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The photocatalytic activity of heterostructural α-Bi2O3/Bi compositions obtained by low-temperature pyrolysis of bismuth complexes with sorbite has been investigated. The efficiency of catalysts has been estimated based on the decomposition rate of methylene blue under illumination by visible light. The obtained catalysts are characterized by different contents of metallic Bi and different degrees of imperfection of the α-Bi2O3 lattice, which was obtained by changing the amount of sorbite in the composition of the precursor organomineral bismuth complex and varying the synthesis temperature. It is established that isothermal annealing of the α-Bi2O3/Bi compositions in air in the range of 400–600°C leads to relaxation of defects and an increase in the α-Bi2O3 lattice volume. An increase in the annealing temperature to 550°C is accompanied by a rise in the α-Bi2O3/Bi catalytic activity. However, the heterostructure degrades at higher temperatures as a result of metallic bismuth oxidation, while the catalytic activity decreases.

The solid-state formation of gallium antimonide on Si(111) from a stoichiometric mixture of GaSb in the temperature range of 300 °C–500 °C and thicknesses of 12–40 nm was studied under ultrahigh vacuum conditions. The influence of the preformed GaSb seed islands on the morphology, composition, and structure was studied. It has been found that at 300 °C a strained continuous polycrystalline film is formed, which rupture at 350 °C. It has been shown that a continuous single-crystal GaSb film grows at 400 °C–500 °C if the sample is annealed at a weak antimony flow. This is also facilitated by the preliminary formation of a high density of nanosize GaSb seed islands. As a result, a continuous relaxed film with epitaxial relations GaSb(111)∣∣Si(111) and GaSb[1–10]∣∣Si[1–10] was obtained from a GaSb mixture 40 nm thick at 500 °C. We demonstrate a possibility of direct formation of GaSb on Si(111) without buffer layers of other chemical elements.

The results of a cross-correlation analysis of the relationship between the process conditions for obtaining CoNiFeSiB amorphous alloys, their physical and chemical properties and structure are presented. The alloys are obtained by single-roll rapid quenching on a copper wheel at frequencies from 30 to 60 Hz, which corresponds to linear velocities from 22 to 38 m/s, a chamber pressure from 0.05 to 0.6 atm, and a pressure in the crucible from 0.4 to 0.6 atm. Elemental analysis is carried out; the atomic and surface structures, phase-transition parameters upon heating, and the corrosion properties are investigated. Correlations between the structural-ordering parameters and physical and chemical properties are determined. Regression models of the dependence between the structural characteristics, physical and chemical properties, and process conditions of production are formulated. A regression model for the dependence of the average cluster area in the atomic image on the specific energy of structural changes is proposed. The concentrations of nickel, silicon, and boron in cobalt-based alloys are found to play an important role in determining the structural characteristics and properties of the alloys.

This work is dedicated to a study of the influence of the duration of an electrical discharge on the size of the melting zone formed at a cathode of VT20 titanium alloy. It is found that the melting zone possesses radial symmetry and is surrounded by a ring-shaped zone, whose surface is exposed to electrical erosion. The dependence of the radii of the melting region and the erosion zone, and of the volume of melted metal on the duration of the discharge pulse is determined in the interval from 0.05 ms to 1 ms. A mathematical model is proposed, allowing us to calculate the temperature distribution in a metal plate at different times during the discharge. The parameters of a nonstationary surface heat source arising in the region of the electrical discharge are found from the condition of coincidence of the position of the boundary of the solid–melt phase transition observed in experiments and determined by solving the heat transfer equation.

The search for inexpensive and efficient methods of forming thin BaSi2 films as a promising material for photovoltaic is an actual task. The co-deposition of Ba and Si atoms with alloy thickness of 100-120 nm on the silicon substrate at room temperature with following annealing (SPE method) was proposed. Ba-Si alloy compounds then were thermally annealed at different temperatures and three samples were formed: #1 at T = 600 ° C, #2 at T = 700 ° C and #3 at T = 800 ° C. Polycrystalline films with an orthorhombic BaSi2 structure were formed by XRD, UV-VIS, FIR and Raman spectroscopies data. BaSi2 grains in samples #1 and #2 have sizes 62-64 nm and 86 nm in the sample #3 from XRD data calculations by Scherrer formula. Proposed growth method resulted to strong compression of the BaSi2 unit cell volume on 1.78 – 2.70%. The strongest compression was observed after annealing at 800 °C, which was accompanied by desorption of a noticeable amount of barium and a strong decrease in the film thickness in the sample #3. The formation of nanosize Si clusters was confirmed by Raman data for samples #2 and #3, but they did not observed in the sample #3. So, the film, formed at 800 °C, is the most qualitative in terms of structure and single-phase BaSi2, but with strong decrease of initial Ba-Si alloy thickness due to Ba desorption.

This work is devoted to the wear nature of Fe–Ni–Cr–W–Mo–Co–C–B metal glass coatings on steel 1035 substrate via electrospark deposition in various granules mediumcompositions. The microhardness, roughness, and wear resistance of the coatings under dry abrasive and dry sliding wear conditions in the load range of 2.2 to 50 N were studied. During dry abrasive friction, the minimum specific wear rate of the coatings was 1.4 to two times lower than that of steel 1035 in all load ranges. Tests of the Fe33Ni8Cr8W8Mo8Co8C16B11 coating resistance to dry friction against P6M5 steel showed that its wear at 30 km was 1.5 to two times lower than steel 35, but, with a decrease in the normal load, the greatest effect of steel hardening was observed. The results show that the method used in the electrospark deposition of the Fe33Ni8Cr8W8Mo8Co8C16B11 granules mixture can protect the steel substrate from abrasive and sliding wear at low loads and speeds.

FeCrWMoC metallic glass (MG) is synthesized in the form of coatings by electric spark treatment in grain media consisting of individual components. It is demonstrated that the amorphous phase fraction in the composition of the coatings increases with the time of the granule treatment increasing to 100–150 min. The proposed approach offers the potential for the one-stage synthesis of MG in the form of coatings in the automatic mode.

The synthesis of nanotubes and faceted nanocrystals of titanium dioxide doped with alkali metals cations has been performed. It has been established that TiO2 nanotubes with lengths of up to 100 nm and thicknesses of 50–500 nm obtained by solvothermal synthesis have an anatase structure in the direction of crystal growth. Faceted TiO2 particles with sizes of 80–150 nm doped with Na and K cations (2–7 at % calculated to a yield of TiO2 yield) preserve the anatase structure, whereas doping with Li induces the formation of a mixture of anatase and rutile. An analysis of the diffuse reflectance spectra showed that dopants had an insignificant effect on optic properties of TiO2 nanoparticles. The high activity of these catalysts is explained by a decrease in the rate of recombination of charge carriers, rather than by the increase of their photo-generation yield.

Crystalline FeWMoCrBC electrode materials were prepared by conventional powder metallurgy. Metallic glass (MG) coatings were produced by electrospark deposition onto AISI 1035 steel in argon atmosphere. X-ray diffraction and scanning electron microscopy verified the amorphous structure of the as-deposited coatings. The coatings have a thickness of about 40 microns and a uniform structure. The results of dry sliding wear tests against high-speed steel demonstrated that Fe-based MG coatings had a lower friction coefficient and more than twice the wear resistance for 20 km sliding distance with respect to AISI 1035 steel. High-temperature oxidation treatment of the metal glass coatings at 1073 K in air for 12 h revealed that the oxidation resistance of the best coating was 36 times higher than that for bare AISI 1035 steel. These findings are expected to broaden the applications of electrospark Fe-based MG as highly protective and anticorrosive coatings for mild steel.

Titanium oxide particles are produced using electric-discharge dispersion of titanium in aqueous solution of hydrogen peroxide. Electron vacuum microscopy, X-ray diffraction, and diffuse reflection spectroscopy are used to study the morphology, composition, and optical characteristics of the erosion particles. It has been demonstrated that the particles consist of titanium and titanium oxides with different valences. The edge of the optical absorption is located in the UV spectral range. The band gap is 3.35 eV for indirect transitions and 3.87 eV for direct allowed transitions. The band gap decreases due to the relatively long heating in air at a temperature of 480–550°C, so that powder oxide compositions can be obtained, the optical characteristics of which are similar to optical characteristics of anatase. The erosion products are completely oxidized to rutile after annealing in air at a temperature of 1000°C.

s Thick epitaxial Ca2Si(100) films were first grown on Si(111) substrates by forming a sacrificial Mg2Si(111) template and converting it into the Ca2Si template. It was found that a temperature of 250 °C is sufficient to transfer it into the Ca2Si template with sufficient uniformity. During Ca and Si co-deposition at 250 °C, epitaxial Ca2Si(100) domains with two orientations are formed in a thin (100 nm) film, and increasing the substrate temperature to 300 °C leads to a deterioration in the Ca2Si crystalline quality due to a partial violation of its continuity and grain growth of the CaSi phase from Si substrate. An increase in the film thickness to 400 nm at 250 °C led to the appearance, in addition to the Ca2Si(100) epitaxial phase, of the second Ca2Si(010) epitaxial phase with both contributing to the LEED pattern. From the transmission and reflection spectra of the grown samples, it was found that Ca2Si film has a first direct interband transition at E1d = 1.095 ± 0.15 eV, strong defect adsorption lower 1.0 eV and dispersionless refractive index no ≤ 3.8. Eight Raman peaks and 6 FIR peaks were first registered and identified, which are in good agreement with theoretical calculations. The absorption coefficients characteristic of FIR peaks was determined, which can be used further in the quick estimation of the thickness of Ca2Si films through an intensity of FIR absorption peaks.

Thermostable monodisperse nanoparticles of anatase with a diameter of 35–50 nm doped with tungsten were obtained by the method of hydrothermal synthesis. It was found that the temperature of the phase transition from anatase to rutile decreases from 905 to 650°С with the increase in the content of tungsten oxide from 0.35 to 4% in the precursor. Diffuse reflection spectra of the synthesized nanoparticles were obtained, and the values of the band gap were determined. The band gap varies with changes in tungsten content from 3.15 eV for pure anatase to 2.91 eV for TiO2/WO3(4%), leading to an increase in the optical absorption in the visible and the ultraviolet regions.

A novel scheme of electrospark deposition of hardening coatings on steel substrate is presented. According to it, the workpiece-substrate which must be coated is placed in the center of a hollow cylinder and filled with granules of WC–Co alloy. The current pulses are passed from the cylinder wall through granules to the cathode. Electrical discharges occur at the points of contact between the hard alloy particles and the cathode surface, and the coating forms on all surfaces of the workpiece simultaneously. This processing configuration is more productive and can facilitate the automation of the electrospark deposition (ESD) of coatings. In this paper, the influence of treatment duration and size of granule fractions on the mass transfer, structure, roughness, microhardness, and wear resistance of the coatings is investigated. It is shown that the obtained coatings have a structure and properties similar to those of traditional electrospark WC–Co coatings.

This paper deals with the formation of titanium aluminide coatings by electrospark deposition and the investigation of their properties. The coatings were prepared by the sequential deposition of titanium and aluminum onto steel 35 in various atmospheres (argon, air). It has been established that the TiAl3 and Al3Ti0.75Fe0.25 intermetallics are formed as a result of the alloying of the surface layer on the steel substrate. The preferred deposition arrangement is “titanium-aluminum.” Titanium nitride and aluminum oxide have been detected in coatings deposited in air. The protective coatings allowed us to increase the wear resistance of the steel substrate 3–4 times, and the heat resistance, 11–16 times.

One-piece hard-alloy end mills are characterized by excellent wear resistance but they are too expensive, on account of the frequent shaft failure. Multicomponent hard-alloy end mills are even more expensive. In many operating conditions, however, composite hard-alloy end mills are competitive with onepiece and multicomponent mills and are much less expensive.

Carbonaceous matter (CM) in shales of some deposits and occurrences of the Russian Far East has been studied by scanning and transmission electron microscopy, Raman spectroscopy, and X-ray phase and differential thermal analyses. It was shown that the carbonaceous matter in the high-temperature shales (amphibolite facies) of the Soyuznoe deposit is represented by holocrystalline graphite, while the low-temperature (greenschist facies) shales of the Sutyr and Kimkan sequences contain mainly nanocrystalline graphite. It was substantiated for natural objects that platinum is assimilated by graphite at high temperatures. This should be taken into account in planning the prospecting works, as well as in developing a technique for enrichment of carbonaceous ore, because high-temperature carbonaceous shales with holocrystalline graphite are promising for Pt, unlike their low-temperature analogues with nanocrystalline graphite.

Electrospark deposition was employed to clad WC-10%Co, W/C1.6-10%Co, and W/C0.5-10%Co hard alloys on steel 1035, and the tribological properties of the coatings obtained were examined. The influence of the W/C ratio in the electrode materials on the decarburization of tungsten carbide was studied. It is shown that the degree of tungsten carbide degradation can be reduced by increasing the concentration of carbon in the WC-Co electrode materials, and also that the WC decarburization reaction is reversible on annealing. Coatings deposited using new electrode materials with an excess of carbon (W/C0.5) and/or tungsten (W/C1.6) have increased microhardness and improved frictional characteristics compared with the conventional coating.

Electrospark deposition (ESD) was employed to clad WC-10%Co hard alloy on steel 1035 and the tribological properties of the coatings obtained were examined. The influence of the duration and frequency of discharges, the nature of the environment, and the carbon concentration in the electrode materials on the decarburization of tungsten carbide was studied. It is shown that the degree of tungsten carbide degradation can be reduced by decreasing the discharge frequency and increasing the concentration of carbon in the WC-Co electrode materials and also that the WC decarburization reaction is reversible on annealing.

Coatings containing Ti-Al intermetallics are fabricated by the electrospark deposition of titanium on aluminum and aluminum on titanium. The microstructure and composition of the grown coatings is studied by scanning electron microscopy, X-ray diffraction, and S-ray microanalysis. It is found that the surface layer formed in argon mostly contains the α-TiAl3 intermetallic independent of the duration and frequency of discharge pulses. The γ-TiAl and α2-Ti3Al phases can be obtained by aluminum deposition on titanium followed by the subsequent deposition of a second titanium layer. Aluminum oxide and titanium nitride are additionally formed during the deposition of electrospark coatings in air.

The structure and properties of coatings based on WC-Co alloys containing additives of 1% - 5% aluminium oxide and 2.5% - 4.5% carbon were investigated. The coatings had a nanocrystalline structure. Depending on the duration and frequency of the discharge pulses, the ratio between WC and W2C in the coatings was different. The additives in the hard alloy allowed us increase the microhardness and wear resistance of the coatings by a factor of 2 - 3 in comparison to coatings created using a conventional WC-10%Co alloy.

Photocatalytic activity, optical properties, thermal stability, phase patterns and morphology of nano-size ТiО2/WO3 compositions obtained from organic precursors through hydrothermal synthesis have been studied. It has been shown that doping of anatase nanoparticles with tungsten W+6 results in particle diameter reduction from 35 to 10 nm; decrease in width of the band gap from 3.15 eV to 2.91 eV and increase in temperature of phase transition of anatase to rutile up to 980оС. Catalytic activity of ТiО2/WO3 (4 mol.%) composition under photochemical methylene blue (MB) oxidation by simulated solar light exceeds that of undoped anatase (obtained in the same way) 6-fold.

In the electrospark deposition (ESD) of WC-Co materials on low carbon steel, tungsten carbide (WC) decarburization is observed. The use of an inert atmosphere (argon) does not eliminate the problem of tungsten carbide decarburization during electrospark processing. The effect of the carbon concentration of electrode materials on the phase composition and mechanical properties of WC (10 wt% of Co) ESD coatings has been investigated in this work. The introduction of additional carbon (graphite) in the electrode material on the basis of the WC-10%Co leads to an increased amount of WC in the obtained coatings and thus improves their wear resistance.

The results of studying the formation of coatings by electrospark alloying with the use of an electrode material based on the VK8 tungsten-containing alloy with the addition of an aluminum oxide nanopowder are presented. It is shown that introducing Al2O3 into the hard alloy promotes an increase in the mass transfer coefficient, microhardness, and wear resistance of the formed coatings. The duration of electric discharges exerts a significant effect on the phase composition of the alloyed layer.

The surface of copper cathode foils with thicknesses up to 50 μm has been studied after a single discharge current pulse with an amplitude of up to 60 A and a pulse duration within 50–1300 μs in air at atmospheric pressure. It is established that the foil surface upon discharge is covered by copper nanoparticles with diameters above 30 nm, which form an ordered array with a cellular structure and dimensions of up to several hundred nanometers. A possible mechanism of this self-ordered structure formation is qualitatively described.

Experimental evidence is presented that the growth of tungsten whiskers during CO reduction of NiWO4 follows the vapor-liquid-solid mechanism. A liquid phase appears at 940°C owing to the melting of NiWO4-Na2WO4 eutectic regions which seem to result from the segregation of sodium impurities present in the reagents used. The presence of the liquid phase ensures comparable rates of Ni and W liberation from the crystal lattice of nickel tungstate, leading to the formation of α-W + NiW two-phase regions. The directional growth of tungsten whiskers during further CO reduction of the tungstate melt is associated with W deposition on the growth surfaces of α-W single crystals in the two-phase regions.

The microstructure and phase composition of a copper foil subjected to single low-voltage discharges of different duration and power have been studied. It was found that the grain size decreases from 200 μm to 10 nm with approaching the center of the discharge-affected zone. The electron-microscopic examinations showed that the compounds formed by electrode materials and oxygen were regularly distributed depending on the distance from the center of the discharge-affected region.

A circuit and the structural features of apparatus for the synchronous recording of the electrical and optical characteristics of spark discharges, which occur between two electrodes at low voltages, are described. The parameters are recorded in digital form with a discreteness of 4 μsec.

The possibility of attaining critical transitions in metals depending on the nature, intensity, and time of action of a concentrated energy flux (laser radiation, spark discharge) is analyzed. A criterion of erosion resistance based on critical constants is proposed.