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The spectrum of collective excitations of liquid deuterium in the bulk and confined within a MCM-41 matrix having pores of an average diameter of 2.4 nm has been studied by means of neutron scattering and molecular dynamics simulations. The main effects of confining liquid D2consist in a shift of the characteristic frequencies associated with damped density oscillations to higher energies. A strong decrease in diffusivity is also observed upon confinement.

Zeolites featuring basic sites have displayed outstanding performance in the valorisation of biobased substrates through condensation and coupling reactions. Herein, we present the continuous-flow, gas-phase dehydrogenation of ethanol to acetaldehyde as a novel application of the recently developed alkali-activated high-silica USY zeolites. Evaluation of the hydroxides of Group 1 metals in the catalyst preparation by alkaline treatment identified sodium hydroxide as the most suitable base. This is due to the stronger character and the higher number of mildly basic sites formed coupled with the minimal impact on the pristine porous properties of the zeolite, which resulted in superior catalytic performance. Compared to existing basic catalysts such as MgO and hydroxyapatites, no C4-condensation products were observed and the occurrence of ethanol dehydration to ethylene was marginal due to the negligible acidity of the material. At the optimal reaction temperature, acetaldehyde was attained with a ca.15-fold higher yield (50%) and with high selectivity (80%) when adding oxygen to the ethanol feed. The origin of this peculiar positive behaviour was unraveled through kinetic and in situinfrared spectroscopic studies as well as by the temperature-programmed surface reaction of ethanol. These investigations revealed the exclusive presence of ethoxide species at the catalyst surface, which (i) are formed upon adsorption of ethanol at basic siloxy groups, (ii) are stabilised through hydrogen bonding with vicinal silanols and (iii) react in a rate-limiting step with gas-phase oxygen through an Eley–Rideal mechanism to form acetaldehyde, thus releasing water. In contrast to the rapid deactivation shown by noble metal based catalysts, the material exhibited stable performance over 24 h on stream.

Abstract.: The spectrum of collective excitations of liquid deuterium in the bulk and confined within a MCM-41 matrix having pores of an average diameter of 2.4 nm has been studied by means of neutron scattering and molecular dynamics simulations. The main effects of confining liquid D2 consist in a shift of the characteristic frequencies associated with damped density oscillations to higher energies. A strong decrease in diffusivity is also observed upon confinement.

The crystal and magnetic structures of (Pr0.55Ca0.45)(Mn1-yCry)O3 (y = 0.00, 0.03, 0.06) have been investigated between 5 and 300 K by means of neutron powder diffraction followed by Rietveld refinement and dc magnetic measurements. An orthorhombic-to-monoclinic phase transition occurs on cooling in (Pr0.55Ca0.45)MnO3; at lower temperature charge ordering in the Mn sub-lattice, coupled with orbital ordering, induces an anti-ferromagnetic (AFM) spin ordering within the monoclinic phase. Cr substitution at the Mn site hinders the phase transition, although for the y = 0.03 sample small amounts of the monoclinic phase co-exist at low temperature with the main phase characterized by an orthorhombic structure. In addition Cr favours ferromagnetism (FM) participating to the double exchange mechanism. Cr substitution prevents charge ordering, favouring double exchange and hence FM spin ordering within the Mn sub-lattice. The Curie temperature of the Cr substituted samples is independent on the Cr content.

The crystal and magnetic structures of (Pr0.55Ca0.45)(Mn1-yCry)O3 (y = 0.00, 0.03, 0.06) have been investigated between 5 and 300 K by means of neutron powder diffraction followed by Rietveld refinement and dc magnetic measurements. An orthorhombic-to-monoclinic phase transition occurs on cooling in (Pr0.55Ca0.45)MnO3; at lower temperature charge ordering in the Mn sub-lattice, coupled with orbital ordering, induces an anti-ferromagnetic (AFM) spin ordering within the monoclinic phase. Cr substitution at the Mn site hinders the phase transition, although for the y = 0.03 sample small amounts of the monoclinic phase co-exist at low temperature with the main phase characterized by an orthorhombic structure. In addition Cr favours ferromagnetism (FM) participating to the double exchange mechanism. Cr substitution prevents charge ordering, favouring double exchange and hence FM spin ordering within the Mn sub-lattice. The Curie temperature of the Cr substituted samples is independent on the Cr content.

Neutron intensity elastic scans on trehalose, maltose, and sucrose/H2O mixtures as a function of concentration, temperature, and exchanged wave vector are presented. The experimental findings show a crossover in molecular fluctuations between harmonic and anharmonic dynamical regimes. A new operative definition for the degree of fragility of glass-forming systems is furnished by using explicitly the connection between viscosity and mean-square displacement. The procedure is tested for the investigated mixtures and for a set of glass-forming systems. In this frame, the stronger character of trehalose/H2O mixture indicates a better attitude in respect to maltose and sucrose/H2O mixtures to encapsulate biostructures in a more rigid matrix.

In this work results on glass-forming systems, i.e. homologues disaccharides (trehalose, maltose, sucrose)/H₂O mixtures obtained by using elastic incoherent neutron scattering are shown. The different degree of “strength” of the investigated systems, highlighted by the results, has been quantitatively characterized by using a new operative definition of “fragility”. The connection between the fragility degree and the cryptoprotection degree is also discussed.

In this work results on glass-forming systems, i.e.homologues disaccharides trehalose, maltose, sucroseH2O mixtures obtained by using elastic incoherent neutron scattering are shown. The different degree of “strength” of the investigated systems, highlighted by the results, has been quantitatively characterized by using a new operative definition of “fragility”. The connection between the fragility degree and the cryptoprotection degree is also discussed.

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In this work a route for BaZrO3synthesis that assures homogeneity and stoichiometry of the final powder is proposed. The route consists in the complexation of the metallic ions by citric acid and ammonia in an aqueous solution. After an accurate drying of the initial solution, the crystalline phase of barium zirconate is obtained at relatively low temperature (about 700°C) and in relative short times utilising cheap starting reagents. A detailed description of the different steps of a preparation of 300 g of final product and a comparison with BaZrO3powders produced by a typical solid state reaction are reported. The powders are characterised during the various steps by thermal analysis (DTA-TGA) and by structural and morphological techniques (XRD, FTIR and granulometric measurements). A preliminary investigation of the sintering process is reported: SEM imaging and dilatometric measurements were performed to evaluate different sintering behaviours of the powders prepared by wet and solid state methods.