Vol 82, No 7 (2018)

A thermodynamic analysis of deformation mechanisms is performed, based on an experimental study of dislocational substructures that form as a result of the deformation of single crystals of nickel at room temperature. It is shown that in single crystals of pure nickel, strain produces a mainly thermal effect. The most important factors responsible for the accumulation of internal energy are elastic and dislocational components.

The grain structure of M1 copper subjected to equal-channel angular pressing (ECAP) and subsequent annealing at 593K for 1 h is studied by means of transmission electron microscopy and scanning electron microscopy with the diffraction of backscattered electrons. An increase in grain size and the formation of special boundaries (Σ3 twins both coherent and incoherent) are observed, along with the migration of high-energy Σ3 twins and common grain boundaries, the splitting of Σ9 special boundaries into Σ3 twins, and the splitting of common grain boundaries into Σ9 and Σ3 special boundaries. The local transformation of common grain boundaries into special boundaries also occurs. Particles of the Cu₂O phase are present on the migrating Σ3 twins and common grain boundaries.

The mechanism of the structural and chemical state modification of columbite, tantalite and zircon surface under the effect of high-voltage nanosecond pulses is investigated using a set of precision physical and chemical methods (e.g., XPS, FTIR, SEM–EDX, potentiometric titration, electrophoretic light scattering, AFM–Kelvin force probe microscopy, and microhardness). An effective mode of preliminarily treating rare-metal minerals with high-voltage nanosecond pulses to produce directional changes in their physicochemical, electrical, mechanical, and technical properties is validated that increases mineral flotation and sorption activity and greatly improves the flotation technological characteristics of columbite and zircon.

Polarization is corrected using modified version of the electron-statistical theory of the interfacial energy at a metal–nonpolar organic liquid boundary. The dependence of the correction on the orientation and macroscopic dielectric permittivity of the liquid is established.

The size dependence of the N-variant component adsorption and interfacial tension are considered with allowance for the nanoscale effect on the volume and surface characteristics of nanoparticles and the matrix in a binary system. Numerical calculations are performed at 2200 K in a Ti–Mo system. The positive adsorption of titanium \((\Gamma _{Ti} {(N)} > 0)\) under isobaric–isothermal conditions is identified.

CeCu_3–xMn_xV₄O₁₂ (x = 0–3) with perovskite-like structure are synthesized at high pressures and temperatures. Their crystal structures are characterized by X-ray diffraction (space group Im\(\bar 3\), Z = 2). The temperature dependences of their electroresistance are studied.

The effect of the degree of doping with strontium has on the superconducting properties of granular superconductor La_2–xSr_xCuO₄ is considered. It is found that reducing the concentration of strontium under conditions of compositional disorder broadens the superconducting transition above the temperature of intergranular Josephson coupling and raises the temperature of the completion of the global superconducting transition.

Shortcomings of the zero creep compensation used in measuring surface tension σ_T of metals in the solid state are analyzed, especially its low sensitivity in measuring the temperature coefficient. A device for directly measuring σ_T with a high degree of accuracy and without the flaws of zero creep compensation is proposed.

Si/Si_1–xGe_x/Si heterostructures with large-scale (micrometer-size) lateral potential fluctuations at the upper SiGe/Si-cap heterointerface are grown. These potential fluctuations are caused by partial strain relaxation in the SiGe layer. Low-temperature photoluminescence (PL) spectra show that these fluctuations form lateral traps where photoexcited nonequilibrium charge carriers are accumulated and bind into dipolar excitons, which ultimately recombine. At temperatures below 6 K, a new narrow line with a width considerably less than that of the dipolar exciton PL line emerges in the spectra as the level of excitation increases. It is shown that this line is associated with the recombination of dipolar biexcitons in large-scale traps.

Phase transformations and aspects of alloying the phases of alloys of cementite composition, alloyed with chromium and nickel in the state immediately after mechanical synthesis and subsequent annealing, are studied. It is shown that cementite after mechanical synthesis is basically alloyed with chromium, while the amorphous phase is alloyed with chromium and nickel. Cementite produced upon the crystallization of the amorphous phase at T_ann = 300°C is enriched with nickel. At medium temperatures of annealing, the cementite regions with the highest nickel content decompose to form para- or ferromagnetic austenite.

Equivalent electrical circuits for all types of electromigration are proposed: pass-through conductivity, fast polarization processes, and relaxation polarization. The principle of the superposition of currents allows circuits to be designed with the simultaneous development of several processes of electromigration. The possibility of identifying the processes of electromigration developing in a substance from the experimental impedance spectra is discussed.

Magneto-abrasive materials, obtained via the joint mechanical activation of magnetic (metal) and abrasive (diamond, silicon carbide) components in a high-energy planetary-type ball mill, are studied by means of XRD phase analysis and optical and scanning-electron microscopy. It is shown that a metallomatrix structure forms in an Fe/diamond system after only 10 min of mechanical activation. Diamond particles are ground from 40–50 μm to 0.5–3 μm and distributed over the volume of the iron matrix. Study of the abrasive properties of Fe/silicon carbide composite applied to zirconium alloy shows that an Fe/SiC composite obtained via 10 min of mechanical activation ensures the greatest reduction in the weight of the material and the lowest level of roughness.

It is established that in impure (low concentrations of identical nonmagnetic impurities in the I-layer) M–I–M junctions (M = N, S; N is a normal metal, S is a superconductor, and I is an insulator), the matrix elements of a tunnel Hamiltonian differ radically from those in pure (without impurities in the I-layer) M–I–M junctions in the energy range of tunnel resonances associated with random quantum shortcuts in a disordered I-layer.

Magnetic properties of amorphous nanocrystalline alloy Fe–(Cu, Nb)–(Si, B) during stepwise annealing are investigated by means of X-ray diffraction analysis, vibration magnetometry, and Mössbauer spectroscopy. It is shown that an increase of the Nb content reduces the amount of the nanocrystalline component in the alloy, stabilizing the amorphous state and magnetic softness during structural relaxation.

Results are presented from studying atomic long-range order in Ni₄Mo and Ni₄W alloys via X-ray diffraction analysis. The phase transitions in these alloys are confirmed to be of the D1_a → A1 type. The temperature dependences of the long-range order parameters are found to be similar in Ni₄Mo and Ni₄W alloys. The difference between their properties is due to different characters of the order–disorder phase transition. A transition from the single-phase state with D1_a superstructure to single-phase А1 through the diphase (D1_a → A1) region occurs in the Ni₄Mo alloy. A more complex D1_a → (A1 + δ) peritectoid transformation takes place in the Ni₄W alloy. It is shown that an order parameter equal to unity can be obtained in Ni₄Mo alloy through long-term ordering annealing, while such long-range order in Ni₄W alloy (η_max = 0.9) is impossible to obtain by annealing.

X-ray means are used to investigate phase formation upon contact melting, including cases of electrotransfer, in Cd–In and Cd–Sn systems upon adding small amounts of sodium to cadmium. The nucleation of two- and three-component intermetallic compounds is established. It is shown that the microhardness of interlayers depends largely on the direction of the current in the zone of contact melting. An attempt is made to explain the obtained results.

The structural, microstructural, dielectric, and piezoelectric characteristics of ceramics of (Bi_{0.95 − x}Pb_{0.05 + x})(Fe_{0.95 − x/2}Ti_0.05Nb_x/2)O₃ ternary system solid solutions (x = 0.175–0.325, Δx = 0.025) are studied. Features of the formation of the crystal structure, granular composition, and patterns of the dielectric characteristics are analyzed within a wide range of temperatures and frequencies.

Experimental results are presented on the effective thermal conductivity of rocks (sandstone and granite) and polycrystalline arsenic chalcogenides. Measurements are made using an absolute steady-state approach in the temperature range of 273–523 K and at hydrostatic pressures of up to 400 MPa. A power-law temperature dependence of thermal conductivity with a negative exponent is specific to the investigated samples at a fixed pressure. A description of this dependence is proposed. The values used in the equation are calculated from the experimental data.

A new approach to the diagnostics of the evolution of drugs in a living organism by means of synchrotron X-ray radiation diffractometry is proposed. A drug is first localized via differential radiography, and a microbeam is then used to obtain the X-ray diffraction patterns of the corresponding area. Bismuth tripotassium dicytrate (BTD) is used as a test material. It is both introduced inside a stomach of a mouse and used in experiments with a phantom. It is shown experimentally and theoretically that an energy of 90.5 keV near the K-edge of bismuth is most effective in this approach. The possibility applying it to the diagnostics of a human body is demonstrated.

The results are presented from experimental studies of the concentration and temperature dependences of the surface tension of aqueous suspensions of bentonites. The studies are conducted using the hanging drop method on a DSA-100 tensiometer. The maximum error of measuring surface tension is 1%. A chemical analysis of samples of the studied bentonites is performed. An attempt is made to explain the nature of the minimum in the isotherms of surface tension of the suspension in terms of the spatial orientation of nanoparticles in the surface layer.

The mechanoactivation of ferroelectric materials with perovskite structure is performed. Structural changes of the ferroelectric materials after mechanoactivation based on X-ray absorption spectra (XAFS) and X-ray diffraction data (XRD) are studied. The Fourier analysis of EXAFS spectra allows quantitative estimates to be obtained for the local atomic structure of the investigated materials after activation. The effect mechanoactivation has on permittivity in a wide range of frequencies and temperatures is considered.