Influence of the electrode nano/microstructure on the electrochemical properties of graphite in aluminum batteries

Herein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4- in graphite, has been fully characterized by correlating the micro/nanostructural modification to the electrochemical performance. To achieve this aim a combination of X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and computed tomography (CT) has been used. The reported results evidence that the irreversibility is caused by a very large decrease in the porosity, which consequently leads to microstructural changes resulting in the trapping of ions in the graphite. A powerful characterization methodology is established, which can also be applied more generally to carbon-based energy-related materials

Small angle x-ray and neutron scattering study of disordered and three dimensional-ordered magnetic protein arrays

Copyright © 2009 American Institute of PhysicsProceedings of the 53rd Annual Conference on Magnetism and Magnetic Materials, Austin, Texas, 11-14 November 2008The magnetic nanoparticles of Fe3O4-γ–Fe2O3 grown inside the cavity of globular proteins (apoferritin)-magnetoferritin proved to be a useful model system for studying the fundamental effects of magnetostatic interactions in nanoparticle assemblies. In this work the main focus is on structural characterization of such new nanocomposites by small angle x-ray scattering (SAXS) and small angle neutron scattering to evaluate interparticle separation (center to center) in two types of assemblies: three dimensional periodic arrays and disordered (amorphous) assemblies. Straightforward analysis of the face-centered cubic pattern of periodic arrays revealed that the interparticle spacing is 9.9 nm, whereas the SAXS pattern of disordered assembly reveals three correlation lengths, one of which is 10.5 nm and corresponds to the interparticle (center-to-center) nearest neighbor distance. The magnetic behaviors of the two systems are distinctly different. Given that the interparticle separation differs by only ∼ 0.6 nm, the main structural factor contributing to the observed differences in magnetic properties is likely to be the array order

Identifying the location of Cu ions in nanostructured SAPO 5 molecular sieves and its impact on the redox properties

Combining X ray Absorption Fine Spectroscopy XAFS with Anomalous Small Angle X ray Scattering ASAXS determines the location of Cu2 ions in silicoaluminophosphate SAPO 5 frameworks prepared by hydrothermal crystallization or impregnation. As expected, for the hydrothermally prepared sample, incorporation in the SAPO 5 framework was observed. For the first time preferential location of Cu2 ions at the inner and outer surfaces of the framework is determined. Temperature Programmed Reduction TPR and X ray Photoelectron Spectroscopy XPS investigations demonstrated that such Cu2 is stable in an argon Ar atmosphere up to 550 C and can only be reduced under a hydrogen atmosphere. In contrast, Cu2 deposited by impregnation on the pure SAPO 5 framework can be easily reduced to Cu in an Ar atmosphere. At lower Cu amounts, mononuclear tetrahedrally coordinated Cu species were formed which are relatively stable in the monovalent form. In contrast, at higher Cu amounts, CuO particles were found which change easily between the mono and bivalent specie

Laser-induced surface modification of biopolymers - Micro/nanostructuring and functionalization

The medical-grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial in medicine for preparation of high-tech devices because of its remarkable properties. In this paper, we present experimental results on surface modification of PDMS elastomer by using ultraviolet, visible, and near-infrared ns-laser system and investigation of the chemical composition and the morphological structure inside the treated area in dependence on the processing parameters - wavelength, laser fluence and number of pulses. Remarkable chemical transformations and changes of the morphological structure were observed, resulting in the formation of a highly catalytically active surface, which was successfully functionalized via electroless Ni and Pt deposition by a sensitizing-activation free process. The results obtained are very promising in view of applying the methods of laser-induced micro- and nano-structuring and activation of biopolymers' surface and further electroless metal plating to the preparation of, e.g., multielectrode arrays (MEAs) devices in neural and muscular surface interfacing implantable systems

Influence of the electrode nano microstructure on the electrochemical properties of graphite in aluminum batteries

Herein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1 ethyl 3 methylimidazolium chloride aluminum trichloride EMIMCl AlCl3 as electrolyte. The reaction mechanism, involving the intercalation of AlCl4 in graphite, 3 has been fully characterized by correlating the micro nano modification to the electrochemical performance. To achieve this aim a combination of X ray diffraction XRD , small angle X ray scattering SAXS and computed tomography CT has been used. The reported results evidence that the irreversibility is caused by a very large decrease in the porosity, which consequently leads to microstructural changes resulting in the trapping of ions in the graphite. A powerful characterization methodology is established, which can also be applied more generally to carbon based energy related material

The Sariçiçek Howardite Fall in Turkey: Source Crater of HED Meteorites on Vesta and İmpact Risk of Vestoids

The Sariçiçek howardite meteorite shower consisting of 343 documented stones occurred on 2 September 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariçiçek experienced a complex cosmic ray exposure history, exposed during ~12–14 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 ± 2 Ma ago to Earth (as did one third of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 ± 2.5 Ma and 4553 ± 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite U-Pb age of 4525 ± 17 Ma, K-Ar age of ~3.9 Ga, and the U,Th-He ages of 1.8 ± 0.7 and 2.6 ± 0.3 Ga are interpreted to represent thermal metamorphic and impact-related resetting ages, respectively. Petrographic, geochemical and O-, Cr- and Tiisotopic studies confirm that Sariçiçek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariçiçek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 ± 0.8 kms-1 from NW, fragmentations at 37, 33, 31 and 27 km altitude, and provide a pre-atmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariçiçek with the Vesta asteroid family (V-class) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids ≤4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antonia impact crater on Vesta was formed on terrain of the same age as given by the 4He retention age of Sariçiçek. Lunar scaling for crater production to crater counts of its ejecta blanket show it was formed ~22 Ma ago

Structure analysis of multiphase systems by anomalous small angle X ray scattering

International audienceThe theory of the small-angle scattering is reviewed with special attention paid to the anomalous scattering and multiphase systems. A general equation describing the scattering of a multiphase system as a sum of scattering functions of each of the phases, as if it scattered alone in a two phase system, and interphase interference scattering functions is derived. These scattering functions depend only on the spatial distribution of the phase boundaries, but not on the scattering density. Contrast variation techniques are most rewarding when the scattering density of only one phase can be varied. For ASAXS, this means the most favorable is the case in which resonant atoms are contained in one phase only. The general equation involves n(p-1) unknown partial atomic number density differences, where p is the number of phases and n - the number of the different atom types in the sample. These partial atomic number density differences can be found if a suitable structure model is applied to calculate the phase scattering functions. Then, the phase compositions and densities can be calculated by solving a system of linear equations incorporating the atom number conservation law. The partial structure factors formalism is also reviewed. Corresponding equations for a system of n types of atoms and p phases are derived. The number of independent partial structure factors is p(p-1)/2 and depends on the number of phases, but not on the number of the types of the atoms in the sample, as in the case of wide angle scattering