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Abstract: Investigating the textural properties and 3D geometry of the connected pore network in volcanic products provides insight into magma ascent processes, due to their influence on magma permeability, outgassing efficiency and explosivity. Here, we used X-ray computed microtomography to investigate vesicle textures in tephra from the 2021 Tajogaite eruption (La Palma, Spain) and the relationship between these pore network parameters and eruptive style. We report a 3D dataset of pore network parameters for lapilli clasts collected throughout the eruption, associated with different eruptive styles (ash-rich jets, lava fountains, Strombolian activity). In clasts from Strombolian activity, the lower vesicle number density (VND) and tortuosity factor (m) suggests that there are fewer vesicles and that the channels which connect them are less tortuous than in clasts from fountain and ash-rich jet activity, favouring a lower degree of gas–melt coupling and thus, more efficient outgassing. Instead, for clasts of lava fountain and ash-rich jet activity, the higher VND and m suggest a higher number of vesicles connected by more tortuous channels, promoting some degree of gas–melt coupling and thus, less efficient outgassing. However, in clasts from ash-rich jets, the presence of narrower channels, as suggested by the lower throat-pore size ratio, favours a greater degree of gas–melt coupling with respect to fountain activity, leading to magma fragmentation. This work highlights the importance of textural and pore network analyses in understanding eruption dynamics, and provides a case study for investigating the interplay between pore network parameters, magma permeability and ascent dynamics for low-viscosity magmas.

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Abstract: The strength-ductility trade-off in additively manufactured (AM) β Ti alloys remains a significant challenge. In this study, we employed a cost-effective in-situ alloying laser powder bed fusion approach with optimized processing parameters to fabricate a nearly fully dense, chemically homogeneous β Ti-12Mo alloy. We then examined how solution-treatment duration influences the tensile behavior of the AM Ti-12Mo alloy. The optimally solution-treated alloys exhibited high tensile yield strength (725–741 MPa) and commendable ductility (22–36 %) along both the 0° and 90° orientations relative to the build direction. Focusing on the underlying deformation mechanisms perpendicular to the build direction, we report a uniform elongation of 17.9 % and a pronounced strain hardening rate (∼2300 MPa at 4 %), which we elucidate via in-situ high-energy synchrotron X-ray diffraction and microstructural characterization. The high yield strength is primarily attributed to the presence of Mo-lean embryonic athermal ω nanoparticles. During plastic deformation, both twinning and phase transformation contribute to the high strain hardening rate. At the early stage (strain < 1.9 %), deformation is dominated by {332}< 113 >β twinning, whereas at later stages, the deformation-induced α'' phase becomes significant. The volume fraction of α'' phase increases with strain, supporting the continuous hardening. Notably, irrational {112}< 751 >β, secondary {112}< 111 >β, and {130}< 310 >α'' nano-twins confine the primary structures to nanograins and sustain strain hardening. This study sheds light on designing high-performance β Ti-12Mo alloy via AM followed by heat treatment.

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Abstract: This study aims to understand the interplay between strength and ductility in metastable β-Ti alloys based on eutectoid and neutral elements. A low-cost ternary Ti-7Cr-4Sn alloy was prepared by furnace cooling from the single β region at the end of the primary processing. Although isothermal ω, a nano-precipitation generally considered to embrittle the material, is present in the obtained ultra-fine microstructure, the material still exhibits a balanced strength and ductility, with a yield stress of 1067 MPa and elongation of about 10%. The obtained tensile properties surpass traditional primary processed Ti-6Al-4V, and are comparable to a range of expensive commercial high-strength aerospace Ti alloys. Multiple microstructural features, including grain boundary α (αGB), short rod shape primary α (αP), isothermal ω (ωiso) and ω assisted secondary α (αs) are characterised within the room temperature microstructure. Microstructural analysis reveals that strong Cr segregation in the β phase and slight partitioning of Sn between the α and β phase strengthens the β phase while also preserving ductility in the alloy. This results in a microstructure dominated by the ductile α phase and sub-micron α grain boundaries. This study also discusses the evolution of these microstructural features during different stages of cooling from β matrix, substantiating a promising alloy design strategy for affordable high-performance new Ti alloys.

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Abstract: Lithium ion batteries are pivotal for clean energy storage and mitigating climate change. In this study, we employ operando synchrotron X-ray computed tomography to investigate the dynamic evolution of battery cathode microstructure. We focus on tracking changes in porosity and pore size distribution at the microscale and cathode thickness at the macroscale during the lithiation and delithiation processes within a commercially configured battery. Image quality was enhanced using both conventional image processing methods and a Super-Resolution Convolutional Neural Network (SRCNN) model. Our findings revealed a slight increase in the cathode solid volume fraction and specific surface area as the battery transitioned from its pristine state to fully lithiated, followed by a reduction during delithiation. This behavior was attributed to the expansion of the cathode material and phase transitions during lithiation, which split larger pores into smaller ones, as evidenced by the increase in surface area. Cathode thickness also exhibited expansion during lithiation and contraction during delithiation. These results offer valuable insights into the structural changes that contribute to battery aging, helping researchers better understand how these different parameters change over time. This understanding is crucial for designing more durable and sustainable batteries in the future, both in terms of specific design and material selection, to enhance resistance during charge and discharge cycles to improve performance and longevity.

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Abstract: Hydrogen (H2) storage in porous geological formations offers a promising means to balance supply and demand in the renewable energy sector, supporting the energy transition. Important unknowns to this technology include the H2 fluid flow dynamics through the porous medium which affect H2 injectivity and recovery. We used time-resolved X-ray computed microtomography to image real-time unsteady and steady state injections of H2 and brine (2 M KI) into a Clashach sandstone core at 5 MPa and ambient temperature. In steady state injections, H2 entered the brine-saturated rock within seconds, dispersing over several discrete pores. Over time, some H2 ganglia connected, disconnected and then reconnected from each other (intermittent flow), indicating that the current presumption of a constant connected flow pathway during multiphase fluid flow is an oversimplification. Pressure oscillations at the sample outlet were characterized as red noise, supporting observations of intermittent pore-filling. At higher H2 fractional flow the H2 saturation in the pore space increased from 20-22 % to 28 %. Average Euler characteristics were generally positive over time at all H2 flow fractions, indicating poorly connected H2 clusters and little control of connectivity on the H2 saturation. In unsteady state injections, H2 displaced brine in sudden pore-filling events termed Haines jumps, which are key to understanding fluid dynamics in porous media. Our results suggest a lower H2 storage capacity in sandstone aquifers with higher injection-induced hydrodynamic flow and suggest a low H2 recovery. For more accurate predictions of H2 storage potential and recovery, geological models should incorporate energy-dissipating processes such as Haines jumps.