卷 42, 编号 1 (2016)

Single crystals of polyelemental rare earth hexaborides with the preset formula La_0.5(Ce_0.1Pr_0.1Nd_0.1Sm_0.1Eu_0.1)B₆ were obtained for the first time. Synthesis and crystallization were performed by the solution–melt method in an immiscible Al/Pb system. Step-by-step chemical analysis was made with the aid of a CAMEBAX microprobe. The inclusion of all rare earth metals (REMs) in the hexaboride lattice was proven, and differences in the composition of obtained crystals caused by nonstationarity of the bulk crystallization process were found. The lattice periods of the polyelemental REM hexaborides were found to be smaller than that of hexaboride of lanthanum, the main element of the metal sublattice. The measured microhardness of the new material lies within the range of the microhardness values of hexaborides of all its constituent REMs. Speculations are provided on the peculiarities of the growth mechanism, crystallization, and composition of the obtained crystals.

We have obtained general expressions for the intensity of radiation and tangential force of a small polarizable particle in the process of translational–rotational motion in equilibrium radiation background (thermalized photon gas) of a certain temperature at an arbitrary relative orientation of the linear and angular velocity vectors. It is shown that, in a cold vacuum background, the translational velocity of particle is independent of time and the intensity of its spontaneous emission is determined by the angular velocity and imaginary part of the particle polarizability.

Oblique shock waves can be reflected from hard walls, the axis, or the plane of symmetry, as well as from other counterpropagating shock waves with the formation of regular and Mach shock wave configurations. The specific form of shock wave structures is determined by the parameters of the problem: Mach number and intensity of incident shock waves. On the plane of parameters, there exists an ambiguity area in which laws of conservation admit both the regular and Mach reflection of shock waves. The boundaries of this region have been determined.

Heterojunction photovoltaic cells with a photoactive layer composed of a mixture of a silane copolymer with a fullerene derivative PC₇₀BM have been fabricated, and their working characteristics have been measured. Data obtained by cyclic voltammetry were used to construct the energy level diagram for the cell components. Analysis of the diagram and photoelectric characteristics of the photovoltaic cell made it possible to find ways to improve its efficiency.

The effect of hydrogenation of thin films of vanadium dioxide by plasma-immersion ion implantation on their conductivity is characterized. It is demonstrated that the parameters of the metal–insulator phase transition observed in VO₂ films depend on the irradiation dose. If the dose exceeds a certain threshold, film metallization occurs and the phase transition vanishes. The time of retention of hydrogen within films is considerably longer than that typical for other hydrogenation methods.

Amplification of plasma waves in shielded graphene with inverted energy distribution of charge carriers is investigated theoretically. It is shown that graphene shielding allows one to increase an amplification factor of terahertz plasmons in several times compared to the case of amplification of unshielded plasmons due to strong field confinement of the shielded plasmons near graphene.

A method for the reconstruction of the architecture, strength of couplings, and parameters of elements in ensembles of coupled time-delay systems from their time series is proposed. The effectiveness of the method is demonstrated on chaotic time series of the ensemble of diffusively coupled nonidentical Ikeda equations in the presence of noise.

An energy model of the formation of multiwall nanoscrolls from thin layers is proposed. It is established that the radial growth of a nanoscroll can be accompanied by variation of the ratio of its internal and external diameters. The influence of the main physical parameters of the model on this ratio is considered.

Nonstationary velocity fields that arise during the development of flows behind shock (blast) waves initiated by pulsed surface sliding discharge in air at a pressure of (2–4) × 10⁴ Pa have been experimentally studied by the particle image velocimetry (PIV) technique. Plasma sheets (nanosecond discharges slipping over a dielectric surface) were initiated on walls of a rectangular chamber. Spatial analysis of the shape of shock-wave fronts and the distribution of flow velocities behind these waves showed that the pulsed energy deposition is homogeneous along discharge channels of a plasma sheet, while the integral visible plasma glow intensity decreases in the direction of channel propagation.

We describe a magnetosensitive device consisting of a combination of a thin-film Si transistor with built-in conducting channel (fabricated by the silicon-on-insulator technology) and a Hall-type sensor (HS). The transistor has a double-gate field control system of the metal–insulator–semiconductor–insulator–metal type and operates in the regime of carrier accumulation in the channel at partial depletion of adjacent regions of the Si film. It is established that the device can operate at temperatures up to about 350°C, which is 160–180°C higher than the maximum operating temperature of HSs based on bulk Si crystals and comparable with HSs based on wide-bandgap semiconductors.

We have developed and studied a powerful high-enthalpy (H ≥ 20 kJ/g) air plasma jet generator with a divergent channel of the output electrode, which belongs to the class of dc plasmatrons with a thermionic cathode. The plasma generator possesses an efficiency of about 80% and ensures the formation of slightly divergent (2± = 12°) plasma jet with diameter D = 50 mm and a mass-average temperature of 6000–9000 K.

We have experimentally detected a signal of magnetic resonance (MR) from ⁸⁵Rb atoms in the 5²S_1/2 state by measuring the absorption of light from a helium lamp producing optical orientation of metastable 2³S₁⁴He atoms in a cell containing alkali metal vapor and gaseous helium at a pressure of 1 Torr. The ratio of MR signal amplitudes in Rb and He atoms did not exceed 10^–2. Peculiarities of the formation and observation of the collisional polarization of Rb atoms in alkali–helium plasma are discussed.

Self-organized metal nanostructures have been obtained by an original method on the surface of soda–lime glasses. The nanostructures are grown by heat treatment of poled glass substrates in hydrogen upon preliminary ion-exchange introduction of silver. The poling is produced with the aid of a profiled anode electrode. Using the proposed method, it is possible to grow separate metal nanoislands and ordered nanostructures of several islands on the glass surface. The islands are formed in submicron-sized unpoled regions as a result of self-assembly during out-diffusion of silver. Minimum spacing in linear groups of two or three silver islands is 20–30 nm at their characteristic size of about 100 nm. The proposed method allows nanoisland arrays and groups of a few islands to be grown and multiplicated.

An experiment on search for neutron–antineutron oscillations is proposed based on the storage of ultracold neutrons (UCNs) in a material trap. The main factors influencing sensitivity of the experiment are the trap size and the amount of UCNs trapped. A high-intensity UCN source will be created at the WWR-M reactor of Petersburg Nuclear Physics Institute, which must provide an UCN density two to three orders of magnitude higher than that in the existing sources. The results of simulations of the experiment for detecting neutron–antineutron oscillations with the new source show that the sensitivity can be increased by ~20–80 times compared to existing depending on the model of neutron reflection from walls.

We have studied the temperature dependence of the mechanical strength at uniaxial compression for solid solutions based on bismuth and antimony chalcogenides, which were prepared by three methods: (i) vertical zone melting (VZM), (ii) hot extrusion, and (iii) spark plasma sintering (SPS). In the samples of solid solutions obtained by VZM and extrusion, a brittle–ductile transition was observed in a wised temperature interval of 200–350°C. In nanostructured SPS samples, transition from brittle to plastic fracture was observed within 170–200°C. The room-temperature strength of nanostructured samples was eight to nine times as large as that of VZM samples, and the stress–strain curves of these materials were significantly different. At a temperature of about 300°C, the strength of nanostructured solid solutions decreases to nearly zero.