Technical Physics最新文献

In the experiments of Mössbauer spectroscopy, transmission electron microscopy (TEM) and atomic force microscopy (AFM) the morphology and structurization of the carbon phase, the charge state of europium and the dynamic properties of europium bis-phthalocyanine pyrolysed derivatives, including the Debye temperature, were revealed. It was found that the pyrolysis of europium bis-pthalocyanine resulted in the amorphous carbon matrix and nanoscaled graphene clusters both forming turbostratic carbon phase. The europium ions in the charge state Eu³⁺/Eu²⁺ were detected. The data indicated that localization of Eu ions took place between layers of graphenes similar to graphite intercalation compounds. It was shown that an isomeric shift, linewidths and the magnitude of the resonant absorption are essential characteristics of structural transformations at the pyrolysis of rare earth bis-phthalocyanines.

Study of the mechanisms of the solid-state reactions in Sn/Fe/Cu thin films is interesting both from a fundamental point of view and from a view of the importance of emerging intermetallics in the technology of solder joints and thin-film lithium-ion batteries. By the integrated approach, including both X-ray phase analysis and local elemental analysis of the cross-sections of the films, the phase composition and the mutual arrangement of phases were studied, at various stages of the solid-state reaction occurring at different temperatures. The observed sequence of the appearing phases differs significantly from the expected one if the mass transfer took place by a volume diffusion through the forming layers.

The paper shows that upon ignition of the combined gas discharge in the resonator chamber, there appears a double layer with diode properties that consists of layers of positive and negative charges surrounding the workpiece. An increase in the level of microwave power supplied to the chamber leads to a decrease in the equivalent diode resistance in open and closed modes and an increase in the current flowing through the unit. The ions of the process gas (nitrogen or argon) ionized by the microwave field fall on the product surface and diffuse into it as a result of the thermal diffusion process, which hardens the surface layer. The product is heated when a positive bias potential is applied to it by a stream of high-energy electrons arriving at the surface and accelerated to energies of tens and hundreds eV in the discharge acceleration zone. Ion-plasma implantation leads to a significant increase in the strength, wear resistance and corrosion resistance of the surface of the processed product.

The results of the measurements of spall strength of polycarbonate at a maximum compression stress of 0.6 GPa in the initial temperature range of 20–185°C are presented. It has been found a significant decrease in the spall strength when the polycarbonate reached the glass transition temperature. The strain rates in the plastic compression wave are determined depending on the maximum stress under single and stepwise shock compression. The dependences of the shock wave velocity U_s—mass velocity up in the range of maximum shock compression stresses up to 0.8 GPa at different temperatures are constructed.

This paper presents the results of the sky survey with the TAIGA–HiSCORE installation, an array of 120 wide-angle Cherenkov light detectors spread over an area of 1 km². Data analysis is made for 2 winter seasons (2019–2021) at cosmic ray energies above 200–500 TeV. A modified method of background estimation is tested. Signal significance is estimated using classical Li-Ma method.

The change in the characteristics of a solar battery as a result of a random abrupt change in the properties of individual solar cells, which occurred as a result of a single or systematic impact of adverse factors in near-Earth outer space, is considered. The choice of the calculation scheme for constructing a model of a single solar cell is substantiated. For this situation, analytical mathematical models of typical connections of solar cells have been developed. Using the developed models, the current-voltage and volt-watt characteristics of the solar battery are analyzed in the case of an abrupt decrease in the photocurrent of solar cells with different probabilities. A statistical analysis of the characteristics of damaged solar cells was carried out using simplified logical-analytical models with the introduced circuit loss coefficient. Estimates of the values of the coefficient of circuit losses for typical schemes for connecting solar cells are given.

The activation parameters for various iron structures were calculated by the analytical method based on the paired four-parameter Mie–Lennard-Jones interatomic interaction potential. Within the framework of a single method, all the activation processes parameters were calculated: Gibbs energy, enthalpy, entropy and volume for both the process of electroneutral vacancy formation and for the process of atom self-diffusion. The isobaric temperature dependences of the indicated activation parameters for BCC and FCC iron structures from T = 10 to 1810 K along two isobars: P = 0 and 10 GPa were calculated. It is shown that at the α–γ transition temperature (1184 K), the activation parameters decrease during the isobaric transition from the BCC to the FCC structure. At the γ–δ transition temperature (1667 K), the activation parameters increase during the transition from the FCC to the BCC structure. With increasing pressure, the jumps magnitude for the Gibbs energy and the enthalpy of the activation process increases, and for the entropy and volume of the activation process decreases. It is shown that, at low temperatures, due to quantum regularities, activation parameters strongly depend on temperature, and the entropy of activation processes in this region is negative. In the high temperature region, a good agreement has been obtained with the experimental estimates of activation parameters for different iron structures known from the literature.

CuO nanoparticles obtained in a low-pressure arc discharge plasma followed by annealing in an oxygen atmosphere at 500°C were studied by X-ray diffraction and transmission electron microscopy. The formation of irregularly shaped nanoparticles in the size range of 5–30 nm was found. The Rietveld refinement confirmed the formation of a monoclinic CuO phase with an average crystallite size of ~21 nm. The temperature dependences of the magnetization and permittivity of CuO nanoparticles have been studied. They show antiferromagnetic behavior with a Neel temperature of 230 K and frequency-dependent dispersion behavior in the temperature range of 100–200 K at an external magnetic field induction of 0–1.3 T. The dielectric relaxation mechanism is analyzed and found to follow the Arrhenius behavior. It is shown that hopping conductivity with a variable hop length more accurately describes charge transport in CuO nanoparticles. A magnetodielectric response of about 2.5 was observed at a frequency of 12 kHz at a temperature of 150 K in a magnetic field of 1.3 T.

A series of data on the flux of cosmogenic ¹⁰Be in an ice core recovered from Fuji Dome Station (East Antarctica) covering the period 700–1876 was analyzed. Fourier analysis and wavelet analysis showed the presence of cyclicity in this series with a period of about 36 yr. Since flux of ¹⁰B contains information about variations in cosmic radiation entering the Earth’s atmosphere, mainly associated with changes in solar activity, the identified periodicity may be the result of the corresponding solar cycle. The possible climatic origin of the 36-year variation is also discussed.