Inorganic Materials: Applied Research最新文献

The physical, mechanical, and thermal properties of new nonwoven materials based on heat-resistant fibers were studied. An analysis of existing nonwoven materials of various fibrous compositions, as well as effective water-repellent compositions, was carried out. A technique has been developed for the production of hydrophobized nonwoven materials using solutions of fluorine-containing latex. Bulk density values of samples were determined, thermogravimetric analysis was carried out, mechanical properties (values of breaking load and elongation at break), water absorption, and other technical characteristics of the developed material were studied, and an experimental batch was manufactured.

New technologies of microelectronics are emerging to reduce the size of devices and combine them into more compact ultralow power systems. Betavoltaic power sources (BVPSs) can serve as power generators of such order. BVPSs consist of a combination of betavoltaic cells (BVCs) based on long-lived radioisotopes of beta radiation and semiconductor converters (SCs). One of the key tasks for increasing the power of BVCs is the selection of SCs that can efficiently convert the energy of beta particles into electricity. Currently, semiconductor structures with a developed surface and a high band gap are considered to be perspective SCs. In present work, arrays of titanium dioxide nanopores (TiO₂ NPs) synthesized by common electrochemical anodization were chosen as a SCs. These SCs were part of BVCs based on nickel-63 with an activity of ~10 Ci/g. TiO₂ NPs with an amorphous structure in the composition of BVC demonstrated low electrical parameters. To increase them, we modified TiO₂ NPs by the hydrothermal method in a solution of Sr(OH)₂ with a concentration of 0.05 mol/L at various times. These experiments were carried out in order to convert TiO₂ (anatase) into structure-like SrTiO₃. We found that the electrical parameters of the SCs increased with the duration of the modification time. The best result was obtained in the case of modification for 3 h—the BVC generated a short circuit current of 2.9 nA and open circuit voltage of 0.8 V and had a maximum power of 0.8 nW at 0.45—0.5 V. The obtained electrical parameters in combination with the miniature dimensions of the BVCs open up the potential possibility of creating a BVPS with an increased power density.

The potential of improving the impact strength and reducing the density of carbon-fiber-composite products (CFCs) is explored as a function of the content of introduced ultra-high-molecular-weight polyethylene (UHMWPE) roving. The roving feature high tensile and impact strength and low density. The carbon fiber composite consists of carbon-fiber (CF) roving. It is additionally reinforced using D800 and SK75 roving with UHMWPE fibers. CF and UHMWPE roving are mixed in different ratios to make unidirectional hybrid (three-component) samples in two types of epoxy matrices (HT-2 and L285). In addition to hybrids, two-component samples are made using individual CF, D800, and SK75 roving. The amount of roving in the volume of hybrid samples is changed with a 25% increment to obtain CF and UHMWPE roving ratios of 0.25/0.75, 0.50/0.50 and 0.75/0.25. The required quantity of roving having the above ratios is calculated using the CF and UHMWPE roving constants. The impact strength, density and bending strength are estimated. The density of the samples is determined by calculation accounting for the roving constants. The results of the strength tests in hybrids are compared with CFC strength indicators. When the amount of UHMWPE roving increases, the bending strength and the density of hybrids decreases at different rates if compared to CF. The impact strength sharply increases under the same conditions followed by a sharp decline. The density of hybrids decreases by about 8% with each incremental step, and the rate of bending strength decline is approximately twice the rate of the density decrease. The impact strength of hybrids containing 25 and 50% UHMWPE roving shows an average increase by 3.28 and 3.4 times, respectively.

The effect of sequential action of pulsed helium ion and helium plasma flows on low-activated austenitic 25Cr12Mn20W chromium–manganese steel samples cut from a hexagonal pipe preirradiated with the deuterium ion and deuterium plasma flows in different modes at the Plasma Focus PF-1000 facility has been studied. Two deuterium irradiation modes have been implemented: a relatively soft mode with a power density of q ~ 10⁷–10⁸ W/cm² and a hard mode with q ~ 10⁹–10¹⁰ W/cm² with a pulse length of τ = 100 ns and number N = 4 of pulse discharges in both cases. It has been shown that the effect of the helium ion and helium plasma flows at the PF Vikhr facility with irradiation parameters of q ~ 10⁷–10⁸ W/cm², τ = 100 ns, and N = 15 on the inner surface of a steel pipe sample depends on the mode of its preirradiation with deuterium ion and deuterium plasma flows. In the relatively soft mode of pre-exposure to deuterium ion and deuterium plasma flows with a power density of q ~ 10⁷–10⁸ W/cm², the subsequent pulsed irradiation with helium causes slight changes in the damageability of the surface layer: smoothing of the wavelike surface relief, an increase in pore formation in the surface layer, appearance of microcracks in it, and formation of spherical particles consisting of basic and impurity elements of the steel composition. The presence of niobium deposited from the anode of the PF facility has also been observed. The impact of the helium ions and helium plasma flows on the inner surface of a steel pipe sample after its preirradiation with deuterium ion and deuterium plasma flows in the hard mode at q ~ 10⁹–10¹⁰ W/cm² increases the damageability of the surface layer. Implantation of helium into the material facilitates an increase in the number and size of open cavities (tens of microns) emerging in the surface layer at the stage of preirradiation of the pipe with deuterium, formation of numerous small (up to ~5 μm) bubbles and pores in it, and emergence of spherical particles of different phases on the irradiated surface. An increase in the damageability of the surface layer in the investigated steel sample after its subsequent pulsed irradiation with helium is accompanied by a significant increase in the intensity of erosion of the material as compared with the situation implemented in the softer mode of pre-irradiation of the sample. The enhanced erosion leads to a noticeable decrease in the content of niobium deposited onto the irradiated surface.

Scanning electron microscopy and X-ray diffractometry are used to study the coating layer deposited on a CuSn10Pb10 bronze surface through electric spark machining with anode material having similar composition. X-ray studies of the phase composition indicate the presence of copper–tin phases (Cu, α-(Cu; Sn), Cu₃Sn, ε-Cu₃Sn, and Cu_5,6Sn) and lead. The ratio of intensities of diffraction maxima illustrates the absence of a predominant growth (texture) orientation in the coating obtained through electric spark deposition. Scanning electron microscopy data prove that the surface coating layer contains melted areas, pores, spherical and oval inclusions, irregularly shaped particles, cracks, rounded pits, etc. The main reason behind melted areas deals with high temperatures developing between electrodes during an electric spark discharge. The appearance of surface fractures can be primarily associated with developing high thermal stresses and mechanical contacts between electrodes. Spherical/oval particles can develop due to interaction of liquid droplets with the cathode substrate surface. Irregularly shaped particles appear as a result of explosive emission from the edges of the erosion crater of the anode material.

Nanoparticles of transition metal chalcogenides are promising materialds for creating fairly cheap and efficient electro- and photocatalysts for producing hydrogen by splitting water. The method of pulsed laser ablation in liquid makes it possible to obtain nanoparticles, whose characteristics depend on the chemical nature of the ablated targets and the composition of liquid. Nanoparticles obtained by ablation of a WSe₂ target with nanosecond laser pulses in water and isopropyl alcohol are studied. The size of the nanoparticles varies in the range from ~20 to ~200 nm. During laser ablation in water, the formation of tungsten oxide nanoparticles dominates. Nanoparticles obtained by laser ablation in alcohol contain nanophases with different valences of tungsten: W⁶⁺ (WO₃), W⁵⁺ (W–Se–O), W⁴⁺ (WSe₂), and W⁰. No obvious signs of carburization of these nanoparticles are found. In both cases, selenium not reacted with tungsten is released in the form of a crystalline and/or amorphous nanophase. The possibility of applying the created nanoparticles as photocatalysts for the hydrogen evolution reaction is analyzed.

A new type of separation materials for alkaline water electrolyzers has been obtained: a diaphragm synthesized by the phase inversion method and a multilayer microfilm membrane with zirconium hydroxide hydrogel as a hydrophilic filler. Experimental data on their porosity, electrical conductivity, and gas density, as well as the results of their tests as part of an alkaline electrolyzer battery are presented in comparison with a porous diaphragm based on polysulfone with a hydrophilic filler (TiO₂), synthesized by the traditional phase inversion method. The advantages and disadvantages of new materials are assessed, and ways for further research and development are determined.

The article presents the results of high-temperature gas and salt corrosion of a heat-resistant nickel alloy on an automated installation at temperatures of 750 and 850°C, a gas flow velocity of 270 m/s, and the supply of synthetic sea salt or a mixture salts of Na₂SO₄–NaCl (at a ratio of 3 : 1) as corrosive-active agents. It has been established that, with an increase in the number of heating/cooling cycles and the temperature of corrosion tests, the nickel alloy damage increases. As a result of corrosion tests when supplying an aqueous solution of synthetic sea salt and at temperature of 750°C, it was established that formation takes place of micrograined layers of magnesium oxides, which are products of thermohydrolysis of MgCl₂, on the surface sample of the nickel alloy. When the test temperature increases to 850°C, the process of thermohydrolysis of sea salt components is accompanied by the formation of oxide deposits with an abnormally high cobalt content. The increase in cobalt content in oxide deposits is caused by the action of the sea salt component NaCl. It has been established that a mixture salts of Na₂SO₄ and NaCl has the greatest negative effect on the alloy than salt corrosion caused by the action of synthetic sea salt. At the same time, the areas of intense corrosion were observed on the alloy surface and thinning-out of the sample working part due to spalling of brittle oxide deposits.

An metal–intermetallic material based on the combustion products of the layered system (Ti–Al–Mg)/Ti was first obtained using the self-propagating high-temperature synthesis (SHS) combined with pressing. Exothermic synthesis from elemental powders was carried out at a pressure of 10 MPa, and the hot product of synthesis was pressed at a pressure of 250 MPa. It was demonstrated that the SHS pressing process results in an inseparable bond between the “intermetallic/metal” layers. The main features of microstructure formation, phase composition, and strength properties of the transition zones at the interface between the reacting SHS compositions Ti–Al–Mg and the Ti substrate were investigated. The thickness of the transition zone between the layers was at least 15 μm. Energy-dispersive analysis (EDA) showed that Mg in the synthesized alloy is mainly located in intergranular layers, in the form of a small amount of Ti–Al–Mg compound, indicating incomplete reaction diffusion between the Ti–Al and Al–Mg layers. The microhardness of Ti–Al grains in the synthesized alloy is 5820 MPa on average, while that of the matrices based on Al–Mg is 3980 MPa. The hydrostatic density is 3.3 g/cm³, with a porosity of less than 13%. The porosity of the Ti–Al–Mg alloy obtained by the SHS pressing method was reduced by three times.

The possibility of forming carbides of the (Ti,Cr)_xC_y type in the Ti₆Al₄V alloy by the method of direct laser deposition of materials (DLD) is shown. A new method for the synthesis of carbides of the (Ti,Cr)_xC_y type consists in preliminary laser cladding of carbon fibers with chromium, adding them to the VT6 powder mixture, and fusing the resulting DLD composition. Thus, a new Ti₆Al₄V/CFs/Cr alloy was obtained. The formation of carbides of the Cr_xC_y type was revealed in the coating on carbon fibers (CF/Cr). The appearance of Cr_xC_y carbides in CF/Cr samples is due to the interaction of carbon with chromium as a result of laser processing. The average microhardness of the Ti₆Al₄V/CFs/Cr alloy was 700 ± 100 HV_0.01. At the same time, the hardness of the detected carbides (Ti,Cr)_xC_y in the Ti₆Al₄V/CFs/Cr alloy was 1000 ± 40 HV_0.01. During the DLD process, the carbon fiber can be completely or partially dissolved. In the composite material Ti₆Al₄V/CFs/Cr, carbides (Ti,Cr)_xC_y are formed. It is shown that the hardness of the detected carbides is 2 times higher than the hardness of the composite material. It has been established that the friction coefficient of the VT6 alloy under increased load decreases by 1.5 times after 20 min of testing, while the friction coefficient of the Ti₆Al₄V/CFs/Cr alloy remains stable and is 0.27 over the entire test interval.