Issue

The paper gives a predictive estimate of detonation nanodiamond (DND) yield depending on the value of oxygen balance, zone length, and chemical reaction time of explosives. The dependences of the main characteristics of explosives on each other are determined. It is shown that practically any characteristic of explosives (e.g., detonation velocity) can be used to calculate other characteristics of explosives, as well as the DND yield during their synthesis. The DND yield from hydrogen-free benzotrifuroxane (1.88 wt. %) was determined for the first time. According to the data of the Institute of Hydrodynamics named after M.A. Lavrentiev (Russia, Novosibirsk), such nanodiamonds have a spherical shape (diameter ~100 nm) due to a very high temperature (4300 K) and pressure of 36 GPa. Moreover, the thermal effect of combustion and the thermal effect of the explosion can be accurately calculated based on the elemental composition of explosives. From there, the specific power of the explosives and all other characteristics, including the DND yield, can be determined. Predictive evaluation does not exclude the need for experimental work, but determines its feasibility.

Improving physical and mechanical properties of austenitic stainless steels (ASS) by methods of surface severe plastic deformation (SSPD) is one of the key problematic topics in the field of surface engineering and nanocrystal materials. The complex nature of the structural states evolution under the conditions of SSPD restricts the possibilities of a specified nanostructuring of the type 18-10 ASS in a wide range of deformation impacts. The article presents the results of XRD and TEM analysis of AISI 321 near-surface layer after ultrasonic nanocrystal surface modification (UNSM) with different processing densities. The work used methods of X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) tested for examination of the structural and phase composition of the type 18-10 ASS subjected to UNSM. XRD and TEM indicate a two-phase (α′ + γ) composition of the near-surface layer of AISI 321 steel processed by UNSM. The XRD technique has established the functional dependencies of the martensite volume fraction from 1) the processing density and 2) the strain energy density, the approximation of which by linear regression equations is performed with reliability R2 = 0.984. According to TEM data, the structure of the near-surface layer of AISI 321 stainless steel subjected to UNSM with the maximum processing density used (N = 9367 mm–2) is represented by a significant amount of martensite in the form of lamellae with the width of less than 100 nm and a high dislocation density. The results of this work can be used to develop and optimize the UNSM processing modes of the 18-10 ASS produced by subtractive, additive and hybrid additive-subtractive manufacturing technologies.

Multifunctional energetic materials (reactive materials) under normal conditions are inert mixtures, but under strong mechanical or thermal impact they are capable of intensive exothermic reactions. For the development of reactive materials and optimization of their composition it is necessary to take into account the sequences of chemical reactions. The features of combustion in powder reactive material based on tungsten, polytetrafluoroethylene and aluminum have been investigated. Since the metal components react with the decomposition products of polytetrafluoroethylene, this stage was studied in separate experiments on combustion of metals with CF4 tetrafluoromethane. The use of tetrafluoromethane instead of polytetrafluoroethylene made it possible to determine that in the Al–CF4 system the reaction starts at 900–1000 °C, and in the W–Al system at 700 °C. Intensive evaporation of polytetrafluoroethylene in the W–PTFE–Al system prevents the reaction of tungsten with aluminum, which leads to ignition at 900–1000 °C. Combustion of two-component systems W–Al and Al–CF4 showed that the heat released during their interaction is insufficient for selfsustaining synthesis. Combustion of W–Al samples in tetrafluoromethane environment is realized in self-sustained mode. The reaction of tungsten with aluminum gives the initial impulse, and the main heat source is the interaction of aluminum with tetrafluoromethane.

Almost all stents with medicinal coatings used in Russia are manufactured abroad and have a high cost, which cannot meet the needs of Russian patients and their financial capabilities. The search and development of new types of medical stent coatings, as well as the establishment of their production in the Russian Federation is relevant. It is necessary to create thin-film drug coatings of stents with an extended time of drug emission for the treatment of various diseases. As a component providing prolonged and dosed desorption of the drug from the surface of the stent, it is best to use a carrier polymer. The paper investigates the possibility of using a promising modern material – carbon nanotubes – as a component of the medicinal coating of a medical stent, which will provide not only an improvement in the physical and mechanical properties of the coating, but also a prolonged effect of the drug by increasing its desorption time. Theoretical studies on the mechanisms of creating drug coatings for stents based on the polyvinylpyrrolidone copolymer, which include drugs (tegafur, dexamethasone) and carbon nanotubes, have been carried out. The quantum chemical calculation method – the density functional theory DFT, which is applied worldwide for calculating nanosystems, was used for research.

The potential use of straight-chain trialkylamines to modify the oleophilic-hydrophilic properties of the surface of copper phthalocyanine was explored. Molecular modeling methods utilizing density functional theory were employed to investigate the characteristics of the adsorption process of trialkylamines with alkyl chain lengths of n = 1 ÷ 8. The change in Gibbs free energy for the adsorption of the studied surfactants from the aqueous phase onto the surfaces (001), (201) containing the metal atom was calculated. It was determined that adsorption of trialkylamines from the aqueous phase does not occur on the non-polar surfaces (001) and (201) , with ΔG values ranging from 18 to 41 kJ⋅mol–1. For adsorption onto surfaces containing a metal atom, negative Gibbs free energy values are observed for tripentylamine and longer-chain trialkylamines (assuming complete loss of rotational and translational degrees of freedom) or for all except triethylamine (with partial retention of rotational degrees of freedom). However, for trialkylamines such as trihexylamine and longer, steric hindrances will be observed during adsorption onto surfaces with a metal atom. For all the examined trialkylamines, lower Gibbs free energy values for adsorption on surfaces with a metal atom were noted compared to non-polar surfaces, indicating selective adsorption of these surfactants on the surface of copper phthalocyanine. The study results indicate that tripentylamine exhibits the best characteristics for the oleophilization of the surface of copper phthalocyanine.

The study analyzes the physical mechanisms behind the quasi-diffusive separation of cohesionless spherical particles in thin-layer fast gravity flows on a rough chute with substantial structural and kinematic parameter nonuniformity, with their complex size and density discrepancies. Studies have been conducted into alternative conditions of quasi-diffusive interaction of particles in a fast gravitational flow on a rough chute, which are defined by the dominance of the particles' relative velocities in the direction of gravitational shear or their chaotic fluctuations in the interaction. It has been found that the intensity of the quasi-diffusive separation flux is in direct dependence on the particle collision frequency, which, in the general case of gravity flows of granular matter, is determined at the dominant value of the component of the relative shear velocity of particles and depends to a lesser extent on the velocity of their chaotic fluctuations. In non-ordinary conditions of fast gravity flow, which are formed in the flow of nonsmooth elastic particles in its upper part, called the “cloud” of particles, the frequency of particle collisions is determined at the dominant value of the velocity of their fluctuations. It is found that in thin-layer fast gravity flows the effect of quasi-diffusive separation due to structural nonuniformity of the flow can dominate over the segregation effect resulting from local nonuniformity of the medium.

Desorption of gases from cathode materials in electrovacuum devices (EVDs) is one of the key problems in the production process, which has a significant impact on the performance and durability of devices such as magnetrons, X-ray tubes and vacuum amplifiers. For example, cleaning the surfaces of EVD parts during production inevitably entails their reactions with air components after extraction from the processing zone, and the process of degassing heating during pumping often contributes to an additional complication of the structure and chemical composition of the surface layer, since impurities diffusing to the surface can cause the appearance of new substances. Therefore, even when choosing cathode materials or parts of internal fittings, EVDs are guided by the ability of the material to quickly remove gases, maintain strength at high temperatures and have high chemical resistance. The present paper is a detailed analysis of modern methods of desorption acceleration, the mechanisms of this process and their computational basis, including known physical laws and models of adsorption and desorption. Promising approaches to improving the quality of cathodes at different stages of their production, with an emphasis on the use of new materials and technologies, are evaluated. Calculations confirming the effectiveness of the proposed solutions are analyzed, as well as the influence of various factors on minimizing the impact of desorption processes and increasing the durability of cathodes in EVDs.