of the most distinctive structures to realize the vertical stacking in 3D IC is the use of microbumps to join the through-Si vias (TSV) vertically. The diameter of microbumps (

Metallic Tin is a promising anode material for lithium ion batteries because of its high energy density, electrical conductivity and market availability. However, Tin based anodes typically experience limited cycle life resulting from extreme mechanical stress during lithiation. The mechanical stress leads to volumetric change and consequent unstable growth of solid electrolyte interface (SEI) during cycling. Nano-sizing is an effective way to reduce mechanical stress and prolong the cycle life of tin based electrode. However, small particle size means numerous difficulties in the fabrication process and might easily lead to agglomeration issues. In this study, free standing tin nanoparticles have been synthesized in-situ on 3D electrodes. Further, mechanically stable carbon based structural modifiers have also been employed to reinforce these electrodes. Best performing composite electrode delivered a high specific capacity of 917mAh/g and a capacity retention of greater than 66% after 150 cycles.

Li-ion batteries are used in many devices, such as in cars, laptop computers, and cell phones. These batteries, however, have a short usable range and a limited life time. Currently, graphite is used as an anode material in most batteries, and even though graphite electrodes have good cycling performance, they have limited specific capacity of 372 mAh/g.Operando spectra of a battery often consists of a strongly overlapping mixture of timedependent and independent resonances due to the compositional complexity. Here I report a new method called Derivative Operando (dOp) that improves the resolution of operando nuclear magnetic resonance (NMR) spectra by removing time independent signals and further distinguishes between time dependent signals associated with formation and removal of species. This approach not only provides better resolution but also more clearly reveals correlations between resonances and the chemical transformations occurring at a specific potential. With the dOp-NMR method we detect the formation of lithium graphite intercalation compounds (GICs), including the signatures of LiC72 and its precursors, which have been previously undetected. We also observe a clear correlation of the dOp 7Li NMR spectra of lithium metal dendrites on the counter electrode to the chemistry of the working electrode.Operando 7Li nuclear magnetic resonance (NMR), ex-situ 7Li magic-angle spinning(MAS) NMR and pair distribution function (PDF) methods are used to investigate theelectrochemical lithiation and delithiation of 60 nm particles of tin. While the structuraltransformation pathways between Li-Sn intermetallics during lithiation and delithiation ofSn nanoparticles are somewhat consistent with the structural evolution of Li{Sn phases expected from the equilibrium binary phase diagram, there are some notable exceptions with the observation of a metastable phase Li2Sn3, and two vacancy rich metastable phases, Li7-zSn3, and Li13-dSn5 during delithiation. The capacity fade of 30 % per cycle is not attributed to particle cracking, but rather to particles losing contact with the carbon/PVDF binder. The disconnecting particles are associated with LixSn phases undergoing large decreases in diameters on delithiation, i.e., Sn, Li2Sn5, LiSn, and Li7Sn3. A peculiar behavior of capacity fade in this system is that it only occurs during delithiation. This is explained by a model of disconnecting-reconnecting LixSn-containing particles which remain in the electrode and become reconnected every cycle by the volume increase of neighboring connected particles during the lithiation process.Similarly, I use operando 7Li NMR and ex-situ 7Li MAS NMR techniques to obtain abetter understanding of the lithiation and delithiation mechanisms of Sn oxides. I found that the cycling of SnO behaves similar to b-Sn after the initial reduction reaction, including the formation of vacancy rich phases. The electrochemical reduction of SnO2, however, results in a metallic form of Sn that lithiates differently than b-Sn, with the absence of some intermetallic phases with low lithium content like Li2Sn5, LiSn and thus, resulting in better cyclability. This is somehow contradictory to previous thoughts that SnO2 should cycle identical to -Sn after the first reduction reaction.

Metallized plastic packaging waste (MPPW) and automotive plastic waste (APW) are two of the most complicated plastic wastes that generated in modern society. They are difficult to be recycled in conventional ways due to their complex combination of various polymeric materials, metals, plastic additives and contamination. This thesis provides innovative approaches to transform them into value-added resources through thermal transformation, thermo-delamination, and steel surface hardening techniques. Valuable Al3C4 nano particles and AlN nano wires with an exceptional length up to tens of millimetres and a diameter of around 102 nm, are successfully synthesized from MPPW via thermal transformation within 600 oC to 1500 oC. High-quality aluminium foil with purity up to 95 wt.% is isolated from metallized plastic packaging waste as the thermo-delamination of polymeric materials and aluminium component occurred in the temperature range of 500 -700 oC. Sustainable steel carburization is achieved by using metallized plastic waste as a carbon resource via plastic gasification and steel gas carburization at temperature of 1200 oC. In this approach, the waste plastics are decomposed into small molecular carbon rich reducing gases, like CO and CH4, that in turn work as carburization agents for steel carburization. In addition, TiN thin film in nanoscale thickness of 18 nm is successfully deposited on steel substrate by using automotive plastic waste as resources. APW is more complicated in nature as it contains almost all kinds of thermoplastics, rubbers, and thermosets along with other additives like silica, titanium dioxide etc. In this work, the plastic additive titanium dioxide in APW is utilized as a titanium resource, the polymeric materials it contains work as carbon resources for carbothermal reduction of titanium dioxide, and the nitrogen from the working atmosphere is used as a nitridation agent. The sustainable approaches developed in this thesis not only achieve fabrication of a series of high-value products from plastic waste but also benefit environmental sustainability by reduction of waste accumulation.

Optical heating has numerous applications, such as cold weather clothing, heat generation for homes, and solar thermal generation of electricity. One form of this optical heating technology is the fabrication of poly (methyl methacrylate) polymer thin films with embedded nanoparticles, such as titanium nitride and carbon black. MATLAB was used to simulate samples, in order to determine the optimal configuration for most heat generated. The optimal configuration was carbon black nanoparticles with a radius of 900nm, packed closely together (1800 nm apart), in a medium such as aerogel with low thermal conductivity, with a maximum mass of carbon black and minimal thickness of the sample.

Synthesis and Structural Chemistry of Diamagnetic Dimeric Metal PhthalocyaninesAbstractbyBENJAMIN WALDEN STURTZ Syntheses have been developed for 18 new, cofacial, oxygen-bridged, metal phthalocyanine dimers: Me3SiO[SiPcO]2SiMe3, Et3SiO[SiPcO]2SiEt3, Pr3SiO[SiPcO]2SiPr3, PrMe2SiO[SiPcO]2SiMe2Pr, BuMe2SiO[SiPcO]2SiMe2Bu, (i-Bu)3SiO[SiPcO]2Si(i-Bu)3, ThMe2SiO[SiPcO]2SiMe2Th, OdMe2SiO[SiPcO]2SiMe2Od, Ph3SiO[SiPcO]2SiPh3, Ph3SiO[Si0.75Ge0.25PcOSiPcO]SiPh3, Hx3SiO[SiPcOGePcO]SiHx3, Hx3SiO[SiPcOGePcO]SiPh3, Et3SiO[GePcO]2SiEt3, BuMe2SiO[GePcO]2SiMe2Bu, (i-Bu)3SiO[GePcO]2Si(i-Bu)3, Hx3SiO[GePcO]2SiHx3, Ph3SiO[GePcO]2SiPh3, and [GaPc]2O. The structures of these dimers have been determined by single-crystal X-ray crystallography. From the structure data gathered, the distances between the metal centers, the distances between the phthalocyanine ring centroids, and the torsion angles between the phthalocyanines rings have been extracted. The results lead to the conclusion that for centroid-centroid distances of approximately 3.30 Å to 3.40 Å the torsion angles are governed by long distance bonding interactions, LDIs. For distances of approximately 3.40 Å to 3.60 Å the angles are governed by the results of a competition between long distance bonding interactions and crystal packing forces, and for distances above approximately 3.60 Å the angles are governed by crystal packing forces. The known centroid-centroid distance and torsion angle of the cofacial polymer [GaPcF]n further support the governance of the torsion angles in cofacial phthalocyanine systems by a balance of LDI bonding and crystal packing forces. Exploratory structural work on HO[Si(OEP)O]2H and Od(i-Bu)2SiO[SiNcO]2Si(i-Bu)2Od has given data consistent with the existence of preferred torsion angles in these smaller and larger cofacial aromatic systems.