Foreword – page 7
1. EXPERIMENTAL STUDIES OF NANOPARTICLES, NANOSYSTEMS, AND NANOMATERIALS – page 8
Bazzal K., Voropay E.S., Alekseenko N.A., Kovalenko M.N., Trinh N.H., Zajogin A.P.
Research of Al2O3 and Al nanopowder formation processes in plasma under the influence of defocused dual laser pulses on aluminum in the air atmosphere – page 8
Abstract: The influence of the magnitude and type of defocusing of twin laser pulses on the purposeful formation of the component and charge composition of laser plasma under the influence of twin laser pulses on a target made of aluminum alloy AD1 (LSS-1 spectrometer) has been studied. It is shown that when defocusing is more than 1 mm, the intensity of the ion line Al III increases several times in comparison with zero defocusing, the intensity of the ion lines Al II, N II also increases more or less monotonously. At the same time, the intensity of the bands AlO practically becomes zero. At the 1 mm defocusing value, the processes of formation of mixed nanopowders were studied and, under the influence of successive series of double laser pulses with the energy of 53 mJ and the inter-pulse interval of the iss on an aluminum target placed in a closed rectangular glass cuvette, the size of primary Al2O3 particles estimated using high-resolution electron microscopy was mainly 30-40 nm, and Al – 45-60 nm. The particles are collected into agglomerates.
Keywords: oxidized nanopowders Al, Al2O3, AlO suboxides, pulsed laser sputtering, laser plasma, laser spark spectrometry.
Bernatskii D.P., Pavlov V.G.
Field desorption of intercalated caesium atoms from graphene on the (100) iridium face – page 18
Abstract: The desorption of caesium atoms from the quasi-spherical carbonized surface of an iridium single crystal was studied using the field desorption microscopy. Field electron and desorption images of the surface during the formation of graphene on the (100) iridium face are obtained. The field electron images of the emitter surface before intercalation and after intercalation of graphene with caesium atoms do not change. The electric field stimulates the desorption of caesium atoms from the intercalated state, due to the breaking of the bonds of the extreme carbon atoms with the surface of the face (100) of iridium. Using frame-by-frame recording, the possibility is shown of observing the localization of graphene layer defects on the surface of the field emitter. It is also shown that the field desorption of caesium atoms from the intercalated state begins with graphene defects located along the perimeter of the graphene island. It is found that desorption centers can be located not only along the perimeter of the graphene island, but also in its central part in the case of the disordered graphene formation.
Keywords: field desorption microscopy, graphene, field emitter, alkali metals, intercalation.
Bernatskii D.P., Pavlov V.G.
Field desorption microscopy of carbon-coated field electron emitters – page 25
Abstract: Field electron emitters in the form of a metal tip with a carbon film on the surface have a number of promising operational properties. The characteristics of the emitter depend on the phase composition, thickness and uniformity of the film. Determining the parameters of films with a thickness of one or more monoatomic layers presents certain difficulties. In this paper, the formation and characteristics of carbon nanostructures on the surface of field emitters made of iridium and rhenium are studied using continuous-mode field desorption microscopy. In the field desorption images, the regions of carbon nanostructures appear as local flashes (avalanche-like desorption). Frame-by-frame analysis of flash video recordings revealed several stages of the flash formation and revealed differences in the desorption from carbon nanostructures on iridium and rhenium. The found differences are explained by formation of the single-layer graphene on iridium and a multilayer graphene on rhenium. Desorption images reveal inhomogeneities and local differences in the film thickness. It is shown that continuous-mode field desorption microscopy makes it possible to determine the regularities of formation of the field desorption images of various carbon nanostructures, in particular, the single-layer and multilayer graphene on the surface of the field emitter, and to diagnose the surface after carburization. Besides, control the uniformity of the resulting coating is possible. The obtained data are useful for developing technology of the effective field electronic emitters.
Keywords: field desorption, carbon, nanostructures, rhenium, iridium, field emitters.
Blinov A.V., Gvozdenko A.A., Blinova A.A., Kobina A.V., Golik A.B., Maglakelidze D.G., Vishnitskaya O.K.
Determination of optimal parameters for synthesis of silver nanoparticles stabilized with polyethylene glycol – page 32
Abstract: Within the framework of this work, the results are presented of a study of the effect of the concentrations of the stabilizer and precursor on the synthesis of silver nanoparticles. Silver nitrate was used as a precursor, and polyethylene glycol with a molecular weight from 200 to 600 Da was used as a stabilizer. The synthesis was carried out by the method of chemical reduction in an aqueous medium. The obtained samples were investigated by photon correlation spectroscopy and spectrophotometry. The presence of a characteristic absorption band at 400 nm in the absorption spectra of all samples of nanosized silver stabilized with polyethylene glycol was established, which is due to the appearance of surface plasmon resonance in metallic silver nanoparticles. It was also found that at the highest and lowest concentration of the stabilizer, equal, respectively, 0,005 and 0,1 mass. %, the formation of large silver particles with an average hydrodynamic radius from 132 to 1900 nm is observed in the reaction system. As a result, the optimal parameters for the synthesis of aggregatively stable silver nanoparticles were determined: the concentration of silver nitrate См(AgNO3)=0,05 M and the concentration of polyethylene glycol equal to 0,01— 0,05 %. Computerquantum-chemical modeling is carried out. It is found that the interaction of the silver atom with the terminal hydroxogroup in the polyethylene glycol molecule in the elementary act of interaction during the stabilization of silver nanoparticles by this polymer is energetically advantageous. This type of interaction is characterized by an absolute chemical hardness equal to η=0,146, and an internal energy of Е=—2048,34 kcal / mol.
Keywords: silver nanoparticles, polyethylene glycol, stabilizer, precursor, spectrophotometry, plasmon resonance, photon correlation spectroscopy, computer quantum chemical modeling.
Bolotov A.N., Novikova O.O.
Viscometry of nanodisperse magnetic liquids and lubricating oils. 1. Instrumentation for rheological studies of magnetic nanodisperse liquid media – page 44
Abstract: Analysis of the literature sources shows that the existing viscometers are not always and not completely able to provide comprehensive studies of magnetic nanofluids for scientific and practical purposes. Design has been developed of a magnetic rotary viscometer which makes it possible to carry out investigations in a wide range of the magnetic field induction. The magnetic field in the device is directed orthogonally to the shear stress and can vary from zero to 1,7·105 A/m. The device has two measuring gaps filled with liquid, that increases the accuracy of the results of studies of low-viscosity liquids. The viscometer allows you to measure the standard characteristics of magnetic nanofluids (viscosity coefficient, plastic viscosity, ultimate shear stress, etc.), as well as to study the structural features of liquids under shear stresses. The shear rate in the liquid can be stably maintained in a wide range of (1÷5) ·103 s-1. The viscosity of the studied liquids can vary from 10-3 Pa·s to ≈ 102 Pa·s. For studies on a viscometer, a small amount of magnetic nanofluid with a volume of about 3,5 cm3 is required. Using experimental data, the mathematical description of the process of laminar fluid flow in the annular gap of the viscometer made it possible to optimize its geometric dimensions and obtain formulas for calculating the viscosity coefficient, shear stress and shear rate.
Keywords: magnetic nanofluid, rheology, coaxial viscometer, shear stress, shear rate, coefficient of viscosity, magnetic field, external and internal friction.
Bolotov A.N., Novikova O.O., Meshkov V.V.
Viscometry of nanodisperse magnetic liquids and lubricating oils. 2. Metrological analysis of a device for rheological studies of magnetic nanodisperse liquid media – page 56
Abstract: An analysis is carried out of the main sources of methodological errors of the magnetic rotary viscometer. The analysis allowed to improve design and to eliminate critical modes of the research. Theoretical evaluations of the systematic error of the device showed that the value of the relative measurement error can be brought to a value of less than 1%. The greatest contribution to the systematic error of the device is made by the instability of the temperature regime of the nanofluid under study and by the inaccuracy of determining the height of the liquid layer in contact with the measuring cylinder. The measurement of the viscosity of the reference liquids on the magnetic viscometer showed that experimental values are slightly, by about 0.9% overestimated. Calibration of the device on various reference liquids allowed reducing the total measurement error down to tenths of a percent. The magnetic rotary viscometer can be used in non-standard scientific studies of the structure and rheological characteristics of nanofluids, for operational control of the processes of synthesis of magnetic liquids and certification of magnetic nanofluids intended for technical use.
Keywords: magnetic nanofluid, rheology, viscometer, shear stress, shear rate.
Bolshakova N.N., Vahterov E.V., Ivanova A.I., Ped`ko B.B., Semenova E.M.
Thermal-induced domain processes in triglycine sulfate crystals with chromium impurities – page 65
Abstract: The article presents the results of studies of thermally induced domain processes in chromium-containing crystals of triglycine sulfate (TGS). It is shown that a change in the temperature of TGS :Cr3+ crystals in the absence of external electric fields is accompanied by a rearrangement of the domain structure, that occurs most intensively in the region of the phase transition. A depolarizing field of ~1,4·105 V·m-1, which is generated by a gradient change in the temperature of the sample, causes the process of switching its domain structure. In unannealed crystals at impurity concentrations exceeding 5·10-3 wt.%, switching processes are hindered, and the intensity of thermally induced domain processes is significantly lower than that for samples with a lower impurity content. The intensity of the switching processes of TGS :Cr3+ crystals is significantly influenced by the rate of their heating. The dependences of the integral number of polarization-reversal jumps on the heating rate of the samples N=f (V) are extreme. The extrema of the N=f (V) curves lie in the rate intervals (0,2—0,8) K·sec-1. The domain structure of TGS :Cr3+ crystals consists of a matrix of the main domain, lenticular and lamellar domains. Evolution of the domain structure is observed under the influence of an electron beam, accompanied by the growth of domains, their coalescence, and sample switching. High-temperature annealing of crystals leads to their polydomenization.
Keywords: triglycine sulfate, domain structure, ligand, switching processes, annealing.
Greshnyakov V.A., Belenkov E.A.
Formation of a novel diamond-like bilayer based on 5-7 graphene – page 76
Abstract: First-principle calculations of the structure and properties of orthorhombic L5-7 graphene and a novel diamond-like bilayer formed on its basis are performed. The calculations using the density functional theory method showed that L5-7 graphene of Stone-Wales defects should exist stably under normal conditions, and its structure should be corrugated in a wave-like manner. Under strong uniaxial compression of bilayer L5-7 graphene, the formation of the novel diamond-like DL5-7 bilayer can occur. The pressure of the «L5-7 → DL5-7» phase transition is 10,1 GPa, when the interlayer distance in bilayer graphene decreases to 1,61 Å. This bilayer has an orthorhombic crystal lattice (pbam) with the parameters a=10,145 Å and b=5,270 Å. The unit cell of the DL5-7 pbam bilayer contains 32 carbon atoms. The bond lengths vary in the range from 1,5590 to 1,6226 Å, while the angles between these bonds range from 89,62 to 140,8 °. The structure of the diamond-like bilayer should be stable up to 270 K. The calculated values of the surface density and the difference total energy of this bilayer relative to the diamond total energy are 1,19·105 g/cm2 and 1,31 eV/atom, respectively. The DL5-7 pbam bilayer should be a semiconductor with a straight bandgap of 1,63 eV.
Keywords: graphene, topological defects, diamond-like layer, ab initio calculations, crystal structure.
Guseva O.S., Malyshkina O.V., Ivanova A.I., Boitsova K.N.
Barium and calcium niobate ceramics: specific features of their structure – page 85
Abstract: We obtained and studied the samples of ceramics based on barium niobate and calcium niobate CaxBa1-xNb2O6 with different percentages of barium and calcium ( x=1 ; 0,9 ; 0,8 ; 0,7 ; 0,6 ; 0,5 ; 0,4; 0,3 ; 0,2; 0,1 and 0). The effect of the sintering temperature on the structure and dielectric properties of ceramics has been investigated. One batch of the samples was sintered at a temperature of 1100°C, the second at 1250°C. We have shown that the sintering temperature of 1100 °C is not enough to obtain good ferroelectric properties, and the process of grain recrystallization is not completed. According to studies of the elemental composition, in samples sintered at a temperature of 1250 °C with the Ca content greater than 0,5, Ba atoms are not present in all grains, which also affects the course of the temperature dependences of the dielectric constant A sample with x=0,3 is distinguished by its dielectric properties.
Keywords: piezoelectric ceramics, barium-calcium niobate, lead-free materials, grain structure, permittivity.
Devitsky O.V., Kravtsov A.A., Sysoev I.A.
Study of the composition of GaAs1-yBiy films obtained by pulsed laser deposition – page 96
Abstract: Uniaxial cold pressing was used to fabricate the GaAs1-yBiy targets with the Bi content of 1 and 22 %. From the obtained targets, pulsed laser deposition of GaAs1-yBiy thin films on the GaAs and Si substrates was carried out for the first time. We studied the composition, Raman and PL spectra of thin GaAs1-yBiy films obtained from targets with 1 and 22 % of Bi . According to the photoluminescence spectra of thin GaAs1-yBiy films on GaAs substrates, it was determined that the maximum content of Bi in the films did not exceed 2,7 %. The results obtained well correlate with the results of the energy dispersive analysis, the composition of films obtained from targets with the Bi content of 1 and 22 % – GaAs0,975Bi0,025 and GaAs0,973Bi0,027 . It was found that the LO (GaBi) phonon mode of associated with disordering during mixing of GaAs and GaBi phases to be at a frequency of 181 cm-1. For the thin film obtained on the Si substrate, the mode LO (GaAs) was observed that was less pronounced and shifted by 3 cm-1 to the left, while the mode TO (GaAs) , forbidden by the selection rules, had a higher intensity and its shift was of about 1 cm-1 relative to the frequency of the mode TO (GaAs) of the thin film obtained on the GaAs substrate.
Keywords: thin films, pulsed laser deposition, GaAs1-yBiy, Raman light scattering, photoluminescence.
Devitskiy O.V.
Roughness and structure of InGaAsN thin films on Si – page 106
Abstract: By the method of pulsed laser deposition in atmosphere of an argon-nitrogen gas mixture, for the first time thin InGaAsN films on GaAs and Si substrates were obtained from the In0,02Ga0,98As target. The In0,02Ga0,98As target was formed by uniaxial pressing from GaAs and InAs powders. The surface morphology and structure of these thin films are studied by atomic force microscopy and X-ray diffraction. It is shown that In0,02Ga0,98As1-yNy films on Si have an average crystal size of 0,93 nm, and In0,02Ga0,98As1-yNy films on GaAs of 0,99 nm. It is determined that a decrease in the pressure of an argon-nitrogen mixture during pulsed laser deposition of thin In0,02Ga0,98As1-yNy films on GaAs and Si substrates leads to a decrease in the value of the root-mean-square roughness of the surface. The smallest root-mean-square roughness equal to 0,25 nm had a thin In0,02Ga0,98As1-yNy film on a GaAs substrate obtained in vacuum, the largest root-mean-square roughness of 19,37 nm had a thin In0,02Ga0,98As1-yNy film on a Si substrate obtained at the argon-nitrogen mixture pressure of 10 Pa -.
Keywords: InGaAsN , pulsed laser deposition, Raman spectra, thin films.
Dyshekova A.Kh., Karmokov A.M., Khasanov A.I., Kalmykov R.M., Shomakhov Z.V.
Morphology and composition of the interface boundary of sodium chloride single crystals with lead – page 115
Abstract: The interface between liquid lead and sodium chloride after cooling and breaking the contact was investigated by the electron microscopy and X-ray spectral analysis. Accumulation of surface-active impurities, contained both in the bulk of lead and in sodium chloride was found on the fracture surface of the samples. As shown by the results of the X-ray diffraction analysis, the content of impurities on the surface of the sodium chloride substrate exceeds the bulk content by several orders of magnitude. A significant accumulation of silicon and indium impurities is also observed on the lead surface. Anisotropy of spreading of liquid lead over the surface of sodium chloride monocrystals is observed in the studied samples. The separation line of a solidified lead droplet on the surface of sodium chloride with orientation (110) deviates noticeably from a circle. In addition, on the electron microscopic image of the lead interface after detachment from the substrate of sodium chloride of orientation (110), there are areas in the form of a «cigar», in which the accumulation of impurities was detected. The orientation of these regions coincides with the crystallographic direction of the substrate.
Keywords: lead, sodium chloride, electron microscopy, interface, X-ray spectral analysis.
Efremov V.V., Palatnikov M.N., Shcherbina O.B.
Metastable state with high electric conductivity in Li0,12Na0,88Tа0,25Nb0,75O3 synthesized at high pressure – page 123
Abstract: The results are presented of a study of a ferroelectric solid solution Li0,12Na0,88Ta0,25Nb0,75O3 with a perovskite structure based on sodium niobate and synthesized under high pressure and temperature. In the temperature range of 290 — 800 K, the values of the specific conductivity at direct current, the activation energy of charge carriers, and the real part of the dielectric constant were determined by the method of impedance spectroscopy. Evolution of temperature anomalies of specific conductivity and dielectric constant during thermal cycling is shown. The observed effects are associated with structural phase transitions, and the Curie temperature is determined. The Li0,12Na0,88Ta0,25Nb0,75O3 undergoes a second-order phase transition. It was found that a metastable phase is formed in Li0,12Na0,88Ta0,25Nb0,75O3, which has a high electrical conductivity at the room temperature. When heated above the Curie temperature, this phase is destroyed. Possible mechanisms of the discovered phenomena are discussed.
Keywords: impedance spectroscopy, solid solutions based on sodium niobate, high pressure, metastable phase, phase transitions.
Zigert A.D., Dunaeva G.G., Sdobnyakov N.Yu.
Fractal analysis of the maze-like domain structure of ferrite-garnet films in the process of magnetization – page 134
Abstract: In this work, using a set of experimental techniques and specialized software, magnetic bismuth-containing ferrite-garnet films grown on gadolinium-gallium garnet substrates are investigated. The limiting magnetic hysteresis loops are obtained by the method of optical magnetometry for defective and defect-free areas of bismuth-containing ferrite-garnet films. It was found that, far from defects, the loop exhibits a non-coercive behavior within the error limits. For the case of magnetization reversal, a coercive state with HcI ~ 1Oe appears near the defect. For different sections of the limiting magnetic hysteresis loop, the fractal dimension is determined. The obtained values are in the range of DL=1,35÷1,46 for an arbitrary section of the film and DL=1,37÷1,54 for a section with defects. Typical morphological characteristics of the surface of a bismuth-containing ferrite-garnet film have been determined. The results obtained make it possible to predict the relationship between the value of magnetization and the value of fractal dimension for epitaxial bismuth-containing magnetic films of iron garnet.
Keywords: magnetic films, ferrite garnets, bulk defects, domain structure, coercivity, fractal dimension, nanorelief.
Ivanov V.I., Pyachin S.A.
Separation of particles in polydisperse nanosuspension in the laser radiation field – page 146
Abstract: On the basis of a stationary solution of a diffusion equation separation of nanoparticles in a transparent polydisperse aqueous suspension with different types of size distributions was studied under the action of the light pressure arising in the laser radiation field with the intensity of0,5—500 W/cm2. It was found that particles with a radius of more than 100 nm will mainly be precipitated at the bottom of the cell, and the concentration of smaller nanoparticles in the entire volume of the suspension will remain unchanged. In the case of a symmetrical initial distribution of nanoparticles size, the effect of a light beam with high intensity on the suspension leads to a violation of the symmetry of the distribution function curve, as well as a shift of the maximum to the region of smaller particle sizes on the irradiated surface. If the initial size distribution is asymmetric, the initial single-mode particle size distribution is transformed into a two-mode one. This technique can be used to isolate nanoparticles of certain sizes depending on the power density of the radiation.
Keywords: laser radiation, polydisperse medium, nanoparticles, deposition, separation.
Ivanov D.V., Antonov A.S., Semenova E.M., Ivanova A.I., Anofriev V.A., Sdobnyakov N.Yu.
Different schemes for obtaining fractal relief of nanosized platinum films – page 156
Abstract: The morphology of the relief of nanosized platinum films on the mica surface is investigated using the scanning probe (in the atomic force mode) and tunneling microscopy. Platinum films were investigated immediately after their preparation in a magnetron sputtering facility, as well as after annealing in a muffle furnace in an air atmosphere. Annealing made it possible to establish the possible ranges of variation of the fractal dimension and the altitude parameters corresponding to degradation of the nanorelief. The values of the fractal dimension were obtained for films of different thicknesses using two alternative methods of investigation at different initial scales of samples: based on the data of an atomic force microscope – c D=2,17÷2,38 and a scanning tunneling microscope – c D=2,28÷2,50 depending on the sequence of deposition of layers and annealing of films. For comparison, experimental data of other authors are presented. The choice of the sequence of operations for magnetron sputtering and annealing, and external conditions makes it possible to formulate recommendations for development of the technology for «growing» structures with a given surface morphology.
Keywords: scanning probe microscopy, atomic force microscope mode, scanning tunneling microscopy, magnetron sputtering, annealing, nanorelief, roughness parameters, fractal dimension, platinum films.
Ivanova A.I., Zigert A.D., Tretyakov S.A., Semenova E.M., Dilmieva E.T., Karpenkov A.Yu., Barabanova E.V., Sdobnyakov N.Yu.
Micromorphology of the surface of rapidly quenched Heusler-alloys – page 166
Abstract: The paper describes the results of the scanning electronic and atomic force microscopy research of the surface structure of the Ni57Mn21Al22, Ni57Mn21Al19Si3, Ni40Co10Mn34Al16 rapidly quenched ribbons. The influence of the chemical composition on the size, boundary geometry and structure of the grains is considered. It is shown that all the test samples have a nano-sized martensitic relief, and its parameters are determined. It has been established that the cross section of the ribbon is represented by crystalline grains of different shapes which are due to differences in the cooling rates along the edges and in the center of the samples. Elemental mapping of the cross-sectional surface of the ribbons was carried out using an X-ray energy dispersive spectrometer, and a uniform distribution of chemical elements in the samples was established. It is shown that the cobalt doping of Ni57Mn21Al22 ribbon causes changes in the micromorphology of the surface and has a significant effect on the magnetic properties of rapidly quenched ribbons: field dependences of themagnetization and domain structure.
Keywords: Heusler alloys, structural transformation, rapidly quenched ribbons, surface microstructure, martensitic relief.
Ivanova A.I., Marinicheva K.A., Tret’yakov S.A., Ivanov A.M., Molchanov S.V., Kaplunov I.A.
Temperature dependence of optical transmission of germanium single crystals – page 177
Abstract: In this work, we investigated optical transmission in the wavelength range of 2—14 µm of low-resistance germanium crystals (1—3 Ω·cm) doped with donor and acceptor impurities in the temperature range from 86K to 523 K. The values of the attenuation coefficients for investigated crystals are obtained. Minimum attenuation coefficients α of 0,0015—0,0231 cm-1 in the temperature range from 86K to 323K are characteristic for germanium single crystals doped with antimony in the range 2,1—11 μm. Studies have shown that the low values of α and the transmittance τ at a wavelength of 3,39 μm for Ge:Bi and Ge:Sb crystals make it possible to use these low-resistance germanium crystals for gas helium-neon lasers at temperatures from 86K to 323K. The temperature changes in the geometry of the crystal surface are investigated at the nanoscale level. It is shown that heating crystalline germanium leads to an increase in the diffuse reflection of radiation from the surface. The possibility of using the low-resistance germanium crystals doped with antimony as elements of infrared optics in the temperature range 86—373 K has been demonstrated.
Keywords: germanium single crystals, temperature stability, optical transmission, attenuation coefficient, surface nanorelief, diffuse reflection.
Kalmykov R.M., Karmokov A.M., Shomakhov Z.V., Dyshekova A.Kh.
Nanosized structures in PbTe matrix with CdSe impurities – page 187
Abstract: In this work, electron microscopic studies of semiconductor compounds based on PbTe with impurities of dispersed CdSe phases have been carried out. As shown by the research results, in the initial undoped PbTe compound, the content of lead atoms is about 63,8 wt.%, and the tellurium content was 36,2 wt.%, i.e. corresponded to the stoichiometric composition. According to the electron microscope images, these components are evenly distributed over the area. The results of the study also showed that the formed new phases had grain sizes from 90 nm to 2 μm. The obtained values of the lattice parameter for the lead telluride compound and crystal system are in good agreement with the literature data. The structure of the resulting phases has the same symmetry as the initial undoped PbTe compound, a face-centered cubic lattice with the Fm3m symmetry class. In the molecules of the newly formed phases, in which the abundances of the elements Cd and Se prevailed, a change in the crystal lattice syngony was found.
Keywords: lead telluride, cadmium selenide, nanoscale structures, lattice parameter, phase changes.
Kartashynska E.S.
On estimation of the area per a surfactant molecule in a 2D monolayer during the liquid-expanded-liquid-condensed phase transition at the air/water interface – page 196
Abstract: A method is proposed to estimate the area per molecule of a surfactant monolayer Ac at the transition onset of the liquid-expanded to a liquid-condensed phase based on two theoretical models. A thermodynamic model with account for nonideality of the mixing entropy makes it possible to estimate the Gibbs energy of surfactant clusterization using the Π-A isotherms obtained at different temperatures. On the other hand, the quantum-chemical approach also makes it possible to calculate this thermodynamic parameter and assess the structural features of the obtained monolayers. The values of the Gibbs clusterization energies of small surfactant associates and the geometric parameters of the monolayer unit cells were previously calculated using the quantum-chemical semiempirical method PM3 for eight classes of amphiphilic compounds: saturated and ethoxylated alcohols, saturated and cis-monoenic carboxylic acids, α -hydroxylic and α -amino acids, N -acyl-substituted alanines and dialkyl-substituted melamine. These parameters are used in the thermodynamic model with account for nonideality of the mixing entropy to calculate Ac . The estimated values Ac adequately reflect the experimental temperature dependence for the considered phase transition: with an increase in temperature the area per surfactant molecule of a fixed chain length decreases, and vice versa, with an increase in the surfactant chain length at a fixed temperature, the value Ac increases. This makes it possible to use the proposed approach for prognostic purposes.
Keywords: amphiphilic monolayer, clusterization Gibbs’ energy, unit cell, phase transition, thermodynamic model.
Kovalenko M.N., Alekseenko N.A., Markova L.V., Rutkovskaiy L.S., Patapovich M.P., Zajogin A.P.
Studies of processes of the precursor formation for production of CuAl2O4 nanoceramics at the effect of double laser pulses on AD1 and M2 alloys in the air atmosphere – page 209
Abstract: A study of formation of mixed Al nanopowders, copper and aluminum oxides, and precursors for production of CuAlO2 and CuAl2O4 nanoceramics under the influence of double laser pulses with energy of 53 mJ and the interpulse interval of 10 microseconds on a target consisting of plates of aluminum grade AD1 and copper grade M2, 0,4 mm thick, glued together and placed in a closed rectangular glass cuvette. It is found that the successive exposure of a series of double laser beams to an aluminum target and then to a copper target leads to a multiple increase in the yield of AlO suboxides, aluminum and copper ions and atoms in the laser torch, compared with the exposure to single laser pulses. To better understand the hidden mechanisms of this dependence, we study the processes occurring both on the surface and in the near-surface laser plasma inside the resulting microchannel when the target is broken by a series of single and double laser pulses. The possibility of obtaining precursors for the production of nanoceramics such as CuAlO2, CuAl2O4 is shown.
Keywords: oxidized nanopowders Al , Al2O3, AlO suboxides, copper oxides, CuAl2O4, CuAlO2, pulsed laser sputtering, laser plasma, laser spark spectrometry.
Kravtsov A.A., Chikulina I.S., Vakalov D.S., Chapura O.M., Krandievsky S.O., Devitskiy O.V., Lapin V.A.
Luminescence of YAG: Ce doped with silver nanoparticles – page 220
Abstract: This work was the first to study the effect of silver nanoparticles on the luminescence of cerium doped yttrium-aluminum garnet. A sol with the size of silver nanoparticles of ≈100 nm was synthesized using the method of chemical reduction. Phosphor ceramic powder of the yttrium- aluminum garnet doped with cerium was obtained by the two-stage precipitation method. The silver nanoparticles sol was introduced into the precursor powder before calcination in concentrations from 0,125 to 0,1 ml. It was shown that the photoluminescence intensity increased in comparison with the reference when we used this method of introducing silver nanoparticles. The optimal concentration within the study was 0,25 ml. At this concentration, the increase in the photoluminescence intensity at a wavelength of 540 nm was about 10 %. Studies have shown that silver nanoparticles can be successfully used to increase the brightness of the phosphor of the yttrium-aluminum garnet doped with cerium without distortion and deterioration of spectral characteristics.
Keywords: silver nanoparticles, ceramic powder, luminescence, yttrium-aluminum garnet doped with cerium, optical properties.
Krylov A.A., Alekseev V.G., Feofanova M.A., Ivanova A.I., Baranova N.V.
Change in the surface structure of semiconductor polymer films during reverse oxidation-reduction – page 228
Abstract: The surface morphology of films of semiconducting polymers: polyaniline, poly-o-toluidine, poly-naphthylamine was studied by scanning electron microscopy. The films were obtained by electrochemical synthesis from solutions of their monomers acidified with mineral acids by the method of cyclic voltammetry. The films are formed on platinum substrates made according to the principle of bimetallic plates. The processes of reversible oxidation and reduction of the obtained films were carried out using an electric current in aqueous solutions of hydrochloric acid, which led to the doping of polymers with chloride anions. It was shown that the surface of films of polyaniline and poly-o-toluidine has a similar structure, consisting of numerous spherical grains ranging in size from 1 to 5 μm. The surface of poly-α-naphthylamine films is significantly different and consists of dendrons and large pores. In this case, in all cases, the observed supramolecular formations for films in the oxidized state are somewhat larger than for films in the reduced state, which is due to a change in the conformation of macromolecules.
Keywords: .
Kuznetsov Yu.A., Lapushkin M.N.
Electron-stimulated desorption of lithium atoms adsorbed on the surface of gold-lithium intermetallic – page 235
Abstract: A thin film of the intermetallic compound LixAuy was obtained at room temperature by deposition Li atoms onto a layer of adsorbed gold on the tungsten surface. The processes of electron-stimulated desorption of Li atoms from the surface are investigated. It is shown that electron-stimulated desorption of Li atoms can be observed only in the case when at least one monolayer of Li and Au atoms is deposited. The dependence of the electron-stimulated desorption yield of Li atoms on the amount of deposited has a maximum when two monolayers of atoms Li are deposited on Au . The results obtained indicate the LixAuy formation of various stoichiometry: from with a deficit of lithium atoms to the deposition of two monolayers of atoms. In the kinetic energy distribution of desorbed Li atoms, two peaks were found: high-energy and low-energy. The first of them is associated with the desorption of Li atoms from LixAuy , and the second with the desorption of Li atoms from the upper monolayer of Li atoms.
Keywords: electron-stimulated desorption, adsorption, alkali metals, gold, intermetallic compounds.
Kuznetsova Yu.V.
Improving the efficiency of the contact force method of the atomic force spectroscopy – page 243
Abstract: We propose a technique that optimizing the method of contact force spectroscopy. With the help of a macro language integrated into the NOVA software of the Solver P47 scanning probe microscope, an algorithm was developed that allows analyzing force curves without leaving its main interface. The approbation of the method was done on samples of synthesized polymer, since one of the most important mechanical properties determining their range of applications is elasticity. In this paper, local values of the Young’s modulus on the polymer surface are obtained by the method of contact force spectroscopy using the YUNG script developed using a macro language integrated into the control program of a scanning probe microscope. It is shown that the use of the YUNG script makes it possible to optimize the method of contact force spectroscopy by searching for the exponent γ, choosing a model for calculating the interaction force for further determination of the local Young modulus.
Keywords: atomic force microscopy, the method of contact atomic force spectroscopy, Young’s modulus, elastic modulus, Hertz model.
Kuleshov D.S., Blinov A.V., Blinova A.A., Yasnaya M.A., Maglakelidze D.G., Vishnitskaya O.K.
Comparison of the efficiency of different detectors of the scanning electronic microscope « MIRA-LMH» for studying microstructure of nanomaterials – page 250
Abstract: At the first stage, the objects of study were synthesized – silicon dioxide by the Stober method, where tetraethoxysilane was used as a precursor, and a nanocomposite ZnO–Au by the sol-gel method using the aqueous zinc acetate dihydrate as a precursor. At the second stage, the microstructure and morphology of the obtained samples were investigated by scanning electron microscopy on a «MIRA-LMH» scanning electron microscope (Tescan company) using both a classical secondary electron detector and additional detectors – intralens secondary electron detector and back-scattered electrons detector. As a result of the research, it was found that when using the secondary electron detector, practically no noise images with topographic contrast are obtained. When using the intralens secondary electron detector, images of only material contrast are created, without the influence of the surface relief. Also, the use of this detector made it possible to obtain high-quality images with a high resolution at a distance of 5 mm from the sample. When using a back-scattered electrons detector with a working distance to the sample of 8 mm and increasing the resolution of the microscope, the resulting images have low border contrast, but represent compositional information with high sensitivity. Thus, it was found that the intralens secondary electron detector with a working distance of 5 mm to the sample is optimal for obtaining clear images of the microstructure of the surface of nanomaterials at multiple magnifications.
Keywords: silicon dioxide, nanocomposite ZnO—Au , scanning electron microscopy, detectors, microstructure.
Lapin V.A., Kravtsov A.A., Kuleshov D.S., Malyavin F.F.
Investigation of possibility of the misfit dislocation density reduction in Ge / Si films with a buffer layer – page 263
Abstract: The possibility of improving the quality of Ge/ Si heteroepitaxial structures with a buffer layer is investigated. It is shown that when using a preparatory layer consisting of nanostructures overgrown with a low-temperature buffer layer, it is possible to manifest the so-called effect of annihilation of the misfit dislocations in the bulk of the buffer layer Buf , which significantly improves the quality of the resulting structures. The dependence of the morphology of the surface of the pure Ge layer on the buffer on the growth time of nanostructures in the Si /Buf interface is presented. The optimal technological parameters of the growth of nanostructures for obtaining a Ge layer with a minimum roughness value are revealed. The best results were achieved when the deposition time of nanostructures was 2 min. At the same time, the minimum surface roughness value of 78 nm was achieved. It is shown that with a further increase in the size of the nanostructures, the process of annihilation of defects slows down, and the growth of the low-temperature buffer layer is replaced by a three-dimensional island growth, which increases the differences in the relief of the surface of the grown layer.
Keywords: heteroepitaxy, molecular beam epitaxy, misfit dislocations, buffer layer, defect annihilation.
Malashenko V.V., Malashenko T.I.
Specific features of inelastic processes in materials with nanoscale defects – page 272
Abstract: The high strain rate deformation of alloys containing Guinier-Preston zones under high- energy external influences has been theoretically analyzed. The analysis was carried out within the framework of the theory of dynamic interaction of structural defects. The investigated dissipation mechanism consists in the irreversible transfer of energy of an external impact into the energy of dislocation vibrations. An analytical expression for the dynamic yield stress taking into account all structural defects of the alloy has been obtained. It is shown that, under high-energy external influences, nanoscale defects affect the nature of the dependence of mechanical properties on the concentration of atoms of the second component. The dependence of the dynamic yield stress on the atomic concentration of the second component becomes nonmonotonic and has a minimum. Numerical estimates of the concentration corresponding to the minimum yield stress has been made. At this concentration value, a transition occurs from the dominance of the dislocation drag by the Guinier-Preston zones to the dominance of the drag by the atoms of the second component.
Keywords: high strain rate deformation, dislocations, Guinier-Preston zones, point defects, nanomaterials.
Malyshkina O.V., Patsuev K.V., Ivanova A.I., Ali M.
Comparative analysis of the properties of sodium niobate and sodium – lithium niobate ceramics – page 278
Abstract: The authors studied the effect of the temperature of sodium niobate synthesis on the state ofpolarization in c eramic samples of pure sodium niobate and modified with lithium. A comparative study of the structure and pyroelectric properties of the obtained samples has been carried out. It is shown that the introduction of lithium as a modifier leads to a significant change in the structure in the depth of ceramic samples based on sodium niobate. If in the depth of the pure sodium niobate samples, as well as on the surface, there are individual grains, then the central part of the sodium niobate- lithium niobate ceramics is a continuous mass in which individual grains are not observed. In all samples, except for pure sodium niobate, which was synthesized by double synthesis (the first at 650 °C, the second at 700 °C), the existence of a polarization gradient along the thickness of the samples was established. The gradient is directed from the side corresponding to the positive end of the polarization vector to the side corresponding to the negative end of the polarization vector.
Keywords: piezoelectric ceramics, lead-free materials, pyroelectric effect, spontaneous polarization, grain structure.
Mamaev D.V., Merkuryev S.A., Malyshkina O.V.
Pore percentage estimation of piezoelectric ceramics using CCANN and image made with SEM – page 286
Abstract: The authors synthesized samples of piezoelectric potassium sodium niobate ceramics of 10,25 and 40 pore percentage by volume. Capsule convolutional artificial neural network has been developed for estimation of the pore percentage in images. Using the scanning electron microscopy, f learning massive of examples was formed (photographs of surface and edges of so-synthesized samples). Development and approbation of the capsule convolutional artificial neural network was completed in a few stages. During the first stage, the network was trained using a backpropagation method. Secondly, it was tested by a testing set. At the final stage we made a comparison of the acquired results with the results of the density comparing method. The article shows that this method can be used the pore percentage estimation in sodium niobate ceramics because the acquired results are comparable with the results of other methods. It was found that the samples where the pores were not made also have some pore percentage (about 5%).
Keywords: piezoelectric ceramics, capsule convolutional artificial neural network, artificial neural networks, pore percentage.
Maraeva E.V., Moshnikov V.A.
Nitrogen thermal desorption of as a control method for determination of the nanoparticle size in compositions based on zinc oxide and hydroxyapatite – page 294
Abstract: In this paper we consider the possibility of using the nitrogen thermal desorption method for determining the size of nanoparticles in compositions based on hydroxyapatite and zinc oxide. The compositions in the form of tablets were obtained using a manual water press. The initial powders of hydroxyapatite were obtained by chemical deposition using a microwave radiation. Using the BET sorption method, the specific surface area of the powders is analyzed before and after pressing, and the effect of the composition formulation on the specific surface area is investigated. The calculation of the average sizes of nanoparticles in composites is given on the basis of the results of sorption measurements within the framework of the models of spherical and rod-like nanoparticles. The field of application of the materials under consideration is medicine, including the use of nanocomposites in targeted drug delivery and in bone engineering as bioactive coatings applied to the surface of a metal bioimplant.
Keywords: hydroxyapatite, zinc oxide, adsorption, specific surface area.
Matveev A.V., Mashukov M.Y., Nartova A.V., Sankova N.N., Okunev A.G.
Automatic analysis of microscopy images using the DLgram01 cloud service – page 300
Abstract: The study of materials by microscopy often includes counting the number of observed objects and determining their statistical parameters, for which it is necessary to measure hundreds of objects. The created DLgram01 cloud service allows specialists in the field of materials science who do not have programming skills to perform automated image processing – to determine the number and parameters (area, size) of the objects under study. The service is developed using the latest achievements in the field of deep machine learning. To train a neural network, the user needs to label only several objects. The neural network is trained automatically in a few minutes. Important features of the DLgram01 service are the ability to adjust the results of neural network prediction, as well as obtaining detailed information about all recognized objects. Using the service allows to significantly decrease the time for quantitative image analysis, reduce the influence of the subjective factor, increase the accuracy of the analysis and its ergo-intensity.
Keywords: microscopy, recognition, nanoparticles, deep neural networks, artificial intelligence.
Muratova E.N.
Thermal studies of porous aluminum oxide membranes – page 312
Abstract: Study of optical properties of nanoscale membranes of porous anodic alumina can significantly expand the scope of this material. The paper presents the results of thermal imaging studies of porous anodic alumina membranes with various structural parameters. Temperature distribution profiles for membranes obtained in various electrolytes based on sulfuric, oxalic and orthophosphoric acids have been constructed. It was found that the shielding of IR radiation is more pronounced (approximately 30 %) in membranes with a smaller pore diameter ds pore≈20 nm compared to membranes with a larger pore diameter dl pore≈200 nm. This is due to the scattering of thermal radiation on structural inhomogeneities, which are much higher in porous anodic aluminamembranes obtained with sulfuric acid. Small-diameter pores, under-etched areas and defects act assources of inhomogeneity. Also, due to the increased activity of sulfuric acid in comparison with other acids used, more anions are incorporated into the structure of the sample.
Keywords: porous aluminum oxide, membranes, pore diameter, optical properties, thermal imager, IR radiation.
Musskaya O.N., Krut’ko V.K., Kulak A.I., Krutsko E.N.
Composites based on calcium phosphates and copper nanoparticles – page 320
Abstract: Copper nanoparticles were synthesized by the borohydride method using polymer stabilizers (polyethylene glycol, polyvinylpyrrolidone). It was found by optical spectroscopy that copper nanoparticles obtained at a molar ratio Cu / polymer of 1:(3–6) have the highest stability (up to 1.5 months). It was shown that in the absence of polymer or at its low content (molar ratio Cu / polymer 1 : 1), the resulting nanoparticles aggregate and a precipitate forms containing copper and its oxides (Cu2O , CuO). By mechanical mixing of amorphized calcium phosphates (in powder and gel form) and copper nanoparticles (in the form of a colloidal solution), a powder composite containing Ca19Cu2H2(PO4)14 and Cu2PO4OH phases was obtained. It was shown that during the co-precipitation of calcium phosphates and copper nanoparticles, copper ions are incorporated into the crystal lattice of calcium phosphates with the formation of mixed acidic and medium salts.
Keywords: amorphized calcium phosphates, hydroxyapatite, copper nanoparticles, polyvinylpyrrolidone, polyethylene glycol, composites.
Mustafaev G.A., Mustafaev A.G., Cherkesova N.V.
Charge distribution in the Al2O3-SiO2 system exposed to ionizing radiation – page 329
Abstract: Metal-insulator-semiconductor (MIS) structures are key elements of modern electronic technology, including devices operating under conditions of exposure to penetrating radiation. One of the possible approaches to reducing radiation effects in MIS structures is the use of dielectrics, which reduce the generation and accumulation of excess space charge in the bulk of the dielectric. We investigated the system of dielectrics Al2O3–SiO2. The study shows the suitability of using MIS structures based on a system of dielectrics for formation of devices with high radiation resistance. Applying a Al2O3 layer on top of the SiO2 layer improves the performance of MIS structures by increasing the uniformity of parameters. The main effect of the influence of the Al2O3 layer on the parameters of the structures is to reduce the mechanical stresses at the interface SiO2 -substrate. The trapping of electrons in Al2O3 , compensates for the charge of the trapped holes in SiO2 , and reduces the parasitic current through Al2O3.
Keywords: ionizing radiation, surface states, charge distribution, system of dielectrics, radiation resistance.
Permiakov N.V.
The use of liquid probes based on an eutectic solution for studying the conducting properties of thin films – page 338
Abstract: The work is devoted to development of a modular four-probe setup using a liquid contact based on an indium-gallium eutectic solution ( EGaIn), which can be used to create clamping liquid contacts that do not introduce mechanical deformation into the measured structures. It is proposed to use this setup for measuring the current-voltage characteristics of thin-film samples. A modular measurement scheme is assumed. Each probe is driven by four motors to position and expel a drop from the syringe to form the desired contact area size. Optical control is used to prepare the probes and measure the diameter of the formed contact areas. The parameters for the manufacture of liquid probes are selected, namely, the speed of extrusion and movement of the probe along the vertical axis to form a conical droplet. The installation is controlled in the LabView environment.
Keywords: indium-gallium eutectic, electric probe, adjustable contact area size, thin films, current- voltage characteristic.
Polukhin V.A., Belyakova R.M., Kurbanova E.D.
Influence of alloying Ti, Mo and W on the kinetic and strength characteristics of membrane alloys based on Nb and V – page 345
Abstract: An analysis was carried out of influence of , Ti Mo and W on the nature of the amorphous nano- and crystalline structures on the strength and kinetic characteristics – diffusion D and permeability Φ of hydrogen in membrane alloys based on binary Nb – Ni and V – Ni . Doping with Nb – V alloys by titanium, molybdenum and tungsten leads to the gradual replacement of niobium and vanadium, and promotes the formation of several minor phases while acting as barriers for hydrogen diffusion, but contributing hydride reduction processes. A close dependence of the hydrogen kinetics was revealed not only on thermodynamic parameters – temperature and pressure, but also on the presence of free volume in the formed amorphous, nanocrystalline and crystalline alloys. So, the processes of selectivity, the dynamics of hydrogen – its flux J determined by the product of diffusion D and permeability Φ, J = D × Φ depend on the basic composition and the choice of alloying elements (Ti, Mo and W), as well as the formed structures – amorphous, nanocrystalline and duplex, represented by multiphase crystalline microstructures. It was found that a carefully selected composition determines the productivity of the selective process and promotes the release of high-purity hydrogen with its subsequent applications for green energy.
Keywords: hydrogen, amorphous and nanocrystalline alloys, V, Ni, Ti, Zr, Nb, structuring, selectivity, solubility, permeability, diffusion, hydrides, accumulation, thermal stability, fragility, crystallization, modeling, icosahedral clusters, nanophases, duplex structure, Laves phases..
Sverdlik G.I., Ataeva A.Yu., Ataev A.R., Khadzaragova E.A., Vazieva L.T.
Analysis of methods for studying the size of nanoparticles – page 358
Abstract: In the presented work, various methods for determining the size of nanoparticles are considered. An effective method for finding possible options has been determined. Information on various methods and studies was selected and analyzed. Fundamentally different methods for finding the sizes of nanoparticles are considered. Non-contact (optical) methods are the most promising. The particle size ranges of the investigated particles are analyzed and presented using the next methods: optical microscopy, electron microscopy, scanning probe microscopy. The principles of operation and possible schemes of installations for studying the material under study are described. The sedimentation method, using centrifugation and the X-ray principle of detection, is described in more detail. Its advantages over other methods are noted. Examples are given of its use in an experimental setup that allows obtaining differential and integral characteristics in various bases, which make it possible to analyze the particle size distribution in the granulometric study of materials, including nanomaterials.
Keywords: nanoparticles, sedimentation method, sedimentometer, gravity sedimentation, centrifugation, differential and integral curves.
Semenova E.M., Lyakhova M.B., Sinkevich A.I., Ivanov D.V., Antonov A.S., Sdobnyakov N.Yu.
Fractal analysis of the nanostructure of a heterogeneous high coercity alloy – page 368
Abstract: The atomic force microscopy was used to obtain images of the nanostructure of components of a heterogeneous intermetallic SmCoCuFeZr compound in a highly coercive state. At the microlevel, two types of regions were distinguished in the alloys, differing in integral elemental composition and coercivity intervals. Based on the atomic force microscopy data, an analysis of the fractal characteristics of the surface is carried out on both of the above types of areas. It is shown that the fractal dimension of the nanostructure correlates with the local coercivity of the phase components. The phase component with a relatively low coercivity demonstrates the possibility of the existence of structures with fractal dimensions in the 2,396–2,475 range corresponding to a moderately developed fractal relief. In this case, the high-coercive component with a regular nanostructure is characterized by a higher fractal dimension of 2,452–2,508, and in some areas of the sample there were regions with a fractal dimension up to the value of 2,577.
Keywords: atomic force microscopу, nanorelief, nanostructure, surface morphology, coercivity, fractal dimension.
Sidorov N.V., Teplyakova N.A., Palatnikov M.N.
Hydrogen bonds in lithium niobate crystals of different composition – page 376
Abstract: An analysis of complex defects was carried out by IR-spectroscopy method in the area of OH– groups stretching vibrations. The defects are caused by hydrogen bonds present in the structure of nominally pure congruent lithium niobate crystals, crystals of stoichiometric composition with a different Li /Nb ratio, as well as in LiNbO3:Zn(0,04–6,5 мол.% ZnO) crystals doped in a wide range of concentrations due to direct doping of the melt method. Dopants were determined to influence OH– groups concentration, type and localization of complex defects in the crystals structure. A change in the amount of hydrogen sites in the LiNbO3 crystals structure was shown to evaluate the composition either stoichiometric or congruent. The character of OH– groups complexing with cation sublattice point defects was shown to change when doped crystals LiNbO3:Zn(0,04–6,5 мол.% ZnO) trespass concentration thresholds. Dopant incorporation mechanism changes at this drastically, thus crystal properties also change quite sharply. Frequencies (as well as quasi-elastic constants of OH– bonds) change in congruent and doped crystals due to a difference in electronegativities and ionic radii of the main and dopant cations.
Keywords: single crystal, lithium niobate, defects, IR absorption spectra, doping, stretching vibrations of OH– group.
Sidorov N.V., Teplyakova N.A., Palatnikov M.N.
Influence of the method of doping on uniformity and optical properties of LiNbO3:Mg crystals – page 383
Abstract: The paper considers results for strongly doped turned to a single domain state crystals LiNbO3: Mg(5,03 mol % MgO and LiNbO3:Mg ( 4,75 mol % MgO ). Magnesium concentration in these crystals is close to each other and to threshold ≈5 mol % MgO . Crystals were grown from a charge synthesized using precursor LiNbO3:Mg (homogeneous doping method) and from a charge obtained at a direct addition of magnesium to the charge (direct doping method). Complex studies were carried out by Raman spectroscopy and laser conoscopy. Compositional homogeneity and some optical properties of studied crystals are considered. Homogeneous doping with precursor Nb2O5:Mg method allows us to obtain heavily doped LiNbO3:Mg single crystals with low coercive field and more compositionally homogeneous than method of direct melt doping with magnesium. In this case, a more uniform distribution of the dopant in homogeneously doped crystals begins to form at the stage of Nb2O5:Mg precursor synthesis during the formation of chemically active complexes that predominantly determine the oxygen-octahedral structure of the Nb2O5:Mg precursor.
Keywords: lithium niobate crystal, homogeneous and direct doping, Raman scattering, laser conoscopy.
Skachkov V.M., Pasechnik L.A., Medyankina I.S., Sabirzyanov N.A.
Study of the properties of diffusion-hardening composite solders modified with a Ti – Mo powder mixture – page 392
Abstract: The article discusses the possibility of regulating the properties of diffusion-hardening solder based on low-melted gallium-tin, gallium-indium-tin, gallium-tin-zinc alloys and a solid component consisting of a copper-tin alloy powder by introducing a mixture of inert powders of metallic titanium and molybdenum after the heat treatment at various temperatures. The microhardness and thermal stability of composite diffusion-hardening solders are evaluated. It is shown that the heat treatment at higher temperatures contributes to the transition of the solder to an equilibrium state, while a sharp increase in hardness occurs. The phases formed as a result of diffusion hardening were determined by the method of X-ray phase analysis. It is shown that at different processing temperatures, different phases are formed – nanoscale intermetallic compounds. Due to small additives of fillers that are inert or weakly interacting with gallium, but are well wetted by it, the characteristics of the diffusion-hardening solder are significantly improved.
Keywords: composite diffusion-hardening solders, metal powder, properties, microhardness, differential thermal analysis.
Staritsyn M.V., Fedoseev M.L., Kaptelov E.Yu., Senkevich S.V., Pronin I.P.
Structure changing of submicron PZT films with a fine variation of the composition corresponding to morphotropic phase boundary – page 400
Abstract: The paper discusses the possibility of a fine variation in the composition of submicron ferroelectric films of lead zirconate titanate solid solutions corresponding to a morphotropic phase boundary. Composition was varied by changing the distance from the target to the substrate in the range of 30–70 mm in an installation for radio-frequency magnetron sputtering of a ceramic target, in which films deposition occurred on a «cold» platinized silicon substrate. This made it possible to change the composition of the deposited films (i.e., the elemental ratio of Zr and Ti atoms) in the range of 0–1,5 % while maintaining the single-phase perovskite films annealed at 580 °С. In this case, the films were characterized by elemental inhomogeneity of the composition over the thickness, reaching several percents. The thickness of thin lead zirconate titanate layers was 500 nm. Changes in the microstructure and crystal lattice parameters were studied. The change in the composition of the films was accompanied by significant changes in the nature of the spherulite microstructure and growth texture. A sharp jump in the quasi-cubic crystal lattice parameter was discovered, which may be caused by the phase transformation of the ferroelectric phase – from the rhombohedral modification to the two-phase state, presumably consisting of monoclinic and tetragonal modifications.
Keywords: lead zirconate titanate solid solutions, thin films, morphotropic phase boundary, fine variation in composition, microstructure.
Starodub O.S., Voskresenskij V.M., Sidorov N.V., Palatnikov M.N.
Comparative analysis of the influence of doping ions of yttrium and boron formation of defects in lithium niobate crystals – page 411
Abstract: Lithium niobate crystals, which are a widely used and highly demanded as nonlinear optical material, are remarkable for their ability to vary a wide range of ferroelectric and nonlinear optical characteristics depending on the type and concentration of the impurity ion, as well as on the Li/Nb ratio. Based on our approach to modeling clusters in the lithium niobate crystal, in which the cluster grows not by unit cells, but by oxygen octahedra, we have carried out a comparative analysis of the features of the incorporation of impurity ions of yttrium and boron with the same charge +3 into the crystal. It is shown that due to the different ionic radii the incorporation proceeds by to two mechanisms. If for yttrium the usual mechanism operates, when the impurity ion is localized inside the oxygen octahedron. The ion of boron, i.e. a nonmetallic element, is incorporated into the tetrahedral voids of the structure, namely, into the oxygen planes forming the octahedron. In this case, the influence of these impurity ions on one of the most important characteristics of lithium niobate turns out to be diametrically opposite: yttrium enhances the photorefractive effect, boron decreases it, which must be taken into account in the direction of targeted use of lithium niobate crystals.
Keywords: lithium niobate, modeling, clusters, vacancy models, sublattice defects, single crystals, ferroelectrics.
Khubolov B.M.
Physico-chemical properties of electrochromic complex tungsten oxides – page 421
Abstract: A brief review of the problem of electrochromism in disordered thin films of complex tungsten oxides is given on the basis of experimental results published earlier. The problems of the ion- electron ordering in complex tungsten oxides MxWO3(M=Na or K and x=0,3) are regarded as well as their relationship with the dynamics of the process of electrochromic coloring in these condensed systems. Possible ways of solving the indicated problems are considered. The starting point of our campaign to study the electrochromism and to develop the physical grounds of the technology of electrochromic devices was the rejection of the generally accepted electrochemical consideration of this phenomenon. We are convinced that the electrochromic effect is a purely solid-state one occurring in a condensed system with a strong electron correlation. The electronic structure of a solid at the solid- electrolyte interface largely controls the nature and rate of reactions that take place on its surface. In the case of oxides, the role played by the electronic structure is particularly complex. All of the above indicates the need to consider the effect of deep levels in the bulk of the oxide tungsten bronze and on its surface, bordering the electrolyte, on the process of electrochromic coloring.
Keywords: complex tungsten oxides, electrochromic effect, tungsten oxide bronze, thin film, monocrystal.
Khubolov B.M.
Optical properties of amorphous thin films of sodium-tungsten oxide bronzes – page 430
Abstract: The spectral dependences were measured of the optical density of amorphous thin films of sodium-tungsten oxide bronze of the tetragonal structure and the composition Na0,3WO3, condensed on glass substrates, thermostated at temperatures of 373, 473 and 573K, as well as annealed in air vacuum, and electrochromically colored. The optical density D , which is proportional, as is known, to the absorption coefficient, was chosen as the studied optical characteristic. Spectral measurements of films deposited on substrates in the temperature range of 373, 473 and 573K showed the same type of spectral characteristics, with a peak of the exciton absorption in the near ultraviolet. The band of minimum absorption lies in the wavelength range of 400÷460 nm, while that of the impurity absorption is a wide band in the region of 650÷1000 nm with a maximum in the range of 900÷1000 nm. This spectral characteristic determines the blue-blue color of a thin film in transmission. The study of the optical properties of thin films of sodium-tungsten bronzes is an urgent problem.
Keywords: sodium tungsten bronze, thin film, monocrystal, electrochromic effect, optical density, spectral characteristics.
Shebzukhova I.G., Aref`eva L.P.
Influence of polymorphic transformations on anisotropy of the surface energy and the work function of the electron of lithium – page 439
Abstract: On the basis of the electronic-statistical method, a relationship is obtained and the surface energy and the work function of the electron of the faces of lithium crystals are estimated, taking into account the dispersion, polarization, and oscillatory interactions of the atoms of the surface layer. It was assumed that the crystal lattice has no defects. The expressions for the corrections and an analytical relationship between the work function of the electron and the surface energy are modified taking into account the type of the crystal lattice and the orientation of the faces. The work function of the electron and the surface energy of smooth faces are calculated at the limiting temperatures of the existence of polymorphic lithium phases. The influence of polymorphic transformations and temperature on the anisotropy is established. The temperature coefficient of the work function of an electron in a defect-free crystal is positive and amounts to about 0,1–1 meV. The calculation results are in good agreement with the experimental data for polycrystals.
Keywords: work function of an electron, surface energy, lithium, polymorphism.
Shomakhov Z.V., Nalimova S.S., Kalmykov R.M., Aubekerov K., Moshnikov V.A.
Study of the microstructure and composition of tin dioxide layers modified by silver nanoparticles – page 447
Abstract: Tin dioxide layers were synthesized by hydrothermal method from an aqueous solution of SnF2 . Silver nanoparticles were deposited on the surface of the obtained layers by the photoreduction method. The surface morphology of the samples was studied by atomic force microscopy. The size of the silver nanoparticles depends on the concentration of the AgNO3 solution used for the photoreduction reaction. When synthesized from 0,02 M solution with a concentration of, the size of the nanoparticles varies from 10 to 100 nm, when the concentration of the solution is doubled, the size of the nanoparticles is about 100 nm. The surface composition of the layers before and after the deposition of silver nanoparticles was studied using the X-ray photoelectron spectroscopy. It was shown that a layer of the tin dioxide is formed without external inclusions, and metallic silver is deposited. The chemical shift of the peaks of tin and oxygen after the deposition of silver nanoparticles indicates the exchange of electrons between tin and silver. The synthesized layers are of interest for application in the field of semiconductor adsorption gas sensors.
Keywords: tin dioxide, silver nanoparticles, gas sensors, atomic force microscopy, X-ray photoelectron spectroscopy.
2. THE THEORY OF NANOSYSTEMS – page 457
Izmailov V.V., Novoselova M.V.
Correlation-spectral analysis of the topography of engineering surfaces at the nanoscale level – page 457
Abstract: The nanotopography of some typical technical surfaces is investigated and the characteristics of the nanoroughness profile as a random process are experimentally determined – the autocorrelation function and spectral density. It is shown that for the investigated surfaces, their profilograms can be considered as realizations of a random stationary normal ergodic process. A visual check of the process normality was carried out by comparing the experimental values of the profile ordinates with theoretical values obeying the normal distribution, as well as by comparing the frequency polygon with the theoretical probability density function of the normal distribution. Quantitative confirmation of the process normality was carried out using the Kolmogorov goodness-of-fit test. It is shown that at the significance level p=0,05, the hypothesis about the normality of a random process (surface nanoroughness profile) does not contradict the experimental results. The correlation intervals of the considered processes are determined. The form of the autocorrelation functions and the values of the correlation intervals indicate the random nature of the surface profile: in the interval equal to one or two average values of the step of the irregularities of the profile, its ordinates become practically uncorrelated. Spectral density plots indicate that the surface profile can be considered as a wide-band random noise with a predominance of low-frequency components.
Keywords: surface, nanotopography, profile method, random process, normal distribution, autocorrelation function, spectral density, correlation interval.
Kramynin S.P.
Influence of size and pressure on the temperature dependencies of thermodynamic properties of platinum – page 465
Abstract: Based on the parameters of the pair interatomic interaction potential of the Mie-Lennard- Jones for Pt , and using the RP-model of the nanocrystal, the temperature, pressure and size dependencies of the following properties are studied: elastic modulus, thermal expansion coefficient, isobaric heat capacity, and surface energy. The calculation of the equation of state showed good agreement with experiment. The equation of state was calculated along five isotherms: T=300, 1300, 1500 , 1700 , 1900 K. For the first time, calculations of the temperature dependences of the above properties of Pt in the range from 0 to 1500 K along 0 and 50 GPa isobars were performed from a unified standpoint. Calculations of these dependencies were carried out for both macro- and cubic nanocrystals of 306 atoms. It is shown that with an isobaric-isothermal decrease in the nanocrystal size, the values of the elastic modulus and surface energy decrease, while the values of the thermal expansion coefficient and isobaric heat capacity increase over the investigated temperature range.
Keywords: platinum, nanocrystal, size dependencies, equation of state, surface energy.
Kuznetsov Yu.A., Lapushkin M.N.
Calculation of electronic structure of 2D NaAu intermetallic layers – page 475
Abstract: The calculation of the density of states of various thicknesses of the 2D -layers of the intermetallic compound has been carried out. 2D -layers of intermetallic compound NaAu are simulated by supercells NaAu (111) 2×2×2. For a monolayer 2D -layer of an intermetallic compound NaAu the presence of a bandgap with a width of 1,87 eV has been established. An increase in the thickness of the 2D -layers of the intermetallic compound NaAu to two monolayers showed a decrease in the bandgap to 0,81 eV. A further increase in the thickness of the 2D -layers of the intermetallic compound NaAu leads to the disappearance of the band gap, which indicates a semiconductor-metal transition for the 2D -layer of the intermetallic compound NaAu with a thickness of three monolayers. The valence band of the 2D -layer of the intermetallic compound NaAu is formed mainly by Au 5d electrons, with an insignificant contribution from Au 6s and Au 6p electrons. The conduction band of NaAu is formed mainly by Au 6p electrons with an insignificant contribution of electrons Na 3s .
Keywords: electronic structure, intermetallic compounds, 2D -layer, sodium auride.
Malyshkin Yu.A.
Preferential attachment with fitness dependent choice – page 483
Abstract: We study the asymptotic behavior of the maximum degree in the preferential attachment tree model with a choice based on both the degree and fitness of a vertex. The preferential attachment models are natural models for complex networks (like neural networks, etc.) and constructed in the following recursive way. To each vertex is assigned a parameter that is called a fitness of a vertex. We start from two vertices and an edge between them. On each step, we consider a sample with repetition of d vertices, chosen with probabilities proportional to their degrees plus some parameter β>-1. Then we add a new vertex and draw an edge from it to the vertex from the sample with the highest product of fitness and degree. We prove that the maximum degree, dependent on parameters of the model, could exhibit three types of asymptotic behavior: sublinear, linear, and of n / lnn order, where n is the number of edges in the graph.
Keywords: complex networks, random graphs, preferential attachment, power of choice, fitness.
Myasnichenko V.S., Matrenin P.V., Sdobnyakov N.Yu.
Prediction of bonding energy by structural descriptors of metal nanoalloys – page 495
Abstract: The problem of predicting the binding energy for ternary metal nanoparticles and the construction of learning models based on structural descriptors are discussed. Regression dependences of the specific interatomic bond energy were constructed for the ternary Au–Ag–Cu nanosystem. A number of five radial features were used, depending on the pairwise interatomic distance of the nanoparticle structure descriptors. For a more correct assessment of the accuracy, cross-validation was applied, then the results obtained on the validation parts of the sample were averaged. The resulting model limitedly predicts the value of the specific interatomic binding energy within a group of data for nanoparticles of the same composition. For the entire sample the average error in modulus is 14 %. In this case, the model almost accurately determines the composition of a nanoparticle of several variants. The largest value of the coefficient of determination in the entire sample was obtained using an ensemble random forest algorithm. A negative correlation was found between the binding energy of the nanoalloy and the position of the first peak of the radial distribution function for copper atoms.
Keywords: machine learning, radial distribution function, structural descriptor, bond energy, ternary alloy..
Samsonov V.M., Talyzin I.V., Puitov V.V., Vasilyev S.A.
To the problem of applicability of the Tamman temperature concept to nanosized objects: to the 160th anniversary of Gustav Tamman – page 503
Abstract: The introduction provides a brief critical review of the available definitions and interpretations of the Tamman temperature, usually defined as TT(∞)=0,5Tm(∞), and of the Hüttig temperature TH(∞)=0,5Tm(∞) where Tm(∞) is the macroscopic value of the melting point of the material. For a nanoparticle we propose to replace in the above relations Tm(∞) by the melting temperature of the small object Tm , i.e. to define TT as 0,5Tm and TH as 0,3Tm. In our molecular dynamics experiments on Au nanoparticles, carried out using the LAMMPS program, we found that at the temperature T=TT, in both the central part of the fcc nanoparticle (the core) and in its surface layer (the shell), some local species of a quasicrystalline structure appear which are alternately identified either as crystalline or as non-crystalline by the OVITO program. However, contrary to opinion of E. Rukenstein (1984), at T=TT, a liquid layer on the surface of the crystalline nanoparticle is not formed yet. However, a liquid-like layer was gradually developed in the course of the further temperature elevation. At the same time, in our molecular dynamics experiments we did not reveal any manifestation of the Hüttig temperature TH in the structure of crystalline Au nanoparticles reproduced in our molecular dynamics experiments. It is also of interest that in our molecular dynamics experiments the nanoparticle sintering took place not only above the Tammann temperature but below it as well.
Keywords: Tamman temperature, Hüttig temperature, metal nanoparticles, surface melting, sintering, molecular dynamics.
Skobin M.I., Feofanova M.A., Kryukov T.V.
Theoretical and experimental study of macromolecular nanostructures based on heparin and lanthanoids – page 513
Abstract: Study of synthetic and natural materials suitable for the creation of nanocarriers and their modification will provide a breakthrough in the treatment of many diseases. Glycosaminoglycans (heparin and its derivatives) are a good choice for creating nanocarriers due to their unique biological and physicochemical properties. The complexation of Pr (III), Sm (III), Eu (III) with heparin anions was studied by potentiometric titration at 37 °C and an ionic strength of 0,15 M NaCl . Significant forms and chemical equilibria were determined using the NewDALSFEK program. In the pH range from 2,7 to 5 , a complex of the type {[LnHep]}n, is formed, where Hep3- is a monomeric unit of the heparin macromolecule. Data on the stability of nanocompositions were obtained: lgβ [PrHep]=4,27±0,04, lgβ [SmHep]=4,28±0,04, lgβ [EuHep]=4,28±0,03. The M06-HF method in combination with the CSDZ+* basic set was used to perform quantum chemical modeling of the complexes.
Keywords: heparin, lanthanides, stability constant, quantum chemical calculation, anticoagulants, Hartree-Fock method.
Yurov V.M., Goncharenko V.I., Oleshko V.S., Guchenko S.A.
Surface layer thickness and anisotropy of the surface energy of cubic ruthenium crystals – page 522
Abstract: The paper deals with the anisotropy of the surface layer and the anisotropy of the free surface energy of cubic ruthenium crystals. This consideration is based on an empirical model of atomically smooth crystals, the thickness of the surface layer of which depends on single fundamental parameter – the atomic volume of an element. Calculations of ruthenium crystals showed that the thickness of the surface layer of ruthenium crystals in all directions does not exceed d(I)<10 nm and they represent a nanostructure. Crystals of ruthenium aluminum, ruthenium hafnium, ruthenium titanium, ruthenium zirconium have σ>3 J/m2 in the (100) direction. We have considered the problem of gas diffusion in a nanometer ruthenium plate. In contrast to the classical problem, a logarithmic term appears in the resulting equation. This leads to divergence at the origin. Therefore, the boundary conditions must be specified not at x=0, but at x=d(0) – the de Broglie wavelength of electrons. Only in this case the classical diffusion equations are meaningful. It is also important that, according to the obtained equation, the diffusion of the nanoplate depends both on the material of the plate through the diffusion coefficient of the bulk sample and on the size factor. In the classical case, there is no such dependence. Various models have been proposed to describe phase transitions in nanostructures, among which we can mention the Landau mean field method, in which the order parameter is used. We will use Landau’s theory, replacing the temperature T with the coordinate h .
Keywords: surface layer, nanostructure, surface energy, atomic volume, size effect, ruthenium.
3. FIRST PRINCIPLES AND ATOMISTIC MODELING – page 534
Alekseev V.G., Baburkin P.O., Tung S., Komarov P.V.
Computer simulation of π – π interactions of tetrathiophene molecules – page 534
Abstract: The properties of the supramolecular organization of conjugated polymers strongly affect the mobility of charge carriers and, consequently, the properties of produced electronic devices based on them. Therefore, it is important to learn how to build computational models capable of reproducing the structure of such polymers with the highest possible accuracy. One of the main driving forces of the self-assembly of supramolecular structures in conjugated polymers is π–π interaction. Taking it into account is a rather difficult task, especially when constructing mesoscale models. In this work, we use the electron density functional theory to develop a methodology for calculating conjugated polymers taking into account π–π interaction. The geometric characteristics of stacks of four tetra thiophene molecules were studied. The performed calculations show that the use of the M06-2X-D3 functional makes it possible to correctly model the interactions of oligothiophene molecules and the structure of the resulting aggregates, while semiempirical calculations by the PM7 method of conjugated polymers are suitable only for rapid preliminary optimization of models. The tested calculation technique is of great importance for the parametrization of mesoscale modeling schemes.
Keywords: organic solar cells, organic polymers, thiophenes, quantum chemical calculations, π–π stacking interaction.
Belenkov M.E., Chernov V.M.
Simulation of polymorphic varieties of hexagonal graphene functionalized by hydroxyl groups – page 541
Abstract: Computer simulation of the crystal and electronic structure of hexagonal graphene layers, on the surface of which hydroxyl groups, chemically adsorbed, was performed by the density functional theory method. As a result of calculations, the possibility of the stable existence of five structural varieties of COH–L6 layers was established. The layer density varies from 1,62 to 1,72 mg/m2. The length of the hydrogen-oxygen bond varies in the range from 1,046 to 1,079 Å, and the carbon-oxygen bond-from 1,455 to 1,465 Å. The orientation of the O–H bonds relative to the surface of the layers can vary depending on the choice of the unit cell of the layer. Layer COH–L6–T4 has the minimum sublimation energy equal to 18,69 eV/(COH), and layer COH–L6–T1 has the maximum sublimation energy 18,93 eV/(COH). The electronic structure of all COH layers is characterized by the presence of a direct band gap at the Fermi energy level, varying in the range from 3,02 to 4,56 eV.
Keywords: graphene, chemical adsorption, hydroxyl groups, ab initio calculations, crystal structure, electronic properties, polymorphism.
Belyakova R.M., Kurbanova E.D., Polukhin V.A.
Analysis of Nb – Ni and V – Ni based membrane characteristics – page 552
Abstract: To obtain ultrapure hydrogen by membrane technology, instead of expensive membranes made of Pd alloys, cheaper ones based on metals ( Nb–Ni) and (V–Ni) are considered. Due to alloying of these Ti alloys, the performance of the membranes increased – diffusion and permeability of hydrogen, wear resistance and thermal stability, exceeding the Pd alloys. For crystalline analogs, the problem was also solved by increasing the Ti concentration with the formation of eutectic phases in ternary alloy compositions (Nb85-xTixNi15 and V85-xTixNi15). Hydrogen accumulated in membrane matrices forms specific polyhedral eutectic TСР hydrides up to phase transitions, and upon cooling from 673 to 303К under conditions of thermal expansion from 473 to 673К, it increases the temperature of β-hydride formation and forms NiTi and NiTi2 compounds, which stabilize and protect nano- and crystalline membranes from brittle destruction.
Keywords: Ti alloying, ternary alloys Nb–Ni–Ti, V–Ni–Ti, hydrogenation, absorption, diffusion, hydrogen permeability, phase formation, Me–H hydrides, embrittlement, duplex matrix microstructure.
Malyshev M.D., Tung S-H., Komarov P.V.
Molecular-dynamic simulation of mixtures of modified fullerenes and 1,8-octandithiol – page 562
Abstract: In this work, we report on the results of comparative atomistic modeling of two systems containing functionalized fullerenes of phenyl- C61 -butyric acid methyl ester (PC61BM ) and phenyl- C71 -butyric acid (PC71BM) in the presence of a high-boiling solvent 8,1 -octanedithiol (ODT ). The calculations were performed by full atomistic molecular dynamics with using LAMMPS software package. A fundamental difference in the packaging of PC61BM and PC71BM molecules was detected. In the case of systems with PC61BM , there is a tendency towards gradual separation of the solvent and fullerenes. At the same time, in samples with PC71BM, there is a tendency to the formation of stable three-dimensional network structures formed by two interpenetrating phases: fullerenes and ODT molecules. In order to check the scalability of the observed structural ordering for the mixture of PC71BM with ODT , an additional simulation was performed in a cell with doubled edge size. In this case, we also observe the formation of bicontinual structures from fullerenes and the solvent.
Keywords: atomistic molecular dynamics, modified fullerenes, high-boiling solvent, networks, bicontinual structures.
Myasnichenko V.S., Eshov P.M., Savina K.G., Veselov A.D., Bogdanov S.S., Sdobnyakov N.Yu.
Regularities of structure formation in bimetallic nanoparticles with different crystallization temperatures – page 568
Abstract: In this work, of the structure formation was investigated using Au–Ag, Ti–Al, Ti–V bimetallic nanoparticles as the patterns. These bimetallic nanoparticles have different atomic size mismatches and different crystallization temperatures. A series of molecular dynamics experiments was carried out. Based on their results, the final configurations with the lowest energy were analyzed and the concentration dependences of the mixing energy were obtained. An analysis of the concentration dependences of the mixing energy makes it possible to predict the compositions and sizes of bimetallic nanoparticles, which can exhibit instability, such as for Ti–V bimetallic nanoparticles. The asymmetry of individual concentration dependences of the mixing energy is evidence of specific structural transformations characteristic for the given composition and size. It has been established that structural segregation is characteristic for Au–Ag, Ti–Al bimetallic nanoparticles and it is actively manifested at low concentrations of a more low-melting component. The competing phases in this case are fcc and hcp phases. In addition, for the average sizes considered in the article, the dependence of the crystallization temperature on the composition of bimetallic nanoparticles was investigated.
Keywords: molecular dynamics method, tight-binding potential, bimetallic nanoparticles, structure formation, crystallization temperature, mixing energy, stability.
Pan’kin N.A.
Change in the structure of titanium nanoclusters under thermal exposure: molecular dynamic simulation – page 580
Abstract: Investigation of the structure of nanoclusters at different temperatures is an urgent task of modern materials science. This fact is due to the prospect of their application in the creation of materials with unique physical, mechanical, chemical and operational properties. Computer simulation was carried out by the method of classical molecular dynamics in the LAMMPS software package. To describe the interatomic interaction in the cluster, a modification of the Finnis-Sinclair many-body potential was used. The structure of titanium nanoclusters of various sizes has been studied. They are obtained at various cooling rates from the liquid state. An increase in the cooling rate leads to the formation of a subblock structure and an increase in the number of atoms with a disordered environment. They are due to the fact that high cooling rates impede the equilibrium process of rearrangement of the atomic structure with the formation of long-range order. No regions with an icosahedral structure were found. It is shown that the crystallization temperature and binding energy decrease with decreasing nanocluster size. An increase in the cooling rate increases the temperature difference between the start and end points of crystallization, respectively. The simulation results indicate a less pronounced dimensional dependence of the crystallization temperature – its estimated value for a macroscopic system (810K) is much lower than the value for bulk titanium (1940 K).
Keywords: nanocluster, binding energy, crystallization temperature, cooling rate, structure, molecular dynamics method.
Ryzhkova D.A., Gafner S.L., Gafner Yu.Ya.
Role of «magic» HCP numbers in stability of the internal structure of Ag89 and Ag153 nanoclusters – page 593
Abstract: Currently, silver is actively used in microelectronics, mainly due to its high electrical and thermal conductivity. Taking into account the processes of interaction between a metal and a light wave (plasmon effects) gives completely new technical applications of silver. These applications are made possible by the strong interaction between incident light and free electrons in nanostructures. By now, it has already become clear that the size, shape, and structure of nanoparticles determine their plasmon properties, including resonance frequencies. Therefore, by adjusting the size, appearance of the metal nanostructure and its internal structure, it is possible to control light with a very high degree of accuracy. In this work, the boundaries of thermal stability of various initial structural phases in small silver clusters with the number of atoms corresponding to the «magic» numbers of the hcp structure were studied by the molecular dynamics method using the modified tight-binding potential TB-SMA (second moment approximation of tight-binding). It was shown that the nature of thermally induced structural transitions in the groups of nanoclusters under study differs sharply. This fact can make it possible to create small silver clusters with the required internal structure.
Keywords: nanoclusters, silver, computer simulation, «magic» numbers, hcp structure, tight-binding.
Ryzhkova D.A., Gafner S.L., Gafner Yu.Ya.
Structural stability of Ag55 and Ag147 nanoclusters with a change in the initial morphology – page 604
Abstract: This article provides a comparative analysis of thermally induced structural transitions in silver nanoclusters with a change in their initial morphology. The study was executed by the molecular dynamics method using the modified TB-SMA (second moment approximation of tight-binding) tight binding potential. The number of atoms in nanoclusters corresponds to the icosahedral structure «magic» numbers. It is shown that for nanoclusters with the initial FCC configuration, the Ih modification is formed either at the stage of preliminary thermal relaxation or during further heating. For nanoclusters with an initial amorphous morphology, the nature of structural transitions undergoes significant changes. For example, the formed Ih modification is more stable at high temperatures and the melting point of nanoclusters shifts by more than 100 K. This effect is due to a smoother change in the specific potential energy of the nanocluster in comparison with the case when a stable Ih configuration is formed at low temperatures. The data obtained can be used in processes to create silver nanoclusters with the required internal structure.
Keywords: structure stability, nanoclusters, silver, computer simulation, structure, tight-binding.
Sdobnyakov N.Yu., Bogdanov S.S., Veselov A.D., Savina K.G., Nepsha N.I., Kolosov A.Yu., Myasnichenko V.S.
Influence of the size effect on the regularities of the structure formation in bimetallic Au-Co nanoparticles – page 612
Abstract: This work studied bimetallic Au–Co nanoparticles of three stoichiometric compositions of various sizes by the molecular dynamics method using the tight-binding potential. The regularities of structure formation are established, their characteristic features are described. In particular, in compositions with 50at% and 75at% Au content, multiple small nuclei of local icosahedral symmetry are formed. Crystalline phases prevail only in the Co -25 at% Au composition with an increase in the particle size. Compositions are revealed in which the internal symmetry of a nanoparticle is determined by the presence of one icosahedron or a superstructure of several icosahedrons. The concentration dependences of the mixing energy of a bimetallic Au–Co nanoparticle are calculated. It is shown that there are concentrations of compositions at which bimetallic nanoalloys can exhibit instability in a certain size range. Crystallization temperatures were determined using the caloric curves of the potential part of the internal energy. It was found that the crystallization temperature demonstrates a moderate or significant, depending on the composition as well as growth with an increase in the size of bimetallic Au–Co nanoparticles.
Keywords: molecular dynamics method, bimetallic nanoparticles, cobalt, gold, size mismatch, structure formation, stability, crystallization temperature, mixing energy.
Sokolov D.N., Sdobnyakov N.Yu., Savina K.G., Kolosov A.Yu., Myasnichenko V.S.
New opportunities for high-performance simulations of nanosystem using Metropolis software – page 624
Abstract: The architecture and software Metropolis for computer simulation by the Monte Carlo method, as well as its modifications, are described. The tight-binding potential that does not exclude the possibility of using other modifications of many-body potentials. In comparison with previous software implementations of the Monte Carlo method, this modification has increased the rate of calculations by 700 times for a selected nanoparticle size. The data on the convergence of the results of modeling by the Monte Carlo method are presented on the example of the melting point. The developed software package is constantly tested for calculations of various mono- and multicomponent nanoparticles and nanosystems. The results obtained show fairly good agreement with other numerical methods, primarily molecular dynamics, and real experiment. Further development of the software package and its performance indicators are planned to be improved using parallelization of computations and the use of computing technology on graphics processors CUDA.
Keywords: computer experiment, Monte Carlo method, hybrid methods, nanoparticles, Metropolis API interface.
Chepkasov I.V.
Study of potassium intercalation in the graphene / MoS2 structure – page 639
Abstract: Using modern ab-initio calculations, in this work, we systematically studied the intercalation of potassium atoms into a hybrid two-layer graphene/MoS2 structure. In the course of the study, concentrations of potassium atoms were determined at which the formation energy is negative. So, in particular, when the concentration of potassium atoms (in relation to molybdenum atoms) is not more than x=0,43, formation of a layer of potassium atoms between the graphene/MoS2 layers is energetically favorable. Beginning with the concentration of potassium atoms x>0,75, an increase in the distance between the graphene and MoS2 layers is observed, which further leads to destruction of the structure. Calculation of charges showed that a potassium atom at low concentrations gives up about 0,8–0,85 electrons, 0,35 of which flow on carbon atoms, and 0,4–0,5 to molybdenum disulfide. Calculation of the difference in electron densities showed that the bond between the layers of graphene, molybdenum and potassium disulfide has a covalent nature.
Keywords: potassium-ion batteries, anodes, intercalation, transition metal dichalcogenides, graphene, density functional theory.
4. PHYSICAL AND CHEMICAL BASES OF NANOTECHNOLOGIES – page 646
Bakhvalova E.S., Bykov A.V., Nikoshvili L.Zh., Kiwi-Minsker L.
Influence of halogen nature on the adsorption ability of aryl halides on palladium clusters – page 646
Abstract: In this paper, the density functional theory calculations were carried out in order to find the adsorption energies of a benzene ring on small Pd0 clusters consisting of four or nine atoms. The adsorption of benzene on palladium clusters was found to result in a noticeable energy gain of the system: –146 kJ/mol in the case of Pd4, and –117 kJ/mol in the case of Pd9 . The adsorption energies of chloro-, bromo- and iodoanisole on Pd4⚹C6H6 were also calculated. The adsorption of iodoanisole was characterized by the highest energy gain of the system (–278 kJ/mol) and occurred dissociatively without activation, that fundamentally distinguished it from chloro- and bromoanisole. The data obtained can be used to explain the differences in the behavior of catalysts based on hyper- cross-linked polystyrene in cross-coupling reactions of various aryl halides and phenylboronic acid, and also the fact that aryl iodides can favor the formation of homogeneous forms of palladium.
Keywords: palladium, clusters, aryl halides, Suzuki cross-coupling, density functional theory.
Bogdanova E.A., Skachkov V.M., Giniyatullin I.M., Pereverzev D.I., Nefedova K.V.
Preparation of biocomposites based on nanoscale hydroxyapatite with zirconium and silicon oxides – page 655
Abstract: The article discusses the possibility of obtaining a hardened composite material with a porous structure based on nanostructured hydroxyapatite (HAP) synthesized by precipitation from a solution. The new material was obtained by the mechanochemical synthesis of HAP with reinforcing additives of zirconium dioxide and silicic acid. The synthesized samples are certified using modern physico- chemical methods of analysis. The influence of the qualitative and quantitative composition of the composite on the sintering processes, porosity, strength characteristics, the degree of dispersion and morphology of the studied samples is shown. It has been experimentally established that the sample has the maximum strength characteristics and a constant composition of Ca10(PO4)6(OH)2–15%SiO2·nH2O–5%ZrO2. The composite material has a dense uniform structure with a high degree of crystallinity, with a developed porosity, is a promising material for further research in order to introduce it into medical practice. A patent application has been filed for the developed composite material.
Keywords: hydroxyapatite, zirconium oxide, silicon oxide, composite biomaterials, crystallinity, microhardness.
Bogdanova E.A., Skachkov V.M.
Promising composite materials based on nanoscale apatite with gelatin as a binding agent – page 664
Abstract: Nanoscale hydroxyapatite and fluorapatite powders were synthesized by precipitation from solutions. Food gelatin is used as a binder. This composition has a high adhesion on materials of different nature and porosity. Porous films and granules with a developed specific surface area were also obtained. Their microstructures are considered. The possibility of using a colloidal suspension and an aqueous suspension of crystalline apatite in combination with a gelatin solution as a bioactive material, both for creating coatings and obtaining granules, has been studied. It is established that the use of apatite powder together with gelatin can significantly reduce the time of formation of a bioactive coating and significantly increase its adhesive strength. The obtained apatite granules are compared in size depending on the concentration of gelatin in an aqueous solution. Patent applications have been filed for the developed bioactive coatings and granular material based on nanoscale apatite with a binding agent.
Keywords: hydroxyapatite, fluorsubstituted hydroxyapatite, gelatin, collagen, biomaterial, bioactive coatings, adhesion, granules.
Zernitsa D.A., Shepelevich V.G.
Study of the structure and properties of lead-free rapidly solidified zinc-based alloys during a heat treatment – page 672
Abstract: The results of studies of the effect of ultrahigh melt cooling rates, equal to at least 105 K/s, on the properties of rapidly solidified alloys of the Zn–Sn system are presented. The upper region of the foil, in contact with the crystallizer during solidification, had more dispersed particles of the second phase, and as the distance from the upper layers increased, the particle sizes increased. At room temperature, the decomposition of a supersaturated solid solution proceeds with the release of dispersed particles. Additional heat treatment leads to the coarsening of the particles of the second phase, and helps to reduce the microhardness. Rapidly solidified foils with a maximum zinc concentration are characterized by the presence of a (0001) texture, which weakens as the tin content in zinc increases, and upon alloying up to 30 wt. % Sn is rearranged to (1010) texture. Heat treatment up to 160 °C does not change the texture.
Keywords: rapidly solidification, lead-free solders, Zn–Sn alloy, microhardness, unit cell, isochronous annealing, decomposition, solid solution.
Ivanov D.V., Anofriev V.A., Koshelev V.A., Antonov A.S., Vasilyev S.A., Sdobnyakov N.Yu.
Simulation of layer by layer growth of fractal metal Pt-Rh films – page 682
Abstract: In this work, the molecular dynamics method and the tight-binding potential are used to simulate the process of molecular beam epitaxy in order to determine the regularities in the formation of fractal platinum metal films on the rhodium surface. The possibility of formation of fractal structures both in island platinum films on the rhodium surface and in a continuous film has been established. The parameters of the computer experiment, which determine the transition from individual island films to a continuous film in the indicated system, have been established. Using various software products Gwyddion and Image Analysis, as well as our own software FractalSurface, the range of changes in the fractal dimension has been analyzed under various conditions of a molecular dynamics experiment by the method of cube counting. The obtained values of the fractal dimension are generally in acceptable agreement with each other; however, there is a number of exceptions, which are discussed in more detail. A comparative analysis of the results obtained allows one to formulate recommendations for the methodology for creating, adjusting and precision control when «growing» structures with a given surface morphology.
Keywords: molecular beam epitaxy, molecular dynamics modeling, tight-binding potential, fractal dimension, cube counting, platinum, rhodium, imaging software.
Ivanov Yu.F., Abzaev Yu.A., Klopotov A.A., Prokopenko N.A., Tolkachev O.S., Nikitin P.Yu., Shugurov V.V., Teresov A.D., Petyukevich M.S.
Features of the structural phase state of a film based on a high-entropy AlNbTiZrСu alloy synthesized by deposition of a multi-element metal plasma – page 693
Abstract: This paper presents the results of structural studies of films with a thickness of up to 5 microns of high-entropy alloys of the AlNbTiZrCu system. The films were synthesized on metal and cermet substrates by deposition of a multielement metal plasma created by electric arc plasma assisted simultaneous independent sputtering of several cathodes. It is shown that the films are a layered material and have an amorphous-crystalline structure. It was found that irradiation of films with a pulsed electron beam (18 keV, 20 J/cm2, 50 μs, 3 imp., 0,3 s-1) is accompanied by crystallization of the material. It is shown that the resulting films are dominated by the compound of the AlNbTiZr composition with the lattice parameter of 0,32344 nm. On the basis of theoretical calculations, the structural data of the crystal AlTi0,86Zr0,95Nb lattice were obtained, mechanical and thermodynamic characteristics of this compound were determined.
Keywords: high-entropy alloy, low-pressure gas discharge plasma, film/substrate system, pulsed electron beam, phase composition, structure.
Klychkov N.A., Simakov V.V., Sinev I.V., Timoshenko D.A.
Dynamics of response of a sensor based on a nanostructured tin dioxide layer exposed to the isopropanol vapors – page 708
Abstract: Nanostructured gas-sensitive tin dioxide films have been synthesized by sol-gel technology. A conductivity vs temperature dependence of a gas sensor into atmosphere of synthetic air has been investigated. A response vs temperature dependence of a gas sensor into atmosphere of isopropanol vapors with various concentrations has been investigated. Local minimum on the temperature dependence of the tin dioxide film conductivity in clean air atmosphere were observed. A decrease in conductivity with increase temperature in the range of 300…350 °C can be associated with a dissociation molecular form of the adsorbed oxygen. At temperatures above 350 °C, conductivity increases because of desorption of the atomic form of the adsorbed oxygen on the surface of gas-sensitive tin dioxide film. The greatest response value is achieved at a sensor temperature equal to 350 °C. It is proposed that the reason is a domination of the atomic form of the chemisorbed oxygen on the surface. The analysis of response time vs concentration and response time vs temperature of gas sensor has been carried out. Sensor response time decreases monotonically with increase admixture substance in gas-probes, apparently because of increase in adsorption rate admixture particles on the surface of gas-sensitive film. It was found that the dependence of the response time on the operating temperature has an Arrhenius form. This may be associated with thermally activated adsorption-desorption processes and heterogeneous chemical reactions on the surface of sensor active layer.
Keywords: sol-gel method, nanostructured films, tin dioxide, gas sensor response time.
Kovtun A.I., Mysyura A.G.
Physico-chemical properties of a nanocomposite hydrogel coating on a textile carrier for the wound treatment – page 717
Abstract: Nanotechnologies using biopolymers are widely used in biomedical applications. In this work, nanocomposite hydrogels based on natural (chitosan, carboxymethylcellulose) and synthetic (polyvinyl alcohol) polymers with silver nanoparticles for application to a textile carrier have been developed. Carboxymethylcellulose dialdehyde and boric acid were used as crosslinking reagents in the creation of hydrogels. Physicochemical properties (sorption capacity in unilateral contact with the model medium, degree of swelling, vapor permeability, capillarity) of hydrogel coatings on a textile carrier, and the kinetics of the drugs release (lidocaine, dioxidine) included in the hydrogels were determined. It is shown that materials with a two-layer coating are characterized by higher sorption properties relative to saline and a longer release of drugs than materials with a single-layer coating. The release of drugs from the two-layer coatings occurs in two stages with a maximum release within two days. The obtained textile materials with a film nanocomposite hydrogel coating can be used as dressings in the treatment of wounds.
Keywords: hydrogel, silver nanoparticles, textile, chitosan, polyvinyl alcohol, carboxymethylcellulose dialdehyde, drug release kinetics, dressing, wound treatment.
Kurbanova E.D., Belyakova R.M., Polukhin V.A.
Specific structure of effective membrane alloys based on niobium, vanadium and zirconium – page 728
Abstract: With unique mechanical and functional properties, amorphous, nanocrystalline and matrix duplex microstructure membrane alloys based on group V elements actively contribute to the development of hydrogen energy. There are still not completely resolved problems for these new alloys – their low thermal stability, insufficient mechanical strength (plasticity, hardness), and intermetallic and hydride embrittlement. For effective use, alloys with a triple composition are being developed – which, in addition to the elements of group V, also include nickel and titanium as alloying metals. Not only amorphous and nanocrystalline alloys are obtained that are applicable in electronics and power engineering, as well as membrane alloys with a duplex matrix structure that combines amorphous, nano- and quasicrystalline dendritic-hardening phases strengthening the amorphous matrix. In specialized membrane ternary alloys, NiTi and NiTi2 compounds are formed, which stabilize and protect nano- and crystalline membranes from brittle destruction. It has been found that the intense formation of hydrides in these alternative membrane alloys is as undesirable as for palladium-based compounds. The alloys under consideration actually make it possible to obtain high-purity gaseous hydrogen using new compositions instead of expensive membranes based on Pd–Au/Ag/Cu alloys.
Keywords: amorphous and nanocrystalline alloys, nickel, titanium, zirconium, niobium, structurization, membrane gas separation, hydrogen purification, solubility, hydrogen permeability, accumulation, thermal stability, fragility, crystallization, modeling, diffusion, nanophases, Me–H hydrides, embrittlement, duplex matrix microstructure.
Malyshkina O.V., Shishkov G.S., Ivanova A.I.
Optimization of technology for producing a composite based on barium ferrite and barium titanate – page 740
Abstract: It is shown in the work that as a result of sintering of composite samples of barium titanate (80 vol. %) – barium ferrite ( 20 vol. %) in a porcelain crucible at a temperature of 1300 °C, a eutectic appears. As a result of comparing the properties of the samples obtained at different sintering temperatures, it was found that the samples sintered at 1250 °C have optimal properties. The structure and dielectric properties of barium titanate ceramic samples and barium titanate (80 vol. %) – barium ferrite ( 20 vol. %) composite sintered at a temperature of 1250 °C are compared. It has been shown that the addition of 20% barium ferrite to the composition of barium titanate increases the dielectric constant, pyroelectric coefficient, and piezoelectric modulus d33 of the composite of 1,5–2 times compared to barium titanate ceramics, while the value of the piezoelectric modulus d31 remains unchanged. The introduction of 20 % barium ferrite into the barium titanate ceramics is sufficient for the resulting composite to have magnetic characteristics corresponding to pure barium ferrite.
Keywords: multiferroic, barium ferrite, barium titanate, magneto-electric composite, piezoelectric ceramic structure.
Masloboeva S.M.
Analysis of methods for synthesis of a boron-doped lithium niobate charge used for growing single crystals – page 750
Abstract: Known methods of a boron doped lithium niobate charge synthesis were analyzed. Such a charge is applied for the growth by Czochralski of single crystals with high optical quality. Homogeneous doping (the charge is obtained from precursor Nb2O5 : B and Li2CO3 ) was compared with solid phase doping (the charge is obtained from the mixture Li2CO3 : Nb2O5 : H3BO3). Homogeneous doping was determined to help produce LiNbO3 : B crystals with a more uniform distribution of a boron dopant, boron distributes more uniform in the melt volume; technological regimes established during crystal growth become easier. For the first time the paper considers liquidphase charge synthesis method; the method excludes the stage of annealing of homogenized mixture of niobium pentoxide and lithium carbonate. Results are crucial for the choice of technology at growing of boron doped lithium niobate crystals for exact areas of technics.
Keywords: lithium niobate, charge synthesis, single crystal, doping, boron, optical quality.
Ponomareva A.A., Sitnikova V.E., Tсoi K.A.
Formation of sol-gel catalytic coatings to improve the ecological parameters of intermetallic porous burners – page 760
Abstract: The environmental parameters of power equipment are important in terms of minimizing the negative impact on the environment. Intermetallic infrared porous flameless burners are a new generation of burners with improved performance. Gas burners are among the most efficient devices for direct conversion of combustion heat into infrared energy. Despite the improved environmental characteristics of infrared porous burners compared to traditional burners, during operation they can emit unwanted and hazardous combustion products of gas mixtures (or other fuels), especially during transient and high-power modes. In this work, catalytic coatings based on cerium-based oxide systems with a small addition of silicon oxides were obtained. The deposition of the catalytic material on porous intermetallic substrates was controlled using the gravimetric method, optical analysis system, and scanning electron microscopy, and its chemical structure was investigated using IR spectroscopy. The uniform distribution of the coating over the substrate surface and the correspondence of the IR peaks with the chemical composition of the synthesized systems were detected.
Keywords: catalytic coatings, metal oxide structures, porous burners, sol-gel technology, infrared spectroscopy.
Pravilnikova T.I., Golovanova O.A.
Precipitation of calcium phosphates from a model blood plasma solution on steel grade 12X18N10T – page 769
Abstract: The paper presents a study of the processes of precipitation of mineral-organic formations in a model solution of blood plasma in the presence of additives of albumin, glycine, glucose, glutamic and lactic acids. The phase composition of the samples was studied by the X-ray diffraction analysis. Photos were taken to measure the surface area of the sample with modified calcium phosphate. The solid phase coating areas were highlighted in the photos and the degree of coating of steel samples was calculated using the ToupView software. The deposition of the crystal phase occurs on all the studied samples. The differences are in the distribution of crystals on the surface of the plate. The additive albumin inhibits the deposition of hydroxyapatite on the studied samples. It is shown, that additions of glucose, glutamic and lactic acids catalyze the process of hydroxylapatite deposition on the surface of a steel sample. As a percentage of the total area of the image, the largest amount of precipitated hydroxylapatite powder is observed in samples with the addition of glucose.
Keywords: mineral-organic formations, blood plasma, calcifications, crystallization, hydroxylapatite, precipitation, steel grade 12X18N10T.
Raksha E.V., Glazunova V.A., Oskolkova O.N., Sukhov P.V., Volkova G.K., Davydova A.A., Berestneva Yu.V., Savoskin M.V.
Carbon nanoparticles based on thermally expanded graphite: effect of the TEG obtaining route on the particles morphology – page 777
Abstract: The paper presents the investigation results of the morphology of carbon nanoparticles formed during liquid-phase exfoliation of thermally expanded graphite in tert-butanol. The thermally expanded graphite used in this work was obtained by thermal expansion of graphite nitrate with acetic and formic acids in the thermal shock mode at 500 °C and 900 °C. Initial cointercalate was shown by powder X-ray diffraction analysis to be the mixture of the IInd and the IVth stage intercalation compounds. It has been established by transmission electron microscopy that dispersions of carbon nanoparticles formed during the exfoliation of thermally expanded graphite in tert-butanol via sonication contain mainly few-layer graphenes, the planar dimensions of which reach 8 μm. The influence of the conditions for thermally expanded graphite obtaining on the morphology of resulting carbon nanoparticles is discussed. Dispersions based on thermally expanded graphite obtained at a lower temperature, in addition to few-layer graphenes, also contain a significant amount of amorphous carbon particles with planar sizes up to 100 nm.
Keywords: few-layer graphenes, liquid-phase exfoliation, graphite nitrate, cointercalation.
Skachkov V.M.
Change in properties of diffusion-hardening solder in dependence on the composition of the liquid metal component – page 788
Abstract: The article discusses the change in the properties of diffusion-hardening solder in dependence on the composition of the liquid metal component based on low-melting gallium alloys: gallium-tin, gallium-indium-tin and gallium-tin-zinc when interacting with the Spherical copper-tin alloy powder (SCTAP5) subjected to low-temperature (125°С) and high-temperature (500°С) heat treatment. The mechanical properties were evaluated by measuring the microhardness, and the thermal properties were studied by differential thermal analysis. Heat treatment at high temperatures promotes the transition of the solder to an equilibrium state, with a significant increase in hardness. The thermal effects of heat treatment of diffusion-hardening solders are calculated and compared. The phases formed as a result of hardening are determined by X-ray phase analysis. It is shown that different phases and nanoscale intermetallic compounds are formed at different processing temperatures. The improvement of the mechanical properties of diffusion-hardening solder in the presence of zinc dissolved in a gallium liquid alloy has been experimentally proved.
Keywords: composite diffusion-hardening solders, exothermic effects, properties, microhardness, differential thermal analysis, X-ray phase analysis.
Timoshenko D.A., Sinev I.V., Simakov V.V., Klychkov N.A.
Recognition of gas-air mixtures by a single gas sensor based on the tin dioxide nanowhiskers – page 796
Abstract: Tin dioxide nanowhiskers were grown by physical vapor deposition and transferred to the contact system by the frozen drop method. The sensors demonstrate gas-sensitivity. Exposing sensors to the atmosphere contained vapors of reducing-gases leads to an increasing of their conductivity. A long-term drift of the sensor conductivity during reducing-gas exposition was shown. A sensitivity response vs concentration for ethanol, acetone, and propanol- 2 vapors at temperature 300 °C was investigated. Desorption energies of the particles and the positions of the donor levels induced by adsorption of reducing gases particles were calculated by analysis of the conductivity vs concentration dependence. The calculated parameters had a significantly smaller time drift in comparison with the conductivity. Using of these parameters makes possible to recognize gas-air mixtures: classify the each of three studied samples to one of classes.
Keywords: whisker nanocrystals, tin dioxide, gas detection, semiconductor gas sensor, gas sensitivity.
Fomin A.I., Pan’kin N.A.
Phase composition, substructure and residual macrostresses in the surface layer of a tape obtained by electric contact welding – page 802
Abstract: The surface layer of DI50-2 cast iron after its processing by electric contact welding has been investigated by methods of X-ray diffraction and electron microscopy. A 50HVA steel strip was used as a filler material. Processing technologies were used with the creation of an intermediate layer of nickel powder PC-12N-01 and without it. Results on phase composition, substructure and residual stresses are obtained. The system under study consists of α–Fe and γ–Fe phases. Substructure parameters (microstrain and block refinement) have the same values for different modes of electrical contact welding. Residual stresses are of a tensile nature and decrease when an intermediate layer of nickel powder material is created. The main mechanism of their formation is thermal effects on the material processed by electrocontact welding. Cracks may form after electrical contact welding of the tape. They are oriented mainly parallel to the surface to be treated and are due to the presence of a large temperature gradient.
Keywords: electrical contact welding, phase composition, microstrains, size of subblocks, macrostresses.
5. NANOCHEMISTRY – page 809
Bibanaeva S.A., Skachkov V.M.
The effect of metal additives on conversion hematite in the processing of bauxite by the Buyer method – page 809
Abstract: The work is devoted to the study of the influence of mono – and composite metal additives on the process of processing bauxite by the hydro-alkaline method. The chemical qualitative and quantitative composition, morphology of red mud (RM) obtained under conditions of autoclave high- temperature leaching were studied. X-ray phase studies aimed at determining the composition and structure of compounds in red mud were carried out. The prospects of the method of autoclave leaching of hard-to-open bauxites with simultaneous extraction of alumina and conversion of hematite to magnetite by hydrogen gas are shown. It was found that the method allows the processing of bauxite with a high degree of alumina extraction and allows to obtain red mud with different magnetic fraction content and low sodium content. The resulting magnetized red mud is suitable for processing by magnetic separation and makes it a promising raw material for the ferrous metallurgy. The dependence of the degree of conversion of hematite to magnetite on the type of reducing agent is determined. According to the results of the research, a patent for the invention was obtained.
Keywords: the bauxite leaching, the recovery of iron, the Bayer process, red mud, hematite, magnetite.
Glazov I.E., Krut’ko V.K., Vlasov R.A., Musskaya O.N., Kul’bitskaya L.V., Kulak A.I.
Precipitation of hybrid hydroxyapatite / autofibrin nanocomposites – page 818
Abstract: Hybrid composites based on hydroxyapatite and autofibrin were synthesized by precipitation in a medium with pH=9. Soft precipitation conditions and rapid isolation of the composite precipitates favored preservation of a biopolymer matrix of autofibrin. An effect of fibrin macromolecules contributed to destabilization of the amorphous calcium phosphate phase and formation of stoichiometric hydroxyapatite. The medium of the citrated plasma stimulated precipitation of calcium-deficient hydroxyapatite with x≈0,1 and the Ca/P ration of 1,65 which transformed into the mixture of hydroxyapatite / β -tricalcium phosphate at 800 °С. Biomimetic apatite composites were synthesized with an addition of 30 vol. % of a Simulated Body Fluid (SBF) model solution. The effect of Mg2+, CO32- ions of SBF promoted the stabilization of amorphous calcium phosphate and formation of carbonated hydroxyapatite that exhibited thermal stability up to 800 °С. The cummulative effect of autofibrin and ions of induced SBF provided controlling composition of the mineral part of hybrid nanocomposites without disruption of an autofibrin matrix.
Keywords: hybrid nanocomposite, hydroxyapatite, fibrin, citrated plasma, amorphous calcium phosphate, calcium-deficient hydroxyapatite, carbonated hydroxyapatite.
Golovanova O.A.
Synthesis and properties of Sr-containing trycalcium phosphate – page 829
Abstract: Sr -substituted tricalcium phosphate was obtained by precipitation from aqueous solutions. Synthetic solid phases were investigated using X-ray phase analysis, IR spectroscopy, scanning electron microscopy, energy dispersive analysis. The supernatant was examined for the presence of Ca2+ and PO43- ions to calculate the Ca/ P ratio. It was revealed that strontium ions are part of tricalcium phosphate, but do not change its phase composition. The addition of strontium ions to the initial solution contributes to a decrease in the size of crystallites and an increase in their porosity. When studying the bioresorbability of the obtained samples using direct potentiometry, it was found that the samples containing strontium ions in their composition have a lower value of the rate of resorption. Energy dispersive analysis data confirmed that strontium ions are included in the composition of TCP samples. But with an increase in their concentration, complete replacement of calcium ions with strontium ions in the TCP structure does not occur. At the same time, the highest values of the dissolution rate are recorded in acidic media.
Keywords: crystallization, calcium phosphates, substituted tricalcium phosphate, strontium, bioresorbability.
Gubarev Yu.A., Lebedeva N.Sh., Tonkushina M.O., Gagarin I.D., Golub A.Yu., Ostroushko A.A.
Interaction of iron-containing nanocluster polyoxometalate with doxorubicin – page 841
Abstract: Actual problem in the field of targeted drug delivery is transport of highly toxic drugs, with undesirable side effects, in particular antitumor medicine. The thermodynamic parameters of complexation between nanocluster polyoxometalate {Mo72Fe30}, promising as a means of targeted drug delivery, and a cytostatic agent – doxorubicin, widely used in clinical practice, were studied. The interaction of doxorubicin with {Mo72Fe30} was accompanied by an exothermic effect, which indicates an energetically favorable formation of the complex. The kinetics of the release of doxorubicin from the complex in a buffer solution with a pH corresponding to the pH value of blood was studied by fluorescence spectroscopy. The rate constants of destruction processes in the complex, accompanied by the release of doxorubicin, and further complexation of the released doxorubicin with decay products were determined. In the future, it is possible to slow down the release of doxorubicin by stabilizing the {Mo72Fe30}, for example, when it is associated with albumin.
Keywords: Nanocluster polyoxometalates, doxorubicin, complexation, targeted delivery, nanoparticles, rate constant, thermodynamic parameters.
Klychkov N.A., Simakov V.V., Sinev I.V., Timoshenko D.A.
Multiparametric recognition of organic vapors by using a gas sensor based on a nanostructured tin dioxide film – page 852
Abstract: The influence of organic vapors (isopropanol, ethanol, and acetone) with different concentrations in air on a response gas sensor based on nanostructured tin dioxide films synthesized by the sol-gel method was studied. It was found experimentally that inject of the gas mixtures containing organic vapors into measure chamber results to an increase of the conductivity of nanostructured tin dioxide films. In the area of high concentrations (more than 50% of saturated vapor), the concentration dependence of conductivity trends to saturation. The recognizing possibility of species gas admixture by using statistical processing of response only single sensor at different analyzed gas mixture concentrations is validated. The surface donor level of gas-reducing relative to acceptor level oxygen and desorption heat of gas particle were determined. A new method based multiparametric recognition gas mixtures is proposed based on using concentration-independent physical and chemical parameters of analyzed gases as classification properties. It is shown that proposed multiparametric recognition method has higher reliability in comparison with standard methods based on the analysis gas sensor response.
Keywords: gas sensor, sol-gel method, signals preprocessing, adsorption center parameters, multiparametric recognition of gas mixtures.
Krut’ko V.K., Doroshenko A.E., Musskaya O.N., Rabchynski S.M., Kulak A.I.
Apatites formation on electrodeposited calcium phosphates in the Ca(NO3)2 / NH4H2PO4 and CаCO3 / Ca(H2PO4)2 systems – page 860
Abstract: Calcium phosphate coatings on titanium plates were obtained by electrochemical deposition at room temperature in a two-electrode cell at a constant current density of 30 mA/sm2 and a deposition time of 10 min, and brushite coatings from Ca(NO3)2/NH4H2PO4 system at pH = 4, and composite (brushite/calcite/apatite) coatings from the CaCO3/Ca(H2PO4)2 system at pH = 5. The apatite-forming ability (bioactivity) was determined by soaking both types of calcium phosphate coatings in a model SBF solution during month. The newly formed amorphized apatite layer after heat treatment at 800 °С crystallized into β –tricalcium phosphate/hydroxyapatite on brushite coatings and hydroxyapatite on composite coatings due to the presence of calcite, whose carbonate ions initiate formation of hydroxyapatite, as well as apatite nanoparticles in the initial coating. The obtained calcium phosphate coatings are promising as biocoatings capable to increase osseointegration of metal implants.
Keywords: calcium phosphate coatings, brushite, calcite, SBF model solution, apatite, hydroxyapatite.
Krut’ko V.K., Maslova L.Yu., Musskaya O.N., Safronova T.V., Kulak A.I.
Modification of calcium phosphate foam ceramics with bioapatite in SBF solution – page 870
Abstract: The multiphase calcium phosphate foam ceramics, represented by β -tricalcium phosphate ( 65%) and β -calcium pyrophosphate ( 25 %),including hydroxyapatite (5 %) and α -tricalcium phosphate (5 %), with 60–64 % porosity and a through architecture of polyurethane foam was obtained. The application of a layer of hydroxyapatite led to an increase in the content of hydroxyapatite to 25 %, α -tricalcium phosphate to 40%, and an increase in static strength to 0,03 MPa with a decrease in porosity to 49%. The application of the second layer of hydroxyapatite promoted an increase in the content of hydroxyapatite to 40%, the static strength reached 0,05 MPa at a porosity 40 %. The bioapatite formation in the shape of «foam spheres» with a size from 2 to 10 μm occurred in the process of modifying all types of foam ceramics in a SBF solution during 21 – 28 days. The modified calcium phosphate foam ceramics enriched with α -tricalcium phosphate and hydroxyapatite, was characterized by the maximum static strength 0,08 MPa at a porosity 38%.
Keywords: calcium phosphate foam ceramics, hydroxyapatite, polyurethane foam, tricalcium phosphate, SBF (Simulated body fluid), bioapatite.
Kryukov T.V., Feofanova M.A., Skobin M.I., Ivanova A.I.
Synthesis and physicochemical study of the cerium and cefazolin metal complex – page 881
Abstract: In this work, a team of authors obtained and isolated in solid form a metal complex compound by the interaction of aqueous solutions of trivalent cerium chloride and sodium salt of cefazolin. Its elemental composition was determined using the X-ray spectral electron probe analysis. The thermal characteristics of this compound, the temperature of its decomposition, the composition and the method of coordination of the inner sphere of this metal complex were clarified by the methods of thermogravimetry, differential scanning calorimetry and IR spectroscopy. Based on the data obtained, the inner sphere of the metal complex contains three molecules of cefazolin and three molecules of inner-sphere water. The composition of the inner sphere corresponds to the formula [CeCzl3(H2O)3]. Taking into account IR spectroscopy data, the authors concluded that the most likely way of coordination of cefazolin to the central ion is through the amide and carboxyl groups.
Keywords: coordination compounds of rare earth elements, cefazolin, cefazolin complexes, cephalosporins.
Malkanduev Yu.A., Kokoevа A.A., Dzhalilov A.T.
Polymerization by interaction α-haloacrylic acids with tertiary amines – page 890
Abstract: The results of spontaneous polymerization of α -chloroacrylic and α -bromoacrylic acids with tertiary amines at a low temperature are presented. As a result of spontaneous polymerization during the interaction of α -halodacrylic acids with tertiary amines, polymers containing quaternary ammonium groups are formed. In order to confirm this assumption, nuclear magnetic resonance and infrared spectroscopic studies of the products of the spontaneous polymerization were carried out. Spontaneous polymerization proceeds, consisting of two stages: the quaternization reaction and the polymerization reaction. The kinetic regularities of the polymerization reaction were studied and it was shown that the quaternization reaction, which is the limiting stage of the spontaneous polymerization process, proceeds according to the SN2–mechanism. It has described the first attempts to obtain new nanocomposite materials based on synthesized copolymers and modified montmorillonite. Analysis of the literature data shows that the features of the preparation of nanocomposites based on Na+–montmorillonite and water-soluble copolymers have not been previously studied.
Keywords: polyelectrolytes, chloroacrylic acid, bromoacrylic acid, spontaneous polymerization, polymerization kinetics, quaternary ammonium salts, composite.
Medyankina I.S., Skachkov V.M., Pasechnik L.A.
Kinetics aspect of hydrochemical fluorination of silicon-containing industrial waste – page 900
Abstract: A method for producing amorphous silica from the enrichment wastes of low-titanium vanadium containing titanomagnetites of JSC «EVRAZ ZSMK» – wet magnetic separation tailings is proposed. The use of a NH4HF2 solution makes it possible to practically selectively extract silicon into the solution in the form of ammonium hexafluorosilicate. The extraction of silicon with 1,0–2,5 wt.% NH4HF2 solution for 6 hours reached 46 %. The diffusion process of the silicon extraction is described by the kinetic equation 1–(1–α)1/3=0,0043·exp(–5230 / RT)·τ. Amorphous silica obtained by the sol-gel method from a fluoride silicon-containing solution has a highly developed surface 320 m2/g, the particle size calculated from the average density of «white carbon black» is of 10 nm. The increase in concentration to 20 wt. % NH4HF2 leads to the rise of the silicon solubility and of other tailings components, which are unwanted impurities in the final product. In general, it is shown that the hydrochemical leaching of silicon-containing industrial waste – tailings with weak solutions of ammonium hydrofluoride is promising for the synthesis of pure amorphous silica.
Keywords: wet magnetic separation tailings, amorphous silica, ammonium hydrofluoride, fluorination, kinetics of the process.
Nalimova S.S., Shomakhov Z.V., Punegova K.N., Ryabko A.A., Maximov A.I.
Synthesis and study of gas-sensitive nanostructures of the Zn–Sn–O system – page 910
Abstract: Zinc oxide nanorods were synthesized by the hydrothermal method. The obtained samples were processed in an aqueous-alcohol solution of potassium stannate and urea at 170 °C during different times. As a result, Zn–Sn–O nanostructures were obtained. The surface chemical composition of ZnO and Zn–Sn–O was studied using the X-ray photoelectron spectroscopy. Its sensitivity to vapors of isopropyl alcohol (1000 ppm) at 120 °C, 180 °C, 250°C was analyzed. The electron density redistribution during the Zn–Sn–O composite nanostructures formation manifests itself in the chemical shift of the O1s and Zn2p peaks. It confirm the rearrangement of chemical bonds when zinc atoms are replaced by tin ones. It was found that the sensitivity of composite structures to isopropyl alcohol vapors significantly exceeds that of ZnO in the entire temperature range under study. The improvement of gas-sensitive properties is associated with the presence of various types of surface centers in the Zn–Sn–O samples that participate in the adsorption and oxidation of isopropyl alcohol.
Keywords: zinc oxide, zinc stannate, gas sensors, nanorods, X-ray photoelectron spectroscopy.
Rozhentsev D.A., Mansurov R.R., Tkachev N.K., Russkikh O.V., Ostroushko A.A.
Catalytic properties in the heterogeneous Fenton reaction of the surface of nanoporous iron obtained by electrochemical dealoiyng in melted chloride mixtures – page 919
Abstract: The samples of partially oxidized micro- and nanoporous iron obtained by high-temperature dealloing of an iron-manganese alloy in a molten salt were investigated. The data concerning the structure of the samples and the composition of their surface were obtained by electron microscopy; it was found that after washing at room temperature in air the oxide phases of iron were formed as whiskers with a thickness of about 10 nm. During the preparation of the samples a quantitative removal of manganese from the initial alloy was achieved. The catalytic activity of the obtained samples in the heterogeneous Fenton reaction was estimated by oxidation of methyl orange by hydrogen peroxide. The rate of the first stage of the reaction, which was described by the first-order equation, was determined by the most active spent part of the samples, and then the reaction passed into the stationary mode. The nanoporous samples possessed a higher catalytic activity.
Keywords: nanoporous iron, dealloying, iron oxide whiskers, catalytic activity, Fenton reaction.
Kharaev A.M., Bazheva R.Ch.
Study of relaxation transitions in some aromatic polyesters – page 928
Abstract: The spin probe method was used to systematically study the main relaxation transitions of rigid-chain glassy polymers in a wide temperature range using spin probes of different sizes using polysulfone as an example. In the main relaxation region of aromatic polyesters, two inflections were found using the spin probe method. The two inflections found in the temperature dependence of the rotation correlation time are the result of unfreezing of segmental mobility in regions with different packing of segments. It was shown that the high-temperature inflection corresponds to the defrosting of the cooperative-type segmental mobility (α -transition), and the inflection at a lower temperature corresponds to the β -defrosting of the segmental mobility of the local type (the α′-process). To explain the nature of this transition, a theoretical model of the polymer was used, where it is assumed that different levels of supramolecular organization are possible in amorphous polymers, i.e. the existence of more ordered and more densely packed regions, which alternate with looser and less ordered regions. The influence of various factors on the position of the α′-transition on the temperature scale is investigated. The choice of the probe volume on the basis of a strictly substantiated model of its motion made it possible to reveal the relationship between the rotational motion of the probe and the motion of individual segments of the amorphous polymer below the glass transition temperature.
Keywords: polyester, polysulfone, polycarbonate, spin probe method, glass transition temperature, pre-carbonate temperature.
Yasnaya M.A., Blinov A.V., Golik A.B., Maglakelidze D.G., Gvozdenko A.A., Kravtsov A.A., Blinova A.A.
Influence of the polyethylene glycol molecular mass on thermal transitions of nanosized copper oxide – page 937
Abstract: In this work, samples of nanosized copper oxide stabilized with polyethylene glycol of various grades with molecular weights from 200 to 6000 Da were obtained. The crystal structure of the samples was investigated by X-ray diffractometry. As a result of the XRD analysis, it was found that the samples have a monoclinic crystal lattice with space group C2/c . The effect of the molecular weight of the polymer on the size of nanoparticles was studied by the photon correlation spectroscopy method. Analysis of the results showed the presence of one fraction of particles in all samples, the size distribution was monomodal. It was found that the molecular weight of polyethylene glycol has an effect on the CuO particle size in colloidal solutions, while the phase composition and crystallite size remain unchanged. The average hydrodynamic radius of CuO particles in the obtained samples was about 140±40 nm. The smallest hydrodynamic radius of 70±15 nm was observed in a sample of nanosized copper oxide stabilized with polyethylene glycol with a molecular weight of 6000 Da. The effect of stabilizers with different molecular weights on the phase transitions of samples during heat treatment was investigated by the synchronous thermal analysis. As a result of thermal analysis, it was found that the optimum temperature for calcining nanosized CuO powders was 500°C.
Keywords: copper oxide (II), polyethylene glycol, synchronous thermal analysis, XRD, photon correlation spectroscopy.