Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by 7 Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.

To say it briefly, this is a marvellous book. It describes in depth and richly illustrates the wood structure of some 180 trade timbers belonging to approximately 60 families. This edition in the English language finally allows access for non-Japanese scientists, wood engineers and applicants of wood to the lifetime work of Ken Ogata, one of the foremost wood anatomists of our time. Contrary to gloomy predictions that by the year 2000 world timber trade would be largely restricted to plantation-grown pines and eucalypts and products manufactured thereof, the diversity of tropical timbers shipped to the main importing countries, such as China, Japan and EU countries, has actually increased. This is a constant challenge for those involved in wood identification. Representatives of wood industry and trade are the traditional and still the most important customers for this service. But on the other hand, also archaeologists, architects, paleobotanists, and, more recently, agencies responsible for monitoring and controlling trade with protected plants and activities concerning illegal logging are also seeking help and advice from wood anatomists responsible for timber identification. And this is what this book addresses.From A (Alangiaceae) to V (Verbenaceae), each hardwood timber description gives a brief explanation of the botanical and trade nomenclature and the geographical distribution of a trade timber, followed by concise description of macroscopic and microscopic features. Nearly all comments are accompanied by accurate line drawings highlighting structural patterns and specific features. Moreover, a series of excellent half-tone illustrations cover a wide range of magnifications on macroscopic, microscopic and SEM level and explain structural features of the woods in question. In addition,

A systematic study of the kinetics of axial Ni silicidation of as-grown and oxidized Si nanowires (SiNWs) with different crystallographic orientations and core diameters ranging from ∼ 10 to 100 nm is presented. For temperatures between 300 and 440 °C the length of the total axial silicide intrusion varies with the square root of time, which provides clear evidence that the rate limiting step is diffusion of Ni through the growing silicide phase(s). A retardation of Ni-silicide formation for oxidized SiNWs is found, indicative of a stress induced lowering of the diffusion coefficients. Extrapolated growth constants indicate that the Ni flux through the silicided NW is dominated by surface diffusion, which is consistent with an inverse square root dependence of the silicide length on the NW diameter as observed for (111) orientated SiNWs. In situ TEM silicidation experiments show that NiSi(2) is the first forming phase for as-grown and oxidized SiNWs. The silicide-SiNW interface is thereby atomically abrupt and typically planar. Ni-rich silicide phases subsequently nucleate close to the Ni reservoir, which for as-grown SiNWs can lead to a complete channel break-off for prolonged silicidation due to significant volume expansion and morphological changes.

Nano-structured silicon is an attractive alternative anode material to conventional graphite in lithium-ion batteries. However, the anode designs with higher silicon concentrations remain to be commercialized despite recent remarkable progress. One of the most critical issues is the fundamental understanding of the lithium–silicon Coulombic efficiency. Particularly, this is the key to resolve subtle yet accumulatively significant alterations of Coulombic efficiency by various paths of lithium–silicon processes over cycles. Here, we provide quantitative and qualitative insight into how the irreversible behaviors are altered by the processes under amorphous volume changes and hysteretic amorphous–crystalline phase transformations. Repeated latter transformations over cycles, typically featured as a degradation factor, can govern the reversibility behaviors, improving the irreversibility and eventually minimizing cumulative irreversible lithium consumption. This is clearly different from repeated amorphous volume changes with different lithiation depths. The mechanism behind the correlations is elucidated by electrochemical and structural probing.

We report on a new class of cocatalysts for the chemical vapor deposition of carbon nanotubes, where the cocomponent (Ta) acts as a solid-state reducing agent for the active catalyst (Fe). The cocatalytic FeTa system enables carbon nanotube growth without the need for a reducing gas atmosphere such as H2 or NH3. In situ X-ray photoelectron spectroscopy reveals that the tantalum (oxide) getters the oxygen from the iron (oxide) by a diffusive solid-state process, driven by the much larger affinity to oxygen of Ta compared to Fe. We suggest that this redox-based mechanism is applicable to a wide range of metal (oxide)/catalyst systems and relevant to rational catalyst design in general heterogeneous catalysis

We demonstrate a stretched contact printing technique to assemble one-dimensional nanostructures with controlled density and orientation from either dry or wet sources. The random, chaotically arranged nanostructures can gradually transform to a highly aligned configuration. Our results show that up to 90% of the printed nanowires are aligned within ±15° of the primary stretching direction. This approach is easily applicable to a variety of nanowires and nanotubes on different substrates, and we demonstrate various field effect transistors with nanowire and hybrid nanowire–polymer networks. The hybrid inorganic–organic transistors based on a parallel aligned nanowire network and a semiconducting polymer revealed a significant enhancement in transistor mobility, a 10-fold reduction in subthreshold slope (∼0.26 V decade–1), and superior air stability compared to a pristine polymer host.

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