卷 64, 编号 5 (2019)

The self-induction of a thin cylindrical metallic wire has been calculated. A general case when the ratio of the electron free path to the wire radius may take an arbitrary value has been considered. The dependence of the regular reflectance on surface defect density and angle of incidence of electrons on the wire’s inner surface has been taken for boundary conditions of the problem.

Barodiffusion in slow flows of a gas mixture is studied with an approximation using hydrodynamic equations of motion for the individual mixture components. It is shown that consideration of the viscous momentum transfer and the contribution of Knudsen layers for the mixture flowing in a channel has a considerable effect on the value of the barodiffusion factor. The relations are obtained for the mean diffusion fluxes of components and for the total flux of the mixture in a circular cylindrical capillary; these relations are valid for moderately small Knudsen numbers used for calculation of the diffusion baroeffect and separation effect when the gas mixture flows in a set of capillaries connecting two volumes. The modification of the relations for the barodiffusion factor (and for the diffusion slip coefficient cross-linked with it) allows interpreting the sign alteration of these effects observed experimentally for some gas mixtures at intermediate Knudsen numbers.

Fluctuations of the poloidal component of the plasma magnetic field in the frequency range of 0.5–50 kHz are studied in the Uragan-3M (U-3M) torsatron. Hydrogen plasma is produced and heated by RF fields at frequencies close to that of the ion cyclotron. The studies are carried out using a set of 15 magnetic sensors installed in one of the torus cross sections. RF heating provided the plasma with rare collision frequencies and the presence of the bootstrap current. The study is carried out when the maximum amplitude of magnetic fluctuations is observed and their connection with the plasma energy content is noticeable. Two types of vibrations are observed. In the first type, the current structure rotates with a certain frequency mainly in the direction of the rotation of electrons in the magnetic field, and the amplitude varies slowly with time (the rotating structure). For the second type, the spatial structure does not rotate, but its amplitude changes with a certain frequency (the standing structure). The frequencies of fluctuations and rotations are close for structures with a given poloidal wave number. The standing vibration structures with different poloidal wave numbers in this frequency range are correlated. The maximum amplitude of the rotating structures is observed with m = 2, and for the standing structures with m = 3 and reaches the values of \(\tilde {B}\) ≤ 0.3 G in the confinement region. The vibration frequency does not depend on poloidal wave number m for the studied cases; m = 0, 1, 2, 3.

Analysis of the dependence of the break-down point of granite on the temperature of microwave heating allows identification of the following characteristic areas: hardening is observed at low temperature heating up to 390 K; a decrease in strength appears in the temperature range from 390 to 460 K, which is due to generation, growth, and coalescence of smaller cracks and their redistribution to the boundaries of grains with the formation of intergranular microcracks; there is a significant decrease in the strength at the temperature range from 460 to 550 K, which is caused by the separation of grains into blocks with a small area of crack density as a result of their coalescence, and the destruction and splitting of granite samples occurs at temperatures above 593 K due to the development of all kinds of microcracks. The developed method of determining the rational parameters of the microwave energy impact on the softening of hard rocks in the field of standing electromagnetic waves allows justification of the effective parameters of the impact of microwave energy on quartz-containing hard rocks for their softening and destruction based on the study of the dynamics of induced microcracks.

The anisotropy of magnetoelectric properties of lead zirconate–titanate and nickel ferrite based bulk composites has been experimentally studied. It has been shown that a ratio of longitudinal to transverse magnetoelectric coefficients is affected by the piezoelectric constant of a composite. The mechanism that explains the obtained dependences has been suggested; the mechanism is based on the assumption that the anisotropy of magnetic properties is caused by the deformation occurring at electric polarization of a sample.

The results of penetration of a high-speed metal jet (with a velocity of 3–7 km/s) into brittle materials (ceramics and glass) have been analyzed. The data on jet destabilization as a result of the response of the brittle material to the high-speed penetration are presented. The generalized dependence of the high-speed jet absorption efficiency on the bending strength of the brittle material has been constructed in the hydrodynamic approximation.

In this paper, we propose a new principle of high-performance 3D printing for non-ferrous metal melts. The crystallization temperature may increase in the lower part of the tapering jet of liquid metal due to the pressure produced by the Ampere forces caused by a specially applied current. The fundamental possibility of this crystallization with regard to additional heating produced by this current was studied. The introduction of ferromagnetic additives was found to allow creating a range of parameters in which such crystallization is possible.

Negative electrodes for lithium-ion batteries prepared by electrochemical etching of single-crystalline silicon crystals demonstrate a high specific capacity per gram of the material and per unit of nominal anode area as well as a high stability during several hundreds and even thousands of cycles. However, industrial application of such structures is inexpedient in view of the high cost of the material and technology used. In this work we have investigated anodes based on disordered macropores in solar-grade n-Si obtained by photoanodization in a 4% HF solution in dimethyl formamide. The use of this organic electrolyte leads to the formation of layers with a porosity higher than in an aqueous electrolyte and ensures spontaneous separation of these layers from the substrate. The anodes have been prepared from macroporous membranes with a thickness of 48–86 μm and a porosity of 52–75%, and their electrochemical parameters have been studied. It is found that the geometrical parameters of the porous structure and experimental conditions determine the charge and discharge capacity and the cycle life of the anodes. In the regime of the charge capacity limited by 1000 mA h/g and charge/discharge rate C/5, the obtained anodes can stably operate during several hundreds of cycles, preserving a high (greater than 98%) Coulombic efficiency.

Two series of shock-wave experiments have been conducted in order to measure the Hugoniot elastic limit and determine the strain rate dependence of critical fracture stress for tantalum experiencing spall fracture. Tantalum specimens have been preannealed in vacuum at 1000°C. The evolution of elastoplastic compression shock waves at room and elevated up to 500°C temperatures has been presented from complete wave profiles recorded by a VISAR laser Doppler velocimeter. The spall strength dependence on the strain rate during the expansion of the material in a rarefaction wave has been determined.

We have studied experimental samples of photoelectric transducers with an n⁺–p junction based on a silicon single crystal and an antireflection porous silicon (por-Si) film formed by color chemical etching in a HF : KMnO₄ : C₂H₅OH etcher. It is shown that for KMnO₄ oxidant concentrations of 0.025 and 0.040 M, the por-Si film growth time at which the maximal efficiency of the photoelectric transducer is reached can be substantially increased as compared to that attained using anode electrochemical etching. For investigating the current transmission mechanisms, we have measured the temperature dependence of forward- and backward-bias current–voltage branches. The existence of several current transmission mechanisms has been established. It is found that traps with activation energy distributed in a continuous range of values considerably affect the current transmission.

Fabrication of composites based on micro- and nanostructured hybrid polymers have been studied. A new technology for nanoparticle immobilization in the polymer matrix of the composite has been suggested. Its essence is to produce functional electronegative polymer segments in the polymer matrix, which are the main agents preventing nanoparticle mobilization in the polymer phase of a composite.

Radiation-induced absorption (RIA) of light in five isotropic optic fibers (OFs) with a core of undoped silica glass (SiO₂) and a fluorosilicate cladding and one birefringent OF of the “PANDA” type of the same chemical composition was measured at a wavelength λ = 1.55 μm under γ-irradiation to a dose of 1 kGy (∼ 1 Gy/s), 15–45 min after completion of irradiation, and in a few months at temperatures +25 and –60°C. An extrapolation of the RIA after irradiation in the framework of the kinetic model of the nth order, which gave a forecast of the RIA for isotropic OFs of ∼1.1 and ∼ 0.3 ± 0.1 dB/km at –60 and +25°C, respectively, was made to assess the RIA at the end of a 15-year mission in space. It has been concluded that it is possible to use at least 4–5 km of OF in space under conditions of temperature variation within ±60°C at a maximum dose of 1 kGy and a mission duration of 15 years. It has also been established that the RIA will not have been higher in the birefringent OF than in the isotropic ones by the end of such a mission.

Optimum conditions for ion implantation and subsequent annealing for the fabrication of NiSi₂/Si (111) nanofilms with a thickness of 3.0–6.0 nm are determined. It is demonstrated that the energy-band parameters and optical properties typical of thick NiSi₂ films start to set in at d = 5.0–6.0 nm.

High-resolution X-ray diffraction method (XRD) is used to determine sizes and crystallographic orientation of the nanocrystallites of the Pd and Pd₅Ba phases in palladium–barium cathode. Electron spectroscopy for chemical analysis (ESCA) is used to study Ba and Pd chemical states in cathode material and determine the phase composition including dissolved microimpurities in the phases. The comparison of the XRD and ESCA data makes it possible to reveal effects related to the formation of the BaO crystallites in the cathode material, which are responsible for the emission properties. Electron-energy loss spectroscopy is used to determine the concentration of oxygen vacancies in the BaO crystallites that are formed in the cathode material due to activation. An original crystallite model of the working palladium–barium cathodes that is based on the results of this work may serve as an alternative to the known film model and makes it possible to optimize technology of cathode fabrication and activation.

The results of calculation of fluxes of ultracold (UCNs), very cold, and cold neutrons at the output of neutron guides of the UCN source with superfluid helium at the WWR-M reactor are presented. UCN density ρ_35L = 1.3 × 10⁴ n/cm³ in the trap of the electric dipole moment (EDM) spectrometer was obtained by optimizing source parameters. This UCN density in the EDM spectrometer is two orders of magnitude higher than the UCN density at the output of the available UCN sources. The flux density of cold neutrons with a wavelength of 2–20 Å at the output of a neutron guide with a cross section of 30 × 200 mm² should be as high as 1.1 × 10⁸ n/(cm² s), while the flux density of very cold neutrons (50–100 Å) at the output of the same neutron guide should be 2.3 × 10⁵ n/(cm² s). An extensive program of fundamental and applied physical research was mapped out for this source.