Том 60, № 10 (2018)

Three gold nanoparticle suspensions are obtained, and mean radii in distributions – (6.1 ± 0.2), (11.9 ± 0.3), and (17.3 ± 0.7) nm – are determined by the transmission electron microscopy method. The optical absorption spectra of suspensions are obtained and studied. Calculation of spectral dependences of the absorption index of suspensions at values of the gold complex refractive index taken from the literature showed a significant deviation of experimental and calculated data in the region of 450–800 nm. Spectral dependences of the absorption of suspensions are simulated within the framework of the Mie–Drude theory taking into account the interband absorption in the form of an additional term in the imaginary part of the dielectric permittivity of the Gaussian type. It is shown that to quantify the spectral dependences in the region of the plasmon absorption band of nanoparticles, correction of the parameters of the interband absorption is necessary in addition to the increase of the relaxation parameter of the Drude theory. Spectral dependences of the dielectric permittivity of gold in nanodimensional state are refined from the solution of the inverse problem. The results of the present work are important for predicting the special features of operation of photonic devices and optical detonators based on gold nanoparticles.

The effect of submicron ferroelectric BaTiO₃ particles on the dielectric and electro-optical properties of the smectic-A liquid crystal (LC) with a high negative dielectric anisotropy is investigated. It is shown that the addition of BaTiO₃ particles with a weight amount of 1% reduces insignificantly the transverse dielectric permittivity component ε_⊥ of, but significantly increases the longitudinal dielectric permittivity component ε_// of the smectic-A LC. As a result, the anisotropy of the dielectric permittivity Δε = ε_// − ε_⊥ of the smectic-A LC decreases. The addition of BaTiO₃ particles shifts the dispersion ε_⊥ toward lower frequencies. Both components of the electrical conductivity of LC colloid + BaTiO₃ are an order of magnitude higher than of the pure LC. The threshold voltage of the homeotropic-planar transition of the colloid is twice smaller, and its velocity is 6 times higher in comparison with the pure LC. A simple model explaining qualitatively all results obtained is presented.

Inkjet ink based on silver nanoparticles with sizes of 11.1 ± 2.4 nm has been developed. Test images are printed on a laboratory inkjet printer, followed by sintering the printed patterns with a diode laser having a wavelength of 453 nm. The structure and electrical properties of the resulting films are studied depending on the parameters of laser sintering. It is found that under optimal conditions, an electrically conductive film with a low resistivity of 12.2 μΩ· cm can be formed.

A method of analytical description of one of the most complex problems in the study of high symmetry quantum-mechanical objects, namely, tetrahedral splittings, is considered. Results are presented that allow tetrahedral splittings of the vibrational states of A₁ and A₂ symmetries for polyad N ≤ 4 to be determined in an analytical form.

The evolution of the Universe in the early (inflationary) stage of its development in the spatially flat Friedmann–Lemaître–Robertson–Walker metric is considered. A theoretical model, described by a van der Waals fluid with the effect of bulk viscosity taken into account is investigated. A solution of the gravitation equation for the energy density is found and an analytical expression for the scale factor has been obtained. To verify the reliability of the cosmological model, the inflation parameters, the spectral index, and the scalartensor ratio were calculated. A comparison of these parameters with data obtained from observations of the Planck satellites is carried out. Conditions for the applicability of the van der Waals model with viscosity to the description of an inflationary Universe are obtained.

Questions on improving the accuracy of multiple-base phase direction finders by rejecting anomalously large errors in the process of resolving the measurement ambiguities are considered. A physical basis is derived and calculated relationships characterizing the efficiency of the proposed solutions are obtained. Results of a computer simulation of a three-base direction finder are analyzed, along with field measurements of a three-base direction finder along near-ground paths.

The type of electrical conductivity of А¹В³₅С⁶₈ semiconductor compounds with defective crystalline structure is modified by the influence of powerful laser radiation. It is shown that at certain power and wavelength of laser radiation acting on the single-crystal п-AgIn₅S₈, an area with the p-type of conductivity is formed in the irradiated region of the crystal. Current-voltage characteristics of homo-junctions created on the basis of n-AgIn₅S₈ are recorded.

The temperature dependences of the thermal and elastic MnSi properties are analyzed within the limits of the self-consistent approach. The role of the anharmonicity of acoustic and optical lattice vibrations is analyzed. It is demonstrated that anomalously weak anharmonicity is characteristic for acoustic phonons. In particular, this explains the temperature dependence of the MnSi bulk compressive modulus. The one-electron contribution is estimated and the anomalous non-lattice contribution to the formation of the temperature dependences of heat capacity and volume thermal expansion coefficients.

The paper presents detailed investigations of dynamic processes occurring in nanostructured Si(Fe) material under the radiation exposure, namely: heating, thermoelastic stress generation, elastic disturbances of the surrounding medium similar to weak shock waves, and dislocation generation. The performance calculations are proposed for elastic properties of the nanostructured material with a glance to size effects in nanoparticles.

The paper focuses on morphology, as well as structural and optical properties of CdSe/TiO₂ heterostructures. The samples were produced by high-voltage pulse method and characterized by methods of scanning electron microscopy, X-ray phase analysis, energy-dispersive analysis, and optical spectroscopy. X-ray phase analysis demonstrated that CdSe in the produced composites has a cubic crystalline structure of sphalerite. Energy-dispersive analysis showed that elemental composition of produced CdSe samples is close to stoichiometric. The study of optical absorption established that modification with CdSe particles shifts the absorption region of TiO₂ to the visible spectrum.

The paper studies physical and mechanical properties of tungsten-nickel-iron-cobalt metal foam alloyed with titanium tungsten carbide. Test specimens are obtained by the liquid phase sintering of powder materials, including those containing tungsten nanopowders. High porosity metal foams are prepared through varying the porosity of powder specimens and the content of filling material. The penetration capability of cylinder projectiles made of new alloys is explored in this paper. It is shown that their penetration depth exceeds that of the prototype with relevant weight and size, made of tungsten-nickel-iron alloy, other factors being equal.

Using the methods of X-ray diffraction and atomic force microscopy, the process of crystallization of an amorphous Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ alloy irradiated with accelerated Ar⁺ ions is investigated. It is found out that an irradiation by the Ar⁺ ions with the energy 30 keV at the ion current density 300 μA/cm² (fluence 3.75·10¹⁵ cm^–2, irradiation time ~2 s, ion-beam short-duration heating up to 350°С, which is 150°С lower than the thermal crystallization threshold) results in a complete crystallization of this amorphous alloy (throughout the bulk of a 25 μm ribbon) followed by precipitation of solid solution crystals of α-Fe(Si), close in its composition to Fe₈₀Si₂₀, stable phase of Fe₃Si, and metastable hexagonal phases. By the methods of atomic force and scanning tunneling microscopy it is shown that nanocrystallization caused by ion irradiation is accompanied by surface relief changes both on the irradiated and unirradiated sides of the Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ alloy ribbon at the depth exceeding by a factor of 10³ that of the physical ion penetration for this material. The data obtained, taking into account a significant temperature decrease and multiple acceleration of the crystallization process, serve an evidence of the radiation-dynamic influence of accelerated ions on the metastable amorphous medium.

The statement and solution of the problem of the expansion of the Universe in nonstationary spherically-symmetric coordinates in the Schwarzschild metric are considered without pressure taken into account. The observational data of astronomers investigating the rates of recession of distant stars are explained on the basis of the obtained solutions.

The results of studies of electrical and gas sensitive characteristics of acetone sensors based on thin nanocrystalline SnO₂ films with various catalysts deposited on the surface (Pt/Pd, Au) and introduced into the volume (Au, Ni, Co) are presented. Films containing impurities of gold and 3d-metals were obtained by the method of magnetron sputtering of mosaic targets. Particular attention was paid to the influence of the longterm tests and humidity level on the properties of sensors. It is shown that the sensors with the deposited dispersed gold layers with Au+Ni and, especially, Au+Co additives introduced into the volume are characterized by the increased stability in the process of testing under prolonged exposure to acetone and also under conditions of varying humidity.

An investigation of structural characteristics and behavior of TiNi-based pore-permeable materials manufactured by the methods of selfpropagating high-temperature synthesis (SHS) at the initial synthesis temperatures T = 400 and 600°С is performed. It is shown that depending on the temperature regime, the resulting structure and properties of the material can differ. It is found out that the SHS-material produced at the initial synthesis temperature T = 400°С possesses the largest number of micropores in the pore wall surface structure due to a high phase inhomogeneity of the alloy. The regime of structure optimization of the resulting materials is described and the main stages of formation of the pore wall microporous surfaces are revealed. It is demonstrated that after optimization of the surface structure of a TiNi-based fine-pore alloy by its chemical etching, the fraction of micropores measuring in size less than 50 nm increased from 59 to 68%, while the number of pores larger than 1 μm increased twofold from 11 to 22%. In addition, peculiar features of interaction between certain cell cultures with the surface of the SHS-material manufactured at different initial synthesis temperatures are revealed. It is found out that the dynamics of the cell material integration depends on the pore wall surface morphology and dimensions of macropores.

Method of finding false paths in sequential circuits is developed. In contrast with heuristic approaches currently used abroad, the precise method based on applying operations on Reduced Ordered Binary Decision Diagrams (ROBDDs) extracted from the combinational part of a sequential controlling logic circuit is suggested. The method allows finding false paths when transfer sequence length is not more than the given value and obviates the necessity of investigation of combinational circuit equivalents of the given lengths. The possibilities of using of the developed method for more complicated circuits are discussed.

The name of the first author should read A. М. Maharramov.