Добірка наукової літератури з теми "Pérovskites – Texture – Effets des hautes pressions"
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Дисертації з теми "Pérovskites – Texture – Effets des hautes pressions":
Gay, Jeffrey. "Microstructures and anisotropy of pyrolite in the Earth’s lower mantle : insights from high pressure/temperature deformation and phase transformation experiments." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR043.
Microstructures in mantle rocks impact the way seismic waves travel through the Earth and are dependent on the pressure, temperature, and deformation applied to the rock. At approximately 660 km depth, an increase in seismic wave velocities mark a distinct boundary that separates the upper and lower mantle. Another boundary is found at approximately 2700 km depth and marks the beginning of the D" layer. Furthermore, observations of seismic anisotropy at these discontinuities have been made. These boundaries are largely believed to be related to phase transitions from ringwoodite [(Mg,Fe)2SiO4, space group Fd3m] to bridgmanite [(Mg,Fe)SiO3, space group Pbnm] to post-perovskite [(Mg,Fe)SiO3, space group Cmcm]. In order to make interpretations of these seismic observations, however, a sound understanding of what generates these microstructures is required.Here, we approach this problem through high pressure and high temperature experiments. We identify microstructures in polycrysalline mantle minerals resulting from in-situ transformation and deformation using radial and multigrain X-ray diffraction in the diamond anvil cell. In the first study we transform a bridgmanite analogue, NaCoF3, from a perovskite to post-perovskite structure. The following two studies investigate the transformation of an average mantle composition, pyrolite, at conditions relevant to the 660 km discontinuity and further deformation at pressures and temperatures corresponding to depths between 500 and 2400 km. In the final study, we test an aluminum rich 'pyrolite' composition (pyrolite minus olivine) in order to compare transformation and deformation microstructures to those observed in experiments on pure pyrolite.Results from radial diffraction experiments show the transformation from perovskite to post-perovskite in NaCoF3 are reconstructive in nature and for which we identify the orientation relationships. Major takeaways from the multigrain X-ray diffraction experiments are as follows: i) the decomposition from (ringwoodite + garnet) to (bridgmanite + davemaoite + ferropericlase) result in non-reconstructive 001 transformation textures in bridgmanite, 101 and 111 textures in davemaoite, and no preferred orientation in ferropericlase. ii) With further deformation, bridgmanite changes to 100 and 010 orientations with no change in either davemaoite or ferropericlase. iii) Textures in bridgmanite and davemaoite in pyrolite minus olivine are similar to those observed in our experiments on pure pyrolite.Finally, we use the results of these experiments to build a model for S and P-wave seismic anisotropy within a subducting slab and the surrounding mantle for multiple scenarios and compare our results to those of the literature. This interplay between experiments and seismic models are important in order to provide constraints on deformation, dynamics, and history of the Earth's interior
Mandolini, Tommaso. "Microstructural evolution of polymineralic aggregates deformed under high pressure and temperature : an in-situ and post-mortem study on olivine+serpentine." Electronic Thesis or Diss., Université de Lille (2022-....), 2022. http://www.theses.fr/2022ULILR047.
At plate tectonic boundaries, the lithosphere is deformed and strain localization occurs up to kilometers-scale, which can manifest in form of shear zones. The strain localization suggests the strength of the lithosphere is locally weakened. The formation of interconnected layers of weaker minerals in the lithosphere is a potential mechanism to achieve such weakening. Serpentinized peridotite is commonly found within and between tectonic plates. It is mainly composed of olivine and serpentine minerals. The latter is generally accepted to be weaker than olivine at geological strain rates. During deformation, strain is thus expected to preferentially partition into serpentine than into olivine. This can lead to the formation of interconnected weak layers (IWL) of serpentine where strain localizes.The present work is based on microstructural investigation to infer the strain accommodation in rocks. Olivine+serpentine aggregates with two compositions (10 and 20 vol.% serpentine) are used as a proxy for partially serpentinized peridotites. The aggregates are experimentally deformed in torsion at high pressures (HP, > 2 GPa) and high temperatures (HT, > 300°C) at an equivalent strain rate of 10-4 s-1. The experiments are coupled with in-situ absorption contrast X-ray tomography. I obtain 2D and 3D information on connectivity and structural layering in the microstructure of the ‘weak' serpentine. Electron microscopy is performed on recovered samples to link the in-situ X-ray tomography observations to the plastic properties of the phases.I first outline experimental and image-data processing procedures specific to in-situ HP experimental deformation. Then, I study the deformation of the aggregates with increasing shear deformation at multiple scales of observations. The main aim is to observe the onset and development of IWL in its microstructure. The relations between the morphology and plastic properties of the phases in the rock are investigated to understand the strain localization in serpentinized peridotite.The main results show the deformation regime in olivine+serpentine aggregates can be described as semi-brittle, with the dominant phase of olivine (‘stronger') mainly displaying brittle deformation, whereas the serpentine (‘weaker') showing a dominant ductile-style deformation. A strain γ of ca. 4-5, serpentine content of ca. 20 vol.%, and initial fraction of large clusters >15 vol.% determine the condition for IWL configuration in the olivine+serpentine aggregates. Conversely, at serpentine content of ca. 10 vol.%, IWL do not occur, independently of strain or initial clusters size distribution of serpentine. This is more consistent with a load-bearing framework (LBF) behavior, where the stronger olivine grains are jammed, and during deformation crush one another, leading to grain size reduction and accommodating much of the deformation in the rock. These findings suggest contents of serpentine >10 vol.% or ca. 20 vol.% define a threshold for crucial changes in the morphology, connectivity, percolation, of the weak serpentine in serpentinized peridotites under shear. This may lead to important changes in deformation behavior and mechanical properties of the rock.In light of these findings, I give some perspectives for strain localization and shear zones initiation in the lithosphere
Bollinger, Caroline. "Rhéologie de l’olivine polycristalline aux conditions du manteau supérieur : étude en D-DIA." Electronic Thesis or Diss., Lille 1, 2013. http://www.theses.fr/2013LIL10038.
This manuscript presents an experimental investigation of the effect of pressure on the rheology of olivine and forsterite. Indeed, the geodynamics of the Earth’s interior is not always well understood and needs input for experimental data. The movements of materials in the Earth mantle induce plastic deformation of the constitutive minerals and, particularly, are connected to the rheology of olivine, the main constituent of the upper mantle. Polycristalline olivine and forsterite are deformed in D-DIA at pressure-temperature conditions of the upper mantle, from 3 to 8 GPa and 1373-1673 K. Coupled with synchrotron radiations, applied stresses and developed lattice preferred orientations are measured in situ, with the addition of transmission electron microscopy observations on the run products. From these experimental data, rheological laws have been determined in dislocation-creep regime, under “wet” conditions and below 8GPa for both of these minerals. Pressure effect is observed with an activation volume of 12.8 ± (5) cm3.mol-1 for olivine. For forsterite, this parameter is 12.5 ± 5 cm3.mol-1, with a stress-exponent of n’= 2.35 (0.6). The water influence is apparently not significant compared to the pressure effect, and the iron-bearing olivine is more ductile than iron-free olivine.Developed textures show a dominant slip-system along the (010) plane below 8 GPa. Above, textures are weaker, leading to the conclusion that others slip-systems and/or deformation mechanisms take a part in the plasticity of the olivine. This transition is well correlated with the decreasing of the observed seismic anisotropy of the upper mantle below -200 km
Bollinger, Caroline. "Rhéologie de l’olivine polycristalline aux conditions du manteau supérieur : étude en D-DIA." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10038/document.
This manuscript presents an experimental investigation of the effect of pressure on the rheology of olivine and forsterite. Indeed, the geodynamics of the Earth’s interior is not always well understood and needs input for experimental data. The movements of materials in the Earth mantle induce plastic deformation of the constitutive minerals and, particularly, are connected to the rheology of olivine, the main constituent of the upper mantle. Polycristalline olivine and forsterite are deformed in D-DIA at pressure-temperature conditions of the upper mantle, from 3 to 8 GPa and 1373-1673 K. Coupled with synchrotron radiations, applied stresses and developed lattice preferred orientations are measured in situ, with the addition of transmission electron microscopy observations on the run products. From these experimental data, rheological laws have been determined in dislocation-creep regime, under “wet” conditions and below 8GPa for both of these minerals. Pressure effect is observed with an activation volume of 12.8 ± (5) cm3.mol-1 for olivine. For forsterite, this parameter is 12.5 ± 5 cm3.mol-1, with a stress-exponent of n’= 2.35 (0.6). The water influence is apparently not significant compared to the pressure effect, and the iron-bearing olivine is more ductile than iron-free olivine.Developed textures show a dominant slip-system along the (010) plane below 8 GPa. Above, textures are weaker, leading to the conclusion that others slip-systems and/or deformation mechanisms take a part in the plasticity of the olivine. This transition is well correlated with the decreasing of the observed seismic anisotropy of the upper mantle below -200 km
Brière, Benjamin. "Propriétés optiques de matériaux à fortes corrélations électroniques en conditions extrêmes." Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4020/document.
Materials with strongly correlated electrons belong to the most intriguing systems in condensed matter physics due to their great variety of properties discovered during the last decades such as high temperature superconductivity, molecular conductors and colossal magnetoresistance. During this thesis, two types of strongly correlated materials have been studied: the quadruple perovskite EuCu3fe4Oi2 and the molecular conductors [Au(Et-thiazdt)2J. EuCu3Fe4Oi2 undergoes a metal to insulator transition at low temperature (240K), and [Au(Et-thiazdt)2J goes from a Mott insulator to a correlated metal state under high pressure. Infrared microspectroscopy measurements allowed us to probe the low energy electrodynamic of these systems. Ab-initio calculations were also used to understand the mechanisms of the transitions and the role of electronic correlations in the material