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Segregation of the solidification structure of an immiscible alloy is related to the convection induced by the density differences of the components under gravity during solidification. Here, the solidification of the Al–Bi alloy in both opposing and parallel directions to the gravity force was investigated in situ using radiography and optical flow techniques. A quantitative analysis was performed on the flow, solute, and constitutional undercooling fields at the interface. During upward solidification, a flat solute-enriched layer was observed, with the melt flowing toward the center from both sides of the interface. During downward solidification, the solute-enriched layer was deformed, and solute plumes were observed, with the melt flowing toward the sides from the center of the interface. A high solute concentration gradient enhances the local flow and solute transport. The elongation of the plumes was attributed not only to the convective diffusion of the solute but also to the dispersion of droplet clusters. The forces acting on the droplets were calculated, and it was found that the resultant force on the droplets increased the area of the solute-enriched layer. Convection within the bulk melt and the motion of the droplets have synergistic effects on the flow pattern and solute distribution. Distinct microstructures were observed in opposite directions of solidification owing to the differences in constitutional undercooling and flow instability. This work offers insights into the quantitative measurement and understanding of the multi-physics fields during the solidification process. [ABSTRACT FROM AUTHOR]

Cuttage is a common plant cultivation method, and the key to its survival is the restoration of water refilling, which remains unclear up to now. We report 3D dynamic imaging of water refilling of cuttage without resorting to any contrast agent. Hydrodynamics of the refilled water flow over time reveals the existence of a unit mass force field with a gradient along the refilling direction, which means that cutting plants also have a gradient force field to drive the recovery of water refilling, as predicted by Cohesion-Tension theory in normal plants. We found that force fields of different functional regions are isolated and independently distributed, which is conducive to ensure the safety of water transmission. At the same time, we also found that there is a so-called "inchworm effect" in the mass force field, which contributes to the force transfer inside the cutting through local force accumulation. Results of this paper demonstrate that the developed method for the measurement of mass force field in-vivo is applicable to help decipher the mechanism of plant water refilling. [ABSTRACT FROM AUTHOR]

Rechargeable magnesium batteries (RMBs), with Cu as positive electrode current collector (CC), typically display a gradual capacity increase with cycling. Whereas the origin of this was suggested in gradual active material electro-activation, the fact that this is prevalent in many positive electrode material systems remains unexplained. Herein, we elucidate the underlying mechanism through a series of multiscale joint operando X-ray characterizations, including operando synchrotron X-ray diffraction and imaging technology. We select a series of manganese oxides as benchmark positive electrodes and find that no magnesium ions are stored within the lattices of these materials, despite an apparent cell capacity increase with cycling. The origin of capacity increase is rooted in the gradual electrochemical corrosion of metallic Cu, release of Cu(I, II) species in electrolyte, and their subsequent redox activity, resulting in apparent electrode capacity gains. Furthermore, the shuttle and redox speciation of Cu ions trigger the irreversible depletion of both the Cu CC (or any other source) and the magnesium metal, ultimately leading to cell failure. Our work suggests the need to reconsider the appropriateness of using Cu as a positive electrode CC for RMBs., (© 2024 Wiley‐VCH GmbH.)