Том 99, № 2 (2025)

The results of studies of reactivity and phase formation features in the process of oxidation of aluminum-based powders by TG (thermogravimetry), DSC (differential scanning calorimetry), and X-ray diffraction of synchrotron radiation directly in the process of programmed heating are considered. When applied together using synchrotron radiation, thermal and phase analyses are shown to help get an idea of fast oxidation mechanism processes and accelerate the selection of modifiers to optimize the properties of dispersed aluminum-based systems and technological parameters of synthesis of materials with controlled properties.

The isobaric heat capacity of a single-phase sample of ytterbium titanate of pyrochlore structural type synthesized and characterized by XRD, SEM, and EDX methods in the temperature range 2–1869 K is measured for the first time. The existence of magnetic transformation at < 20 K and the absence of structural transformations in the entire region of existence of Yb₂Ti₂O₇ are confirmed. Thermodynamic functions, viz. the entropy and the enthalpy increment and the Gibbs free energy of formation of Yb₂Ti₂O₇ from elements and binary oxides at 298.15 K are calculated. The contribution to the heat capacity of the Schottky anomaly is estimated.

Values of the standard partial molar heat capacity $\overline{C_{p_i}^0}$ and heat capacity change ${\Delta }_{сольв.} C_{p,i}^0$ during solvation of ammonium ion in the mixed solvent MP-water at 298.15 K are found. The value ${\Delta }_{сольв.} C_{p,i}^0$ of the ammonium ion is presented as the sum of four contributions, viz. electrostatic, cavity formation, solvent structural changes, and specific ion-solvent interactions. Based on experimental data and model representations, the values of the contributions are calculated. Dependences of the resulting values on the mixture composition are discussed in connection with the structure of the mixed solvent.

The vapor-liquid equilibrium of methanol-chloroform-tetrahydrofuran mixtures of different composition and methanol-chloroform-tetrahydrofuran-dimethyl sulfoxide mixtures with different content of dimethyl sulfoxide at 101.32 kPa is studied experimentally. Experimental and calculated values of relative volatility of substances in four-component mixtures are compared. The results of extractive rectification of ternary mixtures on the basis of experimental and calculated data obtained by the NRTL model are predicted.

Catalytic properties of Cu-Zn-catalysts on various commercial supports such as Al₂O₃, SiO₂, ZrO₂(La), TiO₂, ZnO, and activated carbon in the reaction of CO₂ hydrogenation with methanol production are studied. The CuZn/Al₂O₃ catalyst is found to show the highest CO₂ conversion; the highest selectivities to methanol equaling 99% and 97.5% are observed in CuZn/ZrO₂(La) and CuZn/SiO₂ catalysts, respectively, and high CH₃OH selectivities of 90–95% are achieved in the temperature range of 175-275°C; and the CuZn/ZrO₂(La) catalyst had the highest methanol productivity of 547 g/(kgcat h). The synthesized catalysts are characterized by methods of low-temperature nitrogen adsorption, X-ray phase analysis, and SEM-EDX.

Within the framework of the stochastic approach, a numerical study of the kinetics of occupancy of the triplet state of an electron donor molecule caused by photoinduced electron transfer from the donor to the paramagnetic acceptor and back is performed. The conditions are determined, and a general strategy for achieving the maximum efficiency of triplet molecule accumulation induced by the electron transfer is stated. Solvents with fast dielectric relaxation are shown to contribute to increasing the efficiency of the process involved.

The specific heat capacities (ср) of ammonium iodide solutions in the mixed solvent N-methylpyrrolidone (MP)-water in the whole range of compositions were measured by calorimetric method at 298.15 K. The influence of the mixed solvent composition on the heat capacity of three-component NH₄I−MP−Н₂О systems was analyzed. Standard values of partial molar heat capacities of NH₄I in the mixed solvent MP-water at 298.15 K are calculated.

Crystallization of aluminophosphate gels prepared using aluminum isopropoxide with di-n-propylamine/Al₂O₃ ratios of 1.0, 1.4, and 1.8 is studied. Changing the template/Al₂O₃ ratio in the reaction gels is shown to make various intermediate phases form during crystallization into the AlPO₄-11 molecular sieve. A method to control its secondary porous structure based on adjusting the template/Al₂O₃ ratio in the reaction gels is proposed.

The process of redox sorption of oxygen dissolved in water on cathodically polarized granular layers of copper-ion-exchange nanocomposites depending on the water flow rate and the value of polarizing current is studied. It is observed that initially the amount of absorbed oxygen exceeds the amount of leaked electricity. With time, the chemical activity of the nanocomposite decreases, and oxygen continues to be sorbed and further recovered mainly due to the current component of the process. Simultaneous increase in the water flow rate and the strength of the limiting current is concluded to have a favorable effect on the rate of oxygen uptake. Maintaining the constancy of the water supply mode and the respective current strength ensures a stationary course of diffusion, chemical, and electrochemical stages. Successive stages of external diffusive oxygen transfer to the surface of nanocomposite grains, intra-diffusive oxygen transfer along the grain pores and chemical oxidation of copper nanoparticles to oxides characteristic of the final sources are found to be compensated by the stages of electroreduction of oxygen from surface adsorbed complexes and regeneration of oxidation products into metallic copper nanoparticles. The nanocomposite is a continuous source of newly reduced metal particles and contributes to the oxygen redox sorption process reaching the stationary mode. Unlike the nonpolarizable granular layer, the oxygen concentration remains at a low constant level under the conditions of the maximum admissible electric current applied.

Fine-dispersed shungite as an effective filler of composite materials is studied. Experimental data on the influence of the filler concentration of the composite material on its electromagnetic radiation absorbing and shielding characteristics in the radio and microwave ranges are obtained. The obtained data can be used for manufacturing effective radio-absorbing materials and electromagnetic shields for protection against undesired effects of electromagnetic radiation, information protection, in radio engineering, as well as in warfare.

Diffuse reflectance infrared Fourier transform spectroscopy of adsorbed carbon monoxide is used along with X-ray absorption spectroscopy to study the effect a second alloying metal (Zn, Cu) has on the electronic state and local structure of rhodium on the surfaces of Rh/HZSM-5 zeolite catalyst. It is established that introducing copper and zinc helps improve the stability of rhodium toward aggregation (the formation of clusters) under conditions of the oxidative carbonylation of methane into acetic acid. Compared to monometallic catalyst Rh/HZSM-5, where single atom rodium sites are partially aggregated into clusters, the proportion of Rh° is halved in the case of Rh–Zn/HZSM-5, and Rh clustering does not occur in the case of Rh‒Cu/HZSM-5. The stabilizing effect of Cu is due to the interaction between copper and rhodium cations on the surface of zeolite.

A mass spectrometric study of ionization processes of short peptides of triglycine, alanylglutamine, and prolylleucine by electrospray ionization (ESI) and surface-activated laser desorption/ionization (SALDI) methods in the presence of copper sulfate crystalline hydrate is performed. It is shown that during ESI ionization, the presence of copper ions in the solution initiates the aggregation of peptide molecules with the formation of large associates of up to 7-8 peptide molecules. The influence of the nature of peptides on the nature of ionization processes is studied. At the same time, competitive cationization of peptide molecules by copper ions with the formation of an M+Cu+ ion occurs during ionization by SALDI method. Peptide fragmentation and copper cationization of decarboxylation products are also typical.

The electrochemical reaction reduction of nitrites (NO₂−RR) in a neutral aqueous electrolyte is studied, which has important applications both for future ammonia synthesis processes and for effective wastewater and agricultural wastewater treatment. The catalytic activity is compared (the results of the Faradaic efficiency and the yield rate of ammonia are obtained) for noble (platinum) and non-noble (cobalt) metals. Metallic polycrystalline platinum and cobalt serve as electrocatalyst. The surface of the catalysts is analyzed using SEM and light microscopy. The method of linear voltammetry is used to preliminarily identify the potential of ammonia synthesis and estimate the synthesis current density. The values of Faradaic efficiency (FE) and the yield rate of ammonia release are obtained for the five selected values of current densities (J). It is found that the cobalt cathode is more efficient (FE ≈ 99%, yield rate (NH₃) = 2.4 mmol h^–1 cm^–2), which exceeds the values for the platinum cathode ((FE = 88.1%, yield rate (NH₃) = 0.4 mmol h^–1 cm^–2). The electrochemically active surface (ECSA) of the electrocatalysts is determined. The explanation of such activity of catalysts is given according to the results of the work that demonstrate that a non-noble metal cathode can be more effective for NO₂−RR.

Experimental study of mineralization of oxalic acid Н₂С₂О₄ and some other oxidation-resistant organic compounds in an aqueous solution under the action of oxygen, ozone, and ultraviolet radiation is performed. It is found that in acidic solutions Н₂С₂О₄ is not oxidized under the action of ozone or UV-irradiation in the presence of oxygen; under simultaneous action of O₃ + UV, oxidation with low rate is observed. The possibility of photocatalysis of mineralization process by ions Mn²⁺, MnO^4–, Fe³⁺, Со²⁺, BrO^3–, or IO^3– is studied. Fe³⁺ ions are the most effective photocatalyst as there is a rather fast oxidation of oxalic acid to CO₂ in their presence and under UV-irradiation both under the action of O₃ and O₂. The conditions of maximum ozone conversion at oxalic acid photomineralization are found. The possibility of oxidative destruction of more oxidation-resistant substrate - acetic acid - at ozonation and UV-irradiation of solutions with Fe(III) and Н₂С₂О₄ additives is shown.

The dependence of flame propagation characteristics on heterogeneous reactions of atoms and radicals at atmospheric pressure is established. It is noted that along with participation in the breakage of reaction chains, adsorbed hydrogen atoms carry out heterogeneous development of chains as they react with O₂ to form HO₂ radicals registered by the laser magnetic resonance method. In the flame, HO₂ radicals with H atoms form OH radicals, and thus heterogeneous development of chains takes place. The flame changes the chemical properties of the surface. It is concluded that the identified mechanism and equations derived from it quantitatively describe the observed patterns.