Failure caused by dendrite growth in high-energy-density, rechargeable batteries with lithium metal anodes has prevented their widespread use in applications ranging from consumer electronics to electric vehicles. Efforts to solve the lithium dendrite problem have focused on preventing the growth of protrusions from the anode surface. Synchrotron hard X-ray microtomography experiments on symmetric lithium-polymer-lithium cells cycled at 90 °C show that during the early stage of dendrite development, the bulk of the dendritic structure lies within the electrode, underneath the polymer/electrode interface. Furthermore, we observed crystalline impurities, present in the uncycled lithium anodes, at the base of the subsurface dendritic structures. The portion of the dendrite protruding into the electrolyte increases on cycling until it spans the electrolyte thickness, causing a short circuit. Contrary to conventional wisdom, it seems that preventing dendrite formation in polymer electrolytes depends on inhibiting the formation of subsurface structures in the lithium electrode.

There is a need to understand the structure properties of gas-diffusion layers (GDLs) in order to optimize their performance in various electrochemical devices. This information is important for mathematical modelers, experimentalists, and designers. In this article, a comprehensive study of a large set of commercially available GDLs' porosity, tortuosity, and pore-size distribution under varying compression is presented in a single study using X-ray computed tomography (CT), which allows for a noninvasive measurement. Porosities and PSDsare directly obtained from reconstructed stacks of images, whereas tortuosity is computed with a finite-element simulation. Bimodal PSDsdue to the presence of binder are observed for most of the GDLs, approaching unimodal distributions at high compressions. Sample to sample variability is conducted to show that morphological properties hold across various locations. Tortuosity values are the lowest for MRC and Freudenberg, highest for TGP, and somewhere in-between for SGL papers. The exponents for the MRC and Freudenberg tortuosity have very small dependence on compression because the shapes of the pores are spherical indicating minimal heterogeneity. From the representative elementary volume studies it is shown that volumes of 1x1 mm in-plane and full thickness in through-plane directions accurately represent GDL properties.

Weathering disaggregates rock into regolith – the fractured or granular earth material that sustains life on the continental land surface. Here, we investigate what controls the depth of regolith formed on ridges of two rock compositions with similar initial porosities in Virginia (USA). A priori, we predicted that the regolith on diabase would be thicker than on granite because the dominant mineral (feldspar) in the diabase weathers faster than its granitic counterpart. However, weathering advanced 20× deeper into the granite than the diabase. The 20 × ‐thicker regolith is attributed mainly to connected micron‐sized pores, microfractures formed around oxidizing biotite at 20 m depth, and the lower iron (Fe) content in the felsic rock. Such porosity allows pervasive advection and deep oxidation in the granite. These observations may explain why regolith worldwide is thicker on felsic compared to mafic rock under similar conditions. To understand regolith formation will require better understanding of such deep oxidation reactions and how they impact fluid flow during weathering. Copyright © 2012 John Wiley & Sons, Ltd.

Ceramic matrix composites are the emerging material of choice for structures that will see temperatures above ~1,500 °C in hostile environments, as for example in next-generation gas turbines and hypersonic-flight applications. The safe operation of applications depends on how small cracks forming inside the material are restrained by its microstructure. As with natural tissue such as bone and seashells, the tailored microstructural complexity of ceramic matrix composites imparts them with mechanical toughness, which is essential to avoiding failure. Yet gathering three-dimensional observations of damage evolution in extreme environments has been a challenge. Using synchrotron X-ray computed microtomography, we have fully resolved sequences of microcrack damage as cracks grow under load at temperatures up to 1,750 °C. Our observations are key ingredients for the high-fidelity simulations used to compute failure risks under extreme operating conditions.

We used soft x-ray tomography (SXT) – a high-resolution, quantitative imaging technique – to measure cell size and organelle volumes in yeasts. Cell size is a key factor in initiating cell division in yeasts, whereas the number and volume of the organelles has a profound impact on the function and viability of a cell. Consequently, determining these cell parameters is fundamentally important in understanding yeast biology. SXT is well suited to this type of analysis. Specimens are imaged in a near-native state, and relatively large numbers of cells can be readily analyzed. In this study, we characterized haploid and diploid strains of Saccharomyces cerevisiae at each of the key stages in the cell cycle, and determined if there were relationships between cellular and organelle volumes. We then compared these results with SXT data obtained from Schizosaccharomyces pombe, the three main phenotypes displayed by the opportunistic yeast pathogen Candida albicans, and from a coff1-22 mutant strain of Saccharomyces cerevisiae. This comparison revealed that volumetric ratios were invariant irrespective of yeast strain, ploidy or morphology, leading to the conclusion these volumetric ratios are common in all yeasts.