


Vol 63, No 11 (2018)
- Year: 2018
- Articles: 21
- URL: https://journal-vniispk.ru/0036-0236/issue/view/10310
Synthesis and Properties of Inorganic Compounds
Chemical and Phase Transformations during the Synthesis of Cs[MgR0.5P1.5O6] (R = B, Al, Fe) Complex Oxides from Metal Nitrates
Abstract
Cesium-containing complex oxides Cs[MgR0.5P1.5O6], where R = B, Al, or Fe, were prepared from solutions containing H3BO3, metal nitrates, and H3PO4/NH4H2PO4. The chemical and phase transformations occurring during the synthesis of these oxides were elucidated by differential thermal analysis (DTA) and X-ray powder diffraction (XRD. Optimal synthesis parameters were found. The boron compound was found to be formed at 800°C, and the aluminum and iron compounds, at 1200°C. All compounds have the pollucite structure (cubic system, space group I4132). A comparative analysis of the synthesis of complex oxides under study from various precursors that differed from one another in metal and phosphorus chemical species was carried out.



Structure and Crystallization of Glasses in the MnNbOF5–BaF2–InF3 System
Abstract
Glasses of the MnNbOF5–BaF2–InF3 system were prepared. The structure, thermal behavior, and crystallization of these glasses were studied by IR and Raman spectroscopy, differential scanning calorimetry (DSC), X-ray powder diffraction, and microscopy. The \(\rm{NbO}_2\rm{F}_4^{3-}\) and \(\rm{InF}_6^{3-}\) ions form a mixed glass network. Glass crystallization occurs in one or two steps depending on the component ratio. The major crystal phases are Ba3In2F12 and BaNbOF5. The obtainability of transparent crystal-glass samples in MnNbOF5–BaF2–InF3 glasses via heat treatment is shown.



Preparation of Hydrated Strontium Silicates from Silica Hydrogel Isolated from Serpentines and Their Thermal Transformations
Abstract
Interaction between silica hydrogel isolated from serpentines (Mg(Fe))6[Si4O10](OH)8, sodium hydroxide NaOH, and strontium chloride SrCl2 in aqueous medium was studied by DTA and X-ray powder diffraction (XRD). Stirring of the boiling aqueous suspension prepared from these reagents under the atmospheric pressure for 2 h yields hydrated strontium silicate species: Sr3Si2O7 · 4H2O and Sr3Si2O7 · 3H2O or their mixtures, whose heating to 810–825°C is accompanied by some phase transformations: strontium metasilicate Sr3Si3O9 or strontium orthosilicate Sr2SiO4 is formed after bound water is removed in the range 250–350°C, and strontium silicate SrSiO3 is formed at higher temperatures. Sr2SiO4 single phase is observed upon heat treatment to 700–750°C. The optimal molar ratio of the reagents was found to favor Sr2SiO4 formation.



Structure, Magnetic and Photochemical Properties of Fe–TiO2 Nanoparticles Stabilized in Al2O3 Matrix
Abstract
Fe–TiO2 nanoparticles with Fe concentration from 0.24 to 5 wt % were synthesized in a Al2O3 matrix through multiple impregnations from organic solutions of Ti n-butoxide and Fe acetylacetonate. Microstructure, morphology and magnetic properties of the composites were studied using X-ray analysis, transmission electron microscopy, energy-dispersive analysis, Mössbauer spectroscopy and magnetic susceptibility. It was shown that the deposition of the solution with low concentration of Ti n-butoxide leads to the formation of mostly extensive Fe–TiO2 films with a small fraction of individual Fe–TiO2 nanoparticles. On the contrary, the increase of Ti n-butoxide concentration results in the formation of a great number of individual Fe–TiO2 nanoparticles on Al2O3. The size of these particles increases from 2–3 nm to 5–8 nm with the increase of Fe content in the samples from 0.24 to 1.0 (wt %). Mössbauer spectroscopy revealed two types of magnetic ions. The first type of paramagnetic Fe3+ demonstrate spin–lattice relaxation properties while another one substitutes Ti4+ in the TiO2 structure thus forming Fe–TiO2 stabilized particles in the matrix. According to the magnetic data antiferromagnetic and ferromagnetic types of exchange spin coupling occur in Fe–TiO2/Al2O3 composites. The increase of Fe concentration in the composites from 1 to 5 wt % results in the narrowing of the TiO2 band gap from 3.2 to 2.7 eV and shifting the absorption edge in visual spectrum from 350–400 to 450–500 nm.



Manufacture of Magnesium Oxide Nanoparticles Coated with Silica Shells
Abstract
MgO@SiO2 core–shell nanoparticles were manufactured, and a synthetic protocol was developed to prepare MgO nanoparticles where the SiO2 shell thickness was less than 10 nm. The influence of synthesis parameters on the formation of MgO@SiO2 nanoparticles was studied. The fact of a SiO2 shell being formed on the MgO surface was established and the sizes of the thus-prepared MgO@SiO2 nanoparticles were determined by TEM and Fourier-transform IR spectroscopy.



Ytterbium-Containing Oxide Catalysts for Oxidative Dehydrogenation of Hydrocarbons
Abstract
Oxide catalyst samples for the oxidative dehydrogenation (ODH) of alkanes were prepared by heat treatment of precursors, namely, hydrotalcite-related magnesium aluminum double hydroxo salts containing ytterbium, as well as magnesium, aluminum, chromium, vanadium, molybdenum, and niobium in various combinations. Their catalytic activities were studied. Some catalysts were found to have high efficiency in ODH of ethane, propane, and isobutane, increasing the product yield and enhancing the reaction selectivity.



Quantitative Description of Properties of Nickel-Containing Nanocomposites Affecting Their Magnetic Characteristics
Abstract
Multiple regression equations linking properties of nanocomposites synthesized by thermolysis of unsaturated nickel dicarboxylates in an argon medium and magnetic characteristics have been obtained by processing experimental data. The equations obtained enable one to predict the magnetic characteristics on the basis of data on the phase composition of the nanocomposite, the content of nickel, and average diameter of nickel-containing nanoparticles; moreover, information on the effect of characteristics on the magnetic properties can be obtained.



Synthesis and Luminescence of Europium-Containing Compositions Based on Yttrium Oxide and Oxyfluorides
Abstract
By heating the products isolated from an ethyl acetate medium, luminescent europium-containing compositions based on yttrium oxyfluorides and oxide have been synthesized. The concentration of Eu3+ ions in the compositions was from 0.10 to 10 at % of the yttrium content. It has been shown that the (EuхY1–х)nOn–1Fn + 2, (EuхY1–х)OF, (EuхY1–х)2O3, and (EuхY1–х)5O4F7 phases are formed during the synthesis. The luminescence of the compositions is related to the 5D0 → 7Fj electron transitions of Eu3+ ions. It depends on the synthesis conditions, the type of matrix, the position of the Eu3+ ions in the crystal lattice, the excitation wavelength, and other factors.



Nanocrystalline ZnO Obtained by the Thermal Decomposition of [Zn(H2O)(O2C5H7)2] in 1-Butanol: Synthesis and Testing as a Sensing Material
Abstract
The influence of conditions of heat treatment of a solution [Zn(H2O)(O2C5H7)2] in 1-butanol (temperature 125–185°C, treatment times 2, 4, and 6 h) on dispersion and microstructure of the formed nanocrystalline and poorly aggregated zinc oxide, promising component for optoelectronics, including as receptor materials of chemical gas sensors, was investigated. IR spectroscopy showed that the precursor decomposition occurs through the cleavage of the Cβ–Cγ bond of the ligand to form acetone and butyl acetate. It was determined that at the minimum treatment temperature and time (125°C, 2 h) ZnO nanoparticles are nearly spherical, and under hard conditions, rodlike particles are formed. At 125°C (treatment times 4 and 6 h), rodlike particles are organized into dense agglomerates resembling bundles in shape, and at the higher temperatures there is no aggregation of ZnO nanoparticles. The high CO selectivity and sensitivity (4–100 ppm) was revealed for oxide coatings obtained by screen printing using ZnO nanopowders synthesized at 125°C (treatment times 2 and 4 h).



Coordination Compounds
Gas Phase Composition and Vaporization Thermodynamics of Cobalt(II) Pivalate Complexes
Abstract
Vaporization of cobalt(II) pivalate [Co(Piv)2] (1, HPiv = HO2CCMe3) and cobalt(II) oxopivalate [Co4O(Piv)6] (2) complexes has been studied by Knudsen effusion technique in combination with mass-spectral analysis of gas phase composition. The congruent sublimation of the prepared compounds has occurred, it has been accompanied by partial thermal decomposition in the case of complex 1. Saturated vapor over complex 1 has been found to consist mainly of monomeric Co(Piv)2, dimeric Co2(Piv)4, and small amount of tetrameric Co4(Piv)8 molecules, as well as Co4O(Piv)6, CO2, and 2,2,4,4-tetramethylpentanone ones. Saturated vapor over complex 2 contains only Co4O(Piv)6 species. The absolute values of partial pressure and sublimation enthalpies of gas phase components have been calculated.



Monoclinic Low-Temperature Polymorph of Cesium Nitrate
Abstract
A new CsNO3 polymorph with space group P21/c, Z = 4, a = 4.5699(9) Å, b = 11.1871(10) Å, c = 9.1484(18) Å, β = 131.24(3)° has been prepared by crystallization from a mixture of water and DMSO. Flat triangles NO3 are located in the (010) and (020) planes between the layers formed by coordination polyhedra of Cs atoms in the (040) plane. In contrast to the previously known low-temperature polymorph, the new modification is characterized by the crystal equivalence of all Cs and NO3 groups.



Structure and Thermodynamic Stability of Rhenium and Ruthenium Oxoalkoxo Derivatives MxN4 – xO6(OMе)10 (M, N = Re, Ru; x = 4–0)
Abstract
Quantum-chemical calculations of the structure and relative thermodynamic stability of tetranuclear clusters MxN4 – xO6(OMе)10 (M, N = Re, Ru; x = 4–0) including geometric isomers of bimetallic clusters are performed to establish the possibility of replacing Re atoms by Ru atoms while maintaining a cyclic tetranuclear structure. As the initial model, the structure of Re4O6(OPri)10 was chosen which is an almost regular rhombus. The values of the metal–metal and metal–oxygen interatomic distances are calculated, and features of their variation under the transition from mononuclear to heteronuclear clusters and from neutral clusters to anions are discussed. Differences between the relative thermodynamic stability of homometallic and heterometallic tetranuclear clusters, including the geometric isomers of the latter, are discussed.



Complex Formation of Cobalt(II) Octakis(3,5-di-tert-butylphenoxy)phthalocyanine with 2′-(Pyridin-4-yl)-5′-(Pyridin-2-yl)-1′-(Pyridin-2-ylmethyl)-2′,4′-Dihydro-1′H-Pyrrolo[ 3′,4′:1,2][C60-Ih][5,6]fullerene
Abstract
The formation of the donor–acceptor complex of cobalt(II) octakis(3,5-di-tert-butylphenoxy)phthalocyanine with 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-2-ylmethyl)-2′,4′-dihydro-1′Hpyrrolo[3′,4′ : 1,2][C60-Ih][5,6]fullerene (Py3C60) in toluene was studied by chemical kinetics (thermodynamics) and spectroscopy methods in comparison with a similar system based on 4-picoline (Pic). In both cases, the reaction occurred in one step giving donor–acceptor complexes of 1 : 1 stoichiometry, which were characterized by key spectral (UV-vis, IR, 1H NMR) parameters and thermodynamic equilibrium parameters; in the case of reaction with pyridyl-substituted fullerene, full kinetic description was obtained. The stability constants for (Pic)CoPc(3,5-tBuPhO)8 and (Py3C60)CoPc(3,5-tBuPhO)8 are (1.01 ± 0.16) × 104 L/mol (logK = 4.00, ΔG=–22.84 kJ/mol) and (1.84 ± 0.16) × 105 L/mol (logK = 5.26, ΔG=–30.04 kJ/mol), respectively. The obtained results are relevant for the development of new efficient components for photovoltaic cells based on phthalocyanine–fullerene systems.



Theoretical Inorganic Chemistry
Ozone Adsorption and Release by Hexagonal Manganese Clusters (MnAkBi)m · nH2O (A, B = O, SO4, H2SO4; i, k = 0, 1, 2; n = 3–15, m = 3, 6, 12): Quantum-Chemical Modeling
Abstract
Quantum-chemical modeling of the structure, electronic properties, and stability of hexagonal manganese clusters (MnAkBi)m · nH2O (A, B = O, SO4, H2SO4; i, k = 0, 1, 2; n = 3–15, m = 3, 6, 12) has been performed by the density functional theory method with gradient correction (PBE and B3LYP). It has been demonstrated that the hexagonal manganese clusters can react with water to release oxygen and ozone (upon the transition to low-lying excited states, for example, on heating or exposure to light). The release of ozone from the (MnO2)n clusters (n = 3, 6, 12, …) requires the smallest energy input. It has been revealed that the interaction with hydrogen in the gas phase can lead to the adsorption of ozone onto the cluster surface.



Physical Methods of Investigation
A Study of Сu(II) Complexes with Pyruvic Acid Nicotinoyl and Isonicotinoyl Hydrazones by EPR and X-ray Absorption Spectroscopy
Abstract
The composition and structure of the Cu2+ coordination cores in the previously synthesized [CuCl(HNPv)] · H2O, [CuCl(HIPv)] · H2O, [Cu(AOc)(HNPv)], [Cu(AOc)(HIPv)], [Cu(NO3)(HNPv)], and [Cu(NO3)(HIPv)] complexes, where HNPv and HIPv pyruvic acid nicotinoyl and isonicotinoyl hydrazones, respectively, have been determined. The binuclear complex [Cu2(HNPv)2(H2O)2(μ-Cl)] has been synthesized for the first time and characterized by elemental analysis and IR, EPR, and EXAFS spectroscopy. Its dimeric structure has been proved by magnetic susceptibility measurement and EPR.



Thermodynamic Properties and Thermal Expansion of Tm2O3 · 2ZrO2 Solid Solution
Abstract
The isobaric heat capacity of Tm2O3 · 2ZrO2 solid solution was measured by adiabatic calorimetry and differential scanning calorimetry (DSC), and smoothed values of the enthalpy changes, entropy, and reduced Gibbs free energy in the temperature range 8–1200 K were calculated. Thermal expansion was studied by X-ray diffraction in the temperature range 298–1173 K.



Impact of a Supersonic Dissociated Air Flow on the Surface of HfB2–30 vol % SiC UHTC Produced by the Sol–Gel Method
Abstract
A new method to produce ultra-high-temperature ceramic composites under rather mild conditions (1700°C, 30 MPa, treatment time 15 min) was applied to synthesize a relatively dense (ρrel = 84.5%) HfB2–30 vol % SiC material containing nanocrystalline silicon carbide (average crystallite size ∼37 nm). The elemental and phase compositions, microstructure, and some mechanical properties of this material and also its thermal behavior in an air flow within the temperature range 20–1400°C were investigated. Using a high-frequency induction plasmatron, a study was made of the effect of a supersonic dissociated air flow on the surface of the produced ultra-high-temperature ceramic composite shaped as a flat-end cylindrical sample installed into a copper water-cooled holder. On 40-min exposure of the sample to the supersonic dissociated air flow, the sample did not fail, and the weight loss was 0.04%. Although the heat flux was high, the temperature on the surface did not exceed 1400–1590°C, which could be due to the heat transfer from the sample to the water-cooled model. The thickness of the oxidized layer under these conditions was 10–20 μm; no SiC-depleted region formed. Specific features of the microstructure of the oxidized surface layer of the sample were noted.



Physicochemical Analysis of Inorganic Systems
Phase Equilibria in Systems DyCuS2–EuS and Cu2S−Dy2S3−EuS
Abstract
The phase diagram of system DyCuS2–EuS has been first constructed, and the phase equilibria in the Cu2S–Dy2S3–EuS triangle at 970 K have been studied. Compound EuDyCuS3 (1DyCuS2 : 1EuS), space group Pnma, a = 10.1901(3) Å, b = 3.9270(1) Å, c = 12.8468(3) Å, melts incongruently at 1727 ± 7 K according to the reaction: EuDyCuS3solid ↔ 0.17 SS EuS (90 mol % EuS, 10 mol % DyCuS2) + 0.83 liq (42 mol % EuS, 58 mol % DyCuS2), ΔH = 2.9 ± 0.6 kJ/mol; microhardness of the phase is 3080 ± 35 MPa. Compound EuDyCuS3 is transparent in the range 3000–1800 cm–1. In system DyCuS2–EuS, the solid solution (SS) based on EuS extends from 91 to 100 mol % at 1770 K and from 92 to 100 mol % at 1170 K. In γ-DyCuS2, 2 mol % EuS dissolves at 1487 K. The eutectic is formed between compounds DyCuS2 and EuDyCuS3 at 12 mol % EuS, T = 1487 ± 8 K. In system Cu2S−Dy2S3−EuS, 10 secondary systems have been isolated. At 970 K, tie-lines are located between compound EuDyCuS3 and solid solutions based on compounds β-Cu2S, EuS, DyCuS2, β-(DyCu3S3), and EuDy2S4; between DyCuS2 and the solid solution of α-Dy2S3, DyCuS2, and EuDy2S4.



Secant Tetrahedron LiF–KBr–KVO3–LiKMoO4 of the Five-Component Reciprocal System Li,K‖F,Br,VO3,MoO4
Abstract
The secant tetrahedron LiF–KBr–KVO3–LiKMoO4 of the five-component reciprocal system Li,K‖F,Br,VO3,MoO4 was studied by differential thermal analysis (DTA). The composition corresponding to the quaternary eutectic (mol %) was determined to be the following: LiF, 6.0; KBr, 11.4; KVO3, 57.0; Li2MoO4 + K2MoO4, 25.6; the melting temperature: 358°С.



Influence of the Crystallization Temperature and Atmosphere on the Equilibrium Phase Assemblage of Plutonic Rocks of the Monzonite Family
Abstract
The influence of external settings on the mineral assemblage of plutonic rocks is studied. The equilibrium compositions of phases formed during melting–crystallization of quartz monzodiorite are calculated by physicochemical modeling (PCM) methods. It is shown that, by changing the temperature and atmosphere of melt formation, one can change the mineral assemblage of the crystallizing solid phase that can be used in stone casting and in the production of mineral fibers.



Physicochemistry of Solutions
The State of Copper Ions in Aqueous and Aqueous Ammonia Solutions of Copper Acetate
Abstract
Stabilization of Cu2+ ions in aqueous and aqueous ammonia solutions of copper acetate was studied for a wide range of ammonia concentrations. The structure of copper acetate hydrate complexes was shown to markedly change upon dissolution in water. In aqueous solutions, copper is stabilized as strongly bound Cu2+ associates (dimers) in a distorted octahedral environment composed of water molecules and acetate groups oxygen atoms in equatorial positions with strong exchange interaction via acetate groups. In solutions of copper acetate in aqueous ammonia, the concentration of ammonia has a crucial effect on the ordering of Cu2+ ions in associates. At high ammonia concentration, disordered copper tetra-ammoniate associates with the \({d_{{x^2} - {y^2}}}\) ground state are formed, whereas at low ammonia concentration, bulky Cu2+ ion associate structures are generated, with the \({d_{{x^2} - {y^2}}}\) ground state, hydroxyl groups in the equatorial plane, and water molecules in the axial positions.


