This dissertation focuses on two areas of garnet porphyroblast crystallization that have until now remained largely uninvestigated: epitaxial nucleation of garnet porphyroblasts and yttrium and rare earth (Y+REE) uptake in metamorphic garnet. The mechanism of epitaxial nucleation is explored as a step towards determining which aspects of interfaces are significant to interfacial energies and nucleation rates. Garnet from the aureole of the Vedrette di Ries tonalite, Eastern Alps, shows a clear case of epitaxial nucleation in which garnet nucleated on biotite with (110)grt || (001)bt with [100]grt || [100]bt. The occurrence is remarkable for the clear genetic relationships revealed by the microstructures and for its preservation of the mica substrate, which allows unambiguous determination of the coincident lattice planes and directions involved in the epitaxy. Not all epitaxial nucleation is conspicuous; to increase the ability to document epitaxial relationships between garnet and micas, I develop and apply a method for determining whether evidence for epitaxial nucleation of garnet is present in porphyroblasts containing an included fabric. Although the magnitude of uncertainties in orientation measurements for garnets from Passo del Sole (Switzerland), the Nevado Filabride Complex (Spain), and Harpswell Neck (USA) preclude definitive identification of epitaxial relationships, the method has potential to become a viable technique for creating an inventory of instances and orientations of epitaxial nucleation with appropriate sample selection. Using lattice-dynamics simulations, I explore the most commonly documented epitaxial relationship, (110)grt || (001)ms. The range of interfacial energies resulting from variations in the intracrystalline layer within garnet at the interface, the initial atomic arrangement at the interface, and the rotational orientation of the garnet structure relative to the muscovite structure shows that the intracrystalline layer within garnet has the greatest effect on interfacial energy. A complete understanding of the role of intergranular diffusion for yttrium and rare-earth-element uptake in porphyroblastic garnet is critical because the complexities of Y+REE zoning in garnets and the mechanisms of Y+REE uptake have implications for petrologic interpretations and garnet-based geochronology. Y+REE distributions in garnets from the Picuris Mountains (USA), Passo del Sole (USA), and the Franciscan Complex (USA) imply diverse origins linked to differing degrees of mobility of these elements through the intergranular medium during garnet growth.

This study was aimed at understanding the environmental performance of two abrasives, coal slag and garnet which are commonly used by shipyards and many other industries in surface preparation of metallic surfaces. Environmental performance evaluated in this study included, (1) productivity (ft2/hr), (2) consumption and or used-abrasive generation rate (ton/2000 ft2; lb/ ft2), (3) particulate emission factors (mg/ft2; mg/lb; lb/lb; lb/kg; lb/ton). In order to achieve the study objectives, an emission test facility was built and necessary equipment and materials were procured. Blasting was performed on rusted steel panels inside the test facility and emissions were measured using EPA Source Test Method to quantify particulate emissions. By measuring the area cleaned, blasting time, and the abrasive consumed, environmental performance of coal slag and garnet was evaluated. Simple mathematical models were developed to predict performance based on feed rate and blast pressure. Garnet was observed to be more productive, less consuming, and more environmentally-friendly compared to coal slag. These study findings will valuable in reducing costs, improving productivity, and protecting the environment.

The thesis explores preparation and properties of bismuthiron garnet (BIG) films and the incorporation of BIG films intoone-dimensional magneto-optical photonic crystals (MOPCs). Films were prepared by pulsed laser deposition. Weinvestigated or measured crystallinity, morphology,film-substrate interface, cracks, roughness, composition,magnetic coercivity, refractive index and extinctioncoefficient, and magneto-optical Faraday rotation (FR) andellipticity. The investigations were partly performed onselected samples, and partly on two series of films ondifferent substrates and of different thicknesses. BIG filmswere successfully tested for the application of magneto-opticalvisualization. The effect of annealing in oxygen atmosphere wasalso investigated - very careful annealing can increase FR byup to 20%. A smaller number of the above mentionedinvestigations were carried out on yttrium iron garnet (YIG)films as well. Periodical BIG-YIG multilayers with up to 25 single layerswere designed and prepared with the purpose to enhance FR at aselected wavelength. A central BIG layer was introduced asdefect layer into the MOPC structure and generated resonancesin optical transmittance and FR at a chosen design wavelength.In a 17- layer structure, at the wavelength of 748 nm, FR wasincreased from -2.6 deg/µm to -6.3 deg/µmat a smallreduction in transmittance from 69% to 58% as compared to asingle-layer BIG film of equivalent thickness. In contrast tothick BIG films, the MOPCs did not crack. We were first toreport preparation of all-garnet MOPCs and second toexperimentally demonstrate the MOPC principle inmagneto-optical garnets.

Abstract During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3

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During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1300 nm to 1600 nm. The fast increasing demand of communication capacity results in the emergence of wavelength division multiplexing (WDM) technology, enabling tens of channels with different wavelengths transmitted simultaneously on an optical fiber. In consequence, it raises the requirement of spectral bandwidth of all the optical components used in the optical transport networking systems. Cr4+:YAG has potential to meet this demand because its 3T2¡÷3A2 transition has a strong spontaneous emission that just covers the low-loss window of optical fiber. The crystalline host offers a excellent mechanical characteristic. Such a fiber is, therefore, eminently suitable for super-wideband optical source since the required pump power is expected to be higher. We have successfully demonstrated a diode-laser pumped Cr:YAG crystal fiber ASE light source. The crystal fibers are grown by the laser-heated pedestal growth technique. Using a 46.6 mm-long Cr:YAG single crystal fiber of a 3-dB ASE width of 265 nm and a power spectral density ¡V22.1 dBm/nm was achieved. In the future, to further increase the quantum efficiency and output power we will reduce the core diameter, lengthen the fiber, increase the Cr4+ doping concentration, fabricate double-cladding, coat the fiber facets, and improve the cooling system.

<p>The thesis explores preparation and properties of bismuthiron garnet (BIG) films and the incorporation of BIG films intoone-dimensional magneto-optical photonic crystals (MOPCs).</p><p>Films were prepared by pulsed laser deposition. Weinvestigated or measured crystallinity, morphology,film-substrate interface, cracks, roughness, composition,magnetic coercivity, refractive index and extinctioncoefficient, and magneto-optical Faraday rotation (FR) andellipticity. The investigations were partly performed onselected samples, and partly on two series of films ondifferent substrates and of different thicknesses. BIG filmswere successfully tested for the application of magneto-opticalvisualization. The effect of annealing in oxygen atmosphere wasalso investigated - very careful annealing can increase FR byup to 20%. A smaller number of the above mentionedinvestigations were carried out on yttrium iron garnet (YIG)films as well.</p><p>Periodical BIG-YIG multilayers with up to 25 single layerswere designed and prepared with the purpose to enhance FR at aselected wavelength. A central BIG layer was introduced asdefect layer into the MOPC structure and generated resonancesin optical transmittance and FR at a chosen design wavelength.In a 17- layer structure, at the wavelength of 748 nm, FR wasincreased from -2.6 deg/µm to -6.3 deg/µmat a smallreduction in transmittance from 69% to 58% as compared to asingle-layer BIG film of equivalent thickness. In contrast tothick BIG films, the MOPCs did not crack. We were first toreport preparation of all-garnet MOPCs and second toexperimentally demonstrate the MOPC principle inmagneto-optical garnets.</p>

This dissertation focuses on two areas of garnet porphyroblast crystallization that have until now remained largely uninvestigated: epitaxial nucleation of garnet porphyroblasts and yttrium and rare earth (Y+REE) uptake in metamorphic garnet. The mechanism of epitaxial nucleation is explored as a step towards determining which aspects of interfaces are significant to interfacial energies and nucleation rates. Garnet from the aureole of the Vedrette di Ries tonalite, Eastern Alps, shows a clear case of epitaxial nucleation in which garnet nucleated on biotite with (110)grt / (001)bt with [100]grt / [100]bt. The occurrence is remarkable for the clear genetic relationships revealed by the microstructures and for its preservation of the mica substrate, which allows unambiguous determination of the coincident lattice planes and directions involved in the epitaxy. Not all epitaxial nucleation is conspicuous; to increase the ability to document epitaxial relationships between garnet and micas, I develop and apply a method for determining whether evidence for epitaxial nucleation of garnet is present in porphyroblasts containing an included fabric. Although the magnitude of uncertainties in orientation measurements for garnets from Passo del Sole (Switzerland), the Nevado Filabride Complex (Spain), and Harpswell Neck (USA) preclude definitive identification of epitaxial relationships, the method has potential to become a viable technique for creating an inventory of instances and orientations of epitaxial nucleation with appropriate sample selection. Using lattice-dynamics simulations, I explore the most commonly documented epitaxial relationship, (110)grt / (001)ms. The range of interfacial energies resulting from variations in the intracrystalline layer within garnet at the interface, the initial atomic arrangement at the interface, and the rotational orientation of the garnet structure relative to the muscovite structure shows that the intracrystalline layer within garnet has the greatest effect on interfacial energy. A complete understanding of the role of intergranular diffusion for yttrium and rare-earth-element uptake in porphyroblastic garnet is critical because the complexities of Y+REE zoning in garnets and the mechanisms of Y+REE uptake have implications for petrologic interpretations and garnet-based geochronology. Y+REE distributions in garnets from the Picuris Mountains (USA), Passo del Sole (USA), and the Franciscan Complex (USA) imply diverse origins linked to differing degrees of mobility of these elements through the intergranular medium during garnet growth. / text

No description available.

The ¹⁷⁶Lu-¹⁷⁶Hf and ¹⁴⁷Sm-¹⁴³Nd decay systems have been extensively used as geochronological tools to determine ages from garnet (Grt) - whole rock (WR) parent-daughter isotopic ratios; however, the ¹⁷⁶Lu-¹⁷⁶Hf age of garnet is almost always found to be significantly older than the ¹⁴⁷Sm-¹⁴³Nd age determined from the same aliquots. This dissertation presents new experimental diffusion data for Lu and Hf in garnet, and numerical simulations using these data, which explain these age discrepancies and also show that Grt-WR ¹⁷⁶Lu-¹⁷⁶Hf isochrons do not generally yield ages which correspond to an unambiguous temporal event in the evolutionary history of the host rocks. This is a result of (a) partial or complete retention of very slow-diffusing radiogenic ¹⁷⁶HF produced during prograde heating, and (b) the lower closure temperature of Lu relative to Hf; these complexities do not affect the interpretation of Grt-WR isochrons based on the ¹⁴⁷Sm-¹⁴³Nd system. In addition, the diffusion kinetic properties of Hf in clinopyroxene were experimentally determined in order to address the age controversy of the shergottite suite of Martian meteorites (~200 Ma ages determined by ¹⁷⁶Lu-¹⁷⁶Hf, ¹⁴⁷Sm-¹⁴³Nd, and various other decay systems as opposed to a ~4 Ga whole rock Pb-Pb age). This was achieved by calculating the timescales needed to re-equilibrate Hf isotopes in clinopyroxene (the primary host of rare earth elements amongst the minerals used to compose the ¹⁷⁶Lu-¹⁷⁶Hf isochrons) with the surrounding matrix at the peak- and post-shock P-T conditions likely to have been experienced by the shergottites. It is concluded that, contrary to the earlier suggestions, impact heating is highly unlikely to have significantly reset the ¹⁷⁶Lu-¹⁷⁶Hf ages of these Martian samples. These calculations are bolstered by the nature of measured Cr and Fe-Mg concentration profiles across olivine-melt boundaries, and Ti profiles across clinopyroxene-maskelynite interfaces in the shergottite RBT-04262. The lack of any evidence of diffusion in the measured concentration profiles, coupled with the qualitative incompatibility of the measured crystal-melt fractionation at these interfaces with the nature of fractionation expected from equilibrium partitioning, provides strong evidence that no substantial chemical exchange took place between the solid and melt phases during peak-shock P-T conditions.