Trends in formation of the nanocrystalline structure and cationic ordering in the Dy2O3-HfO2 (1: 1) system

Evolution of the nanocrystalline structure of the complex oxide Dy₂HfO₅ in the course of thermal annealing at temperatures to 1600°C has been studied by a combination of X-ray and synchrotron methods, including traditional and anomalous X-ray diffraction, PDF, EXAFS, and SAXS. The changes in crystallite size upon annealing of the as-synthesized amorphous precursor have been analyzed in detail. The systematic distortions of a fluorite-type perfect crystal structure (space group $Fm\bar 3m$ ) related to the nonequivalence of the local environment of the Dy and Hf cations but not resulting in formation of a pyrochlore-type cationordered structure in this system have been examined.     

Structure and properties of (Ac)Fe(III)-5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrin in the reaction with organic peroxides in benzene: The effect of imidazole on reaction kinetics

The kinetics of the reaction between (Ac)Fe(III)-5,15-diphenyl-3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrin and dicumene peroxide in benzene at 295 K was studied with the purpose of further studying the effect of the conformational and electronic factors of nonplanar metalloporphyrinates on redox properties using a combination of computational and spectrophotometric methods. The molecular structures of reagents and intermediates of the studied reaction were optimized by the PM3 quantum-chemical method. The obtained characteristics were analyzed, and the distortion of a macrocycle was established to considerably increase in the reaction of iron(III) porphyrinate with peroxides. The intermediate molecule was found to be sterically hindered and extremely unstable. The kinetic characteristics of the reaction were obtained spectrophotometrically. The nature of a metal atom and the distortion of a macrocycle were established to have some effect on the process rate. The introduction of imidazole into a reaction mixture and the variation of concentration of a base were shown to produce some changes in the composition of reagents and the kinetics of the process. A good agreement between experimental and calculated data was observed.     

Synthesis and structure of complexes of some d metals with 10-(2-benzothiazolylazo)-9-phenanthrole (HL). Crystal and molecular structures of [CdL2] · DMF

The coordination compounds of cadmium(II), zinc(II), nickel(II), cobalt(II), and copper(II) with 10-(2-benzothiazolylazo)-9-phenanthrole (HL) were isolated in the crystalline state and studied. The crystal structure of the cadmium complex [CdL₂] · DMF was determined by X-ray diffraction. The ligand is attached to cadmium in the form of anion functioning as an O,N,N-tridentate chelating ligand; this is accompanied by a change in its isomer form. The Cd configuration is a distorted octahedron.     

Synthesis and structure of the oxalatotetranitratouranylate complex (NH4)2[{UO2(NO3)2}2(μ4-C2O4)] · 2H2O

The reaction of diaquadinitratouranyl with ammonium nitrate in ethanol gave the single crystals of ((NH₄)₂[}UO₂(NO₃)₂}₂(μ₄-C₂O₄)] · 2H₂O (I).The structure of the complex was studied by X-ray diffraction. The crystals are monoclinic, a = 8.6497(10) Å, b = 11.7001(10) Å, c = 20.2135(10) Å, β = 93.924(10)°, space group P2₁/c, Z = 4, V = 2040.9(3) ų. The structural units of the crystal are island binuclear groups [{UO₂(NO₃)₂}₂(μ₄-C₂O₄)]^2?, ammonium cations, and crystal water molecules. The structure has a complex three-dimensional packing provided by electrostatic attraction forces of the counterions and the hydrogen bond system involving water molecules, oxalate, nitrate, and uranyl ions. The IR spectra of I confirm the X-ray diffraction data.     

Synthesis, crystal, and molecular structure of the solvated complex [MoO2(L)] · DMF (L2− = 2-[N-(2-hydroxynaphthylidene)amino]propane-1,2,3-triol anion)

A new dioxomolybdenum(VI) complex, [MoO₂(L)] · DMF, where L^2? = 2-[N-(2-hydroxynaphthylidene)amino]propane-1,2,3-triol, has been synthesized. Its structure has been determined by X-ray diffraction analysis. The Mo atom is octahedrally coordinated by two oxo ligands that are in cis-positions with respect to each other, two oxygen atoms, the nitrogen atom of the tridentate bis(chelate) ligand L, and the DMF oxygen atom.     

Chemical interaction in the quaternary mutual systems Li,K‖F,Cl,MoO4 and Li,K‖F(Cl),VO3,MoO4

The Li,K‖Cl,VO₃,MoO₄ system was partitioned into simplexes using graph theory, and the tree of phases for this system was constructed. The equations of the main reactions describing the chemical interaction in the quaternary mutual systems Li,K‖F,Cl,VO₃(MoO₄) and Li,K‖F(Cl),VO₃,MoO₄ were derived using the conversion patterns of partitioning elements. Based on the reaction equations and the data on the boundary elements, the prediction of phases crystallizing in the studied systems was made and confirmed by X-ray powder diffraction analysis.     

Synthesis and characterization of MIIU3O10 · nH2O (MII = Mg, Mn, Co, Ni, Cu, Zn, Cd) triuranates

Individual crystalline phases of composition M^IIU₃O₁₀ · nH₂O were prepared by reacting schoepite UO₃ · 2.25H₂O with aqueous solutions of Mg, Mn, Co, Ni, Cu, Zn, or Cd nitrates under hydrothermal conditions at 200°C. The composition and structure of the resultant compounds were determined by hightemperature X-ray diffraction, IR spectroscopy, scanning calorimetry, and chemical analysis; the dehydration and thermal destruction of the compounds were studied.     

Transformation of wood during ozonization in the presence of hydrogen peroxide

Samples of ozonized aspen wood pretreated with hydrogen peroxide solutions of various concentrations are investigated by UV diffuse reflectance spectroscopy, IR spectroscopy, and X-ray structural analysis. The general course of wood transformation under the action of the O₃/H₂O₂ system is associated with the destruction of lignin and oxidation of carbohydrates, raising the fraction of the crystalline phase in a lignocarbohydrate material. The possibility of varying the depth of the chemical and structural transformation of the substrate upon changing the hydrogen peroxide concentration in the O₃/H₂O₂ system is demonstrated.     

35Cl quadrupole resonance study of the thermally activated motion of the nitro group in chlorinated nitrobenzenes

The results of NQR studies of the thermoactivated motion of NO₂ groups in chlorine-containing nitrobenzenes are presented. A procedure for analyzing the experimental data is suggested. It uses the characteristic temperature of the minimum of the modulation contribution to the temperature dependence of the spin-lattice relaxation time T ₁ of the resonant probe nuclei (³⁵Cl) bonded with the moving group by nonvalent interactions. The activation energy of the thermoactivated motion was correlated with the temperature of the minimum. The possibility of a temperature dependence of the activation energy of the NO₂ group was examined.     

Reconstruction of the Dependence of Radiative Loss of the Tokamak Plasma Using the Experimental Transverse Distribution of Radiation

Technical Physics - Theoretical principles for determination of the power density of electromagnetic radiation (radiative loss) in a plasma volume with cylindrical symmetry are based on the results...