Showing papers in "Russian Journal of Inorganic Chemistry in 2016"

Au–Cu Phase Diagram

Abstract: Phase equilibria have been extrapolated to low temperatures, and a condensed phase diagram has been plotted for the Au–Cu system to be consistent with the third law of thermodynamics.

Solvent and substitution effects on the structure and properties of a half-sandwich complex of vanadium with a terminal borylene ligand: Theoretical study

Abstract: The structures and properties of a terminal borylene vanadium complexes CpV(CO)3(BNH2) were explored using theoretical methods. The density of states (DOS) was beneficially used to analyze the main features of electronic structure. The influence of solvent on the structural parameters, frontier orbital energies and wavelength absorption maxima (λmax) of this structure was studied. These calculations were performed in different solvents, i.e. cyclohexane, dichloromethane, tetrahydrofuran, chlorobenzene, and chloroform, utilizing the self-consistent reaction field (SCRF) theory. Also, substituent effect in CpV(CO)3(BNR2) complexes on the structure and properties was investigated.

Behavior of HfB2-SiC (10, 15, and 20 vol %) ceramic materials in high-enthalpy air flows

Abstract: HfB2–SiC ceramic samples containing 10, 15, and 20 vol % silicon carbide were prepared by spark plasma sintering. The samples were characterized by X-ray powder diffraction, SEM, and other methods. Their densities and calculated porosities were determined. The behavior of the materials under heating by a subsonic dissociated air flow was studied on a VGU-4 high-frequency inductive plasmatron. The average surface temperatures of the 10 and 15 vol % SiC samples were shown to increase up to 2550–2675°C during heating, due to the generation of surface localities having temperatures of 2600–2700°C (the initial surface temperature was ~1700–1900°C) and the progressive growth of these regions in area. The overall time during which the average surface temperatures of these samples were higher than 2000°C, was about 31–32 min. For the 20 vol % SiC sample, heat removal (when the sample touched a water-cooled holder) was shown to influence the surface temperature and surface temperature distribution. The variation in gas-phase composition over the central area of the sample surface during an experiment was studied using emission spectroscopy. Explanations are proposed to the variation of boron and silicon concentrations in the course of exposure to high-enthalpy flows. The elemental and phase compositions were determined and the microstructures were studied on the surface and sections of samples after long-term (~40-min) exposure to high-enthalpy air flows.

[Co(solv) 6 ][B 10 H 10 ] (solv = DMF and DMSO) for low-temperature synthesis of borides

Abstract: The synthesis and structure of complexes [Co(solv)6][B10H10] (solv = DMF and DMSO) have been reported. Both complexes have been prepared in a high yield by the reaction between cobalt(II) salts and closo-decaborates Cat2[B10H10] in the corresponding solvent. The complexes have been characterized by elemental analysis, IR and UV spectroscopy, X-ray powder diffraction, and X-ray crystallography. The thermal properties of the compounds have been studied in the temperature range 20–600°C under argon. The conditions to form cobalt borides have been determined based on the results of thermal analysis, subsequent annealing of the complexes in various conditions, and analysis of IR spectra of the resulting thermolysis products.

Nickel(II) complexes with boron cluster anions [B n H n ]2– (n = 10, 12) and azaheterocyclic ligands L (L = Bipy, Phen, BPA, and DAB)

Abstract: The effect of the nature of azaheterocyclic ligands L (L is 1,2-diaminobenzene, 2,2’-bipyridyl-amine, 2,2’-bipyridyl, or 1,10-phenanthroline) on the composition and structure of nickel(II) coordination compounds with the [BnHn]2– anions (n = 10, 12) has been studied. Conditions to isolate complexes of general formulas [NiL2(H2O)2][BnHn] and [NiL3][BnHn] have been found. The structures of [Ni(DAB)2(H2O)2][B10H10] · H2O, [Ni(BPA)2(H2O)2][B10H10] · 3H2O, [Ni(Bipy)3][B10H10], [Ni(Bipy)3][B10H10] · 3CH3CN · 0.5H2O, [Ni(Phen)3][B10H10] · 4DMF · 0.32H2O[Ni(Phen)3][B12H12] · 1.5DMF · 0.25H2O, and [Ni(Phen)3](Et3NH)[B10H10]1.5 · 1.75CH3CN have been determined by X-ray diffraction. Structural features of the complexes including intermolecular contacts of different elements of the structures are discussed.

Substituent effect on the structure and properties of dialumene

Abstract: In this work, we report a theoretical study on molecular structure, and electronic properties of dialumene (ArAl = AlAr, Ar = aryl) and substituted dialumene. The effects of the substituent groups on the structure, electronic properties, ionization potential (IP), electron affinity (EA), and reorganization energy were studied. Theoretical calculations were carried out by density functional theory (DFT) using the B3LYP hybrid function combined with the 6-311 + G(d) basis set. The most intensity electronic transition energy and oscillator strength of molecules were calculated by time-dependent density functional theory (TD-DFT) and shows λmax blue-shifted in withdrawing electron substituents. Quantum theory of atom in molecules was used for explain of AlAl and AlC bonds in all molecules.

Preparation of nanostructured thin films of yttrium iron garnet (Y3Fe5O12) by sol–gel technology

Abstract: The synthesis of hydrolytically active heteroligand coordination compounds [M(C5H7O2)3‒x (C5H11O i ) x ] (M = Fe3+ and Y3+) using iron and yttrium acetylacetonates has been studied. The gel formation kinetics in solutions of these compounds upon hydrolysis and polycondensation has also been studied. Thin films of a solution of these precursors have been applied to polished sapphire substrates by dip coating technology. The crystallization of nanostructured yttrium iron garnet (Y3Fe5O12) films during heat treatment of xerogel coatings under various conditions has been studied. How the phase composition, microstructure, and particle size depend on the synthesis parameters has been recognized.

Liquid-phase synthesis and physicochemical properties of xerogels, nanopowders and thin films of the CeO 2 –Y 2 O 3 system

Abstract: Low-agglomerated xerogels, ultrafine oxide powders with particle sizes of 12–20 nm, and uniform thin films with particle sizes of 8–14 nm are prepared in the CeO2–Y2O3 system using liquid-phase low-temperature methods, namely via coprecipitation of hydroxides and cocrystallization of salts, sol—gel technology. A comparative characterization of the prepared xerogels and nanopowders is performed using a set of physicochemical analytical methods. A dependence of phase composition, microstructure, and particle size on synthetic parameters is elucidated.

Lithium isotope effects in extraction of lithium chloride by benzo-15-crown-5 in the 1,1,7-trihydrododecafluoroheptanol–water system

Abstract: The extraction characteristics of the 1,1,7-trihydrododecafluoroheptanol water system have been studied for lithium chloride as the salt to be extracted and benzo-15-crown-5 as the extracting agent, as well as blank extraction of lithium chloride in this system. Single-stage lithium isotope separation factors (a) have been measured at various lithium chloride concentrations in water, and the isotope effect has been multiplied by extraction chromatography. The value of a for the Li6–Li7 pair was 1.024. The light lithium isotope is concentrated in the organic phase.

Extraction of rare earths and scandium by 2-phosphorylphenoxyacetic acid amides in the presence of ionic liquids

Abstract: The distribution of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc between aqueous solutions of their salts and solutions of 2-phosphorylphenoxy acid amides in dichloroethane containing an ionic liquid (1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide) have been studied. Metal ion extraction has been found to increase considerably in the presence of this ionic liquid in the organic phase. The stoichiometries of extractable complexes have been determined. The influence of aqueous HNO3 concentration and of the nature of extractant and ionic liquid on the efficiency of REE(III) and scandium(III) recovery to the organic phase has been considered.

Preparation of MB2/SiC and MB2/SiC-MC (M = Zr or Hf) powder composites which are promising materials for design of ultra-high-temperature ceramics

Abstract: This survey shows the prospects of studies targeted at preparing MB2/SiC and MB2/SiC-MC (M = Zr or Hf) nanosized composite powders for use in the manufacture of ultra-high-temperature ceramics (UHTCs) and antioxidant protective coatings on Cf/C and Cf/SiC composites. The survey considers the specifics of various preparation methods, including sol-gel technology or precipitation followed by borothermic/ carbothermic reduction, self-propagating high-temperature synthesis (SHS), specifically variants combined with mechanochemical activation or spark plasma sintering (SPS), chemical modification of ZrB2(HfB2) powders with polycarbosilane followed by pyrolysis, and dispersion of appropriate ceramics with the stabilization of the slurry. The elemental and phase compositions, particle sizes, microstructures, and some other characteristics of the products reported in the related literature are summarized.

3D model of the T–x–y diagram of the Bi–In–Sn system for designing microstructure of alloys

Abstract: The published experimental and calculated data (binary systems, x–y projection of the liquidus, table of invariant reactions with the liquid phase, and one isothermal and two polythermal sections) were used for constructing a spatial computer model of the T–x–y diagram of the Bi–In–Sn system that was supplemented with the regions of the decomposition of the compound Bi m In n and the polymorphic transformation of tin. It was determined that the T–x–y diagram comprises 173 surfaces and 74 phase regions. Using the model for analyzing the material balances of phases and their microstructural components at all the stages of crystallization was demonstrated.

Silicon- and carbon-based anode materials: Quantum-chemical modeling

Abstract: With the aim of searching for promising anode materials for lithium-ion batteries, we performed quantum-chemical modeling of the structure, stability, and electronic properties of silicon-coated carbon nanotubes, silicon rods, and silicon carbide fibers by the density functional theory method including gradient correction and periodic boundary conditions. It has been demonstrated that nanotubes poorly hold silicon, whereas silicon firmly adheres to the SiC surface. Silicon rods are more favorable than clusters and have the stability close to that of the crystal. The band gap in the rods is close to zero. Silicon carbide can be transformed into a conductor by doping with nitrogen.

Study of isotope effect upon lithium iodide complexation with benzo-15-crown-5 in water–chloroform extraction system

Abstract: Extraction characteristics of chloroform–water system in lithium iodide extraction with benzo-15-crown-5 (B15C5) were studied. The complexation of the crown ether with LiI in organic phase was shown by IR spectroscopy. Isotope effect multiplication was performed by extraction chromatography technique. The magnitude of isotope separation factor (α) for 6Li-7Li pair was 1.017. The light lithium isotope is concentrated in organic phase.

Phase diagram of the NaF–CaF2 system and the electrical conductivity of a CaF2-based solid solution

Abstract: The phase diagram of the NaF–CaF2 system was studied by thermal analysis and X-ray powder diffraction analysis with the determination of the chemical composition. The system was found to be of the eutectic type. A narrow range of the existence of solid solution Ca1–xNaxF2–x was established. The NaF solubility reaches a maximal value of x = 0.035 at 1200 ± 50°C (the temperature at which there is a diffuse phase transition in fluorite). At 920 ± 25°C, the NaF solubility reaches a minimum (<0.4 mol %) and increases again to 2.2 ± 0.2 mol % at a eutectic temperature (818°C). The ionic conductivity increases by three orders of magnitude after adding NaF to CaF2.

Influence of the composition of [Ti(OC 4 H 9 ) 4 – x (O 2 C 5 H 7 ) x ] complexes and hydrolysis conditions on the synthesis of titania by sol–gel technology

Abstract: The influence of the coordination sphere of [Ti(OC4H9)4–x (O2C5H7) x ] complexes, concentration in solution, and the ratio n(H2O)/n(Ti4+) on the hydrolysis and polycondensation kinetics of the complexes, the stability of the resulting gels, the thermal behavior of then-formed xerogels, the shift of anatase–rutile phase transition temperature, and the microstructure of the product, was determined.

Specifics of reactions of cerium sulfate and europium sulfate with hydrogen

Abstract: Reactions of cerium sulfate and europium sulfate with hydrogen have been studied. Diagrams showing the evolution of phase composition of the polycrystalline products of reaction between europium sulfate and hydrogen are constructed. The reaction of Ce2(SO4)3 with hydrogen at 600°С consecutively yields Ce2O2S and Ce2O3 phases. At 800°С the batch is >95 mol % Ce2O3. At 480-500°С, a single-phase sample of EuSO4 is prepared; at 600-1000°С, Eu2O2S is prepared; and at 1050°С, the batch is >95 mol % Eu2O2S and up to 5 mol % Eu2O3. Atomic-force microscopy shows that europium sulfate grains, which represent agglomerates of particles 10-20 μm in size, are degraded upon reaction with hydrogen into individual ovalshaped particles sized 40-60 × 130-200 nm.

Structural features of monomeric octahedral d 2-rhenium(V) monooxo complexes with oxygen atoms of bidentate-chelating acido (O,O)-ligands

Abstract: The structural features of 39 mononuclear octahedral d 2-rhenium(V) monooxo complexes (I–ХХХIХ) with oxygen atoms of bidentate-chelating (O,O) acido ligands (Lig) are considered. In 21 complexes (I–ХХI), the O(lig) atoms are both in trans and cis positions to oxo ligands. In the other 18 complexes (XXI–XXXIX), both O(lig) atoms are in cis positions to the O(oxo) ligands.

Preparation of HfB2/SiC composite powders by sol–gel technology

Abstract: 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.

Synthesis of cerium orthophosphates with monazite and rhabdophane structure from phosphoric acid solutions in the presence of hydrogen peroxide

Abstract: It has been proposed to conduct the synthesis of cerium(III) orthophosphates by reacting cerium(IV) compounds with hydrogen peroxide in the presence of concentrated orthophosphoric acid at ambient temperature. It has been shown that the reaction of H2O2 with CeO2 suspensions in H3PO4 medium produces CePO4 · xH2O (rhabdophane structure), while that with CeO2 solutions in concentrated H3PO4 results in CePO4 (monazite structure).

Crystal Structures of α- and β-SrCeCuS3

Abstract: The crystal structure of SrCeCuS3, a complex sulfide synthesized for the first time, has been solved using X-ray powder diffraction data. The crystals are orthorhombic, space group Pnma. SrCeCuS3 has two polymorphs: the high-temperature phase of Ba2MnS3 structural type (a = 8.1393(3) A, b = 4.0587(2) A, c = 15.9661(2) A) and the low-temperature phase isostructural to BaLaCuS3 (a = 11.1626(2) A, b = 4.0970(2) A, c = 11.5307(1) A). The incongruent melting temperature and enthalpy of SrCeCuS3 are, respectively, 1486 ± 3 K and 13.4 ± 1.5 J/g.

The effect of synthesis conditions on the structure of compounds formed in the Dy2O3–TiO2 system

Abstract: Crystallization and phase transition processes taking place in the Dy2O3–TiO2 system during the isothermal annealing of the precursors synthesized by co-precipitation were studied. The phase composition of the obtained powders is determined by not only the chemical composition of the precursor (Dy2O3: TiO2 ratio) and annealing temperature but also by the procedure of precursor synthesis determining the uniformity of Dy and Ti distribution in the precursor precipitate. Higher homogeneity of precursor particles provides the formation of almost single-phase nanocrystaline dysprosium titanate (Dy2TiO5, Dy2Ti2O7) powders at annealing temperatures of 800–1000°C.

Quantum-chemical study of the structure and magnetic properties of mono- and binuclear Cu(II) complexes with 1,3-bis(3-(pyrimidin-2-yl)-1 H -1,2,4-triazol-5-yl)propane

Abstract: On the basis of X-ray crystallographic data on molecular copper complexes with 1,3-bis(3-(pyrimidin-2-yl)-1H-1,2,4-triazol-5-yl)propane, quantum-chemical optimization of their equilibrium structure has been performed by the density functional theory method with subsequent analysis of the electron density distribution by Bader’s atoms in molecules method and g-factor anisotropy calculation. The topological parameters of electron density at the Cu–N bond critical points have been considered, and the bond energies have been estimated using the Espinosa equation. A phenomenon of variable coordination of nitrate ions with Cu(II) ions in the inner coordination sphere of the mononuclear copper complex with 1,3-bis(3-(pyrimidin-2-yl)-1H-1,2,4-triazol-5-yl)propane has been revealed. The contributions of different components to the gfactor anisotropy have been analyzed in the framework of the gauge-independent atomic orbital method. The largest contribution to the g-factor is made by the orbital (Zeeman) and spin–orbit components accounting for very high averaged g-factor values of 2.1413 and 2.5636 for the doublet state of the mononuclear complex and the triplet state of the binuclear complex, respectively.

Synthesis of nanosized iron(III) oxide and study of its formation features

Abstract: Nanosized iron(III) oxide has been obtained by thermolysis of iron(III) acetylacetonate using diphenyl ether as a dispersion medium. It has been shown that increase in thermolysis temperature from 180 to 250°C allows one to half the average size of Fe2O3 nanoparticles. The introduction of surfactant into dispersion medium also leads to decrease of the average size of particles down to 4 nm. The phase composition of the prepared nano-Fe2O3 has been established, the possibility to reduce nano-Fe2O3 into iron metal has been shown by temperature-programmed reduction

Tris(4-fluorophenyl)antimony dicarboxylates (4-FC 6 H 4 ) 3 Sb[OC(O)R] 2 (R = C 10 H 15 or cyclo -C 3 H 5 ): Synthesis and structure

Abstract: Tris(4-fluorophenyl)antimony dicarboxylates (4-FC6H4)3Sb[OC(O)R]2, where R = C10H15 (I) or cyclo-C3H5 (II), have been synthesized by the reaction between tris(4-fluorophenyl)antimony and adamantanecarboxylic or cyclopropanecarboxylic acids in ether in the presence of tert-butyl hydroperoxide with a high yield. The antimony atoms in complexes I and II have a distorted trigonal bipyramidal coordination to the carboxylate ligands in axial positions (OSbO angles are 174.02(10)° (I) and 176.53(5)° (II)). The Sb-O and Sb-Ceqv bond lengths are 2.120(3), 2.121(2), and 2.110(3)-2.117(3) A (I), 2.147(1), 2.122(1), and 2.120(3)-2.123(2) A (II). Molecules contain intramolecular contacts between the antimony atom and the carbonyl oxygen atom (2.740(3), 2.867(4) A (I); 2.694(3), 2.773(4) A (II)). The structural organization in a crystal of complex I is due to weak intermolecular hydrogen bonds H···F (2.42-2.66 A). Complex II involves the intermolecular contacts H···F (2.63 A) and H···O=C (2.50 A).

Structural and phase transformations and hardness of ceramics produced by high-temperature zirconium nitriding

Abstract: Resistive heating of zirconium in a gaseous nitrogen atmosphere yields ceramics based on zirconium nitride with a heterophase structure. X-ray powder diffraction analysis determined the compositions of phases of the synthesized ceramics. The surface of the material consists of zirconium nitride close in composition to ZrN. In the bulk of the materials, in shallower layers, a nitrogen-deficient nitride phase forms, and in deeper layers, a phase of solid solution of nitrogen in zirconium does. The hardness of ceramics based on heterostructures of the type Zrsolid solution/ZrN1–x/ZrN was studied. Changes in the structure and phase composition during high-temperature nitriding of zirconium foil at 1500 and 2400°C were described.

NiCo/C nanocomposites: Synthesis and magnetic properties

Abstract: 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.

Preparation of nanostructured titania thin films by sol–gel technology

Abstract: 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.

Thermal decomposition features of calcium and rare-earth oxalates

Abstract: Thermal decomposition of Ln2(C2O4)3 · 9H2O concentrate (Ln = La, Ce, Pr, Nd) in the presence of CaC2O4 · H2O was studied by X-ray diffraction, thermogravimetry, and chemical analysis. Annealing at temperatures above 374°C in the absence of calcium oxalate gives rise to the solid solution of CeO2-based rare-earth oxides. Calcite CaCO3 is formed in the presence of calcium oxalate at annealing temperatures above 442°C, which impedes the formation of lanthanide oxide solid solution and favors crystallization of oxides as individual La2O3, CeO2, Pr6O11, and Nd2O3 phases. An increase in temperature above 736°C is accompanied by decomposition of calcium carbonate to give rise to an individual CaO phase and an individual phase of CeO2-based lanthanide oxide solid solution.

Migration of lithium ions in a nonaqueous Nafion-based polymeric electrolyte: Quantum-chemical modeling

Abstract: 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.