Vol 61, No 1 (2016)

The heat capacity of TbVO₄ has been measured by the adiabatic calorimetry (5–346 K) and differential scanning calorimetry (344–859 K) methods. The C_p = f(T) plot has an extreme point (32 K). The thermodynamic properties of the oxide compounds have been calculated from the experimental data. A general equation that describes the heat capacity of terbium orthovanadate as a function of temperature in the range 35–859 K has been derived.

Phase equilibria in the Al–Cu–Fe system alloyed with 5% Cr were studied. Based on the data of X-ray powder diffraction analysis, electron microscopy, and differential thermal analysis, the effect of temperature on i ⇔ d phase transitions in alloys Al₆₅Cu₂₅Fe₅Cr₅ and Al₇₀Cu₂₀Fe₅Cr₅. In the Al–Cu–Fe–Cr system, multiphase structures were detected; these structures are mixtures of quasi-crystalline and approximant phases, the contents and morphologies of which depend on the composition of the initial mixture and the crystallization rate.

The crystals of [UO₂(C₂H₅COO)₂(CO(NH₂)₂)₂] · H₂O (I) and [UO₂(C₂H₅COO)₂(H₂O)₂] · 2C₃H₆N₂O (II), where CO(NH₂)₂ is carbamide, C₃H₆N₂O is ethylenecarbamide, were synthesized and studied by IR spectroscopy and X-ray diffraction. The key structural units of compounds I are II are mononuclear electrically neutral complexes, which belong to the AB⁰¹M₃¹ and AB⁰¹M₂¹ crystal-chemical groups (A = UO2²⁺ B⁰¹ = C₂H₅COO^–; M¹ = C₂H₅COO^– or CO(NH²)² (I), H²O (II)) of uranyl complexes. The factors that affect the “selection” of the coordination number of U(VI) atoms (7 or 8, respectively) in the crystal structures of I and II and, as a consequence, are responsible for different structures of uranium complexes are discussed.

Some methods for the synthesis of copper(II) complexes with 2-(7-bromo-2-oxo-5-phenyl-3H-1,4-benzodiazepin-1-yl)acetohydrazide (Hydr) ([Cu(Hydr)(H₂O)Cl₂]) and products of its condensation with pyruvic acid ([Cu(HydrHPv)(H₂O)Cl₂] and, with alkalization to pH 8, [Cu(HydrPv)₂]) were developed, and the complexes themselves were synthesized. The complexes were characterized by electrical conductivity, magnetic susceptibility, and IR and EPR spectroscopy measurements.

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.

The energies of formation of intramolecular hydrogen bonds (IHB) in unsaturated dicarboxylic acid molecules in aqueous solutions were calculated by the DFT method (B3LYP hybrid functional, 6-31G** basis set) using the GAMESS software, Version 1, May 2013 (R1). The medium effect was taken into account in terms of the Polarized Continuum Model (PCM). In the case of allylmalonic, itaconic, and maleic acids, fairly weak IHB with an energy of 5.8–13.9 kJ/mol were found to form. The enthalpies of formation of acid and normal cobalt and nickel salts of carboxylic acids in aqueous solutions were calculated by the semiempirical PM3 method using the HyperChem 8.0.8 software (Hypercube Inc.). The results indicate that in aqueous solutions, the formation of cobalt and nickel acid salts of allylmalonic, itaconic, and cis,cis-muconic acids is energetically more favorable than the formation of normal carboxylates, which is consistent with experimental data.

Zirconium fluoro complexes with phosphoryl-containing bases (L) have been synthesized by the reaction of a suspension of ZrF₄(dmso)₂ in toluene with an excess of Ph₃PO or Bu₃PO, as well as (Me₂N)₃PO in CH₂Cl₂. The composition and structure of the complexes in CH₂Cl₂ solutions have been studied by ¹⁹F NMR in the temperature range 293–203 K. Phosphine oxides are substituted for dmso to form mainly cis-tetrafluoro species, insignificant amounts of trans-tetrafluoro species, and mer- and fac-[ZrF₃L₃]⁺ complexes. In addition to these species, the reaction with Bu3PO yields the dimeric oxo complex (µ-O)[ZrF₃(Bu₃PO)₂]₂. Hydrolysis of fluoro complexes in CH₂Cl₂ with the use of an NBu₄OH solution in iso-PrOH does not lead to oxo and hydroxo complexes: first, the [ZrF₅L]^– complex is formed, and the final hydrolysis product is ZrF₆^2-. The fine structure of ¹⁹F NMR resonance lines for the zirconium fluoride compounds [ZrF5L]^–, cis- [ZrF₄L₂], dimeric oxo complex, and mer-[ZrF₃L₃]⁺ in organic solvents has been observed for the first time, which makes it possible to reliably identify the composition and structure of the zirconium coordination polyhedron in the complexes under consideration.

Changes in the luminescence characteristics of Tb³⁺ complexes with hydroxybenzoic acids in the series true solution–viscous medium of a water-soluble polymer (WSP)–WSP film have been studied. The existence of oxygen-containing functional groups in WSPs and the possibility of their coordination to Tb3+ ions, as well the viscous medium created by WSPs, are responsible for changes in characteristics of the complexes, such as luminescence intensity and lifetime. Interligand energy transfer (\({E_{{T_1}}}\left( {Lig} \right) \geqslant {E_{{T_1}}}\left( {WSP} \right)\)) in viscous media leads either to an increase or a decrease in luminescence intensity; however, it is increased multifold in films.

The reduction specifics of REE orthovanadates LnVO₄ (Ln = La, Nd, Sm, Dy, Ho, Er, Tm, Yb, and Lu) have been studied using the temperature-programmed reduction (TPR) method. Hydrogen and carbon monoxide were chosen as reducing agents. The reduction temperature is found to depend both on the REE and the reducing agent. REE orthovanadates are reduced in the range 1033–1153 K not forming phases that contain vanadium in intermediate oxidation states. In CO, the reduction temperature is found to be higher than in H₂ for all orthovanadates. TPR data have been used to calculate the activation energies of reduction of REE orthovanadates using the Kissinger equation. The effective activation energies of reduction depend on the REE and the reducing agent and are in the range 41–147 kJ/mol.

A Sm–Sm2Se3 phase diagram has been studied from 1000 K until melting. This system forms three congruently melting compounds: SmSe (ST NaCl, a = 0.6200 nm, T_m = (2400 ± 50) K, and H = 2750 MPa), Sm₃Se₄ (ST Th₃P₄, a = 0.8925 nm, T_m = (2250 ± 30) K, and H = 3350 MPa), and Sm₂Se₃ (ST Th₃P₄, a = 0.8815 nm, T_m = (2150 ± 40) K, and H = 5300 MPa). There are eutectics between Sm and SmSe phases and between SmSe and Sm₃Se₄ phases at 2.5 at % Se, 1300 K and at 54.5 at % Se, 2100 K, respectively. Within the extent of Sm₂₊ Sm₂³⁺ Se4–Sm₂³⁺Se₃ solid solution (ST Th₃P₄), the experimentally determined percentages of Sm₂₊ ions correspond with the values calculated from the formula compositions of samples. The bandgap width for SmSe_1.45 and SmSe_1.48 phases is ΔE = (1.90 ± 0.05) eV.

The ZnGeAs₂–MnAs system is a eutectic-type system as determined by X-ray powder diffraction, DTA, and microstructure observation, with the eutectic coordinates: 61 mol % ZnGeAs₂ mol %, 39 mol % MnAs, and T_m = 816°C. The eutectic is a lamellar eutectic as shown by microstructure examination. A characteristic feature of the system is a small mutual solubility of the components. Precision analysis of diffraction patterns enabled us to refine unit cell parameters for cubic and tetragonal ZnGeAs₂ phases. MnAs in alloys is shown to consist of a hexagonal phase and a orthorhombic phase. ZnGeAs₂ and MnAs alloys are ferromagnets (T_C ~ 320 K). Their magnetization increases in response to increasing MnAs content.

A model was presented for the p–T diagram of a binary system comprising a polymer and a highly volatile component in which there are intermediate nonstoichiometric phases. The most characteristic polythermal and polybaric sections of the spatial p–T–x diagram are considered.

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.