Vol 97, No 10 (2023)

A summary is presented of results from studying the transport characteristics of hydrogen isotopes in a number of fusion reactor materials as ferritic–martensitic steels, austenitic steels, and CuCrZr–bronze. The parameters of tritium transport in the materials are obtained using experimentally measured parameters of hydrogen and deuterium transport within the classical rate theory. The applicability of this approach is discussed. It is shown that a considerable part of the experimental data is inconsistent with assumptions based on the classical theory. Other approaches are required to accurately predict tritium fluxes through fusion reactor materials.

In mathematical chemistry problems, a chemical reaction is represented as a transformation of one molecular ensemble into another, and information entropy and related parameters are often used to quantify changes in the complexity of molecules. The information entropy of a chemical reaction is calculated as the difference between the values corresponding to an ensemble of products and an ensemble of reagents. Previously, we have shown that the information entropy of molecular ensembles depends not only on the information entropy of individual molecules, but also on cooperative entropy—an emergent parameter that arises when molecules are combined into an ensemble. Inclusion of this parameter in calculation determines the peculiarities of calculating the information entropy for interrelated chemical reactions. The article considers systems of independent and parallel chemical reactions and gives an analytical dependence that correlates the information entropy of the total process with the parameters of individual reactions.

A mathematical analysis of the process for the preparation of high-density jet fuels of T-6 and T‑8V grades, based on hydrogenation of polycyclic aromatic (mostly bicyclic) hydrocarbons, has been performed. The process was carried out on a pilot laboratory plant using two nickel catalysts: Raney nickel and nickel on kieselguhr. The experimental data obtained for temperatures of 200–400°C and different feed space velocities were used to construct a mathematical model for catalytic hydrogenation of hydrocarbons that allows for changes in the volume of the reaction mixture. The concentrations of mono- and bicyclic aromatic hydrocarbons (initial and intermediate compounds) and naphthenes (target products) obtained within the framework of the mathematical model are in good agreement with the measured concentrations. The solution of the inverse kinetic problem made it possible to estimate the kinetic parameters of the main chemical transformations in the hydrogenation of aromatic hydrocarbons.

New nickel-containing catalysts based on the phyllosilicate phase have been obtained by microwave activation for efficient liquid-phase hydrogenation of a number of unsaturated compounds to olefins under relatively mild reaction conditions: T = 100–140°C, pH2 = 1.5 MPa, reaction time 1 h. A comparison of the synthesis methods showed that the best results with 90.1% selectivity of styrene formation at 89.6% conversion of phenylacetylene were obtained on the nickel catalyst prepared by microwave synthesis.

The possibility of preparation of a polymetallic dispersed Fe–Ni–Co–Al system in aqueous solutions by a redox process between iron(III), nickel(II), cobalt(II) ions and aluminum microparticles in aqueous solutions is shown. In this case, a structure is formed in the aqueous solution, which, from the standpoint of the phase composition, is a mechanical mixture of elemental metals. It has been found that the synthesized Fe–Ni–Co–Al system consists of metallic aluminum particles coated with elemental metals (iron, nickel, and cobalt) with a minimum content of the oxide phase. Additional HF modification of the studied sample of the polymetallic system in low pressure inductive discharge plasma leads to the formation of a number of intermetallic compounds, mainly CoFe (~60%) and FeNi (~15%), and also ensures particle spheroidization. The resulting intermetallic powder composition is potentially suitable for use in additive manufacturing technologies.

An experimental study of the equilibrium distribution of cations in the system of Dowex 50 sulfonic cation exchanger and an aqueous solution of picolinic acid and iron chloride was carried out. A high concentration of iron and picolinic acid complexes was obtained in the Dowex 50 sulfonic cationite phase. The possibility of calculating the equilibrium counterionic composition of Dowex 50 sulfonic cationite from the equilibrium constants of binary ion exchanges and the known composition of the solution is shown. Sulfocationite Dowex 50 is proposed as a container for biologically active preparations based on picolinic acid and Fe3+ cations.

Graphdiynes (GDYs) are two-dimensional carbon nanostructures containing sp- and sp2-hybridized carbon atoms that form conjugated bonds in the linear chains connecting six-membered carbon rings. The results of scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy showed that GDYs have a uniform surface and contain conjugated –С≡С–С≡С bonds. The hydrogen-adsorption capacity of GDYs was studied, and a comparative analysis of hydrogen adsorption in GDYs, graphenes, graphene nanotubes, and graphene structures formed on zeolites was performed. The substrate on which the carbon nanostructure is formed was shown to have a significant effect on the adsorption capacity of the latter. The possibility and prospects for the synthesis of graphenes on catalysts to increase their efficiency in hydrogenation processes are considered.

Transformations in the S–AgNO3–NH4X–NH4NO3 (X = Cl, Br, I) system show that nanoparticles and nanocomposites with a controlled size of particles and content of components can be synthesized via mechanical treatment and adding small amounts of a liquid in which the precursors are soluble. Nanoparticles form in a dimethyl sulfoxide (DMSO) medium through conventional (continuous dissolution–crystallization) or reactive means (continuous dissolution of precursors and their reacting with subsequent crystallization of the target product), rather than by direct mechanical activation. The first version is used for synthesizing sulfur nanoparticles (nanosulfur); the second, for synthesizing silver halides. Sulfur-containing S/AgX nanocomposites with a controlled content of sulfur are synthesized mechanochemically. A predetermined content of nanosulfur in the nanocomposites is obtained via the dissolution–crystallization (recrystallization) of sulfur in DMSO inside a mechanochemical reactor. The proposed technical solution allows the synthesis of S/AgX nanocomposites through processing AgNO3, NH4X, and NH4NO3 (diluent) precursors, commercial sulfur, and small amounts of DMSO in planetary ball mills with different fittings. The water-soluble components of the product of mechanosynthesis are readily washed off.

The oxidation stability and phase formation sequence for pure aluminum APK and Al–2.3%V alloy heated in air at rates of up to 100°C/min were analyzed by thermogravimetry with differential scanning calorimetry and X-ray diffraction using synchrotron radiation. It was established that an increase in the heating rate from 10 to 100°C/min does not significantly change the thermal stability of the modified Al powder. The presence of Al3V and Al10V intermetallic compounds, as well as a small amount of γ-Al2O3, in the structure of the alloy should favor consolidation of metal particles and reduce the porosity of the resulting product during selective laser melting (SLM).

Within the scalar-relativistic and full relativistic approximation, ab initio calculations of the electronic structure for all singlet and triplet states of the KRb molecule converging to the first two excited dissociation thresholds were performed. The adiabatic interatomic potentials and spin-orbit electronic matrix elements derived within of the framework of “a” and “c” Hund’s coupling case as a function of the inter-nuclear distance have allowed the asymmetry puzzle of the fine structure Ω = 0+/–, 1, 2-splitting experimentally observed for vibrational levels of the triplet d3ΠΩ state of KRb.

Electronic absorption spectra were calculated in the visible region for clusters of the pigment Yellow 3 that comprise one, two, and four molecules. The geometry was optimized by the PBEh-3c and B3LYP-D4/def2-SVPD methods. The results obtained by the B3LYP-D4/def2-SVPD method correlate best with the experimental data. The spectral characteristics were calculated by the TD-DFT and sTD-DFT methods with the PBE0 functional and the def2-SVPD basis set. By analyzing the natural transition orbitals (NTOs) and changing the electron density during the formation of excited states of the studied clusters, it was shown that the main contribution to the spectral lines in the visible range is made by the density transfer from the aromatic rings to the nitro group and the conjugated bond system in the center of the molecule. In this case, for the crystalline state of matter, all excited states are delocalized, and the main contribution to the intermolecular transfer of the electron density is made by the formation of excitons.

The reasons for the failure of the first attempts at countercurrent electrophoretic separation of isotopic lithium ions are analyzed. It is concluded that the separation of these ions in the potentiostatic version of the countercurrent process scheme used by the authors is futile. As an alternative for the preparative separation of isotopic and other ions with similar chemical properties, a galvanostatic mode of countercurrent electrophoretic separation is proposed. Using examples of the separation of alkali metal ions and isotopic lithium and rubidium ions, it is shown that in this case the system enters a stationary self-regulating regime and significantly higher separation factors are achieved compared to the potentiostatic version of the process. It has been determined that a high separation efficiency is achieved with a minimum length of the separation space. For significant effects of the separation of isotopic lithium ions, a separating column 4 mm in height filled with quartz sand is sufficient. Additionally, to address the analytical challenges of electrophoretic separation of isotopic ions of light elements, such as lithium and boron, the required efficiency is also achieved under the potentiostatic conditions of the traditional scheme of capillary zone electrophoresis, as demonstrated in the examples of determining the isotopic composition of the aforementioned elements.

The electrochemical properties of N-substituted salts of 2,2'-bipyridine: N-methyl-2,2'-bipyridinium iodide and N,N '-dimethyl-2,2'-bipyridinium iodide were studied by cyclic voltammetry (CV). The electrochemical properties are greatly affected by the methyl substituents at the nitrogen atom in the ortho-bipyridine molecule. The conproportionation constants were calculated for N,N '-dimethyl-2,2'-bipyridinium iodide and made it possible to judge about the degree of electron localization in the systems.

The thermodynamic stability of the axial (а) and equatorial (е) forms of the S- and R-enantiomers of 5,5,6-trihydroxy-6-methyldihydropyrimidine-2,4(1Н,3Н)-dione was studied by quantum-chemical methods. The equilibrium geometrical parameters and thermodynamic characteristics were determined by the DFT method using the TPSS functional combined with the 6-311+G(d,p) split-valence basis set including the d and p type polarization functions. The Chemcraft and VMD programs were used to visualize the geometrical structure. The most stable forms of 5,5,6-trihydroxy-6-methyldihydropyrimidine-2,4(1Н,3Н)-dione are Se and Re in both the gas phase and aqueous and organic (DMSO) media. The activation barrier of the rearrangement inside the ring is 21.22–24.93 kJ/mol depending on the medium.

The luminescent properties of p- and m-nitrodibenzoylmethanates of boron difluoride are studied by via quantum-chemical modeling in combination with stationary and time-resolved luminescence spectroscopy. The effect the position of the nitro group has on the luminescent properties of the complexes has been revealed. In the series of donor substituents (phenyl, naphthyl, p-methoxyphenyl), compounds with p‑methoxyphenyl have the highest yield of luminescence quanta. The nitro group in the p-position (in contrast to the m-position) greatly reduces the yield of luminescence quanta. The formation of exciplexes is observed in the solutions of complexes in benzene, increasing the yield of luminescence quanta and creating a strong bathochromic shift of the luminescence spectrum’s maximum.