卷 44, 编号 1 (2025)

Molten salts are used as heat-conducting media in liquid salt reactors and solar installations. Knowledge of the thermal conductivity of molten salt is necessary for the safe operation of these units. Computational methods are an alternative way to the hard-to-reach experimental way of determining thermal conductivity. In this work, the temperature dependence of the thermal conductivity of the molten salt FLiNaK, as well as this molten salt with NdF₃ dissolved in it, was calculated using the method of equilibrium molecular dynamics. The temperature trend of thermal conductivity, as well as its change after the dissolution of NdF₃ in FLiNaK, is explained based on the determination of the dynamic network of ionic bonds that exists in the molten salt model. Networks of ionic bonds were established with an upper limit of interionic distance of 0.2 nm for both types of salt melts and with a limit of 0.27 nm for the Nd–F network in a melt containing NdF₃. These networks of bonds appear in different parts of the system over time and may disappear completely. The total number of dynamic network nodes, determined during the correlation of heat flows, has an impact on the thermal conductivity value of the simulated system. A new method for interpreting the temperature behavior of the thermal conductivity of molten salt in a computer model can be used for predictive purposes when fluorides of various lanthanides and actinides are dissolved in salt melts.

It is shown that the number of spins in clusters of coherently correlated states arising under conditions of multiplequantum NMR – spectroscopy in a solid increases exponentially with time. The Smolukhovsky equation was used to study the above processes. Possible processes of cluster degradation were not taken into account. The results obtained are in good agreement with the experimental data, at least up to about 10⁵ spins in the cluster.

The kinetics of cathodic reduction of hydrogen on low-carbon steel in 2 M HCl (t = 25 °C) containing corrosion inhibitors – catamine AB and IFKhAN-92 – was studied. The main rate constants for the stages of hydrogen gas evolution and the introduction of hydrogen atoms into steel are determined. The additions of catamine AB and IFKhAN-92 inhibited the cathodic reduction of hydrogen and its permeation into steel in an HCl solution. The most effective inhibitor of hydrogen absorption is IFKhAN-92. The inhibitory effect of this compound is due to a decrease in the ratio of the hydrogen concentration in the metal phase to the degree of hydrogen filling of the surface. IFKhAN-92 reduction of hydrogen concentration in the volume of metal determines the preservation of the plastic properties of steels during corrosion in HCl solutions. The high efficiency of IFKhAN-92, as an inhibitor of cathodic reduction of hydrogen and its absorption, is the result of chemisorption of this compound on the surface of the steel and the formation of a polymolecular protective layer.

The work concerns the studying the accuracy of the quasi-static approximation for the calculation of the kinetics of singlet fission (SF) in molecular semiconductors. The SF is known to be accompanied by inverse TT-annihilation (TTA), which essentially controls the specific features of the SF-kinetics. The analysis of the SF-kinetics in the wide time region has been made, which covers both short times usually associated with the stage of geminate TTA and long times typical for the bimolecular TTA. The simple models have been proposed, analysis of which demonstrated good accuracy of formulas, derived within the quasistatic approximation, in the description of SF-kinetics. High accuracy of interpolation formulas, which combine the obtained expressions and allow for describing the kinetics at different stages of the process, is also demonstrated. The proposed formulas are shown to significantly simplify the description of the experimental results.

The paper investigates the effect of the content of the Fe + Co + Cr + Ni + Al metal binder and mechanical activation (MA) on the combustion rate, elongation of samples during synthesis, mixture yield and size of composite particles after MA, morphology and phase composition of combustion products and activated mixtures in the system (Ti + 2B) + (Ti + C) + x(Fe + Co + Cr + Ni + Al. In the process of MA mixtures, a multicomponent high–entropy alloy is formed – a solid solution based on γ-Fe with a HCC lattice (MHEA). A composite material consisting of ceramics and a high-entropy alloy was obtained by the method of self-propagating high-temperature synthesis (SHS). MA increases the maximum content of the metallic binder in the mixture, at which SHS is carried out at room temperature, from 60 to 80%. After MA, the elongation of the product samples and the combustion rate (in the case of a metal binder presence) of mixtures (Ti + 2B) + (Ti + C) + x(Fe + Co + Cr + Ni + Al) increases. For a mixture (Ti + 2B) + (Ti + C) without a binder, the combustion rate decreases after MA. With an increase in the content of the metal binder Fe + Co + Cr + Ni + Al in mixtures (Ti + 2B) + (Ti + C), the size of composite particles increases, the combustion rate, the yield of the activated mixture and the elongation of the samples of the reaction products of MA mixtures decreases. For the initial mixtures, the dependence of the elongation of the combustion product samples on the content of the binder is nonmonotonic, has a maximum.

The pulsed radiation-induced conductivity of polyethylene and polypropylene was studied at low (about 100 K) temperatures under the influence of electron pulses with an energy of 50 keV and a duration of 1 ms. To explain the results obtained, the Rose-Fowler-Vaisberg model was used. It is shown that when using it, it is necessary to take into account the difference in the shifts of carriers in a unit electric field before the first trapрing $\left({\stackrel{-}{\mu }}_0{\stackrel{-}{\tau }}_0\right)$ and those moving by recapture along traps $\left({\stackrel{}{\mu }}_0{\stackrel{}{\tau }}_0\right)$ appearing in the theoretical Rose–Fowler–Vaisberg model. Both of these parameters were calculated based on the results of experimental results.

The effect of the synthesis method of NiO–In₂O₃ composites on their structural, conductive and sensory characteristics when detecting hydrogen was studied. Impregnation of indium oxide nanoparticles with a nickel nitrate salt and a hydrothermal method with aqueous solutions of the corresponding salts were used. It has been shown that during the impregnation process, nickel oxide is formed in the form of amorphous nanoparticles on the surface of indium oxide, and during hydrothermal treatment, nickel ions are introduced into In₂O₃ structures. In impregnated composites, the particle size of indium oxide does not depend on the composition and is 60 nm, while in hydrothermal composites it decreases from 35 to 30 nm with increasing nickel content. With an increase in nickel content from 0 to 3 wt.% for both synthesis methods, the conductivity decreases, and the resistance for hydrothermal samples is an order of magnitude higher than for impregnated ones. The sensory response was almost twice as high.

The detailed microstructure of human hair in the transverse and longitudinal directions was studied using of scanning force microscopy (SPM) in the mode of intermittent probe oscillation (known as TappingMode^TM). In addition, operating in SPM-based nanoindentation local elastic properties (Young modulus, E_loc) were determined in various zones of the hair. For quantitative analysis of E_loc precise calibration of the SPM system and assessment of the tip apex geometry were carried out. To calculate the numbers of E_loc the adapted Sneddon contact mechanical model was used.