Inorganic Materials: Applied Research最新文献

The effect of multi-axis forging (abc pressing) at 300°C on the temperatures of martensitic transformations and inelastic properties (effects of superelasticity and the shape memory) is explored in Ti_49.8Ni_50.2 (at %) alloy samples. It is found that the temperature of the onset of direct martensitic transformation B2 → R remains virtually the same after abc pressing. This temperature is equal to 63 ± 1°C. At the same time, the temperature of the end of the direct martensitic transformation to the B19′ structure decreases by 41 ± 1°C. The temperatures of the beginning and the end of the reverse martensitic transformation B19′ → B2 decrease by 18 and 13°C, respectively. It is found that, after abc pressing at 300°C, the alloy samples retain inelastic properties, having values (regardless of the given true strain e) comparable with the value of the inelastic properties of the coarse-grained samples. In all samples under study, the maximum value of the reversible inelastic strain reaches ~18% and is observed at 16–24% of the determined plastic torsional strain.

Abstract—The effect of irradiation with pulsed helium ion beams and helium plasma on the structural characteristics and mechanical properties of titanium alloys with the following compositions (wt %): Ti–0.5 Nb–0.5 Mo–3 Zr–3 Al; Ti–1 Nb–1 Mo–3 Zr–3 Al; and Ti–1.5 Nb–1.5 Mo–3 Zr–3 Al was investigated. The irradiation was carried out using a Plasma Focus type device with power flux densities of q = 2 × 10⁸ W/cm² for helium ions and q = 4 × 10⁷ W/cm² for helium plasma, with pulse durations of 20–100 ns. Metallographic and X-ray phase analyses were performed and the mechanical properties (ultimate strength, yield strength, and elongation) and microhardness of the alloy samples before and after irradiation were determined. The irradiation caused a slight (less than 10%) decrease in the strength and plasticity indicators of the alloy samples, while the microhardness remained practically unchanged.

Two methods of liquid-phase synthesis—coprecipitation of hydroxides and co-crystallization of nitrate salts—are used to synthesize highly dispersed mesoporous powder samples. The samples have the following composition: (CeO₂)_1–x(Dy₂O₃)_x (x = 0.05, 0.10, 0.15, 0.20) with a specific pore volume ranging between 0.028 and 0.086 cm³/g and a specific surface area of 22.68–66.32 m²/g. The powder obtained is used to make ceramic nanomaterials having designed composition. These are cubic fluorite type solid solutions having a coherent scattering region (CSR) of ~78–91 nm (1300°C). The open porosity varies between 2 and 14%. The apparent density is fairly high (5.87–7.05 g/cm³). Different effects of synthesis conditions influence the physics and chemical properties of the ceramic electrolyte materials. It is shown that the synthesis used to obtain sintering additive ZnO for ceramics controls open porosity and density in different manner: the open porosity drops 3–5 times and the density increases when the salt co-crystallization technique is used. However, it is shown that the porosity exhibits a decrease by 2 times in the samples synthesized using the hydroxide coprecipitation method, which confirms the selective effect of sintering additives. The new ceramic materials have physical and chemical properties (density, porosity, and coefficient of thermal expansion) making them promising for applications as solid oxide electrolytes in medium-temperature fuel cells.

Multilayer coatings consisting of nanocrystals with layered atomic packing, in which planes with dense atomic packing are combined into a crystal through weak van der Waals interaction, were created by alternating pulsed laser ablation of MoS₂ and WSe₂ targets in vacuum conditions. Deposition on a substrate heated to 400°C caused both the crystallization of the layers and the formation of the WS₂ phase at the layer interfaces. As a result of the peculiarities of pulsed laser ablation of the selected targets, the van der Waals matrix of the layers contained metal nanoinclusions (bcc-Mo and β-W). The tribological properties were studied by sliding a steel ball over the coating at low relative humidity. The coefficient of sliding friction decreased with increasing load on the counterbody down to an ultralow value of 0.01. The friction caused some disordering of the crystalline structure of the layers and mass transfer in the contact area of the coating. The low value of the friction coefficient could be due to the difference in the packing parameters of atoms in the basal planes of molybdenum and tungsten dichalcogenides, accumulating in the tribofilm and determining the shear stresses of the atomic layers at local interfaces during counterbody sliding. Metallic nanoparticles could influence the tribo-activated modification of the nanostructure and the composition of the coating in the tribofilm.

Abstract—The parameters of micromodules for thermoelectric generators used at low heat fluxes have been calculated. For the branches of micromodules, our own developments of fine-crystalline materials based on the Sb₂Te₃–Bi₂Te₃ solid solution of p-type conductivity and the Bi₂Te₃–Bi₂Se₃ solid solution of n-type conductivity obtained by hot pressing and extrusion of powders prepared by grinding an ingot and by the melt rapid crystallization methods, that is, by melt spinning and crystallization of melt in a liquid, are considered. Calculations of the dependence of micromodule power on the temperature difference, thermoelectric properties (the Seebeck coefficient, specific electrical conductivity, and thermal conductivity) of p- and n-branch materials, their number, cross-section, and height at the cold junction temperature of 17°C have been carried out. It was found that the generated power of the module is directly proportional to the cross-sectional area and inversely proportional to the height of the module branches.

The results of hardening modification of cured polymer composite materials in a microwave electromagnetic field have been analyzed. It has been shown that a necessary factor for obtaining the desired effect is a combination of the energy flux density and exposure time, which ensure heating of a material to a temperature of 60–80°C. Drawbacks of the microwave modification in electron beam chambers with sequential emitters have been noted and the microwave hardening modification of large-sized polymer composite products by discrete movement (scanning) of a horn emitter over the product surface with a delay at each scanning step has been proposed. The temperature field distribution over the irradiated surface at different scanning schemes has been experimentally investigated. A rational value of the overlap of the radiation pattern areas with the maximum energy flux density at each scanning step has been found to be 25%, which ensures uniform heating of the product surface with a spread of no more than ±5°C and eventually makes it possible to implement a uniform distribution of the mechanical properties of the modified structure.

The influence of lithium and tin additives on the mass transfer of diffusing elements during the formation of coatings using diffusion metallization technology from a medium of low-melting liquid metal solutions is examined. It is revealed that the addition of lithium and tin leads to the intensification of the coating formation owing to an increase in the activity of the transport melt. Lithium promotes the reduction reaction of oxide films, which allows for an increase in the intensity of mass transfer and coating formation. The leading role in the removal of oxide films, in the presence of tin in transport melts, is played by the adsorption effect and dispersion of the oxide film under the action of the melt.

Castings based on a ceramic suspension containing 80 wt % VK94-1 powder were produced using the gel casting method. A gel-forming agent system based on acrylamide (the main monomer) and methylene bisacrylamide (the crosslinking monomer) was used. The sintered ceramic is characterized by a fine crystalline structure with a grain size of 2–8 μm and a uniform distribution of glass phase layers, with a relative density of up to 93% and an ultimate bending strength of up to 332 MPa.