Russian Physics Journal最新文献

The paper focuses on magnetron sputtering of the pure calcium target in DC magnetron discharge. The target diameter and thickness are 50 and 3 mm, respectively. Argon and krypton are used as working gases. Continuous and medium frequency discharges are investigated along with the discharge and plasma parameters, including a current–voltage characteristic, mass-to-charge ratio of the plasma composition, ion current, and deposition rate.

This work explores compaction of fine ZrO₂ powders doped with Y₂O₃ and MgO. ZrO₂(Me_xO_y) powders are obtained by plasma chemical synthesis and chemical precipitation from salt solutions. Powder compaction is studied during the nonisothermal sintering process. It is shown that the ZrO₂(Y₂O₃) powder synthesized by chemical precipitation demonstrates the lowest degree of compaction during sintering. With the same synthesis method and similar size distribution of ZrO₂(Me_xO_y) powders, the difference in the compaction kinetics is determined by the different number of oxygen vacancies. The higher number of oxygen vacancies in the ZrO₂(MgO) powder obtained by plasma chemical synthesis, provides the highest compaction rate compared to the ZrO₂(Y₂O₃) powder. According to mercury porosimetry, ZrO₂(Y₂O₃) powders of the same composition obtained by plasma chemical synthesis and chemical precipitation, have very different porosity. The highest compaction rate for all compacts is observed at the heating stage. After sintering, ZrO₂(Y₂O₃) ceramic samples show similar values of compaction rate. Research findings may be useful to specialists involved in the development and synthesis of fine ceramic powders.

Prospects for the application of orbital lidars for the detection of gas leaks from spacecrafts are investigated. The optical characteristics of the main light-scattering components – molecules and atoms of gases, are estimated at altitudes of 100–600 km from the Earth surface. It is shown that an orbital lidar with modern technical parameters can reliably detect signals from dispersed gas leak components at distances from several tens to one hundred meters from the spacecraft.

This work is devoted to the study of a negative corona discharge in air at atmospheric pressure. To ignite it, the edge (cathode) –plane (anode) system has been used with interelectrode gap of 10–20 mm long and edge curvature radius of ≈20 μm. For the first time, it has been established that in a certain voltage range, the Trichel pulse mode after ignition becomes unstable and is periodically replaced by the glow discharge mode with a current ≲ 1 μA. It is shown that at the stage preceding the first Trichel pulse, the discharge current is not recorded within measurement error of ±0.2 nA.

The paper analyzes a three-layer waveguide made of chiral metamaterials separated by the graphene interface. The interface consists of three graphene monolayers with a thickness 0.34 nm, so the interface thickness is 1.02 nm. Mathematical formulas are derived for dispersion relations and power flux of guided waves for hybrid odd and even modes at right and left circular polarizations. Power profiles in the waveguide regions are potted and discussed. The work aims to investigate changes that occur due to the graphene presence as an interface in the chiral slab waveguide. It is shown that graphene properties affect the light propagation, which, in turn, provides a disappearance of the fundamental odd mode. The power flux through the waveguide shows a significant effect due to the presence of graphene and chirality.

The results of 3D modeling of the distribution and accumulation of dislocations and low-angle boundaries in the volume of a layered metal-intermetallic composite under uniaxial compression are obtained. The calculations are performed using a synthesis model of dislocation kinetics and mechanics of a deformable solid. The model is preliminarily tested on a single-phase intermetallic compound and pure metal, which shows a good agreement between the calculated values and the earlier obtained experimental results. The patterns of stress distribution, plastic deformation intensity, dislocation density, and low-angle boundaries density in the plane of the central longitudinal section of a deformed rectangular sample of a layered metal-intermetallic composite are presented. The inhomogeneities of internal stresses and strength properties of the selected-configuration layered metal-intermetallic composite under compression are evaluated.

Synthesis and characterization of a Dy³⁺-activated calcium yttrium oxide (CaY₂O₄) phosphor are reported. The CaY₂O₄:Dy³⁺ (1.5 mol%) phosphor is synthesized using a modified solid-state reaction technique for calcination and sintering. The cubic structure is revealed by the X-ray diffraction technique. The morphology and particle size distribution of the prepared phosphor are investigated by the FEGSEM technique. The chemical bonds and functional group analysis are confirmed by the FTIR. A photoluminescence analysis of the CaY₂O₄:Dy³⁺ phosphor shows dual excitation wavelengths at 285 and 348 nm, especially in the ultraviolet region. At 383 nm, three distinct emission peaks are found at the wavelengths 238, 485, and 571 nm. The spectroscopic parameters are calculated using the CIE chromaticity coordinates. The CIE coordinates of the Dysprosium ion-activated CaY₂O₄ phosphor (1.5 mol%) show an emission near the white light region of the chromaticity diagram, suggesting that it is suitable for W-LED applications.

In this paper, the effect of ultrasound on the microhardness and microstructure of friction stir welding joints is investigated. It has been found that the area with minimum microhardness is located in the thermomechanically affected zone on the retreating side. An ultrasonic impact resulted in an increase in the size of this area. The weakening of the region is attributed primarily to the low content of hardening particles due to overaging. It was also found that the ultrasonic impact during welding resulted in a 5 times reduction of residual stresses.

The physical and chemical characteristics of hydrophobic protection of cement rock and concrete surfaces, using the binders based on polyurethane, elemental sulfur, and nanodimensional fillers of Tarkosil and thermally modified peat, are discussed. It is shown that a combined use of the physical texture-formation methods and an optimal selection of the protective coating chemical composition results in a significant increase of the wetting angle and the solid phase surface energy. It is found out that a directional orientation of the magnetically sensitive particles in the magnetorheological composites in a magnetic field is among the most effective methods for improving the protective coating properties.

Orbital evolution of model near-Earth space (NES) objects moving in orbits with semi-major axes in the range from 8 000 to 100 000 km is analyzed to reveal the dynamic structure features of this NES region to choose a disposal strategy for spent spacecrafts or deployment of new satellite systems. The areas possessing the greatest stability and keeping preset orbital elements and hence the most suitable for placing new satellites and disposal of spent satellites are shown. The areas in which the deployment of satellites is inexpedient are highlighted.