Vol 63, No 6 (2018)

A method was developed for the low-temperature sol–gel synthesis of one of the most popular components of functional and structural materials—nanostructured yttrium aluminum garnet Y₃A_l5O₁₂—using precursors from the class of alkoxoacetylacetonates produced from the corresponding acetylacetonates. It was determined that increasing duration of heat treatment of yttrium-aluminum-containing xerogen in air to 6 h reduces the crystallization temperature of the Y₃A_l5O₁₂ phase from 920–930 to 750–800°C, which was confirmed by IR spectroscopy and X-ray powder diffraction analysis. The microstructure of nanocrystalline yttrium aluminum garnet obtained at 800°С was studied; it was found that the size of crystallites is 30–40 nm, the size of particles is 30–50 nm, and the size of pores is 20–30 nm. Small-angle neutron scattering demonstrated that, in the powders synthesized at 700–800°C, there is structural ordering of the short-range type, whereas in the nanocrystalline samples heat-treated at a higher temperature (850°С), there is no such ordering.

Nanocrystalline manganese dioxide have been prepared by hydrothermal microwave treatment of mixed solutions of potassium permanganate and 2,4,6-triamino-1,3,5-triazine (melamine) in pH range 0.5–3. Phase and chemical composition and morphology of the samples was studied by XRD, Raman spectroscopy, and SEM. Conditions (solution pH and temperature) for the formation of single phase MnO₂ powders (α-MnO₂, γ-MnO₂, δ-MnO₂, and δ*-MnO₂) under hydrothermal microwave treatment were determined.

BaMoO₄ crystals were synthesized by a 900 W microwave induced plasma process (MIP) for 40, 60, 120 and 140 min. Phase, morphology, vibrational mode and energy gap were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and UV-visible spectroscopy. In this research, the phase and morphology of product were influenced by microwave heating time. The sample processed for 140 min shows spherical particles tetragonal BaMoO₄ phase with size of 200–700 nm in diameter. BaMoO₄ with band gap of 3.35 eV shows a blue emission wavelength at 440 nm.

A method for the preparation of high-purity iron via the chlorination of a mixture containing iron(III) oxide by ammonium chloride with the subsequent decomposition of the intermediate product to iron(III) chloride, its sublimation, and further reduction in a hydrogen flow was proposed. The reaction between ammonium chloride and iron(III) oxide and the thermal decomposition of the ammonium chloride complex were thermogravimetrically studied. The conditions and energetic characteristics of these reactions were determined. The method was tested on iron-containing raw materials. The impurities in the end product of reduction by hydrogen were 0.25%.

Ph₃PC₆H11-cyclo)]⁺[PdBr₃(Dmso)]^– (I) and [Ph₃PBu]⁺[PdCl₃(Dmso)]^– (II) have been synthesized by the reactions of tetrahydrobromopalladic acid with (cyclohexyl)triphenylphosphonium bromide and tetrahydrochloropalladic acid with butyltriphenylphosphonium chloride in water with further recrystallization from dimethyl sulfoxide. [Ph₃PCH₂CH=CHCH₂PPh₃]²⁺[PdCl₄]^2–. Dmf (III) has been synthesized by a similar reaction of tetrahydrochloropalladic acid with butylene-2-bis(triphenylphosphonium) dichloride with recrystallization from N,N-dimethylformamide. According to X-ray diffraction data, P–C bond lengths and CPC angles in cations of complexes I–III variate within 1.778(2)–1.811(4) Å and 106.1(2)°–112.0(2)°, respectively. Dimethyl sulfoxide molecules in anions of complexes I and II are S-coordinated, and Pd–S bonds are 2.2478(14) and 2.2466(6) Å, while Pd–Cl distances in centrosymmetric square anions of complex III are 2.3143(5) and 2.3170(5) Å, and ClPdCl trans angles are 180°. The structural organization of crystals is formed by weak hydrogen bonds C–H...Br, C–H...Cl, and C–H...O.

Structural features of 26 mononuclear octahedral monooxo d²-Re(V) complexes with singly charged oxygen atoms of bidentate-chelating (O,N) ligands (Lⁿ), namely, [ReO(Lⁿ)(L_mono)₃] (where L_mono stands for a monodentate ligand) containing six- and seven-membered chelate rings ReNC₃O and ReNC₄O, are considered. The atoms O(Lⁿ), with one exception, are in the trans positions to ligands O(oxo). In [ReO(OPPh₃)Cl₂(L³⁵)], the trans position to the oxo ligand is occupied by the neutral oxygen atom of ligand OPPh₃. In [ReO(Hal)₂(Lⁿ)(L_mono)] [(L_mono = PPh₃, AsPPh₃, and OPPh₃)] structures, two geometric isomers exist: halide ligands are either in the cis- or in the trans position to each other.

Complexation of iron(II) in aqueous glycine (α-aminoacetic acid) solutions is studied in the pH range 1.0–8.0 at 298.16 K at various ionic strengths (NaClO₄). The stability constants of the resulting complexes go down as the ionic strength of the solution increases. The stability constants of the complexes are determined using the experimental “electromotive force of the system versus pH” curves by iterative fitting of the theoretical oxidation function to the experimental one with the Excel program. The correlation between the stability constants of complexes and ionic strength of the solution is also calculated using the Debye–Hückel equation and SigmaPlot 10.0 software. Statistical analysis of the calculated data is performed with P value of 0.95.

Tris(2,6-dimethoxyphenyl)antimony diazide has been synthesized and characterized by X-ray diffraction. The antimony atoms in four crystallographically independent molecules have a distorted trigonal pyramidal coordination. Axial angles range within 174.57°–178.95°.

The geometrical parameters of the molecular structures of aluminum–chromium and aluminum–molybdenum clusters Al₂Cr₃ and Al₂Mo₃ have been calculated by the OPBE/TZVP density functional theory (DFT) method with the Gaussian09 programL package. It has been found that each of these metal clusters can exist in twenty structural modifications, which significantly differ in stability and geometric parameters. Bond lengths and bond and torsion (dihedral) angles are reported for each of these modifications.

The phase relationships in the subsolidus region of the Li₂MoO₄–K₂MoO₄–MgMoO₄–Sc₂(MoO₄)₃–Lu₂(MoO₄)₃ system have been studied by X-ray crystallography and vibrational spectroscopy. A phase of variable composition Li_0.2K_0.8–yMg_1–xSc(Lu)_{1 + x}(MoO₄)₃ (0 ≤ х ≤ 0.5; 0 ≤ y ≤ 0.3) with a NASICON structure (space group R\(\bar 3c\)) was synthesized by the ceramic route. The phase exhibits high conductivity, which makes it a candidate for use as a solid electrolyte with lithium and potassium ion conductivity. The unit cell parameters were determined, and IR and Raman spectra were interpreted.

The chemical vapor deposition (CVD) of boron-containing films involving the trimethyl borate precursor has been modeled in the ranges of pressures 0.03 ≤ Р, Torr ≤ 760 and temperatures 300 ≤ Т, K ≤ 2000. The CVD diagram of this system was found to feature existence fields of the following phase complexes: В + В₄С, В4С + В₂О₃, С + В₂О₃ + В₄С, С + В₂О₃, С + В₂О₃ + НВО₂, С + НВО₂, С + В₄С, and a В₄С phase.

Phase equilibria in the FeSb₂S₄–FeSm₂S₄ system were studied by physicochemical analysis methods (differential thermal and X-ray powder diffraction analyses and microhardness and density measurements), and the T–x phase diagram of the system was constructed. Intermediate phase FeSmSbS₄ melting congruently at 1255 K was found to form. According to the X-ray powder diffraction data, FeSmSbS₄ crystallizes in the orthorhombic system with the unit cell parameters a = 11.446 Å, b = 14.160 Å, c = 3.800 Å, Z = 4, space group Pnam, ρ_pycn = 4.96 g/cm³, and ρ_X-ray = 5.00 g/cm³. In the FeSb₂S₄–FeSmSbS₄ segment of the phase diagram of the FeSb₂S₄–FeSm₂S₄ system, an unlimited series of solid solutions with an orthorhombic unit cell forms. The isothermal section of the FeS–Sb₂S₃–Sm₂S₃ system at 298 K was constructed. The molar specific heat C_p (T) of FeSb₂S₄ was approximated within the range 300–800 K.

Water–acetone solutions in the AlCl₃–(CH₃)₂CO–H₂O and AlCl₃–(CH₃)₂CO–H₂O–HCl systems were obtained and studied. In both cases, the solution separated into layers to form liquid fractions of lower and higher density. The IR spectra of the fractions were studied. In the light fraction, no AlCl₃ was present, but hydrogen-bonded acetone–water complexes were detected. The spectra of the heavy fraction exhibited a broad band at ~3020–3040 cm^–1 corresponding to the OH groups of water from aluminum hexahydrate. As the solvent is evaporated, the band narrows down, with its position being retained. The IR spectrum of the obtained solid becomes identical to the IR spectrum of the crystal hydrate AlCl₃.(H₂O)₆. The structures and spectral and energetic parameters of Al(H₂O)₆³⁺, Al(H₂O)₆₊₁₂³⁺, Al((CH₃)₂CO)₆³⁺, Al((CH₃)₂CO)₄³⁺, and (CH₃)₂CO.H₂O were calculated by the density functional theory method (B3LYP/6-31++G(d,p)). Relying on the results, an explanation was proposed for the experimentlly observed absence of acetone molecules in the Al³⁺ first coordination shell.