Vol 62, No 5 (2017)

State equation P(V/V₀, T) and baric dependences of thermal properties of diamond have been obtained without any fitting parameters from the interatomic pair Mie–Lennard-Jones potential and the Einstein model of a crystal. Calculations have been performed along two isotherms (at T = 300 and 3000 K) up to P = 10000 kbar = 1000 GPa, i.e., to a relative volume of V/V₀ = 0.5. The baric dependences have been obtained for the following characteristics: isothermal elastic modulus B_T and B'(P), isochoric heat capacity C_v and C_v' (P), isobaric heat capacity C_p; thermal expansion coefficient α_p and α_p' (P); and specific surface energy σ, as well as its derivatives σ'(P) and σ'(T). It is shown that for P → ∞, functions B_T(P) and σ(P) vary linearly, functions B'(P), α_p(P), C_v(P), C_p(P) and σ'(P) tend to constants, while functions α_p'(P), C_v'(P), and difference C_p(P)–C_v(P) tend to zero. Good agreement with experimental data has been demonstrated.

Perfect gas mixtures that result from thermal ionization of spatially and chemically homogeneous monoatomic gases are considered. Equilibrium concentrations of the components of such mixtures are determined using integration over the momentum space and summation with respect to energy levels of the distribution functions that maximize the entropy of system under condition for constancy of the total number of nuclei and electrons. It is demonstrated that such a method allows significant simplification of the calculation of the equilibrium composition for ionized mixtures at different temperatures and makes it possible to study the degree of ionization of gas versus gas density and number in the periodic table of elements.

The problem of the gravitational filtration of a liquid in suspension is considered taking into account the formation of deposition by sedimentary disperse particles. The behavior of the suspension has been described using the system of equations of 1D inertia-free motion of a two-phase mixture, while the flow of the liquid through the porous sediment layer has been described by the filtration equation based on the Darcy law. The dynamics of sediment formation has been analyzed. Limiting cases of equidense and equilibrium suspensions have been studied separately. The expressions for integrated characteristics of the filtration of a disperse mixture in the gravity field have been derived, and the intensities of filtration in different regimes have been compared. The effect of key parameters on the dynamics of filtering a liquid from a suspension has been investigated.

We have studied the mass and charge composition of an ion beam extracted from the plasma of a vacuum arc with a zirconium deuteride cathode for various durations of the arc current pulse (half width at half amplitude) of 2, 4, 7, and 17 μs. It has been established that the fraction of deuterium ions in the vacuum arc plasma increases with the current and the dependence achieve saturation for current of about 1 kA. For the fraction of deuterium atoms in the cathode at a level of 40%, the fraction of deuterium ions in the vacuum arc plasma can exceed 80%. The experimental results have been interpreted theoretically. It has been shown that the main sources of deuterium ions in a microsecond arc discharge are cathode spots. We have developed a model of deuterium desorption during the operation of cathode spots for quantitatively estimating the concentration of deuterium ions in the arc plasma.

Experiments on initiating electrical air discharge in an airtight radiotransparent volume have been described. The discharge is initiated by a quasi-optical linearly polarized microwave beam with a deeply subcritical field by means of an electromagnetic vibrator mounted above a screen. The results make it possible to calculate the effective area of energy interaction between the plasma of the discharge and its initiating microwave field. It has been shown that this area considerably exceeds the cross-sectional area of the discharge.

An equation of state for graphite and diamond has been derived in wide density and temperature ranges. A set of equations for the graphite–diamond phase transition has been presented. Hugoniots for graphite and diamond have been calculated. Numerical simulation data for the graphite–diamond transition in the isentropic compression process using a metallic z-pinch with diamond saving have been reported.

The effect of high-temperature thermomechanical treatment with deformation in the austenite region on the microstructure and mechanical properties in low-activated 12% chromium ferritic-martensitic steel EK-181 (Fe–12Cr–2W–V–Ta–B) has been investigated. This treatment leads to a significant increase (compared to traditional regime of treatment) in the density of dislocations, dispersity, and volume fraction of nanosized particles V(C,N) and, as a consequence, to an increase in the yield strength while maintaining a sufficient reserve of ductility.

Results have been presented for a computer experiment on concurrent micro-, meso-, and macroscopic studies of the evolution of dislocation structure in a large (adjacent to one of the junctions) domain of a grain after its constant-rate macroplastic deformation to an extent that corresponds to the onset of the stage of developed plastic deformation. The type of dislocation-density and dislocation-charge distributions, as well as amounts and degrees of inhomogeneity in local plastic deformation, have been analyzed. The type of dislocation rearrangements at the junctions and fractures of high-angle grain boundaries has been established, which is responsible for the formation of the first dangling dislocation boundaries, which are mesodefects that trigger fragmentation.

The processes involved in the planarization of the surface of nanoporous SiO₂ by the atomicmolecular deposition of nanoscale TiO₂ films were studied in regimes with different degrees of penetration of TiO₂ into SiO₂ nanopores. The technological process parameters that correspond to different regimes of surface planarization were examined. The degree of penetration of TiO₂ into SiO₂ nanopores was monitored using reflection ellipsometry by measuring the depth distribution of the refraction index within the two-layer model.

The detection properties of a field-effect transistor with a low Schottky barrier gate in the microwave and terahertz ranges has been studied theoretically. Different detector circuits have been considered. The voltage and current distributions along the channel, the input impedance of the transistor, sensitivity, and noise equivalent power have been found. The influence of the Schottky barrier height on the above characteristics has been analyzed.

Layered ZnS/SiO₂, ZnS/Al₂O₃, and ZnSe/SiO₂ nanocomposites have been studied. It has been shown that the use of the Maxwell–Garnett and Bruggeman models, as well as the Luyengi formula, in the low dispersion region makes it possible to predict the production of films with a given effective refractive index. Calculated values of the refractive index correlate well with experimental data. The maximal discrepancy between the theoretical and experimental values of the refractive index and the maximal value of the depolarization factor depend on the structure and microstrains.

Propagation of electromagnetic waves in graphene-like conducting carbon crystals with the (C)_4ν and (C)_6ν symmetries is studied. It is demonstrated that only TM waves can exist in such crystals. The comparative analysis of such waves in different structures is performed. It is shown that the structures under study are superior to classical graphene with respect to excitation of electromagnetic waves.

The results of simulations of a multipole electron-optical system has been considered. The electrodes of the system consist of an even number of identical parts of one circular cylinder that is cut parallel to the generatrix with infinite length. To determine the potential distribution, the Laplace equation has been solved by the method of variable separation in the polar coordinates. All of the geometrical dimensions of the system and the number of electrodes are parameters of the problem.

Effect of deposition conditions in reactive nitrogen atmosphere on the growth morphology, phase composition, structure, and mechanical characteristics (microhardness) of vacuum-arc multilayer coatings obtained using evaporation of the (Ti6%Si) and Mo cathodes is studied with the aid of raster electron microscopy, energy-dispersive elemental microanalysis, and microindentation. It is demonstrated that nitrogen atoms are redistributed to the region of the strongest nitride-forming element (Ti) in relatively thin layers (about 7 nm) consisting of substances with substantially different heats of formation (−336 kJ/mol for TiN and −34 kJ/mol for MoN). Such a process leads to lamination with the formation of nitride TiN and metal Mo (weaker nitride-forming element). Nitrogen–metal bonds are saturated in the layers of strong nitrideforming elements Ti(Si) when the nitrogen pressure increases from 6 × 10^–4 to 5 × 10^–3 Torr in the condensation procedure. Thus, the compound is filled with nitrogen to the stoichiometric composition and, then, the second system of layers based on molybdenum is saturated with nitrogen with the formation of the γ-Mo₂N phase. An increase in bias potential U_SP from–100 to–200 V stimulates mixing in thin layers with the formation of the (Ti, Si, Mo)N solid solution and leads to a decrease in microhardness from 37 to 32 GPa.

We have proposed a mathematical model of the sensor response of vacuummeters with sensitive elements based on broadband semiconductor oxide with electrical conductivity of the n- and p-type, as well as the multicomponent oxide systems. The correctness of the model description of the dependence of the resistivity of nanomaterials synthesized by the sol–gel method and has the structure of spherical aggregates of fractal origin on the ambient pressure has been demonstrated. It has been shown that, taking into account the corrections, the developed model can be used to qualitatively describe the sensor response of nanomaterials based on two-component SiO₂—SnO₂ oxide systems with a labyrinth structure.

We consider the possibility of increasing the spatiotemporal length of an ion packet and reducing the fraction of multicharged ions in the mass spectrometer beam, which are formed under the action of laser radiation on the experimental sample by using a magnetic trap as part of a laser-plasma source.

The ultrafast (subnanosecond) switching of a high-voltage silicon avalanche shaper (SAS) diode from a blocking to conducting state is performed by applying an overvoltage pulse with a wavefront rise-rate of ~10¹² V/s in the reverse direction. The forming under this condition impact ionization front fills in the diode base layer with electron-hole plasma and switches the diode to the conducting state. Besides, it is important to prevent the possible breakdown over the diode structure surface while the overvoltage pulse is applied. The first results of the investigation of principally new SAS diode design is presented. New diode construction completely excludes edge contour degradation by the overvoltage pulse. Our experiments show the usefulness of the suggested diode construction and the importance of further investigations to determine its operation limits.