Russian Physics Journal最新文献

The physical optics approximation is widely used in solving the problem of light scattering on large, irregularly shaped particles due to its computational efficiency and physical clarity. However, its accuracy depends strongly on the size and shape of the particles as well as the light scattering angle. In this study, we evaluate the applicability limits of this approximation by comparing its results with those of the discrete dipole approximation, implemented in the ADDA code, across a range of particle morphologies, including hexagonal column, plate, bullet, droxtal, and arbitrary shaped ice particles. Calculations are performed at a wavelength of 0.532 µm for ice with a refractive index of 1.3116 and for particle sizes ranging from 2 to 4 µm.

Three TiO₂ thin films, TiO₂-DIP, TiO₂-SPIN, and TiO₂-AMORF, are deposited on glass substrates using the sol-gel method for a comparative study. The TiO₂-DIP film is fabricated using dip-coating and annealed at 500 °C, the TiO₂-SPIN film is prepared via spin-coating and annealed at 500 °C, while the TiO₂-AMORF film is produced by dip-coating but annealed at 300 °C. An XRD analysis reveals that both TiO₂-DIP and TiO₂-SPIN films exhibit the anatase phase, In contrast, the TiO₂-AMORF film remains amorphous, while Raman spectroscopy indicates that both TiO₂-DIP and TiO₂-SPIN are predominantly in the anatase phase, with a small percentage of brookite, while TiO₂-AMORF is confirmed to be amorphous. The SEM images show that the TiO₂-SPIN film has a highly homogeneous surface with randomly distributed grains. The AFM measurements indicate that the TiO₂-DIP film exhibits a smoother surface, TiO₂-SPIN film has a rougher surface, while the TiO₂-AMORF film demonstrates an ultra-smooth surface. The optical transmittance of the films ranges from 52 to 93% in the visible spectrum. The optical bandgaps are 3.418 eV for TiO₂-DIP, 3.684 eV for TiO₂-SPIN and 3.611 eV for TiO₂-AMORF. The m‑line spectroscopy reveals single guided modes both in transverse electric (TE) and transverse magnetic (TM) polarizations for all samples. Notably, the TiO₂-AMORF film exhibits a dip in the reflected intensity mode, attributed to its highly smooth surface (RMS = 937 pm). Among the samples, the amorphous TiO₂-AMORF film demonstrates the most favorable waveguiding properties.

In this work, several thin films of iron oxide (Fe₂O₃) doped with copper oxide (CuO) from 0% to 4% are prepared using a spray pyrolysis method. It is shown that with the increasing amount of copper oxide in the films, the optical bandgap values decrease from 2.49 to 2.23 eV. The conductivity reaches 2.64 S/cm, and the resistance is found to decrease from 1.51⋅10⁻¹ to only 3.78⋅10⁻² Ω∙cm. These results indicate that addition of CuO enhances the electrical conductivity and modifies the optical absorption behavior, making the material suitable for optoelectronic applications.

Metal oxide semiconductors (MOSs) are favored for gas sensing due to their high sensitivity, stability, and cost-effectiveness. An enhanced hydrogen detection is demonstrated by synthesizing and characterizing Nb₂O₅, SnO₂, and Eu-doped SnO₂ (Eu-SnO₂) thin films via RF-PVD to address the limitations of conventional sensors. Their structural characterization reveals an amorphous Nb₂O₅ phase and a tetragonal crystalline structure for both the SnO₂ and Eu-SnO₂ films, which exhibit equiaxed grain morphologies. A gas sensing evaluation demonstrates that Nb₂O₅ only responds at high hydrogen concentrations (10.000 ppm). In contrast, SnO₂ and Eu-SnO₂ films successfully detect low concentrations of 100 and 50 ppm, respectively. These results confirm the superior potential of SnO₂-based films, particularly with Eu doping, for efficient and highly responsive hydrogen gas sensing.

The effect of a low-power ultrasonic treatment on the microstructure of the CuAl9Mn2 aluminum-manganese bronze during its wire-feed electron beam additive manufacturing is demonstrated. It is revealed that a dendritic structure forms in the as-printed samples, based on a solid α‑solution, with the needle-like β’-phase precipitating along the grain boundaries. The ultrasound applied to the sample during printing does not significantly alter its phase composition, but reduces the lamellar spacing in the solid α solution and β’ phase. The tendency to forming the columnar grains elongated in the heat dissipation direction is minimized. However, an improvement of the mechanical properties remains relatively modest, manifested primarily by a slightly increased strength and a reduced ductility.

Incorporation of nanoscale inclusions into super-engineering polymer matrices, such as PEEK, PEI and PSU, presents a complex multiscale physical problem, when the macroscopic properties depend on interfacial phenomena. This work investigates the synthesis of aluminum oxide (Al₂O₃) nanoparticles via electric explosion of wire, affecting viscoelasticity, relaxation dynamics, and non-Newtonian flow of polymer melts. A universal protocol is developed to achieve the uniform filler distribution, which serves as a model system to polymer-nanoparticle interactions. Using a combination of rheometry in oscillatory and steady-state shear regimes complemented by structural analysis, quantitative relationships are identified between the filler concentration, network topology, and fundamental rheological response of the melts. The paper provides a physical basis for understanding and predicting processability of such nanocomposites under non-equilibrium conditions, similar to those observed in additive manufacturing.

The paper focuses on the problem of separating helium and helion systems using porous graphene sheets. It is shown that the system of two identical porous films can be successfully used to excite extremely high resonant transmission of one gas mixture component at an overall permeation blocking for the other isotope. A permeability window is selected in porous graphene with the obtained energy U(x), which is then used to calculate permeability of the double-barrier system and search for resonance during the wave transmission through this system.

The influence of ultrasonic treatment on the microstructure and properties of Ti-6Al-4V titanium alloy during its wire-feed electron-beam additive manufacturing is demonstrated. The experiments show that an application of ultrasound during printing enables a modest improvement of tensile mechanical properties of the specimens. Furthermore, in the specimen cross-section the ultrasonic treatment stabilizes the microstructure and causes the formation of more uniform columnar grains. The transverse dimensions of these columnar grains decrease from 1.3–1.5 mm in the samples printed without applying the ultrasound to 1.0–1.1 mm in those printed with an ultrasonic treatment.

This study investigates the influence of vibration-assisted microwave curing on the mechanical and moisture absorption behavior of silica-reinforced epoxy/jute/kenaf (KJJK) hybrid composites. The composites containing 1.5–8.5 wt.% nano-silica are fabricated and compared with the thermally cured laminates. The microwave–vibration process is shown to improve the resin infiltration, minimize the voids, and promote the homogeneous silica dispersion with fewer agglomerates, resulting in a significantly enhanced mechanical performance. At the optimal 6 wt.% silica content, the vibration–microwave-cured laminates achieve a tensile strength of ~106.6 MPa, a flexural strength of ~356.25 MPa, and an interlaminar shear strength of ~97.2 MPa, all higher than those of thermally cured counterparts. The impact resistance also increases, while the moisture absorption decreases from 4.4 to 3.52%, and the hardness improves from ~52.8 to ~59.5 HV. A SEM analysis confirms the improved fiber–matrix adhesion and the absence of microvoids. These findings demonstrate that the vibration-assisted microwave curing is an efficient and sustainable processing route capable of significantly enhancing the structural integrity and environmental durability of natural-fiber hybrid composites.

A Zn-SeO₂ nanocomposite solution was prepared using the two-step technique of pulsed laser ablation in liquid (PLAL): the first step was by ablation of a zinc disc, and the second step was by exposure of a selenium disc within the same ZnO solution to a laser. The properties of the resulting plasma were analyzed using optical emission spectroscopy (OES) and laser-induced breakdown spectroscopy (LIBS) to determine the electron temperature and electron density. The crystal structure was characterized using X‑ray diffraction (XRD), the surface structure was characterized using a field-effect scanning electron microscope (FE-SEM), and optical absorption measurements were used to determine the energy gap. Antibacterial activity tests against Staphylococcus aureus ATCC 25923 using the resulting particles at concentrations of 25, 50, and 100 ppm showed no obvious inhibition zones. The results indicate distinct optical and structural behavior with no antibacterial activity under the tested conditions.