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1رسالة جامعية
المؤلفون: Avadanii, Diana
المساهمون: Wilkinson, Angus, Hansen, Lars, MacNiocaill, Conall
مصطلحات موضوعية: Rock and Mineral Physics, Materials science, Earth Science
الوصف: Grain boundaries in polycrystalline materials underpin deformation processes in both low- and high- temperature regimes. The study of grain boundary types relies on the investigation of small volumes of material containing one interface. This thesis presents small-scale mechanical tests on forsterite grain boundaries. Forsterite is the Mg-rich end member of the solid solution of the mineral olivine. Olivine is a key geological material influencing large-scale, long-term planetary deformation processes on rocky planets. Studies on the deformation of olivine at low temperatures and high stresses have emphasized the importance of a grain-size effect impacting the yield stress. Laboratory observations have demonstrated that aggregates with smaller grains are stronger than aggregates with coarser grains. However, the interactions between intracrystalline defects and grain boundaries leading to this effect remain unresolved in olivine. Moreover, most of our understanding of the role of grain boundaries in the deformation of olivine is inferred from comparison of experiments on single crystals to experiments on polycrystalline samples. In this study, we use high-precision mechanical testing of synthetic forsterite bicrystals with well characterised interfaces and directly observe and quantify the mechanical properties of olivine grain boundaries. We perform room-temperature spherical and Berkovich nanoindentation tests on low- and high- angle grain boundaries. We observe that in the high-angle grain boundary sample, the interface acts as a site of microplasticity and as a barrier to incoming dislocations. The low-angle grain boundary does not interact with other crystalline defects in a measurable manner. Additionally, we conduct in-situ micropillar compression tests at high-temperature (700C) on low- and high-angle grain boundaries. In these in-situ experiments, the boundary is contained within the micropillar and oriented at 45 degrees to the loading direction to promote shear along the boundary. We observe differences in deformation style between the pillars containing the grain boundary and the pillars in the crystal interior. The pillars containing the grain boundary consistently support elastic loading to higher stresses than the pillars without a grain boundary. Moreover, the pillars without the grain boundary sustain larger plastic strain. Post-deformation advanced microstructural characterization confirms that under these experimental conditions, sliding did not occur along the grain boundary. These observations support the hypothesis that at our experimental conditions grain boundaries are relatively stronger compared to the crystal interior, and some grain boundaries can act as potent sources of dislocations in olivine. Studying grain boundaries and their interaction with crystalline defect relies on small-scale, high-precision mechanical testing and microstructural characterization. One such technique is instrumented nanoindentation with a continuous stiffness measurement, which has gained increased popularity in material sciences. Studies implementing spherical nanoindentation rely on the implementation of different methodologies for instrument calibration and for circumventing tip shape imperfections. In this study, we test, integrate, and re-adapt published strategies for tip and machine stiffness calibration for spherical tips. We propose a routine for independently calibrating the effective tip radius and the machine stiffness using three reference materials (fused silica, sapphire, glassy carbon) and validate our proposed workflow against key benchmarks. We apply the resulting calibrations to data collected in materials with varying ductility (olivine, titanium, tungsten) to extract indentation stress-strain curves. We synthesize these analysis routines in a single workflow for use in future studies aiming to extract and process data from spherical nanoindentation. Another strategy for investigating grain boundaries and microstructure evolution represents in-situ mechanical testing. In order to test materials under simple shear studies implement different strategies to transform a far-field compressive or tensile applied stress into shear stress in both mesocale and microscale specimens. In this study, we describe an apparatus developed to investigate in-situ ductile materials by directly applying a simple shear to a thin sheet of material. We propose a novel sample geometry compatible with established techniques for strain characterization and specimens with a wide range of starting microstructures. We demonstrate the capabilities of our apparatus by deforming solder alloys and aluminium, and use optical digital image correlation and electron microscopy for the in-situ characterization of the deforming sample.
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2دورية أكاديمية
المؤلفون: Chinchalkar, Neeraja
المصدر: Electronic Thesis and Dissertation Repository
مصطلحات موضوعية: Meteorite impact crater, impact melting, zircons, West Clearwater Lake impact structure, Mistastin Lake impact structure, Geochemistry, Geology, Mineral Physics
الوصف: Impact melts physically and texturally resemble endogenic igneous melts but are known to be initially superheated. However, the exact amount of superheating and, therefore, the temperatures experienced by superheated impact melts are not very well constrained. Zircon is a refractory mineral that can survive high pressure-temperature events and has been known to persist even in the extreme conditions of impact events. Additionally, zircon (ZrSiO4) dissociates to zirconia (ZrO2) and silica (SiO2) at temperatures > ~1670 ℃, and the pressure-temperature phase relationships of zircon, zirconia, and silica have been well studied. Zircons in different types of impactites from the West Clearwater Lake impact structure were investigated using various microanalytical techniques to: (1) identify the presence of crystallographic deformation; (2) to assess the orientation relationships arising from polymorphic transformations of high pressure or high temperature phases using a phase heritage approach, and (3) to constrain initial pressure-temperature conditions with the help of phase relationships. We documented evidence for superheating > 2370 ℃ in an impact glass sample, shock pressures of >30 GPa in some impactites, and observed a variety of microstructures ranging from fully dissociated and granular zircons to undeformed zircons in all impactite samples. Our results also demonstrate that impact melt evolution is complex and the evidence for superheating in zircons appears to be differentially preserved in different impactite settings. Furthermore, we also investigated the variation in textures and geochemistry of a thick impact melt deposit (Discovery Hill) at the Mistastin Lake impact structure, which was recently shown to contain evidence for superheating in excess of 2370 ℃. It is proposed that the textures seen in this melt rock are a result of a complex cooling history governed by the initially superheated melt that interacted with cooler country rock. Because such textures are analogous to those seen in ...
وصف الملف: application/pdf
العلاقة: https://ir.lib.uwo.ca/etd/9744Test; https://ir.lib.uwo.ca/context/etd/article/12544/viewcontent/Thesis_V2_AUG30.pdfTest; https://ir.lib.uwo.ca/context/etd/article/12544/filename/0/type/additional/viewcontent/Supp_Geochem_Tables.xlsxTest
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3دورية أكاديمية
المؤلفون: Robert Cooper Liebermann
المصدر: The Review of High Pressure Science and Technology. 2023, 33(1):48
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4دورية أكاديمية
المؤلفون: Hongzhan Fei, Baohua Zhang, Jia Liu, Takashi Yoshino
المصدر: Frontiers in Earth Science, Vol 10 (2022)
مصطلحات موضوعية: water distribution, water circulation, mineral physics, mantle, geodynamics, Science
وصف الملف: electronic resource
العلاقة: https://www.frontiersin.org/articles/10.3389/feart.2022.1030793/fullTest; https://doaj.org/toc/2296-6463Test
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5دورية أكاديمية
المؤلفون: Zongfa Wang, Yi Wang
المصدر: Frontiers in Earth Science, Vol 10 (2022)
مصطلحات موضوعية: water content, water distribution, the mantle transition zone, mineral physics modeling, seismic tomography, Science
الوصف: Although the discoveries of hydrous ringwoodite inclusions and ice-VII inclusions in natural diamonds suggest a hydrous mantle transition zone (MTZ), water content and distribution in the MTZ remain unclear. Here combining a global P- and S-wave isotropic velocity tomography and mineral physics modeling, we image the water distribution in the MTZ. Our results indicate that the MTZ is a main water reservoir inside the Earth, and the total water content of the MTZ is about 0.64–1 seawater. The upper MTZ (410–520 km) and the lower MTZ (520–660 km) contain 0.3–0.5 wt% and 0.15–0.2 wt% water, respectively, implying water contents of the MTZ decrease with increasing depths. The most hydrous regions are mainly located near subduction zones, where the upper MTZ and the lower MTZ can contain water up to 0.5–1 wt% and 0.2–0.5 wt%, respectively, indicating water is transported into the MTZ by hydrous slabs. In addition, old subducted slabs in the western Pacific subduction zone are more hydrous than young subducted slabs in the eastern Pacific subduction zone. We also propose a water circulation model which integrates our results of the water content and distribution in the MTZ.
وصف الملف: electronic resource
العلاقة: https://www.frontiersin.org/articles/10.3389/feart.2022.984063/fullTest; https://doaj.org/toc/2296-6463Test
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6دورية أكاديمية
المؤلفون: Poirier, Jean-Paul1 jean-paul.poirier@noos.fr
المصدر: Comptes Rendus Geoscience. Feb2019, Vol. 351 Issue 2/3, p67-70. 4p.
مصطلحات موضوعية: *GEOPHYSICS, *MINERAL physics, *HIGH pressure (Technology), *CONFERENCES & conventions
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7مؤتمر
المؤلفون: Garai, Máté, DiNella, Vincent, Thompson, Dr. Lily, Abdelhamid, Alaa
مصطلحات موضوعية: Scholarship Sewanee 2022, University of the South, Ruby, diamond, fluorescence, spectroscopy, high-pressure, mineral physics, Raman
الوصف: The interiors of terrestrial planets, satellites, and other celestial bodies may provide essential clues to a better understanding of the formation and evolution of our Solar System and other planetary systems throughout the galaxy. Mineral physics is a scientific discipline that probes the physical and chemical properties of planet-forming materials at the extreme pressure and temperature conditions of planetary interiors. For example, the pressure at the center of the Earth is 3.6 million times atmospheric pressure and the temperature of the Earth’s core is approximately the same temperature as the surface of our sun. The pressures and temperatures inside larger or denser planets and exoplanets are even more extreme. In order to constrain the formation, composition, and evolution of planetary interiors, we must first understand what happens to planet-forming materials at the pressure and temperature conditions where we expect them to exist. Mineral physicists can reproduce the high pressures of planetary interiors using diamond anvil cells (DACs), which can be combined with lasers or external resistive heating to recreate the extreme temperatures of planetary interiors. To measure and monitor the pressure of samples that are pressurized within a DAC, an in situ pressure standard is required. Ruby (chromium-doped Al2O3 or Cr:Al2O3) is used as an in situ pressure standard because of two important properties: (1) it fluoresces at a well-defined wavelength of light when excited by a laser, and (2) the wavelength of the ruby fluorescence increases as the ruby is pressurized in a way that has been well-calibrated. In the summer of 2021, Mate Garai, Alaa Adel Abdelhamid, and Vincent DiNella worked under the supervision of Dr. Lily Thompson to design and construct a ruby fluorescence spectrometer that allows the in situ measurement of pressurized mineral physics experiments by exciting ruby fluorescence and measuring the resultant fluorescence spectra.
وصف الملف: application/pdf
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8دورية أكاديمية
المؤلفون: Noonan, Gillian G
المصدر: Undergraduate Student Research Internships Conference
مصطلحات موضوعية: Earth sciences, zircon, pressure, Geochemistry, Mineral Physics
الوصف: Zircon is a mineral that can commonly be found in many rocks in the Earth’s crust and other planetary bodies. Meteorite impact sites have also been shown to contain zircon and its high-pressure polymorph, Reidite.
وصف الملف: application/pdf
العلاقة: https://ir.lib.uwo.ca/usri/usri2022/ReOS/45Test; https://ir.lib.uwo.ca/context/usri/article/1516/viewcontent/PressureStudy.pdfTest
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9دورية أكاديمية
المؤلفون: Berrada, Meryem
المصدر: Electronic Thesis and Dissertation Repository
مصطلحات موضوعية: Electrical Resistivity, Thermal Conductivity, Data analysis, Voltage drop, Mineral Physics
الوصف: The source of the fluid stirring mechanism that powers the dynamo of terrestrial-type bodies during their active magnetic field era is debated. Prior to the formation of a solid inner core, thermal convection may cause enough mechanical stirring of the core fluid to generate a magnetic field through dynamo action. After inner core formation, compositional convection in the liquid outer core becomes the main source of fluid stirring mechanism to power a dynamo. Constraints on the likelihood and duration of these convection mechanisms may be obtained by the experimental determination of the thermal properties of core materials. These cores consist of complex Fe-alloys and the effects of impurities have not yet been established under high pressures and temperatures. The first objective of this thesis was to investigate the behavior of electrical resistivity along the melting boundary of metals by measurements in large volume presses (1000 ton, 3000 ton) using the 4-wire method. Unprecedented measurements on Au up to liquid temperatures from 2-5 GPa show a decrease in resistivity along the melting boundary, conflicting with the prediction of invariant behavior. In contrast, the first measurements on Fe-8.5wt%Si revealed a constant behavior of resistivity along the melting boundary from 10-24 GPa. The second objective of this thesis was to investigate the effect of impurities on the resistivity via measurements on Fe-xSi (x is 2, 8.5, 17 wt%) and Fe-10wt%Ni-10wt%Si from 2-24 GPa and up to liquid temperatures. The similarity in Fe-8.5wt%Si and Fe-10wt%Ni-10wt%Si measurements indicate a negligible effect of Ni. Finally, the estimated heat flow at the top of an Fe-10wt%Ni-10wt%Si Earth core is estimated to be 14 TW. The results of an Fe-Si lunar core date the end of the high magnetic field dynamo to be in the range of 3.32-3.80 Gyr. A similar analysis of an Fe-8.5wt%Si Mercurian core suggests a thermally driven dynamo up to 4.28-4.42 Gyr. However, an Fe-10wt%Ni-10wt%Si Mercurian core indicates a thermally driven dynamo ...
وصف الملف: application/pdf
العلاقة: https://ir.lib.uwo.ca/etd/8612Test; https://ir.lib.uwo.ca/context/etd/article/11295/viewcontent/PhD_Thesis__July_4__without_page_1.pdfTest
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10دورية أكاديمية
المؤلفون: Nabeh, Nader, Brokaw, Cheyenne, Picard, Aude
المصدر: Life Sciences Faculty Publications
مصطلحات موضوعية: Iron sulfide minerals, Biomineral, Microbial sulfate reduction, Desulfovibrio, Mackinawite, Greigite, Organic carbon preservation, Laboratory and Basic Science Research, Mineral Physics
الوصف: Organic carbon sequestration in sedimentary environments controls oxygen and carbon dioxide concentrations in the atmosphere. While minerals play an important role in the preservation of organic carbon, there is a lack of understanding about the formation and stability of organo-mineral interactions in anoxic environments, especially those involving authigenic iron sulfide minerals. In this study, we quantified organic carbon and nitrogen sequestered in biogenic iron sulfide minerals co-precipitated with sulfate-reducing bacteria (SRB) in freshwater and marine conditions in long-term laboratory experiments. The amounts of C and N associated with biogenic iron sulfide minerals increased with increasing cell biomass concentrations available in the media. C and N levels stabilized over the first 2 months of incubation and remained stable for up to 1 year. Crystalline mackinawite (FeS) formed in all experimental conditions and transformed to greigite only in some experimental conditions. We did not find evidence that this mineral transformation affected C and N levels, neither could we identify the factors that controlled greigite formation. Pyrite did not form in our experimental conditions. While C concentrations in minerals correlated with concentrations of reduced sulfate in both the freshwater and marine media, removal of OC by iron sulfide minerals was more efficient in freshwater than marine conditions. Removal of OC by iron sulfide minerals was also more efficient when cells were present (SRB biomass) in comparison with abiotic incubations with organic mixtures (e.g., tryptone, yeast extract, and casamino acids). Our study highlights the potential for biogenic iron sulfide minerals to quantitatively contribute to organic carbon preservation in anoxic environments.
وصف الملف: application/pdf
العلاقة: https://digitalscholarship.unlv.edu/sls_fac_articles/661Test; https://digitalscholarship.unlv.edu/cgi/viewcontent.cgi?article=1942&context=sls_fac_articlesTest
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