Papers by Author: Amelia Montone

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Authors: Daniele Mirabile Gattia, Marco Vittori Antisari, Renzo Marazzi, Luciano Pilloni, Vittoria Contini, Amelia Montone
Abstract: Carbon nanohorns and multiwalled carbon nanotubes have been synthesized by DC arcdischarge carried out at room pressure in air and Ar-enriched environment, by a specially designed experimental device. The resulting nanostructured material, characterized by electron microscopy and X-ray diffraction, shows different structures according to the condensation channels through which the sublimated carbon atoms are re-condensed in the solid state. Multi-Walled Carbon Nano- Tubes are mainly found in the hard crust formed at the cathode, while nano-horned particles can be recovered from a cylindrical collector surrounding the discharge. Further material, rag-like shaped and with an amorphous structure, can be collected in the reaction area. When the discharge occurs under Ar atmosphere, a larger quantity of this latter phase is synthesized. This suggests that the atmospheric oxygen could play an active role by burning the most reactive among the synthesized phases, like amorphous carbon contributing so to an “in situ” purification of the raw material.
Authors: Marco Vittori Antisari, Daniele Mirabile Gattia, L. Brandão, Renzo Marazzi, Amelia Montone
Abstract: Carbon nanostructures are under deep investigation due their peculiar properties and possible applications. In particular, development of new methods for the synthesis of these materials and their mechanism of formation represent interesting research fields. Arc discharge allows to produce different forms of carbon nanostructures. The parameters involved in the process, voltage, current density, type and pressure of the surrounding gas can be controlled especially for achieving high quantity of material with enhanced characteristics in terms of purity while the use of transition metal-graphite mixtures has been used to produce single wall structures. Moreover direct current (DC) and alternating current (AC) are suitable for producing carbon nano-materials, but different results can be obtained. In this work the effect of the power frequency in an AC arc discharge technique on the synthesis of carbon nanostructures is reported. Pure graphite electrodes have been arched in air in an homemade apparatus where the material can be collected directly on a cylindrical collector fixed near the arc. In order to avoid the formation of deposits under the arc a symmetrical configuration of the electrodes has been set. The production of carbon soot containing Single Wall Nanohorns (SWNH) and highly convoluted graphene sheets is optimized. The range of power frequencies 32-1000Hz has been investigated and the arcs have been ignited fixing the voltage at 28 V. The materials has been analyzed by field emission scanning electron microscope and high resolution transmission electron microscope. The microstructure of the material synthesized by this apparatus is affected by the power frequency, as the experimental results demonstrate. The samples produced at low frequency presented high amounts of single wall structures, SWNH-type. More compact structures, similar to large onion-like structures, have been found in samples synthesized at high frequency values.
Authors: C. Díaz-Guerra, Amelia Montone, J. Piqueras, Francsco Cardellini
Authors: Amelia Montone, Jasna Grbović Novaković, Lj. Stamenković, Anna Lisa Fiorini, Luca Pasquini, Ennio Bonetti, Marco Vittori Antisari
Abstract: The influence of the Co addition and synthesis route on desorption properties of MgH2 were investigated. Ball milling of MgH2-Co blends was performed under Ar using different milling intensities and different weight ratios. Microstructural and morphological characterization, performed by XRD and SEM, show a huge correlation with thermal stability and hydrogen desorption properties investigated by DSC. A complex desorption behaviour is correlated with the dispersion of the catalytic particles that appears to play a main role in desorption performances. The optimum catalyst concentration was found to be around 10 wt.%, while the optimum value of the ball to powder ratio was 10:1.
Authors: S. Mentus, Ivan Krstić, Ž. Tešić, Amelia Montone
Abstract: Potentiodynamic polarization of a mechanically polished titanium electrode in a diluted solution of Rhodium(III) chloride in 0.1 M perchloric acid was performed, resulting in simultaneous formation of both Rh and TiO2 films. The morphology of obtained Rh/TiO2 composite film followed the morphology of titanium support, as evidenced by SEM technique. This composite surface was examined by cyclic voltammetry in both acidic and alkaline solutions, in the potential region of both hydrogen and oxygen underpotential deposition. The charge related to hydrogen underpotential deposition corresponded to a surface roughness of 43. As a consequence of high surface roughness, the diffusion current of oxygen reduction in an oxygen saturated 0.1 M NaOH solution, measured by voltammetry on rotating disc electrode, was found to be comparable to the current of hydrogen underpotential deposition.
Authors: M. Angiolini, Marek Krasnowski, G. Mazzone, Amelia Montone, M. Urchulutegui, Marco Vittori Antisari
Authors: Fabrizio Cleri, Massimo Celino, Amelia Montone, Ennio Bonetti, Luca Pasquini
Abstract: Extensive electronic structure calculations, based on the density-functional theory, are used to characterize the equilibrium properties and the behaviour under pressure of MgH2. Moreover, substitutional solid solutions for several 3d metals (Fe, Ni, Ti, Al, Pd, Co, etc.) in MgH2 are characterized by computing both relaxed structures and solution energies. Theoretical results are combined with experimental results on samples synthesized by ball milling. MgH2 was milled with 10 wt.% of 3d metals followed by microstructural characterization and hydrogen desorption behaviour. Good correlation between theoretical solution energies and experimental desorption temperatures reveals a general trend in these systems. A few notable exceptions can be detected, which can be explained in terms of peculiarities in the experimental composite microstructure.
Authors: Jasna Grbović Novaković, T. Brdarić, N. Novaković, Lj. Matović, Amelia Montone, S. Mentus
Abstract: Magnesium based composites MgH2 + X (X=Ti, Co) were synthesized by ball milling in an argon atmosphere using stainless steel vial and balls. The crystallographic behavior of the resulting powders was examined by XRD. Thermal stability and hydrogen desorption properties were investigated by thermal analysis methods. In order to obtain a deeper insight into bonding mechanisms of the transition metal in MgH2 relaxed structure, ab initio electronic structure calculation of MgH2 + X (X=Ti, Co) was performed using Full Potential Linearized Augmented Plane Wave method, implemented in WIEN2K code. DOS analysis, confirmed by DTA measurements, resulted in the conclusion that, in the composite, in comparison to MgH2, the bonding Mg-H was weakened, on account of the shortening of interatomic distances hydrogentransition metal.
Authors: Simone Giusepponi, Massimo Celino, Fabrizio Cleri, Amelia Montone
Abstract: We studied the atomic-level structure of a model Mg-MgH2 interface by means of the Car-Parrinello molecular dynamics method (CPMD). The interface was characterized in terms of total energy calculations, and an estimate of the work of adhesion was given, in good agreement with experimental results on similar systems. Furthermore, the interface was studied in a range of temperatures of interest for the desorption of hydrogen. We determined the diffusivity of atomic hydrogen as a function of the temperature, and give an estimate of the desorption temperature.
Authors: M. Angiolini, G. Mazzone, Amelia Montone, Marco Vittori Antisari
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