Effects of Relaxation on Conversion Negative Electrode Materials for Li-Ion Batteries: A Study of TiSnSb Using 119Sn Mössbauer and 7Li MAS NMR Spectroscopies

Conversion materials were recently considered as plausible alternatives to conventional insertion negative electrode materials in lithium-ion batteries due to their large gravimetric and volumetric energy densities. The ternary alloy TiSnSb was recently proposed as a suitable negative electrode material due to its large capacity (550 mA h g–1) and rate capability over many cycles. TiSnSb has been investigated at the end of lithiation (discharge) using 119Sn Mössbauer and 7Li magic-angle spinning (MAS) NMR spectroscopies to determine the species formed, their relative stabilities and their behavior during relaxation. During discharge, TiSnSb undergoes a conversion reaction to produce a mixture of phases believed to consist of lithium antimonides, lithium stannides, and titanium metal. In situ 119Sn Mössbauer spectroscopy indicates the presence of Li7Sn2 at the end of discharge, while 7Li NMR experiments suggest the formation of two distinct Sn-containing species (tentatively assigned to Li7Sn2 and Li7Sn3), in addition to two Sb-containing species (tentatively assigned as Li3Sb and a non-stoichiometric phase of Li2Sb, Li2–xSb). To gain insight into the relative stabilities of the species formed, experiments have been completed under open circuit voltage conditions. A new Sn-based species has been identified via 119Sn Mössbauer spectroscopy at the end of relaxation. Similar changes are observed in the 7Li NMR spectra obtained during relaxation. The species created at the end of discharge are extremely unstable and spontaneously evolve towards delithiated phases. Surprisingly, it is possible to resume electrochemical cycling after relaxation. It is likely that this behavior can be extended to this family of electrode materials that undergo the conversion reaction

GrassPlot - a database of multi-scale plant diversity in Palaearctic grasslands

GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetationplot databases, such as the European Vegetation Archive (EVA) and the global database " sPlot". Its main aim is to facilitate studies on the scale-and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board

Сверхлегкие генераторные модули для КВЧ-терапии

Разработаны миниатюрные генераторные модули для КВЧ-терапии, лег-ко фиксируемые в любом месте тела пациента. Могут быть использованы не только в медицине

Exploring the interplay of landscape changes and ecosystem services maximization in man-managed lagoon areas

Coastal lagoons have long been subject to continuous changes caused by mutual interactions with human activities. Monitoring such changes becomes critical, particularly when modifications in landscape and land cover classes can affect their capacity to ensure Ecosystem Services (ESs). In the Venice lagoon, some confined areas called “valli da pesca” supply provisioning ESs, namely aquaculture and hunting, but also other ESs important for the entire lagoon, such as regulating and cultural ones. Being heavily modified ecosystems under human control, valli da pesca underwent considerable morphological evolution depending on the maximized ES and the applied management. Using remote sensing data from different sources, we reconstructed changes in land cover and landscape elements in valli da pesca over the last century. By calculating landscape indicators related to land, saltmarshes, and water, we found that landscape features were initially similar for all the valli da pesca. Then, a process began between 1975 and 1987, in which management devoted to maximizing different ESs shaped the land cover in specific patterns. This study confirms the importance of these areas in the context of the entire lagoon and suggests the need to monitor their land cover changes to avoid the depletion of their capacity to conserve landscape elements and the related ESs. In this task, remote sensing data represents an important source of historical data that can deepen the knowledge about human-Nature interactions, capable of tracing the landscape evolution and the dynamics in the ESs supply as responses to human interventions

MnP4 electrode for Na-ion batteries: a complex and effective electrochemical mechanism

International audienceMnP 4 has recently been identified as a possible negative electrode for Li-ion batteries. This study shows that this material can also perform as a negative electrode for Na-ion batteries (SIBs), demonstrating that a suitable electrode formulation allows an exceptional performance, i.e., a stable specific capacity of 1000 mA h g −1 after 50 cycles, much higher than that of hard-carbon-based anodes currently used in SIBs. The combination of operando X-ray diffraction, ex situ Mn K-edge X-ray absorption spectroscopy (XAS) and NMR spectroscopy reveals a complex conversion mechanism with the formation of numerous amorphous sodiated phosphide species. 31 P and 13 Na NMR were particularly effective in identifying these species, demonstrating that their formation is dependent on the preparation of the electrode, especially the amount of carbon additive. XAS analysis, on the other hand, proved the complete reversibility of the mechanism, including the reformation of MnP 4 during the desodiation process

Suivi du comportement mécanique d’une peinture sur bois soumise à des variations d’hygrométrie

International audienceCe travail collaboratif (présenté lors de la précédente journée) regroupe le musée Fabre, des restaurateurs mobilier et couche picturale ainsi que des chercheurs du GESAAF (Université de Florence), de l’institut PPRIME (Université de Poitiers) et du LMGC (Université de Montpellier). Le but de cette étude est la caractérisation du comportement mécanique d’un panneau de bois peint du patrimoine soumis à des variations d’environnement hygrothermique contrôlées. Dans la perspective d’une exposition prévue en 2018 et destinée à destinée à faire connaître les pratiques de la restauration des œuvres d’art au public, la communication sur cette interaction entre acteurs patrimoniaux et académique fait l’objet d’une attention particulière

Probing the role of the so-called inactive transition metal in conversion reactions: not so inactive!

International audienceTernary alloys such as TiSnSb and NbSnNb have been proposed as suitable negative electrode materials for lithium-ion batteries due to their large capacities and rate capability over many cycles. During lithiation, TiSnSb undergoes a conversion reaction, leading to the formation of multiple, highly reactive species. Previous in situ 119Sn Mössbauer and 7Li magic-angle spinning (MAS) NMR spectroscopic studies suggested the phases Li3Sb, Li7Sn2, Li7Sn3 and Li2−xSb are formed at the end of lithiation alongside Ti or Nb nanoparticles. However, their stability and overall contribution to the conversion reaction is not yet fully understood. A series of model Sn- and Sb-based mixtures and alloys (both binary and ternary) have been investigated at the end of lithiation using 7Li MAS NMR spectroscopy to determine both the phases formed and their contribution to the conversion reaction. In all cases, a mixture of reactive lithiated phases and metallic nanoparticles are formed at the end of lithiation. Changing the nature of the inactive element in binary and ternary alloys changes the local Li environment and the observed chemical shifts. Considerable differences in chemical shift are observed for alloys relative to less intimate mixtures. The synthetic conditions used, particularly the intimacy of mixing achieved during synthesis, is key in determining both the phases formed and how the reaction proceeds, i.e., via a conversion or alloying reaction. The data presented show that the so-called “inactive” element and its nature in fact plays a key role in the conversion mechanism and therefore influences the ability for this class of materials to be commercialised in the future

Studies for the Mona Lisa conservation

International audienceSince 2004, the wooden panel of the “Mona Lisa” painting by Leonardo da Vinci has been studied by an internationalresearch group of scientists [1,2] and several experimental campaigns have been carried out to understand itscharacteristics and provide information for the Artwork's conservation [3]. Among these, the implementation of its"digital twin" is here presented as a fundamental step for its conservation. Indeed, this digital twin is providing a deeperunderstanding of the mechanical characteristics of the panel, and after it has been accurately calibrated, it will providethe means for evaluating the stress states which the Artwork undergoes when the surrounding climatic conditions vary.Moreover, it will allow to evaluate in a non-invasive way the effects produced on the Artwork by any changes of itsframing conditions, including the internal stresses or the external forces that it can bear without damage.The implementation of the digital twin, through a Nelder-Mead optimization scheme, starts from the definition of theshape of the Artwork, through optical methods [4], and the identification of the boundary conditions, through anexperimental campaign based on the use of a film sensitive to pressure [5]. During the whole year, while exhibited inthe conditioned display case, the panel continuously tends to deform, due to the slight variations in the surroundingenvironment. Its mechanical behaviour is automatically monitored and recorded every 30 minutes by an ad hocequipment placed close to its back face: four miniature load cells (located at the four corners) measure the forces pressingit against the frame, and three displacement transducers measure its deflection at mid height. Finally, a method is heredescribed to compare two different framing conditions, through the numerical computation of point-by-point stress anddeformation differences, in order to provide information for optimizing settings and constraints to Conservators

Studies for the Mona Lisa conservation

International audienceSince 2004, the wooden panel of the “Mona Lisa” painting by Leonardo da Vinci has been studied by an internationalresearch group of scientists [1,2] and several experimental campaigns have been carried out to understand itscharacteristics and provide information for the Artwork's conservation [3]. Among these, the implementation of its"digital twin" is here presented as a fundamental step for its conservation. Indeed, this digital twin is providing a deeperunderstanding of the mechanical characteristics of the panel, and after it has been accurately calibrated, it will providethe means for evaluating the stress states which the Artwork undergoes when the surrounding climatic conditions vary.Moreover, it will allow to evaluate in a non-invasive way the effects produced on the Artwork by any changes of itsframing conditions, including the internal stresses or the external forces that it can bear without damage.The implementation of the digital twin, through a Nelder-Mead optimization scheme, starts from the definition of theshape of the Artwork, through optical methods [4], and the identification of the boundary conditions, through anexperimental campaign based on the use of a film sensitive to pressure [5]. During the whole year, while exhibited inthe conditioned display case, the panel continuously tends to deform, due to the slight variations in the surroundingenvironment. Its mechanical behaviour is automatically monitored and recorded every 30 minutes by an ad hocequipment placed close to its back face: four miniature load cells (located at the four corners) measure the forces pressingit against the frame, and three displacement transducers measure its deflection at mid height. Finally, a method is heredescribed to compare two different framing conditions, through the numerical computation of point-by-point stress anddeformation differences, in order to provide information for optimizing settings and constraints to Conservators