Features of electrical explosion alloying of metals and alloys

The kinetics of the electrical explosion of foils has been investigated and the parameters of the plasma jet, the radius of the plasma-affected zone, the pressure and temperature of the plasma in the shock-compressed layer near the irradiated surface, and the accepted power density at the jet axis have been calculated in relation to the dimensions of the plasma accelerator, the distance from the nozzle exit section to the irradiated surface, and the charge voltage of the energy store. Modes of electrical explosion alloying of metals have been determined experimentally which are associated with surface melting, splashing of melt, effects of convective heat and mass transfer, aftereffect, and also with physicochemical and physicomechanical features of the materials used. Methods of optical, scanning, and transmission electron diffraction microscopy have been used to examine the relief, phase composition, and defect substructure of the surface layers of metals after various types of one-and two-component electrical explosion alloying. A multilayer structure has been revealed which is characterized by the degree of variation of the phase-structure state and of the material mechanical characteristics. Based on the features of the multiphase jet that serves as a tool for affecting the surface, some propositions have been made on the physical nature of the processes occurring in a material subject to electrical explosion alloying. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 71–83, May, 2008.     

X-ray diffraction study of a sequence of phase transitions in Cs2HgCl4 crystals

The temperature behavior of lattice parameters and diffraction patterns of the reciprocal lattice in Cs₂HgCl₄ crystals is studied by x-ray diffraction in the temperature range from 4.2 to 300 K. A sequence of phase transitions is observed and attributed to the evolution of incommensurate and commensurate modulations along the crystallographic a and c axes of a unit cell in the initial Pnma structure.     

Copper(I) complexes with phenylphosphonous acid diamide

Copper(I) halide complexes with phenylphosphonous diamide ligand (L), C₅₆H₁₀₀Br₄Cu₄N₈P₄ (II) and C₅₆H₁₀₀Cu₄I₄N₈P₄ (III), were synthesized and studied by X-ray diffraction to determine their molecular and crystal structures (CIF files CCDC nos. 1426622 (II), 1426623 (III)). The prepared coordination compounds are cubane-like tetramers like L₄Cu₄X₄. During the reaction, copper(I) is coordinated to the phosphorus atom of ligand L. The stability of the complexes depends considerably on the halogen atom. The iodide complexes are most stable during storage.     

About specific features of the structure modulation in the Bi-ferrate compounds isostructural with Bi2Sr2CaCu2O8

The single-crystalline specimens of the Fe-doped (5% ⁵⁷Fe) Bi₂Sr₂CaCu₂O₈ (2212Cu) compound have been synthesized to compare the behavior of the structure modulation in Bi-cuprate and Bi-ferrate compounds. According to the Mössbauer data obtained, one can conclude that extra oxygen, related to the presence of Cu³⁺ in 2212Cu, is most probably arranged in the Ca layer rather than in the Bi layer, as was supposed in the model of extra oxygen. Based on the analysis of the experimental data we propose the explanation of the structure modulation in Bi compounds. Due to the mismatch between the internal perovskite block and the external BiO layers the structure of the Bi compounds is distorted. The Sr layer being boundary between these blocks probably is most distorted and stressed. We suppose that the different changes related to the modulation can occur just in this layer. The Bi excess, which is always present in Bi compounds (especially in single crystals), can be just the necessary condition at which the modulation appears. Extra oxygen in principle can be present in modulated structures. However, in our opinion, it only complements the influence of other factors and is not the driving force in the structure modulation.     

Electroexplosive Carburizing of Iron: Surface Relief,Phase Composition and Defect Substructure

Surface relief, phase composition and defect substructure of the surface layer of iron specimens are investigated using scanning and transmission electron microscopy after high-energy electroexplosive carburizing treatment. The structure formed is shown to exhibit a conspicuous gradient character resulting from variations in carbon content with the layer depth. It is found out that a liquid melt of the sublayer of nanocrystalline structure is formed at the boundary of the melt pool. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 36–41, September, 2005.     

Advances in the studies of bisphosphorylated dihydric phenols

The data on the synthesis, structure, and chemical properties of bisphosphorylated dihydric phenols are summarized. All the currently known methods for the synthesis of the systems in question are shown. Specific features of their structure, chemical and complexation properties, as well as areas of application of these compounds were analyzed.     

Structural aspects of the dielectric anomaly in SC(NH2)2 crystals at 161 K

The residual incommensurate modulations in the ferroelectric phase of the SC(NH₂)₂ thiourea are investigated using single-crystal x-ray diffractometry. It is found that the structural states of the ferroelectric phase (T<169 K) depend on the thermal prehistory of the crystal in the temperature range of existence of the incommensurate phase (202-169 K). The dielectric anomaly observed at T _x=161 K is justified structurally.     

Effect of finely dispersed platinum on the structure of luminescence spectra of the adsorbates of magnesium phthalocyanine on silicon dioxide

The luminescence and excitation spectra and kinetic characteristics of the luminescence of the adsorbates of magnesium phthalocyanine (MgPhc) on SiO₂ and the effect on them of surface hydration and finely dispersed platinum are studied. It is found that a structure that improves hydration of the adsorbent surface appears on the platinized surface in the luminescence and excitation spectra. It is assumed that the spectral structure is due to the complexes of MgPhc formed with water molecules, the hydroxyl cover of the surface, and the surface centers of SiO₂ modified by a Pt-catalyst. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 552–555, July–August, 1999.     

Evolution of the structure of Rb2ZnCl4 over the temperature range 4.2–310 K

X-ray diffraction is used to study the temperature dependence of the lattice parameters and the sequence of structural realignments in crystalline Rb₂ZnCl₄ over temperatures of 4.2–310 K. The appearance of and changes in the system of satellite reflexes indicative of structural ordering are studied. Below 74 K, on going into the monoclinic phase (space group A11a), anomalies are observed in the behavior of the lattice parameters, and superstructural reflexes develop with wave vectors q=a ^*/3+b ^*/2+c ^*/2 corresponding to an increase by a large factor in initial parameters a, b, and c of the Pnma-phase. Fiz. Tverd. Tela (St. Petersburg) 41, 1084–1090 (June 1999)     

Structure and phase transitions in trigonal Cs3Sb2I9 crystals

The atomic structure of Cs₃Sb₂I₉ single crystals was refined using X-ray diffraction data (sp. gr. P3m1; wR = 1.58% and R = 3.07%). The phase transitions revealed earlier were found to be accompanied by the appearance of superstructural reflections. At T _c1 = 86 K, the reflections indicating doubling of the c parameter. At T _c2 = 73 K, a first-order phase transition takes place accompanied by “freezing” of the satellites h, k + 1/2, l + 1/2 reflections. In the temperature range from 73 to 78 K, an incommensurate phase providing the satellites h, k + 1/2 + δ, l + 1/2 is formed.