DMEX Centre for X-ray Imaging

This first multidisciplinary study simulating the H 2 arrival in deep aquifers used as geological storage shows the importance of microorganisms.

A methanol extract of the bark of Bocconia arborea was fractionated on silica gel and the fractions analysed using gas chromatography coupled with mass spectrometry (GC-MS). Several benzophenanthridine alkaloids were identified including dihydrosanguinarine, oxysanguinarine, 11-acetonyldihydrochelerythrine, dihydrochelerythrine, chelerythrine, chelerythridimerine and angoline as the principal constituents. The results show that the direct GC-MS analysis of these alkaloids is possible with a clear distinction between the compounds. The technique is shown to be a valuable tool and an alternative technique to classical phytochemical procedures permitting the fast analysis of alkaloids mixtures.

Massive storage of dihydrogen (H2) in underground geological storage (UGSs) will be necessary to meet future H2 production ambitions. Such storage in deep aquifers was simulated in a high-pressure reactor, and the evolution of the 3 phases (natural gas/H2, formation water and rock) with autochthonous microorganisms was monitored over several weeks. These results show that methanogens do not necessarily dominate the community, but that sulfate-reducing activity and formate bioproduction are systematically present. The experimental data were fed into a biochemical model in PHREEQC to better understand the interplay between the phenomena observed. In particular, it was shown that the microbial activities associated with H2 consumption led to alkalinisation, which could explain, at least in part, the slower rate at which H2 disappeared, even if sufficient CO2 and sulfate remained in the system. Combined with a supposed local nutrient depletion, these results are encouraging for H2 storage in deep aquifers.

Abstract Hydrothermal dolomitization is an important diagenetic process that occurs in tectonic environments worldwide and forms conventional reservoirs associated with ore deposits and hydrocarbon accumulation, while forming efficient reservoirs for carbon sequestration. However, the current state of knowledge about the availability and reaction rate of Mg in dolomitizing fluids fails to explain the large volumes of hydrothermal dolomites geobodies observed in extended margins or in fold‐and‐thrust belts. To better understand this widespread phenomenon, it is essential to recognize the governing and limiting transport mode of the dolomitizing fluid. This contribution investigates the chemical and physical patterns developed between the original calcite and the newly formed dolomite. An extensive analytical study of well‐preserved dolomitization interfaces observed at outcrop scale in Callovian–Oxfordian limestones in the Layens anticline (north‐western Pyrenees, France) is presented. Through the use of scanning electron microscopy, electron backscattered diffraction, X‐ray microtomography, laser ablation inductively coupled plasma mass spectrometry (and mapping), the replacement related variations in elementary content, rock density, crystallographic properties and phase volumes and distribution were constrained. The results indicate a sequence of replacement, beginning with a fluid which starts to infiltrate the host rock by advection in the grain boundary network causing at the same time the replacement of calcite by diffusion‐limited dissolution and associated dolomite precipitation. The progressive replacement of calcite grains by dolomite is led by dissolution inside the grain enhanced by replacement related porosity creation, leading to a progressive decrease of local calcite grain size isolated as islands until the replacement is complete. The replacement of calcite by dolomite led to a mass loss without volume change, through generation of ca 11 vol.% porosity. Based on analytical observations of a natural sample, a conceptual model that accounts for the transport mode governing the different steps of hydrothermal dolomitization at crystal‐scale is proposed.

Hypoglycaemic activity-guided fractionation together with chemical analysis led to the isolation of 12-ursene and a novel triterpene 23,24 dimethyl-24-ethyl-stigmast-25-ene from the chloroform extract of the dried stem of A. mexicana. Identification was based on spectroscopic methods. The isolated triterpenes were tested for hypoglycaemic activity in normal and alloxman-diabetic CD1 mice 25-30 g at a dose of 50 mg/kg body weight. The blood glucose levels were determined before and 1.5, 3, 4.5 and 24 h after intraperitoneal drug administration. The results showed that the triterpenes produced a significant hypoglycaemic effect in normal as well as in diabetic mice. Comparison was made between the action of the triterpenes and a known hypoglycaemic drug, tolbutamide (50 mg/kg). The 12-ursene was found to be slow and less effective than tolbutamide, and the 23,24 dimethyl-24-ethyl-stigmast-25-ene was shown to be more effective than tolbutamide.

Hydroquinone (HQ) is known to form organic clathrates with some gaseous species such as CO 2 and CH 4 . This work presents spectroscopic data, surface and internal morphologies, gas storage capacities, guest release temperatures, and structural transition temperatures for HQ clathrates obtained from pure CO 2, pure CH 4, and an equimolar CO 2 /CH 4 mixture. All analyses are performed on clathrates formed by direct gas–solid reaction after 1 month’s reaction at ambient temperature conditions and under a pressure of 3.0 MPa. A collection of spectroscopic data (Raman, FT-IR, and 13 C NMR) is presented, and the results confirm total conversion of the native HQ (α-HQ) into HQ clathrates (β-HQ) at the end of the reaction. Optical microscopy and SEM analyses reveal morphology changes after the enclathration reaction, such as the presence of surface asperities. Gas porosimetry measurements show that HQ clathrates and native HQ are neither micro- nor mesoporous materials. However, as highlighted by TEM analyses and X-ray tomography, α- and β-HQ contain unsuspected macroscopic voids and channels, which create a macroporosity inside the crystals that decreases due to the enclathration reaction. TGA and in situ Raman spectroscopy give the guest release temperatures as well as the structural transition temperatures from β-HQ to α-HQ. The gas storage capacity of the clathrates is also quantified by means of different types of gravimetric analyses (mass balance and TGA). After having been formed under pressure, the characterized clathrates exhibit exceptional metastability: the gases remain in the clathrate structure at ambient conditions over time scales of more than 1 month. Consequently, HQ gas clathrates display very interesting properties for gas storage and sequestration applications.

We examine how fluids mix in three-dimensional (3D) porous materials due to differences in density which represent one mechanism of underground carbon dioxide storage. The experiment closely matched the simulation in terms of the patterns and speed of mixing. Interestingly, the experiment reveals columnar plumes self-organizing into a reticular pattern, previously seen only in 3D simulations. Results demonstrate quantitative matching over time in concentration, variance, scalar dissipation rate, and dissolution flux. A new relation between dissipation rate and flux is established, highlighting a 30% higher flux in 3D versus 2D systems, affirming prior estimations.

The objective of this work is to compare three techniques for characterizing the morphology of porous bio-based carbon foam, namely mercury intrusion porosimetry, scanning electron microscopy and X-ray microtomography.

High Resolution Image Download MS PowerPoint Slide The successful integration of dihydrogen (H 2 ) as an energy vector relies on effective seasonal storage in underground facilities like deep aquifers. However, the viability of this storage remains uncertain due to the unclear behavior of indigenous microorganisms in the presence of H 2, which could influence the gas composition. While modeling can inform H 2 dynamics, reactor-scale experiments are needed for validation. In our study, we used a high-pressure reactor to simulate injecting 2% H 2 into a gas storage aquifer currently used for natural gas (CH 4, 1% CO 2 ), utilizing formation water and rock samples from the aquifer. Our research led to a kinetic model that analyzes the interactions among gas, water, rock, and microbial activities. We found that microorganisms consumed H 2 and caused alkalinization, which inhibited further microbial growth and respiration. This suggests that after an initial decrease in H 2 concentration, the gas storage may be stabilized in deep aquifers. Reducing CO 2 levels is vital as CO 2 can hinder alkalinization and enhance sulfate-reducing, methanogenic, and acetogenic activities. Notably, while H 2 -utilizing microorganisms were predominant, both methanogens and sulfate-reducers showed significant activity. Overall, our findings provide insights into the potential for underground H 2 storage in deep aquifers, guiding future research and energy storage applications.

Natural hydrogen (H 2 ) emanations in intracratonic areas offer potentially exploitable carbon-free energy. To date, H 2 seepages have been detected in more than sixty sites with exploration ongoing in many locations. One mechanism of natural hydrogen generation is the oxidation of Fe 2+ in Fe-rich lithologies , and estimating the potential for hydrogen generation by this pathway is an important aspect of characterizing H 2 -generating rocks. However, accurate estimation of Fe 2+ can be challenging due to large-scale heterogeneities and small sample sizes used in conventional analysis. Here, we propose a correlative imaging technique to assess H 2 generation potential in Fe 2+ -rich source rocks by integrating 2D chemical information with 3D volumes of the rock imaged using X-ray computed tomography (micro-CT). The advantage of this method lies in its ability to analyze a whole drill core of the source rock to obtain the most representative values while preserving sample integrity. Our method, validated on fractured monzo-diorite from a natural H 2 -emitting well in Kansas, USA , yields an estimate of 707.93 ± 49.18 mol (H 2 )/ton (source rock), as the upper limit. The proposed method could be useful in characterizing source rocks and estimating their natural H 2 generation potential in the early stages of natural H 2 exploration.

Advanced in-situ characterization methods are crucial for comprehending how solid-state batteries evolve during cell cycling and to identify responsible factors for cell failure. In this study, we advocate for the use of laboratory-based in-situ X-ray tomography as a screening technique to non-invasively monitor the structural evolution of the cell of interest. The detected features of interest can be subsequently analysed by spectroscopic, microscopic and spectrometric techniques. To illustrate the proposed approach, we study the evolution of a Li symmetric cell while cycling from the pristine state up to cell failure. Pre-screening with in-situ X-ray tomography provides 3D images of the interface and suggests the occurrence of electrolyte thickening, puncturing and contact loss. These observations are consistent with impedance measurements conducted while cycling. Post-mortem XPS-analysis identifies lithium salt and organic compound accumulation on the electrolyte after cycling, providing a possible explanation for the observed electrolyte thickness increment. SEM images give visual proof of the interfacial contact loss, and Auger mapping gives further confirmation of the XPS data. This case study illustrates that pre-screening using laboratory-based in-situ X-ray tomography, combined with in-depth analysis techniques, helps to advance our understanding of buried interfaces in solid-state batteries and to identify responsible factors for cell failure.

This study aims to evaluate the self-sealing capacity of the Boom Clay when perturbed by an alkaline plume, by investigating the long-term evolution of hydraulic conductivity and mineralogical changes in fractured Boom Clay upon interaction with highly alkaline solutions. In a first step, percolation experiments were conducted on undisturbed clay samples using Young Cement Water (YCW, pH of 13.5) and Evolved Cement Water (ECW, pH of 12.6), both parallel and perpendicular to bedding planes. Hydraulic conductivity (K) in these alkaline environments were estimated, confirming the previous studies, with higher horizontal than vertical hydraulic conductivity as a result of the natural anisotropy of the Boom Clay. In a second step, clay samples were fractured. All samples experienced a significant increase in K, followed by a progressive decrease, indicative of an efficient self-sealing. This self-sealing process was visualized using X-ray micro computed tomography and spectral micro computed tomography analysis. In addition, mineralogical analyses, including specific surface area and pore size distributions from N 2 -physisorption, (Quantitative) X-ray diffraction and Fourier Transform Infrared spectroscopy analysis were conducted. They revealed partial dissolution of smectite in YCW environments but no significant mineral alteration in ECW-percolated samples. N 2 -physisorption experiments of the post-mortem samples indicated decrease of the specific surface area and concomitant decrease in the microporosity in all studied cases. Though the decrease in the specific surface area and microporosity can be explained by partial dissolution of smectite in the YCW environment, the shift of the pore size distribution towards larger pores can be linked to relative density changes in the vicinity of the fractures and overall increase in hydraulic conductivity. The results confirmed that Boom Clay retains its self-sealing capacity, even after prolonged exposure to high-pH conditions. This study provides valuable insights into the hydro-mechanical and mineralogical response of Boom Clay, essential for assessing its long-term behaviour as a geological barrier.

The investigation of destruction processes in composite materials is a current problem for their structural application and the improvement of their functional properties. This work aimed to visualize structural changes induced in layered carbon fiber reinforced plastics (CFRP) with the help of synchrotron X-ray microtomography. This article presents the details of destructive processes in the early stages of the deformation of reinforced polymers under uniaxial stretching, investigated at the micro level. Individual structural elements of the composite-filaments, parallel fiber bundles, the nonuniformity of the polymer binder distribution, and continuity defects-were observed under an external load. We have considered the influence of the material architecture and technological defects on fracture evolution in cross-ply and quasi-isotropic fiber-reinforced plastics. The results indicate the sequence of irreversible structural changes before the destruction of the material.

Historical monuments, outdoor stone sculptures, and artworks made of porous materials are exposed to chemical and physical degradations over time. Presently, the most promising route for consolidation of weakened porous materials is the injection of viscoelastic solutions of polymerizing compounds. Those compounds, after injection, undergo a sol-gel transition inside the porous media through evaporation of the solvent. Finding a suitable gelifying solution as a consolidant calls for understanding the drying kinetics of viscoelastic fluids in porous media. Here, we present a multiscale study of the drying kinetics of fluids during the sol-gel transition in porous materials using NMR and x-ray microtomography techniques. We find that from the early stage of the drying, a heterogeneous desaturation develops and advances from the free surface of evaporation towards the inner parts of the stone. We identify different drying periods, which appear to be dependent on the intrinsic properties of the porous medium influencing strongly the homogeneity of the final gel distribution within a treated stone. Our findings not only are relevant for the consolidation of porous artworks but also for civil and soil engineering processes where the fluids considered are generally more complex than water.

The massive arrival of biomethane in geological energy storage will lead to a co-injection of O 2 used during the gas desulfurization process. O 2 induces changes in the microbial community and interactions with the stored gas and formation water.

Three-dimensional photoactive self-standing porous materials have been synthesized through the integration of soft chemistry and colloids (emulsions, lyotrope mesophases, and P25 titania nanoparticles). Final multiscale porous ceramics bear 700–1000 m 2 g –1 of micromesoporosity depending on the P25 nanoparticle contents. The applied thermal treatment does not affect the P25 anatase/rutile allotropic phase ratio. Photonic investigations correlated with the foams’ morphologies suggest that the larger amount of TiO 2 that is introduced, the larger the walls’ density and the smaller the mean size of the void macroscopic diameters, with both effects inducing a reduction of the photon transport mean free path ( l t ) with the P25 content increase. A light penetration depth in the range of 6 mm is reached, thus depicting real 3D photonic scavenger behavior. The 3D photocatalytic properties of the MUB-200(x) series, studied in a dynamic “flow-through” configuration, show that the highest photoactivity (concentration of acetone ablated and concentration of CO 2 formed) is obtained with the highest monolith height (volume) while providing an average of 75% mineralization. These experimental results validate the fact that these materials, bearing 3D photoactivity, are paving the path for air purification operating with self-standing porous monolith-type materials, which are much easier to handle than powders. As such, the photocatalytic systems can now be advantageously miniaturized, thereby offering indoor air treatment within vehicles/homes while drastically limiting the associated encumbrance. This volumetric counterintuitive acting mode for light-induced reactions may find other relevant advanced applications for photoinduced water splitting, solar fuel, and dye-sensitized solar cells while both optimizing photon scavenging and opening the path for the miniaturization of the processes where encumbrance or a foot-print penalty would be advantageously circumvented.

The anisotropy and fabric of oil shales have been extensively studied because they are related to petrophysical properties, such as texture, composition, and porosity. Usually, this information is retrieved by applying a variety of methods, e.g., acoustic, anisotropy of magnetic susceptibility (AMS), X-ray microscopy imaging, and conductivity, that are sensitive to different physical properties of rocks. Among them, one of the least developed has been the method that measures dielectric permittivity. Although encouraging results have been published a few decades ago, it has not been widely developed mainly due to experimental difficulties. Recent research using terahertz time-domain spectroscopy (THz-TDS) for measuring anisotropy of shales seems to overcome previous constraints. However, it has not been proposed to estimate the dielectric fabric. Hence, we therefore set out to carry on this study. In particular, this method has the advantage of being non-invasive, and its sub-millimeter spatial resolution allows for characterization of the bulk fabric between the micro- and mesoscales, which is something that is not possible with current standard methods. In addition, we compare for the first time to our knowledge the THz dielectric fabric to those acquired by acoustic, AMS, and X-ray microtomography imaging measurements. The results show that THz-TDS allows for more accurate fabric characterization and more sensibility to discriminate the degree of shale anisotropy.

Abstract Understanding the fabric of rigid grains in strained shales is essential for predicting transport or mechanical properties. Fabric analysis of rigid grains is also key to infer deformation mechanisms in fine‐grained materials. In this study, we investigate the quartz shape fabric of two millimeter‐sized drill cores of tectonically deformed shales by means of X‐ray microtomography. The samples originate from the Jaca basin (Spain) and present a slaty cleavage perpendicular to the bedding. The representativeness of fabric data and heterogeneities are characterized at the microscale and compared with published magnetic fabric data. We extract both the individual grain data and the bulk data in sub‐volumes of increasing dimensions, and focus on identifiers, such as feature size, anisotropy, and shape. In the second step, the spatial heterogeneity of the matrix is assessed. We show that the bulk quartz fabric of a single millimeter‐sized sample is consistent with the magnetic fabric obtained based on a large number of centimeter‐sized samples. Yet, the individual grain analysis demonstrates that this bulk fabric hides a competition between two planar fabrics (bedding and cleavage), where both act differently depending on the grain size and morphology. Inter‐sample comparison reveals the existence of a petrofabric with a characteristic length that exceeds the sample size. These insights are directly applicable to the study of the bulk fabric at a larger scale. In this way, X‐ray microtomography complements petrophysical measurements in shales and helps to avoid misinterpretation of the rock fabric based on bulk measurements.

Salt weathering poses significant challenges to the durability and integrity of construction materials across various engineering applications. This study introduces a novel accelerated salt weathering protocol designed for standardised laboratory testing, aimed at evaluating the effects of salt crystallisation on natural rocks and construction materials. The protocol was validated using three distinct materials: Flysch rocks, Vosges sandstone, and high-performance concrete. The core protocol features continuous partial immersion of cylindrical-shaped samples in a 3 molal sodium sulphate solution at 32 °C. At the same time, room temperature is maintained at 20 °C, providing well-defined boundary conditions for easy reproducibility and potential numerical modelling. Non-destructive monitoring techniques, including time-lapse photography coupled with Digital Image Correlation (DIC) and acoustic emission (AE) analysis, were integrated into the core protocol. In addition, post-mortem X-ray tomography and optical microscopy were used to characterise salt-induced crack patterns further. The Flysch rock samples exhibited significant external deterioration, with DIC analysis highlighting the influence of material heterogeneity in damage susceptibility. AE analysis captured internal damage progression and identified the onset of salt-induced deterioration in the Vosges sandstone samples, which displayed consistent responses to the weathering test protocol. The concrete samples, pre-cracked by mechanical loading to mimic on-site coastal erosion conditions, exhibited salt-induced crack propagation and development of new salt-induced cracks when tested under the weathering protocol. These findings demonstrate the protocol’s effectiveness in evaluating salt-induced damage in construction materials, providing a reproducible framework that can be readily implemented in diverse testing environments to enhance durability assessment in engineering applications. • A novel accelerated salt weathering protocol is introduced for standardized laboratory testing. • The protocol features continuous partial immersion in a sodium sulphate solution under controlled temperature conditions. • Non-destructive monitoring techniques track real-time damage evolution and post-mortem analysis reveals salt-induced crack patterns. • The protocol successfully evaluates salt-induced damage in Flysch rock, Vosges sandstone, and high-performance concrete. • The study provides a reproducible framework to improve durability assessments in construction materials.

Differentiating minerals using high-resolution X-ray tomography (µCT) relies on distinct differences in the attenuation coefficient µ . The µ value depends on an interplay between the material density ρ and the effective atomic number Z eff of a mineral phase. Difficulties in identifying mineral phases arise when this interplay gives similar µ values and thus limited contrast within µCT images. Untangling these two dependencies is essential to improve the three-dimensional chemical identification of critical minerals. Lab-based methods and techniques often incorporate different measures, but only show a limited application potential on multiphase geological samples. Using high- Z spectral laboratory-based µCT we studied the potential of directly identifying chemical elements within the practical margins of high- Z spectral detectors. This paper compares the results from three mineral deposits using two spectral µCT setups. Chemical elements with a Z higher than molybdenum and a concentration of at least some weight percentage were correctly identified using K-edge imaging. The suitability of the different high- Z spectral detectors depends largely on the availability of prior knowledge of the sample composition. Quantifying elemental concentrations is element- and sample specific and currently does not allow for optimal automated mineralogy solutions. Improving the three-dimensional identification of minerals can be achieved with dedicated analyses of the energy-dependent µ curve and therefore will remain the focus of future work. • Comparison between different high- Z spectral laboratory-based µCT setups. • K-edge identification of chemical components with an atomic number larger than Mo. • Differentiation between mineral phases with a similar µ rec in standard µCT scans.