Vol 70, No 11 (2025)

Interaction of β-sialons Si₅AlON₇ and Si₄Al₂O₂N₆ with a boron oxide was studied. Boron oxide was introduced in the form of boric acid, the acid content was set up at 0.5wt.% and 5.0wt.%. Samples were sintered at 1650°C in the stream of N₂ for 2h. It was found that all the samples showed higher densities against those for samples sintered with no aids, however, the densities were still lower as compared to theoretical levels. In most cases disproportionation of the basic phase into phases enriched with aluminum (Si₃Al₆O₁₂N₂) and silicon (Si₂N₂O) occurred. Moreover, when Si₄Al₂O₂N₆ was sintered with an addition of 0.5wt.% of boric acid, a noticeable amount of SiO₂ was also formed. Sintering of Si₅AlON₇ with an addition of boric acid did not lead to sufficient changes in microhardness and bending strength. In contrast, sintering of Si₄Al₂O₂N₆ sintered with an addition of 0.5wt.% of boric acid resulted in an increase in bending strength by ~14%, however, an addition of 5.0wt.% of boric acid caused a decrease in hardness by ~9% and a drop in bending strength by ~36%.

The formation process of SnO nanosheets was studied using the direct chemical precipitation, employing tin(II) chloride as the tin source and sodium hydroxide as the base. The obtained powder was characterized in terms of its crystalline structure and microstructure using X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Spectral characteristics were examined by infrared (IR) and Raman spectroscopy, and thermal behavior was analyzed using simultaneous thermal analysis (TGA/DSC) in an air flow. It was established that the synthesized SnO is resistant to oxidation at temperatures up to 250°C. According to XRD data, the product formed has a tetragonal crystal lattice corresponding to tin monoxide, with an average coherent scattering region (CSR) size of 21.7 ± 1.3 nm. SEM and AFM analyses revealed that the powder possesses a hierarchically organized microstructure consisting of nanoplates with a thickness of 26.2 ± 2 nm and lateral dimensions ranging from 0.6 to 4.3 μm. The work function of the material's surface was estimated using Kelvin probe force microscopy (KPFM) and found to be 3.79 ± 0.02 eV.

Solid solutions based on yttrium iron garnets containing both bismuth and cerium ions in the crystal lattice were obtained for the first time using gel combustion with polyvinyl alcohol as fuel. Substitution of Ce³⁺ ions for yttrium is 0.15 formula units, while substitution with Bi³⁺ is 0.7 and 1.0 formula units. The gels formed during the synthesis were studied using FTIR spectroscopy, and the main functional groups involved in gel structure formation were identified. A study of the magnetic properties of Y_3-x(CeBi)_xFe_3.5Ga_1.5O₁₂ solid solutions allowed us to establish the dependence of the specific magnetization, average magnetic moment, and magnetic ordering temperature on the bismuth and cerium ion content in the garnet.

An efficient two-stage method has been developed for the synthesis of perhalogenated monohydroxy derivatives of the closo-decaborate anion with the composition [2-B₁₀X₉OH]^2– (X = Cl, Br). The method involves complete halogenation of the boron framework in the initial DMF-containing derivative [2-B₁₀H₉OCHNMe₂]^– by its reaction with sulfuryl chloride (SO₂Cl₂) or elemental bromine (Br₂), followed by hydrolysis of the obtained perhalogenated derivatives [2-B₁₀X₉OCHNMe₂]^– (X = Cl, Br) with hydrazine monohydrate (N₂H₄·H₂O). This synthetic approach allows for the production of the target compounds with high yield (80–85%) and high purity, as confirmed by a range of physicochemical analysis methods (multinuclear NMR spectroscopy on ¹¹B, ¹H, and ¹³C nuclei, IR spectroscopy, and elemental analysis). The structures of the [2-B₁₀X₉OCHNMe₂]^– and [2-B₁₀X₉OH]^2– anions were determined by single-crystal X-ray diffraction analysis.

Hydride phases based on TiCr alloys with the hexagonal C14 Laves phase structure, doped with various d-metals, were synthesized. Using X-ray diffraction, it was found that the samples contain a hydride phase with an expanded lattice of the C14 structure and a face-centered cubic lattice known in the literature. The discovered face-centered cubic hydride phase is stable under normal conditions, and after hydrogen desorption, its lattice transforms into a body-centered cubic one. The lattice expansion of hydrides of TiCr alloys of both structural modifications correlates with the lattice volume effects of individual hydrides of the metals constituting the alloy components.

Crystal chemical analysis of naphthalene-1-, naphthalene-2-, and anthracene-9-carboxylate-containing complexes of 3d metals was performed within the framework of a stereoatomic model of crystal structure using the characteristics of Voronoi-Dirichlet polyhedra. The types of coordination of naphthalene-1-, naphthalene-2-, and anthracene-9-carboxylate anions with respect to 3d metals are considered. The influence of the type of coordination on the characteristics of connections M–O in crystal structures is revealed. The 18-electron rule is used to quantify the electron-donating ability of naphthalene-1-, naphthalene-2-, and anthracene-9-carboxylate anions with respect to 3d metals, which decreases steadily from left to right. With respect to two-row 3d metal ions, correlations have been established between the electron-donating ability of oxygen atoms of naphthalene-1-, naphthalene-2- and anthracene-9-carboxylate ions and the group number in which the 3d metal is located.

A series of the 3d-row transition metal complexes was synthesized on the base of o-aminophenol АРН₂^N₂Ph augmented by azo-fragment: bis-o-iminobenzosemiquinonate derivatives (imSQ^N₂Ph)₂Ni (1), (imSQ^N₂Ph)₂Cu (2), as well as mixed-ligand compound (imSQ^N₂Ph)(AP^N₂Ph)Co (3) (where imSQ^N₂Ph and AP^N₂Ph are radical anion and dianion redox-forms of ligand АРН₂^N₂Ph, correspondingly). The molecular structure of ligand АРН₂^N₂Ph and complexes 1·C₇H₈, 2·C₇H₈ and 3·C₇H₈ was determined using x-ray diffraction analysis (CIF files CCDC Nos 2444549-2444553, correspondingly). The planar coordination environment of metal center caused the mutual planar displacement of frontier orbitals HOMO and LUMO, that is why low-energy charge transfer "ligand-to-ligand" is implemented in compounds 1-3, corresponding the light absorption in the IR-region. Obtained metal complexes are characterized by rich set of redox states, predominantly provided by redox-active nature of ligands. The compounds of nickel(II) 1 and cobalt(III) 3 are volatile and distinguished by high thermostability and completeness transfer into the vapor phase, that is the favourable factor for the design of optoelectronic devices based on them using the vacuum deposition method.

New photosensitizers based on cationic porphyrins with an extended π-system have been synthesized. The synthetic strategy involves the use of the Sonogashira cross-coupling reaction to form a conjugated π-system of the macrocycle. The obtained compounds exhibit an absorption peak at 660 nm with an extinction coefficient of ~60 000 M^–1 cm^–1; the singlet oxygen quantum yield and the 1-octanol/water partition coefficient were also determined. Absorption in the near-infrared region allows considering the obtained compounds as potential photosensitizers for photodynamic therapy.

The electronic structure of single-walled chiral GaN (8, n₂) nanotubes, where n₂ = 1–7, has been investigated using the nonempirical relativistic augmented cylindrical wave method. It is established that all systems are semiconductors with a band gap of 1–2 eV. The spin-orbit splitting amounts to 3–13 meV for the valence band top and 1–10 meV for the conduction band bottom. The highest spin selectivity efficiency is observed in (8, 1) and (8, 2) nanotubes, where dominant α-transport and high spin-orbit splitting (>10 meV) create optimal conditions for spin filters.

Heat capacity of PrZnAl₁₁O₁₉ with magnetoplumbite structure has been measured by relaxation, adiabatic and differential scanning calorimetries in the temperature range 2–1848 K. Temperature dependences of entropy, enthalpy change and derived Gibbs energy were calculated based on the smoothed heat capacity values. Enthalpy of formation from binary oxides and standard enthalpy of formation at 298 K were estimated from enthalpy of dissolution in lead borate melt measured using the drop-solution calorimetry at 1073. To determine the probability of the decomposition of PrZnAl₁₁O₁₉ into binary oxides, the temperature dependence of the Gibbs energy of the solid-phase reaction in the temperature range of 298–1800 K was estimated.

Using the example of ternary systems, the need for a clear identification of invariant phase transformations is discussed. It has been shown that the task of clearly and unambiguously distinguishing four-phase reactions is becoming more and more urgent, for example, in cases of polymorphism of reagents, compounds decomposition or formation, liquid immiscibility, in contrast to the currently used schematic, incomplete classification according to the principle: eutectic, peritectic, all other reactions. A nomenclature of phase transformations (examples shown on isobaric phase diagrams of ternary systems) is proposed, which helps to differentiate such transformations by the type of phase reactions and better understand the processes occurring in the system, as well as more clearly present the results of experimental investigations of the studied system. The obtained results can be used in the construction of phase diagrams of ternary systems calculating thermodynamically, studying experimentally, and preparing for computer modeling.

Substitution solid solutions Zn_2-2xNi_2xSiO₄ (willemite structure), Ni_2-2yZn_2ySiO₄ (olivine structure) and Ni_1-zZn_zO (rock salt structure) were synthesized by solid-phase synthesis in air, and their extents were determined. Phase equilibria in the NiO-ZnO-SiO₂ system in the subsolidus region were revealed based on the phase composition of the binary systems NiO-ZnO, ZnO-SiO₂, NiO-SiO₂, control points and parameters of the unit cells of solid solutions. It has been established that the ternary system NiO-ZnO-SiO₂ is divided by conodes into seven elementary fields. Phase equilibria in the NiO-ZnO-SiO₂ system is determined by the quasi-binary equilibrium of the boundary compositions of the Zn_2-2xNi_2xSiO₄ (x = 0.10) and Ni_2-2yZn_2ySiO₄ (y = 0.25) solid solutions and the conodes connecting these compositions with the Ni_1-zZn_zO solid solution, as well as the conode connecting the boundary composition of the Ni_1-zZn_zO (z = 0.4) solid solution with Zn₂SiO₄.

This paper presents a theoretical and experimental study of the three-component reciprocal system Na⁺, Sr²⁺∥F^–, MoO₄^2–. A model for dividing the square of compositions into simplexes is presented and a variant with three phase triangles NaF–SrF₂–SrMoO₄, NaF–2NaF·Na₂MoO₄–SrMoO₄, 2NaF·Na₂MoO₄–SrMoO₄–Na₂MoO₄ is confirmed by the thermodynamic method. The separation was experimentally confirmed by X-ray phase analysis of a mixture of 50 equi % Na₂MoO₄ and 50 equi % SrF₂, corresponding to the point of complete conversion. A tree of phases was constructed and the main chemical reactions for mixtures corresponding to equivalence points were described. Using differential thermal analysis and thermogravimetry, a series of polythermal sections was studied, from which the directions to three points of invariant equilibria were determined. The coordinates of the eutectic and two peritectics have been revealed. All points of invariant equilibria are located in the phase triangle 2NaF·Na₂MoO₄–SrMoO₄–Na₂MoO₄. The phase complex of the system is represented by five crystallization fields — sodium and strontium fluorides, strontium molybdate, incongruent melting compounds and boundary solid solutions based on sodium molybdate. The minimum crystallization fields correspond to the compound 2NaF·Na₂MoO₄ and the boundary solid solution based on sodium molybdate.

An atomic layer deposition (ALD) of aluminum-molybdenum oxide (Al,Mo,O) films, based on cyclic reactions of trimethylaluminum (TMA) and molybdenum dichloride dioxide (MoO₂Cl₂) vapors, is presented. The effect of adding a water vapor dose into the ALD cycle (TMA-H₂O-MoO₂Cl₂) was investigated. The film growth process was studied in situ using a quartz crystal microbalance (QCM). It was established that at a deposition temperature of 180°C, both the TMA-MoO₂Cl₂ and TMA-H₂O-MoO₂Cl₂ processes exhibit linear growth with growth per cycle (GPC) values of 3.79 Å/cycle and 3.94 Å/cycle, respectively. According to X-ray reflectivity (XRR) and X-ray diffraction (XRD) data, the resulting films had an amorphous structure with a density of ∼3.7 g/cm³ and a root mean square (RMS) roughness in the range of 10-12 Å. Both types of films had a similar composition. The films contained Mo⁶⁺, Mo⁵⁺, and Mo⁴⁺ species.

Layered double hydroxides (LDH) have proven themselves as highly effective sorbents of heavy metals and radionuclides. In particular, modification of LDH with ferrocyanide ions is proposed for extraction of cesium-137. However, sorption-selective characteristics of modified LDH under conditions of extraction of cesium radionuclides from model and real solutions of liquid radioactive waste (LRW) remain unexplored to date. In this work, Zn-Al-LDH was obtained by direct coprecipitation with subsequent in situ intercalation of ferrocyanide anions into the interlayer space to achieve selectivity to cesium. In this work, adsorption kinetics was studied with obtaining the corresponding isotherms, the theoretical maximum sorption capacity is 201 mg/g, the experimentally obtained value is 197 mg/g. The effect of interfering ions on the adsorption of ¹³⁷Cs was also studied and the distribution coefficients K_d(¹³⁷Cs) were determined: 4838 and 1763 ml/g under conditions of model solutions of low and moderate salinity, respectively, and 3259 ml/g in seawater. The resulting composite material demonstrates high potential for the selective extraction of cesium radionuclides from aqueous solutions of varying mineralization.