An X‐ray transparent experimental triaxial rock deformation apparatus, here named `Mjölnir', enables investigations of brittle‐style rock deformation and failure, as well as coupled thermal, chemical ...and mechanical processes relevant to a range of Earth subsurface environments. Designed to operate with cylindrical samples up to 3.2 mm outside‐diameter and up to 10 mm length, Mjölnir can attain up to 50 MPa confining pressure and in excess of 600 MPa axial load. The addition of heaters extends the experimental range to temperatures up to 140°C. Deployment of Mjolnir on synchrotron beamlines indicates that full 3D datasets may be acquired in a few seconds to a few minutes, meaning full 4D investigations of deformation processes can be undertaken. Mjölnir is constructed from readily available materials and components and complete technical drawings are included in the supporting information.
The design, construction and assembly details for an X‐ray transparent triaxial deformation cell for 4D investigations of rock deformation and coupled chemical–mechanical processes in the geosciences are presented. The portability and flexibility of the cell are demonstrated by deployment on four different synchrotron beamlines.
Full text
Available for:
FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Third‐ and fourth‐generation synchrotron light sources with high fluxes and beam energies enable the use of innovative X‐ray translucent experimental apparatus. These experimental devices access ...geologically relevant conditions whilst enabling in situ characterization using the spatial and temporal resolutions accessible at imaging beamlines. Here, Heitt Mjölnir is introduced, a heated miniature triaxial rig based on the design of Mjölnir, but covering a wider temperature range and larger sample volume at similar pressure capacities. This device is designed to investigate coupled thermal, chemical, hydraulic and mechanical processes from grain to centimetre scales using cylindrical samples of 10 mm × 20 mm (diameter × length). Heitt Mjölnir can simultaneously reach confining (hydraulic) pressures of 30 MPa and 500 MPa of axial stress with independently controlled sample pore fluid pressure < 30 MPa. This internally heated apparatus operates to temperatures up to 573 K with a minimal vertical thermal gradient in the sample of <0.3 K mm−1. This new apparatus has been deployed in operando studies at the TOMCAT (Swiss Light Source), I12 JEEP (Diamond Light Source) and PSICHÉ (Synchrotron SOLEIL) beamlines for 4D X‐ray microtomography with scan intervals of a few minutes. Heitt Mjölnir is portable and modular, allowing a wide range of 4D characterizations of low‐grade metamorphism and deformational processes. It enables spatially and temporally resolved fluid–rock interaction studies at conditions of crustal reservoirs and is suitable for characterization of material properties in geothermal, carbonation or subsurface gas storage applications. Technical drawings and an operation guide are included in this publication.
Heitt Mjolnir, a heated miniature triaxial apparatus for 4D synchrotron microtomography, is described. This new device combines the capacities of a deformation rig and a thermal reactor with large sample volumes and is suitable for a large range of geo‐energy applications.
Full text
Available for:
FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Plants close their stomata during drought to avoid excessive water loss, but species differ in respect to the drought severity at which stomata close. The stomatal closure point is related to xylem ...anatomy and vulnerability to embolism, but it also has implications for phloem transport and possibly phloem anatomy to allow sugar transport at low water potentials. Desiccation‐tolerant plants that close their stomata at severe drought should have smaller xylem conduits and/or fewer and smaller interconduit pits to reduce vulnerability to embolism but more phloem tissue and larger phloem conduits compared with plants that avoid desiccation. These anatomical differences could be expected to increase in response to long‐term reduction in precipitation. To test these hypotheses, we used tridimensional synchroton X‐ray microtomograph and light microscope imaging of combined xylem and phloem tissues of 2 coniferous species: one‐seed juniper (Juniperus monosperma) and piñon pine (Pinus edulis) subjected to precipitation manipulation treatments. These species show different xylem vulnerability to embolism, contrasting desiccation tolerance, and stomatal closure points. Our results support the hypothesis that desiccation tolerant plants require higher phloem transport capacity than desiccation avoiding plants, but this can be gained through various anatomical adaptations in addition to changing conduit or tissue size.
Stomatal closure point during drought is related to xylem anatomy and vulnerability to embolism, but little is known about how stomatal closure point and the need to transport sugars at low tissue water potentials affects the phloem. We used tridimensional synchroton X‐ray microtomograph and light microscope imaging of combined xylem and phloem tissues of 2 coniferous species that show contrasting desiccation tolerance and stomatal closure points to test recent theoretical hypotheses about the changes needed in phloem anatomy to allow sugar transport at low water potentials. Our results support the hypothesis that plants operating at low water potentials require higher phloem transport capacity than plants that maintain relatively high water potentials, but the high transport capacity can be gained through various anatomical adaptations in addition to changing conduit or tissue size.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Virtual histology is increasingly utilized to reconstruct the cell mechanisms underlying dental morphology for fragile fossils when physical thin sections are not permitted. Yet, the comparability of ...data derived from virtual and physical thin sections is rarely tested. Here, the results from archaeological human deciduous incisor physical sections are compared with virtual ones obtained by phase‐contrast synchrotron radiation computed microtomography (SRµCT) of intact specimens using a multi‐scale approach. Moreover, virtual prenatal daily enamel secretion rates are compared with those calculated from physical thin sections of the same tooth class from the same archaeological skeletal series. Results showed overall good visibility of the enamel microstructures in the virtual sections which are comparable to that of physical ones. The highest spatial resolution SRµCT setting (effective pixel size = 0.9 µm) produced daily secretion rates that matched those calculated from physical sections. Rates obtained using the lowest spatial resolution setup (effective pixel size = 2.0 µm) were higher than those obtained from physical sections. The results demonstrate that virtual histology can be applied to the investigated samples to obtain reliable and quantitative measurements of prenatal daily enamel secretion rates.
The implementation of synchrotron radiation X‐ray microtomography for non‐destructive visualization of the dental prenatal enamel microstructure of intact archaeological human deciduous teeth is presented and compared with the physical thin‐sectioning of the same archaeological dental series. Prenatal daily enamel secretion rates, i.e. the distance between two adjacent daily enamel microstructures, have been measured with the two approaches. Results show a good agreement between physical and virtual histology.
Full text
Available for:
FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Porous ceramics have found immense applications in leading technological areas including porous burners, catalyst supports, and filtration media. It is extremely important to understand morphological ...features of highly porous ceramic bodies, and extract detailed quantitative information, including porosity, pore size distribution, interconnectivity, pore anisotropy, and sphericity. Synchrotron X‐ray microtomography has evolved as an excellent technique to acquire information on the complex three‐dimensional geometry and topology of reticulated structures. In this work, macroporous silicon oxycarbide ceramics are fabricated by positive replication of polyurethane sponge with the use of a preceramic polymer, and their topology has been studied by synchrotron X‐ray microtomography. Further, ceramic bodies have been prepared with progressive increase in the preceramic polymer concentration in the solution, and the ensuing change in the porous morphology of the structures have been studied. The results indicate the formation of excellent reticulated ceramics with 88–92% porosity, and with dense and uniform struts. The pore size distribution is uniform with very good sphericity and minimal anisotropy. The overall porosity indicates excellent interconnectivity with highly negative Euler numbers. The work presents a comprehensive analysis of reticulated ceramic bodies fabricated by preceramic polymer pyrolysis route.
Synchrotron X‐ray microtomography of macroporous silicon oxycarbide ceramics, prepared by sponge replication technique, exhibits homogeneous reticulated structure with 88–92% porosity. Quantitative analysis of the pore topology indicates excellent interconnectivity with negative Euler numbers, minimal anisotropy of the pores, and very good sphericity.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Recently, synchrotron radiation computed microtomography (SRµCT) has emerged as a promising tool for non‐destructive, in situ visualization of cochlear implant electrode arrays inserted into a human ...cochlea. Histological techniques have been the `gold standard' technique for accurate localization of cochlear implant electrodes but are suboptimal for precise three‐dimensional measurements. Here, an SRµCT experimental setup is proposed that offers the benefit of a high spatial and contrast resolution (isotropic voxel size = 4.95 µm and propagation‐based phase‐contrast imaging), while visualizing the soft‐tissue structures and electrode array of the cochlear implant simultaneously. In this work, perimodiolar electrode arrays have been tested, which incorporate thick and closely spaced platinum–iridium contacts and wiring. These data can assist cochlear implant and hearing research, can be used to verify electrode segmentation techniques for clinical computed tomography or could be utilized to evaluate cochlear implant electrode array designs.
The implementation of synchrotron radiation X‐ray microtomography for non‐destructive visualization of the internal microstructure of a human cochlea inserted with a highly absorbing cochlear implant electrode array is presented.
Full text
Available for:
FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Catastrophic failure of brittle rocks is important in managing risk associated with system‐sized material failure. Such failure is caused by nucleation, growth, and coalescence of microcracks that ...spontaneously self‐organize along localized damage zones under compressive stress. Here we present X‐ray microtomography observations that elucidate the in situ micron‐scale processes, obtained from novel tri‐axial compression experiments conducted in a synchrotron. We examine the effect of microstructural heterogeneity in the starting material (Ailsa Craig microgranite; known for being virtually crack‐free) on crack network evolution and localization. To control for heterogeneity, we introduced a random nanoscale crack network into one sample by thermal stressing, leaving a second sample as‐received. By assessing the time‐dependent statistics of crack size and spatial distribution, we test the hypothesis that the degree of starting heterogeneity influences the order and predictability of the phase transition between intact and failed states. We show that this is indeed the case at the system‐scale. The initially more heterogeneous (heat‐treated) sample showed clear evidence for a second‐order transition: inverse power law acceleration in correlation length with a well‐defined singularity near failure and distinct changes in the scaling exponents. The more homogeneous (untreated) sample showed evidence for a first‐order transition: exponential increase in correlation length associated with distributed damage and unstable crack nucleation ahead of abrupt failure. In both cases, anisotropy in the initial porosity dictated the fault orientation, and system‐sized failure occurred when the correlation length approached the grain size. These results have significant implications for the predictability of catastrophic failure in different materials.
Plain Language Summary
When rocks deform, tiny cracks appear, increasing in size and number until the rock breaks completely, often along a narrow plane of weakness where cracks have spontaneously aligned. Sometimes, when the microstructure is complicated, cracking accelerates quickly in a predictable way, giving a good indication of when the rock will break. In other cases, when the microstructure is more uniform, cracking accelerates more slowly and the rock breaks suddenly and early. To understand why failure is predictable in some cases but not others—a major problem in managing risk from material failure (e.g., earthquakes)—we used X‐ray imaging to see how cracks form and interact with each other inside deforming rocks. We found that predictable behavior only arose when cracks aligned themselves asymmetrically. The orientation of this damage zone was governed by the rock's pre‐existing microstructure. We also found distinct changes in crack size and spatial arrangement during alignment, indicating that the rock was approaching failure. However, when cracks did not align asymmetrically, similar changes were not observed and failure was not predictable. Our results are important because they help explain why reliable indicators of catastrophic failure are not always observed and why forecasting may only work in certain cases.
Key Points
Micron‐scale crack network evolution and localization are imaged in situ in deforming granite samples with controlled initial heterogeneity
Heterogeneity affects order and predictability of the phase transition to failure, which occurs as correlation length approaches grain size
Correlation dimension of the crack population is a key indicator of localization, and anisotropy in starting porosity dictates fault strike
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The investigation of the role played by CO2 circulating within the mantle during partial melting and metasomatic/refertilization processes, together with a re-consideration of its storage capability ...and re-cycling in the lithospheric mantle, is crucial to unravel the Earth's main geodynamic processes. In this study, the combination of petrology, CO2 content trapped in bulk rock- and mineral-hosted fluid inclusions (FI), and 3D textural and volumetric characterization of intra- and inter-granular microstructures was used to investigate the extent and modality of CO2 storage in depleted and fertile (or refertilized) Sub-Continental Lithospheric Mantle (SCLM) beneath northern Victoria Land (NVL, Antarctica). Prior to xenoliths entrainment by the host basalt, the Antarctic SCLM may have stored 0.2 vol% melt and 1.1 vol% fluids, mostly as FI trails inside mineral phases but also as inter-granular fluids. The amount of CO2 stored in FI varies from 0.1 μg(CO2)/g(sample) in olivine from the anhydrous mantle xenoliths at Greene Point and Handler Ridge, up to 187.3 μg/g in orthopyroxene from the highly metasomatized amphibole-bearing lherzolites at Baker Rocks, while the corresponding bulk CO2 contents range from 0.3 to 57.2 μg/g.
Irrespective of the lithology, CO2 partitioning is favoured in orthopyroxene and clinopyroxene-hosted FI (olivine: orthopyroxene = 0.10 ± 0.06 to 0.26 ± 0.09; olivine: clinopyroxene = 0.10 ± 0.05 to 0.27 ± 0.14). The H2O/(H2O + CO2) molar ratios obtained by comparing the CO2 contents of FI to the H2O amount retained in pyroxene lattices vary between 0.72 ± 0.17 and 0.97 ± 0.03, which is well comparable with the values measured in olivine-hosted melt inclusions from Antarctic primary lavas and assumed as representative of the partition of volatiles at the local mantle conditions. From the relationships between mineral chemistry, thermo-, oxy-barometric results and CO2 contents in mantle xenoliths, we speculate that relicts of CO2-depleted mantle are present at Greene Point, representing memory of a CO2-poor tholeiitic refertilization related to the development of the Jurassic Ferrar large magmatic event. On the other hand, a massive mobilization of CO2 took place before the (melt-related) formation of amphibole veins during the alkaline metasomatic event associated with the Cenozoic rift-related magmatism, in response to the storage and recycling of CO2-bearing materials into the Antarctica mantle likely induced by the prolonged Ross subduction.
•Significant amounts of CO2 stored in inter- and intra-granular fluids in the mantle.•CO2 mobility is linked to the geodynamic evolution of the Antarctica SCLM.•CO2 is systematically partitioned between mineral phases in the peridotitic system.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Solutions based on the action of diammonium hydrogen phospha are used as consolidants for carbonate stones.•4D SR-μCT is employed to monitor the effects induced during the consolidating treatment on ...the same sample.•The reaction process is shown as time-dependent, with significant changes occurring within the first hour of treatment.•Changes in the stone's porous microstructure are shown and demonstrated.•The effect of solution molarity on the consolidating process is asserted.
Diammonium hydrogen phosphate (DAP) solutions are used as consolidants for carbonate stone materials through the crystallization whithin the original matrix of newly formed crystalline phases. However, the formation mechanism of the new phases within the stone microstructure, and their effects on the porous system, strongly depend on the DAP molarity, the treatment method, and the stone microstructure. In this study, we obtained real-time quantitative information on the structural evolutions induced by the treatment process on the Noto limestone, a porous carbonate stone used as a building stone since antiquity, by synchrotron X-ray Microtomography. With the aid of 4D image analysis, microstructural modifications in terms of porosity, interconnection, and pore size distribution have been demonstrated in different stadia of the consolidation process, and the influence of molarity was asserted. This study paves the way for a deeper understanding of consolidation mechanisms and the effects induced overtime on the 3D microstructural features of porous materials by inorganic treatment.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
PDF
