We report the extensive investigation of Li and H dynamics in Li6C60 and Li6C60Hy, by combining Li-7 and H-7 solid state NMR measurements with DC/AC conductivity, in order to evaluate the potential application. of these systems for energy-storage purposes. Li-7 NMR results show a local motion of Li ions above 200 K in both pristine and hydrogenated compounds, with activation energies of 90-150 meV and correlation times of about 30 ps. Evidences of Li interdiffusive dynamics are given by conductivity measurements in Li6C60 already above 120 K, with activation energies of 240 meV, suggesting that ionic conductivity is of the order of 10(-5) S cm(-1) at room temperature, with correlation times of about 150 ps. On the other hand, the Li6C60Hy behaves like a semiconductor with a high energy gap (ca. 2.5 eV), suggesting that diffusion of intercalated Li ions is prevented. H-1 NMR measurements indicate the absence of H motions for the whole temperature range investigated (up to 360 K), neither on macroscopic or local scale. Li6C60 good properties for H-2-storage are confirmed in terms of absorption capacity (5 wt% H-2), moreover we found that around 35% of lithium segregates in LiH form, leaving Li4C60H40 as the final hydrogenation product (C) 2015 Elsevier Ltd. All rights reserved.

New insights into the reaction pathways of different potassium/magnesium amide-hydride based systems are discussed. In situ SR-PXD experiments were for the first time performed in order to reveal the evolution of the phases connected with the hydrogen releasing processes. Evidence of a new K-N-H intermediate is shown and discussed with particular focus on structural modification. Based on these results, a new reaction mechanism of amide-hydride anionic exchange is proposed.

The mechanism of Bi4Ti3O12 formation starting from the two constituent oxides has been studied. Starting from a physical mixture, a solid-state reaction occurs between the two oxides that leads at ≈700 °C to a mixture of the two ternary oxides Bi12TiO20 + Bi4Ti3O12 along with unreacted precursor oxides. At T ≈ 830 °C Bi12TiO20 reacts with TiO2 forming Bi4Ti3O12 and, finally, at T ≈ 850 °C, the residual Bi12TiO20 undergoes the peritectic reaction that produces Bi4Ti3O12 plus a liquid phase. However, the formation of Bi4Ti3O12 is not complete at temperatures as high as 900 °C. Starting from a mechanically activated mixture, the intermediate Bi12TiO20 only forms as a minority phase at a lower temperature (T ≈ 550 °C), and then it rapidly reacts to give Bi4Ti3O12. No trace of the peritectic reaction is found in the case of the activated mixture. The complete formation of Bi4Ti3O12 can be obtained by 3-h annealing of the activated mixture at T ≥ 650 °C. The heat capacity of the product phase Bi4Ti3O12 has also been measured in the temperature range 50–300 °C.

In the present work we focus the attention on the phase structural transformations occurring upon the desorption process of the LiBH4 + LiAlH4 system. This study is conducted by means of manometric-calorimetric, in situ Synchrotron Radiation Powder X-ray Diffraction (SR-PXD) and ex situ Solid State Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) measurements. The desorption reaction is characterized by two main dehydrogenation steps starting at 320 and 380 degrees C, respectively. The first step corresponds to the decomposition of LiAlH4 into Al and H-2 via the formation of Li3AlH6 whereas the second one refers to the dehydrogenation of LiBH4 (molten state). In the range 328-380 degrees C, the molten LiBH4 reacts with metallic Al releasing hydrogen and forming an unidentified phase which appears to be an important intermediate for the desorption mechanism of LiBH4-Al-based systems. Interestingly, NMR studies indicate that the unknown intermediate is stable up to 400 degrees C and it is mainly composed of Li, B, Al and H. In addition, the NMR measurements of the annealed powders (400 degrees C) confirm that the desorption reaction of the LiBH4 + Al system proceeds via an amorphous boron compound. (C) 2013 Elsevier B.V. All rights reserved.

In this work we focused on nanoconfinement of NaBH4 into highly-ordered Si-based mesoporous scaffold and its carbon replica by ammonia-free wet chemical impregnation. Structural and morphological characterization, performed by X-ray diffraction and transmission electron microscopy enabled us to confirm the effectiveness infiltration procedure. Desorption properties tested by temperature programmed desorption analyses highlighted a noticeable shift towards lower temperature compared to both bulk material and samples of similar systems referred to in the bibliographical data. (C) 2013 Elsevier B.V. All rights reserved.

The present investigation focuses on a new synthesis route of NaBH4 starting from the 2NaH + MgB2 system subjected to mechanochemical activation under reactive hydrogen atmosphere. The milling process was carried out under two different hydrogen pressures (1 and 120 bar) with two different rotation speeds (300 and 550 rpm). The reaction products were characterized by ex-situ solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR), ex-situ X-ray powder diffraction (XRPD) and Infrared Spectroscopy (IR). From the results of these analyses, it can be concluded that milling in all the considered conditions led to the formation of NaBH4 (cubic-Fm-3m). In particular, a reaction yield of 5 and 14 wt% is obtained after 20 h of milling at 120 bar of H-2 for the tests performed at 300 rpm and 550 rpm, respectively. The presence of MgH2 is also detected among the final products on the as milled powders. The influence of the milling conditions and the evaluation of the parameters related the mechanochemical process are here discussed. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

A thermoanalytical (TGA/DSC) and diffractometric (XRD) study has been performed on the solid state reaction system L i 2 C 0 3 F e 2 0 3 in the xLi range 0.10-^0.50. A detailed analysis of the results shows that the data are in agreement with a reaction model where the carbonate decomposition is regulated by the formation of both L i F e 0 2 and L i F e 5 0 8 , and the relative amount of the two phases depends on the initial composition. The DSC evidence offers the possibility to directly quantify the LiFe5Ox phase. Furthermore it allows one to obtain the enthalpies of formation of both L i F e 0 2 and L i F e 5 0 8 .

We focus on the H-2 desorption properties of the 2NaBH(4) + MgH2 system destabilized by different methods. Nanostructured powder mixtures were prepared by ball milling the starting hydrides and nanoconfined reactive composites were obtained by melting infiltration of the hydrides into a Si-based SBA-15 support. NbF5 was tested as catalyst in both the preparations.Structural characterization by X Ray Diffraction and Transmission Electron Microscopy allowed evaluating the successful synthesis of SBA15 matrix, the microstructural features of ball milled and nanoconfined hydrides as well as the success of infiltration process. The evaluation of the sorption properties, by manometric Sievert-type apparatus and thermal desorption spectroscopy, revealed the efficiency of the hydride destabilization, obtained by the different routes, in decreasing the hydrogen release temperature and improving desorption kinetics. (c) 2012 Elsevier B.V. All rights reserved.

It is well known that the control of the crystallization of drugs to ensure that only the approved and desired polymorph is present in the formulation is a crucial point of a preformulation study. In this regard, the aim of the present work is to devise a method for the quantification of the polymorphic purity of nateglinide in mixtures formed by polymorphs H and B. In order to achieve this goal, binary systems of known composition have been prepared and the melting peaks of both polymorphs have been recorded by differential scanning calorimetry. Experiments have determined that the method of preparation of the mixtures has to be carefully evaluated. Indeed it has been shown that grinding the samples induces transition from B to H form. Furthermore, it could be observed that the enrichment of the binary mixture with H form is caused by heating. Therefore, after having prepared the mixture without grinding stage, we propose a method to evaluate the content of H polymorph in mixture with the B one from the melting peak of B.

The sorption properties of NaBH4/MH2 (M=Mg, Ti) powder systems prepared by high-energy ball milling have been thoroughly investigated. Concerning the systems containing MgH2, the 2:1 and 1:2 molar compositions have been studied and both lead to a multi-step desorption pathway, where the formation of MgB2 confirms the destabilization of NaBH4 induced by the presence of MgH2. A noticeable kinetic enhancement is achieved for the MgH2-rich system (composition 1:2) if compared with the NaBH4-rich system (composition 2:1). Even though full re-absorption is obtained for neither of the two compositions, fast kinetics is achieved. During absorption, the unsuspected formation of the perovskite-type hydride NaMgH3 is detected and it is showed that this ternary phase contributes to reduce the gravimetric capacity of the systems. Conversely, in the 2NaBH4/TiH2 system, there is no formation of the intermetallic compound TiB2. Furthermore, a decrease in the sorption kinetics is found in comparison with the systems based on MgH2.

Ternary Mg-Nb(2)O(5) - graphitic C mixtures (molar ratio % = 97.5:0.5:2.0) were prepared by high-energy ball milling (BM) under Ar for different times (from 0.25 h to 4 h) and thoroughly characterized by manometric, calorimetric, X-ray powder diffraction, and scanning electron microscopy analyses. The aims of the work were: - to assess the effect of the simultaneous presence of the two dopants on the reactivity and the sorption properties of the Mg-MgH(2) system; - to study the influence of the milling time on the performance of the mixtures.Neither milling nor the high temperature/high pressure treatments led to reactions among the components of the mixtures, and Mg was the only hydrogen active phase. After 4 activation cycles at 623 K and 35 bar/1 bar charging/discharging pressure, the mixture milled for 1 h was the best performing one: it reversibly charged up to 6.8 wt% H(2) with absorption/desorption rates 64/4.5 times higher than those of a pure Mg sample BM for the same time and activation energies 3.6/2 times lower. The desorption temperature and the dehydrogenation enthalpy of the ternary mixture were respectively 40 K and 4 kJ/mol H(2) lower than those of pure MgH(2). (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

Binary Mg–Ni mixtures and ternary Mg–Ni–C (graphite) samples with fixed proportions of metals (Mg 85%–Ni 15% by weight) and amount of C increasing in increments of 5 wt % from 5 wt % to 15 wt % were prepared by high energy ball milling (BM) in Ar for tBM=2h. The purpose of the study was to evaluate the effect of C addition on the reactivity, the sorption activation and the storage performance of the Mg–Ni system.

Mg-based ternary mixtures (40≤Mgwt%≤80) containing increasing amount (up to 30wt %) of Ni and Cu were prepared by ball milling (BM) under Ar for 16h and subsequently activated at high temperature (623K) by charging/discharging cycles at H2 pressure of 50bar/0.7bar. The work aims to analyze the influence of the mixtures' composition on the storage properties (H2 intake and sorption kinetics) and to describe the role played by an ad-hoc activation in reaching these same properties. The storage capacity of the mixtures decreases by decreasing the Mg starting content, the H2 active phases being “free Mg” and the “bonded Mg” intermetallic compounds Mg2Ni and Mg2Cu. After full activation (3 charging/discharging runs), “free Mg” hydrogenates 10 times quicker than the “bonded Mg phases”, while the discharging of both “free” and “bonded” Mg hydrides takes place simultaneously with similar kinetics. The best kinetic performance is shown by the samples with Mg=60wt% and 70wt% and the highest Ni content (30% and 20% respectively), with sorption rates up to 7 times higher than those of the pure Mg/MgH2 system.

New modifications of the antidiabetic drug nateglinide were found and characterized by means of thermal analysis, vibrational spectroscopy and X-ray powder diffractometry. In particular it has been verified that the product obtained during the final steps of the nateglinide synthesis is the hemihydrate form which melts at about 86 degrees C provided that the adopted experimental conditions hinder the removal of the crystallization water. Otherwise, if the crystallization water is removed, the hemihydrate transforms to a new anhydrous polymorph that melts at 102.8 degrees C. The anhydrous polymorph, if stored at room temperature and humidity, gradually changes to H polymorph while, if stored in water vapour saturated atmosphere, it gets back water and reverts to the hemihydrate form. On the contrary, both an isothermal treatment at 80 degrees C and melt cooling bring to the B polymorph.

The physico-chemical characterization of the polymorphs of nateglinide (named B, H and S), an antidiabetic agent, has been performed by means of thermal, diffractometric, spectroscopic and electron microscopic measurements. It has been established that S polymorph can crystallize from the melt obtained from both B and H samples or also following an isothermal treatment of both forms at temperatures lower than the relevant melting points. By X-ray diffraction it could be shown that the three polymorphs have different crystal structure. On the other hand the indication has been drawn from IR spectra that the molecular structure of B is sensibly different from those of H and S forms that have a very similar molecular structure. Finally, the microstructure features of the three polymorphs have been examined by scanning electron microscopy. Our analyses have allowed to evaluate the relative stability of the three polymorphs through the construction of the energy vs. temperature diagram. In particular, S polymorph, the highest-melting form, has resulted to be the only stable form, while the B and H forms are metastable.

In this work the solid-state characterization of anhydrous D -mannitol has been performed: α and β modifications can be distinguished only by XRPD and FTIR as they show melting temperature and enthalpy that are the same within the standard deviation. The understanding of the thermal behaviour of the δ form (obtained by re-crystallization in acetone) has required XRPD experiments performed at variable temperature. This form during heating undergoes a solid phase transition to α modification. By cooling a melted sample, under a wide range of experimental conditions, a very fast crystallization occurs. Independently of the starting crystal form (β or δ form), the re-crystallization of D -mannitol from melt always leads to α form.

The thermodynamic properties of a new antidepressant drug are studied from room temperature to 200 °C. In this range, the sample neither decompose, nor has a significant reactivity with water. When slowly heating a “fresh” sample, we may observe the following phenomena (in the order): melting of a form (F1, ~170 °C), crystallization of a structurally different form (F2), and melting of F2 (~180 °C). In no circumstances, the direct transition from F1 to F2 can be observed. On the other hand, F2 reverts to F1 upon cooling below ~130 °C. A glassy phase is formed upon cooling from above 180 °C, as confirmed by X-ray analysis and the appearance of a glass transition when reheating. The “reversible” (e.g., melting) and “irreversible” (e.g., glass formation) contributions to the measured enthalpies are estimated with temperature-modulated DSC measurements, resulting into a consistent description of thermodynamics of the forms, their melting and their kinetics of transformation.

The current research on solid state hydrogen storage materials for on-board applications is focused on reactive hydrides composites (RHC), i.e. systems based on the improvement of the dehydrogenation thermodynamic of a complex hydride when one (generally the light hydride MgH2) or more hydrides take part to the reaction. The extent of the destabilization, as well as the sorption characteristics of the composites, strongly depends on the structural and nanostructural properties of the constituent hydrides, which are in turn affected by the preparation route. The aim of this work is to evaluate the influence of different mechanical activation conditions on the storage properties of NaBH4-MgH2 composites, up to now scarcely explored in literature. The first results regard composites with 2:1 and 1:2 stoichiometry milled under different atmosphere (Ar or H-2). X-ray powders diffraction analysis shows that milling does not lead to the formation of any new phase, but it reduces the average crystallite size of the powders down to nanometric scale. All the mixtures release an H-2 amount close to the theoretical value expected for the full dissociation of both the hydrides and much higher than the target fixed by the US Department of Energy for on-board application. The thermal programmed desorption profiles of the mixtures clearly show two steps, with MgH2 dissociating first and with higher rate and NaBH4 gradually dehydrogenating at temperatures close to 400 degrees C. Concerning the 2:1 stoichiometry, when the samples are processed under Ar the two dehydrogenation processes are characterized by a lower starting temperature but also by a lower average rate with respect to the sample milled in H-2. The 1:2 sample milled under Ar shows the best kinetic performance. Unfortunately, also for this mixture more than 10 h are required to obtain full desorption at a temperature as high as 450 degrees C.

The sorption capacity and kinetics of mechanically activated binary mixtures of Mg with nine different metals (Al, Cu, Fe, Mn, Mo, Sn, Ti, Zn, Zr) have been studied to determine whether these metals act as catalyzing/destabilizing agents in formation/decomposition of Mg hydrides. Identification of crystalline phases before and after the absorption/desorption processes assists our understanding of the different behaviors displayed by the studied compounds. Cu, Al and Zn take active part in Mg hydrogenation/dehydrogenation, but only the addition of Cu is actually effective in MgH2 destabilization, leading to a substantial decrease of the desorption temperature of this phase (down to 270°C), and to an improved desorption kinetics. With the other metals, the hydrogen release usually occurs at a significant rate only above 320°C and the kinetics of the absorption/desorption processes are slower than in the Mg/MgH2 system.