Open Access

Show Abstract ▼

Abstract: This study usedhigh-speed synchrotron X-ray tomography to image the growth of Al2Cu intermetallic compoundsin 4D (3D plus time) during solidification of Al-45wt%Cu alloy. Two categories of growth patterns (basic units and dendrites) are identified. Basic unitsare elongated rods whose cross-section areL, U orhollow-rectangularshapes. The transition from L pattern to U and finally to hollow-rectangularshaped morphologywas observed. Faceted dendritic patterns include equiaxed prism and columnar dendrites. Self-repeated layer-by-layer stacking of the basic units (such as L shaped particles) is proposed as a governing mechanism for the growth of Al2Cu faceted dendrites. The growth orientation and morphologies of these patterns are strongly influenced by solidification conditions (temperature gradients, cooling rates and external magnetic fields). Another finding is that when rotating Al-45wt%Cu during upwards directional solidification,under a transverse magnetic field of 0.5T, highly refined and well aligned Al2Cu intermetallic compounds are obtained, much finer than those without the imposition of the magnetic field. This is attributed to a rotational stirring flow that modulates and regulates the temperature and solute distribution.The developed experimental findings provide a physical understanding of the formation of faceted intermetallic compounds during solidification.

Show Abstract ▼

Abstract: Zero carbon energy generation from renewable sources can reduce climate change by mitigating carbon emissions. A major challenge of renewable energy generation is the imbalance between supply and demand. To overcome the energy imbalances, subsurface storage of hydrogen in porous mediais suggested as a large-scale and economic solution, yet its mechanisms are not fully understood. Important unknowns are the effect of the high migration potential of the small and mobile hydrogen molecule and the volume of recoverable hydrogen. We conducted non-steady state, cyclic hydrogen and brine injection experiments at 2-7 MPa and flow rates of 2-80 µl min-1 using water-wet Clashach sandstone cylinders of 4.7 mm diameter and 53-57 mm length (Clashach composition: ~96 wt.% quartz, 2% K-feldspar, 1% calcite, 1% ankerite). Two sets of experiments were performed using our new transparent flow-cell designed for x-ray computed microtomography: 1) Experiments using a laboratory x-ray source (University of Edinburgh) imaged the flow, displacement and capillary trapping of hydrogen by brine as a function of saturation after primary drainage and secondary imbibition. 2) Experiments using synchrotron radiation (Diamond Light Source, I12-JEEP tomography beamline) captured time-resolved hydrogen and brine flow and displacement processes. Pressure and mass flow measurements across the experimental apparatus complemented the microtomography volumes in both sets of experiments. Results from a water-wet rock show that hydrogen behaves as a non-wetting phase and sits in the centre of the pore bodies, while residual brine sits in corners and pore throats. Hydrogen saturation in the pore volume is independent of the injection pressure and increases with increasing hydrogen/brine injection ratio up to ~50% saturation at 100 % hydrogen. Capillary trapping of hydrogen during brine imbibition occurs via snap off and is greatest at higher brine injection pressures, with 10 %, 12% and 21% hydrogen trapped at 2, 5 and 7 MPa, respectively. Higher brine flow rates reduce capillary trapping and increase hydrogen recovery at any given injection pressure. Based on these results, future hydrogen storage operations should inject 100% hydrogen and manage the reservoir pressure to avoid high pressures and minimize capillary trapping of hydrogen during brine reinjection. Ongoing analysis of time-resolved experimental data will provide further insight into the critical pore-scale processes that ultimately influence the potential for geological hydrogen storage and recovery.

Show Abstract ▼

Abstract: A fundamental clarification of the electro-chemo-mechanical coupling at the solid–solid electrode|electrolyte interface in all-solid-state batteries (ASSBs) is of crucial significance but has proven challenging. Herein, (synchrotron) X-ray tomography, electrochemical impedance spectroscopy (EIS), time-of-flight secondary-ion mass spectrometry (TOF-SIMS), and finite element analysis (FEA) modeling are jointly used to decouple the electro-chemo-mechanical coupling in Li10SnP2S12-based ASSBs. Non-destructive (synchrotron) X-ray tomography results visually disclose unexpected mechanical deformation of the solid electrolyte and electrode as well as an unanticipated evolving behavior of the (electro)chemically generated interphase. The EIS and TOF-SIMS probing results provide additional information that links the interphase/electrode properties to the overall battery performance. The modeling results complete the picture by providing the detailed distribution of the mechanical stress/strain and the potential/ionic flux within the electrolyte. Collectively, these results suggest that 1) the interfacial volume changes induced by the (electro)chemical reactions can trigger the mechanical deformation of the solid electrode and electrolyte; 2) the overall electrochemical process can accelerate the interfacial chemical reactions; 3) the reconfigured interfaces in turn influence the electric potential distribution as well as charge transportation within the SE. These fundamental discoveries that remain unreported until now significantly improve the understanding of the complicated electro-chemo-mechanical couplings in ASSBs.

Show Abstract ▼

Abstract: A critical initial phase for any beamline involves detailed characterization and commissioning tests. The development of high-brightness synchrotron laboratories around the world has provided users with X-ray beams with ever smaller dimensions and ever increasing fluxes. As a result, the dose that is delivered to the samples becomes an even greater concern when the objects of study are materials of biological interest. Theoretically, for high densities of X-ray fluxes, there is a relationship between the dose (or dose rate) and induced structural damage. Dosimetric estimates are the first step in minimizing the risk of radiation damage. This work aims to contribute to the topic of dosimetry in synchrotron beams, estimating the dose rate in water from the simulation of the synchrotron X-ray spectrum for three different generations of storage rings. Direct measurement of the incident X-ray spectrum is very difficult as the differential photon flux rate is orders of magnitude greater than the capabilities of conventional detector materials and pulse height analysis hardware. Alternatively, the spectrum was estimated from a theoretical model using the SPECTRA version 11.0 program. We focus on quantities related to the X-ray beam: flux (flux density, integrated flux, etc.), beam quality, power, which are related to basic dosimetric physical quantities such as fluence, air kerma and absorbed dose by soft tissue. The proposed methodology was tested using the experimental parameters of three synchrotron sources of different generations, UVX, Elettra and Sirius, in order to estimate the dose in a biological sample. The same methodology was applied in a real experiment in which the morphology of the tadpole Thoropa miliaris was studied using the microtomography technique in the SYRMEP and IMX beamlines. The results obtained show the need to optimize experiments with biological samples in order to reduce the dose delivered to the sample while maintaining the commitment to the quality of the generated image.

Show Abstract ▼

Abstract: Microdefects in the rust layer of conventional steel and weathering steel were investigated by synchrotron X-ray micro tomography to understand the effect of defects on corrosion resistance. The rust layer of the weathering steel contained fewer and smaller defects than that of the conventional steel. A good correlation existed between the volume of defects and ion permeation of the rust layer obtained by EIS. In comparison with the conventional steel, the tomography results indicated that a protective layer formed on the weathering steel.