Zirconium sorption by chelating polymer sorbents with an <Emphasis Type="Italic">o</Emphasis>,<Emphasis Type="Italic">o</Emphasis>′-dihydroxyazo analytical functional group

The complexing properties of new chelating polymer sorbents (CPSs) with an o, o′-dihydroxyazo functionality and zirconium sorption on these sorbents were studied. Quantitative correlations were found between pK′_OH of the analytical functional groups (AFGs) of sorbents and the stability of chelates (logβ) in order to understand the lows governing the effect of the structural features and acid-base properties of the AFGs on zirconium chemisorption parameters. These correlations make it possible to quantitatively predict the physicochemical parameters of sorbents and their chelates, synthesize them, and use CPSs for zirconium preconcentration in analyses of natural and industrial objects.     

Effect of temperature on the growth rate of tin dioxide whiskers formed by physical vapor deposition

The effect of temperature on the vertical growth rate of functional tin dioxide nanostructures formed by physical vapor deposition from a gas phase is studied. A model is proposed to describe the formation of tin dioxide nanocrystals. This model adequately describes the experimentally detected effect of the deposition zone temperature on the nanocrystal growth rate in the temperature range under study. An analytical relation between the growth rate of a nanowhisker, its geometric parameters, the nanowhisker material, the substrate material, and the technological parameters of its formation is revealed. The crystal growth rate is found to increase with the deposition zone temperature, which can be caused by an activation character of nucleation processes and precursor mass transport along the substrate surface and the lateral nanocrystal surface.     

Chemical and electrochemical syntheses of the binuclear zinc and cadmium chelates based on the sterically hindered Schiff bases

Chemical and electrochemical syntheses of a series of the zinc(II) and cadmium(II) complexes were carried out on the basis of sterically hindered Schiff bases, which are the condensation products of 4,6-di-tert-butyl-2-aminophenol with the salicylaldehyde derivatives (H₂L, H₂L¹). The structures and compositions of the synthesized binuclear complexes M₂L₂ and M₂L ₂ ¹ where M = Zn(II) and Cd(II), were proved by the data of elemental analysis, IR spectroscopy, and ¹H NMR spectroscopy. The structures of the Zn₂L₂ · 2Py and Zn₂L₂ · 2DMF dimers were proved by X-ray diffraction analysis. The electrochemical dissolution of zero-valence zinc and cadmium in methanol in the presence of equimolar amounts of H₂L and H₂L¹ made it possible to isolate dimeric complexes of the corresponding metals of the composition M₂L₂ and M_{2 2} ¹ .     

Synthesis, molecular and electronic structures of six-coordinate transition metal (Mn, Fe, Co, Ni, Cu, and Zn) complexes with redox-active 9-hydroxyphenoxazin-1-one ligands

A series of pseudo-octahedral metal (M = Mn, Fe, Co, Ni, Cu, Zn) complexes 4 of a new redox-active ligand, 2,4,6,8-tetra(tert-butyl)-9-hydroxyphenoxazin-1-one 3, have been synthesized, and their molecular structures determined with help of X-ray crystallography. The effective magnetic moments of complexes 4 (M = Mn, Fe, Co, and Ni) measured in the solid state and toluene solution point to the stabilization of their high-spin electronic ground states. Detailed information on the electronic structure of the complexes and their redox-isomeric forms has been obtained using density functional theory (DFT) B3LYP*/6-311++G(d,p) calculations. The energy disfavored low-spin structures of manganese, iron, and cobalt complexes have been located, and based on the computed geometries and distribution of spin densities identified as Mn(IV)[(Cat-N-SQ)](2), Fe(II)[Cat-N-BQ)](2), and Co(II)[Cat-N-BQ)](2) compounds, respectively. It has been shown that stabilization of the high-spin structures of complexes 4 (M = Mn, Fe, Co) is caused by the rigidity of the molecular framework of ligands 3 that sterically inhibits interconversions between the redox-isomeric forms of the complexes. The calculations performed on complex 4 (M = Co) predict that a suitable structural modification that might provide for stabilization of the low-spin electromeric forms and create conditions for the valence tautomeric rearrangement via stabilization of the low-spin electromer and narrowing energy gap between the low-spin ground state tautomer and the minimal energy crossing point on the intersection of the potential energy surfaces of the interconverting structures consists in the replacement of an oxygen in the oxazine ring by a bulkier sulfur atom.     

Immobilization of microorganisms and proteins on honeycomb monoliths and their composites

Immobilization of biocatalysts on several inorganic monolithic supports has been studied. Transition metals added to TiO₂, α-Al₂O₃ and aluminosilicate change the specific protein binding and support capacity. It is shown that immobilized biocatalysts are stable and can be used to run complex biotechnological processes.     

Energy of an excited atomic configuration in alloys

We investigate a model relating the excitation caused by ion bombardment of a metal substrate to the formation of an additional energy minimum relative to the equilibrium state for the excited atomic configuration. We present an explanation of the effects of changing the boundaries of solid solutions during ion implantation. V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 37–40, July, 1996.     

Heterojunctions in a Solid-state Electrochemical System with Lithium Anode Directly Contacting Organic Semiconductor

Solid-state electrochemical cells containing an alkali metal/organic semiconductor direct contact are studied using a potentiodynamic method. Both ionic and electronic charge transfer processes are possible in heterostructures based on direct contact of alkali metals with p-type semiconductors. The multistage processes proceeding in the systems studied involve chemical reactions and changes in the resistance of both the initial cathode material and the cathodic reduction products.     

Linear problems of the dynamics of a floating fluid. Existence theorems

Mathematical Notes -     

Relationship between sulfur dioxide oxidation and selective catalytic NO reduction by ammonia on V2O5?TiO2 catalysts doped with WO3 and Nb2O5

The performance of V₂O₅–TiO₂ catalysts doped by WO₃ and Nb₂O₅ in sulfur dioxide oxidation, and in selective catalytic reduction (SCR) of NO by ammonia has been studied. Addition of tungsten and niobium oxides was found to suppresses sulfur dioxide oxidation thus increasing the catalysts resistance to SO₂ poisoning and their activity in SCR.     

Formation of a nickel catalyst on the surface of aluminosilicate supports for the synthesis of catalytic fibrous carbon

Conditions for the homogeneous precipitation of nickel hydroxide in the presence of urea onto the surface of aluminosilicate honeycomb monoliths, which were prepared based on clay, talc, and amorphous aluminum hydroxide, were examined. Factors affecting the concentration of supported nickel (synthesis time, starting solution concentrations, loaded amount of the support, and support calcination temperature) were studied. The possibility of supporting nickel hydroxide onto the surface of cellular ceramic foam, glass foam, and haydite was demonstrated. The morphology of nickel hydroxide particles, nickel metal particles on support surfaces, and carbon coatings synthesized in the course of the catalytic pyrolysis of a propane-butane mixture was studied by scanning electron microscopy.