Vol 44, No 2 (2025)

The thermodynamic and kinetic aspects of corrosion of low carbon steels in a flow of H₂SO₄ solution containing Fe(III) sulfate, which occurs through parallel interaction of the metal with acid and Fe(III) salt, are considered. Potentiometric studies of a H₂SO₄ solution containing Fe(III) and Fe(II) salts showed that Fe(III) cations in these media are bound into complexes with sulfate anions, which reduces their oxidizing properties. Voltammetric studies of the behavior of steel in a flow of H₂SO₄ solution containing Fe(III) sulfate indicate that its corrosion includes the reaction of anodic ionization of iron, occurring in the kinetic region, and two cathodic partial reactions – the release of hydrogen and the reduction of Fe(III) cations to Fe(II), characterized by kinetic and diffusion control, respectively. The partial reaction of Fe(III) cations reduction, which occurs under diffusion control, determines the sensitivity of the entire corrosion process to the hydrodynamic parameters of the aggressive environment and the concentration of Fe(III) salt in it. A linear dependence of the steel corrosion rate on the square root of the rotation speed of the propeller mixer used to mix the aggressive environment is observed. Weak inhibition of steel destruction by a corrosion inhibitor in H₂SO₄ solutions containing Fe(III) salt is the result of the accelerating effect of Fe(III) cations on three partial electrode reactions of iron.

Taking into account the data on water binding to stable acetic acid hydrates, an interpretation of the dependence of the rate of the cyclohexene methoxycarbonylation reaction catalyzed by the system Pd(OAc)₂ – PPh₃ – p-toluenesulfonic acid monohydrate, depending on the last component concentration is proposed. This reaction mechanism scheme is supplemented by the reaction of formation of stable acetic acid hydrates AcOH×(H₂O)n, where n =1–10. The effective rate constant of cyclohexene methoxycarbonylation has been estimated. It is con-cluded that the stable acetic acid hydrates formation in the presence of small water amounts in toluene medium is possible.

Recently, works have appeared devoted to the production and study of high-entropy ceramics (HEC), in particular, high-entropy carbides and high-entropy borides. It is assumed that the properties of HEC, due to the distortion of the crystal structure, will exceed the properties of one or two-component borides and carbides. Previously, HEC containing high-entropy carbide and high-entropy boride were obtained by mechanical alloying in a ball mill and electric spark plasma sintering. The strength of this two-phase HEC exceeded the average strength of the high-entropy carbide and high-entropy boride included in its composition. The effect of the ratio of components and compression of samples on the combustion velocity, elongation of samples, morphology and phase composition of synthesis products in the system х(Ti+Hf+Zr+Nb+Ta+5С) + (1 – х)(Ti+Hf+Zr+Nb+Ta+10В) is investigated. With an increase in the content of boron in the composition of mixtures, the combustion velocity of the samples increased. A significant influence of impurity gas release on the combustion process of samples was discovered. Combustion velocity of compressed samples has increased significantly. The elongation of the samples increased with an increase in the carbon content of the mixture. Due to the significant elongation, the synthesis products had high porosity, and powders were easily obtained from them. By the XRD method, reflexes of the high entropy diboride [Ti, Hf, Zr, Nb, Ta]B₂ were recorded in the composition of the combustion products of the mixture Ti+Hf+Zr+Nb+Ta+10B. Three multi-element carbides have been identified in the composition of the synthesis products of the Ti+Hf+Zr+Nb+Ta+5C mixture: medium-entropy [Ti, Hf, Ta]C and two high-entropy [Ti, Hf, Zr, Ta]C and [Ti, Hf, Zr, Nb,Ta]C. The combustion products of a mixture of 50%(Ti+Hf+ +Zr+Nb+Ta+5C)+50%(Ti+Hf+Zr+Nb+Ta+10B) contain five multi-element high-entropy phases: two diborides and three carbides based on metal solid solutions.

In this work, high-entropy ceramics containing high-entropy carbides and borides were obtained for the first time using the SHS method. The SHS method allows synthesis to be carried out in one stage, varying the composition of the products. The results of the work can be used to obtain high-entropy ceramics in the system х(Ti+Hf+Zr+Nb+Ta+5С)+(1-х)(Ti+Hf+Zr+Nb+Ta +10В).

The energy capabilities of five pentazole salts as fillers for composite solid propellants (СSP) were studied. Of these, only hydroxylammonium pentazolate (IV) turned out to be a relatively good component for creating model СSPs. Compound IV is superior to HMX in terms of I_ef(3) both in a binary composition with an active binder and in similar compositions with the addition of AP, ADN or Al. Lithium, ammonium, hydrazinium and 1,4,5-triaminotetrazolium pentazolates are inferior to HMX as the main filler for CSP.

The possibility of a cool-flame oxidation of propane-oxygen mixtures of the composition C₃H₈:O₂ = from 1:3 to 1:1, which is accompanied by the phenomenon of a region of negative temperature reaction rate coefficient (NTC), has been experimentally demonstrated. An increase in the C₃H₈:O₂ ratio (enrichment of the mixture with propane) leads to an expansion of the temperature range for the existence of the cool-flame oxidation regime and shifts the NTC region towards higher temperatures. Cool-flame oxidation of propane is accompanied by the formation of a number of popular petrochemical products (olefins, oxygenates, propylene oxide), the relative yield of which can be controlled by changing the composition of the mixture and the oxidation temperature.

The interaction of hemin and the Zn(II)-complex of tetra(4-pyridyl)porphyrin (ZnTPP) with hexamolybdenonickelate anions in an aqueous medium has been studied by electron absorption spectroscopy and spectrofluorimetry. Differences in spectral behavior of two metal porphyrins when interacting with heteropoly compounds are associated with differences in the structure of these porphyrins. Both the transformation of the porphyrins characteristic bands is manifested, and new bands are found in the electron absorption spectra that indicates the formation of hybrid organo-inorganic complexes. In addition, fluorescence quenching of ZnTPP, predominantly of the static type, is observed, which also testifies the formation of hybrid complexes. The binding ability of the ZnTPP system - crystalline hydrate of sodium hexamolibdenonicelate (HMN) was evaluated, as well as the stability of the obtained hybrid complex. The results of the study will be useful when creating hybrid complexes by molecular design in order to further incorporate them into various biomedical applications.

The results of the formation of foamed acrylamide sorption composites (SC) from suspensions of various natures under microwave heating conditions are presented. The increase in sorption properties (SP) was carried out due to the additional introduction of inorganic (manganese oxide) and organic (chitosan) sorbents into the acrylamide foam matrix. The production of acrylamide foam composites based on dispersion media with chemical reagents that react with toxic compounds and form sediments in the polymer matrix increases the sorption capacity (SC).