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Title: Coherent 3D nanostructure of γ-Al{sub 2}O{sub 3}: Simulation of whole X-ray powder diffraction pattern

Abstract

The structure and nanostructure features of nanocrystalline γ-Al{sub 2}O{sub 3} obtained by dehydration of boehmite with anisotropic platelet-shaped particles were investigated. The original models of 3D coherent nanostructure of γ-Al{sub 2}O{sub 3} were constructed. The models of nanostructured γ-Al{sub 2}O{sub 3} particles were first confirmed by a direct simulation of powder X–Ray diffraction (XRD) patterns using the Debye Scattering Equation (DSE) with assistance of high-resolution transmission electron microscopy (HRTEM) study. The average crystal structure of γ-Al{sub 2}O{sub 3} was shown to be tetragonally distorted. The experimental results revealed that thin γ-Al{sub 2}O{sub 3} platelets were heterogeneous on a nanometer scale and nanometer-sized building blocks were separated by partially coherent interfaces. The XRD simulation results showed that a specific packing of the primary crystalline blocks in the nanostructured γ-Al{sub 2}O{sub 3} particles with formation of planar defects on (001), (100), and (101) planes nicely accounted for pronounced diffuse scattering, anisotropic peak broadening and peak shifts in the experimental XRD pattern. The identified planar defects in cation sublattice seem to be described as filling cation non-spinel sites in existing crystallographic models of γ-Al{sub 2}O{sub 3} structure. The overall findings provided an insight into the complex nanostructure, which is intrinsic to the metastablemore » γ-Al{sub 2}O{sub 3} oxide. - Highlights: • Thin plate-like crystallites of γ-Al{sub 2}O{sub 3} were obtained. • Models of 3D coherent nanostructure of γ-Al{sub 2}O{sub 3} were constructed. • Models were verified by simulating XRD patterns using the Debye Scattering Equation. • Specific broadening of XRD peaks was explained in terms of planar defects. • Primary crystalline blocks in γ-Al{sub 2}O{sub 3} are separated by partially coherent interfaces.« less

Authors:
 [1];  [2];  [2];  [1];  [2]; ; ; ;  [1];  [2];  [2]
  1. Boreskov Institute of Catalysis SB RAS, Pr. Lavrentieva 5, 630090 Novosibirsk (Russian Federation)
  2. (Russian Federation)
Publication Date:
OSTI Identifier:
22658195
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 246; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM OXIDES; CRYSTAL DEFECTS; DIFFUSE SCATTERING; EXPERIMENTAL DATA; NANOSTRUCTURES; PARTICLES; PEAKS; POWDERS; SIMULATION; SYNTHESIS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION

Citation Formats

Pakharukova, V.P., E-mail: verapakh@catalysis.ru, Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090, Yatsenko, D.A., Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, Gerasimov, E. Yu., Shalygin, A.S., Martyanov, O.N., Tsybulya, S.V., Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, and Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090. Coherent 3D nanostructure of γ-Al{sub 2}O{sub 3}: Simulation of whole X-ray powder diffraction pattern. United States: N. p., 2017. Web. doi:10.1016/J.JSSC.2016.11.032.
Pakharukova, V.P., E-mail: verapakh@catalysis.ru, Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090, Yatsenko, D.A., Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, Gerasimov, E. Yu., Shalygin, A.S., Martyanov, O.N., Tsybulya, S.V., Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, & Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090. Coherent 3D nanostructure of γ-Al{sub 2}O{sub 3}: Simulation of whole X-ray powder diffraction pattern. United States. doi:10.1016/J.JSSC.2016.11.032.
Pakharukova, V.P., E-mail: verapakh@catalysis.ru, Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090, Yatsenko, D.A., Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, Gerasimov, E. Yu., Shalygin, A.S., Martyanov, O.N., Tsybulya, S.V., Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk, and Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090. Wed . "Coherent 3D nanostructure of γ-Al{sub 2}O{sub 3}: Simulation of whole X-ray powder diffraction pattern". United States. doi:10.1016/J.JSSC.2016.11.032.
@article{osti_22658195,
title = {Coherent 3D nanostructure of γ-Al{sub 2}O{sub 3}: Simulation of whole X-ray powder diffraction pattern},
author = {Pakharukova, V.P., E-mail: verapakh@catalysis.ru and Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk and Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090 and Yatsenko, D.A. and Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk and Gerasimov, E. Yu. and Shalygin, A.S. and Martyanov, O.N. and Tsybulya, S.V. and Novosibirsk State University, Pirogova Street 2, 630090 Novosibirsk and Research and Educational Center for Energy Efficient Catalysis, Novosibirsk State University, Novosibirsk 630090},
abstractNote = {The structure and nanostructure features of nanocrystalline γ-Al{sub 2}O{sub 3} obtained by dehydration of boehmite with anisotropic platelet-shaped particles were investigated. The original models of 3D coherent nanostructure of γ-Al{sub 2}O{sub 3} were constructed. The models of nanostructured γ-Al{sub 2}O{sub 3} particles were first confirmed by a direct simulation of powder X–Ray diffraction (XRD) patterns using the Debye Scattering Equation (DSE) with assistance of high-resolution transmission electron microscopy (HRTEM) study. The average crystal structure of γ-Al{sub 2}O{sub 3} was shown to be tetragonally distorted. The experimental results revealed that thin γ-Al{sub 2}O{sub 3} platelets were heterogeneous on a nanometer scale and nanometer-sized building blocks were separated by partially coherent interfaces. The XRD simulation results showed that a specific packing of the primary crystalline blocks in the nanostructured γ-Al{sub 2}O{sub 3} particles with formation of planar defects on (001), (100), and (101) planes nicely accounted for pronounced diffuse scattering, anisotropic peak broadening and peak shifts in the experimental XRD pattern. The identified planar defects in cation sublattice seem to be described as filling cation non-spinel sites in existing crystallographic models of γ-Al{sub 2}O{sub 3} structure. The overall findings provided an insight into the complex nanostructure, which is intrinsic to the metastable γ-Al{sub 2}O{sub 3} oxide. - Highlights: • Thin plate-like crystallites of γ-Al{sub 2}O{sub 3} were obtained. • Models of 3D coherent nanostructure of γ-Al{sub 2}O{sub 3} were constructed. • Models were verified by simulating XRD patterns using the Debye Scattering Equation. • Specific broadening of XRD peaks was explained in terms of planar defects. • Primary crystalline blocks in γ-Al{sub 2}O{sub 3} are separated by partially coherent interfaces.},
doi = {10.1016/J.JSSC.2016.11.032},
journal = {Journal of Solid State Chemistry},
number = ,
volume = 246,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2017},
month = {Wed Feb 15 00:00:00 EST 2017}
}
  • Low-temperature {gamma}-, {eta}-, and {chi}-Al{sub 2}O{sub 3} polymorphs were studied by high resolution transmission electron microscopy and x-ray powder diffraction along with computer simulation of the diffraction patterns. Planar defects lying on the (111), (110), and (100) planes, which are the origin of the broadening of x-ray diffraction peaks in different forms of aluminium oxide, were revealed. In addition to providing strong experimental support for the imperfect character of the specimen structures, these results demonstrate the possibility of using nanosized crystalline domains with a spinel-type arrangement, which are regularly shaped and have a specified, developed face and bounding surfaces, formore » the description of the nanostructure of a whole variety of low-temperature Al{sub 2}O{sub 3} derivatives. It was found that different ways of domain packing in the oxide particles with a subsequent formation of planar defects contribute to specific kinds of line-shape broadening observed in the x-ray diffraction patterns of these materials. The mechanism of the vacancy generation upon propagation of the shear-type defect in the (110) plane of the spinel structure, which changes the Al{sub 3}O{sub 4} stoichiometry to Al{sub 2}O{sub 3}, is also discussed.« less
  • The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 deg. C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl{sub 2}O{sub 4}.10H{sub 2}O converted to Ca{sub 3}Al{sub 2}(OH){sub 12} and amorphous aluminum hydroxide. Ca{sub 2}Al{sub 2}O{sub 5}.8H{sub 2}O transformed via the intermediate phase Ca{sub 4}Al{sub 2}O{sub 7}.13H{sub 2}O to Ca{sub 3}Al{sub 2}(OH){sub 12} and gibbsite, Al(OH){sub 3}. The phase Ca{sub 4}Al{sub 2}O{sub 7}.19H{sub 2}O reacted via the same intermediate phase to Ca{sub 3}Al{sub 2}(OH){sub 12} and mainlymore » amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported.« less
  • The three-dimensional structure of a complex tubular uranyl phosphonate, (UO{sub 2}){sub 3}(HO{sub 3}PC{sub 6}H{sub 5}){sub 2}(O{sub 3}PC{sub 6}H{sub 5}){sub 2}(O{sub 3}PC{sub 6}H{sub 5}){sub 2} {center_dot} H{sub 2}O, was determined ab initio from laboratory X-ray powder diffraction data and refined by the Rietveld method. The crystals belong to the space group P2{sub 1}2{sub 1}2{sub 1}, with {alpha} = 17.1966(2) {Angstrom}, b = 7.2125(2) {Angstrom}, c = 27.8282(4) {Angstrom}, and Z = 4. The structure consists of three independent uranium atoms, among which two are seven-coordinated and the third is eight-coordinated. These metal atoms are connected by four different phosphonate groups tomore » form a one-dimensional channel structure along the b axis. The phenyl groups are arranged on the outer periphery of the channels, and their stacking forces keep the channels intact in the lattice. The determination of this structure which contains 50 non-hydrogen atoms in the asymmetric unit, from conventional X-ray powder data, represents significant progress in the application of powder techniques to structure of complex inorganic compounds, including organometallic compounds.« less
  • A series of NiO-WO/sub 3//Al/sub 2/O/sub 3/ catalysts were studied by UV-vis diffuse reflectance spectroscopy (DRS) and x-ray diffraction (XRD). Both the metal content and the temperature of calcination of the catalysts were varied over a wide range. It was found that W is present as a W/sup 6 +/ surface phase regardless of the temperature of calcination and W content. In NiO/Al/sub 2/O/sub 3/ samples several Ni/sup 2 +/ species were detected: an octahedral species located at the surface and both an octahedral and a tetrahedral species located in the Al/sub 7/O/sub 3/ support. In NiO-WO/sub 3//Al/sub 2/O/sub 3/more » samples a different octahedral Ni species was also found, in which Ni is present in a mixed phase containing Ni, W, Al, and O. The Ni content has some influence on the speciation of Ni, but the temperature of calcination is the major factor which determines the location and the coordination of Ni. Calcination below 775 K results in catalysts which contain only octahedral Ni at the surface. At higher temperatures diffusion of Ni into the support is detected by XRD, and at 1175 K an equilibrium distribution throughout the support particles is established. In the support most of the Ni is tetrahedrally coordinated, and above 925 K the distribution of Ni over tetrahedral and octahedral sites is hardly affected by a change in calcination temperature or Ni content. A model is presented which can quantitatively describe the diffusion process using independently determined parameters. It is concluded that Ni diffusion into the support is negligible under hydrodesulfurization (HDS) reaction conditions, which stresses the importance of the structure of the oxidic precursor for the structure and HDS activity of sulfided catalysts.« less