Vol 64, No 6 (2019)

Several parameters (cross section, reaction rate, etc.) of various processes in laser, atomic, and chemical physics are calculated using quantum scattering theory for a system of a few particles. Results of the study of electronic and atomic collisions with diatomic molecules and collisions of diatomic molecules in excited rovibrational states are discussed. Several approximations needed for calculations of real physical systems consisting of several bodies are analyzed. Such approximations can be used for simulation of direct reactions and reactions that yield intermediate transient complexes. Calculated cross sections of electronic and atomic collisions with diatomic molecules and collisions of diatomic molecules are compared with experimental data and results of alternative calculations.

We have analyzed experimental data on supersonic self-sustained propagation of an energy-release wave in low-density mechanically activated mixtures. Various mechanisms that can be responsible for this process have been investigated, and the mechanism for detonation-like propagation of reaction in powder mixtures has been proposed. It is shown that under certain conditions, this process possesses all features of detonation and must be treated as a variety of detonation. It is demonstrated that this type of detonation basically differs from classical “ideal” detonation: instead of a shock wave, a compaction wave propagates in a powder mixture, in which powder compaction and not compression of particle material occurs due to mutual displacement of particles. In this case, a chemical reaction is initiated due to mutual friction of oxidizer and fuel particles in the powder compaction wave.

Numerical simulation data for 2D channel flow obtained by different authors have been used to study the influence of the Reynolds number on the distribution of pulsation kinetic energy over a flat channel’s cross section.

Plasmadynamic processes and rapid shock-wave processes accompanying the generation of plasma formation in a supersonic jet flow are analyzed on the basis of high-speed digital recording of images. We analyze (with a high time resolution) the dynamics of spherical plasmoid formation, discontinuities generated by it, and their action on the bow shock wave in front of the model. It is shown that during the plasmoid lifetime (about 100–120 μs), the regime of the supersonic flow past the model is modified: the shock layer is rearranged, and the departure of the bow wave from the symmetry axis substantially increases due to a change in the structure and parameters of the incoming flow.

The properties of a discharge with a self-heated hollow cathode and an evaporating anode placed in a cusp magnetic field created by two oppositely connected coils installed near the anode and cathode are studied. There is a negatively biased sample holder in the region of the annular magnetic slit. Compressing the discharge column at the anode with a magnetic field ensures effective evaporation of the metal (aluminum) loaded into the crucible anode; the density of the oxygen-containing plasma generated in the volume was controlled by changing the current of the cathode magnetic coil. The rate of depositing the aluminum oxide coating by reactive anodic evaporation, in contrast to reactive magnetron sputtering, is not limited by the oxidation of the sputtering target; the lifetime of the thermal emission cathode is hundreds of hours. The high ion-current density of the plasma (up to 10 mA/cm²) ensures a decrease in the crystallization temperature and the formation of nanocrystalline oxide coatings. The conditions are determined for a stable discharge operation with a current of up to 40 A at a pressure of 0.1 Pa in an oxygen-argon mixture. The results of probe diagnostics of the plasma discharge parameters, deposition rate measurements, and an analysis of the structure and properties of aluminum oxide coatings are given.

We have performed experimental and theoretical investigation of the anomalous form of the compression diagrams and shape memory restoration curves in Ni₄₉Fe₁₈Ga₂₇Co₆ alloy crystals deformed by uniaxial compression along the [011]_A crystallographic direction (A-austenite) in the temperature range of 200–350 K. It is found that in the investigated temperature range, all compression diagrams contain anomalous segments of smooth and sharp decrease in deforming stresses. It is shown that the segments of a smooth decrease in stress are associated with peculiarities in martensite reaction L1₂ → 14M, while segments of a sharp drop are due to instability of martensite reactions 14M → L1₀ and L1₂ → L1₀. A possible source of reaction instability is associated with interfacial stresses at the interfaces between the martensite and austenite phases (lamellas) due to different elastic moduli of contacting phases. The magnitude of these stresses is significant in the case of 14M → L1₀ and L1₂ → L1₀ transformations, which induces a sharp drop of the deforming stress, while the restoration of the shape memory effect is of a burst nature. It is established that the contribution of interfacial stresses to the free energy of martensite transformation is smaller than the dissipative (entropy) contribution to this energy; however, interfacial stresses higher than a certain threshold strongly affect transformation kinetics and, hence, determine the strongly anomalous shape of pseudoelastic deformation curves and burst restoration of the shape memory effect.

The parameters of atomic interaction pair potential for ¹³C diamond have been determined from experimental data on the ratio of Raman frequencies for isotopically different diamonds. Based on these parameters, an equation of state and baric dependences of ¹³C diamond lattice properties at 300 K have been calculated. Specifically, the Debye temperature; the first, second, and third Grüneisen parameters; elastic modulus; thermal expansion coefficient; heat capacity; surface energy; and pressure derivatives of these parameters along a 300 K isotherm have been determined. The results have been compared with available data for diamond having a natural isotopic composition, i.e., for ^12.01C.

The ionic resistance of membrane–electrode assemblies of oxygen–hydrogen fuel cell electrodes containing platinum nanoparticles on carbon black, carbon nanofibers, and proton-conducting Nafion polymer in a wide range of compositions (10–80 wt %) are studied in situ by the methods of current–voltage characteristics, electrochemical impedance spectroscopy, and simulation of the impedance hodograph. Conditions that make it possible to correctly determine the ionic resistance of the electrode on the basis of an analysis of the linear approximation of the high-frequency region of the impedance hodograph are found. It is shown that the occurrence of inhomogeneities and an anomalous increase in the ionic resistance with an increase in the content of Nafion in the electrode are associated with a decrease in the volume fraction of water-generation centers (particles of electrochemically active platinum), which leads to incomplete wetting of Nafion.

The crystalline structure of intermetallic Cu₃Sn synthesized by successively condensing thin layers of copper and tin on a substrate at 150°C has been studied. Cu₃Sn compound exists in a very narrow homogeneity range and has a long-period close-packed ordered D0₁₉ superstructure. It has been found that the crystal lattice exhibits many slip traces associated with dislocation motion. The dislocation motion is due to the stressed state of the crystal, which can be characterized as uniform extension. Electron micrographs show that slip traces in the Cu₃Sn crystal are parallel to the (\(\bar {1}\bar {1}21\)) and (\(11\bar {2}1\)) planes belonging to pyramidal slip system II, which is a main slip system along with pyramidal and basal ones. Slip traces result from the motion of partial dislocations, as indicated by the amount of slip, which is equal to half the interplanar distance. Since the crystal is ordered, slip is accomplished by a pair of superpartial dislocations and a slip trace may be a superstructural or complex stacking fault.

Influence of small additives of fullerene, graphene oxide, and their combinations in the ratio of 85 : 15 on the structure and mechanical properties of cross-linked polyurethanes under static and dynamic loads has been investigated. Nanocomposite structures have been studied by X-ray diffraction analysis and scanning electron microscopy. It is shown that the presence of carbon nanoparticles in the composite reduces its strength under both static and shock-wave loads. The synergistic effect of the mixture of carbon nanoparticles manifests itself as an increase in the elastic modulus by a factor of 1.25 in comparison with the initial polymer.

The peculiarities of resistive switching in capacitors with yttria-stabilized hafnia layers were studied. The characteristics of current transport in the initial state and after electroforming and resistive switching at different temperatures were examined. The parameters of a small-signal equivalent circuit of a capacitor were determined for switching into low- and high-resistance states. These parameters suggest that the resistance of filaments changes after each successive switching. This provides an opportunity to use such measurements to determine the nature of resistive switching and verify the reproducibility of its parameters. The contribution of electron traps to switching was revealed. Ion migration polarization was observed at temperatures above 500 K, and the activation energy of ion migration and the ion concentration were determined. The effect of resistive switching under the influence of temperature was observed and interpreted for the first time.

The composition and parameters of energy bands in thin SiO₂ films grown on the surface of a free Si/Cu film system have been studied. It has been shown that unlike SiO₂ films grown on thick films, the value of E_g for thin SiO₂ films is no higher than ~4.1 eV. This is explained by the presence of Si impurity atoms and nonstoichiometric oxides in the SiO₂ film, which arise because of the impossibility of heating the system above 700 K.

The samples of water-based magnetic fluid, which contain Fe₃O₄–SiO₂ particles with a spherical shape and sizes less than 100 nm, have been obtained. The method based on using a transmission line has been applied to measure the electromagnetic absorption coefficient in the frequency range from 0.1 to 18.0 GHz using a measuring setup based on horn antennas and the cell based on a coplanar transmission line. It has been found that magnetic fluids can be used to produce electromagnetic shields and electromagnetic wave absorbers as well as means to carry out local hyperthermia at electromagnetic radiation frequencies higher than 7 GHz.

Variations of the morphology and field-emission properties of surface-structured n- and p-type silicon wafers have been studied. The silicon surface has been structured by etching in a fluorine–carbon plasma and depositing subnanodimensional island carbon masks. It has been shown that surface structuring in a fluorine–carbon plasma makes it possible to reach desired field-emission currents in electric fields of different strengths. Physicochemical models of field emission mechanisms and models of destruction of surface-modified multipoint silicon array cathodes have been considered.

Using a statistical approach, we have estimated the size of water clusters and the number of free molecules participating in transport phenomena. The sizes of clusters and the number of molecules in them, as well as the number of free water molecules and their mean free paths, have been determined using experimental data on the temperature dependence of viscosity and density of water. It has been concluded that a temperature of 36.6°C is a special point in the range of 0–100°C. At temperatures higher than this value, the binding energy of a molecule with a cluster decreases abruptly, while the concentration of free molecules sharply increases. Quantitative data have been compared with the parameters of the superplastic state of titanium. As an example, we consider metabolism in functioning of erythrocytes of blood in an adult human.

An attempt at eliminating the nonspectral matrix effect leading to suppression of the analytic signal intensity at instrument output has been made using an Agilent-7700 mass spectrometer with inductively coupled plasma with a quadrupole analyzer for several elements in blood and urine. It is shown that acid and salt compositions, as well as organic substances in the composition of the sample itself, play a decisive role in the emergence of the nonspectral matrix effect. The role of acid, salt, and organic compositions of the entire blood matrix and urine in underrating the results of determination of several elements has been estimated. It has also been shown that the internal standard must be chosen proceeding from the closeness of its first ionization potential to the first ionization potential of the element being determined. The contributions of nonspectral matrix effects to the distortion of the results of analysis of biological liquids have been analyzed and estimated. It has been found that the dependence of the matrix effect on salts in the acidic matrix and on the operating regime of the instrument is additive.