Volume 63, Nº 3 (2018)

Hydrated lanthanum fluoride powders, both undoped, and doped with erbium and ytterbium fluorides (to a total content of 6–28 mol %), of the general formula RF₃ · nH₂O (n = 0.30 ± 0.01), crystallizing in the hexagonal system, were obtained by coprecipitation from aqueous solutions of the corresponding nitrates by the interaction with hydrofluoric acid. The dehydration is completed at 380°C. At 600°C, the concentrated solid solution decomposes to precipitate a phase with the structure of orthorhombic YF₃. The efficiency of the upconversion luminescence of the powders, excited at a wavelength of 974 nm, is low.

Various palladium–carbon composites have been manufactured by autoclaving at 170°С to be used as precursors for manufacturing bimetallic particles. The morphology of the manufactured items was comprehensively studied by scanning electron microscopy; the ultrafine metal palladium was found to have particles sizes lying in the range 30–120 nm. The specifics of hydrothermal reduction of gold(III) chloro complexes by palladium–carbon composites at 110°С have been studied. An appreciable increase in gold(III) reduction rate was observed with the use of a palladium–carbon composite relative to the rate observed for ultrafine metallic palladium. Gold is reduced on a palladium–carbon composite to an individual metallic phase.

A new liquid-phase method has been suggested for synthesis of solid electrolytes with lithium conductivity of composition Li_{1 + x}Al_xGe_2–x(PO₄)₃ (x = 0, 0.1, 0.3, 0.5, 0.6, 0.65) with a NASICON structure. The method is based on the use of an alkaline solution of GeO₂ and water-soluble Al(NO₃)₃ · 9H₂O, LiNO₃, and (NH₄)₂HPO₄ salts. The synthesized materials have been characterized by X-ray powder diffraction and impedance spectroscopy. The formation of crystalline Li_{1 + x}Al_xGe_2–x(PO₄)₃ products with a NASICON structure is observed at 750–1000°C depending on the degree of substitution of germanium by aluminum. The effect of final powder annealing temperature and ceramics sintering temperature on the phase composition, density, and conductivity of resulting materials has been studied. The material of composition Li_1.6Al_0.6Ge_1.4(PO₄)₃ produced by sintering the synthesized powder at 900°C exhibits the highest conductivity (3.8 × 10–4 S/cm at a ceramics density of 86%) and the lowest conductivity activation energy (30.5 ± 0.4 kJ/mol in the temperature range 25–250°C).

The crystallochemistry of compounds containing s-metal atoms in the carbon environment has been analyzed using the method of Voronoi–Dirichlet intersecting sectors and polyhedra. The chemical nature of the s metal has been found to affect the characteristics of the Voronoi–Dirichlet polyhedra. It is shown that the volume of Voronoi–Dirichlet polyhedron is practically independent of the coordination number of the s-metal atom.

Crystals of [(UO₂)₂(mal)(Cl)₂(DMA)₄] (mal^2– is malonate ion and DMA is dimethylacetamide) have been synthesized and studied by X-ray crystallography. The key structure units are binuclear island complexes [(UO₂)₂(mal)(Cl)₂(DMA)₄], which belong to the A₂Q⁰²M₆¹ crystal-chemical group (A = UO₂²⁺, Q⁰² = mal^2–, M¹ = Cl^– and DMA) of uranyl complexes. The complexes form a framework through a system of intermolecular nonbonded interactions, which are characterized by means of the Voronoi–Direchlet molecular polyhedron method.

The structure of (C₃H₆N₃)₄Bi₂Cl₁₀ was determined by single crystal X-ray diffraction at room temperature. It crystallizes in the orthorhombic space group Pcmn, with a = 9.430 (1) Å, b = 17.426 (3) Å, c = 19.883(5) Å, V = 3267.3 (11) ų and Z = 4. The structure consists of discrete binuclear [Bi₂Cl₁₀]^4– anions and 3-aminopyrazolium cations. The crystal packing is governed by weak N–H···Cl hydrogen bonds, π–π and electrostatic Cl···Cl interactions. Infrared spectrum is used to gain more information on the title compound. An assignment of the observed vibration modes is reported. The crystal morphology is studied using the BFDH laws. The calculated HOMO and LUMO energies show that charge transfer occur within organic and inorganic molecules. The optical absorption of the zero-dimensional hybrid was also investigated.

The complex formation of lithium thiocyanate with benzo-15-crown-5 (B15C5) was studied. The possibility of formation of both anhydrous and crystal water-containing complexes was demonstrated. The complexes LiB15C5NCS and LiB15C5H₂ONCS were synthesized and characterized by X-ray diffraction and IR spectroscopy.

Samples of the clathrate Na_xSi₁₃₆ were saturated with hydrogen to 100 atm at 25°C in a Sievertstype apparatus and at pressures of 6 and 28 kbar in lentil-type high-pressure apparatuses at 100 and 250°C. X-ray powder diffraction analysis and Raman spectroscopy of the samples quenched after the saturation with hydrogen showed that the phase composition of the clathrates did not change. Heating of the quenched samples to room temperature in a thermal desorption setup produced not hydrogen, but hydrogen-containing gases, as we assumed, silanes. Heating to 650°C leads to decomposition of these compounds to form hydrogen.

The cutting element LiF–LiVO₃–LiKMoO₄–KBr of the quinary reciprocal system Li, K||F, Br, VO₃, MoO₄ was studied by differential thermal analysis. The composition and melting point of the alloy corresponding to a quaternary eutectic were determined (7.0 mol % LiF, 32.0 mol % LiVO3, 47.7 mol % Li2MoO4 + K2MoO4, 12.3 mol % KBr, 410°С).

Phase equilibria in the FeSb₂S₄–FeLa₂S₄ system were studied by physicochemical analysis methods (differential thermal, X-ray powder diffraction, and microstructural analyses and microhardness and density measurements), and the phase diagram of the system was constructed. The formation of quaternary sulfide FeLaSbS₄ melting congruently at 1230 K, an analog of the mineral berthierite FeSb₂S₄, was detected. The X-ray powder diffraction analysis showed that FeLaSbS₄ belongs to the berthierite structural type and crystallizes in the orthorhombic system with the unit cell parameters a = 11.424 Å, b = 14.160 Å, c = 3.782 Å, Z = 4, and space group Pbam.

Iron(III) extraction with trioctylmethylammonium di(2-ethylhexyl)dithiophosphate and di(2- ethylhexyl)dithiophosphoric acid was studied. It was shown that di(2-ethylhexyl)dithiophosphoric acid extracts iron in the form of the complex FeA₂, regardless of the oxidation state of iron in the initial aqueous solution. It was also shown that the iron(III) extraction with trioctylmethylammonium di(2-ethylhexyl)dithiophosphate over a wide acidity range occurs primarily to produce extractable substance (R₄N)FeCl₄; and at pH > 1, iron(II) dialkyldithiophosphate is also extracted into the organic phase. It was established that, in a system with a binary extractant, iron can be efficiently stripped from the organic phase with water or diluted solutions of mineral acids.

Copper(II), silver(I), cobalt(II), nickel(II), zinc(II), manganese(II), and magnesium(II) sorption isotherms on cross-linked sulfoethylated chitosan with the degree of sulfoethylation DS = 0.7 (SEC 0.7) have been plotted for the individual or collective presence of these ions in solution have been constructed. The capacities of the studied sorbents for the studied metal ions have been calculated by processing the sorption isotherms. SEC 0.7 is found to have the greatest affinity to copper(II) and silver(I); their presence almost completely suppresses the sorption of associated metal ions. The Redlich–Peterson model gives the best fit to the sorption isotherms for collectively present metal ions, indicating the chemical inhomogeneity of the sorbent surface.

An easily available fluorescent sensor (L) based on salicylaldehyde has been investigated in this work. Chemosensor (L) was exhibited highly selective and sensitive fluorescence sensing ability for Fe³⁺ over other metal ions in H₂O-DMF solution. The fluorescence quenching response of (L) for Fe³⁺ indcated that (L) can be used as “turn-off” fluorescent chemosensor to selectively detect Fe³⁺. The fluorescent sensor (L) was synthesized by the one pot condensation reaction of 2-[3-(2-formyl phenoxy)propoxy]benzaldehyde and 2-aminobenzenethiol in a 1 : 2 molar ratio and characterized by IR, NMR spectroscopy and elemental analysis.