Russian Physics Journal最新文献

The paper presents results of finite element modeling, development of and experiments with the measuring cell based on a symmetric stripline for measuring coarse-grained soil permittivity. The wave impedance of the measuring cell section intended for filling with soil, is about 80 Ω to expand the frequency range. This allows reducing the width of the central strip and increasing the critical frequency, which cause the higher-order modes. Cell sections with the transfer from SMA connectors to measuring section are filled with a solid dielectric. The distance between outer conductors and the central strip width in these sections, are linearly increased to the size of the measuring section to provide the wave impedance of 50 Ω. The wave impedance growth in the measuring section is considered in the soil complex permittivity calculations. The complex permittivity is measured for five calibration liquids with the static permittivity of 2.27 (transformer oil) to 78.5 (water) and three soil samples with different moisture. It is shown that acceptable values of measurement error can be obtained if the real part of the complex permittivity does not exceed 23–25 units at a frequency of ~1 GHz.

The generalized Pöschl–Teller potential is well-known and is widely applied in molecular physics, chemistry, and nonlinear physics. In the past, when the vintage Greene–Aldrich approximation scheme for the centrifugal potential of the generalized Pöschl–Teller potential was examined, the consensus was that it would break down or become unreliable for large values of the potential parameter α. However, this study challenges that perspective by reviewing the problem in a new light and proposing a new and improved Greene–Aldrich approximation that mitigates the breakdown effect. Additionally, it is demonstrated that the energy eigenvalues produced for short and long-range potentials are in considerably closer agreement with those obtained using the numerical integration method than with the results of earlier research.

The effect of substitutional impurities on the formation energy of nitrogen vacancies and the oxygen defect on the N-sublattice as well as on the oxygen migration energy in TiN is studied using the projector augmented wave method. It has been shown that 4d transition metals with the exception of Zr and elements of IIIA and IVA groups excluding Al and Si reduce the formation energy of nitrogen vacancies. At the same time, regardless of the impurity, the formation energy of the oxygen defect has a negative value. The oxygen migration energy within the first coordination sphere is increased by almost all impurities, while metals of the middle of the 4dperiod slightly lower the migration barrier of oxygen, which allows it to move away from the impurity atom. The lower and upper limits of the temperature-dependent diffusion coefficient of oxygen in the doped titanium nitride are estimated. It has been revealed that almost all considered impurities reduce the diffusion coefficient mainly due to a change in the migration energy.

The influence of annealing at a temperature of 980°C on the microstructure, phase composition, and microhardness of the additively manufactured TiNi-based material has been investigated. TiNi billets were produced using dual-wire electron beam additive manufacturing by simultaneous deposition of titanium and nickel wires. The typical morphology of dendritic microstructure changes from the bottom to the top of the asbuilt billet and is characterized by large dendritic blocks in the bottom part and thin dendrites in the central and upper parts. According to the data of scanning electron microscopy energy-dispersive X-ray (SEM EDS) analysis and the phase diagrams, dendrites and interdendritic regions consist of a mixture of TiNi + TiNi₃ and TiNi + Ti₂Ni phases, respectively, but the data of X-ray analysis confirm the presence of the Ti₃Ni₄ phase as well. Annealing contributes to the partial dissolution of large dendrites in the bottom part of the billet, increase of the thin dendrite sizes, and smoothing of their forms. The data of SEM EDS analysis and XRD both testify that the multiphase mixture of different phases tends to transform into a single-phase TiNi structure during annealing, but this transformation is incomplete. All these factors lead to the increase of microhardness of the annealed samples from ≈5 GPa for the as-built specimen to ≈7 GPa for the 8-h annealed specimen.

The structural-phase sates and defect substructure are studied by the method of transmission electron microscopy using diffraction at different distances from the wheel–rail contact surface along the central axis of symmetry of the top of rail (TOR) (rolling surface) and along the radius of rounding (fluting) of the differentially hardened rails of the DH400RK category made of hypereutectoid steel after their continuous service. Using the obtained structure parameters, the estimates are made of the hardening mechanisms (strengthening by pearlite component, incoherent cementite particles, grain- and subgrain boundaries, dislocation substructure and internal stress fields) controlling the yield stress in the steel under study. A comparison is performed of the quantitative fine structure parameters and the contributions into hardening on the rolling surface and fluting. It is found out that the prevailing morphological component near the wheel– rail contact surface is the subgrain structure, and in the fluting – strengthening by incoherent particles.

The paper presents the synthesis of the aluminum–zirconia titanate composite powder using a high-power fastelectron beam. It is shown that the electron-beam processing of the mixture of initial oxide powders leads to the formation of composite ceramics with a complex phase composition. It is found that the porosity of the powder mixture depends on the electron beam parameters, scanning, and beam-induced displacement rate of the cuvette. When selecting these parameters, it is possible to synthesize low-porosity ceramics, which shows the tendency of combining synthesis and sintering during the electron-beam processing.

In order to promote the research on vacuum-arc coating deposition using vaporable TiBSiNi SHS-cathodes, a design of a Zr+Zr_xN_y+(Zr+TiBSiNi)N+(TiBSiNi)N gradient-layered hardening coating is proposed. Its constituent layers are selected relying on the results of a comparative study of their physical, mechanical and tribotechnical properties. The coating architecture is based on the tribological theory and the analysis of basic requirements to protective-hardening coatings. A comparison of the coating parameters with those of its layers demonstrates that most of them exceed the latter. In particular, its hardness is found to be 40.2 ± 2.0 GPa against that of a ZrN coating equal to 31.5 ± 2.3 GPa and is at the level of the hardest (TiBSiNi)N coating layer (41.9 ± 3.6 GPa). The adhesion (strength of cohesion to substrate) of the gradient-layered coating exceeds those of its constituent layers – ZrN, (TiBSiNi)N, and (Zr+TiBSiNi)N. An annealing treatment of this coating at 700°C in air for 60 min demonstrates its high thermal stability. The proposed gradient-layered coating exhibits a higher hardness (14.8 GPa) compared to the other coating types (5.8–9.1 GPa) after annealing, which, according to the XRD analysis, can be attributed to the availability of zirconium nitrides and harder titanium nitrides in its composition. The principal criteria of the designed gradient-layered coating are its tribo-engineering tests demonstrating both a lower friction coefficient and a higher wear resistance over those of the other coatings. Its wear parameter is found to be 5.4∙10^–6 mm³N^–1m^–1 in coupling with a 100Cr6 steel counterbody compared to that of a conventional ZrN zirconium nitride coating – 43.0∙10^–6 mm³N^–1m^–1. There are also some advantages of the gradient-layered coating revealed in its wear resistance in comparison with the constituent multi-component layers – both with a 100Cr6 steel counterbody and in a tribo-couple with a superhard silicon carbide, SiC.

Using the methods of scanning and transmission electron microscopy, the structural-phase states in the transition zone of a layer of fast-cutting S-2-9-2 steel (European standard) surfaced on 14331 medium-carbon steel (CSN standard) is investigated after tempering and electron-beam treatment. As a result of surfacing, a carbide network structure is formed, while there is no network in the transition zone. A plate-like martensitic structure is observed to form in the transition zone. The carbide phase particles measuring up to tens of nanometers demonstrate different morphology in the transition zone. They localize along the grain boundaries of martensitic crystals and austenitic interlayers and on dislocations in the bulk of the martensitic plates.

Using the results on the structural changes of cured carbon-, glass-, and organic plastics subjected a microvave electromagnetic field, by the method of low-coherence reflexometry, it is found out that the radiation intensity absorbed by the material decreases on average by 15%, 9,4% and 8,4%, respectively, which is indicated by the increased material structure density. It is argued that the influence of the microwave treatment on the filler-free binder is insignificant. The results obtianed objectively indicate a decrease in the number of defects (cracks, delaminations, pores, etc.) and a respective increase of the structure density of cured polymer composite materials processed with microwave electromagneticfield radiation.

Using scanning tunneling microscopy, it is shown that a lath structure is formed in the heat-affected zone of the low-carbon, low-alloy 09G2S steel after electric arc surfacing. Analysis of the results of scanning tunneling microscopy revealed a number of subtle morphological features of the lath structure, which makes it possible to explain the mechanism of its formation and identify it as lower bainite. The lower bainite structure in the heat-affected zone of the base metal of the 09G2S steel is favourable for increasing the impact strength of the coating – base metal composition, which was established earlier in our work.