Vol 61, No 12 (2016)

Sol–gel technology was used to chemically modify the surface of HfB₂ powders with highly dispersed silicon carbide using two carbothermy protocols: (1) under heating to 1500°С in flowing argon (100 mL/min) without exposure and (2) under dynamic vacuum conditions (p ~ 1 × 10^–5–1 × 10^–6 MPa) at 1400°С with 4-h exposure. The phase composition and microstructural features of the thus-prepared HfB₂/xSiC (x = 10–65 vol %) composite powders were studied. The products prepared by the second protocol showed an enhanced oxidation resistance in the range 20–1400°C in flowing air compared to individual HfB₂.

This study is concerned with the preparation of hydrolytically active heteroligand complex [Ti(OC₄H₉)_3.61(O₂C₅H₇)_0.39] from titanium butoxide and acetylacetone and with the gel formation kinetics in a solution of this complex upon hydrolysis and polycondensation. Single-layer and double-layer thin films of a solution of this precursor were coated on polished silicon substrates using the dip-coating method. The crystallization of nanostructured titania films during the heat treatment of these xerogel coatings was studied using various protocols; the anatase–rutile phase transition temperature was found to depend on the film thickness. The effects of the precursor solution viscosity on the film thickness and crystallite size were determined.

Phase ratios in the subsolidus regions of Rb₂MoO₄–CaMoO₄–R₂(MoO₄)₃ systems (R = Nd, Sm, Eu, or Gd) were studied by vibrational spectroscopy, X-ray diffraction, and differential thermal analysis. Ternary molybdates RbCaR(MoO₄)₃ (R = Nd, Sm, Eu, Gd) with scheelite derivative structures (monoclinic symmetry system, space group P21/n) were synthesized. Unit cell parameters were determined, and IR and Raman spectra were characterized.

New complexes of uranyl with diethylglyoxime have been synthesized and studied. A feature of these complexes is the tetradentate bridging coordination of the ligand in both cis- and trans-conformations. The structure of organic ligand C₆H₁₂N₂O₂ and binuclear complex (CN₃H₆)₄[(UO₂)₂(C₆H₁₀N₂O₂)(CO₃)(C₂O₄)₂] ∙ H₂O have been determined by X-ray diffraction.

The complexes [AgL₂(NO₃)] (I) and [AgL₂(CH₃SO₃)] · H₂O (II) (L is 2-methylquinoline, C₁₀H₉N) have been synthesized and structurally characterized by single-crystal X-ray diffraction. Crystals of I are monoclinic, space group P2₁/n, a = 9.296(1) Å, b = 13.495(1) Å, c = 14.931(1) Å, β = 95.06(1)°, V = 1865.8(3) ų, ρ_calc = 1.624 g/cm³, Z = 4. Crystals of II are monoclinic, space group P2₁/n, a = 13.147(1) Å, b = 11.767(1) Å, c = 13.814(1) Å, β = 96.06(1)°, V = 2124.3(3) ų, ρ_calc = 1.599 g/cm³, Z = 4. Compounds I and II are composed of discrete complexes of similar structure but with different orientation of the methyl groups of ligand L (trans and cis arrangement, respectively). Both anions, NO₃^- and CH₃SO₃^- function as a chelating weakly bound ligand for the Ag⁺ ion. The presence of water molecules in II is favorable for the formation of dimeric supramolecular moieties between the centrosymmetrically arranged Ag⁺ complexes with 2-methylquinoline. The luminescence spectra of solid complexes I and II showed a bathochromic shift as compared to the spectrum of L in acetonitrile. Complexes I and II have been characterized by ¹H and ¹³C{H} NMR spectra in CD₃CN.

In the framework of the search for promising electrolytes for lithium-ion batteries. quantum-chemical modeling of the structure. Stability, and electronic properties of membranes based on LiNafion*dimethyl sulfoxide (LiNafion*nDMSO, n = 0–18) has been performed. It has been demonstrated that similar membranes are good candidates from the viewpoint of lithium ion transport with barriers of 0.2–0.3 eV, which depend on the number of DMSO molecules per lithium atom.

The potential energy surfaces (PES) of the reactions FeAl₁₂ + Н₂ → FeН₂Al₁₂ (1) and CoAl₁₂ + Н₂ → CoН₂Al₁₂ (2) of dissociative addition of an H₂ molecule to Fe- and Co-doped aluminum clusters have been calculated by the density functional theory method. Local minima on the PES in the vicinity of low-lying isomers, intermediates, and transition states have been found, and their structural and spectroscopic characteristics and energies have been calculated. The energies of the successive stages of the catalytic cycle have been evaluated, and the channels corresponding to the minimum energy path of the reactions have been studied. Differences between the structural characteristics and energies of key structures in reactions (1) and (2) have been considered. The results are compared with previous calculations of the PES of hydrogenation reactions performed for related clusters doped with nickel and titanium atoms.

Manganese oxides have been prepared on the surface of carbon fiber by simple methods: coprecipitation of manganese salts of different valence in the presence of fiber as a support or electrodeposition from Mn(II) salt solution on a carbon fiber cathode, in the presence of chitosan including, under oxidation with air oxygen conditions. The obtained samples have been characterized by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Sorption properties of the composites toward As(V) have been studied. The relationships between sorption properties, structure, Mn valence, and manganese oxide surface morphology have been discussed.

Using peroxostannate as a precursor, a composite material based on tin dioxide and carbon black was obtained, in which tin dioxide forms a coating on the surface of carbon black nanoparticles. The synthesized material was characterized by electron microscopy and X-ray powder diffraction analysis, and also the electrochemical characteristics of this material as an anode material for lithium-ion batteries were studied. The material demonstrates good stability and rate performance, which is indicative of the efficiency of the peroxide method for producing promising inexpensive anode materials based on tin dioxide and carbon black.

NiCo/C metal–carbon nanocomposites were prepared using NiCl₂–CoCl₂–polyacrylonitrile (PAN) precursors using IR-laser heating. The characterization of these NiCo/C nanocomposites by X-ray powder diffraction, transmission electron microscopy, and vibration magnetometry showed that the structure and properties of NiCo/C nanocomposites depended on the nickel concentration in the precursor and the synthesis temperature. The magnetization of NiCo/C nanocomposites increased from 0.46 to 17 A m²/kg as the synthesis temperature changed from 500 to 800°С.

Solubility data in the diagonal sections of the quaternary reciprocal 2KCl + Ca(NO₃)₂ → 2KNO₃ + CaCl₂–H₂O system at 25 and 15°C are presented. It has been shown that the quaternary system has no stable diagonal at the studied temperatures, but contains a stable pair of salts, namely, potassium nitrate and calcium chloride. The obtained data can be used to optimize the thermal and concentrational parameters of the synthesis of potassium nitrate from calcium nitrate and potassium chloride.

Computational studies using special software have shown by the example of lanthanide salts that the use of counter-current multistep extraction in chromatography mode provides efficient separation of metals from solutions of their mixtures. Fractions with prescribed purity of separated metals can be obtained by changing the number of stages and cycles of counter-current process and varying the value of dimensionless phase movement time.

The stability constants of copper(II) complexes with nicotinate ion in water–ethanol and water–dimethyl sulfoxide mixtures are determined potentiometrically at 25.0 ± 0.1°C at ionic strength of 0.25 (NaClO4). The stability of the copper(II) nicotinate complex significantly increases with ethanol content in the solution, thus making it possible to control the biologically important process by varying the solvent composition. The increase in DMSO concentration causes a less noticeable rise in stability, with its maximum observed at 0.1 dimethyl sulfoxide mole fractions. A comparative analysis of the findings and stability constants of Cu²⁺ complexes with pyridine-type ligands is carried out. The results are discussed using the solvation thermodynamics approach.

The exchange capacity, degree of exchange, and separation factors of copper(II) and cobalt(II) ions on the H-form of the inorganic ion exchanger “polysurmin”, a silicon phosphorus antimony ion exchanger, and a composite material based on polysurmin were studied as functions of the ion exchanger contact time in the solution. The results were treated in order to assess the rate-limiting step of the process.