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Increasing electrode thickness is gaining more attention as a potential route to increaseenergy densityforLi ionbatteries although the realizable capacity and rate capability are usually limited by Li+ion diffusion during (dis)charge, especially at increased (dis)charge rates. It remains challenging to visualize and quantify the low atomic number Li+chemical stoichiometry distribution inside the electrode within commercially standard battery geometry, e.g.coin cells with stainless steel casings. Here, we map the distribution of Li+chemical stoichiometry in the electrode microstructure inside a working coin cell battery to show the amount of electrode materials contributing to energy storage performance using innovativein situcorrelative full-field X-ray Compton scattering imaging (XCS-I) and X-ray computedtomography(XCT). We design and fabricate an ultra-thick (∼1mm) cathode of LiNi0.8Mn0.1Co0.1O2with a microstructure containing vertically oriented pore arrays using a directional ice templating method. This novel technique paves a new way to map low atomic number elements in 3D structures and study how the microstructure improves Li+iondiffusivityand energy storage performance.

The propagation rate of a fatigue crack in a nodular cast iron, loaded in cyclic tension, has been studied in situ by X-ray computed tomography and digital volume correlation. The semi-elliptical crack initiated from an asymmetric corner notch and evolved to a semi-circular shape, initially with a higher growth rate towards one edge of the notch before the propagation rate along the crack front became essentially independent of position. The phase congruency of the displacement field was used to measure the crack shape. The three-dimensional stress intensity factors were calculated via a linear elastic finite element model that used the displacement fields around the crack front as the boundary conditions. Closure of the crack tip region was observed. The cyclic change in the local mode I opening of the crack tip determined the local fatigue crack propagation rate along the crack front.

The cavitation-induced fragmentation of primary crystals formed in Al alloys were investigated for the first time by high-speed imaging using a novel experimental approach. Three representative primary crystal types, Al3Ti, Si and Al3V with different morphologies and mechanical properties were first extracted by deep etching of the corresponding Al alloys and then subjected to ultrasonic cavitation processing in distilled water. The dynamic interaction between the cavitation bubbles and primary crystals was imaged in-situ and in real time. Based on the recorded image sequences, the fragmentation mechanisms of primary crystals were studied. It was found that there are three major mechanisms by which the primary crystals were fragmented by cavitation bubbles. The first one was a slow process via fatigue-type failure. A cyclic pressure exerted by stationary pulsating bubbles caused the *Manuscript Click here to view linked References 2 propagation of a crack pre-existing in the primary crystal to a critical length which led to fragmentation. The second mechanism was a sudden process due to the collapse of bubbles in a passing cavitation cloud. The pressure produced upon the collapse of the cloud promoted rapid monotonic crack growth and fast fracture in the primary crystals. The third observed mechanism was normal bending fracture as a result of the high pressure arising from the collapse of a bubble cloud and the crack formation at the branch connection points of dendritic primary crystals. The fragmentation of dendrite branches due to the interaction between two freely moving dendritic primary crystals was also observed. A simplified fracture analysis of the observed phenomena was performed. The specific fragmentation mechanism for the primary crystals depended on their morphology and mechanical properties. The authors acknowledge the financial support from UK Engineering and Physical Science Research Council (EPSRC) for the Ultra-Cast project (grant EP/L019884/1, EP/L019825/1, EP/L019965/1). The authors are also grateful to the Diamond Light Source Ltd for the loan of the high speed camera system. UK Engineering and Physical Science Research Council (EPSRC) Ultra-Cast project (grant EP/L019884/1, EP/L019825/1, EP/L019965/1).

Ultrasonic melt processing is a promising technique for microstructural refinement in castings. Several mechanisms have been proposed for the observed effects, including cavitation-induced nucleation, activation of substrates and fragmentation. Until now, however, real-time experimental observations which could clarify any of the above mechanisms are very limited. For the first time we directly observed the fragmentation of primary crystals formed in alloys by ultrasonic cavitation. The primary crystals were extracted from real Al alloys and subjected to ultrasonic processing in water with in situ high-speed filming. The recordings of fragmentation of the primary crystals allowed us to observe the different mechanisms of fragmentation, depending on the mechanical properties and morphology of the primary crystals. The collapse of cavitation bubbles in water is less violent than that in liquid aluminum due to the lower cavitation threshold, viscosity and surface tension. Therefore the fragmentation mechanisms for the primary crystals observed in water should also be present for the same primary crystals in the more violent cavitation situation in liquid aluminum. The authors acknowledge the financial support from UK Engineering and Physical Science Research Council (EPSRC) for the Ultra-Cast project (grant EP/L019884/1, EP/L019825/1, EP/L019965/1). The authors are also grateful to Diamond Light Source Ltd for the loan of high speed camera.