Niobium tungsten oxides for high-rate lithium-ion energy storage.

The maximum power output and minimum charging time of a lithium-ion battery depend on both ionic and electronic transport. Ionic diffusion within the electrochemically active particles generally represents a fundamental limitation to the rate at which a battery can be charged and discharged. To compensate for the relatively slow solid-state ionic diffusion and to enable high power and rapid charging, the active particles are frequently reduced to nanometre dimensions, to the detriment of volumetric packing density, cost, stability and sustainability. As an alternative to nanoscaling, here we show that two complex niobium tungsten oxides-Nb16W5O55 and Nb18W16O93, which adopt crystallographic shear and bronze-like structures, respectively-can intercalate large quantities of lithium at high rates, even when the sizes of the niobium tungsten oxide particles are of the order of micrometres. Measurements of lithium-ion diffusion coefficients in both structures reveal room-temperature values that are several orders of magnitude higher than those in typical electrode materials such as Li4Ti5O12 and LiMn2O4. Multielectron redox, buffered volume expansion, topologically frustrated niobium/tungsten polyhedral arrangements and rapid solid-state lithium transport lead to extremely high volumetric capacities and rate performance. Unconventional materials and mechanisms that enable lithiation of micrometre-sized particles in minutes have implications for high-power applications, fast-charging devices, all-solid-state energy storage systems, electrode design and material discovery.K.J.G. gratefully acknowledges support from The Winston Churchill Foundation of the United States, the Herchel Smith Scholarship, and the Science and Technology Facilities Council Futures Early Career Award. K.J.G and C.P.G thank the EPSRC via the LIBATT grant (EP/P003532/1). L.E.M. was funded by the European Union’s Horizon 2020 – European Union research and innovation program under the Marie Skłodowska–Curie grant agreement No. 750294. We thank Dr. Ieuan Seymour, University of Cambridge, and Prof. Bruce Dunn, University of California, Los Angeles, for fruitful discussions. We thank Drs. Jeremy Skepper and Heather Greer, University of Cambridge, for assistance with the electron microscopy and Dr. Maxim Avdeev, Bragg Institute, for his bond valence sum mapping program. We thank Dr. Olaf Borkiewicz, Advanced Photon Source, Argonne National Laboratory and Alisha Kasam, University of Cambridge for diffraction data reduction scripts. We thank Diamond Light Source for access to beamline B18 (SP14956, SP16387, SP17913) that contributed to the results presented here. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE- AC02-06CH11357

Molybdenum sputtering film characterization for high gradient accelerating structures

Technological advancements are strongly required to fulfill the demands of new accelerator devices with the highest accelerating gradients and operation reliability for the future colliders. To this purpose an extensive R&D regarding molybdenum coatings on copper is in progress. In this contribution we describe chemical composition, deposition quality and resistivity properties of different molybdenum coatings obtained via sputtering. The deposited films are thick metallic disorder layers with different resistivity values above and below the molibdenum dioxide reference value. Chemical and electrical properties of these sputtered coatings have been characterized by Rutherford backscattering, XANES and photoemission spectroscopy. We will also present a three cells standing wave section coated by a molybdenum layer $\sim$ 500 nm thick designed to improve the performance of X-Band accelerating systems.Comment: manuscript has been submitted and accepted by Chinese Physics C (2012

Nanoscale polar heterogeneities and branching Bi-displacement directions in K0.5Bi0.5TiO3

K0.5Bi0.5TiO3 (KBT)—one of the few perovskite-like ferroelectric compounds with room-temperature tetragonal symmetry—differs from other members of its family (BaTiO3 and PbTiO3) by the presence of a disordered mixture of K and Bi on cuboctahedral sites. This disorder is expected to affect local atomic displacements and their response to an applied electric field. We have derived nanoscale atomistic models of KBT by refining atomic coordinates to simultaneously fit neutron/X-ray total scattering and extended X-ray absorption fine-structure data. Both Bi and Ti ions were found to be offset relative to their respective oxygen cages in the high-temperature cubic phase; in contrast, the coordination environment of K remained relatively undistorted. In the cubic structure, Bi displacements prefer the ⟨100⟩ directions and the probability density distribution of Bi features six well-separated sites; a similar preference exists for the much smaller Ti displacements, although the split sites for Ti could not be resolved. The cation displacements are correlated, yielding polar nanoregions, whereas on average, the structure appears as cubic. The cubic ↔ tetragonal phase transition involves both order/disorder and displacive mechanisms. A qualitative change in the form of the Bi probability density distribution occurs in the tetragonal phase on cooling to room temperature because Bi displacements “branch off” to ⟨111⟩ directions. This change, which preserves the average symmetry, is accompanied by the development of nanoscale polar heterogeneities that exhibit significant deviations of their polarization vectors from the average polar axis

Identification of control strategies to manage microbiological risks in typical pork products

Starting from 2009 a pilot project has been implemented by a local veterinary service of the Veneto region of Italy (AZ-ULSS 8) in collaboration with IZSVe (Istituto Zooprofilattico Sperimentale delle Venezie) with the aim of identifying control measures based on own-checks and official controls in order to manage microbiological risks related to traditional pork fermented sausages (Italian salami end soppresse) consumption. According to the data obtained a control strategy based on microbiological tests performed by the Competent Authority (CA) and the monitoring of the weight decrease in sausages by the food business operator (FBO) has been implemented for 2010-2011 production season

NEOSTEL: the telescope detail design program for the ESA optical ground network dedicated to NEO discovery and tracking

The Fly-Eye architecture applied for a Space Debris and NEO Surveillance and Tracking optical telescope has been originally proposed by CGS and further refined in the framework of the Space Situational Awareness (SSA) Preparatory Program studies. The high level architecture of a Telescope based on the Fly-Eye concept has been defined in the TELAD Study. Following TELAD conceptual design, the activities of NEOSTEL aim now at generating the Detailed Design of a NEO Survey Telescope based on the Fly-Eye concept. All components of the telescope are designed at detailed level to satisfy the specific requirements for the Survey and Follow Up of the Near Earth Objects. The NEO Survey Telescope detailed design generated under this Program will be directly utilized for the manufacturing of the first prototype, planned to be launched by the SSA Program in the second half of 2015. In addition, the result of the Detailed Design will produce the documentation necessary to prepare the future site that will host the NEO Survey Telescope prototype as well as the high level architecture of the data processing SW that will be required at the telescope site. The product of the prototypation activity will then constitute a full Italian key Optical Core Technology, dedicated to the NEO thematic but also extendable to the SST Segment, therefore offering possibility of application both at Civil and at Institutional level. Furthermore the Fly-Eye Telescope Technology can actively collaborate with a dedicated Space Segment, opening the way to a complete and autonomous EU System

Deep ice as a geochemical reactor: Insights from iron speciation and mineralogy of dust in the Talos Dome ice core (East Antarctica)

Thanks to its insolubility, mineral dust is considered a stable proxy in polar ice cores. With this study we show that the Talos Dome ice core (TALDICE, Ross Sea sector of East Antarctica) displays evident and progressive signs of post-depositional processes affecting the mineral dust record below 1000g m deep. We apply a suite of established and cutting-edge techniques to investigate the properties of dust in TALDICE, ranging from concentration and grain size to elemental composition and Fe mineralogy. Results show that through acidic/oxidative weathering, the conditions of deep ice at Talos Dome promote the dissolution of specific minerals and the englacial formation of others, affecting primitive dust features. The expulsion of acidic atmospheric species from ice grains and their concentration in localized environments is likely the main process responsible for englacial reactions. Deep ice can be seen as a "geochemical reactor"capable of fostering complex reactions which involve both soluble and insoluble impurities. Fe-bearing minerals can efficiently help in exploring such transformations

Operando potassium K-edge X-ray absorption spectroscopy: investigating potassium catalysts during soot oxidation.

The chemical and structural nature of potassium compounds involved in catalytic soot oxidation have been studied by a combination of temperature programmed oxidation and operando potassium K-edge X-ray absorption spectroscopy experiments. These experiments are the first known operando studies using tender X-rays (∼3.6 keV) under high temperature oxidation reaction conditions. X-ray absorption near edge structure analysis of K2CO3/Al2O3 catalysts during heating shows that, at temperatures between 100 and 200 °C, potassium species undergo a structural change from an initial hydrated K2CO3·xH2O and KHCO3 mixture to well-defined K2CO3. As the catalyst is heated from 200 °C to 600 °C, a feature associated with multiple scattering shifts to lower energy, indicating increased K2CO3 dispersion, due to its mobility at high reaction temperature. This shift was noted to be greater in samples containing soot than in control experiments without soot and can be attributed to enhanced mobility of the K2CO3, due to the interaction between soot and potassium species. No potassium species except K2CO3 could be defined during reactions, which excludes a potential reaction mechanism in which carbonate ions are the active soot-oxidising species. Simulations of K-edge absorption near edge structures were performed to rationalise the observed changes seen. Findings showed that cluster size, unit cell distortions and variation in the distribution of potassium crystallographic sites influenced the simulated spectra of K2CO3. While further simulation studies are required for a more complete understanding, the current results support the hypothesis that changes in the local structure on dispersion can influence the observed spectra. Ex situ characterisation was carried out on the fresh and used catalyst, by X-ray diffraction and X-ray photoelectron spectroscopy, which indicated changes to the carbonate species, in line with the X-ray absorption spectroscopy experiments

Operando XAFS investigation on the effect of ash deposition on three-way catalyst used in gasoline particulate filters and the effect of the manufacturing process on the catalytic activity

Platinum group metals such as palladium and rhodium based catalysts are currently being implemented in gasoline particulate filter (GPF) autoexhaust after treatment systems. However, little is known about how the trapped particulate matter, such as the incombustible ash, interacts with the catalyst and so may affect its performance. This operando study follows the evolution of the Pd found in two different model GPF systems: one containing ash components extracted from a GPF and another from a catalyst washcoat prior to adhesion onto the GPF. We show that the catalytic activity of the two systems vary when compared with a 0 g ash containing GPF. Compared to the 0 g ash sample the 20 g ash containing sample had a higher CO light off temperature, in addition, an oscillation profile for CO, CO2 and O2 was observed, which is speculated to be a combination of CO oxidation, C deposition via a Boudouard reaction and further partial oxidation of the deposited species to CO. During the ageing procedure the washcoat sample reduces NO at a lower temperature than the 0 g ash sample. However, post ageing the 0 g ash sample recovers and both samples reduce NO at 310 °C. In comparison, the 20 g ash GPF sample maintains a higher NO reduction temperature of 410 °C post ageing, implying that the combination of high temperature ageing and presence of ash has an irreversible negative effect on catalyst performance