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The possibilities of using powder X-ray diffraction methods in the study of carbon materials are discussed. To determine the phase composition of the crystalline materials the X-ray phase analysis is employed; the real structure is established by the harmonic analysis of diffraction profiles; the structural features and phase composition of the nanomaterials are found by the radial electron density distribution function. [ABSTRACT FROM AUTHOR]

Published data on the application of modern X-ray diffraction methods in the investigation of nanomaterials are reviewed. Examples of investigations on refinement of the phase composition, defect structure, and microstructure of catalytic subjects (supports and deposited catalysts) are presented. The effect of structural defects on the functional characteristics of the catalysts is demonstrated. [ABSTRACT FROM AUTHOR]

The influence of hydrothermal treatment conditions (temperature, duration, acidity of the medium) on the structural and chemical transformations of the complex H2[Pt(OH)6] was studied. The composition and structure of the resulting compounds were determined by several physicochemical methods. Thermal analysis coupled with mass spectrometry showed that, as the hydrothermal treatment temperature is raised from 25 to 120 and 150°C, the product composition in terms of empirical formulas changes as follows: PtO2 · 4H2O → PtO2 · 3.5H2O → PtO2 · 1.5H2O. X-ray diffraction and UV and IR spectroscopy demonstrated that the changes in the chemical composition are accompanied by the amorphization of the structure and Pt-O bond strengthening. X-ray structure determination using the radial electron density distribution method showed that polynuclear species ∼10–15 Å in size with a structure similar to that of orthorhombic PtO2 form in the complexes subjected to “hard” hydrothermal treatment ( T ≥ 150°C). [ABSTRACT FROM AUTHOR]

The influence of the texture of γ-Al2O3 on the formation of Co(Ni)-Mo catalysts for hydrodesulfurization of the diesel fraction is studied. As shown by low-temperature N2 adsorption, X-ray diffraction, IR spectroscopy of adsorbed molecules, and high resolution electron microscopy (HREM), use of a support with a larger specific surface and a lower total concentration of terminal OH groups makes it possible to prepare more active catalysts. The electron density radial distribution method shows that the finely dispersed cobaltcontaining catalyst in its initial state contains CoMoO4, Al2(MoO4)3, and CoAl2O4, the last two phases being present in trace amounts. After the reaction, this catalyst contains cobalt-doped molybdenum sulfide. According to HREM data, the active phase of the cobalt-containing catalyst consists of layered sulfide association species Co1.3Mo2S3.3, which differ in composition from the bulk phase CoMo2S4. It is assumed that, out of the 1.3 cobalt atoms in Co1.3Mo2S3.3 0.3 Co occurs at the edges of the association species and 1.0 Co is intercalated into their interlayer space, and 0.7 S at the boundary between the association species and the Al2O3 phase is replaced by the corresponding amount of oxygen. [ABSTRACT FROM AUTHOR]

The Ru-Cs+/MgO and Ru-Cs+/γ-Al2O3 catalysts, which were prepared by an impregnation method using RuOHCl3 and Cs2CO3 as precursor compounds and reduced with H2 at 450°C, are characterized by X-ray diffraction, high-resolution transmission electron microscopy (with X-ray microanalysis), and X-ray photoelectron spectroscopy (XPS). The Cs+/MgO(Al2O3) systems, Ru-Cs+ black, and model systems prepared by cesium sputtering onto polycrystalline ruthenium foil are studied as reference samples. It is found that, in the Ru-Cs+/MgO sample, cesium is present as a Cs2 + x O cesium suboxide, which weakly interacts with the support, localized on the surface of Ru particles or near them. In the case of Ru-Cs+/γ-Al2O3, cesium occurs as a species that is tightly bound to the support; this is likely surface cesium aluminate, which prevents promoter migration to Ru particles. The Ru-Cs+/MgO sample exhibits a considerable shift of the Ru3 d line in the XPS spectra toward lower binding energies, as compared to the bulk metal. It is hypothesized that this shift is due to a decrease in the electron work function from the surface of ruthenium because of the polarizing effect of Cs+ ions in contact with Ru particles. Based on the experimental results, the great difference between the catalytic activities of the Ru-Cs+/MgO and Ru-Cs+/γ-Al2O3 systems in ammonia synthesis at 250–400°C and atmospheric pressure is explained. [ABSTRACT FROM AUTHOR]

The diffusion intermixing of layers during annealing of epitaxial superlattice nanostructures based on chalcogenide semiconductors (PbS, PbSe, PbTe, EuS, EuSe, SrS) was studed by X-ray diffraction technique. The interdiffusion coefficients were determined basing on changing of the intensity of near-Bragg reflection satellites in X-ray diffraction pattern. Layer materials in superlattices EuS-PbTe and PbS-PbTe are not intermixed. [ABSTRACT FROM AUTHOR]