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General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Echange d'ions, Ion-exchange, Zéolites: préparations et propriétés, Zeolites: preparations and properties, Croissance cristalline, Crystal growth, Crecimiento cristalino, Germination hétérogène, Heterogeneous nucleation, Germinación heterogénea, Nucléation, Nucleation, Nucleación, Synthèse, Synthesis, Síntesis, Tamis moléculaire, Molecular sieve, Tamiz molecular, Zéolite, Zeolite, Zeolita, Agent structurant, and Template

The addition of Mg2+ cations to the synthesis medium of zeolite L favours the zeolite nucleation in the same way as Ag+, an heterogeneous nucleation agent, but slows down crystal growth in the same way as other alkaline earth cations. Comparison with the synthesis of zeolite Y indicates that the promotion of nucleation by Mg2+ is related to the presence of K+ in the synthesis system of zeolite L.

General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Photoémission, Photoemission, Résolution angulaire, Angular resolution, Spectrométrie photoélectron, Photoelectron spectroscopy, Surface Fermi, Fermi surface, Tomographie, Tomography, Angle-resolved photoemission, and Be(0001)

When mapping spatially resolved photoemission intensity for electron kinetic energy corresponding to Fermi energy, one obtains a spherical cut through a three-dimensional Fermi surface of a metal. At the APE-INFM beamline at Elettra, we developed an automated method of measuring the Fermi surface cuts for a large number of photon energies and putting them together in order to reconstruct the three-dimensional Fermi surface. The energy and k∥ (momentum parallel to the surface) resolution are set by the monochromator and energy analyzer properties, while the k⊥ (momentum perpendicular to the surface) resolution depends on the photon energy step chosen for obtaining subsequent data sets. By 3D interpolation of the data, one obtains the k-space tomography of the constant initial state surfaces (e.g. of the Fermi surface). From the tomography, one can retrieve true kx, ky, kz resolved maps. Besides de Haas van Alphen (dHvA) oscillations, this method is the most direct way for the determination of the Fermi surfaces. A set of data on the Fermi surface of Be(0001) is presented and compared to dHvA data and theory.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Alliage base cuivre, Copper base alloys, Effet physique rayonnement, Physical radiation effects, Rayonnement laser, Laser radiation, Spectrométrie laser, Laser spectroscopy, Spectrométrie optique, Optical spectrometry, Espectrometría óptica, Spectrométrie émission, Emission spectroscopy, 82.80.Dx; 39.30.+w; 79.20.Ds; 32.30.Jc; 78.47.+p, and Self-calibrated LIBS; Copper-based-alloys analysis; Laser induced optical emission spectroscopy; fs-LIBS; ns-LIBS

A self-calibrated analytical technique, based on plasmas induced by either 250 fs or 7 ns laser pulses, is presented. This approach is comparable to other calibration-free methods based on LTE assumption. In order to apply this method to very different laser pulse durations, the partial-local thermodynamic equilibrium (p-LTE) has been considered within the energy range of 30,000-50,000 cm-1. In order to obtain the neutral species densities, the detected plasma species emission lines intensities have been treated together with the experimental evaluated background black-body Planck-like emission distribution. For validating the followed method, three certified copper-based-alloys standards were employed and their minor components (Ni, Pb and Sn) amounts were determined. As a result, it arises, that this standardless method, independently from the laser source pulse durations, provides good quantitative analysis, and, consequently, that the composition of the plasma plume emitting species induced is not affected by the laser pulse time width.

General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Composé minéral, Inorganic compounds, Métal transition composé, Transition element compounds, Nanoparticule, Nanoparticles, Zinc oxyde, Zinc oxides, O Zn, ZnO, Mechanochemical, UV-vis spectrophotometer, and ZnO nanoparticles

Crystalline ZnO nanoparticles were synthesized by mechanochemical method. Mechanochemical processing involves the mechanical activation of solid-state displacement reactions at low temperatures in a ball mill. Statistical design was used to investigate the effect of main parameters (i.e. time, milling rate and calcination temperature) on ZnO crystallite size and morphology. After annealing at 400 °C in air, zinc oxide (ZnO) nanoparticles were obtained. The milled powders are analyzed by X-ray diffraction (XRD), TG/DTA and transmission electron microscope (TEM). The crystallite size of ZnO samples calculated from XRD is consistent with the TEM images and estimated to be less than 20 nm. The optical properties of the samples were studied by UV-vis spectrophotometer.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Transformation des combustibles. Carbochimie et pétrochimie, Fuel processing. Carbochemistry and petrochemistry, Acidité, Acidity, Acidez, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur sur support, Supported catalyst, Catalizador sobre soporte, Gas oil, Gasóleo, Hydrotraitement, Hydrotreating, Hidrotratamiento, Matériau composite, Composite material, Material compuesto, Métal transition composé, Transition element compounds, Pétrole lourd, Heavy oil, Petróleo pesado, Silice, Silica, Sílice, Support, Soporte, Titane oxyde, Titanium oxide, Titanio óxido, Valorisation, Upgrading, Valorización, Catalyst, Coker gas oil, and Composite support

Y/composite titania-silica (CTS) support was prepared by the in situ growth of CTS on HY zeolite. The effects of HY zeolite pretreatment and Y/CTS modification with P and F for adjusting the acidity of the support were studied. The results showed that the structure of Y/CTS was in the form of CTS as shell and HY zeolite particles as core. The content of HY zeolite affected the acidity, acidity distribution and pore structure of Y/CTS. The density of strong acid sites on the HY zeolite surface could be partly reduced by dealumination with citric acid. This reduced the CTS coverage on the outer surface of the HY zeolite, leading to the increased acidity of Y/CTS. The acidity distribution of the support could also be adjusted by P and F modification. Hydrotreating catalysts were prepared with Y/CTS as support. The catalysts were tested using the hydrotreating reaction of a coker gas oil (CGO). The experimental results showed that the catalyst hydrodenitrogenation (HDN) performance could be remarkably improved by adjusting the acidity of the catalyst support via HY zeolite pretreatment and P and F modification. The catalysts with proper Bronsted (B) acidity and Lewis (L) acidity behaved well in hydrodesulfurization (HDS) and HDN performances.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Absorption RX, X ray absorption, Absorción RX, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Fonctionnelle densité, Density functional, Funciónal densidad, Molybdène oxyde, Molybdenum oxide, Molibdeno óxido, Métal transition composé, Transition element compounds, Oxygène, Oxygen, Oxígeno, Rayon X, X ray, Rayos X, Théorie fonctionnelle, Functional theory, Teoría funcional, Density functional theory, MoO3, and X-ray absorption

The identification of oxygen sites at metal oxide surfaces and the characterization of their properties is of great importance for an understanding of the catalytic activity of such materials and, thus, for a rational design of efficient and selective catalysts. In the case of the clean MoO3(0 1 0) surface we show that an unambiguous discrimination of the different reactive oxygen sites can be obtained by angle-resolved near-edge X-ray absorption fine structure (NEXAFS) combined with density functional theory (DFT) based spectrum analyses for different photon polarization directions. In particular, we are able to unequivocally discriminate the characteristic spectral signatures of singly coordinated molybdenyl oxygen covering the topmost molybdenum layers from those of other oxygen centers that have very similar local environment and only differ by their spatial orientation in the crystal. Theoretical predictions are also successfully used to identify and interpret characteristic features in the NEXAFS spectra that arise from specific vacancy sites present at oxygen deficient surfaces.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Alcanol, Alkanol, Alcool, Alcohol, Activation, Activación, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Cobalt oxyde, Cobalt oxide, Cobalto óxido, Diffraction RX, X ray diffraction, Difracción RX, Ethanol, Etanol, Hydrogène, Hydrogen, Hidrógeno, In situ, Reformage vapeur, Steam reforming, Reformación vapor, Spectrométrie, Spectrometry, Espectrometría, Operando, Cobalt oxides, Ethanol steam-reforming, Hydrogen production, In situ techniques, and Operando X-ray diffraction

The evolution of Co3O4 during ethanol steam-reforming was investigated under operando conditions by using XRD measurements. The study was carried out at atmospheric pressure as a function of reaction temperature, flowing a 1/6 ethanol/water mixture. XRD measurements and catalytic evaluation were simultaneously accomplished using a reactor-cell specially designed for these purposes. Up to 548 K, only the presence of Co3O4 crystalline phase was determined, and under these conditions ethanol was dehydrogenated to acetaldehyde. At higher temperatures, Co3O4 reduced to crystalline CoO and small metallic cobalt particles. Simultaneously, the material became active for the ethanol steam-reforming reaction. At 623 K, the material which showed by XRD the presence of both CoO and Co phases, was very selective in the steam-reforming of ethanol.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Combustibles de remplacement. Production et utilisation, Alternative fuels. Production and utilization, Hydrogène, Hydrogen, Bore nitrure, Boron nitride, Boro nitruro, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Etude théorique, Theoretical study, Estudio teórico, Hydrogène, Hydrogen, Hidrógeno, Nanotube carbone, Carbon nanotubes, Physisorption, Fisisorción, Stockage, Storage, Almacenamiento, Ab initio, BN nanotubes, and Hydrogen storage

Using ab initio calculations we investigated the hydrogen storage in single-walled boron nitride nanotubes. We present the nature of hydrogen interaction in selected sites of a (5,5) and (9,9) BN nanotube. Our results show that BN nanotubes are preferable to carbon nanotubes for hydrogen storage applications due to their heteropolar binding nature of their atoms. In addition, by increasing the nanotube's diameter - decreasing its curvature, more efficient binding energies of hydrogen can be achieved.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Physicochimie de surface, Surface physical chemistry, Echange d'ions, Ion-exchange, Zéolites: préparations et propriétés, Zeolites: preparations and properties, Argile à piliers, Pillared clay, Arcilla con pilares, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur, Catalyst, Catalizador, Eau usée, Waste water, Agua residual, Huile, Oil, Aceite, Hydrogène peroxyde, Hydrogen peroxide, Peróxido de hydrogeno, Oxydation, Oxidation, Oxidación, Réaction catalytique, Catalytic reaction, Reacción catalítica, Tamis moléculaire, Molecular sieve, Tamiz molecular, Zéolite, Zeolite, Zeolita, Biodegradable COD, Cu-zeolite and Cu-pillared clay catalysts, OOMW, and WHPCO

The use of catalysts to improve the performances of water treatment technologies is well known; in the last years more scientific attention was given to the treatment of the olive oil mill wastewaters. This problem affects especially the Mediterranean area because this region is the largest world olive oil producer. In this paper, the results of the wet hydrogen peroxide catalytic oxidation on olive oil mill wastewaters using Fenton-like type catalysts (Cu-Silicalite-1 and Cu-pillared clay) are presented. Both the catalysts showed a high conversion in the oxidation of poly-phenols and were able to drastically reduce the chemical oxygen demand, the biochemical oxygen demand and the non-biodegradability of the olive oil mill wastewaters.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Science des matériaux, Materials science, Nanomatériaux et nanostructures : fabrication et caractèrisation, Nanoscale materials and structures: fabrication and characterization, Divers, Other topics in nanoscale materials and structures, Méthodes de nanofabrication, Methods of nanofabrication, Formation de nanomotifs, Nanoscale pattern formation, Catalyse, Catalysis, Couche tampon, Buffer layer, Capa tampón, Croissance film, Film growth, Echelle nanométrique, Nanometer scale, Formation motif, Patterning, Lithographie, Lithography, Méthode ablation laser, Laser ablation technique, Nanomatériau, Nanostructured materials, Stabilité structurale, Structure stability, Estabilidad estructural, Stabilité thermique, Thermal stability, Film laser-patterning, and Metallic nano-clusters

Growth of metallic nano-clusters and control over their size are critically important for catalysis. Development of film patterning procedures at the nanometer scale has significant impact on future lithography. In this work, we present an approach to grow metallic nano-clusters and control their size using a weakly bound buffer layer as an intermediate substance and a template to control the clusters size at the range 1-15 nm. The buffer layer was further employed to create a pattern based on a selective laser ablation procedure. A thicker metallic film deposited on top of pre-pattemed buffer layer has been demonstrated as a novel patterning technique at the sub-micron to nanometer scale employing a single laser pulse. The thermal stability of metallic structures prepared this way has been studied at temperature up to 1000 K.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Guide onde optique, Optical waveguides, Guide onde, Waveguides, Lithium niobate, Lithium niobates, Usinage, Machining, and Femtosecond laser machining

We report on investigations of the bulk microstructuring of lithium niobate crystals with intense femtosecond laser pulses. In different crystal cuts, optical waveguides were produced whose properties depend strongly on the processing parameters. To explore the origin of the refractive index changes, we subjected the crystals to different conditions (like temperature, illumination, etc.) while monitoring the waveguide output. This way several mechanisms for the change in refractive index could be singled out. These include the photorefractive effect, inhomogeneous ion concentrations and stress in the crystalline lattice. As an application, we demonstrate frequency doubling of 1064 nm laser radiation in a microstructured phase-matched waveguide.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Chemical engineering, Génie chimique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Théorie des réactions, cinétique générale. Catalyse. Nomenclature, documentation chimique, informatique chimique, Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry, Catalyse, Catalysis, Sciences appliquees, Applied sciences, Genie chimique, Chemical engineering, Réacteurs, Reactors, Alumine, Alumina, Alúmina, Catalyse hétérogène, Heterogeneous catalysis, Catálisis heterogénea, Catalyseur, Catalyst, Catalizador, Dépôt, Deposition, Depósito, Microréacteur, Microreactor, Microstructure, Microestructura, Optimisation, Optimization, Optimización, Reformage vapeur, Steam reforming, Reformación vapor, Réacteur catalytique, Catalytic reactor, Reactor catalítico, Alumina wash-coating, Catalyst deposition, Micro-reactors, and Micro-structured reactors

Thick and porous aluminum oxide coatings on the inner walls of a microchannel reactor have been developed as a support for catalytically active metals serving for on-board hydrogen production. These coatings must withstand extremely severe conditions in terms of temperature and mechanical shock. The developed suspension coating method uses alumina prepared from commercial powders. Optimizing the slurry preparation parameters such as particle size, viscosity, solid loading and/or binder content in tight relationship with coating properties allowed us to attain films at a desired thickness of 25 μm, with a good adhesion and reasonable uniformity. An ongoing investigation in our laboratory confirms that these coatings impregnated with an active phase can be successfully employed for hydrogen production by steam reforming of isooctane.

General chemistry, physical chemistry, Chimie générale, chimie physique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Thermodynamique chimique, Chemical thermodynamics, Propriétés thermodynamiques, Thermodynamic properties, Mélanges, Mixtures, Alcaloïde, Alkaloid, Alcaloide, Alcool secondaire, Secondary alcohol, Alcohol secundario, Boldine, Densité, Density, Densidad, Estimation, Estimación, Grandeur molaire partielle, Partial molar quantity, Tamaño molar parcial, Mélange, Mixture, Mezcla, Phénols, Phenols, Fenoles, Pression atmosphérique, Atmospheric pressure, Presión atmosférica, Propriété physique, Physical properties, Propiedad física, Propriété thermodynamique, Thermodynamic properties, Propiedad termodinámica, Système binaire, Binary system, Sistema binario, Volume molaire, Molar volume, Volumen molar, Aporphine dérivé, Dibenzo[de,g]quinoléinium composé, Propan-2-ol, Estimation of solid density, Isopropanol, New method, Partial molar volume, and n-Alcohols

Densities of boldine + alcohol binary mixtures were measured over the whole accessible range of boldine compositions at temperatures from 283.15 to 333.15 K using an Anton-Paar digital vibrating glass tube densimeter. The binary systems studied include, as a solvent, seven normal alcohols from n-C1 to n-C6, n-C8, and isopropanol. The density of these systems has been found an increasing function of the boldine composition. A new methodology based on density data of solutions of solid solutes with normal alcohols is described in order to determine solid molar volume of pure solutes. This methodology was validated with pure solid naphthalene molar volumes data at 298.15 K, with an average uncertainty of 6%.

General chemistry, physical chemistry, Chimie générale, chimie physique, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Equilibres de phases, Phase equilibria, Equilibres liquide-vapeur, Liquid-vapor equilibria, Acétique acide ester méthyle, Methyl acetate, Carbone dioxyde, Carbon dioxide, Carbono dióxido, Densité, Density, Densidad, Equilibre liquide vapeur, Liquid vapor equilibrium, Equilibrio líquido vapor, Equilibre phase, Phase equilibrium, Equilibrio fase, Mélange, Mixture, Mezcla, Propriété physique, Physical properties, Propiedad física, Relation PVT, PVT relation, Relación PVT, Data, and PVT

Volumetric properties were measured for carbon dioxide + methyl acetate system at 313.15 K and pressures to 10 MPa, using the vibrating tube Anton Paar DMA 512P density meter. In the present experiments, no analytical instrument is required. The saturated pressure was further measured for carbon dioxide + methyl acetate system at 313.15 K by the synthetic method. The experimental volumetric data obtained were correlated with the modified Tait equation.

General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Courant photoélectrique, Photocurrents, Diffusion Raman, Raman scattering, Difusión Ramán, Nanotube carbone, Carbon nanotubes, Rayonnement UV proche, Near ultraviolet radiation, Spectre Raman, Raman spectra, Spectrométrie perte énergie électron, EEL spectroscopy, Electron energy loss spectroscopy (EELS), Photocurrent measurements, and Raman scattering spectroscopy

Multiwall carbon nanotubes are found to generate photocurrent in the visible and near ultra violet spectral range using a photoelectrochemical technique. Peaks in the photocurrent are observed at excitation energies in the visible region. Their electron energy loss spectra exhibit the n plasmon feature, typical of graphite layers, and a peak at lower energy. Features at energies between 0 and 4 eV have been already observed for single wall carbon nanotubes and ascribed to interband electronic transitions due to the reduced dimensionality of these systems. The present measurements suggest that the usual identification of multiwall carbon nanotubes electronic density of states with that of graphite layers is not sufficient and more theoretical investigations are necessary to shed light on this point.

General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Faisceau moléculaire, Molecular beams, Oxygène, Oxygen, Spectre photoélectron RX, X-ray photoelectron spectra, O, High resolution XPS, Ru(0001), Supersonic molecular beam, and Vibrational excitation

Supersonic molecular beam technique combined with high resolution X-ray photoelectron spectroscopy using synchrotron radiation was applied to the study of the dynamics of dissociative adsorption of oxygen on Ru(0001) surface in high coverage region. The Ru(0001) surface pre-covered with oxygen atoms of 0.5 monolayer, which corresponds to the p(2 x 1)-O structure, was dosed to oxygen molecules with translational energy of 0.5 eV. Oxygen uptake was compared between the cases with and without the beam source heated in order to verify the effects of internal energy of oxygen. We found drastic enhancement in initial sticking probability of oxygen when the beam source was heated to 1400 K. We concluded that the enhancement of sticking probability is mainly caused by molecular vibrational excitation, indicating that dissociation barrier is located in the exit channel on potential energy surface.

General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Matériau poreux, Porous materials, Silicium, Silicon, Spectre IR, Infrared spectra, Spectre absorption, Absorption spectra, Si, Infrared absorption spectroscopy, Molecular grafting, Porous silicon, and Styrene

A new semi-quantitative method providing the relative efficiency of three different organic functionalization reactions onto porous silicon has been set up, based on infrared absorption data. Compared to previously reported techniques, it enables a direct titration of the grafted molecules. We demonstrated that grafting of Si-styrenyl moieties by ethylaluminium dichloride mediated hydrosilylation of phenylacetylene leads to higher yields than organometallic addition onto either hydrogenated or brominated silicon.

General chemistry, physical chemistry, Chimie générale, chimie physique, Metallurgy, welding, Métallurgie, soudage, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Equations d'état, équilibres de phases et transformations de phases, Equations of state, phase equilibria, and phase transitions, Divers, Other topics in equations of state, phase equilibria, and phase transitions, Amorphisation, Amorphization, Capacité calorifique, Heat capacity, Capacidad calorífica, Condition opératoire, Operating conditions, Condición operatoria, Conductivité thermique, Thermal conductivity, Diagramme phase, Phase diagrams, Eau, Water, Effet pression, Pressure effects, Effet température, Temperature effects, Equilibre phase, Phase equilibria, Etat amorphe, Amorphous state, Etat cristallin, Crystalline state, Etat vitreux, Vitreous state, Glace, Ice, Mécanisme réaction, Reaction mechanism, Mecanismo reacción, Propriété thermique, Thermal properties, Relaxation diélectrique, Dielectric relaxation, Relaxation, Thermodynamique, Thermodynamics, Amorphization mechanism, Amorphous solid and glassy water, and Ices

Pure water forms 15 crystalline ices at different temperatures and pressures, and its solutions containing small molecules form three crystallographically distinct clathrates. Its vapours deposited on a substrate at T< 100K produce a porous amorphous solid and pure water vitrifies (Tg = 136 K) when hyperquenched in micron-size droplets. At a temperature below 140 K, hexagonal and cubic ice collapse when pressure exceeds ∼1 GPa to a ∼30% denser amorphous solid, which on heating at ambient pressure transforms to an amorphous solid with density similar to that of hexagonal ice. In this essay, we describe (i) the thermal conductivity of the ices and clathrates and the thermal conductivity and heat capacity of water's amorphous solids, their thermodynamic paths and their transformations, and (ii) the dielectric relaxation time of ultraviscous water formed on heating the amorphous solids. We also describe the characteristics of pressure collapse and subsequent amorphization of hexagonal and cubic ices that occurs over a period of several days according to a stretched exponential kinetics and a pressure-, and temperature-dependent rate constant. This process is attributed to the production of lattice faults during deformation of the ice and the consequent distribution of the Bom instability pressures. This ultimately produces a kinetically unstable high-energy amorphs in the same manner as random deformation of crystals produces kinetically unstable high-energy amorphs, with density and properties depending upon their temperature-pressure-time history. On heating at 1 GPa pressure, the pressure-amorphized solid relaxes to a lower energy state, becoming ultraviscous water at 140 K. But on heating at ambient pressure, it irreversibly transforms slowly to a low-density amorph that differs from glassy water and vapour-deposited amorphous solid.

General chemistry, physical chemistry, Chimie générale, chimie physique, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Polymers, paint and wood industries, Polymères, industries des peintures et bois, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure, proprietes mecaniques et thermiques, Condensed matter: structure, mechanical and thermal properties, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Domaines interdisciplinaires: science des materiaux; rheologie, Cross-disciplinary physics: materials science; rheology, Frottement, Friction, Nanotube carbone, Carbon nanotubes, Atomic scale friction, and Phonons in nanoscale material

The friction between concentric carbon nanotubes sliding one inside the other has been widely studied and simulated, but not so far using external force as the driving variable. Our molecular dynamics (MD) simulations show that as the pulling force grows, the sliding velocity increases by jumps and plateaus rather than continuously as expected. Dramatic friction peaks [similar to that recently noted by P. Tangney, M.L. Cohen, S.G. Louie, Phys. Rev. Lett. 97 (2006) 195901] which develop around some preferential sliding velocities, are at the origin of this phenomenon. The (stable) rising edge of the peak produces a velocity plateau; the (unstable) dropping edge produces a jump to the nearest stable branch. The outcome is reminiscent of conduction in ionized gases, the plateau corresponding to a current stabilization against voltage variations, the jump corresponding to a discharge or breakdown.

General chemistry, physical chemistry, Chimie générale, chimie physique, Crystallography, Cristallographie cristallogenèse, Nanotechnologies, nanostructures, nanoobjects, Nanotechnologies, nanostructures, nanoobjets, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Physique, Physics, Etat condense: structure electronique, proprietes electriques, magnetiques et optiques, Condensed matter: electronic structure, electrical, magnetic, and optical properties, Emissions électronique et ionique; phénomènes d'impact, Electron and ion emission by liquids and solids; impact phenomena, Photoémission et spectres photoélectroniques, Photoemission and photoelectron spectra, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Généralités, appareillage, General, apparatus, Surface and interface chemistry, Catalyseur, Catalysts, Modélisation, Modelling, Phosphore oxyde, Phosphorus oxides, Réacteur membrane, Membrane reactor, Reactor membrana, Spectre photoélectron RX, X-ray photoelectron spectra, Valence, Vanadium oxyde, Vanadium oxides, Vanadium, V, 79.60.-i; 82.47.-a; 82.65.-s; 82.65.+r; 82.80.Pv, and VPO catalysts; Electrochemical membrane reactor; XPS; Modelling

Recently, the feasibility of butane oxidation in an electrochemical membrane reactor (EMR) using a vanadium phosphorus oxide (VPO) catalyst layer on a tubular anodic electrode has been reported. This novel application of EMR gives rise to questions about the vanadium oxidation state (Vox) under working conditions and about its spatial distribution in the catalyst layer. It has now been determined by means of position-resolved XPS measurements. In addition, model calculations on the spatial Voxdistribution have been performed for the first time. The simulations reveal a non-uniform 3D distribution of Vox due to the relative rate of reduction and re-oxidation processes in the catalyst layer, in good agreement with the experimental XPS data.