Vol 42, No 2 (2023)

The synthesis of new energy-intensive compounds, 7-allyl-7H-trifurazano[3,4-b:3',4'-f:3",4"-d]azepine (AzAll) and 7-allyl-7H-difurazano[3,4-b:3',4'-f]furoxano[3",4"-d]azepine (Az(O)All) is described for the first time. The main parameters of the crystal lattice are determined by X-ray diffraction analysis and experimental data on the heats of combustion and enthalpies of formation of these two compounds are obtained. A thermodynamic analysis of the effectiveness of these compounds as components of solid composite propellants and gas-generating fuels is carried out. It is shown that the compounds under consideration have no prospects for use in solid composite propellants, but they are very effective as potential dispersants of solid fuels for gas generator engines.

In this review, a brief digression into the current state of the theory of luminescence is made and, using the example of my own works, carried out jointly with my colleagues since the 1970s up to the present time, it is shown how effective the application of luminescence analysis is in studying the mechanisms of photochemical transformations.

It is established that firing samples (granules) in a layer of fluxed magnetite iron ore concentrates are accompanied by complex physicochemical processes related to the oxidation of magnetite and the decomposition of carbonates. When they are heated, along with heat exchange processes, mass transfer processes also occur. These processes are interrelated and affect each other, as well as the degree of completion of the processes of oxidation and decarbonization in the layer. The oxidation mechanism of the samples containing magnetite is considered. A model of the mass transfer process for the period of decomposition of carbonates is refined. An equation is proposed that describes the kinetics of magnetite oxidation in samples upon heating for a more general form of boundary conditions. An equation is presented that makes it possible to determine the rate constant of the oxidation process depending on the characteristics of the heat-carrier gas and the properties of the material. A calculation procedure is developed to determine the diffusion coefficient of oxygen in the combustion products of various fuels. Experiments are carried out to study the kinetics of oxidation and decarbonization processes in a layer of granules on an experimental setup, which make it possible to simulate these processes in relation to different periods of their heat treatment in thermal plants and determine the mass transfer coefficients. This will make it possible to determine the degree of completion of processes by the height of the layer at the given values of the temperature and duration of firing.

Using the results of previous experimental research, a mathematical model of ignition is developed for a typical gel fuel combustible particle, based on an organic polymer thickener, in a high-temperature air medium. The mathematical model of the studied process is developed using the mathematical tools of continuum mechanics and chemical kinetics. It describes a process corresponding to the limiting regime in which the characteristic heating times of the fuel and the resulting gas-vapor mixture are much longer than the characteristic times of the chemical reaction of the fuel and oxidizer in a gaseous medium. Satisfactory results of the verification of the mathematical model and numerical algorithm make it possible to conclude that this approach can be used to reliably predict the ignition characteristics of such types of gel fuels. The ignition delay times range from 0.3 to 10.0 s for single particles of gel fuel 0.25–2.00 mm in size, heated in air at temperatures of 750 to 1473 K.

The structures of two-layer silicene and the 4H-modified silicon carbide (SiC) film supporting it, which act as the anode of a lithium-ion battery, are studied by the molecular dynamics method. The behavior of such a combined anode is considered under conditions of its vertical filling with lithium. The silicene sheets contain vacancy defects in the form of bi-, tri-, and hexavacancies. Lithium ions directed perpendicularly to the silicene plane deposited on the silicene sheets remain in the silicene channel and partially penetrate the substrate surface. The vertical displacements of atoms in the top sheet of silicene after lithium intercalation significantly exceed the corresponding displacements in the bottom sheet in contact with the substrate. The construction of Voronoi polyhedra (VP) separately for the Si- and C-subsystems of SiC make it possible to reveal the structural features of each of the subsystems of the studied two-dimensional layered structure.

This paper presents the results of DTA/TG studies of one of the most popular systems in solution combustion synthesis (SCS) nickel nitrate hexahydrate (Ni(NO3)2⋅6H2O)–hexamethylenetetramine (C6H12N4). X‑ray diffraction and EDS-assisted SEM are used for characterizing the reaction products. The specified system is studied in the form of a powder mixture, a gel obtained by dissolving the initial reagents in distilled water, and the same gel, heat treated at 100°C. It is established that the formation of metallic nickel is possible only if the mixture of reagents is first transferred to the gel state. The values of the effective activation energies of the formation of NiO and metallic nickel are calculated, and the features of the course of interactions depending on the method of preparation of the studied samples are presented.

In this paper, we study the formation and dynamics of cavitation bubbles arising in different zones of preovulatory (GV) mouse oocytes as a result of optical breakdown under the action of femtosecond laser pulses with a wavelength of 790 nm. The dynamics of the growth and collapse of the cavitation bubble is determined from the time dependence of the scattered light intensity on the bubble. The difference in the thresholds of optical breakdown and the dynamics of the cavitation bubble between different regions of the oocyte and the aqueous buffer solution is numerically characterized.

The effect of microwave radiation treatment on the widely used technical acrylonitrile-butadiene-styrene (ABS) polymer widely used for 3D-printing is studied. The chemical structure and tensile strength characteristics of filled (with 3 wt % carbon fiber) and unfilled ABS plastic irradiated with microwave radiation for 300, 600, 900, and 1200 s are evaluated. It is shown that the effective irradiation time for the mechanical improvement of the filled samples is 300 s, while no significant changes in the mechanical characteristics of the initial ABS samples are found.

Using the Landauer–Buttiker formalism and the nonorthogonal tight-binding Hamiltonian with NTBM parametrization, the electron transmission and conductivity of metal armchair-type nanotubes of subnanometer diameter are studied. We consider the effect of various structural defects (Stone–Wales defect, monovacancy, replacing a nitrogen atom) and radicals adsorbed on the nanotube surface (H, O, OH, COOH) on the electronic characteristics of carbon nanotubes (CNTs). It is found that structural defects and adsorbates have different effects on their conductivity. In this case, two competing processes are observed. On the one hand, this is a weakening of the conductive properties of CNTs due to the increase in the number of scattering centers, and, on the other hand, the increase in conductivity due to structural relaxation processes.