Vol 97, No 3 (2023)

The review summarizes and analyzes the current state of research in the field of corrosion of metals in acid solutions and their inhibitory protection. The most important concepts about the metal corrosion mechanism in acidic media were considered. The existing experimental approaches to the study of metal corrosion in acid solutions and the effect of organic corrosion inhibitors on this process were discussed. It was shown that electrochemical and physicochemical methods play an important role in studies of the state of the metal surface. The mechanisms of metal corrosion inhibition in acid media were analyzed. The thermodynamic and kinetic aspects of adsorption of inhibitors on metals were considered. The maximum efficiency in metal protection is shown by organic compounds whose molecules are capable of chemisorption interaction with the metal surface, forming polymolecular protective layers of molecules chemically bonded with one another.

A numerical analysis is performed of a thermodynamic determination of the surface tension (ST) of a vapor–liquid binary mixture and interfacial tension (IT) between two liquid phases as the excess value of free energy ΔF of a two-phase system with and without for a phase boundary. Calculations are made in the simplest version of the lattice gas model (LGM), allowing for the interaction of nearest neighbors in a quasi-chemical approximation. Each node of a two-component mixture in the LGM system can be occupied by mixture components A + B and vacancy V. The two main ways of calculating ST, expressed in terms of different partial contributions Miq to excess free energy ΔF (where i = A, B, V are vacancies; 1 ≤ q ≤ κ, q is the number of the monolayer inside the boundary; and κ is its width), are compared, as are calculations of ST and IT as excess free energy ΔF for a lattice model with no vacancies. The ambiguity of ST and IT values depending on the type of Miq functions is obtained by calculating the temperature dependence for a flat boundary and the dependence of ST and IT on droplet size at a fixed temperature. The role of vacancies in the LGM as the main mechanical characteristic of the system under the condition of strict phase equilibrium in three equilibria (mechanical, energy, and chemical) is discussed.

Processes of the formation of coordination compounds in the Fe(II)–Fe(III)–H2Sal–C2H5OH–H2O system are studied using the Clark–Nikolsky oxidation potential at a temperature of 298.16 K and an ionic strength of the solution of 1.0 mol/L against a sulfate background. The formation of complexes of the following compositions is established: [FeHSal(H2O)5]2+, [Fe(HSal)2(H2O)4]+, [Fe(HSal)2OH(H2O)3]−, [Fe(HSal)2(OH)2(H2O)3]3−, [FeIIIFeII(HSal)2(OH)2(H2O)8]+, [FeHSal(H2O)5]+, [Fe(HSal)(OH)(H2O)4]0, [FeIIFeIII(HSal)2(OH)2(H2O)8]+. The constants of formation of all complexes are calculated via iteration of the oxidizing function, and the areas of their dominance and maximum degrees of accumulation are determined.

A study is performed of cobalt/MgAl2O4 catalysts promoted with glucose at Co/C molar ratios of 16.5, 3.2, and 1.6 via sequential deposition and codeposition. Magnetometry and IR spectroscopy of adsorbed CO show that raising the content of carbon in the catalyst contributes to the reduction of cobalt, regardless of how Co is introduced. Infrared spectroscopy reveals the main adsorption sites are cobalt cations and metallic Co. A strong contribution from adsorption sites characteristic of large Co particles is observed in systems synthesized via codeposition. Adsorption sites attributed to Co2+ and Coδ+ are structurally more homogeneous than ones attributed to metallic Co.

The solubilizing effect of β-cyclodextrin on fingolimod, a new generation immunosuppressant, is studied for the first time. A possible 20× increase in the solubility of fingolimod due to the penetration of the hydrophobic fragment of the drug molecule into the macrocyclic cavity of the cyclodextrin is shown. Data driven 1H NMR spectroscopy and computer modeling suggest the configuration of the resulting inclusion complexes. The constant of the complex’s stability and its energy of complexation are calculated, and the formation of hydrogen bonds between fingolimod and β-cyclodextrin is considered.

The heats of interaction between alanyl-phenylalanine and solutions of nitric acid and potassium hydroxide at 288.15 and 308.15 K and solution ionic strengths of 0.5, 0.75, and 1.0 are determined via calorimetry with KNO3. Standard thermodynamic characteristics (ΔrH°, ΔrG°, ΔrS°, ΔC∘pΔ∘) of the reactions of acid–base interaction in aqueous solutions of alanyl-phenylalanine. The effect temperature has on the heats of dissociation of alanyl-phenylalanine is considered along with the relationship between the thermodynamic characteristics of the dissociation of the dipeptide and the structure of this compound.

Networks of hydrogen bonds in mixtures of ethylene glycol (EG) and ethylenediamine (ED) are studied and described via molecular dynamics, graph theory, and Delaunay simplices. Results are compared to data on EG–H2O and ED–H2O systems.

Potentials of the embedded atom model (EAM) for solid and liquid magnesium are proposed. Properties of magnesium are studied by means of molecular dynamics (MD) at binodals of up to 1500 K, and under conditions of static and shock compression. The main characteristics of bcc and liquid magnesium (structure, density, energy, compressibility, speed of sound, and coefficients of self-diffusion) are calculated. The static compression isotherm at 298 K up to a pressure of 108 GPa and the Hugoniot adiabat up to a pressure of 80 GPa are calculated with allowance for electron contributions. Values of the excess energy of the surfaces of magnesium nanoclusters with 13 to 2869 particles are found, and the Gibbs–Helmholtz equation for the relationship between surface tension and surface energy is estimated.

The kinetic theory of diffusion over vacancies is used to obtain expressions for the fluxes of atoms in a three-component alloy. This hole gas approach allows us to express kinetic coefficients in terms of the coefficients of diffusion of labeled atoms from microscopic considerations. The conditions for the formation of nonequilibrium impurity shells are revealed by studying the kinetics of decomposition using these expressions. These shells can considerably inhibit the growth of precipitates and change the properties of the alloy.

The article presents the results of our study of the mechanisms of the photoreactions of methyladamantylthione AdCSCH3 (I) using chemical nuclear polarization (CNP) effects, which show themselves in the NMR spectra. While pulsed and laser photolysis allows us to study the kinetics of death and accumulation of intermediates released from the solvent cell, the use of CNP allows us to study cell processes in detail. The elementary acts of the reaction were established and proved experimentally.

An original comparative study is performed of the combustion of granular and powder Ti–C and (Ti–C)+20%Ni mixtures with granules of different sizes, while varying titanium particle sizes in a range of 31–142 mm. It is found that the rate of combustion of the (Ti–C)+20%Ni powder mixture is 2–3 times higher than that of a Ti–C mixture, despite the lower temperature of combustion of the former. The results are interpreted in terms of the convective–conductive combustion model and attributed to the inhibitory effect of impurity gases that evolve while heating the component particles ahead of the combustion front. The rate of combustion of the granules’ material is calculated using those of granular mixtures with granule sizes of 0.6–1.7 mm. This rate can be thought of as the rate of combustion of a powder mixture in which the effect of impurity gases is neutralized. It is proposed that the ratio of the rates of combustion of the material inside the granules and the powder mixtures be used as a quantitative measure of the effect impurity gas evolution has on the combustion of powder mixtures.

A relatively simple way of obtaining polymer vesicles via self-assembly in an aqueous acetone medium is proposed on the basis of biologically active polymer sulfite lignin (lignosulfonate). The size and morphology of polymersomes are controlled according to molecular weight (46.300–60.000 Da), the concentration of lignosulfonate (CLS 0.10–1.28 g/dm3), and the content of acetone (φAc 0.6–4.0 vol %) in the suspension. The resulting polymersomes are characterized by sizes of 200–350 nm, a polydispersity index of 0.25–0.18, and a ζ potential of −26.3 to −51.0 ± 2.2 mV. Air-dried powders of polymersomes isolated from the corresponding suspensions are polydisperse, with sizes ranging from 40 to 300 nm. The morphology of polymersomes is confirmed by electron microscopy data (SEM, TEM, and AFM). In light of the biological activity of lignosulfonate, polymersomes derived from it can potentially be used in such biomedical applications as targeted drug and gene delivery, enzymatic catalysis, and optical imaging in vivo.