Russian Physics Journal最新文献

The Eu-doped NaCa(PO₃)₃ red-emitting phosphors are prepared by the solid-state reaction method in two heating steps. Initially, the phosphor is heated to 300 °C to remove ammonia, followed by further heating at 730 °C temperature. The X‑ray diffraction (XRD) confirms the triclinic structure and surface morphology is detected by scanning electron microscopy (SEM). The Fourier transform infrared spectroscopy (FTIR) detects the molecular vibrations and chemical bonds present within the phosphors. The photoluminescence (PL) emission occurs at wavelengths of 593 and 616 nm when excited with 396 nm light. The PL intensity reaches its maximum at a 4 mol% concentration of Eu doping, and the color purity is high at 98.9% for this concentration.

This work investigates microstructural and mechanical properties of hybrid AA7075/B₄C/ZrO₂ composites with varying ZrO₂ reinforcement using spark plasma sintering. The primary objective of the work is to optimize the reinforcement content to achieve a balance between enhanced mechanical properties and microstructural integrity. Composites are characterized by SEM, XRD, and mechanical testing to evaluate tensile strength, compressive strength, hardness, and impact strength. It is shown that 6% ZrO₂ is the best reinforcement content, with tensile and compressive strength peak at 468 and 554 MPa, respectively. Beyond this level, mechanical properties degrade due to the formation of brittle phases, including intermetallic carbides (Al₄C₃), intermetallic compounds (Al₃Zr) and increased porosity, as confirmed by the XRD analysis. Hardness values consistently increase with the higher ZrO₂ content, reaching the maximum hardness of 129 HV at 8% ZrO₂, while the impact strength decreases due to reduced ductility from the intermetallic formation and increased brittleness.

The effect of a two-phase (B2+γ/γ′)-structure on the corrosion rate is studied in single crystals of the CoNiAl and CoNiAlFe ferromagnetic shape memory alloys. It is shown that the smaller the volume fraction of the secondary γ/γ′-phases, the lower the corrosion rate. It is found out that the Co₃₅Ni₃₅Al₃₀ and Co₃₅Ni₃₅Al₂₈Fe₂ single crystals with small volume fractions of γ/γ′-phases have a lower corrosion rate, C_corr = 1.20–1.86∙10⁻³ mm/year, compared to that of the Co₄₀Ni₃₃Al₂₇ and Co₃₉Ni₃₂Al₂₇Fe₂ single crystals with a large volume fraction of the secondary phases (C_corr = 1.83–2.98∙10⁻³ mm/year). This is achieved due to a short length of the interphase B2-γ/γ′-boundary and Fe alloying. The crystals under study demonstrate pitting and intercrystalline corrosion.

A Fast Processes station is proposed for studying the detonation and shock wave processes as part of the experimental stations at the SKIF Center for Shared Use. The station includes a number of DIMEX detectors (Detector IMaging EXplosions). A DIMEX is capable of detecting synchrotron radiation (SR) from each electron bunch in the storage ring. Since the bunches can deviate from the equilibrium orbit and differ in current, a fast monitor of the SR beam position and intensity is needed to increase the accuracy of signal magnitude measurements and to measure the relative position and power of the beam radiation from each electron bunch in the storage ring. The readings from this monitor would allow correcting the measurements of the DIMEX detectors. As part of the fast SR beam position monitor, it is planned to place 4 sensors to measure the signal in the vicinity of the beam on the top, bottom, right and left. The signal ratios in the corresponding pairs of sensors are supposed to change with the beam position, and the sum of the signals from all sensors will change with the change of the total SR flux. During the experiment, the beam monitor will record the signals from all sensors synchronously with the DIMEX detector. After the experiment, the results recorded from the DIMEX detector will be adjusted in accordance with the monitor sensor signals.

A compact coplanar waveguide radiator is formed by two ground plane and a slotted central signal strip. The radiating patch is printed on FR4 substrate 1 mm thick. The circular slot on the central strip improves the bandwidth and decreases the return loss. The measured results show that it covers 4.25–7.95 GHz bandwidth with −24.80 dB return loss at a resonance frequency of 6.00 GHz. The fabricated radiator produces nominal value of co-pol at the resonance frequency. The Z-parameter of the proposed radiator is correlated with 50 Ω matching condition. The magnitude of voltage standing wave ratio at 6.00 GHz tends to unity, which implies that the reflected signal is zero and leads to a perfect matching radiator. The measured average gain and radiation efficiency are 2.44 dBi and 94.50%, respectively. The fabricated radiator covers 5.20/5.80 GHz wireless local area network (WLAN), 5.50 GHz worldwide interoperability for microwave access (WiMAX), 5.80 GHz industrial, scientific, and medical (ISM) band, 5G sub 6 GHz band, and 5 GHz wireless fidelity (WiFi) bands.

Numerical simulation of deformation in the surface layer of coated polycrystalline titanium nickelide is performed. The coating is synthesized from a layered Ti/Ni/Ti nanolaminate. The polycrystalline microstructure is studied by electron backscatter diffraction (EBSD) analysis. Based on the available experimental data, a model microstructure of the polycrystalline composite assuming the grain orientation is created. An anisotropic constitutive model of composite elastoplastic deformation is developed taking into account the cubic syngony, slip systems, and phase transition. The microstructure and model are integrated into ABAQUS/Explicit. Finite element calculations of tension and subsequent unloading of the microstructure are performed. The interrelated processes of nucleation and propagation of elastic phase transformation in titanium nickelide and elastoplastic flow in the coating layer are studied. It is found that the phase transition in the base material contributes to a more uniform distribution of strains, while the plastic flow in the coating leads to the formation of residual martensite in the titanium nickelide surface layer.

Metal matrix titanium composites reinforced with a silicide phase are produced by hot compaction and subsequent high-temperature annealing of titanium and 5 wt.% silicon powder mixtures. An X‑ray diffraction analysis and optical and scanning electron microscopy are used to study their microstructure and the elemental and phase compositions. The strength properties of the annealed samples are evaluated by measuring the microhardness. It is found out that the annealing temperature affects the microstructure, the phase composition and the microhardness of the powder compacts. An increase in the annealing temperature within the range of 800–1200 °C results in the completed silicon and titanium reaction and the formation of Ti₅Si₃ silicide, which constitute a net-like structure along the boundaries of the titanium grains. The structure evolution with the increasing temperature results in a progressive hardness increase. In order to increase the strength properties, the hardening phase distribution homogeneity and a more uniform material density, a fine titanium powder and a high hot compaction pressure are required.

The electronic structure and elastic properties of four series of titanium alloys of composition XY₃Ti₁₁, where X and Y are elements of IIIA, IVA, IVB–VIB groups, is studied by the projector augmented-wave method using the cluster-plus-glue-atom model. The smallest values of the Young’s modulus in each series are 37.30 GPa for InHf₃Ti₁₁, 36.52 GPa for SnHf₃Ti₁₁, 65.72 GPa for CrIn₃Ti₁₁, and 52.39 GPa for WSn₃Ti₁₁. The peculiarities of the electronic structure of alloys due to their chemical composition are discussed. It is shown that s, p‑elements do not affect the character of the Young’s modulus anisotropy in the alloy series: the lowest value corresponds to the < 100> direction, and the highest one—the < 111> direction, while d‑elements can change it.

The characteristic mode analysis (CMA) is a modern method for optimizing antennas and scatterers. Tracking mode algorithms are developed to correctly track the characteristic currents and fields when performing the CMA over a frequency range. Although these algorithms are widely used, they still have drawbacks in terms of speed and accuracy. This paper presents a new approach to improving the speed and accuracy of the tracking mode algorithm by combining characteristics of eigenvectors, eigenvalues, and using an adaptive frequency range. This approach focuses on breaking down frequency intervals with complex changes in the eigenvalue, thus reducing the overall tracking time while maintaining the high accuracy. To verify the method effectiveness, it is applied to various structures, from simple to complex ones, such as dipole, crossed wire, wire grid patch, and horn antennas. It is shown that the proposed method can significantly improve the speed and accuracy of the tracking mode results.

Working out of technological recommendations for modern additive manufacturing of titanium alloys is an important scientific and technical task for modern industry. The paper presents results of experimental studying the effect of heat input during wire and electron beam additive manufacturing (WEBAM) on the structural-phase composition and mechanical properties of a WEBAM-built Ti–6Al–4V alloy. Characteristic morphological and structural features of the as-built metal have been established. The as-built metal was represented by α‑Ti (HCP) and β‑Ti (BCC) lath structures. It has been shown that an increase in the heat input contributes to a higher ductility of the as-built metal with lower strength and microhardness values.