Nanofiltration treatment of aqueous solutions to remove triazine herbicides

Nanofiltration treatment of aqueous solutions to remove triazine herbicides (terbumetone, desmetrine, atrazine) with an OPMN-P membrane was studied. The effect of the molecular mass of herbicides, working pressure, and extent of permeate removal on the retention of solutes was analyzed.     

Cluster self-organization of nanotubes in a nematic phase: The percolation behavior and appearance of optical singularities

The structural features, as well as the optical and electrophysical properties of a 5CB nematic liquid crystal with additions of multilayer carbon nanotubes, have been investigated in the concentration range C = 0.0025–0.1 wt %. The self-aggregation of nanotubes into clusters with a fractal structure occurs in the liquid crystal. At 0.025 wt %, the clusters are merged, initiating the percolation transition of the composite to a state with a high electric conductivity. The strong interaction of 5CB molecules with the surface of nanotube clusters is responsible for the formation of micron surface liquid crystal layers with an irregular field of elastic stresses and a complex structure of birefringence. They are easily observed in a polarization microscope and visualize directly invisible submicron nanotube aggregates. Their transverse size increases when an electric field is applied to the liquid crystal cell. Two mechanisms of the generation of optical singularities in the passing laser beam have been revealed. Optical vortices appear in the speckle fields of laser radiation scattered at the indented boundaries of the nanotube clusters, whereas the birefringence of the beam in surface liquid-crystal layers is accompanied by the appearance of polarization C points.     

Quadrupole effects and distortion of the structure of NaNbF6 and KnbF6 from93Nb and23Na NMR data

Journal of Structural Chemistry -     

Relationship between the catalytic behavior of FeZSM-5 zeolites in oxidative degradation of dyes and the nature of their active centers

Catalytic activity of FeZSM-5 zeolites in oxidative degradation of Rhodamine 6G and Methyl Orange dyes was studied in relation to the nature, localization, and dispersity of active centers and on the reversibility of the oxidation reduction of iron contained in the zeolites.     

NMR spectroscopy of bismuth fluoride glasses with alkali cations

Results of the ⁷Li, ¹⁹F, and ²³Na NMR studies of ionic mobility in bismuth fluoride glasses in the systems BiF₃-LiF and BiF₃-MF-ZrF₄ (M = Li, Na, K, Cs) are summarized. Analysis of the ⁷Li, ¹⁹F, and ²³Na NMR spectra made it possible to reveal changes in the nature of ion motions in the fluoride, lithium and sodium sublattices of glasses upon temperature variation and to determine their types. The temperature ranges were found where main types of ion motions in the tested glasses are represented by diffusion of lithium ions, reorientations of fluorine-containing groups constituting the glass network, and diffusion of fluorine ions. The role of alkali cations in the formation of ionic mobility in bismuth fluorozirconate glasses is considered.     

Quantum chemical study of the geometrical and electronic structure of niobium pentafluoride

The geometrical and electronic structure of various configurations of niobium pentafluoride is studied in the nonrelativistic approximation of the DV-X_α method. It is shown in a cluster approximation that the presence of the NbF₅ monomer in various geometrical configurations and of the cyclic [NbF₅]₃ trimer (D_3h symmetry) is most probable for the liquid and gaseous phases. Formation of infinite [NbF₅]_n chains is unlikely. For the most stable clusters, the calculated geometrical parameters are in satisfactory agreement with the available experimental data.     

Use of titanium dioxide for surface modification of polymeric membranes to diminish their biological contamination

Adhesion of microorganisms to the surface of polymeric membranes and the efficiency of modification of the membrane surface by deposition of titanium dioxide to diminish biological overgrowth were studied.     

Spin-glass, antiferromagnetism and kondo behavior in Ce2Au1−x Co x Si3 alloys

Recently, the solid solution Ce₂Au_{1− x Co} xSi₃ has been shown to exhibit many magnetic anomalies associated with the competition between magnetic ordering and the Kondo effect. Here we report high pressure electrical resistivity of Ce₂AuSi₃, ac susceptibility (X) and magnetoresistance of various alloys of this solid solution in order to gain better knowledge of the magnetism of these alloys. High pressure resistivity behavior is consistent with the proposal that Ce₂AuSi₃ lies at the left-hand side of the maximum in Doniach’s magnetic phase diagram. The ac X data reveal that there are in fact two magnetic transitions, one at 2 K and the other at 3 K for this compound, both of which are spin-glass-like. However, as the Co concentration is increased, antiferromagnetism is stabilized for intermediate compositions before attaining non-magnetism for the Co end member.     

Synthesis of Glass-Ceramics in Mixed Fluorozirconate–Phosphate Systems

Fluorozirconate-phosphate glasses of the ZrF₄–BaF₂–NaPO₃(LiPO₃) and ZrF₄–BaF₂–LaF₃–AlF₃–LiPO₃ systems doped with EuF₃, ErF₃, and NdF₃ were studied by the differential-thermal (DTA) and X-ray diffraction (XRD) analysis, luminescence spectroscopy, scanning and transmission electron microscopy (SEM and TEM) methods. Addition of the phosphate component up to 20 mol % decreases the glass transition temperature and increases the glass stability to crystallization. Heat treatment in the range >T_g–T_c1 of glass transition and first maxima of crystallization temperatures causes crystallization of nanosized β-BaZrF₆ particles. At LiPO₃ (NaPO₃) concentrations of more than 80 mol %, glasses containing a crystalline phase are formed during the synthesis process.