Plasma-Enhanced Chemical Vapor Deposition of Silicon Carbonitride Films from Volatile Silyl Derivatives of 1,1-Dimethylhydrazine

Silicon carbonitride films were synthesized from new volatile precursors by plasma-enhanced chemical vapor deposition. Based on a detailed study of the morphology of film surfaces, it was found that the layer material was an amorphous matrix with inclusions of nanosized crystals. Calculation of the structure of the crystalline phase from synchrotron X-ray diffraction patterns demonstrated that the entire set of the diffraction peaks detected is indexed by a tetragonal structure with the lattice parameters a = 9.6 Å and c = 6.4 Å. This is consistent with the fact that the carbon 1s and nitrogen 1s core level X-ray photoelectron spectra exhibited only sp ³ bonding, which was expected for superhard carbon nitride phases.     

Structure of the Mo-Containing Dispersed Catalyst During Heavy Oil Upgrading in the Presence of Steam And Hydrogen

XRD, TEM, EXAFS/XANES methods are first used to study the structure and morphology of Mocontaining phases of carbon residues of heavy oil refining during catalytic steam cracking, catalytic cracking without water, and hydrocracking. According to the results obtained from physical and chemical studies of Mo-based catalytic phases, the reaction medium affects structural features of Mo-containing phases, e.g. the amount of oxide and sulphide forms, the particle size, and particle morphology.     

The Influence of Reaction Conditions on the Rate of Hydrogen Evolution in Aqueous Solutions of Glycerol over Pt/TiO2 Photocatalysts

Kinetics and Catalysis - The processes of photocatalytic hydrogen production from aqueous solutions of glycerol under soft UV radiation over photocatalysts based on platinized titanium dioxide were...     

Effect of the Ni/Cu ratio on the composition and catalytic properties of nickel-copper alloy in anisole hydrodeoxygenation

The activity of NiCu-SiO₂ catalysts with a metal content of 90% and different Ni/Cu ratios has been investigated in the hydrodeoxygenation of anisole, a model compound of bio-oil, at 280°C and 6 MPa. A homogeneous phase composition of the active component has been synthesized by the co-decomposition of nickel and copper nitrates followed by the introduction of SiO₂ as a stabilizer. The resulting catalysts have been characterized by temperature-programmed reduction, X-ray powder diffraction, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy combined with energy-dispersive microanalysis. The bulk and surface composition of active-component particles has been determined by XPS and X-ray diffraction. In all of the catalysts containing 15–85 wt % Ni, there are two types of solid solutions. One has a constant composition, Cu_0.95Ni_0.05, which is independent of the Ni/Cu ratio in the catalyst; in the other, the nickel stoichiometry increases with an increasing Ni content of the active component. A correlation has been established between the Ni/Cu ratio and the rate constants of the reaction examined and between the Ni/Cu ratio and the degree of hydrodeoxygenation for all samples. The most active catalyst is Ni85Cu5-SiO₂.     

Atomic and electronic structures of lutetium oxide Lu2O3

The chemical composition, electronic structure, structure, and physical properties a lutetium oxide Lu₂O₃ film are studied by X-ray photoelectron spectroscopy, ellipsometry, and X-ray absorption spectroscopy. The short-range order in Lu₂O₃ is found to correspond to its cubic modification. The binding energies of the 1s and 2p levels of oxygen and the 4d _5/2 and 4f _7/2 levels of lutetium are 529.2, 5.0 and 7.4, 195.9 eV, respectively. The energy gap determined from the electron energy loss spectrum of the film is 5.9 eV. The electron energy loss spectra have two peaks at 17.4 and 22.0 eV, which can be attributed to the excitation of bulk plasma oscillations. The dispersion of the refractive index is measured by spectral ellipsometry. The refractive index is shown to increase from 1.82 at 1.5 eV to 2.18 at 5.0 eV, and the high-frequency permittivity of Lu₂O₃ is 3.31.     

Temperature Hysteresis in the Reaction of Methane Oxidation on a Palladium-Doped Manganese Hexaaluminate Catalyst

A study of the Pd-containing catalyst based on manganese hexaaluminate by X-ray diffraction analysis, transmission electron microscopy, thermo-programmed reduction with hydrogen, and thermoprogrammed oxidation showed the hysteresis manifested itself in a difference between the temperature dependences of its catalytic activity in the oxidation of methane under the conditions of sample heating or cooling is related to the decomposition of PdO to metallic palladium at temperatures higher than 700–800°C and the subsequent formation of PdO nanoparticles, which are localized on the surface of metallic Pd (30–50 nm) in the form of polycrystalline films with a thickness of 2–5 nm, at temperatures lower than 600–700°C. A near-surface oxide film is formed under the conditions of cooling in oxygen-containing atmospheres, including in the presence of methane. The value of the hysteresis depends on the heat treatment temperature of the catalyst, and it reaches a maximum on the catalysts calcined at 900 and 1000°C.     

Effect of the calcination temperature on the properties of Fe2O3/SiO2 catalysts for oxidation of hydrogen sulfide

The effect of the calcination temperature on the properties of supported iron oxide catalysts for hydrogen sulfide oxidation prepared by impregnation of silica with iron(III) nitrate has been studied. An increase in the calcination temperature was found to diminish the catalytic activity of the Fe₂O₃/SiO₂ catalysts in hydrogen sulfide oxidation. This behavior can be explained by the agglomeration of iron oxide particles and by a decrease in the surface concentration of active sites. It has been shown that an increase in the calcination temperature makes the catalyst more stable towards the sulfidation of the active component (Fe₂O₃) to the iron disulfide phase.     

The Nature of Electrophilic and Nucleophilic Oxygen Adsorbed on Silver

Results of a spectroscopic study of two forms of adsorbed atomic oxygen on a silver surface, which participate in ethylene epoxidation reaction, are presented. The possibility of the combined use of the methods of photoelectron spectroscopy and X-ray absorption for a detailed analysis of adsorbate electron structure on solid surfaces is demonstrated. It is found that a significant difference in the position of O 1s lines for nucleophilic (528.3 eV) and electrophilic (530.4 eV) oxygen is determined by the effects of the initial state, that is, by the difference in the charge state of oxygen anions. The use of the well-know correlation of the Auger line splitting with a Pauling charge at an oxygen atom showed a substantial difference (1 electron charge unit) in charge transfer from metal to the nucleophilic or electrophilic adsorbed oxygen atom. Based on the X-ray absorption data of the oxygen K-edge, it is found that there is a substantial overlap of the 4d- and 5sp orbitals of silver with oxygen 2p orbitals in the nucleophilic state in the formation of an Ag–O bond and there is only an overlap of 5sp orbitals of silver with oxygen 2p orbitals in the electrophilic state. Structural models of the adsorption site are presented for both states. The conclusion is drawn that the charge state of oxygen in oxide systems may depend substantially on its binding to metal atoms.     

Surface Properties of Gas Chromatographic Adsorbents Based on Silochrome S-80 Modified by Transition Metal 8-Oxyquinolinates

Russian Journal of Physical Chemistry A - IR spectroscopy and gas chromatography are used to study the acid–base and adsorption properties of the surface of Silochrome S-80 modified with...     

LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> and LiCoO<Subscript>2</Subscript> composite cathode materials obtained by mechanical activation

New composite cathode materials xLiMn₂O₄/(1 ? x) LiCoO₂(x = 0.7, 0.6, 0.5 и 0.4) were obtained by mechanical activation. According to scanning electron microscopy data, the process was accompanied by pronounced dispersion and fine mixing of the initial components. In the course of the preparation and electrochemical cycling of the composites, LiMn₂O₄ and LiCoO₂ partially reacted, leading to the replacement of manganese with cobalt in the structure of spinel, which was detected by powder X-ray diffraction (XRD), IR and X-ray photoelectron spectroscopy (XPS), and cyclic chronopotentiometry. The specific discharge capacity of composites was ～100 mAh/g.