Vol 8, No 2 (2017)

Thin films of Mo(Ni)Se_x are synthesized using pulsed laser deposition (PLD) in a special mode of operation in which the laser ablation of a Mo(Ni)Se₂ target releases a mixed deposition flux consisting of atomic Mo, Ni, and Se and Mo droplets. The size of deposited Mo particles is in the range of 20–100 nm. Incorporation of amorphous carbon phase (a-C) in some Mo(Ni)Se_x films is achieved by using a graphite target along with a Mo(Ni)Se₂ one and depositing the ablation plume of the former. The films are deposited on graphite and glassy carbon substrates and some are subjected to thermal treatment at 550°C. Electrochemical testing for catalytic activity toward hydrogen evolution reaction (HER) and characterization of the structures are performed for both thermally processed and unprocessed samples. Annealing is shown to cause the formation of structures with the inclusion of ultrafine sheetlike MoSe₂ crystals. Incorporation of carbon in the films suppresses the growth of the nanosheets during annealing. However, enhancement of HER in an acidic solution is also observed for samples with quite minor amounts of the nanosheets, which can be attributed to peculiarities of structurization of Mo(Ni)Se_x and Mo(Ni)Se_x/a-C layers obtained by PLD.

Design, manufacture, and test results are presented for laminated metal-polymeric hybrid fragments of a wing panel made of high-strength aluminum-lithium alloy V-1469T1 and of single-directed laminated aluminum fiberglass SIAL-1-1R. It is shown that the principle “material–technology–structure” can be implemented, and we demonstrate it by example of designing the fragment of a hybrid wing panel beginning from choosing the optimal structure material for the stringer and the structure of hybrid skin and finishing by testing large-sized structure-like samples. We show that the results of strength calculations for fragments of the hybrid wing panel demonstrate good convergence according to static and repeated static tests of panel fragment. Calculations are performed according to different methods, including the finite element method. We show that the hybrid structures are better than the traditional structures made of aluminum alloys according to weight efficiency, which can run up to 10%, and according to bearing capacity, which can run up to 20%.

Cathode materials in the form of complex metal oxides LiNi_xMn_yCo_1–x–yO₂ (0.3 ≤ x ≤ 0.6; 0.2 ≤ y ≤ 0.4) obtained by different methods, such as a solid state method and a method of thermal destruction of organometallic compounds in oil, are studied. The results of the elemental analysis, TGA/DSC, XRD, SEM, TEM, and electrochemical tests are presented. It is found that complex metal oxides obtained by the method of thermal destruction of organometallic compounds in oil are composed of primary nanocrystallites (up to 100 nm) coated by a nanoscale carbon layer that can significantly improve the electrochemical characteristics of the basic lithium-ion battery based thereon.

A method is developed for the preparation of mixed pentoxide Nb_2(1–y)Ta_2yO₅ by rapid coprecipitation of a mixture of hydroxides of niobium and tantalum from a solution of hydrofluoric acid by ammonia water, followed by purification and calcination of the precipitate. The proposed method allows obtaining a homogeneously mixed pentoxide of niobium and tantalum Nb_2(1–y)Ta_2yO₅, in contrast to the method of obtaining Nb_2(1–y)Ta_2yO₅ from a mechanical mixture of individual pentoxides of niobium and tantalum. The temperature dependences of the real part of the permittivity (ε′) of ceramic samples of Nb_2(1–y)Ta_2yO₅ at various frequencies were investigated and the magnitude of dielectric loss (tan(δ)) versus frequency measurement of the electric field and temperature was evaluated. On the basis of analysis of the data of impedance spectroscopy, the temperature dependence of the static conductivity σ_dс of the ceramic Nb_2(1–y)Ta_2yO₅ was determined. From the temperature dependence of σ_dс, the enthalpies of activation of charge transport for different temperature ranges were evaluated.

Nanocrystalline powder (~20 nm) with the composition of (ZrO₂)_0.6(In2O3)_0.04 is synthesized on the basis of a co-precipitation method. After its consolidation, a dense and porous ceramic matrix for supercapacitor electrodes is obtained. The deposition conditions are determined for thin nanocarbon and MnO₂, Co₃O₄ layers on the porous ceramic or metal matrix. It is shown that the model supercapacitor with composite electrodes based on nickel foam and thin layers of nanocarbon and MnO₂ has the highest average specific capacitance.

The amorphous structure of aluminum alloy doped with transition (Fe, Ni) and rare earth (La) metals crystallizes with the formation of a multiphase nanocrystalline composite under irradiation with fast 38-MeV ¹²C⁺³ ions at a fluence of Φ = 5 × 10¹⁶ particles/cm². The microhardness of the irradiated amorphous–nanocrystalline composite is higher than that of the unirradiated amorphous alloy. No phase transformations are observed in the polycrystalline state. The morphology of phases slightly changes owing to partial dissolution and coagulation of intermetallic compounds.

Chemical analysis of phases and inclusions in a specimen of Ti–5Al–4V–2Zr titanium alloy in the initial state and after irradiation with titanium ions up to the radiation damage dose of ~1 dpa at 260°C was carried out and the microstructure was studied. Microstructural analysis was performed by the methods of transmission electron microscopy, energy dispersion X-ray spectroscopy, and atom probe tomography. Results of the chemical analysis of the matrix α phase and inclusions of β phase grains are given. It is shown that the α phase is enriched in aluminum up to 10 at % and the β phase is enriched in vanadium up to 20 at % in the initial state in the Ti–5Al–4V–2Zr alloy. Heavy ion irradiation induces the formation of dislocation loops of 3 to 12 nm with the number density of ~10²² m^–3. A high number density (up to ~10²⁴ m^–3) of nanoscale precipitations with the average size of ~2 nm is formed during alloy irradiation in the α phase.

The process of formation of matrix structures (matrices) from bioresorbable triblock polyethylene glycol and poly-ε-caprolactone copolymers with different molecular weights, as well as their composites with finely divided hydroxyapatite (particle size is about 1 μm), was developed and studied with thermal extrusion three-dimensional printing. The internal structure and surface morphology of the matrices obtained were investigated with optical and scanning electron microscopy. The effect of extruder temperature and flow rate of a polymer melt through the extruder on molecular weight distribution of the starting copolymers and formation of solid-state microstructures from them was studied with gel permeation chromatography

Plasma spraying of composite coatings is developed and investigated. Three-dimensional capillary porous titanium (3DCP Ti) coatings with a thickness of 1 mm are sprayed using a wire. Hydroxyapatite (HA) coatings with a thickness of 0.08–0.35 mm are sprayed on 3DCP Ti coatings at a temperature of 300–550°C. The joint between the coating and plastic is analyzed at shear. The plastic simulates bone tissue that grows into the coating surface. The heating of the 3DCP Ti coating to 550°С when the HA coating is being sprayed increases the shear strength of the coating with respect to the plastic to 9.8 MPa. Modeling approximations are proposed for the shear of the joint between the coating and the plastic.

The paper describes the investigation of the effect of functionalized carbon 1D nanostructures (single- or multiwalled nanotubes, nanofibers with a relatively smooth or highly disordered outer surface) on the level of interfacial interactions in filled vulcanizates. It is found that functionalization of nanoparticles with carbon black is accompanied by formation of hybrid structures in phase of filler that leads to increasing vulcanizate stiffness. Functionalization of nanoparticles by polyfunctional polymers increases the level of interfacial interactions on the vulcanizate-textile cord border without deterioration of the complex of elastic-strength properties.

The mechanism and the kinetics of the oxidation in an air flow of powdery Nb–Si eutectic alloy containing (wt %) 93.0 Nb, 6.7 Si, and 0.27 B are studied by X-ray diffraction (XRD), thermogravimetric (TG), and differential thermal analysis (DTA). The oxidation of alloy proceeds through three stages. At the first stage (600–923 K), the oxidation of a Nb_ss solid solution (with the formation of Nb₂O₅, NbO_0.76, NbO, and NbO₂ oxides) and boron (to B₂O₃) released during the conversion of the Nb₅Si_3–xB_x phase (T₂ phase) into Nb₅SiB_y (D8₈) occurs. At the second stage (923–993 K), the accumulation of the product layer and the formation of borosilicate occur, which prevents the oxidation. At the third stage, Nb₃Si and Nb₅SiB_y (D8₈) silicides and Nb₃B₂ niobium boride are oxidized. Under heating above 1023 K, the interaction of boron oxide with niobium oxide occurs with the formation of Nb₃BO₉. The possible oxidation mechanisms are considered. It is shown that are well described by the model of three successive stages, each one limited by the kinetic regime.

Austenite stainless steel produced by metal injection molding (MIM process) is studied, including its structure, phase composition, and mechanical properties of initial feedstock and sintered material. Prepared feedstock consists of cylindrical granules with the diameter of approximately 3.5 mm. The main feedstock material is a mixture of chrome-nickel and steel powders. Polyacetal is used as a plastic binder. Upon sintering of the feedstock, the material is synthesized with chemical composition, structure, and mechanical properties similar to those of austenite stainless steels. The material density after sintering is higher than 98% of theoretical value. It is established that, upon sintering, a phase transformation occurs: the initial ferrite phase is transformed into the austenite phase. The phase transformation is promoted by nickel contained in initial powder mixture. The microhardness of the sintered material is 1.6 GPa; the elastic modulus is 115 GPa.

The study aimed at revealing the main interaction regularities of powder mixtures of tungsten with a polymeric polytetrafluoroethylene matrix (PTFE) in shock-wave consolidation in cylindrical recovery fixtures. Three powder compositions based on tungsten and Teflon were subjected to shock-wave treatment: a two-component one (W + PTFE) and ones with Al and Ti + B additives. Two types of cylindrical recovery fixtures were applied: ones with continuous filling and ones with a central rod. A significant effect of the “activating” additives (Al, Ti, B) on the initiation and the process of the chemical reaction in the powder mixture and the final phase formation was experimentally shown.

The effect of additional annealing on the structure and mechanical properties of the titanium VT6 alloy in the submicrocrystalline state is studied. It is shown that the annealing at 833 K for 20 min does not significantly affect the mechanically properties of the alloy at room temperature. However, this annealing severely deteriorates the superplastic properties of the alloy. Annealing at 873 K for 5 min results in a sharp decrease in the strength properties of the alloy at room temperature (by about 20%). Nevertheless, the superplastic properties of the alloy after this annealing are the highest ones among those considered in this work. It is assumed that the state of grain boundaries plays the decisive role in the development of the superplastic flow of the VT6 alloy after three-dimensional pressing and subsequent annealing.