Phone: +7 (383) 330-67-71, Fax: +7 (383) 330-80-56, E-mail: bic@catalysis.ru
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Phase Analysis Methods
Single- and multi-component polycrystalline and nanocristalline systems.
X-ray powder diffraction is used for the study of the composition, structure, microstructure, and phase conversion dynamics in the single- and multi-component polycrystalline and nanocristalline systems.
Following estimations are performed:
dynamics of phase composition variation, dispersity, structural parameters of specific phases (unit cell parameters, structural type, characteristics of an atomic structure deviation from the ideal one under the temperature and medium influence and others), kinetic parameters of phase transitions.
The method becomes a necessity under the reversible action of the specific conditions onto the substance and might be used in the various fields of science and engineering (catalysts, minerals, metals and any chemical compounds).
1. In the Siberian Center of Synchrotron Radiation of the Siberian Branch of the Russian Academy of Sciences (SB RAS) jointly with the Institute of Chemistry of Solid and Mechanochemistry of SB RAS a precise diffractometer allowing to obtain the diffraction patterns with a resolution (peak half width) up to 0.03° by 2Θ in the wide range of wave length 0.05 – 0.4 nm. Due to the possibility of wave length variation the anomalous scattering method might be used for the study of isomorphous substitutions and for the construction of the partial functions of radial atom distribution.
2. An original software for the simulation of real structure and diffraction patterns of ultra-dispersed and partially disordered systems has been developed. With this technique on the basis of a full profile analysis of the diffraction pattern it is possible to obtain the detail information about CSD, micro-strains (I and II type), type and concentration of defects of layers deposition and others. It is possible to study the real structure of a lot of objects, including crystals with a developed micro-domain structure and crystals with very small physical sizes, paracrystals, turbostrate structures, various polytypic and modulated structures as well as diversity of real systems in which various sources of disordering of the long-range order simultaneously take place.
Experimental (asterics) and theoretical (solid line) X-ray diffraction patterns
of aluminum-magnesium spinel (R1 = 4.5 %, Rp = 7.6 %)
A full profile analysis of X-ray diffraction images allows not only to refine the average crystalline structure (atoms coordinates in the elementary cell, positions occupation, heating parameters) but to define the structure of extended defects as well. The example given for the non-stoichiometric aluminum-magnesium spinel displays these possibilities. The theoretical diffraction image corresponds to the experimental X-ray pattern with a high accuracy.
The local structure and concentration of the planar defects are determined from the X-ray diffraction data. They constitute the dislocation walls forming the pseudo hexagonal closed loops that are visualized by the technique of high resolution electron microscopy (HRTEM).
/Journ. Struct. Chem. [JSTCAM], v.32, p.325 [1997]/
Siemens D500, URD-6, URD-63, HZG-4B, HZG-4C, Bruker D8 diffractometers (Germany); high resolution diffractometer with synchotron emission in the Siberian Center of Synchotron Radiation of SB RAS. The X-ray tubes with the copper and molybdenum anodes are applied on the series-produced diffractometers. Bases of X-ray diffraction powdery (PC-PDF) and crystallostructural data are available.
Samples in the form of powder (0.5–2 cm3), plates, tablets (not less than 5x5 mm2) with the indication of chemical composition.
Prof. S.V. Tsybulya. Full profile analysis and study of the defective structures.
Prof. L.M. Plyasova. Regularities of the formation of complex oxide catalytic systems, X-ray in situ.
Prof. E.M. Moroz. Study (including by REDD method) of the structure of oxides, carbon-containing materials, highly dispersed bulk and supported metals.