Том 61, № 11 (2019)

The paper presents the experimental results of mechanical activation, annealing and thermal treatment of Nb– 2Si powder blend. It is shown that mechanical activation intensifies the phase formation in the powder blend and facilitates its more complete transformation into the reaction product of stoichiometric composition at a stage of thermal treatment.

The paper considers carbyne nanostructures as filtering members for separation of gas mixtures based on selective adsorption of its components, in particular, hydrogen, helium and methane. The size of a highlyselective cell is determined in this paper. It is found that the number of layers in carbyne membrane has no effect on the selective separation of gas mixtures.

Possible improvement of mechanical properties and fracture toughness of low-alloy steel API 5L X52 after helical rolling under the conditions of cooling rate variations is analyzed. Upon helical rolling and air cooling (Regime I), the average ferrite grain size in this steel is observed to decrease from 13.5 μm in the initial state to 3.5 μm, the volume fraction of pearlite also decreases, the banded orientation disappears, and the structure becomes more homogeneous. The structural changes provide an increase in the yield stress value from 270 to 430 MPa and strength from 480 to 630 MPa, with the plasticity remaining at the initial level (ε = 25%). Simultaneously, the impact toughness value (KCV) increases in the entire temperature interval by about 30%, compared to that in the initial state, and the critical temperature of brittleness Т₅₀ is shifted towards the region below –70°С. After rolling of low-alloy steel X52 and water quenching (Regime II), a ferrite-bainite structure is formed. Regime II favors an increase in the yield strength of the steel by a factor of 1.6, while the level of KCV slightly decreases.

The paper studies the high-temperature plastic deformation in Ni₃Ge alloy single crystals localizing in a band a few tens of microns wide that reaches the shear strain of thousands of percent. The electron backscatter diffraction and synchrotron radiation techniques allow investigating the structure of the single crystal in the band of super-localized plastic deformation. It is shown that super-localization of plastic deformation occurs due to the formation of polycrystalline multi-level substructure in the initial single crystal. The grain size and grain misorientation bimodal distributions are determined in the polycrystalline substructure. Also, regions of amorphous state are observed in the super-localization band at high homologous temperature Т > 0.5T_m. A partial destruction of the far atomic order is detected.

Elemental compositions and structure-phase states of titanium nitride coatings on the flat surface and in a cut of substrate from 10Cr18Ni10Ti steel are investigated by the methods of x-ray microspectral analysis, Auger electron spectroscopy, and dark-field electron microscopy analysis of the bending-torsion of the crystal lattice. It is established that the coating in the cut, unlike the coating on the frontal surface, has a modified elemental composition and a two-layer structure whose special features and thicknesses change with distance from the sample surface. It is shown that these changes are caused by phase transformations, decreased number of defects, dispersion of layer structures, and increased concentration of impurities with increasing distance from the substrate surface. Based on the results obtained, possible conditions for coating structure formation in the cut of the substrate surface are discussed.

A detailed electric model of current transmission through vestibular labyrinth tissues is suggested based on the anatomic structure of the labyrinth taking into account electrophysical properties of hair and basilar cells of neuroepithelium. Formulas for the impedance of the vestibular organ are derived and phase shifts of the stimulating current are calculated based on experimental data on the electrophysical and anatomic characteristics of vestibular labyrinth tissues of a guinea pig. The dispersion of the impedance is investigated for the frequencies in the range 10¹–5·10⁴ Hz. It is shown that the phase shift of the current relative to the voltage applied between the electrode and the vestibular nerve is nonmonotonic in character and depends on the frequency. A minimum negative phase shift of the current is observed at f = 200 Hz. Taking into account of the cellular structures of the hair and basilar cells in the electric circuit shows that in the examined frequency range they bring significant contribution to the total impedance. The suggested electric model and the results of calculations can provide the basis for diagnostics of vestibular labyrinth diseases and design of vestibular implants of a new type.

A method of visualization of the process of optical damage of a ZnGeP₂ single crystal using digital holography is suggested. The mechanism of the ZnGeP₂ single crystal damage is investigated at energy density ~0.3–0.6 J/cm². The temperature in the damage channel during its formation is estimated. The data obtained allow the conclusion on the thermal nature of ZnGeP₂ crystal damage to be made under the action of laser radiation with a wavelength of ~2.1 μm.

Results of investigation of spectral-luminescent and lasing characteristics of substituted 1,3-oxazoles and 1,3,4-oxadiazoles lasing in the blue-green spectral region are presented. For some compounds, efficiencies of 40 and 38% have been achieved with pump power density of 7 MW/cm². A 34 nm wide tuning range in the blue-green spectral region with lasing line width of 0.012 nm is shown. A series of laser-active compounds with good solubility in methyl methacrylate capable of effectively lasing is determined.

A concept of a hybrid plasma source to be used as a micro satellite thruster is proposed, where the propellant is a liquid gallium–indium alloy. The plasma source operates in two modes: 1) generation of laser ablation plasma and 2) generation of plasma in a laser-triggered, low-voltage vacuum-arc discharge. The cathode in the discharge cell of the source represents a stainless-steel capillary filled with the working liquid. The laser beam target is the working liquid meniscus. Without any voltage in the discharge gap, only laser-ablated plasma is generated. Upon application of even a relatively low voltage (<1 kV), the ablation initiates a high-current vacuum-arc discharge. In the experiments, the discharge current and voltage waveforms were recorded and so were the images of plasma glow obtained with a HSFC-Pro 4-channel high-speed camera. Regularities of current flow in the high-current vacuum-arc discharge, initiated by the cathode laser ablation, are investigated.

On the basis of the modified potential two-cluster model with forbidden state which effectively take the Pauli principle into account, calculations have been performed of the astrophysical S-factor of radiative p¹⁴N capture to the ground state of the ¹⁵O nucleus at proton energies up to 5 MeV in the center-of-mass system (c.m.s.) with allowance for wide resonances up to 3.4 MeV in the c.m.s. For an acceptable explanation of the available experimental data it is necessary to allow the existence of the ¹⁴N cluster in the excited state ¹⁴N^* at an excitation energy of 5.69 MeV and angular momentum J^π = 1^–. It is assumed that in such a case it is possible to use the wave function of the ⁴D_1/2 state with respect to the relative motion of the p¹⁴N^* clusters. It is also shown that a description of the S-factor of p¹⁴N capture in the resonance region is possible only under the assumption that all of the low-lying resonances at 260(1/2⁺), 987(3/2⁺), 1447(1/2⁺), 2187(3/2⁺), and 3211(3/2⁺) keV in the c.m.s. are ⁴D_1/2 and ⁴D_3/2 scattering waves.

For the depletion and accumulation modes, equivalent circuits of MIS structure based on an organic P3HT thin film with an Al₂O₃ insulator are proposed. The frequency dependences of the capacitance and conductance of an organic MIS structure were simulated at a temperature of 300 K in the frequency range of 20 Hz – 2 MHz. It is shown that the measured values of the capacitance and conductance substantially depend on the thickness of the insulator layer, the thickness and specific conductance of the organic film, the parameters of surface traps, the frequency and bias voltage. Methods for determining the values of the basic elements of the equivalent circuit for the correct characterization of traps at the inorganic insulator – organic film interface are described.

Results of investigation of conversion of radiation with the wavelength λ = 950 nm and pulse duration of 100 ps into the second harmonic are reported. It is demonstrated that the second harmonic pulse duration is half the pulse duration at the fundamental frequency. The converted radiation linewidth remains unchanged. The beam quality factor М² increases from 1.16 to 1.56. The maximal conversion efficiency is 12.2%.

Coherent transition radiation (CTR) is widely used in determining the longitudinal e-beam dimensions in the accelerator technology applications. In this study, the CTR process is investigated in a real Au-target for the sake of measuring the size characteristics of the electron bunches with lengths from 100 to 300 nm, and possible applications of such targets is demonstrated.

The energy of a two-dimensional two-electron atom is calculated in its lowest excited states; together with the previously calculated energy in the ground state, this makes it possible to find the screening constant σ in the lowest excited state and the fundamental frequencies of radiation of such atoms (for example, Не), which can, in principle, be obtained in the Bose condensate phase as has already been done with Na atoms. The possibility of experimental verification of the results is indicated. Errors incurred by other authors in their calculations of σ in the excited state of the two-dimensional He atom are also pointed out.

The article describes circuit schematics, features and design methodology of microwave integrated digital step attenuators (DSAs) based on SiGe technology (SiGe BiCMOS). The measured characteristics of the designed 0.1–4.5 GHz microwave monolithic integrated circuit (MMIC) DSA with a parallel and serial control driver are presented. The DSA bitness is 6 bit, attenuation range is 30 dB with a 1-dB step, and input power at the 1 dB gain compression is no less than 14 dBm. In addition to the wide bandwidth, advantages of the MMIC DSA are a good input and output matching, as well as low consumption current. The MMIC DSA can be used in microwave transmitters and receivers for different applications, including ones that are based on the systemon-a-chip concept.