Nanocrystalline £\-Zr condensates deposited by ion beam sputtering on the NaCl (100) surfaces and then annealed at 100 oC to 750 oC in air. The phases present were identified by transmission electron microscopy to be nanometer-size £\-Zr+ZrO¡B£\-Zr+ZrO+c-ZrO2¡Bc-ZrO2¡Bc-+t-ZrO2¡Bt-ZrO2¡Band t-+m-ZrO2 phase assemblages with increasing annealing temperature. The zirconia showed strong {100} preferred orientation due to parallel epitaxy with NaCl (100) when annealed between 150 oC and 500 oC in air. The c- and t-zirconia condensates also showed (111)-specific coalescence among themselves. The c- and/or t-ZrO2 formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of the neighboring grains.

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Thesis advisor: Yvette D. Kuiper / Crystallographic Preferred Orientations (CPO) are common in deformed rocks, and usually result from crystal plastic deformation by dislocation creep. Whether deformation mechanisms that occur at lower differential stress and lower temperature than dislocation creep, such as Dissolution-Precipitation Creep (DPC), may result in the development of a CPO is less certain. DPC, a process also known as pressure-solution creep or dissolution creep, has caused substantial removal and reprecipitation of quartz within the Purgatory Conglomerate of Rhode Island. The conglomerate is exposed within the southeastern region of the Pennsylvanian Narragansett basin and experienced folding during the Alleghanian orogeny. Strain within the southeastern portion of the Narragansett basin increases from west to east and is associated with a metamorphic gradient from very low grade greenschist facies in the west to the lower biotite zone in the east. Within the Pugatory Conglomerate DPC has led to the dissolution of quartz along cobble surfaces perpendicular to the shortening direction, and to be precipitated as overgrowths at the ends of the cobbles (strain shadows), parallel to the maximum extension direction. This offers a unique opportunity to study the effects of dissolution and precipitation separately, because the quartz grains within the cobbles experienced dissolution only, while precipitation occurred in the strain shadows. Cathodoluminescence (CL) analysis was conducted on regions within the strain shadow in order to determine what amount of the quartz was formed authigenically. The results suggest that quartz-rich areas of the strain shadow were comprised primarily of authigenic quartz and formed channels or wedges. Electron Backscatter Diffraction (EBSD) analysis was used to test whether quartz dissolution processes within the cobbles and/or quartz precipitation within the strain shadows resulted in CPO development. Quartz grain c-axis orientations of various domains within the cobbles and strain shadows indicate that CPO patterns are absent in both domains of dissolution and of precipitation irrespective of the degree of strain or metamorphic grade. The existence of discrete mica selvages along the cobble margins suggests that quartz dissolution only occurred along the cobble surface and did not affect the grains, or result in a CPO, within the cobble's interior. Quartz precipitation within the strain shadows did not result in a CPO, probably because the strain shadows are truly localized regions of low strain with little to no differential stress, allowing quartz grain growth in random orientations. / Thesis (MS) — Boston College, 2010. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Since 2011, the Institute of Petrology and Structural Geology, Charles University in Prague, worked with CIP - Computer Integrated Polarization microscopy as fast, inexpensive measurement of c-axis orientation of uniaxial minerals, mostly quartz in high definition. CIP method is developed from the early nineties in Switzerland (Heilbronner & Pauli 1993) and later in many other workplaces. The aim of this work was testing and calibration of optical and camera equipment to verify the accuracy and reliability of data obtained. Served as an independent measurement of EBSD (Electron Backscatter Diffraction) data obtained from the same part of the studied thinsections. The data obtained were analyzed by quantitative analysis of microstructures (PolyLX - MATLABTM toolbox; Lexa 2003). The samples used for testing the methodology mentioned were taken on the profile of Hvězdná and Zdobnice near Rokytnice in the Eagle Mountains by contact orlica-snieznik complex and its mantle. Field studies showed the existence of west dipping shear zone along the said contact and deformed orthogneiss show a macroscopic superposition of several deformation events. The resulting frequency histograms similarities and differences of angles c-axes and angles misorientace grains have a high consensus in the azimuthal criterion, axes...

Texture in crystalline materials, i.e. preferred orientation (PO), is of interest in terms of texture-property relationships and also in X-ray diffraction science because PO can cause serious systematic errors in quantitative phase analysis using diffraction data. The single- parameter, pole-density distribution function (PDDF), proposed by March (1932) to represent PO in diffraction analysis, is used widely it Rietveld pattern-fitting following a suggestion by Dollase (1986). While the March model is an excellent descriptor of PO for gibbsite [AI(OH)3] x-ray powder diffraction (XRPD) data (O'Connor, Li and Sitepu, 1991), the model has proved to be deficient for Rietveld modelling with molybdite [Mo03], calcite [CaCO3] and kaolinite [A12O3.2SiO2.2H2O] XRPD data (Sitepu, 1991; O'Connor, Li and Sitepu, 1992; and Sitepu, O'Connor and Li, 1996). Therefore, the March model should not be regarded as a general-purpose PDDF descriptor.This study has examined the validity of the March model using XRPD and neutron powder diffraction (NPD) instruments operated, respectively, by the Curtin Materials Research Group in Perth and by the Australian Nuclear Science and Technology Organisation at the HIFAR reactor facility at Lucas Heights near Sydney. Extensive suites of XRPD and NPD data were measured for uniaxially-pressed powders of molybdite and calcite, for which the compression was systematically varied. It is clear from the various Rietveld refinements that the March model becomes increasingly unsatisfactory as the uniaxial pressure (and, therefore, the level of PO) increases.The March model has been tested with a physical relationship developed by the author which links the March r-parameter to the uniaxial pressure via the powder bulk modulus, B. The agreement between the results obtained from directly measured values of B and from Rietveld analysis with the March model are ++ / promising in terms of deducing the powder bulk modulus from the March r-parameter.An additional test of the March model was made with NPD data for specimens mounted, first, parallel to the instrument rotation axis and, then, normal to the axis. The results have provided some further indication that the March model is deficient for the materials considered in the study.During the course of the study, it was found that there are distinct differences between the direction of the near-surface texture in calcite, as measured by XRPD, and bulk texture characterised by NPD. The NPD-derived textures appear to be correct descriptions for the bulk material in uniaxially-pressed powders, whereas the XRPD textures are heavily influenced by the pressing procedure.An additional outcome of the NPD work has been the discovery, made jointly with Dr Brett Hunter of ANSTO, that the popular LHPM Rietveld code did not allow for inclusion of PO contributions from symmetry-equivalent reflections. Revision of the code by Dr Hunter showed that there is substantial bias in Rietveld-March r-parameters if these reflections are not factored correctly into the calculations.Finally, examination of pole-figure data has underlined the extent to which the March model oversimplifies the true distributions. It is concluded that spherical harmonics modelling should be used rather than the March model as a general PO modelling tool.

Ti nano-films are deposited on a NaCl(001) single crystal substrate by ion beam sputtering from a Ti target, and then annealed. Ti crystallites on a NaCl(001) substrate with increase in the substrate temperature and annealing have the preferred orientation (1-101) and (0001).

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Nanocrystalline £\-Zr condensates deposited by ion beam sputtering on the NaCl (100) surfaces and then annealed at 100 ¢J to 750 ¢J in air. The phases present were identified by transmission electron microscopy to be nanometer-size £\-Zr+ZrO¡B£\-Zr+ZrO+c-ZrO2¡Bc-ZrO2¡Bc-+t-ZrO2¡Bt-ZrO2¡Band t-+m-ZrO2 phase assemblages with increasing annealing temperature. The zirconia showed strong {100} preferred orientation due to parallel epitaxy with NaCl (100) when annealed between 150 ¢J and 500 ¢J in air. The c- and t-zirconia condensates also showed (111)-specific coalescence among themselves. The c- and/or t-ZrO2 formation can be accounted for by the small grain size, the presence of low-valence Zr cation and the lateral constraint of the neighboring grains. (Part 1) Nanocrystalline £\-Zr condensates were deposited on the NaCl (100) plane at 25 to 450 ¢J by radio frequency ion beam sputtering from a pure 99.9¢H Zr disk. The nano condensates were identified by transmission electron microscopy to be quasiamorphous, £\-Zr, £\-Zr+ZrO and £\-Zr+ZrO+c-ZrO2 phase assemblages with increasing substrate temperature. At 400 ¢J and under 1-20 sccm oxygen, c- and t-ZrO2 nanocondensates were assembled on NaCl (100) as monolayer nanocrystalline material and showed strong preferred orientation. The c- and/or t-ZrO2 were retained by small grain size, low-valence Zr cation and 2-D matrix constraint of the film. (Part 2) Nanosized c- and t-ZrO2 were formed as monolayer nanocrystalline film on NaCl (100) plane by radio frequency ion beam sputtering. The microstructure and the epitaxy relationship with the NaCl (100) plane were studied by a high resolution transmission electron microscope. The epitaxy orientation was found to be [001]Z//[001]N, [100]Z//[1 0]N (group A), and [011]Z//[001]N, [100]Z//[100]N (group B) between zirconia (Z) and NaCl (N). Group B has two variants and is the dominant type. The possible causes for the epitaxy relationship are discussed. Crystallites within the same group can merge by rotation and coalesce into a single crystal, whereas crystallites in different groups can form high-angle grain boundaries. (Part 3) Special interfaces were formed for the c- and/or t-ZrO2 (Z) nano-crystals when deposited on the NaCl (N) (100) cleavage plane by ion beam sputtering to follow the epitaxy relationships of [001]Z//[001]N, (100)Z//(1 0)N (group A); and [011]Z//[001]N, (100)Z//(100)N (group B1) or (100)Z//(010)N (group B2). The nanoparticles in group A and B were impinged and coalesced to form {220}A/{200}B and {200}A/{111}B interfaces; with anchored dislocation whereas those in group B1 and B2 form {220}B1/{200}B2 interface. The {220}A/{200}B interface is found to be of especially low energy due to good match O2¡V lattice sites, and smoothly joints {200} and {220} planes across the interfaces without mismatch strain and dislocations. The special interfaces may shed light on the epitaxial mechanism of nanocrystalline materials in general. (Part 4)

Thesis advisor: Seth C. Kruckenberg / The West Antarctic rift system is one of the most expansive regions of extended continental crust on Earth, but relatively little is known about the structure of the mantle lithosphere in this region. This research aims to examine a suite of ultramafic mantle xenoliths from several volcanic centers located throughout Marie Byrd Land, West Antarctica. Through the use of several complementary analytical methods, the deformational and compositional heterogeneity of the lithospheric mantle in this region is characterized. The Marie Byrd Land xenoliths have equilibration temperatures between 779 and 1198°C, which is a range that corresponds to extraction depths between 39 and 72 km. These samples preserve significant mineralogical and microstructural heterogeneities that document both lateral and vertical heterogeneities within the Marie Byrd Land mantle lithosphere. The modal mineralogy of spinel peridotites varies between 40 – 99% olivine, 0 – 42% diopside, 0 – 45% enstatite and 0 – 5% chromite. Minimum olivine grain sizes range from 60 to 110 µm and maximum olivine grain sizes range from 2.5 to 10.0 mm. The geometric mean grain size of olivine in these samples ranges from 100 µm to 2 mm and has an average of 694 µm. The geometric mean grain size of diopside ranges from 90 to 865 µm and has an average of 325 µm, whereas that of enstatite ranges from 120 µm to 1.2 mm and has an average of 625 µm. Comparatively, the pyroxenites contain 0 – 29% olivine, 29 – 95% diopside, 1 – 36% enstatite and 1 – 11% chromite. Deformation mechanism maps suggest that the olivine within the MBL peridotite xenoliths primarily accommodate strain through the operation of dislocation-accommodated grain-boundary sliding at strain rates between 10-19/s and 10-11/s. This is consistent with microstructural observations of the suite made using optical microscopy (e.g., deformation bands and subgrains in olivine; aligned grain boundaries between contrasting phases). Application of the olivine grain size piezometer indicates that the suite preserves differential stresses ranging from 0.5 MPa to 50 MPa, with mean differential stresses ranging from 4 to 30 MPa. Values of mean differential stress only vary slightly throughout the field area, but generally decrease in magnitude towards the east with maximum values migrating upwards in the lithospheric mantle along this transect. The samples from some volcanic centers are highly homogenous with respect to their microstructural characteristics (e.g., Mount Avers – Bird Bluff), whereas others display heterogeneities on the sub-five-kilometer-scale (e.g., Demas Bluff). Comparatively, mineralogical heterogeneities are more consistent throughout the sample suite with variations generally being observed between the sub-five-kilometer-scale and the sub-ten-kilometer-scale. Most samples within the MBL peridotite suite display axial-[010] or A-type olivine textures. Although less dominant, axial-[100], B-type and random olivine textures are also documented within the suite. Axial-[010] textures have J-indices and M-indices ranging from 1.7 – 4.1 and 0.08 – 0.21, respectively. The average value of the J-index for axial-[010] textures is 2.9, whereas the average M-index of these samples is equal to 0.15. Overall, A-type textures tend to be stronger with J- and M-indices ranging from 1.4 – 9.0 and 0.07 – 0.37, respectively. The olivine crystallographic textures of the MBL xenolith suite are heterogeneous on scales that are smaller than the highest resolution that is attainable using contemporary geophysical methods, which implies that patterns of mantle flow and deformation are far more complex than these studies suggest. / Thesis (MS) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Texture, i.e. preferred orientation, can cause large systematic errors in quantitative analysis of crystalline materials using x-ray powder diffraction (XRPD) data. Various mathematical forms have been proposed for the application of preferred orientation corrections. The most promising of these appears to be the single-parameter March (1932) model proposed by Dollase (1986).Li and O'Connor (1989) applied the March model to determine the level of preferred orientation in various gibbsites using two procedures. The first involved the Rietveld (1969) least squares pattern-fitting method. Each pattern was Rietveld-analysed in two ways, initially assuming random orientation of the crystallites and subsequently with the March model. The second procedure for preferred orientation analysis, described here as the line ratio method, determines preferred orientation factors according to the intensity ratios of carefully selected line pairs.In the thesis the procedures proposed by Li and O'Connor for texture analysis have been evaluated with XRPD data sets for molybdite, calcite and kaolinite. The results indicate that while the March formula improves agreement between the' calculated and measured patterns in Rietveld analysis, other forms of systematic error in the intensity data appear to limit the effectiveness of the March formula in general. It has been found also that the line ratio method improves agreement between the data sets, but less effectively than the Rietveld method. It is proposed that extinction is likely to be the most influential source of systematic error competing with texture.