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The article presents results of the study of possibilities of selective laser melting (SLM), or so-called additive technologies, for production of permanent magnets. This process makes it possible to produce not only product models and prototypes, but also finished functional products using layer-by-layer addition of material and binding of particles and layers to each other. An alloy based on Fe - Cr - Co system has been chosen as the material for evaluation of the compared technologies for permanent magnets production. The application fields of selective laser melting (SLM/SLP) were considered. The powders obtained by different methods are taken for the research. Classical technology of magnetic alloy casting also was analyzed. The studies of magnetic materials and comparisons of the properties of powder magnets with standard data were carried out. On the basis of 25Kh15KA alloy powder sprayed by gas atomization, permanent magnets with a material density of 7.59 - 7.55 g/cm3 can be manufactured at the SLP plant. They meet the requirements recommended by the state standard GOST 24897 - 81, and achieve characteristics of magnets made by classical metallurgical technologies. To study the magnetic and physical properties, four samples were produced with the same geometry in the shape of a cube. During production of each of the test samples, different operating modes of the plant were selected. Samples were made on the basis of the “Kurchatov Institute” NRS enterprise (the “Prometheus” Central Research Institute of Construction Materials) as part of the NIO-35 technological complex. It was established that characteristics of the powders obtained by gas atomization qualitatively exceed characteristics of the powders obtained by other methods, and the produced magnets meet all the requirements for magnets.

Laser optoporation systems are now increasingly used for intracellular delivery. However, data on the response of cells to radiation-induced nondamaging changes in the integrity of the membrane lip...

VOx films deposited using the multistep method have been investigated. These films were deposited by repeating the two-stage method of low-temperature deposition – low-temperature annealing. The structure and characteristics of VOx thin films have been studied. Taking into account the obtained results, theoretical modeling of the structure was performed and the parameters of the metal-insulator transition have been calculated.

The kinetics of reactive ion etching of Si and SiO2 in the plasma of a high-frequency (13.56 MHz) inductive discharge in a CF4 + O2 mixture in the range of input power of 200–600 W (0.02–0.06 W/cm3) is studied. The key plasma-chemical processes that form stationary electrophysical parameters and composition of the gas phase are identified (a), and the flux densities of neutral and charged particles on the treated surface are determined (b) with the combined use of plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling. It is found that the dominant etching mechanism for both materials is an ion-stimulated chemical reaction proceeding in the kinetic mode and limited by the fluorine flux. It is shown that the decrease in the effective probability of interaction in Si/SiO2 + F systems with an increase in the input power and gas pressure may be due to heterogeneous processes with the participation of oxygen atoms.

Layered van~der~Waals materials of the family TaTMTe$_4$ (TM=Ir, Rh, Ru) are showing very interesting electronic properties. Here we report the synthesis, crystal growth and structural characterization of TaIrTe$_4$, TaRhTe$_4$, TaIr$_{1-x}$Rh$_{x}$Te$_4$ ($x = 0.06$; 0.14; 0.78; 0.92) and Ta$_{1+x}$Ru$_{1-x}$Te$_4$ single crystals. For Ta$_{1+x}$Ru$_{1-x}$Te$_4$ off-stoichiometry is shown. X-ray powder diffraction confirms that TaRhTe4 is isostructural to TaIrTe4. We show that all these compounds are metallic with diamagnetic behavior. Ta$_{1.26(2)}$Ru$_{0.75(2)}$Te$_{4.000(8)}$ exhibits an upturn in the resistivity at low temperatures which is strongly field dependent. Below $T \approx 4$K we observed signatures of the superconductivity in the TaIr$_{1-x}$Rh$_{x}$Te$_4$ compounds for $x = 0.92$. Magnetotransport measurements on all samples show weak magnetoresistance (MR) field dependence that is typically quadratic-in-field. However, for TaIr$_{1-x}$Rh$_{x}$Te$_4$ with $x\approx 0.78$, the MR has a linear term dominating in low fields that indicates the presence of Dirac cones in the vicinity of the Fermi energy. For TaRhTe$_4$ series the MR is almost isotropic. We have performed electronic structure calculations for isostructural TaIrTe$_4$ and TaRhTe$_4$ together with the projected total density of states. The main difference is appearance of the Rh-band close to the Fermi level.

In this work, we performed the comparative study of plasma parameters, steady-state gas phase compositions and Si reactive-ion etching kinetics in CF4 + O2 + Ar, CHF3 + O2 + Ar and C4F8 + O2 + Ar gas mixtures with variable O2/Ar component ratios. It was found that the substitution of Ar for O2 (a) did not disturb the well-known correlation between the polymerizing ability and the F/C ratio in the original fluorocarbon molecule; (b) causes similar changes in electrons- and ions-related plasma parameters (electron temperature, plasma density, ion bombardment energy); and (c) always suppresses densities of polymerizing radicals and reduces the polymer film thickness. At the same time, the specific effects of oxygen on F atom kinetics result in sufficient differences in their densities and fluxes. It was shown that the dominant etching mechanism for Si in all three gas systems is the chemical etching pathway provided by F atoms (since the contribution of physical sputtering is below 10%) while measured etching rates do not follow the behavior of F atom flux. The phenomenological analysis of heterogeneous process kinetics allowed one to suggest factors influencing the effective reaction probability. These are either the transport of F atoms through thick polymer film (in the case of high-polymerizing C4F8 + O2 + Ar plasma) or heterogeneous reactions with a participation of oxygen atoms under the condition of thin or non-continuous polymer film (in the case of low-polymerizing CF4 + O2 + Ar plasma).

This paper reports a process for the growth of zinc–erbium codoped lithium niobate single crystals using a growth charge synthesized from a Nb2O5:Zn:Er precursor and Li2CO3. Characterization of the LiNbO3:Zn:Er crystals by high-speed evaluation of the number of scattering centers, piezoacoustic measurements, photoinduced light scattering, and laser conoscopy has demonstrated that they have high optical quality. The proposed technological approaches are aimed at designing functional materials with fundamentally new characteristics for electronics, acoustoelectronics, and integrated, quantum, and laser optics.

The principal possibility of designing a liquid light filter using hydrophilic solutions is considered. Search for hydrophilic solutions with the most uniform light transmission at all wavelengths of the visible spectrum.

The main problems associated with the operation of reverse osmosis facilities in the treatment of groundwater for drinking water are considered and the possibilities of reducing the concentrate consumption are studied. The existing solutions for reducing the consumption of concentrate using reagent and evaporation techniques are described. The presented article is devoted to the investigation of possibilities to remove calcium carbonate from concentrate due to calcium deposition on “seed” crystals. A new technique for reducing concentrate flow is presented that consists of the operation of a membrane unit in circulation mode whereby concentrate is circulated through a “seed” reactor. Calcium and carbonate ions deposit on the seed crystals thus reducing the scaling hazard and total dissolved solid (TDS) value. A water treatment flow diagram is presented and technical parameters of membrane facilities are determined at each stage that allow one to calculate the entire technological scheme. The product flow on each membrane stage is calculated, scaling rates and calcium carbonate deposition rates are evaluated; caustic consumption and number of membrane facilities at each stage are determined. An experimental technique to determine the amount of hardness removed from the concentrate and the minimal volume of concentrate that could be reached per day is described. The main dependences are obtained and presented, which make it possible to determine the costs of electricity and reagents, types of membranes and volumes of concentrate, the rates of accumulation of sediment on the membranes, and the efficiency of removing hardness ions from water during the operation of the third-stage setup in the circulation mode.

Lithium cobaltate with stoichiometric composition (LiCoO2) is synthesized by the sol–gel method. The physical parameters (particle size, specific surface area, and specific static conductivity) of studied samples are found and their dependence on the calcination temperature is revealed. The following three conduction mechanisms are shown to contribute to the conductivity value: frequency-independent σ0, ionic transport in the sample bulk σsv, and ionic transport at the electrode/ionic conductor interface σdl. The optimal modes of thermal treatment that allow the highly developed specific surface of LiCoO2 to be retained are determined.

The authors propose a novel model accounting for the hardness of materials in a simplified algorithm in order to evaluate their wear resistance by the “block-on-ring” method during tests on a friction machine. This work is relevant for the study of the factors influencing wear and continues to improve this method based on the Taylor series and the testing results for a number of materials in a wide range of hardness. The problem is solved by correlation analysis of the dependence of the hardness of materials on the Mohs scale on the experimental wear parameters, including the volumetric wear resistance of these materials. A complete software that has been developed implements a simplified version of the “blockon- ring” method for wear testing of materials, taking into account their hardness. The high correctness and efficiency of the proposed model is confirmed by the increasing hardness of a polytetrafluoroethylene composite filled with ultrafine diamond. Practical significance. The model of the relationship between the wear resistance and the hardness of materials proposed and justified in the paper is ready for use in their tests by the “block-on-ring” method in production conditions.

Polymer composites are one of the types of modern functional materials. This class includes many different in structure and field of application materials, including dispersed-filled polymer composites [1]. Such materials are made by mixing a polymer matrix in a fluid state with a powder filler and then curing. The properties of the resulting materials are influenced by a variety of factors, including the nature of the preliminary (prior to addition to the mixture with the polymer) mechanical-chemical processing of the filler.

In this paper a set of models is considered to describe the mechanism of ultra fast plasma propagation in silicon dioxide waveguide under the action of intense laser pulse. In particular, the paths via which the energy is absorbed are analyzed. For the first time, the absorption in the region ahead of the primary plasma front related to the medium fracture by the shock wave with magnitude greater than 30 k b a r is taken into account on the base of recently obtained experimental data. And it is clearly shown that this effect defines the propagation of the absorption wave with a speed ~ 3 k m / s that was observed experimentally and did not get an explanation yet. It is also shown that the competition between the energy absorption behind the shock wave and momentum losses due to transverse expansion defines the oscillations in the speed of absorption wave. The spatial period of oscillations depends unequivocally on the absorption length in the fractured region as well as on the fragments size. Obtained results can provide an interpretation of the unique experimental data on high-speed fracture of optical fibers under the action of intense laser pulse.

The kinetics of reactive ion etching of an Si, SiO2, and Si3N4 in the C4F8 + O2 + Ar mixture with a varied C4F8/O2 mixing ratio under the conditions of an rf inductive discharge (13.56 MHz) is investigated. Using the methods of plasma diagnostics and simulation, the data on the effect of the initial mixture’s composition on (a) the parameters of the electronic and ionic components of plasma and (b) the concentrations and densities of the fluxes of neutral species are obtained. It is established that nonmonotonic (with the maximum at ∼15% O2) changes in the etching rates for all three materials with an increasing O2 fraction in the mixture are provided by an increase in the atomic fluorine flux density with a simultaneous decrease in the effective probability of a heterogeneous chemical reaction with them. It is demonstrated that the behavior of the latter parameter does not reflect the changes in the kinetics of polymerization on the treated surface; however, this can be due to the heterogeneous processes involving oxygen atoms.

This paper presents a study of the influence of basalt rocks’ phase composition, acidity modulus, and structural parameter NBO/T on the tensile strength and elastic modulus of basalt continuous fibers (BCFs) derived from them. A series of BCF samples based on 14 different basalt deposits was obtained under equal conditions. The tensile strength and elastic modulus of the BCFs from different deposits vary in the ranges of 1495–3380 MPa and 58.2–78.7 GPa, respectively. Using the original method of quantitative phase analysis based on the Rietveld method, the phase compositions of the 14 deposits were defined. All deposits can be used to obtain BCFs. In the studied natural rocks, the main component is tectosilicates; the mass content of framework aluminosilicates is in the range of 16.5–3.3 mass percent. The second main component is inosilicates; the mass content of chain aluminosilicates is in the range of 6.0–58.0 mass percent. The correlations among phase composition, acidity modulus, ratio of non-bridging oxygens to tetrahedral cations, tensile strength, and elastic modulus of the BCFs from the 14 different basalt deposits were calculated. There were strong positive correlation between tectosilicate minerals mass content and elastic modulus [Pearson correlation coefficient (PCC) of 0.7] and strong negative correlation between content of chain and layered aluminosilicates and elastic modulus (PCC of − 0.74).

The results of studies of shot blasting as one of the methods of mechanical cleaning for surface hardening (peening) of parts are presented. The simulation in the QForm-3D (VX) software environment of high-speed impact of spherical particles on the metal was carried out and the stress–strain state of the metal in the impact hardening zone was revealed. It was shown that friction losses are proportional to the squared velocity of the particles of the shot blasting machine, and a decrease in the value of the contact friction coefficient will accordingly reduce the frictional work and increase the blades resource. Calculations and studies have established the basic laws of the shot blasting process conditions influence on the surface geometry and the metal surface layer properties.

A review of scientific publications and modeling of the effect of mechanical stresses on the sputtering yield of silicon by an ion beam is carried out. It is shown that the flux of atoms (from the depth to the surface) through interstitial or vacancy mechanisms due to the stress gradient caused by the limiting bending of the plate is insufficient to explain the increase in the sputtering coefficient. Calculations show that even the limiting elastic deformations do not significantly change the energy of atom detachment from the site, and an increase in the drift velocity of atoms due to the enrichment of the near-surface region with vacancies is insufficient to increase the sputtering rate. Consequently, it is necessary that the elastic deformation is transformed into plastic with the formation of mobile weakly bound atoms. The calculated stress distribution in a loaded silicon wafer using the COMSOL Multiphysics software package showed that the key driving force behind the increase in the silicon sputtering coefficient is the concentration of compressive and tensile stresses in the vicinity of the simulated crater during sputtering. The created crater is a stress concentrator, the gradients of which significantly exceed the values obtained by bending a plate without a crater. It is demonstrated that the generated stresses exceed the ultimate strength of the material in the vicinity of the crater, which begins to relax due to the expulsion of "excess" atoms in the tension region. The appearance of additional deformation-stimulated fluxes of weakly bound surface atoms at the bottom and walls of the crater provides an increase in the concentration of knocked-out atoms in the process of ion sputtering. Simulations predict an increase in sputtering yield of up to 40%. It is also shown that closely spaced craters, due to elastic interaction with each other, compensate each other's elastic fields, which has an effect on the value of the sputtering coefficient.

An influence of hyper-hardening on structure and mechanical properties of ceramic solid solutions (SS) Li0.12Na0.88TayNb1–yO3 with tantalum concentrations у = 0.05; 0.25; 0.4 has been revealed. The...

In this paper, we investigate the kinetics and mechanisms of reactive-ion etching of Si and SiO2 in the plasma of an HBr + O2 mixture with a variable initial composition under conditions of the high-frequency (13.56 MHz) inductive discharge. In the experimental and theoretical (model) analysis of the plasma parameters, the key plasma-chemical processes that form the stationary composition of the gas phase are identified and the densities of active particle fluxes onto the surface under processing are determined. It is found that the increase in the O2 concentration in the plasma-forming mixture is accompanied by a decrease in the kinetic coefficients (probability of effective interaction and etching yield) that characterize the heterogeneous stages of the etching process. It is assumed that the main mechanism of this effect is the oxidation of SiBrx etching products to low volatile compounds of the SiBrxOy type.

In this paper hydrodynamic processes arisen in the silica under laser action are analyzed numerically. Exactly these processes determine the development of fracture of optical fiber under the action of high-intense laser beams. The mathematical model describing the wave processes inside the core and cover of an optical fiber is proposed. It is shown that the basic mechanism of high-speed fracture wave propagation is related to the plasma expansion into the cold silica. At the same time, the transverse waves define the development of the plasma bubble and as a result the destruction of the optical fiber core. Obtained hydrodynamic mechanisms are basic for a wide class of scenarios related to the interaction of high-energy fluxes with solid medium.

This paper reports a process for the growth of optically homogeneous lithium niobate single crystals containing boron as a dopant. A LiNbO3:B crystal has been grown by the Czochralski technique using a single-phase growth charge synthesized from a Nb2O5:B precursor and lithium carbonate. We have assessed the optical quality of the crystal by a high-speed method from the number of scattering centers, evaluated its single-domain state by piezoacoustic measurements, and calculated its d333 piezoelectric modulus component. The results demonstrate that the crystal has a high degree of optical uniformity and is single-domain. The proposed method for LiNbO3:B crystal growth can serve as a basis of a commercial-scale process for the preparation of doped lithium niobate single crystals for various engineering applications.

A procedure has been developed for calculating the geometric, kinematic and energy-power parameters of helical rolling, which allows a comparative analysis of the processes carried out in stands of various designs. Based on the results of this analysis, a helical rolling mill was designed and manufactured which allows to roll materials with high deformation resistance at high temperatures. The results of the study of the mechanical characteristics of molybdenum bars and wires made by new technology are presented.

The effect of Ar/O2 mixing ratio on gas-phase characteristics and SiO2 etching kinetics in CF4 + Ar + O2 and C4F8 + Ar + O2 plasmas was studied under conditions of 13.56 MHz inductive RF discharge. The constant processing parameters were fraction of fluorocarbon component in a feed gas (50%) total gas pressure (6 mTorr), input power (700 W) and bias power (200 W). It was found that the full substitution of Ar for O2 in both gas systems results in non-monotonic (with a maximum at ~ 25% Ar + 25% O2) SiO2 etching rates as well as in monotonically increasing photoresist etching rate with higher absolute values for CF4-containing mixture. The steady-state densities of active species were determined using a combination of plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling. Corresponding results indicated that both gas systems are characterized by quite close parameters of electron and ion components while exhibit sufficient differences in the kinetics of neutral species, especially in the presence of O2. The latter produces opposite changes in F atom density as well as in effective probability of ion-assisted chemical reaction vs. Ar/O2 mixing ratio. Relationships between type of fluorocarbon component and heterogeneous process kinetics were analyzed through the set of gas-phase-related parameters (fluxes, flux-to-flux ratios) characterizing chemical etching pathways for SiO2 and formation/destruction balance for the fluorocarbon polymer film. It was suggested that the transition toward O2-rich plasma in the low-polymerizing CF4 + Ar + O2 plasma suppresses the effective probability for SiO2 + F reaction through decreasing efficiency for oxide bond breaking and desorption of etching products due to decreasing ion energy flux. Oppositely, an increase in O2 content in the high-polymerizing C4F8 + Ar + O2 mixture lifts up the effective reaction probability by decreasing fluorocarbon film thickness and providing better access of F atoms to the etched surface.

The effect of the O2/Ar component ratio in the CHF3 + O2 + Ar mixture on the electrical parameters of the plasma, kinetics of active particles, and their stationary concentrations under the high-frequency (13.56 MHz) induction discharge is investigated. Using jointly the plasma diagnostics and simulation techniques, (i) features of the plasma composition in the oxygen-free system CHF3 + Ar are found, (ii) the effect of oxygen on the stationary concentrations of active particles is established via the kinetics of processes under the electron impact and the reaction of the atom–molecule interaction, and (iii) a simulation analysis of the kinetics of heterogeneous processes (etching, polymerization, and destruction of a polymer film), which determine the etching mode and output characteristics, is carried out.

—Improved methods and devices for nondestructive control of the degree of unipolarity of large LiNbO3 crystals are described. These methods are based on measurements of the static and dynamic piezoelectric characteristics of crystals and are applicable to other ferroelectric materials. These methods allow assessment of the degree of unipolarity and the relative volume of antiparallel domains in crystals.

In this work, we investigated the possibidlxlity to control both gas-phase chemistry and silicon etching kinetics in C4F8 + O2 + Ar inductively coupled plasma by changes in O2/Ar, C4F8/O2 and C4F8/Ar mixing ratios at the constant fraction of the rest component (50%), gas pressure (10 mTorr), input power (700 W) and bias power (200 W). The combination of plasma diagnostics and modeling tools allowed one: (a) to compare the effects of gas mixing ratios on both steady-state plasma parameters and densities of active species; (b) to figure out key processes which determine the fluorine atom formation/decay balance in each gas system; and (c) to analyze the differences in Si etching kinetics in terms of process-condition-dependent effective reaction probability. It was shown that the maximum changes in gas-phase chemistry take place in O2-rich plasmas due to CFx + O/O(1D) → CFx−1O + F, CFxO + e → CFx−1O + F + e and CFO + O/O(1D) → CO2 + F stepwise dissociation pathways. It was suggested also that the effective probability for Si + xF → SiFx reaction may be controlled by either fluorocarbon film thickness (in C4F8—rich plasmas) or O atom flux (in Ar and O2—rich plasmas) through the balance of adsorption sites on the etched surface.

The effect of Ar/O2 mixing ratio on plasma parameters, steady-state densities of active species and SiO2 etching kinetics in the three-component C4F8+Ar+O2 gas mixture was studied under typical conditions of reactive ion etching process (inductive 13.56 MHz RF discharge, total gas pressure of 6 mTorr, input power of 700 W and bias power of 200 W). The investigation combined etching rate measurements, plasma diagnostics by Langmuir probes and 0-dimensional (global) plasma modeling in order to determine steady-state densities and fluxes of plasma active species. It was found that the full substitution of Ar for O2 at constant fraction of fluorocarbon gas (in fact, the transition from 50% C4F8 + 50% Ar to 50% C4F8 + 50% O2 gas system): 1) results in weakly non-monotonic (with a maximum) SiO2 etching rate with close values for both O2-free and Ar-free plasmas; 2) causes the monotonic decrease in both F atom flux and ion energy flux; and 3) suppresses the formation of the fluorocarbon polymer film on the etched surface through its oxidative destruction pathway. The model-based analysis of SiO2 etching kinetics allowed one to conclude that an increase in effective probability for SiO2 + F reaction contradicts with the behavior ion energy flux as well as demonstrate the agreement with the change in gas-phase parameters characterizing the fluorocarbon film thickness. Therefore, an increase in O2 content in a feed gas influences the effective reaction probability by decreasing fluorocarbon film thickness and providing better access of F atoms to the etched surface.

The comparative research of the parameters, steady-state composition, and the effects of heterogeneous interaction in the plasma of fluorocarbon gases CxHyFz with various z/x relations in conditions of an induction RF (13.56 MHz) discharge is carried out. The binary systems CxHyFz + Ar based on CF4 (z/x = 4), CHF3 (z/x = 3), and C4F8 (z/x = 2) are used as the subjects of research. Through the methods of diagnostics and simulation of plasma we found (a) the reasons of the differences in the physical parameters (temperature and density of electrons, energy of ion bombardment) of the plasma in the studied systems; (b) the special characteristics of the kinetics of the plasma-chemical processes determining the steady state concentrations of fluorine atoms and polymer-forming radicals; and (c) the special characteristics of the kinetics of the heterogeneous process forming the output parameters (rate, selectivity, anisotropy) of the reactive ion etching of Si and SiO2.

It is established that when physical modifications to the blown film of LDPE in extrusion installation for large values of the ratio of the longitudinal drawing of the melt, Km from 7.2 to 12.4, there is the technological anisotropy Kat in the range of 2.8 to 3.7. It is 1.8 times higher than the anisotropy of strength of Kaσ films. At uniaxial tension of such films in polarized light, the appearance of isochromes associated with the value of Kat is observed.

Objectives. This study is devoted to developing new-generation nickel (Ni) catalysts for the purification of a nitrogen–hydrogen mixture from carbon oxides, which should encompass the best qualities of the NIAP-07-series solid catalysts. Methods. This study used derivatographic and radiographic methods; temperature-programmed recovery, decomposition, and joint temperature-programmed decomposition and recovery; and low-temperature nitrogen adsorption (specific surface determination). The mechanical strength of catalysts was determined using an MP-2C device by crushing granules with an applied load on the end face. The chemical composition and catalytic activity were determined by the methods of TU 2178-003-00209510 Technical Conditions. Results. Many studies regarding Ni–aluminum (Al)–calcium (Ca) methanation catalyst at all stages of its preparation have been conducted. It is demonstrated that Ni hydrocarboxyaluminate, a precursor of the active component of the catalyst, is formed when Ni hydroxocarbonate is mixed with active alumina in the presence of an aqueous solution of ammonia, and its chemical formula is established. Moreover, it was found that the mechanical strength of the catalyst is determined by the amount of industrial Ca aluminate added to the Ni–Al composition. The compositions of catalysts with different contents of the active component have been optimized. Conclusions. The developed catalyst has a low activation temperature and high catalytic activity, thermal stability, and mechanical strength and is resistant to organic and alkaline carbon dioxide absorbers. The catalyst can be produced in the form of a ring, cylindrical tablets, and extrudates of various geometric sizes. The methanation unit at Stavrolen (Budennovsk, Stavropol krai, Russia) has begun commercially operating the catalyst.

In high-pressure gas–jet Hartmann generators, the source of acoustic energy is kinetic energy of a gas jet by the supercritical ratio between the operation and ambient pressure. Under certain conditions, onflow of a supersonic jet to a resonator is accompanied by powerful self-sustained oscillations with irradiation of acoustic waves into the environment and resonator cavity. A model of a self-oscillating process arising from the interaction of a nonisobaric jet with semi-closed cylindrical cavities is considered, which allows one to identify typical elements of the gas-dynamic structure of the forming flow. The physical pattern of the flow in the gas–jet generator has been discussed and the study of the dependence of the self-sustained oscillation characteristics on the key gas-dynamic and geometric parameters has been performed.

The influences of both HBr/O2 (at constant Cl2 fraction) and Cl2/O2 (at constant HBr fraction) ratios in HBr + Cl 2 + O2 gas mixture on bulk plasma characteristics, active species densities and etching kinetics of silicon were studied. The results indicated that an increase in O2 content in a feed gas at constant Cl2 fraction in a processing gas (1) produces the stronger impact on plasma chemistry by the influence on the kinetics of electron-impact and atom-molecular reaction; and (2) provides the wider adjustments for both halogen atom flux and ion flux with the opposite tendencies with those for variable Cl2/O2 mixing ratio. The experiments demonstrated that the transition toward more oxygenated plasmas in both cases lowers the Si etching rate as well as result is decreasing effective reaction probability and etching yield. These effects may be associated with decreasing amount of adsorption sites for Cl/Br atoms as well as increasing sputtering (ion-stimulated desorption) threshold for reaction products due to the formation of the low-volatile silicon oxy-chlorides and-bromides in heterogeneous SiClx + O/OH and SiBrx + O/OH reactions.

LiTaO3 ceramics has been produced from a fine powder synthesized by a sol-gel method from a Li,Ta-containing citrate precursor, and its microstructure and mechanical and electrical properties have been studied. Young’s modulus and microhardness of the ceramic lithium tantalite have been determined. The critical stress intensity factor of mode I KIC, which is a criterion for the crack resistance of a material, has been evaluated, and the effective fracture energy of the LiTaO3 ceramics has been determined. The complex impedance dispersion Z*(ω) has been studied, and temperature dependences of dielectric constant and conductivity have been measured in the temperature range ~300–705 K, which is crucial for the acoustoelectronic applications of ceramic lithium tantalate. In the temperature range studied, the static conductivity and relaxation time of LiTaO3 ceramics have been determined. The charge transport activation enthalpies for various temperature ranges have been estimated.

The investigation of etching kinetics and surface conditions for KNbxOy thin films in CF4 + Ar and Cl2 + Ar inductively coupled plasmas was carried out. The variable processing parameters were Ar content in a feed gas (0–75% Ar), gas pressure (4–10 mTorr) and input power (400–700 W) at constant bias power of 100 W. The combination of plasma diagnostics by Langmuir probes and plasma modeling provided the data on internal plasma parameters, gas-phase chemistry and steady-state densities of plasma active species. The compositional changes of the etched surfaces were investigated using X-ray photoelectron spectroscopy (XPS). It was found that the fluorine-based etching chemistry provides the much lower halogen atom flux together with the much higher KNbxOy etching rate under the condition of quite close ion momentum fluxes in both gas systems. The correlations between measured etching rates and model-predicted fluxes of active species suggested the neutral-flux-limited etching regime with the much lower effective reaction probability between KNbxOy and Cl atoms. The last effect may be related to lower volatility of NbClx compared with NbFx (that is confirmed by XPS data) as well as to the higher energy threshold for KNbxOy + Cl reaction.

Despite the growing demand for hydrogen peroxide it is almost exclusively manufactured by the energy-intensive anthraquinone process. Alternatively, H2O2 can be produced electrochemically via the two-electron oxygen reduction reaction, although the performance of the state-of-the-art electrocatalysts is insufficient to meet the demands for industrialization. Interestingly, guided by first-principles calculations, we found that the catalytic properties of the Co–N4 moiety can be tailored by fine-tuning its surrounding atomic configuration to resemble the structure-dependent catalytic properties of metalloenzymes. Using this principle, we designed and synthesized a single-atom electrocatalyst that comprises an optimized Co–N4 moiety incorporated in nitrogen-doped graphene for H2O2 production and exhibits a kinetic current density of 2.8 mA cm−2 (at 0.65 V versus the reversible hydrogen electrode) and a mass activity of 155 A g−1 (at 0.65 V versus the reversible hydrogen electrode) with negligible activity loss over 110 hours. Producing H2O2 electrochemically currently use electrocatalysts that are insufficient to meet the demands for industrialization. A single-atom electrocatalyst with an optimized Co–N4 moiety incorporated in nitrogen-doped graphene is shown to exhibit enhanced performance for H2O2 production.

The work is devoted to the study of the rheological behavior of proppant carrier fluids used for hydraulic fracturing (HF) technology in order to increase oil recovery, including from hard-torecover oil and gas reserves, in a wide range of deformation rates using viscometers of various designs. Rheological properties were studied for proppant carrier fluids based on guar and Surfogel grade D, (type 70–100, produced by JSC “Polyex”) with comparable shear rate 128 s–1. Quasistatic experiments to determine the values of the dynamic viscosity of the liquids under study were carried out using a falling ball viscometer (according to the Stokes method). Using an original viscometer, consisting of two coaxial cylinders (rotary rheometer), the dynamic viscosity of surfogel was investigated in a wide range of shear rates. The viscoelastic properties of surfactants were studied using a Physica MCR501 rheometer, which has a plane-to-plane measuring system and allows rheological studies in rotational and oscillatory modes. A comparison of the rheological properties of fluids based on the guar and the viscoelastic surfactant is carried out and it is established that a fluid based on the viscoelastic surfactant has a higher dynamic viscosity and does not lose its elastic properties, which is an certain advantage over a fluid based on the guar.

In the article the results of the finite element modeling of cold extrusion of carbon steel, the stress-strain state of massive dies at high cyclic stresses characteristic of the cold extrusion of steel are presented. The possibility of significant amplification of dies in their working area by creating a variable external pressure from the rims of a special design is shown. Dies banding with variable external pressure, proportional to the internal pressure in the die, is aimed at increasing the technical resource of the tool.

Numerical simulation of the fiber optic parametric oscillator aiming the goal to produce picosecond narrowband pulses for CARS has been performed in an extremely wide range of parameters, such as a pump pulse duration, parametric frequency shift, spectral bandwidth of the pump and the parametric pulses. It required extremely large calculation window both in time (3.5 ns) and spectral (from 433 nm to 3100 nm) domains. We managed to speed up simulation in fifty times by graphic processor unit, which allowed to define the areas of stability for different lengths of standard passive and photonic-crystal fibers used in the external linear cavity of oscillator. The cavity length reached a value of 100 meters that was resulted in parametric pulses with the energy up to 40 nJ and peak power up to 1 kW at a wavelength about 800 nm.

Application of poly-N-isopropylacrylamide (PNIPAM) and its more hydrophobic copolymers with N-tert-butylacrylamide (NtBA) as supports for cell sheets has been validated in numerous studies. The binary systems of these polymers with water are characterized by a lower critical solution temperature (LCST) in a physiologically favorable region. Upon lowering the temperature below the LCST, PNIPAM chains undergo a globule-to-coil transition, causing the film dissolution and cell sheet detachment. The character of the PNIPAM-water miscibility behavior is rather complex and not completely understood. Here, we applied atomic force microscopy to track the phase transition in thin films of linear thermoresponsive (co)polymers (PNIPAM and PNIPAM-co-NtBA) prepared by spin-coating. We studied the films' Young's modulus, roughness, and thickness in air and in distilled water in a full thermal cycle. In dry films, in the absence of water, all the measured parameters remained invariant. The swollen films in water above the LCST were softer by 2-3 orders of magnitude and about 10 times rougher than the corresponding dry films. Upon lowering the temperature to the LCST, the films passed through the phase transition observed as a drastic drop of Young's modulus (about an order of magnitude) and decrease in roughness in both polymers in a narrow temperature range. However, the films did not lose their integrity and demonstrated almost fully reversible changes in the mechanical properties and roughness. The thermal dependence of the films' thickness confirmed that they dissolved only partially and required an external force to induce the complete destruction. The reversible thermal behavior which is generally not expected from non-cross-linked polymers is a key finding, especially with respect to their practical application in cell culture. Both the thermodynamic and kinetic factors, as well as the confinement effect, may be responsible for this peculiar film robustness, which requires overcooling and the aid of an external force to destroy the film.