Том 68, № 4 (2023)

Hexagonal tungsten trioxide–base interstitial solid solutions of general formula CoxWO3, where 0.01 ≤ x ≤ 0.09, were prepared hydrothermally. The dopant homogeneity extent was found to depend on рН in the working solution. Interstitial solid solutions with the highest Co2+ concentrations were formed at рН of 2.3. The CoxWO3 samples with a fiber-like morphology with a fiber diameter of ca. 40 nm, which were prepared at рН of 2.3, had the highest specific surface area, equal to 38.6 m2/g. The key parameter for the stability of the CoxWO3 crystal structure appeared to be ammonium ions residing in the hexagonal channels of the crystal structure. When tested as photocatalysts of 1,2,4-trichlorobenzene oxidation under the UV light, the prepared samples showed high chloroarene conversions and low selectivities to yield a wide range of organic compounds, including chlorine-free ones.

Ca1 – 2xBi2xMo1 – xGexO4 solid solutions with a scheelite-like structure (space group I41/a) and the homogeneity range х = 0.0–0.4 were prepared using standard ceramic technology. The unit cell parameter с and unit cell volume increase as the dopant concentration increases due to the changing size of Ca/BiO8 polyhedra. The predominant thermal expansion of Ca/BiO8 polyhedra was inferred from the temperature-dependent unit cell parameters and Raman spectral patterns. The Ca/Bi–O and Mo/Ge–O bond lengths were calculated. The increasing dopant concentration decreases the thermal expansion coefficient of the ceramics and increases the electrical conductivity and activation energy of the complex oxides compared to the matrix compound. The effective oxygen diffusion coefficient is determined.

Heteroleptic compounds of bismuth(III) adopting a new binuclear structural type: hexamethylenedithiocarbamato(HmDtc)-chloride of [Bi2(S2CNHm)4(μ2-Cl)2] (I) and its solvated form [Bi2(S2CNHm)4(μ2-Cl)2]·2CH2Cl2 (II) have been isolated and studied by X-ray diffraction, IR spectroscopy, and simultaneous thermal analysis. Despite the identical chemical composition, the structure of binuclear molecules in I and II differs significantly. In the first case, the noncentrosymmetric molecule includes two nonequivalent moieties of [Bi(S2CNHm)2Cl], which are combined by μ2-Cl ligands to form the [Bi–(μ2-Cl)2–Bi] metallocycle in the butterfly conformation: Bi(1)–Bi(2) 4.0785(5) Å, Cl(1)–Cl(2) 3.936(2) Å. On the contrary, in the solvated form II, the complex is centrosymmetric and four-membered [Bi2Cl2] ring is stabilized in a rhombic configuration: Bi(1)–Bi(1)a 3.9592(9) Å and Cl(1)–Cl(1)a 4.540(4) Å. According to the microprobe method, the main residual substance after the thermolysis of the complexes is microcrystalline Bi2S3 with inclusions of metallic bismuth particles.

To study the electronic and spin properties of single-walled platinum nanotubes, two rows of chiral nanotubes have been calculated by the relativistic method of symmetrized linearized augmented cylindrical waves: Pt(5, n2) with 1 ≤ n2 ≤ 4 and Pt(10, n2) with 1 ≤ n2 ≤ 9 and radii from 2.24 to 7.78 Å. In all tubes, the intersection of the top of the valence band and the bottom of the conduction band with the Fermi level is observed, which is characteristic of compounds with a semi-metallic band structure. The spin–orbit coupling manifests itself as a splitting of nonrelativistic dispersion curves, which can exceed 0.5 eV for near-Fermi bands and decreases upon transition to the internal states of the valence band and nanotubes of larger diameter. The spin densities of states for electrons with spin up and down at the Fermi level are noticeably different, which can be used to create pure spin currents through nanotubes using alternating electrical voltage. The (5, 3) and (10, 7) nanotubes are the most suitable for this.

Phase equilibria in the NaVO3–Na2WO4 two-component system and in the NaCl–NaVO3–Na2EO4 (E = Mo or W) three-component system were studied. The phase assemblages of the NaCl–NaVO3–Na2EO4 (E = Mo or W) three-component systems were analyzed. Differential thermal analysis (DTA) showed that the binary system is a eutectic system and the three-component systems are partitioned by the compound Na3ClEO4 into two secondary triangles, in each of which eutectics were found. The percentages of the components in the ternary eutectics and their melting points were determined. Phase equilibria were described for all elements of the phase diagrams studied in this work. The Na2WO4 crystallization field is represented by α, β, and γ phases, and the Na2MoO4 crystallization field, by δ, γ, and β phases. The smallest crystallization field in the ternary systems belongs to low-melting NaVO3.

Spectrometry, spectrophotometry, pH-potentiometry, and solubility method have been used to study the reactions proceeding in aqueous solutions containing the “metal of life” ion Cu2+ and biologically active substances, succinic acid and (or) one of the amino acids (aminoacetic, glutamic, and aspartic). The general acid protonation constants, composition, and stability constants of homoligand and mixed ligand copper(II) complexes have been determined at ionic strength I = 0.3; for copper(II) succinate of the composition CuC4H4O4⋅2H2O, the solubility constant has been found (logKS = –7.59 ± 0.06).

Samples of monoalkyl and mixed-alkyl phosphine oxides of the hexyl–octyl series were synthesized previously by the Grignard method. Here, the group extraction of rare-earth metals contained simultaneously in their nitrate solutions has been studied using then-synthesized alkyl phosphine oxides. Extraction isotherms for the recovery of the total of lanthanides, scandium, and thorium from nitrate solutions have been obtained. Trihexyl phosphine oxide (THPO) exhibits the highest efficiency under these conditions. Trioctyl phosphine oxide (TOPO) exhibits the best selectivity to heavy-group lanthanides, which makes it useful for the recovery of the heavy-group lanthanide fraction. In addition, scandium and thorium were extracted completely, which in turn indicates the usefulness of phosphine oxides for their extraction. The separation factors have been determined for the entire lanthanides series.

The behavior of the ceramic material Ta4HfC5-30 vol % SiC has been studied under the effect of supersonic flow of dissociated nitrogen, which is necessary to assess the potential application of these materials in oxygen-free gas environments at temperatures >1800°C. It has been found that as a result of heating the surface to ~2020°C in a few minutes there is a decrease to ~1915°C followed by a slow decrease to 188°C. This is probably due to the chemical processes occurring on the surface and the formation of an extremely rough microstructure. The ablation rate has been determined; it has been shown that neither at introduction of the sample into a high enthalpy nitrogen flow nor at sharp cooling (temperature drop to ~880°C in 9–10 s) cracking of the sample or detachment of the near-surface region has been observed. X-ray powder diffraction and Raman spectroscopy data allow us to conclude the complete removal of silicon carbide from the surface layer and the transformation of complex tantalum-hafnium carbide into the nitride.

Two series of cobalt-doped CuGa1 – xCoxSe2 and Cu1 – x/2Ga1 – x/2CoxSe2 chalcopyrites were prepared. Cobalt in part entered the chalcopyrite structure to ensure the appearance of paramagnetic properties, while in part it remained involved in cobalt selenide admixtures. High-temperature quenching forced almost all of the cobalt to enter the crystal structure in the Cu1 – x/2Ga1 – x/2CoxSe2 samples. Significant ferromagnetism appears in the Cu0.9Ga0.9Co0.2Se2 sample, which had the highest cobalt concentration, in particular at room temperature.