Russian Physics Journal最新文献

The effect of alloying the Ni_49.5Ti_35.5Hf₁₅ polycrystals with up to 15 at. % Nb on the stress-induced martensitic transformations, shape memory effect, and superelasticity of this alloy is studied. The initial Ni_49.5Ti_35.5Hf₁₅ polycrystals exhibit no shape memory effect due to a high volume fraction of (Ti, Hf)₂Ni particles, suppressing the stress-induced martensitic transformations. First, an addition of Nb results in the homogeneous distribution of Ni, Ti, and Hf, the formation of local β‑Nb phase regions, and the suppression of the (Ti, Hf)₂Ni particle precipitation. Second, the (Ni_49.5Ti_35.5Hf₁₅)₈₅Nb₁₅ alloy exhibits high-temperature shape memory and superelasticity effects, with a maximum transformation strain of 1.0% and a reversible strain of 0.3%–0.4% in compression. Third, despite their high strength, the Ni_49.5Ti_35.5Hf₁₅ polycrystals suffer brittle fracture near the yield stress during deformation in the austenitic state, while an addition of Nb increases the material plasticity up to 14.5%–18%. Moreover, a high resistance to the oriented martensite formation in the (Ni_49.5Ti_35.5Hf₁₅)₈₅Nb₁₅ polycrystals results in a mismatch between the curves of the σ(T) dependence derived from the experimental ε(T)_σ and σ(ε)_T curves.

The paper studies heat-transfer properties and structural bonds of cured polymer composites modified by the microwave electromagnetic field. Raman spectroscopy shows the dependence of carbon fiber and fiber glass spectral intensity on the microwave radiation and the significant difference of these spectra from those of reference samples at certain microwave radiation parameters. In general, Raman spectroscopy of reference and test carbon fiber and fiber glass samples demonstrates the growth in the spectral line intensity for the main functional groups of the cured epoxy matrix and the formation of additional bonds due to the heat and wave processes accompanying the microwave effect that can improve the strength of polymer composites due to the better matrix-filler interaction as well as a cohesive interaction in the matrix.

The electronic structure of fullerene C₆₀, both in its neutral and ionized state, is investigated taking into account the strong intrasite Coulomb interaction. The energy spectrum of the C₆₀ and C₆₀⁺ systems is calculated in the static fluctuation approximation for the Hubbard model. The optical absorption spectrum is constructed relying on the calculated energy spectrum using the Kubo formula. The optical absorption spectrum curves of C₆₀ coincide with the experimental curves on the good qualitative level. However, the optical absorption spectrum of C₆₀⁺ does not coincide with the experimental data. The reasons for this discrepancy and the effects that lead to it are discussed.

The microstructure and mechanical properties of the 13Mn6, SS321, and 56GM steel specimens produced by the wire-feed electron beam additive manufacturing (EBAM) are examined. The printing parameters are shown to strongly affect their geometric accuracy. The heat input plays a key role in the formation of structure characteristics. The macrostructure of all steel specimens is characterized by the presence of distinct melt-pool boundaries, inherited during repeated melting of previously deposited layers and thermal cycling. The formation of this macrostructure is attributed to the alloying element segregation under the conditions of non-stationary metallurgy in the course of the electron beam additive process. During the deposition of subsequent layers, the microsegregation expands in the material flow direction, causing the macrostructure to acquire a characteristic layered character. The microstructure of the additively-grown SS321-based specimen is characterized by a dendritic pattern, whereas the 13Mn6 and 56GM-based specimens exhibit a grain structure. The average yield and tensile strengths for the 13Mn6-based specimens are 262 and 431 MPa, for the SS321-based specimens—328 and 696 MPa, and for the 56GM-based specimens—511 and 934 MPa, respectively, which are comparable to those of the steels produced by conventional methods.

The paper presents a solution procedure for the wave transmission through a two-barrier system. Each barrier in this system consists of a graphene plate with a specified areal atomic density. It is shown that it is always possible to select an inter-barrier distance, at which the resonant transmission occurs, while simultaneously exhibiting resonance with an exceptionally broad separation of components.

In this study, thin films of (CuO:Zn)_1−xFe_x are prepared using a pulsed laser deposition (PLD) technique. The Nd:YAG pulsed laser operated at a fundamental wavelength of 1064 nm and a frequency of 6 Hz is used. The effect of adding iron at different ratios from 0.1 to 0.5 on the structural and optical properties of the prepared films is studied. The results of X‑ray diffraction (XRD) show that the crystal structure remains stable despite the addition of iron. However, there are the crystal angle shifts and lattice distortions, indicating that the addition of iron has affected the lattice and changed the crystal dimensions. On the other hand, the optical properties of the prepared films show a significant improvement upon the addition of iron, as a gradual decrease in the energy gap from 2.8 to 2.4 eV is observed, in addition to a significant increase in the absorption and extinction coefficients, refractive index, and real and imaginary electrical permittivity. These results indicate a potential use of the doped films in many optical applications, such as solar cells and optical filters and sensors.

The paper focuses on nanocomposites fabricated from polydimethylsiloxane with the multi-walled carbon nanotube content of 1, 5, and 8 wt.%, cured at room and elevated temperatures. The sample structure is investigated by scanning electron microscopy, mechanical testing (Young’s modulus), differential scanning calorimetry, small- and wide-angle X‑ray diffraction method, electrical resistance measurements. Hot-cured composite in the content of 5 wt.%, demonstrates the best balance between the mechanical properties and conductivity for soft neuroprosthetic devices.

This study reports the synthesis of cadmium-doped tin oxide (SnO:Cd) nanoparticles using pulsed laser ablation in liquid (PLAL) at laser energies of 500, 700, and 900 mJ. The influence of laser energy on the structural, morphological, and optical properties of the nanomaterials has been systematically investigated. X‑ray diffraction (XRD) results for the prepared samples show the formation of crystalline structures with a clear increase in crystallite size with increasing laser power. On the other hand, atomic force microscopy (AFM) reveals an increase in the surface roughness resulting from particle agglomeration. Field emission scanning electron microscopy (FESEM) supports this result using its high-resolution imaging to visually show that nanoparticles have different sizes. UV-Vis examination reveals a redshift in the absorption behavior with a decrease in the band gap from 2.9 to 2.2 eV. These results demonstrate that the laser power is a critical parameter in controlling the properties of the resulting SnO:Cd nanoparticles, which impacts their suitability for microelectronics, optics, and sensor applications.

The paper studies two types of thermal control coatings for space vehicles that are based on ZnO pigment and KО-921 silicone varnish and deposited by conventional and additive manufacturing techniques. It is found that the deposition technique can significantly affect the performance of thermal control coatings, in particular optical properties and radiation resistance. In additive manufacturing, the solar absorption factor (a_s = 0.136) is lower than in brushing (a_s = 0.148). As for optical properties, they are more stable for the brushed than for the printed coating.

A comprehensive theoretical investigation into the dynamic transport properties of electrons in the indium arsenide (InAs) spherical layer quantum dots (SLQDs) is presented. The focus is on how these properties are influenced by structural geometry, temperature, and externally applied pressure. Utilizing a quantum mechanical framework based on the effective mass approximation, a systematic analysis is made of the variations in quantized energy levels, electron relaxation time, mobility, electrical conductivity, and drift velocity with respect to the inner and outer SLQD structure radii. The results demonstrate that increasing the inner radius (or reducing the outer radius) leads to stronger quantum confinement, which significantly enhances all investigated transport properties. Furthermore, elevated temperatures result in improved electron dynamics, while applied hydrostatic pressure has a detrimental effect by suppressing the energy level spacing and reducing the carrier mobility. These findings provide fundamental insights into how thermomechanical parameters and quantum dot geometry can be effectively tuned to optimize the electron transport in low-dimensional semiconductor systems for advanced optoelectronic and nanoscale device applications.