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The Cholla cactus is a species of cacti that survives in arid environments and produces a unique mesh-like porous wood. In this article, we present a comprehensive investigation on the hierarchical structure and micromechanical properties of the Cholla cactus wood. Multiple approaches consisting of X-ray tomography, scanning electron microscopy, scanning probe microscopy, nanoindentation, and finite element simulations were used to gain insight into the structure, property, and design principles of the Cholla cactus wood. The microstructure of the Cholla cactus wood consists of different components, including vessels, rays, and fibers. In the present study, we quantitatively describe the structure of each of these wood components and their likely functions, both from the perspective of biological and mechanical behavior. Nanoindentation experiments revealed for the first time that the cell walls of the fibers exhibit stiffness and hardness higher than those of rays. Furthermore, the idea of making porous, thin-walled cylinders was abstracted from the design of vessel elements, and the structures inspired by this principle were studied in tensile and torsional loading conditions using finite element simulations. Finite element simulations revealed that the utilization of a larger volume of material to carry the load leads to an increase in toughness of these structures, and thus suggested that the pores should be architected to maximize the distribution of load. The Cholla cactus wood possess a unique hierarchical structure that enables it to thrive in arid environments. Our correlative microscopy approach reveals incredible strategies that individual wood components exhibit to enable the survival of Cholla cactus in extreme environments. The present work quantifies the microstructure and mechanical properties of this very interesting natural system. We further investigate a design principle inspired by the vessel elements, one of the wood components of Cholla cactus, using finite element simulations. The study presented here advances our understanding of the structural significance of Cholla cactus and potentially other desert plants and will further help design architected structural materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Ni-impregnated Gd 0.1 Ce 0.9 O 2 and Y 0.08 Zr 0.92 O 2 fuel electrodes for solid oxide cells are manufactured by the combination of the freeze tape casting and infiltration techniques. Their morphological properties are investigated by scanning electron microscope and X-Ray microtomography while their electrochemical performance is evaluated in symmetrical Y 0.08 Zr 0.92 O 2 -supported button cells by electrochemical impedance spectroscopy. The microstructural analysis of the manufactured scaffolds highlights the characteristic anisotropy of porosity provided by the freeze tape casting method. The average tortuosity factor across the out of plane direction has been calculated equal to 1.38, being considerably lower than the average values of the other components, (τ x = 10.2) and (τ y = 6.87). The contribution provided by gas diffusion to the overall polarization resistance of the freeze tape cast electrodes has been estimated around 6·10−4 Ω cm2 in the 600–750 °C temperature range, thus lower than the best reported values for the state-of-the-art electrodes featuring sponge-like porosity. The measured impedance data highlighted the higher electrochemical performance of the Ni-impregnated Gd 0.1 Ce 0.9 O 2 architecture, holding a polarization resistance of 0.823 Ω cm2 at 750 °C, which is regarded as a very promising result for a ∼600 μm thick electrode. The interpretation of the impedance data was supported by the distribution of relaxation times analysis and the complex non-linear least square fit. In particular, the electrochemical investigation highlighted the presence of two major resistive contributions which have been ascribed to the occurrence of a chemical capacitance within the GDC10 lattice (low frequency contribution) and to the multi-layered architecture of the tested symmetrical cells which increases the contact losses (high frequency contribution). • The electrode design optimization is expected to increase its electrochemical performance. • Nanostructured graded porous electrodes for SOCs are shaped combining freeze tape casting and infiltration. • The anisotropy of gas diffusion channels is highlighted by the 3D reconstruction of the GDC10 scaffold. • The Ni-infiltrated GDC10 freeze tape cast scaffold is measured to be the best performing electrode architecture. • The electrochemical performance of the Ni-GDC10 electrode is mainly hindered by its low electronic conductivity. [ABSTRACT FROM AUTHOR]

This work focuses on the analysis of the combined effect of intermetallic, interlocking, and voids on the joint strength of Al6061 and AZ31 Mg dissimilar friction stir welds. The FSW of Al6061 and AZ31 Mg is performed with different tool rotation speeds and feed rates. Tensile test specimens are prepared from these joints and subjected to X-ray tomography, which reveals the serrations and voids at the Al6061/AZ31 interface. Here, Serrations interlock the materials and increase the interface area. Serrations pitch is higher in shoulder driven region (1.4 – 0.6 mm) compared to pin driven region (0.5 – 0.2 mm). The Al6061 and AZ31 Mg interface is also accompanied by voids, where void fraction is around 0 % near the top and 2–7 % near the bottom. SEM, EDS mapping, and XRD 2-theta scans of the Al6061/AZ31 Mg interface are utilized to investigate the intermetallic compounds. Al 3 Mg 2 and Al 12 Mg 17 intermetallic compounds are observed at Al6061/AZ31 Mg interface. Further, the intermetallic compound thickness increases from 2.8 μ m to 5.3 μ m with increase tool rotational speed from 500 rpm to 800 rpm. Based on the variation of joint strength against these parameters, the intermetallic compound thickness is the most detrimental contributor to the joint strength, followed by void volume and interface area, for the Al6061 and AZ31 Mg dissimilar joints. The maximum joint strength of 112.1 MPa is achieved, which is 40 % and 33 % of AZ31 Mg and Al6061, respectively. [ABSTRACT FROM AUTHOR]

This paper explores the influence of incorporating microencapsulated Phase Change Materials (MPCM) on the evolution of both mechanical behavior and meso-structural damage in mortars in response to prolonged freeze-thaw conditions, employing Differential Scanning Calorimetry (DSC) for thermal analysis, comprehensive mechanical performance experiments, and high-resolution X-ray Tomography (XRT) to assess internal damage evolution. The DSC results highlight the thermoregulatory effect of MPCM, which influences the performance of the mortars under freeze-thaw conditions. Mechanical experiments show a trade-off between initial strength and long-term durability, with MPCM-enhanced mortars demonstrating significantly reduced strength loss when exposed to extended freeze-thaw cycles compared to control mortars. XRT images further corroborate these outcomes, illustrating less pronounced meso-structural degradation in MPCM-containing samples when exposed to extended freeze-thaw cycles. Overall, the findings in this paper reveal that MPCM-infused mortars, particularly those with higher MPCM concentrations, exhibit significantly reduced internal damage and maintain better mechanical integrity compared to control samples. Collectively, these insights suggest that MPCM integration could be a pivotal strategy for designing more resilient and durable cementitious composites, paving the way for future advancements in construction practices tailored to withstand the challenges of freeze-thaw conditions. • MPCM-incorporation results in prolonged and consistent latent heat release in mortars. • MPCMs reduce ice formation during crystallization, mitigating freeze-thaw damage. • MPCM-integrated mortars show reduced strength loss over prolonged freeze-thaw cycles. • X-ray Tomography reveals less microstructural freeze-thaw damage in MPCM-mortars. [ABSTRACT FROM AUTHOR]

Boiler water walls experience in-phase thermo-mechanical loading during start-ups and shut-downs, leading to low cycle fatigue (LCF) failure. This study aims at establishing an FEA-based failure prediction method for estimating the fatigue performance and service life of the welded water walls. The developed model is validated for predicting failure in the defect-free uniaxial fatigue specimens. Stress-mechanical strain hysteresis loops and accumulated inelastic strain energy density per cycle parameters are extracted from fatigue tests at 0.4%, 0.6%, and 0.7% strains. A combination of cyclic plasticity and continuous damage mechanics (CDM) theory is utilized to predict fatigue crack initiation sites and estimate the specimen fatigue life. Accumulated damage has been calculated for the life cycle of each specimen. FEA model predicted failure and service life agrees well with the experimental results. The established failure analysis parameters are then transferred from the specimen level to the water wall component level, thereby estimating the service life of defect-free water walls at 750 cycles. • Cyclic plasticity, damage, and failure of defect-free water wall uniaxial fatigue specimens subjected to in-phase thermo-mechanical loading are anlyzed. • Plasticity and continous damage mechanics theories have been used to predict fatigue initiation and crack propagation. • The model is successfully applied to water wall assemblies. [ABSTRACT FROM AUTHOR]

In this study, a new barrier material was synthesized using biochar to modify the cement-bentonite (CB) system. The optimal doping of biochar in the CB system was determined to be 20 % through mechanical performance, gas permeability and adsorption efficiency tests. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicated that biochar enhanced the hydration of the cement system and the fixation of carbon dioxide. Adsorption kinetics and isotherm experiments indicated that the adsorption reaction of the material to phenol was more consistent with the pseudo-second-order kinetic model and the Freundlich model. Diffusion tests revealed that the average effective diffusion coefficient of the material at different NaCl concentrations was 8.980×10⁻¹² m²/s. The X-ray tomography and finite element simulation results indicated that the sample had an average pore radius of 15.66 μm, with poor permeability and low pore connectivity. The study on engineering performance indicated that the service life of the cutoff wall increased with the thickness and the flow resistance coefficient. Service life calculations and Visual MODFLOW simulations showed that the CBB-2 cutoff wall has significant durability and barrier effect to phenol. [Display omitted] ● Biochar was used as modifier in cutoff walls to enhance the mechanical properties. ● Biochar can improve the carbon sequestration capacity of cementitious composites. ● The cutoff walls had good anti-seepage and barrier properties for phenol. ● Internal structural parameters were analyzed through the pore-scale modeling. ● The barrier ability of cutoff walls for phenol was simulated by Visual MODFLOW. [ABSTRACT FROM AUTHOR]

As climate variability intensifies the frequency and severity of freeze-thaw cycles, the development of cementitious materials capable of withstanding these harsh conditions becomes increasingly crucial. This research focuses on the potential of Microencapsulated Phase Change Materials (MPCMs) to enhance the durability of Hardened Cement Paste (HCP) in the face of such challenges. Specifically, this paper evaluates the influence of MPCMs on evolution of pore microstructure, damage, and micromechanical response in HCP subjected to extended freeze-thaw cycles, utilizing Low-Temperature Differential Scanning Calorimetry (LTDSC), X-ray Tomography (XRT), and micro-indentation. LTDSC results indicate a lower ice-crystallization temperature and a significant reduction in ice formation in MPCM-integrated HCP. Micro-indentation experiments reveal that while the control HCP undergoes substantial decreases in indentation hardness (35 %) and Young's modulus (37 %) after 180 cycles, the MPCM samples show much lower losses (only 9 % loss in hardness and 7 % loss in Young's modulus for 20 % MPCM inclusion). XRT image analysis reveals that MPCMs mitigate pore enlargement, preserve a stable pore size distribution, and effectively reduce the risk of increased interconnected porosity in HCP when subjected to extended freeze-thaw cycles. Crack analysis demonstrates that control HCP samples exhibit significant crack propagation with increased freeze-thaw cycles, while samples with 10 % MPCM inclusion show only slight crack initiation, and those with 20 % MPCM inclusion maintained their structural integrity with virtually no crack progression after 180 freeze-thaw cycles. These findings underscore the potential of MPCMs to improve the durability of HCP against freeze-thaw damage, offering key insights for designing more robust materials. [ABSTRACT FROM AUTHOR]

Ultrastrong metallic alloys, possessing unparalleled load-bearing abilities, are coveted in many sectors, thus attracting growing research efforts. However, these alloys encounter persistent usability challenges posed by hydrogen embrittlement, which causes unpredictable fracture through crack initiation. Due to complex hydrogen-microstructure interactions and their exacerbation under high stress, advances in hydrogen resistance in ultrastrong materials are sparse throughout their long history. Herein, we report a quantum-mechanics-informed strategy for hydrogen tolerance enhancement in ultrafine-grain-hardened Al-Zn-Mg-Cu alloys, approaching their current strength limit of approximately 1 GPa. This method involves the incorporation of hydrogen-absorbing T-phase precipitates into nanograins, to substantially reduce hydrogen coverage at potential crack initiation sites. We demonstrate, via synchrotron radiation X-ray micro-/nano-tomography, scanning transmission electron microscopy and atom probe tomography, that nanoprecipitates successfully withstand shear strains exceeding 1000 and are exploitable essentials for ultra strength-hydrogen synergy, contrasting their often-assumed secondary roles in nanocrystalline alloys due to possible strain-induced dissolution, which has intuitively excluded exploring them as central elements. Our approach potentially inspires new hydrogen-resisting alloys across a broad strength-composition space. • The first exploration into hydrogen resisting Al alloys in ultra-strength domains. • Hydrogen-trapping precipitates are incorporated into ultrafine-grained Al alloys. • T phase precipitates improve hydrogen resistance and reduces crack percentage. [ABSTRACT FROM AUTHOR]

Current research on self-expanding super-elastic nitinol stents is mainly focused on designing geometries suited to the human venous and arterial systems. This study specifically considers a patented one-piece double cross-sectional stent designed to address venous stenosis affecting the vena cava, iliac veins, and their bifurcations. Before its placement within the vein, numerous tribological challenges arise as the stent slides along the guide-wire (so-called catheter). These are mainly connected to the lack of knowledge related to (i) its frictional behaviour and (ii) the level of contact pressure linked to the unknown real contact area between the compressed stent and the polytetrafluoroethylene (PTFE) catheter. This paper describes an original multi-scale approach, based on the Persson's contact theory, that allows determination of (i) the contact pressure, (ii) the evolution of the real contact area, and (iii) the shear stresses at the interface during the stent sliding. A topographical optimization criterion will finally be provided, enabling control of both friction and stick–slip phenomena at the stent-catheter interface. [ABSTRACT FROM AUTHOR]

Soil structure is a dynamic property which controls a wide range of soil functions and is closely linked with soil carbon content. The carbon contents of agricultural soils are subject to several ongoing trends, including declining carbon stocks and attempts to increase the soil carbon reserves. In this study, we aimed to quantify how organic soil amendments, which have been shown to reduce long-term nutrient loads from agricultural fields, can impact soil structure. The structural impacts of a large one-time addition (8 tons carbon per hectare, three different soil amendments) of pulp and paper mill side stream sludges to a boreal clay soil were explored quantitatively in aggregate (X-ray microtomography, sample size 1–2 mm), core (water retention measurements, sample size 195 cm3) and column (macropores ≥80 µm, sample size ∼ 20 dm3) scales. Our results showed no micrometer-scale structural changes within soil aggregates despite the large number (25 aggregate per treatment) of imaged samples. However, the organic soil amendments had a statistically significant impact on the macroporosity. The macroporosity was on average 20–27 % higher compared to the control samples and visible even five years after the application of the amendments. Such change in soil structure improves soil aeration and fast infiltration of water during wet periods and extreme rain events and may thereby also reduce erosion risk by decreasing surface runoff. The increased microporosity was visible only in the column scale. No statistically significant differences were observed in the fraction of large pores in core scale water retention measurements. Probing the soil structural changes in macropore regime by X-ray tomography or developing sub-micron scale analysis methods are recommended approaches to improve our understanding of clay soil's structural changes induced by organic soil amendments. • The effect of a large single dose of organic matter on soil structure was studied. • Soil structure was investigated from aggregate to column scale. • 100 aggregates imaged with X-ray tomography. • Differences in intra-aggregate porosity were not found. • Only macropores (≥80 µm) were affected by the organic soil amendments. [ABSTRACT FROM AUTHOR]

In the context of novel environmental and energy regulations in construction (RE2020), biocomposites derived from bamboo fibers, bamboo powders, and biodegradable poly(lactic)acid polymer, all of which are renewable resources, have been investigated to meet the criteria of the novel regulations. In this work, the biocomposites were manufactured by twin-screw internal mixing at 170 °C for 5 min with a rotation speed of 60 rpm. The composites sheets were then shaped on a hydraulic press at 185 °C. Pore characterization including pore volume fraction, 3D-pore structure and morphology, and pore distribution of these materials were investigated using X-ray tomography combined with image processing (Avizo). The results show that when the bamboo fibers content is increased, an augmentation in the pore volume fraction and the number of large-volume pores could be observed. In turn, the bamboo powder-containing sheet had a significant increase in pore volume fraction, while a higher quantity of smaller pores, with uniform size, could be observed. The water absorption capacity of these composite increases with the increase of the amount of pore distribution, pore connection, and pore volume fraction. In addition, the orientation of the fibers in 3D observation, flexural mechanical properties, and thermal stability of the biocomposites are also reported in this study. [ABSTRACT FROM AUTHOR]

• Macropore characteristics in arable topsoils were quantified using X-ray tomography. • The degree of preferential transport (PT) was determined under near-saturated conditions. • Macropore connectivity measures did not regulate the PT. • The PT was regulated by the abundance of mesopores and small macropores. • Increasing soil organic carbon may reduce the PT by its effects on pore size distribution. An improved understanding of preferential solute transport in soil macropores would enable more reliable predictions of the fate of agrochemicals and the protection of water quality in agricultural landscapes. The objective of this study was to investigate how soil organic carbon (SOC) and soil texture shape soil pore structure and thereby determine the susceptibility to preferential transport under steady-state near-saturated flow conditions. To do so, we took intact topsoil samples from an arable field that has large variations in SOC content (1.1–2.7%) and clay content (8–42%). Soil pore structure was quantified by X-ray tomography and soil water retention measurements. Non-reactive solute transport experiments under steady-state near-saturated conditions were carried out at irrigation rates of 2 and 5 mm h−1 to quantify the degree of preferential transport. Near-saturated hydraulic conductivities at pressure heads of −1.3 and −6 cm were also measured using a tension disc infiltrometer. The results showed that larger abundances of small macropores (240–720 µm diameter) and mesopores (5–100 µm diameter) resulted in weaker preferential transport, due to larger hydraulic conductivities in the soil matrix that prevented the activation of water flow and solute transport in large macropores. In particular, the degree of preferential transport was most strongly and negatively correlated with the mesoporosity in the 30–100 µm diameter class. In contrast, the degree of preferential transport was not correlated with connectivity measures (e.g. the percolating fraction and critical pore diameter for the macropore network), probably because i.) the pore space of almost all samples was highly connected, being dominated by one percolating cluster, and ii.) only a part of this percolating macroporosity was active under the near-saturated conditions of the experiment. We also found that the degree of preferential transport was strongly and negatively correlated with clay content, whilst the effects of SOC were not significant. Nevertheless, macroporosity in the 240–720 µm diameter class and mesoporosity were positively correlated with SOC content in our soils and in some previous studies. Therefore, SOC sequestration in arable soils may potentially reduce the risk of preferential transport under near-saturated flow conditions through better developed networks of small macropores and mesopores. [ABSTRACT FROM AUTHOR]

Structural inhomogeneity developed within compacted powders using punches with grooved surfaces, is a critical issue due the cracking tendency. This study aims to provide a better understanding of the structural inhomogeneity according to the design of the punch surfaces using a finite element modelling. Two case studies are compared. In this modelling, the Drucker-Prager Cap model with density-dependent parameters is considered while the density distributions of manufactured grooved compacts are determined using X-ray tomography. The structural inhomogeneity is then analysed with the goal to determine which punch design is likely to improve the homogeneity. The contact-stress, stress and density distributions within the compact are computed. Predictions of the density distributions are validated from the measurements and show high densified regions localized essentially under the grooves and decreases drastically towards the compact center. The inhomogeneity of structure generated by each punch design is explained by the resulting contact-stress and the wall friction. A notable improvement of the homogeneity is qualitatively showed using the design of five instead of two grooves which was confirmed by X-ray tomography images and modelling thanks to the regular distribution of contact-pressure over the powder bed, even though this last is not uniform. [Display omitted] • The structure inhomogeneity of two designs of grooved compacts is investigated. • The microstructure of grooved compacts is obtained from X-ray tomography images. • The contact-pressure, stress and density fields are computed using Finite Element Method. • Computed and measured density distributions are in good agreement. • The structural homogeneity of compacts with five grooves is qualitatively improved. [ABSTRACT FROM AUTHOR]

Multidimensional effects on hot-spot formation must be considered to better understand the current limits on the performance of direct-drive inertial confinement fusion experiments on OMEGA with cryogenically layered solid deuterium–tritium targets. A comprehensive reconstruction effort has been established at the Laboratory for Laser Energetics to infer hot-spot and shell conditions at stagnation from a large collection of x-ray, neutron, and particle detectors along multiple lines of sight. Several time-gated and time-integrated x-ray imagers are being used to record the shape of the hot-spot plasma. A 3D hot-spot x-ray emission tomography technique has been developed to infer low-mode drive asymmetries from the hot-spot shape. A suite of neutron diagnostics is used to provide measurements of hot-spot flow velocity, ion temperature, and areal density. The information obtained from the x-ray and neutron detectors will be combined into a coherent model of the shape of the hot spot and shell assembly. [ABSTRACT FROM AUTHOR]

• Zn-rich phases in Mg-6Zn-0.6Si- x Sn alloys formed an interconnected 3D network. • Volume fraction of Mg 2 Sn increased with Sn content in Mg-6Zn-0.6Si- x Sn alloys. • Sn addition improved strength due to solid solution and precipitation strengthening. • The ductility of Mg-6Zn-0.6Si- x Sn alloys increased by 15 % upon 4 wt% Sn addition. In this study, the role of varying Sn concentration (x = 0, 1, 2, 3 and 4 wt%) on the microstructure and mechanical properties of Mg-6Zn-0.6Si- x Sn alloys has been investigated. The type, distribution and volume fraction of the precipitates have been carried out using both scanning electron microscopy (2D) and X-ray tomography (3D). The Mg 2 Sn phase appeared after addition of 2 wt% Sn. The increase in the compressive strength of the alloy with increase in Sn addition has been attributed to both precipitation strengthening as well as solid solution strengthening. [ABSTRACT FROM AUTHOR]

We report the synthesis of plasmonic nanocapsules and the cellular responses they induce in 3D melanoma models for their perspective use as a photothermal therapeutic agent. The wall of the nanocapsules is composed of polyelectrolytes. The inner part is functionalized with discrete gold nanoislands. The cavity of the nanocapsules contains a fluorescent payload to show their ability for loading a cargo. The nanocapsules exhibit simultaneous two-photon luminescent, fluorescent properties and X-ray contrasting ability. The average fluorescence lifetime (τ) of the nanocapsules measured with FLIM (0.3 ns) is maintained regardless of the intracellular environment, thus proving their abilities for bioimaging of models such as 3D spheroids with a complex architecture. Their multimodal imaging properties are exploited for the first time to study tumorspheres cellular responses exposed to the nanocapsules. Specifically, we studied cellular uptake, toxicity, intracellular fate, generation of reactive oxygen species, and effect on the levels of hypoxia by using multi-photon and confocal laser scanning microscopy. Because of the high X-ray attenuation and atomic number of the gold nanostructure, we imaged the nanocapsule-cell interactions without processing the sample. We confirmed maintenance of the nanocapsules' geometry in the intracellular milieu with no impairment of the cellular ultrastructure. Furthermore, we observed the lack of cellular toxicity and no alteration in oxygen or reactive oxygen species levels. These results in 3D melanoma models contribute to the development of these nanocapsules for their exploitation in future applications as agents for imaging-guided photothermal therapy. The novelty of the work is that our plasmonic nanocapsules are multimodal. They are responsive to X-ray and to multiphoton and single-photon excitation. This allowed us to study their interaction with 2D and 3D cellular structures and specifically to obtain information on tumor cell parameters such as hypoxia, reactive oxygen species, and toxicity. These nanocapsules will be further validated as imaging-guided photothermal probes. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel ceramic composite has been obtained by introducing polyvinyl alcohol in magnesium-based chemically-bonded ceramics and exploiting the cross-link reaction with glutaraldehyde during setting. The properties of the obtained material and the interaction of the polymer with the cement reaction have been investigated. Several beneficial effects were observed. Namely, an extension of the working time, a reduction in the water sensitivity, a decrease in the rate of the heat evolution during hardening. The latter has been ascribed to the intervention of surface adsorption processes, which hindered the dissolution of MgO, as well as the nucleation and growth of the magnesium phosphate products, in concert with the film forming ability of the polymer. Thanks to the complementarity of their mechanical properties, the cement and the additive operated in a synergistic fashion, allowing for the obtainment of a material possessing higher strength and better elastic properties. Three-dimensional quantitative image analysis from synchrotron X-ray microcomputed tomography evidenced the development of a more compact microstructure, comprising a higher number of crystals of smaller size. As a consequence, the pore network exhibited a higher fraction of small pores and lower pore connectivity. These characteristics contributed to hinder the water absorption, as confirmed by the fluid transport simulations within the volume. The observed correlation between the solution pH and the polymer cross-link density offers the way to effectively modulate the material performance by acting on the chemical environment thanks to its compatibility with the cross-link reaction. [ABSTRACT FROM AUTHOR]

In this work a modelling approach for predicting density distribution in the vicinity of two facing grooves on a parallelepiped compact surface, is developed and results are validated using X-ray tomography. An experimental hybrid procedure is proposed to calibrate Drucker-Prager Cap model material parameters which are numerically validated and considered for FEM compaction simulation of grooved specimen using Arbitrary Lagrangian Eulerian method (ALE). Results of the predicted density show high values under the groove and low values on its flanks and shoulders. Similar findings were observed in the literature. Additionally, a strong density gradient between the facing grooves is predicted and validated, demonstrating that the calibrated model achieved good agreements with the measurements. The proposed hybrid calibration procedure could be used for other shape and size die not benefiting from radial instrumentation. Moreover, the ALE approach demonstrated its robustness in solving die powder compaction in presence of strong mesh distortions. [Display omitted] • Hybrid procedure for DPC model material parameters calibration. • Finite Element Modelling of die compaction using ALE adaptive meshing approach. • Density distribution predictions in the vicinity of grooved parallelepiped compact. • Validation of density distribution using X ray tomography. [ABSTRACT FROM AUTHOR]

In spite of many years of research, the physical phenomena leading to the evolution of compacted graphite (CG) during solidification is still not fully understood. In particular, it is unknown how highly branched CG aggregates form and evolve in the semi-solid, and how local microstructural variations at micrometer length scale affect this growth process. We present here the first time-resolved synchrotron tomography combined with a bespoke high-temperature environmental cell that allows direct observation of the evolution of CG and relates this dynamic process to the local surrounding microstructures in a cast iron sample during repeated melting and solidification. Distinct processes are identified for the formation of CG involving the nucleation, growth, development of branches and interconnection of graphite particles, ultimately evolving into highly branched graphite aggregates with large sizes and low sphericities. CG is found to nucleate with a spheroidal or a plate-like shape, developing branches induced by high carbon concentration, e.g. thin melt channels. Additionally, CG grows much faster than spheroidal graphite during subsequent cooling in solid state. The direct visualization of the dynamic solidification process provides unprecedented new insights into formation mechanisms of CG and correlating factors such as local microstructural variations, and guides the development of CG iron solidification models. [Display omitted] [ABSTRACT FROM AUTHOR]

Because of coal seam excavation and periodic disturbance of back-and-forth coal cutting, the surrounding rock is subjected to tiered cyclic unloading and loading. Based on this, a seepage experiment under constant axial stress and tiered cyclic unloading-loading confining pressure was carried out, and two new damage variables were proposed. These results showed that, the accumulative plastic deformations and corresponding permeability increased step-wise with unloading levels, permeability decreased with cycle number in the same unloading level when the unloading level was small, it was the opposite when the unloading level was large. The Kaiser effect and the Felicity effect actually coexisted during the experiment. As the unloading level increased, the relationship between dissipated energy and cycle number converted from logarithm to linear relationship. Two damage variables showed that the critical value of the damage variables for coal failure D c≈0.9. [Display omitted] • Effect of tiered cyclic unloading-loading conditions on permeability and deformation. • Proposed that the Kaiser effect and the Felicity effect actually coexist. • A new method for calculating dissipation energy of gas-bearing coal. • Damage characterization based on dissipation energy and deviatoric stress. • Damage characterization based on X-ray tomography. [ABSTRACT FROM AUTHOR]

Introduction: Distal radius fractures (DRF) are among the most frequent in the body. About one third of these fractures can result in malunion with restriction of movement and pain in the wrist, the treatment in these cases consists of corrective osteotomy of the deformity. Due to its three-dimensional (3D) complexity, careful preoperative planning is a fundamental step in correction. The prototyping from the 3D reconstruction of the computed tomography of the affected wrist, allows the real understanding of the deformity.Methods: Patients with malunion of the distal radius with indication for surgical treatment, from December 2019, were included in the group of corrective osteotomies through planning with prototyping in 3D printing. The postoperative functional outcome was assessed by the Disabilities of the Arm, Shoulder and Hand Score (DASH) and visual analogue scale (VAS). Radiographic data including radial inclination, volar tilt and joint step were recorded from standard posteroanterior and lateral radiographic views.Results: A total of 9 patients were included. The mean age was 47 years. The average postoperative DASH value of the patients was 24.9 and VAS was 3.6. Radiographically, the palmar tilt had an average improvement of 25.22°, and the radial inclination had an average improvement of 2°.Conclusion: Corrective osteotomy through planning with prototyping in 3D printing is an effective method of treating symptomatic distal radius malunions. The possibility of performing the osteotomy in a 3D model, simulating the surgery, making the procedure more predictable. [ABSTRACT FROM AUTHOR]

Fe is a common impurity element in recycled aluminum scraps, and adjusting Fe content can effectively promote the effective utilization of recycled aluminum. In this study, Al-Mg-Si-Mn-Fe alloys with different Fe contents were prepared by adding various percentage of aluminum scraps. Synchrotron X-ray tomography technology was used to study the morphological evolution of Fe-rich phases and corresponding effect on mechanical properties of studied alloys. The results showed that as the Fe content increased, the 3D morphology of Fe-rich phases changed from fine Chinese-script and needle-like shapes to coarse Chinese-script structure. Their 3D morphology was mainly composed of thin platelets and curved branches. The increase in Fe content did not significantly change the 3D structure of Fe-rich phases, but increased the volume fraction of large Fe-rich phases. When the Fe content reached 0.35 %, the maximum volume and the number of branches of individual phases increased by 182.9 % and 142.2 %, respectively, compared with the 0.2Fe alloy. With the increase of Fe content, the ductility of alloys gradually decreased, especially when the Fe content exceeded 0.25 %. The Fe content had a small effect on the liquidus temperature of alloys, but it changed the initial formation temperature and type of Fe-rich phases. When the Fe content exceeded 0.32 %, it promoted the formation of β-Fe phase, which may be the main reason for the significant decrease in ductility of studied alloys with higher Fe content. • The Al-Mg-Si-Mn-Fe alloys were successfully prepared with different Al scraps. • The 3D morphology of Fe-rich phase particles was reconstructed. • Increasing Fe content keep strength at similar lever while decreases elongation. [ABSTRACT FROM AUTHOR]

The evolution kinetics of hydrogen porosity during solid solution treatment (SST) of vacuum-cast Al–Cu–Li alloys and the effect of porosity defects on the mechanical properties of the alloys were investigated. It has been found that porosity at 6h SST was dominated by nucleation and its evoluton of fractions has a linear correlation with time, A P S = (0.05 ± 0.06)＋(0.11 ± 0.01) t. However, the growth of porosity at 12 h is evidenced by a decrease in the number of pores and an increase in the size of large pores, expanding inter-porosity distance due to Ostwald ripening. Three dimensional quasi- in situ X-ray CT quantification of porosity demonstrate that the hydrogen concentration at the interface in the early stages of the solid solution was not adequate to balance its surface tension and vacancies were created by cross-diffusion, reducing the interficial energy for porosity nucleation. The effects of porosity on the tensile strength satisfies lnσ-lnσ 0 = α ln fp , and those detrimental hydrogen porosities can be predicted by a multi-scale model which take into account hdyrogen diffusion during vacuum solution treatment. • Quantification and characterization of porosity nucleation and growth using two-dimensional metallographic techniques. • Quasi-in situ XCT was used to study the effect of holding time on porosity and to reveal the kinetic of porosity evolution. • Nucleation and growth mechanisms of porosity during solid solution treatment revealed from an atomic perspective. • Quantification of the effect of effective cross-sectional porosity on the tensile strength. • A scientific basis for the regulation of porosity defects in the solid solution treatment of Al–Cu–Li alloys. [ABSTRACT FROM AUTHOR]

In order to determine fiber volume contents (FVC) of low contrast CT images of carbon fiber reinforced polyamide 6, a novel thresholding method and a convolutional neural network are implemented with absolute deviations from experimental values of 2.7% and, respectively, 1.46% on average. The first method is a sample thickness based adjustment of the Otsu threshold, the so-called "average or above (AOA) thresholding", and the second is a mixed convolutional neural network (CNN) that directly takes 3D scans and the experimentally determined FVC values as input. However, the methods are limited to the specific material combination, process-dependent microstructure and scan quality but could be further developed for different material types. [Display omitted] • Alternative to experimental determination of FVC through CT image processing. • Convolutional neural network and novel thresholding technique. • Especially for low contrast material combinations. • Average absolute deviations of only about 2.7% (novel thresholding) and 1.46% (CNN). [ABSTRACT FROM AUTHOR]

The existing structural characterization methods of building materials as well as thermal conductivity calculation models can not be directly applied when considering fibrous building thermal insulation materials with intricate skeletons. In this study, rock wool is considered the research object, and the X-ray tomography method is used to characterize the pore structure and extract structural parameters. Based on the actual pore morphology of the material, the pores in the representative elementary volume (REV) are reasonably assumed to be cubic. Additionally, considering the contact thermal resistance of fibers and the randomness of pore distribution, the curved pattern of heat conduction pathway with the ever-changing diameter is reasonably simplified into a series-parallel form of the curved heat chain with the same diameter. On this basis, the fractal models of effective thermal conductivity are established in horizontal and vertical directions. Finally, a modified formula for the effective thermal conductivity calculation of fiber thermal insulation materials is proposed, taking into account the influence of fiber orientation on the material thermal conductivity. It was shown that the relative deviation between the calculated correction value and the experimental value of the effective thermal conductivity is all less than 16.13%. • The tomography method is used to reconstruct the pore structure of materials. • The 3-D structural parameters of the material are accurately extracted. • The actual curved heat conduction path with ever-changing diameter is considered. • The pores in representative elementary volume are reasonably assumed to be cubic. • The modified formula for calculating effective thermal conductivity is proposed. [ABSTRACT FROM AUTHOR]

• CP-Ti foams with predictable porous architecture were produced using PADS and the space holder method. • The space holder was removed in the sintering reactor using heat. • The foams produced using PADS exhibited higher porosity. • PADS was able to reduce dramatically foams shrinkage in comparison to conventional sintering. • Foams exhibited elastic modulus in the range of cortical and trabecular bones. High porosity titanium foams are used to replace bone structures with low elastic modulus due to their ability to avoid the phenomenon of stress shielding. Producing foams with porosity levels above 70 % in volume using space holders is challenging because the component can collapse or lose shape during processing. In this study, commercially pure Ti powder was mixed with 50, 70, and 80 vol% potassium chloride (KCl) as space holder, cold-compacted, and sintered in a plasma-assisted reactor to obtain high porosity foams. Plasma-assisted technique was used to remove KCl using heat in the sintering reactor. The porous amount of the foams was measured using Archimedes principle and studied through X-ray microcomputed tomography, and the elastic modulus of the foams was measured using ultrasonic wave transmission. The present study showed that the space holder method and plasma sintering can produce CP-Ti foams with predictable porous architecture, reduced shrinkage, and increased porosity than conventional sintering. [ABSTRACT FROM AUTHOR]

Cemented paste backfill (CPB) is used as a support and filler material in underground mines. In underground conditions, before mine closure and flooding, surface and groundwaters with variable quality are in contact with CPB material, which may result in the leaching of harmful substances from the CPB. In this study, we used actual mine water from a gold mine to flush CPB in a laboratory test to simulate underground conditions and the environmental influence of CPB on groundwaters more realistically than before. Different CPB materials were treated with mine water in columns for nine months. The columns were drained and filled with new mine water batches four times during the experiment to simulate intermittent flushing underground. The dissolved elemental content, major cations, pH and oxidation-reduction potential (ORP) of the waters were measured, and the chemical results were analysed by performing geochemical modelling with the widely used geochemical code PHREEQC. X-ray tomography was also used to examine the internal structure of the CPB specimens. The results demonstrated that calcium and sulphate present in CPB parent materials leached into the mine water, which might cause a deterioration of CPB. In contrast, the concentrations of dissolved As, Sb and Ni decreased in the mine water when it was in contact with CPB materials. However, arsenic started to be re-released from the materials at the end of the nine-month experimental period. The geochemical modelling suggests that the removal of metals/metalloids from the mine water was driven by the surface complexation reactions on originally present and/or freshly precipitated metal (hydr)oxide minerals. A longer and modified testing period is needed to thoroughly examine the conditions under which these adsorbed elements start to release over time. • Column tests to study the interaction between mine water and cemented paste backfill. • Removal of dissolved As, Sb and Ni from mine water during experiments. • Ca, SO 4 2− and Mo were released from CPB materials to mine water. • Metal(loid)s removal mainly resulted from surface complexation reactions. • High release of Ca might deteriorate the internal structure of CPB. [ABSTRACT FROM AUTHOR]

• A detailed examination of flow morphology and heat transfer during steam condensation in a single inclined condenser tube was performed for pressures up to 65 bar and steam qualities at inlet down to 2.8 %. • Test experiments were carried out at five pressure stages up to 65 bar and for different inlet steam qualities. • The flow patterns were investigated using two advanced measurement techniques namely X-ray computed tomography and X-ray radiography. • The wall heat flux distribution and integral condensation rate were measured. • The interrelation between flow morphologies and wall heat flux were investigated. We report on an experimental study of high-pressure (up to 65 bar) steam condensation heat transfer in a slightly inclined tube at the thermal–hydraulic test facility COSMEA. The study is part of an extended experimental program on this topic and focused this time on heat transfer and two-phase flow at low inlet steam qualities (down to 2.8 %). We determined condensation rates respectively total heat transfer, wall heat flux distribution and flow morphology using X-ray imaging and local temperature measurements. [ABSTRACT FROM AUTHOR]

The prediction of the pressure drop of packed beds requires an accurate estimation of the packed-bed porosity as its error propagation multiplies the occurring errors by a factor of about four. For a better understanding of the packed bed's local porosity characteristics, a comprehensive x-ray tomography study was performed investigating and correlating the void structure of packed beds made of smooth, mono-sized spheres in cylindrical confining walls having tube-to-particle diameter ratios λ = 3.0 to 9.0 reinforced by numerically generated packed beds of λ = 1.1 to 9.0. An in-depth analysis of the obtained oscillating void profiles is performed, discussing the locations and heights of porosity extrema. Most importantly, a significant and in parts surprising extrema formation in the tube's center is described, especially present for λ < 6, which is assumed to have a predominant effect on the packed bed's pressure drop. Image 1 • X-ray computed tomography scans of ideal sphere packings in slender packed beds. • Comprehensive extrapolation of experimental results by numerical simulations. • Detailed structural investigation of random packed beds of spheres at λ < 10. • Validation of two numerical packing generation procedures. [ABSTRACT FROM AUTHOR]

The present study employs in situ X-ray microtomography to characterize the impact of grain size on void nucleation, growth and linkage during tensile loading of magnesium alloy AZ31. It was found that the tensile strain to failure increased almost threefold when the grain size was reduced from 60 to 3 μm. Grain refinement led to reduced twin formation and reduced void growth rates but did not impact markedly on the relationship between strain and the detected void number density. Because the finer grained samples experienced higher strains to failure, greater void number densities were thus detected at failure in these samples. The void volume fraction at failure remained constant despite changing grain size, within error. Final failure occurs via a shear localization and there appears to be a role of void formation in triggering the final shear instability. We thus favour ascribing failure to a void-sheeting type mechanism. Failure is seen to follow rapidly after a critical void volume fraction is attained and this is broadly consistent with predictions made via the application of a simple McClintock model. The higher strains to failure in the present fine-grained samples are thus ascribed chiefly to the lower rates of void growth. The suppression of void growth by grain refinement seen here may explain why finer grain magnesium alloys often display higher tensile ductility. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The objective of this work is to link microstructure features of foamed gypsum (lightweight gypsum board core material) and its compressive properties. Several samples of foamed gypsum with different microstructures were manufactured and characterized by X-ray tomography and 3D image processing. Spherical indentation tests results show that for a similar density, the size distribution of the macropores and the distribution of the three levels of porosity has only a very small influence on the mechanical properties. In contrast, the density and homogeneity of spatial distribution of macropores has a much stronger impact on hardness. [ABSTRACT FROM AUTHOR]

3D ink-extrusion of powders followed by sintering is an emerging alternative to beam-based additive manufacturing, capable of creating 3D metallic objects from 1D-extruded microfilaments. Here, in situ synchrotron X-ray diffraction and tomography are combined to study the phase evolution, alloy formation and sinter-densification of Fe-20Ni-5Mo (at.%) microfilaments. The filaments are <200 µm in diameter and are extruded from inks containing a blend of Fe 2 O 3 +NiO+MoO 3 µm-sized oxide particles. Blended oxide inks show rapid reduction and homogenization during heating to 1373 K in H 2 accompanied by fast densification and interdiffusion. The resulting homogenous Fe-20Ni and Fe-20Ni-5Mo alloys reach near-full density within minutes at 1373 K. When using Ar-5%H 2 , co-reduction and interdiffusion are slower and the sequence of reduction is changed. During H 2 co-reduction, Fe 2 O 3 and NiO show synergistic effects. The onset temperature of reduction is mutually reduced and the conversion rates to Fe 3 O 4 and Ni are increased. Fe-20Ni-5Mo microfilaments printed with coarser, elemental powder (~3 µm) show slower sintering and compositional homogenization as compared to inks of blended oxide, as the coarser metal particles provide lower surface/volume ratio and higher diffusion distances. Using micron-size oxide powders (rather than coarser metallic particles) accelerates kinetics of reduction, sintering and interdiffusion which reduces costs and energy in 3D ink-printing, improves filament surface quality, but doubles the extent of shrinkage. Image, graphical abstract [ABSTRACT FROM AUTHOR]

A novel particle-based model is proposed to generate synthetic yet representative 3D microstructures of typical SOC electrodes. The model steps can be related to the real electrode manufacturing routes, classically via powders processing, making it a practical tool for electrodes design optimization. The representativeness of the synthetic microstructures is checked on several two-phase (LSCF, LSC) and three-phase (Ni-YSZ) electrodes reconstructed by synchrotron X-ray and FIB-SEM tomography. The validation shows a very good agreement between the real and synthetic media in terms of metric, topological and physical properties. Furthermore, the model is adapted to simulate the microstructure of a typical Ni-YSZ current collecting layer by taking into account a bimodal pore-size-distribution. In this objective, the macro-pores resulting from the burning-off of specific pore-formers are morphologically separated in the reconstruction from the micro-porosity network. Finally, the geometrical features of the macro-pores are meticulously characterized and successfully emulated by using parametric ellipsoids. Morphological separation of the macropores resulting from the burning-off of specific pore-formers from the micro-porosity network coming from partial powders sintering and the NiO reduction in the X-ray tomographic reconstruction of the electrode substrate. This microstructure is thoroughly characterized and successfully simulated by the proposed particle-based model. Unlabelled Image • Novel particle-based model for Solid Oxide Cell electrodes microstructure. • Synthetic microstructures for Ni-YSZ, LSCF and LSC functional layers. • Synthetic microstructure for Ni-YSZ substrate with a bimodal pore size distribution. • Model validated on large synchrotron X-ray holotomography 3D reconstructions. • Quantification of the different porosity length-scales within the substrate. [ABSTRACT FROM AUTHOR]

Cold sintering is a promising route towards the manufacturing of dense ceramics at mild processing conditions, but our poor understanding of the process has prevented the wider spread of this attractive densification approach. Using nanovaterite powders with well-defined multiscale morphology, we perform in-situ X-Ray tomography on compacts subjected to controlled mechanical load and quantify the multiscale deformation processes responsible for the water-assisted cold sintering of this powder with the help of instrumented indentation experiments at the micro- and nano-scale. Our results reveal the crucial effect of water in promoting the macroscopic densification process and highlight the dominant role of the nanoparticle network inside agglomerates in controlling the cold sintering of compacts at high mechanical loads. By providing new insights into the deformation processes responsible for the densification effect, this study can potentially guide the discovery of novel chemical compositions and particle morphologies that can be more easily densified through room-temperature cold sintering with water. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Preservation bias may significantly impact the application of detrital zircon geochronology in reconstructing Earth surface processes. Here we compare detrital zircons from the actively eroding Murchison River channel in Western Australia with Ordovician fluvial sediments that have drained similar source rocks along the western margin of the West Australian Craton. In addition to standard analysis of detrital zircon age spectra we apply multivariate statistics to test the relation between 3-D grain shape, U-content and U–Pb ages, with the objective to quantify differences between both sample groups and track preservation along the transport pathway of the Murchison River. Our results show that zircon grains in modern river sands display an upstream trend toward larger surface areas, volume equivalent diameters and grain widths, as well as toward higher U-contents and lower apparent grain densities. 3-D grain shape, size and age spectra of Murchison River zircons evolve consistently downstream, but even at the river outlet remain distinct from the Ordovician samples, as a less mature representation of source. We interpret Ordovician river zircons to represent a significantly depleted subset from which up to 22% of the zircon population may have been lost compared to the actively transported detrital load. This discrepancy between the characteristics of detrital zircons in modern active rivers and ancient fluvial Ordovician sandstones demonstrates a bias that could be relevant for other source-sink detrital transport systems throughout Earth history. Image 1 • Comparison between detrital zircons from modern river sands and Ordovician fluvial sediments. • Provenance bias quantified by 3-D grain shape, composition and U–Pb age of detrital zircons. • Up to 22% of the zircon population in ancient river sediments may have been lost compared to their modern counterparts. [ABSTRACT FROM AUTHOR]

Ceramic oxide green pellets for nuclear fuel or targets are manufactured by powder processes producing detrimental fines. Porous brittle microspheres offer an interesting alternative, providing that their fracture behavior is well controlled during pressing. Here we investigate, using experimental characterization and numerical simulations, the effect of porosity and internal defects on the strength of porous microspheres. We show that although the residual porosity is the main parameter affecting their strength, the shape and location of defects also play a role. Real defects characterized by X-ray tomography are reproduced with discrete element simulations, providing new insights on their fracture behavior. We also investigate the departure from monosized microspheres by simulating the fracture behavior of two microspheres of different sizes, and show that it is the minimum radius that allows for a consistent strength normalization. This study offers a method for anticipating agglomerate strength that can be generalized for any ceramic systems. [ABSTRACT FROM AUTHOR]

• X-ray absorption tomography is applied to ancient Egyptian papyri. • X-ray imaging and volume rendering is used to identify type of folding on ancient papyri. • An unfolding algorithm is applied to ancient papyri with orthogonal folding lines. • A hidden text was identified in an Egyptian papyrus after virtual unfolding/unrolling. The historical importance of ancient manuscripts is unique since they provide information about the heritage of ancient cultures. Often texts are hidden in rolled or folded documents. Due to recent improvements in sensitivity and resolution, spectacular disclosures of rolled hidden texts were possible by X-ray tomography. However, revealing text on folded manuscripts is even more challenging. Manual unfolding is often too risky in view of the fragile condition of fragments, as it can lead to the total loss of the document. X-ray tomography allows for virtual unfolding and enables non-destructive access to hidden texts. We have recently demonstrated the procedure and tested unfolding algorithms on a mockup sample. Here, we present results on unfolding ancient papyrus packages from the papyrus collection of the Musée du Louvre, among them objects folded along approximately orthogonal folding lines. In one of the packages, the first identification of a word was achieved, the Coptic word for "Lord". [ABSTRACT FROM AUTHOR]

• An unprecedented multi-modal 3D image-based simulation was established to fully capture the actual distributions of stress and hydrogen. • Quasi-cleavage crack propagated in the region where the interfacial cohesive energy of precipitate was reduced by hydrogen. • A combination of hydrogen and applied stress led to nano-crack initiation and associated hydrogen embrittlement in Al-Zn-Mg alloy. • Dynamic hydrogen partitioning to precipitate dominates hydrogen embrittlement in Al-Zn-Mg alloy. Hydrogen can strongly embrittle aluminum alloys by accumulating at precipitate interface and triggering transgranular cracking, due to stress-driven hydrogen diffusion towards crack tip and grain boundaries. However, although mechanical features near crack tip and grain boundaries, and hydrogen diffusion/trapping processes have been extensively studied separately, very few quantitative information regarding the local interactions between hydrogen distribution and stress fields with full spatial complexity has been revealed. The present study attempts to fill this gap, by using a multi-modal three-dimensional image-based simulation that combines a crystal plasticity finite element method with hydrogen diffusion analysis, to fully capture the actual stress distribution and its effect on hydrogen distribution, and more importantly on cracking probability, near a real propagating hydrogen-induced crack. Stress-diffusion-trapping coupled simulations indicate the intergranular crack transitioned to a quasi-cleavage crack in the region where the interfacial cohesive energy of semi-coherent interface of the MgZn 2 precipitate was reduced by hydrogen accumulation near the crack tip. The multi-modal three-dimensional image-based simulation used in the present study successfully bridged nanoscopic debonding and macroscopic hydrogen embrittlement fracture behavior. [Display omitted] [ABSTRACT FROM AUTHOR]

Lime-cement columns are a common form of ground improvement used in the Nordic countries to improve the engineering properties of soft soils. The strength and stiffness of lime-cement mixed clay, however, are heterogeneous. Hence, the characterisation of the extent of variability of strength and stiffness is essential to optimise the performance of lime-cement columns. This paper presents an integrated approach to characterise the variability in strength and stiffness of samples from 1 year old lime-cement columns in natural sensitive clay, from the Centralen project site in Gothenburg, Sweden. A novel image-based method is proposed to characterise the spatial variability at the laboratory scale, using a stereoscopic digital image correlation (DIC) system in addition to X-ray Computed Tomography (XCT) scans. Data from column penetration tests (FKPS) and reverse column penetration tests (FOPS) on the lime-cement columns at the excavation site were used to estimate the spatial variability at the field scale. The key finding of this work is that different magnitudes of scales of fluctuations exist for the lime-cement mixed clay under laboratory scale and field scale testing. The results serve to highlight the ever-present problem of inherent variability in lime-cement mixed soils and challenges to accurately characterise this variability. Thus, further work is required to relate scale of fluctuation of strength to that of stiffness, and to link scale of fluctuation at laboratory scale with that at field scale. • The strength and stiffness of lime-cement columns are highly variable in magnitude and spatial distribution. • Different magnitudes of scales of fluctuations (SOF) exist at laboratory and field scale. • SOF of lime-cement columns estimated from field sounding data and image-based methods. [ABSTRACT FROM AUTHOR]

Defects in composite materials, such as voids, significantly impact their long-term performance and should be carefully considered in the design process of engineering structures. This study investigates the effects of high void content on the impact and post-impact properties of pure Flax/Epoxy (FE) composite laminates. Three main configurations, namely cross-ply (CFE), angle-ply FE (AFE), and quasi-isotropic FE (QFE), are examined using drop-weight impact and three-point bending tests. The results reveal distinct behavior among the configurations. The drop-weight impact test results show that the AFE configuration exhibits 3.5 % and 6.45 % higher impact resistance compared to CFE and QFE, respectively. to the increase of the impact energy to 15 J amplifies the differences to 9.31 % and 19.11 %. Also, post-impact flexion tests demonstrate a significant decline in flax composite resistance by 14 % for CFE, 26 % for QFE, and AFE. Furthermore, the overall impact and flexural properties of the FE composites are not significantly affected by the void content. However, it has a major impact on the damage mechanism that is ispected visually and through X-ray tomography, emphasizing the importance of considering the void content in the design and analysis of such flax composites. The proposed numerical model to predict the onset of damage and damage evolution in these composite materials under low velocity impact show a good greement with the experimental results. [ABSTRACT FROM AUTHOR]

The high temperature strengthening mechanisms in Al-Cu-Fe aluminium alloy was analysed basis on a comprehensive microstructural study of the as-cast alloy and mechanical testing results. An approach which extracts the specific contribution of solid solution atoms, precipitates, and Fe-rich particles to the creep strengthening was utilized. Additionally, the Shear Lag model, was employed to account for the contribution to strengthening of the Fe-rich intermetallic particles through a load transfer mechanism. For this study, an as-cast Al-Cu alloy, which does not contain Fe impurities, has been also used for comparative purposes. The findings suggest that the large and 3D interconnected Fe-rich phase particles (Al 6 (MnFe) and α-Fe) generate the main strengthening effect at high temperature through a load transfer mechanism, whereas the contribution of the nanometric Al 2 CuMg precipitates were very limited. • Al-Cu-Fe alloy shows higher elevated temperature mechanical properties. • The 3D morphology of intermetallic particles after test is reconstructed by synchrotron X-ray tomography. • The fine precipitates and Fe-rich particles contribute to the improve of high temperature properties. • Fe-rich phases generate a high load transfer effect in Al-Cu-Fe alloy. [ABSTRACT FROM AUTHOR]

• Bed particle layer growth on quartz is faster at convex regions of the particle. • Convexes show thick inner and outer layer, concaves mainly show a thin inner layer. • Smooth areas of bed particles have the thickest Ca-rich inner and outer layers. • Crack layers form in concaves with cracks in the inner and a missing outer layer. • Ca-rich protective layers on smooth particles may reduce operational problems. The influence of quartz bed particle surface morphology on the bed particle layer and crack layer formation process in fluidized bed combustion of woody biomass was investigated in this work. Bed material samples were collected at different sampling times from the startup with a fresh bed in industrial scale bubbling fluidized bed (BFB) and circulating fluidized bed (CFB) boilers, both utilizing woody biomass. X-ray microtomography (XMT) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) were employed to characterize bed particle layers and crack layers in the samples. Results showed that there is a noticeable difference between the bed layer characteristics over the so-called "concave" and "convex"-shaped morphologies on the bed particle surface with respect to layer formation. The concave areas are mainly covered with a thin inner layer, whilst the convex display a comparably thick inner layer and an outer layer. In addition, 3D images of the particles revealed that the crack layers mainly originate from concave areas where the particle is less protected by an outer bed particle layer in conjunction with cracks in the inner layer. [ABSTRACT FROM AUTHOR]

This article introduces a novel testing system for investigating rock hydromechanical behavior with neutron and X-ray imaging techniques. The system comprises four subsystems: an axial compression system, a confining pressure system, a fluid flow system, and a triaxial cell. In order to enable imaging with both modalities to track fluid flow and deformation in situ and 3D, the cell was designed to have sufficient transparency to X-rays and neutrons. The system's capabilities are demonstrated by showing neutron and X-ray tomography data of Idaho Gray sandstone samples during in situ coupled flow-triaxial tests. Quasi-single-phase flow analysis was enabled by directly visualizing the fluid front advance via neutron tomography by exchanging light water (H 2 O) and heavy water (D 2 O). Digital Volume Correlation (DVC) could be performed on both the X-ray and neutron tomography images to quantify the mechanical strain field evolution in the samples, which can be compared to the evolution of the fluid flow fields. In addition, the cell and a sample of Idaho Gray sandstone were imaged in a laboratory X-ray tomography machine, generating 3D reconstructed volumes with grain-scale resolution. Improvements are proposed for future experiments to obtain grain-scale resolution images during coupled flow-triaxial tests using neutron and X-ray beams simultaneously and conducting in situ experiments on laboratory tomographs. • A novel system for conducting flow and triaxial tests with neutron and X-ray imaging. • The triaxial cell is sufficiently transparent to both X-rays and neutrons. • 3D flow path tracking can be achieved using high-speed neutron tomography. • Digital volume correlation can be performed from X-rays and neutron images. [ABSTRACT FROM AUTHOR]

There is an ever increasing demand for higher power and energy in EVs and the use of anodes with a percentage of silicon (Si) is becoming more prevalent to meet those demands. This article describes the results of a systematic study on electrochemical performance and the impact of mechanical changes within two types of batteries of commercial relevance that are nominally identical except their anode chemistry. We analyse 32 cells with a composite anode comprising graphite and a silicon-based component, and 30 cells with conventional graphite anodes and reveal through X-ray computed tomography that jelly roll deformations nucleate as a result of the swelling of the anode layers towards the centre of the cell. Furthermore, although Si causes large mechanical changes in the architecture of the jelly roll, with respect to the SOH window relevant for EVs, the presence of a small percentage of Si does not have a highly detrimental impact on the cycling performance of the cells. In fact, with respect to cell degradation, it appears that commercial cells have not yet reached the limit of Si loading in composite anodes, and there is room for improvement in cell capacities to meet the increasing demands on EVs. • A systematic comparison of cell architectures with and without silicon is presented. • X-ray CT reveals substantial changes to the cell architecture with silicon based additives. • In spite of this, it appears that cells have not yet reached the limit of Si loading. [ABSTRACT FROM AUTHOR]

Previous studies show that the total volume of fractures increases non-linearly during loading as rocks approach failure in triaxial compression at stress and temperature conditions representative of the upper crust. However, the factors that control the critical volume of fractures or the critical spatial organization of the fracture network that trigger macroscopic failure remain unclear. To identify the fracture characteristics that determine the timing of macroscopic failure and localization of the fracture networks, we analyze data from six X-ray tomography experiments on Westerly granite with varying confining stress, fluid pressure, and amounts of preexisting damage. We develop machine learning models to predict 1) the timing of failure, 2) the localization of the fracture networks as measured with the Gini coefficient of the fracture volume, and 3) the change in localization from one differential stress step to the next. When the models only have access to individual fracture characteristics, the fracture length produces the best predictions of the distance to failure. When the models have access to the fracture length and sets of other characteristics, the fracture volume, aperture, and distance between fractures produce the best predictions of the distance to failure. The characteristics that describe the time or loading in the experiment, the axial strain and differential stress, produce some of the best predictions of the Gini coefficient. The results are generally consistent among the different experiments, suggesting that the fracture characteristics that determine the timing of macroscopic failure, and the localization of the fracture network, are independent of the range of confining stress, fluid pressure, and amount of preexisting damage tested here. Our results are consistent with the idea that monitoring the spatial distribution of deformation and changes in the seismic wave properties indicative of fracture growth may improve forecasting efforts of failure in the crust. • Predicting localization, delocalization, and the timing of catastrophic failure. • The fracture length, volume, aperture, and clustering predict the timing of failure. • The macroscopic strain and stress predict fracture localization. • The models struggle to predict delocalization. [ABSTRACT FROM AUTHOR]

Stress corrosion cracking (SCC) behaviors induced by the combination of external and internal hydrogen (H) in an Al-Zn-Mg-Cu alloy were systematically investigated via in-situ 3D characterization techniques. SCC of the Al-Zn-Mg-Cu alloy could initiate and propagate in the potential crack region where the H concentration exceeded a critical value, in which the nanoscopic H-induced decohesion of η -MgZn 2 precipitates resulted in macroscopic cracking. External H that penetrated the alloy from the environment played a crucial role during the SCC of the Al-Zn-Mg-Cu alloy by generating gradient-distributed H-affected zones near the crack tips, which made Al alloys in water environment more sensitive to SCC. Additionally, the pre-existing internal H was driven toward the crack tips during plastic deformation. It was involved in the SCC and made contributions to both the cracks initiation and propagation. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Real and artificially generated material representations i.e. texture volumes. • X-ray microscopy (XRM) measurements of lithium aluminate slag. • Texture inheritance of spherical particles in the particle replacement method (PRM). • The model is suitable for breakage in discrete element method (DEM) simulations. • Liberation distributions for a magnetite-iron ore and lithium aluminate slag. Various models have been developed in recent years to simulate particle breakage in discrete element method (DEM) simulations. However, texture inheritance of fragments is only available for certain complex particle shapes or bonded particle models, significantly increasing the computation time. We propose a spherical particle model coupled with a particle replacement method (PRM) scheme, which incorporates texture inheritance through an intermediate mapping step. In this way, the model benefits from the computational advantages of spherical particles without losing texture information during the breakage process. The model is evaluated by applying it to artificially generated particles incorporating texture information from a lithium-containing slag measured by X-ray microscopy (XRM) and an artificially generated magnetite iron ore. Comparisons of the liberation distributions with other models in the literature match with minor deviations. In addition, the liberation distributions calculated using the model are consistent with randomly sampled particles. [ABSTRACT FROM AUTHOR]

• Simultaneous X-ray diffraction and X-ray tomography combination allow to correlate the cement phase contents and pore microstructures. • CSH amount in dry samples do not change when irradiated, not modifying the amount of gel pores. • Sodium sulfate solution increases the fractality of macropores in samples when compared in water and dry conditions. Radioactive waste disposal, considered a major technical problem, has as one of the solutions, the construction of repositories that will be exposed to a range of environmental conditions in a timescale which involve thousands of years. Cement-based materials, used in the repositories, have a complex porous structure that changes over time and their durability strongly correlates to the transport of water and ions throughout the pore structure. In this study, the influence of the repository's environment was simulated using two different solution conditions: Water and Na 2 SO 4 at different gamma irradiated condition. Two X-Ray techniques were performed simultaneously: (i) diffraction to characterize the phases contents on cement mortar samples; (ii) tomography to investigate the differences between the pore structure and pores volume. The combination's advantage of the X-Ray techniques shows their potential application to determine the relation amongst the phases and the pores structures, to demonstrate how the environment and the irradiation modify the structure of mortar. [ABSTRACT FROM AUTHOR]

Compression of snow at low strain rates governs the natural densification of snow and firn on Earth. Different deformation mechanisms (e.g., grain boundary sliding and dislocation creep) are widely employed in models and are mainly believed to change depending on relative density or snow type. To explore this picture, we conducted compression experiments with a nominally constant strain rate ɛ ̇ ≈ 1 0 − 6 s − 1 and systematically varied snow type, density, and specific surface area. We used a micro-compression stage to enable X-ray micro-tomography imaging and microstructure characterization before and after the experiment. Using repeated load-relaxation cycles, we eliminate changes in the microstructure that occur during the first loading, allowing us to probe the viscoplastic behavior of the intact ice matrix. To evaluate the effective mechanical behavior of snow, we derived an implicit, analytical solution of a non-linear scalar model that characterizes loading and relaxation in terms of the stress exponent n in Glen's law. Our results evidence a sharp transition of n as a function of the geometrical grain size, and rule out that this transition is caused by density or snow type. The derived values of n ≈ 1. 9 for small grains to n ≈ 4. 4 for large grains are consistent with a transition from grain boundary sliding to dislocation creep at a transition grain size of around 0.5-0.6 mm. Our results shed new light on the old discussion about deformation mechanisms in snow and firn. [Display omitted] • Consecutive loading-relaxation experiments complemented by micro-CT were employed. • Experiments allow probing the viscoplastic behavior of the intact ice matrix in snow. • We evaluated experiments to estimate Glen's law stress exponent and time scales. • The geometrical grain size drives transition in Glen's law exponent n for snow. • n transits from n ≈ 1. 9 (fine grains) to n ≈ 4. 4 (coarse grains) in snow. • This transition is interpreted as a transition from GBS (n ≈ 1. 9) to DC (n ≈ 4. 4). [ABSTRACT FROM AUTHOR]