Search

The results of a search for correlations between the crystal-geometry parameters and structural-phase states in the alloys based on Ag–Me (Me = Co, Rh, Ir, Ni, Pd, Pt, Cu, Au) are presented. The limits of numerical values of the crystal-geometry and thermodynamic factors are identified, within which inorganic regions of solid solutions are formed in the state diagrams of binary systems or monotectic reactions take place in the systems due to a limited solubility of the system components in liquid states. It is shown that an approach relying on the analysis of state diagrams, including the crystal-geometry and thermodynamic factors of the alloy-forming elements into consideration, is promising in searching for common patterns of structural-phase states in the Ag-based alloys; it is found out that an Ag–Pt system is the most attractive binary system in this respect. A slight deviation of the experimental concentration dependences of the atomic volume in the solid solutions of the Ag–Pd and Ag–Au systems from the Zen relation is observed in intermetallic compounds in the alloys of the Ag–Pt system.

The effect of UV radiation on the efficiency of bisphenol A (BPA) phototransformation in water in the presence of polypropylene nonwoven material based on ultrafine fibers has been studied. The absorption and fluorescence spectra of the investigated substance with fibers of different properties have been obtained. After excitation with an excilamp, the main photoproduct - BPA - fluoresces in the region of similar to 408 nm. With an increase in the irradiation time from 0 to 10 min, the fluorescence intensity of this photoproduct increases. The absorption and fluorescence spectra of cyclohexane containing compounds desorbed from the fiber surface indicate the adsorption of the photoproduct on its surface during UV irradiation.

Using a novel ejection spraying unit and relying on new approaches, fibers are formed by the method of pneumatic melt blowing of polycarbonate, polypropylene, and polyethylene terephthalate. The proposed approach is based on the concepts of atomization of the polymer melt flow as a preferential regime for fibermaterial formation. From the analysis of the values of numerical characteristics in the zone of atomization and the physical background of the criteria under study a conclusion is drawn that the essential role in destruction of the jet belongs to the formation of a boundary layer in the melt under the action of friction forces, followed by its separation. An assumption is made on the prevailing action of the separating destruction of the melt jet via the mechanism of ‘skinning’ of the boundary layer of the melt due to a shorter time of its persistence compared to the development of the Kelvin–Helmholtz instability.

New approaches are proposed, relying on which the coatings from nanodispersed oxide materials are formed on polypropylene fibers. It is shown that in the course of the viscous fluid – solid state transition of the polymer its nanoparticles are stabilized on the surface of the formed fibers.

The effect of the nature of carbon nanofillers on the structure-sensitive characteristics of resistive composites with polyurethane binders is investigated. The influence of the size, shape, concentration of carbon nanofibers (K-163 channel black, GE-3 graphite element, C-1 colloid graphite) and the method of their introduction into the binder on the formation of an electrically conductive mesh in the structure of the composite is identified. It is experimentally found that an introduction of C-1 colloid graphite ensures optimal parameters of specific volume resistivity, hardness, and adhesion strength, as well as low values of the percolation threshold.

The results of investigations of structural-phase transitions in the polypropylene melt-blown fiber materials before and after their short-term exposure to microwave radiation are presented. Using the methods of X-ray diffraction analysis and differential scanning calorimetry (DSC), it is shown that the smectic mesomorphic phase transforms into a stable monoclinic α-crystalline structure due to dielectric heating of the water molecules adsorbed on the surface of the material, without any changes in its crystallinity degree. Based on the calorimetric data, it is found that a microwave treatment of the material results in the formation of a crystalline phase with a homogeneous structure and increases its melting temperature.

In this paper, a method for determining the doping efficiency of dispersed semiconductor metal oxide materials is proposed proposing to use the dependences of the free charge carrier concentration, normalized to the concentration of the doping impurity (Ne spec.), on the content of this impurity. The possibilities of this method are demonstrated by the example of studying the effect of technological factors on the efficiency of doping of indium oxide with tin and doping of tin oxide with antimony. It is shown that it is impossible to achieve the concentration of free charge carriers in the ITO material, higher than that in ATO materials, due to the lower solubility of tin in the In2O3 lattice, as compared with the solubility of antimony in the SnO2 lattice.

In this paper, we present an IR spectroscopy study of the molecular and supramolecular structure of the polypropylene fibre, used as a metal nanoparticle carrier, by the example of nanoparticles of tin dioxide. The aim of this work is to investigate the changes in the chemical structure of the polypropylene melt-blown web when modified with the tin dioxide nanoparticles. The paper shows that the metal-oxygen valence vibration bands appear in the IR spectra of modified polypropylene fibrous carriers. At the same time, the carrier material remains stereoregular and possess a helical structure.

Using electronic spectroscopy and fluorescence techniques, the degradation of 2-methyl-4-chlorophenoxyacetic acid has been researched in water under the excitation with UV radiation produced by a KrCl excimer lamp in the presence of “TiO2, SnO2, SnO2/TiO2Nanoparticles – Polypropylene Fibrous Carrier” Systems. It has been determined that MCPA phototransformation is most efficient when using the “TiO2/SnO2heteronanoparticles – carrier” system with the concentration of 25/6 mg/g. The results indicate that systems with applied semiconductor particles do not exhibit sorption properties towards МСРА molecules. Therefore, the change in the spectral characteristics of a МСРА water solution after time-exposure and exposure to radiation is only associated with the phototransformations of non-adsorbed МСРА molecules and with the emergence of their photodegradation products.

Results of investigations of the reflection and transmission coefficients of flat specimens made from multifunctional composite polyurethane-based materials with fillers of three types: channel black K-163, colloidal graphite preparation С-1, and elemental graphite GE-3 are presented in teraherz frequency range. The calculated complex dielectric permittivity in this frequency range is presented. It is demonstrated that specimens with carbon filler content of 10 mass% and higher effectively reflect teraherz electromagnetic radiation, and specimens with filler content of 5 mass%, can be used as radio absorbing coatings. The feasibility of application of these materials for heating elements of press plates is analyzed.

The results of investigations of the complex permittivity, diffuse-reflectance, and characteristics of crystal lattices of tin-doped indium and dysprosium oxides are presented. Using the methods of spectroscopy and X-ray diffraction analysis, it is shown that doping of indium oxide with tin results in a significant increase of the components of the indium oxide complex permittivity and an appearance of the plasma resonance in its diffuse-reflectance spectra. This indicates the appearance of charge carriers with the concentration of more than 10 21 cm −3 in the materials. On the other hand, doping of the dysprosium oxide with the same amount of tin has no effect on its optical and electromagnetic properties.

A physicochemical research of the processes of phase composition formation in the materials of the Dy-Sn-O system was performed. Phase composition was taking place in the course of thermal treatment of dysprosium (III) and tin (IV) codeposition products. These were codeposited from nitrate solutions at pH 7, and 25% ammonia water was used as the precipitant. Using thermal and X-ray diffraction analysis, it was found that in the above system at 90 wt. % of Dy2O3 and 10 wt. % of SnO2, when the precursors were heated above 600°C there are no solid solutions. In the meanwhile, at temperatures below 1000°C there is only one phase, Dy2O3. At temperatures above 1000°C, the system becomes bi-phase and includes Dy2O3 and Dy2Sn2O7.

In the current article the use of nanoparticles of titanium dioxide is justified to be an active component of the photocatalytic materials. The relationship between composition, structure and bactericidal properties of titanium dioxide is also established. It is shown that the polypropylene carrier comprising on a surface of at least 2.1 ± 0.3 mg/g of titanium dioxide nanoparticles, where both phases of titanium dioxide such as rutile and anatase are presented, allows the antibacterial treatment of water with high efficiency and it can be used for water purification from microbial contamination.

Thermostability of resistive materials based on polyurethane used as heat-liberating elements in the design of heating elements of thermoactive formworks is investigated. The application of polyurethane as a binder provides solid contact of polymer molecules with nanodimensional carbon fillers and their uniform distribution in a composite material. The influence of thermal treatment and dispersed fillers on the stability of electrophysical and thermophysical properties of carbon-filled polyurethane coatings is established.

Theoretical estimates are made of the thermodynamic functions of fluorammonium complexes of 4f elements. Using techniques of statistical thermodynamics, we have obtained the temperature dependences of the basic thermodynamic state functions (C p , ∆H, ∆S, and ∆G). The decomposition temperatures of the investigated complex fluorides of 4f elements have been estimated on the basis of an analysis of the obtained dependences.

Using the fluorescence, IR, and electronic spectroscopy methods, we have investigated the spectral characteristics of the surface of a polypropylene microfiber before and after their UV irradiation. We have studied the degradation of naphthalene and phenol in water exposed to UV radiation in the presence of fibers. As a radiation source, we used a KrCl excilamp with a radiation wavelength of 222 nm. It has been revealed that, after irradiation, photooxidation of the fiber surface occurs. The degree of crystallinity of examined samples remains almost the same after their irradiation. We show that, as a result of the adsorption of naphthalene and phenol on the fiber surface, their concentration in aqueous solutions efficiently decreases. Maximally, the concentration of naphthalene decreased 21-fold and that of phenol decreased 4-fold. Under UV irradiation of the system toxicant + water + fiber by the KrCl excilamp, fluorescent photoproducts are formed in the system and are adsorbed on the fiber surface.

The present paper is devoted to studying structural and morphological properties of the resistive composite materials based on the polyurethane binder. The paper shows the influence of nature, size, shape, concentration of conductive carbon fillers (channel black K-163, graphite element GE-3, colloidal-graphite preparation C-1) and the method of their introduction into the binder to form the electrical conductivity of composites. Experimentally it was found out that a homogeneous composite structure reaches dispersive mixing filler and binder within 120 min. The analysis of the morphological pattern surfaces and chipping resistance materials has demonstrated that composites with colloidal-graphite preparation C-1 are more unimodal with the same concentrations of the investigated fillers.

Methods of physical and numerical experiments are used to investigate formation of quantum dissipative silver nanostructures on polypropylene microfibrous condensed-state carriers under two-stage activation by UV- and microwave radiation. For these two nanoprocessing stages, two different mechanisms of quantum activated silver nanoparticle relaxation are suggested, including dissipation of their energy into the polymeric matrix through the exciton femtosecond and phonon picosecond channels. A comparison of the results of mathematical modeling and physical experiments testifies to the adequacy of these models to the physical processes of self-assembly and self-organization of polymeric biomimetic fibrous material modified by silver nanoparticles.

3Methods of electron absorption and fluorescence spectroscopy are used to investigate degradation of naphthalene in water upon exposure to UV radiation of a KrCl excilamp in the presence of polypropylene microfibers (PMF) modified by TiO2 and SnO2 particles. The results obtained demonstrate that the naphthalene concentration is halved in the presence of PMF. This is caused by the naphthalene adsorption on the PMF surface. UV irradiation of the naphthalene–water−PMF system leads to the formation of fluorescing naphthalene photoproducts in water and on the PMF surface. Naphthalene phototransformation products are detected by the chromatography-mass spectrometry method.

The possibilities of the isotope-selective excitation of molecules by CO laser radiation. More specifically, the problem of determining the conditions of the preferable excitation of heavy isotope 3C18O compared to the light isotope 12C18O is set. A carbon monoxide molecule is capable of absorbing at hundreds of vibrational-rotational lines within the principal absorption band of the CO molecule over the 1200–2600 cm−1 range. Since radiation absorption is negligibly low in the frequency range below 1900 cm-1 and there are no appreciably efficient radiation sources over the 2200–2600 cm−1 range in which absorption can be observed, the 1900–2200 cm−1 frequency range is considered in this work. The presented calculations may refer to the selective excitation of the gas phase in bulk and in gas absorbed on the surface.

Nanocrystals of stable, tetragonal tin dioxide have been synthesized using microwave processing, and the effect of microwave heating on the structural phase transformations of the tin compounds involved has been examined. The results are used to determine microwave heating parameters that ensure strong bonding of nanocrystals to the surface of polymer fibers.

The most probable parameters of the pure, doped, and mixed GaSe1−xSx (x ≤ 0.4) crystals (solid solutions) are presented together with the results of investigations of their crystal structure and defects, optical and mechanical properties, and damage thresholds.

The thermochemical processes of synthesis and purification of rare earth metals fluorides through the transfer of fluoroammonium complexes were discussed. By differential thermal calorimetry the temperature maxima of rates of formation and decomposition of complex compounds were defined and the values of the apparent activation energy processes were determined. It is possible the use of fluoroammonium systems to develop the preparation of anhydrous fluorides of rare earth metals.

The influence of thermal treatment and dispersed carbon fillers on the thermostability of polyurethane binder is established. The conditions of thermal treatment of thick film composite resistive coatings have been defined to be further used in structures of electric heaters. It was found that the thermostability of resistive coatings based on polyurethane varnish Kontracid D3010 is reached by means of thermal treatment at a temperature of 120°C during 2 hours and is characterized by the completion of a reaction between the hydroxyl and isocyanate groups.

The influence exerted by the composition of film-forming solutions based on acetylacetone on the electrical and optical properties of indium-tin oxide films obtained from these solutions by the dip-coating process was revealed.

A thermodynamic calculation of nucleation during codeposition of indium and tin hydroxides is presented. A thermodynamic probability of phase formation is evaluated. The theoretical results obtained are in good agreement with experiment.

Coprecipitation of tin(II, IV) and antimony(III) from chloride solutions was studied by X-ray phase analysis, thermogravimetry, IR spectroscopy, and elemental analysis.

Frequency dependences of transmission and reflection coefficients, dielectric permeability of composite materials with the various content of carbon fillers (technical carbon, graphite) in polyurethane varnish in ranges of frequencies 26–40 GHz and 110–260 GHz are experimentally investigated. It was found that composite material 0.4 mm thick with 4–5 % graphite mass content has a transmission coefficient of less than minus 7 dB in the whole investigated range of frequencies and can be effectively used in devices of protection from electromagnetic radiation.

Gas-sensitive (sensory) properties of bismuth-tin oxide materials, including ceramic films with the Bi2Sn2O7 composition and pyrochlore structure, were considered, as applied to the determination of H2, CO, and CH4 in an air mixture.

Catalytic activity of oxide nanostructure catalysts fixed on the surface of polymeric carrying agents was studied in relation to the removal of organic substances difficultly decomposed by the chemical oxidation in the processes of ozonation of aqueous solutions.

New materials with prescribed isotopic composition could open good possibilities of functional characteristics needed for the progress in science and technology. [1]. It have been shown, that the thermal conductivity of the monocrystallic 70Ge (99,99 %) at 15 K was as much as 8.1 higher than the corresponding parameter of the natural isotopic structure [2]. Applications of the single isotopes compositions are restricted by their high cost. That's why it is very promising to find out new and less expensive methods of isotope separation and characterization of new materials [1].

Structure, defects, mechanical and optical properties of GaSe1-xSx, 0

The research paper deals with the performance of composite resistive material heating coatings based on the polyurethane binder, filled with colloidal-graphite preparation C- 1, which can be used in structures of electric heaters. Frequency dependences of transmission and reflection coefficients, dielectric permeability of composite materials with the various content of carbon fillers (technical carbon, graphite) in polyurethane varnish in ranges of frequencies 26-40 GHz and 110-260 GHz are experimentally investigated.