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Behavior of Pt/C catalysts obtained by the platinum deposition on standard and nitrogen-doped carbon supports with different microstructure has been studied in the oxygen electroreduction reaction in an acidic electrolyte. The catalysts based on the modified supports are characterized by a uniform spatial distribution of small-sized (1.5–2 nm) Pt nanoparticles over the surface of the supports, which results in high values of the electrochemically active surface area (110–130 m2 g− 1 (Pt)). The use of various stress testing protocols has shown that the Pt/C material based on the N-doped KetjenBlack EC DJ-600 possesses the highest mass activity and durability, which noticeably exceed the corresponding characteristics of the commercial HiSPEC3000 catalyst.

Dispersoid hardening is a key factor in increasing the recrystallization resistance and mechanical strength of non-heat treatable aluminum-based alloys. Mn and Zr are the main elements that form dispersoids in commercial Al-based alloys. In this work, the annealing-induced precipitation behavior, the grain structure, and the mechanical properties of Al-3.0Mg-1.1 Mn and Al-3.0Mg-1.1 Mn-0.25 Zr alloys were studied. The microstructure and the mechanical properties were significantly affected by annealing regimes after casting for both alloys. The research demonstrated a possibility to form high-density distributed quasicrystalline-structured I-phase precipitates with a mean size of 29 nm during low-temperature annealing of as-cast alloys. Fine manganese-bearing precipitates of I-phase increased recrystallization resistance and significantly enhanced the mechanical strength of the alloys studied. The estimated strengthening effect owing to I-phase precipitation was 150 MPa. Due to the formation of L12-structured Al3Zr dispersoids with a mean size of 5.7 nm, additional alloying with Zr increased yield strength by about 90 MPa. The L12-phase strengthening effect was estimated through the dislocation bypass looping and shearing mechanisms.

The effect of scandium on the superplasticity characteristics of Al–0.5Mg–Sc conductor aluminum alloys with a submicrocrystalline (SMC) structure is investigated. Large elongation to failure (~1060%) is achieved in the SMC alloys with 0.4 and 0.5% Sc at a deformation temperature of 500°C and a strain rate of 1 × 10–1 s–1. Intense pore formation is shown to occur during the superplasticity of the Al–0.5Mg–Sc SMC alloys. The kinetics of deformation-stimulated grain growth in the Al–0.5Mg–Sc SMC alloys is found to be determined by the mobility of junction disclinations and orientation-misfit dislocations.

Metallic zirconium based glasses are a new promising family of materials characterized by high strength and comparatively high plasticity in compression tests. In recent years, great attention has been paid to the application of different regimes for the treatment of metallic glasses for the formation of a unhomogeneous amorphous structure to increase the plasticity of these materials. In this study, amorphous Zr62.5Cu22.5Fe5Al10 alloy bands were manufactured by the method of quenching on a rotary copper disk. The effect of hot rolling and further annealing at a temperature of 300°C for 150 min on the structure and properties of these bands was investigated. To study the transformation occurring in their structure as a result of thermomechanical treatment, transmission electron microscopy and X-ray diffraction were used. The effect of thermomechanical treatment on the mechanical properties of bands was studied by measuring the Vickers microhardness. Based on the obtained results, some conclusions about the effect produced by the microstructure of bands on the microhardness of the Zr62.5Cu22.5Fe5Al10 alloy were made. In this study, an abrupt increase in the microhardness was observed after thermomechanical treatment, due to the formation of nanosized uniformly distributed areas in the structure.

t—The diffusion welding of ultrafine-grained pseudo-α-titanium Ti–4.73% Al–1.88% V alloy specimens has been performed by spark plasma sintering. It has been shown that the destruction of welded joints in the ultrafine-grained (UFG) specimens under hot salt corrosion (HSC) conditions has a two-stage character: intercrystallite corrosion (ICC) is developed at the first stage to turn into pitting corrosion at the following stage. It has been established that the resistance to intercrystallite corrosion is governed by the concentration of vanadium on grain boundaries, the size and volumetric content of β-phase particles, and the existence of pores in a welded joint. It has been demonstrated that the welded joints of the ultrafine-grained specimens have higher hardness and resistance to intercrystallite corrosion as compared to coarse-grained specimens.

The effect of the SnO2 nanoparticles content on the structure and electrochemical behavior of Pt/(SnO2/C) catalysts containing about 20 wt% Pt was studied. In this case, SnO2/C nanostructured materials were obtained by tin electrodeposition on the carbon particles in suspension. It was found that the optimal combination of stability and activity in the oxygen electroreduction reaction is demonstrated by materials containing 25–30% wt. SnO2. A comparative assessment of the durability and activity of Pt/(SnO2/C) catalysts and a commercial Pt/C catalyst with 20% Pt-loading has been carried out.

The effect of severe plastic deformation by rotary forging on the mechanical properties and the corrosion resistance of a pseudo-α-titanium PT-7M alloy is studied. The corrosive character of fracture the fine-grained alloy under hot salt corrosion (HSC) conditions is found to change: pitting corrosion at the onset of recrystallization processes changes into intercrystalline corrosion. The HSC resistance of the fine-grained PT-7M titanium alloy is shown to depend on the structure–phase state of grain boundaries, whose intense migration with developing recrystallization leads to “sweeping out” of corrosion-hazardous alloying elements (aluminum, zirconium) from the crystal lattice of the titanium alloy.

The parameters of reversion after hardening aging of magnesium alloys containing two rare earth metals gadolinium (yttrium group) and samarium (cerium group) were determined at various ratios of their contents. The reversion was observed at short annealing at 250 and 300°С beginning with 5 min after preliminary aging at 200°С up to maximum hardening and consisted of significant softening of the alloys then. Measurements of the electrical resistance indicated that during softening the reverse dissolution of the rare earth metals in magnesium-based solid solution takes place with diminution of the quantity of hardening particles precipitated during aging beforehand. The reverse dissolution of the rare earth metals in solid magnesium increases with increase in the annealing temperature after aging from 250 to 300°С and with increase in the gadolinium to samarium ratio in the alloys.

Electrocatalysts based on Pt-M bimetallic nanoparticles deposited on carbon supports have already been used in commercially available Proton Exchanged Membrane Fuel Cells (PEM FC). Nevertheless, production and practical use of such materials faces with the problems caused by the need to combine high specific activity in current-forming reactions and their durability, with the stability of the element's composition during the operation of PEM FC. The suggested stepwise approach to the PtCu/C materials synthesis in the liquid phase is based on the initial deposition of platinum nuclei and their subsequent growth due to the joint or sequential deposition of copper and platinum from the solutions of their precursors. The PtCu/C catalysts, obtained in this way, demonstrated not only higher activity in oxygen reduction reaction compared to the commercial Pt/C catalyst, but also a significantly higher corrosion-morphological stability.

The phenomenon of post-aging retrogression in magnesium alloys containing two rare-earth metals belonging to different groups, i.e., yttrium Y (the yttrium group) and samarium Sm (the cerium group), is investigated. It is shown that retrogression may occur in alloys with different proportions of yttrium and samarium aged at 200°C for maximum hardness and then annealed at somewhat higher temperatures (250 and 300°C). The process is possible due to decomposition of the supersaturated magnesium solid solution. The degree of the retrogression is shown to depend on the temperature and duration of the post-aging annealing and on the yttrium- to-samarium proportion in the alloys.

The thermal stability of the grain structure, the mechanical properties, and the electrical resistivity of submicrocrystalline (SMC) Al–0.5% Mg alloys with 0.2, 0.3, 0.4, and 0.5% Sc is studied. The alloys are fabricated by induction casting and equal-channel angular pressing (ECAP). The alloys with >0.3% Sc contain submicrometer primary Al3Sc particles, the amount of which increases with the scandium content in the alloys. The precipitation kinetics of Al3Sc particles in the SMC alloys is determined by the intensity of diffusion processes along lattice dislocation cores and grain boundaries. ECAP of the alloys at a temperature of 225°C provides high thermal stability of the SMC structure: the temperature of the onset of recrystallization is 375°C. At room and elevated temperatures, the SMC alloys have a high plasticity and a good combination of strength, hardness, and electrical conductivity.

The effect of heat treatment at 1000°C for 400 h on the thermal conductivity of zirconium dioxide crystals stabilized with scandium oxide (ZrO2)1 – x(Sc2O3)x (x = 0.08–0.10) and simultaneously with scandium and yttrium oxides (ZrO2)1 – x – y(Sc2O3)x(Y2O3)y (x = 0.003–0.20, y = 0.02–0.025) has been studied. In the crystals of zirconium dioxide stabilized with scandium oxide, the most noticeable changes in the thermal conductivity are observed in the 9ScSZ crystals, in which the phase composition is changed and a marked content of the rhombohedral phase appears. These changes are less noticeable in the 8ScSZ crystals and they are mainly due to the ordering of oxygen vacancies and the changes in the microstructures of the samples, and there are no changes in the 10ScSZ crystals. The 10ScSZ crystals have the minimum electrical conductivity before and also after annealing, which is determined by the highest content of scandium oxide in the solid solution. Insignificant changes in the thermal conductivity are observed in crystals of partially stabilized zirconium dioxide co-alloyed with scandium and yttrium oxides. The cubic 8Sc2YSZ and 10Sc2YSZ crystals demonstrate only slight changes in the thermal conductivity, the character of the temperature dependence of the thermal conductivity, and the phase compositions. The alloying of the zirconia–based solid solutions with yttrium oxide simultaneously with scandium oxide enables one to increase the stability of their phase compositions and structurally dependent thermal and electrical physical characteristics.

Titanium alloys are widely used as materials for the elements of nuclear power plants, which are subject to high reliability requirements. The goal of the study is to develop X-ray diffraction analysis of the phase composition of α - and near- α -titanium alloys. Surface treatment of the samples of titanium alloys PT-3V, PT-7M and VT1-0 was carried out by mechanical, electrochemical polishing and chemical etching. It is shown that PT-3V and PT-7M alloys are characterized by a mixed structure consisting of α - and α ’-phases with precipitation of submicron particles of the β -phase along the grain boundaries. The results of X-ray diffraction analysis of the samples obtained on an X-ray diffractometer Shimadzu XRD-7000 (Cu K α radiation) were compared with the data of metallography and electron microscopy. It is shown that the results of X-ray diffraction analysis strongly depend on the method, quality and duration of the surface treatment of the samples. Electrochemical polishing and acid treatment reduce the width of diffraction peaks and lead to a more pronounced manifestation of their «fine» structure thus demonstrating the presence of at least two crystalline phases in the alloys. «Splitting» of the main X-ray peaks of titanium is a consequence of the fine structure of primary X-ray radiation ( K α 1,2 -doublet). Presence of «fine» structure of X-ray peaks and correlation between the intensities of different peaks appears to depend essentially on the mode and quality of surface treatment of the titanium alloy thus reducing the reliability of quantitative analysis of the phase composition of titanium alloys without verification of the results by direct methods of studying alloy structure.

In this work we explored the possibility of obtaining single-phase β-Zn4Sb3 material by direct melting and spark plasma sintering (SPS). The effect of the SPS conditions and synthesized material composition on the structure and thermoelectric properties of the material was studied. X-ray diffraction was used for phase analysis, and scanning electron microscopy was used for characterizing the morphology of the bulk samples. We found electro-migration of Zn due to the exposure to DC pulses during SPS at 40 MPa. Zinc electro-migration produced a zinc-excess layer on the sample surface on the cathode side and a zinc-depleted layer, i.e., ZnSb, on the anode side of the sample. We show that an increase in the sintering pressure, and hence a decrease in the electric current passing through the material, produces single-phase β-Zn4Sb3 material in the entire sample bulk, provided the synthesized material contains excess zinc. The highest ZT of ∼ 1.28 at 673 K was obtained for the material synthesized with Zn excess and sintered by SPS at a pressure of 100 MPa.

Cerium is a promising alloying element that may improve the mechanical properties of aluminum-based alloys. However, the effect of Ce on the microstructural and mechanical behavior of complex-alloyed aluminum-based alloys has not been studied well. In this work, we have analyzed the effect of Ce and Fe co-addition on the phase structure, grain structure, and tensile characteristics of the Al-Mg alloy at ambient and elevated temperatures. X-ray and microstructural studies involving scanning electron and transmission electron microscopy methods have been used in order to identify the phase composition of the Al-Mg-Fe-Ce alloy. Two Ce-bearing constituent phases have been identified and their morphology has been analyzed. Uniaxial tensile test experiments were used to study the mechanical characteristics of the samples processed by simple thermomechanical treatment. The Ce- and Fe-modified alloy exhibits fine-grained structure and superplasticity at sub-solidus temperatures, increased yield strength, and good room temperature ductility.

The effects of the Y2O3 and Yb2O3 co-doping impurities on the transport characteristics and stabilization of the cubic phase in solid solutions based on ZrO2–Sc2O3 were compared. The crystals of the (ZrO2)0.99 –x(Sc2O3)x(Yb2O3)0.01 and (ZrO2)0.99 –x(Sc2O3)x(Y2O3)0.01 (x = 0.08–0.10) solid solutions were grown by directed crystallization of the melt in a cold container. The high-temperature cubic phase was stabilized at a total concentration of stabilizing oxides of 11 mol % for (ZrO2)0.99 –x(Sc2O3)x(Y2O3)0.01 crystals and at 10 mol % for (ZrO2)0.99 –x(Sc2O3)x(Yb2O3)0.01 crystals. At (9–10) mol % scandium oxide, the high-temperature conductivity of the crystals co-doped with ytterbium oxide was higher than in the case of the crystals co-doped with yttrium oxide. The (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01 crystals have maximum conductivity over the whole temperature range.

The temperature dependence of the thermal conductivity of cubic ZrO2 single crystals stabilized with yttrium oxide from 8 to 40 mol % has been studied in the temperature range 50–300 K. The dependence is analyzed taking into account the phase compositions, the features of the local structures and the electrophysical characteristics of these single crystals.

The thermal conductivity of single-crystal solid solutions (ZrO2)1 – x – y – z(Sc2O3)x(CeO2)y(Y2O3)z (x = 0.08–0.10; y = 0.005–0.01; z = 0–0.005) was measured in the temperature range 50–300 K. Phase composition and defective structure of crystals were studied.

The results of investigating the crystal structure, ionic conductivity, and local structure of the (ZrO2)1 –x(Gd2O3)x and (ZrO2)1 –x(Y2O3)x (x = 0.04, 0.08, 0.10, 0.12, and 0.14) solid solutions are reported. The crystals are grown by directional crystallization of the melt in a cold container. The phase composition of the crystals is investigated by X-ray diffractometry and transmission electron microscopy. The transport characteristics are studied by impedance spectroscopy in the temperature range of 400 to 900°C. The local crystal structure is examined by optical spectroscopy. Eu3+ ions were used as a spectroscopic probe. The study of the local structure of the ZrO2–Y2O3 and ZrO2–Gd2O3 solid solutions revealed the features in the formation of optical centers, which reflect the character of localization of oxygen vacancies in the crystal lattice depending on the stabilizing oxide concentration. It is established that the local crystal environment of Eu3+ ions in the (ZrO2)1 –x(Y2O3)x and (ZrO2)1 –x(Gd2O3)x solid solutions is determined by the stabilizing oxide concentration and is practically independent of the stabilizing oxide type (Y2O3 or Gd2O3). The maximum conductivity at a temperature of 900°C is observed in the crystals with 10 mol % of Gd2O3 and 8 mol % of Y2O3. These compositions correspond to the t'' phase and are close to the interface between the cubic and tetragonal phase regions. It is found that in the ZrO2–Y2O3 system the highly symmetric phase is stabilized at a lower stabilizing oxide concentration than in the ZrO2–Gd2O3 system. The analysis of the data obtained makes it possible to conclude that, in this composition range, the concentration dependence of the ionic conductivity is mainly affected by the phase composition rather than the character of the localization of oxygen vacancies in the crystal lattice.

The results of investigation of crystal structure, ion conductivity and local structure of solid solutions (ZrO2)1−x(Gd2O3)x and (ZrO2)1−x(Y2O3)x (x = 0.04, 0.08, 0.10, 0.12, 0.14). The crystals were grown by directional crystallization of the melt in a cold container. The phase composition of the crystals was studied by X−ray diffractometry and transmission electron microscopy. Transport characteristics were studied by impedance spectroscopy in the temperature range 400—900 °C. The local crystal structure was studied by optical spectroscopy. Eu3+ ions were used as a spectroscopic probe. The results of the study of the local structure of solid solutions of ZrO2—Y2O3 and ZrO2—Gd2O3 systems revealed the peculiarities of the formation of optical centers, which reflect the nature of the localization of oxygen vacancies in the crystal lattice depending on the stabilizing oxide concentration. It is established that the local crystal environment of Eu3+ Ions in solid solutions (ZrO2)1−x(Y2O3)x and (ZrO2)1−x(Gd2O3)x is determined by the stabilizing oxide concentration and practically does not depend on the type of stabilizing oxide (Y2O3 or Gd2O3). The maximum conductivity at 900 °C was observed in crystals containing 10 mol.% Gd2O3 and 8 mol.% Y2O3. These compositions correspond to the t′′−phase and are close to the boundary between the regions of the cubic and tetragonal phases. It was found that in the system ZrO2—Y2O3 stabilization of the highly symmetric phase occurs at a lower stabilizing oxide concentration than in the system ZrO2—Gd2O3. Analysis of the data obtained allows us to conclude that in this range of compositions the main influence on the concentration dependence of the ion conductivity has a phase composition, rather than the nature of the localization of oxygen vacancies in the crystal lattice.

—A compact powder Ti–22Nb–6Zr alloy was obtained by powder metallurgy methods. The initial alloy powder was synthesized by the calcium hydride method. It was shown that, after consolidation during vacuum sintering and subsequent hot isostatic pressing, the residual porosity of the consolidated material did not exceed 1%. The physicomechanical properties and structural features of the powder alloy obtained were investigated. It was established that, after hot isostatic pressing, there was no release of brittle ω phase in the structure of β-Ti alloy. In the range of heating temperatures of 550–700 K, the β phase was prone to decay with the formation of the α phase of a lamellar morphology and a small amount of the ω phase. The appearance of decay products was accompanied by dilatometric effects and an increase in Young’s modulus. It was shown that, regardless of the method of powder consolidation, the resulting alloy exhibited elinvarity (a small change in Young’s modulus with increasing temperature) in the temperature range of 200–500 K. It was determined that, at room temperature, samples with ~8% pores had Young’s modulus of about 64 GPa; when the porosity level was reduced to

Gold nanoparticles (NPs) were synthesized via chemical (Chem) and radiation-chemical (RadChem) methods for the reduction of ions in reverse micellar solutions (RMS). The gold NP have for the first time been obtained by self-organization (Self-assembly), and their optical properties were evaluated. The formation of Au NP (Chem, RadChem, and Self) was confirmed by the transmission electron microscopy. The spectral characteristics of optical absorption of gold NP in the RMS depend on the solubilization coefficient ω, the salt concentration, and the methods for initiating the primary steps of reduction reactions responsible for the formation of nanoscale structures.

Phase stability and transport characteristics of (ZrO2)1-x(Sc2O3)x(СeO2)y (x = 0.08–0.10; y = 0.005–0.015) and (ZrO2)1-x-y-z(Sc2O3)x(СeO2)y(Y2O3)z (x = 0.08–0.10; y = 0.005–0.010; z = 0.005–0.020) melt-grown crystals have been studied after air heat treatment at 1000 °C for 400 h. Annealing of the (ZrO2)1-x(Sc2O3)x(СeO2)y crystals caused the formation of a rhombohedral phase and reduced the electrical conductivity of the specimens in the entire test temperature range. Yttrium co-doping of the (ZrO2)1-x(Sc2O3)x(СeO2)y crystals stabilized the cubic phase for some compositions. In two-phase (ZrO2)1-x-y-z(Sc2O3)x(СeO2)y(Y2O3)z crystals containing a cubic and a tetragonal phases exhibited conductivity degradation. Annealing of cubic crystals caused the formation of the t'` phase and increased their conductivity.

The study focuses on corrosion fatigue processes taking place in an ultrafine-grained (UFG) near-α-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M) used in nuclear engineering. UFG structure formed with Rotary Swaging is found to increase resistance to corrosion fatigue. Parameters of the Basquin's equation are defined and the slope of the fatigue curve σa-lg(N) is shown to depend (nonmonotonic dependence) on the UFG alloy annealing temperature. This effect can be explained with the patterns of microstructural evolution in a UFG alloy PT7M during annealing: (1) reduced density of lattice dislocations, (2) precipitation and dissolution of zirconium nanoparticles, (3) release of α′′-phase particles causing internal stress fields along interphase (α-α′′)-boundaries, and (4) intensive grain growth at elevated annealing temperatures. It is shown that the fatigue crack closure effect manifested as changing internal stress fields determined using XRD method may be observed in UFG titanium alloys.

The research aims to analyze the impact that severe plastic deformation arising during Rotary Swaging has on mechanical properties and corrosion resistance of a near-α-titanium alloy Ti-2.5Al-2.6Zr (Russian industrial name PT7M). The nature of corrosion decay in fine-grained alloys caused by hot salt corrosion is known to vary from pit corrosion to intercrystalline corrosion at the onset of recrystallization processes. Resistance to hot salt corrosion in a fine-grained titanium alloy Ti-2.5Al-2.6Zr is shown to depend on the structural-phase state of grain boundaries that varies during their migration as a result of “covering” corrosive doping elements (aluminum, zirconium) distributed in the crystal lattice of a titanium alloy.

The aging-induced recovery of binary magnesium alloys with various rare-earth metals (Y, Nd, Sm, Gd, Tb, Dy, Ho), in which the decomposition of the supersaturated magnesium solid solution is accompanied by substantial hardening, is studied. It is found that annealing of the alloys at 250°C, which were preliminary aged at 200°C to a peak hardness, leads to their softening; in this case, the hardness continues to decrease as the annealing time increases. Electrical resistivity measurements show that, as a result of annealing at 250°C, recovery takes place and is accompanied by partial dissolution of the decomposition products in the magnesium solid solution; after that, its decomposition continues. The degree of recovery in the alloys with yttrium-group rare-earth metals (Y, Gd, Tb, and Ho) is found to be higher than that for the alloys with cerium-group rare-earth metals (Nd and Sm); within the lanthanide series, the degree of recovery increases with the atomic number of a rare-earth metal.

Polycrystalline thermoelectric elements of n-type Bi2(Te0.95Se0.05)3 and p-type (Bi0.25Sb0.75)2Te3 were fabricated by modified Bridgman technique, followed by electrospark cutting. A thermoelectric micromodule, consisting of 12 legs with an Ni anti-diffusion barrier and high-temperature SnSb solder between them, was assembled. To investigate thermoelements under conditions close to operating ones, the micromodule was annealed at 443 K for 1000 h. It was revealed that after annealing for more than 40 h, the near-contact zone of the n-type legs degraded, leading to a complete break of the micromodule junctions. Our results revealed that during annealing, the SnSb solder flowed into the unprotected side surface of the legs, and contacted with the cleavage planes along which tin can diffuse into the thermoelement volume. In contrast, the p-type legs were not affected by the contact with the solder. Different impacts of the solder on n- and p-type legs were explained in the framework of density functional theory (DFT) calculations. Substitution, diffusion and thermodynamic stability calculations showed that Bi to Sn substitution is energetically more beneficial than Sb to Sn substitution. Additionally, it was calculated that for the Bi2Te3 + Sn system, it is more beneficial to form a TeSn and Bi phase, while an Sb2Te3 + Sn system is thermodynamically stable.

Low-energy (E = 30 keV) Ag+ ions have been implanted into single-crystalline Si wafers (c-Si) with an implantation dose varying from 1.25 × 1015 to 1.5 × 1017 ions cm–2 and an ion beam current density varying from 2 to 15 μA/cm2. The surface morphology of implanted wafers has been examined using scanning electron microscopy, transmission electron microscopy, and atomic force microscopy, and their structure has been studied by means of reflection high-energy electron diffraction and elemental microanalysis. It has been shown that for minimal irradiation doses used in experiments, the surface layer of c-Si experiences amorphization. It has been found that when the implantation dose is in excess of the threshold value (~3.1 × 1015 ions cm–2), Ag nanoparticles uniformly distributed over the Si surface arise in the irradiated Si layer. At a dose exceeding 1017 ions cm–2, a porous Si structure is observed. In this case, the Ag nanoparticle size distribution becomes bimodal with coarse particles localized at the walls of Si pores.

A bulk nanostructured material based on oxidized silicon nanopowder was fabricated using a spark plasma sintering technique. Structural investigations revealed that this material has the composition of ∼14 nm core Si granules inside an SiO2 shell. Photoluminescence measurements have shown that the emission spectra lie in the energy range of 0.6–1.1 eV, which is not typical of the emissions of the Si/SiO2 nanostructures reported in numerous papers. This result can be explained by the formation of energy states in the bandgap and the participation of these states in both electronic transport and photoluminescence emission. Annealing of the sample leads to a decrease in defect density, which in turn leads to quenching of the 0.6–1.1 eV photoluminescence. In this case ∼1.13 eV inter-band transitions in the Si core start to play a dominant role in radiative recombination. Thus, the possibility of controlling the photoluminescence emission over a broad wavelength range was demonstrated.

A layered metallic hybrid material based on vanadium and zirconium alloys was obtained by high pressure torsion (HPT) at room temperature. HPT of the initial three-layer V-10Ti-5Cr alloy/Zr-2.5Nb alloy/V-10Ti-5Cr alloy billet resulted in a “mixing” of the zirconium alloy layer with vanadium alloy layers. A mixed nanostructure consisting of elongated grains (fragments) with a width of 40–50 nm was formed in the zirconium/vanadium alloy layers of the hybrid. Partial amorphization in the zirconium alloy layer of the hybrid material was found.

The thermal conductivity of single-crystal (ZrO2)1 – x(Sc2O3)x (x = 0.09, 0.10) and (ZrO2)1 ‒ x ‒ y(Sc2O3)x(Y2O3)y (x = 0.003–0.10; y = 0.01–0.025) solid solutions has been experimentally determined in the temperature range 50–300 K. The results are analyzed with allowance made for the phase compositions and features of imperfect crystal structures.

PtCu/C electrocatalysts with similar compositions but different distributions of components in bimetallic nanoparticles were obtained by simultaneous and sequential reduction of copper(II) and platinum( IV) in a carbon suspension. The catalyst obtained by multistage synthesis while sequentially increasing the Pt(IV) concentration in the precursor solution added at each stage showed the highest stability and activity in oxygen electroreduction in acidic media. This catalyst was least liable to selective dissolution of copper during its operation. The influence of the architecture of bimetallic PtCu nanoparticles on the electrochemical behavior of the catalysts is due to the peculiarities of the structure rearrangement of nanoparticles during the enrichment of the protective surface layer with platinum.

We carry out an experimental-theoretical study of the process of the equal-channel angular pressing (ECAP) to obtain a bismuth-telluride-based thermoelectric (TE) material. A brief review of the mathematical modeling of the ECAP process is given, and the effect of the design features and temperature of ECAP regimes on the formation of plastic is studied. The results of calculations of the thermally stressed state of the samples at different stages of the ECAP process are presented. The calculations for the ECAP process are carried out using the Lagrange finite element mesh. During the calculation, the mesh is adjusted to the geometry of the die, becoming rarer or finer depending on the magnitude of the plastic deformation to satisfy the specified calculation accuracy and the convergence of the iterative process. We discuss the results of an experimental study of the structure and properties of the samples obtained with the help of ECAP using various methods (X-ray diffractometry and scanning electron microscopy). The TE characteristics of the obtained materials are measured by the Harman method. Comparative methodological calculations of the ECAP process for a bismuth-telluride-based TE material with a change in the parameters determining the formation of grains are performed (the critical plastic deformation as a function of temperature and the power-law dependence of the rate of this deformation). This allowed us to adjust the design model of the ECAP process using the grain size measurements in the TE material. The results of the calculation of the process of grain formation at different temperatures of plastic molding are presented and compared with the experimental data. The practical result of this research is the improved geometry of the die punch and the validated technological regimes of plastic deformation, which allowed obtaining samples with high TE efficiency values.

Stability is one of the most important characteristics of electrocatalysts used in low-temperature fuel cells with a proton exchange membrane. The corrosion-morphological stability of supported electrocatalysts containing platinum and platinum-copper nanoparticles with ~20 wt % Pt was evaluated under the conditions of voltammetry stress testing corresponding to different degradation mechanisms. The effect of the difference in the architecture of Pt–Cu nanoparticles on the stability of catalysts and changes in their composition as a result of stress tests were studied. At close values of the electrochemically active surface area (ECAS), the carbon-supported bimetallic catalysts demonstrated significantly higher stability compared to the commercial Pt/C catalysts. The Pt(Cu)/C catalyst obtained by sequential deposition of copper and platinum showed the highest resistance to the degradation and selective dissolution of copper during the testing.

—The Cu2 – xSe (0.03 ≤ x ≤ 0.23) powders fabricated by mechanochemical synthesis have been studied by X-ray diffraction. The in situ study has been carried out for the temperature dependences of the lattice parameters, the structures, and the phase compositions of the powders in the temperature range 25–350°C. The powder compositions are shown to differ from the charge compositions and are shifted to lower copper concentrations. The estimation of peak half-widths of the cubic β phase indicates an increase in the structure imperfection after the phase transition from the α phase to the β phase of Cu2 – xSe at ~140°C. It is shown that the superpositions of the subtraction solutions (copper vacancies) and interstitials solutions (copper atoms in interstitial sites), whose proportion is changed as a function of temperature and the deviation from stoichiometry, are in the thermodynamic equilibrium in the copper selenide solid solution at room temperature. The change in the slope of the dependence of the lattice parameter of the powder Cu2 – xSe samples on the composition (0.03 ≤ x ≤ 0.23) in the temperature range 25–350°C enables the suggestion that interstitial copper atom concentration increases with temperature and deviation from stoichiometry.

Kinetics and phase transformations are studied for the previously unconsidered decomposition of supersaturated solid solution in magnesium-based alloys Mg–Dy–Sm. The decomposition of solid solution slows when there is an increase in % Dy: % Sm ratio in the alloys. Mg–Sm and Mg–Dy alloys grow harder when Dy and Sm are added to them, respectively. Products of decomposition in ternary Mg–Dy–Sm alloys are the same as in binary alloys Mg–Dy and Mg–Sm but contain combinations of Dy and Sm.

In this work we report a study of (ZrO2)1−x−y(Sc2O3)x(СeO2)y solid solution crystals (x = 0.08–0.10; y = 0.005–0.015) grown by skull melting technique. The crystal structure of the material was studied using X-ray diffraction, Raman spectroscopy and impedance spectroscopy. The study showed that optically homogeneous and transparent crystals cannot be grown from the melt in the experimental composition range. For overall stabilizing oxide concentrations of above 10 mol% the crystals contained a cubic phase and a rhombohedral one, whereas at concentrations of lower than 10 mol% a cubic and a tetragonal phases coexisted. Ceria introduction into the (ZrO2)1−x(Sc2O3)x system increases its high-temperature ionic conductivity. The highest ionic conductivity was observed in 0.5 mol% ceria containing crystals.

An experimental and theoretical study of the process of the equal−channel angular pressing (ECAP) was performed to obtain a thermoelectric (TE) material based on bismuth telluride. A brief review of the mathematical modeling of the ECAP process is given. The influence of the ECAP design features and temperature modes on the process of plastic forming is considered. The results of calculations of the thermally stressed state of samples at different stages of the ECAP process are presented. The calculations of the ECAP process were carried out by means of Lagrangian finite element mesh, which adjusted adaptively during the process to the die geometry and became finer or coarser depending on the magnitude of the plastic deformation. It was required for the specified calculation accuracy and the convergence of iterative process. The results of an experimental study of the structure and properties of samples obtained by the ECAP using a set of measuring methods (X−ray diffractometry and electron microscopy) are discussed. The thermoelectric characteristics of the obtained materials were measured by Harman method. Comparative methodical calculations of the ECAP process for TE materials based on bismuth telluride have been made by adjusting parameters determining the grain formation (i.e. the critical plastic deformation as a function of temperature and power−law dependence of its rates). It made possible to adjust the ECAP model on the basis of the measured grain sizes for TE materials . The calculation results of grain creation during the plastic forming, which are compared with the measurement data, are presented. The practical result of this research was the improved geometry of the die and the validated technological regimes of plastic deformation, which allowed obtaining samples with the good TE efficiency.

Increasing the recrystallization resistance and the mechanical properties of aluminum-based alloys is possible due to the formation of a nanoscale L12-structured Al3Zr phase. Treatment conditions and alloys composition affect the size and density of dispersoids and their final properties. In this work we analyze the decomposition of the supersaturated solid solution in the as-cast Al-3%Mg-0.25%Zr alloy for different annealing modes to understand the precipitation kinetics of the Al3Zr phase in the presence of Mg. We found that both discontinuous and continuous precipitation mechanisms of the Al3Zr phase are possible in the studied low-alloyed material. One-step annealing leads to the formation of coarse (17 nm) spherical precipitates of a coherent L12-structured Al3Zr phase and discontinuously formed fan-shaped aggregations of the same phase. Two-step annealing provided for the maximum precipitation hardening with the formation of high-density nanoscale (7 nm) dispersoids of the Al3Zr phase. This study highlights the importance of the annealing mode of the as-cast material for achieving a high density of the fine L12 structured Al3Zr phase and the maximum hardening effect.

A layered hybrid material is prepared by high-pressure torsion of a three-layer (vanadium alloy–zirconium alloy–vanadium alloy) billet. A mixed nanostructure with a highly uniform distribution of zirconium and vanadium alloy regions forms under the chosen severe plastic deformation conditions in the middle layer of the material. The microhardness of this layer increases by a factor of about 2.5 as compared to the initial state.

The architecture of bimetallic nanoparticles has strong influence on durability and activity of PtM/C electrocatalysts in the oxygen electroreduction (ORR) and the methanol electrooxidation reactions (MOR). In the present study the Pt0.8(Cu)/C electrocatalyst was obtained by the methods of successive multistage reduction of platinum and copper from the solutions of their precursors while platinum concentration in the matrix solution was increasing step by step. The composition, structural characteristics and electrochemical behavior of this material were compared with the Pt1.0Cu/C catalyst based on the nanoparticles of a solid solution, which was obtained by the combined single-step chemical reduction of precursors, as well as with a commercial Pt/C sample with the same Pt-loading (20% by weight). The catalyst based on the Pt–Cu gradient nanoparticles demonstrated the highest corrosion-morphological stability in the stress-test, as well as the highest activity in ORR and MOR in the HClO4 solutions. Both of the studied bimetallic catalysts lose a significant amount of copper during the standardizing cycling and the stress-test. In the stabilized composition of the “gradient catalyst” the residual copper content, however, is considerably higher than that of the catalyst with the solid solution nanoparticles. The positive features of the electrochemical behavior of Pt0.8(Cu)/C catalyst arise apparently due to the faster formation of a durable protective layer of platinum on the surface of nanoparticles in the process of functioning, compared to the analogue based on the nanoparticles of the solid solution. High stability and activity of Pt0.8(Cu)/C compared to the Pt/C analogue are associated with the larger size of the nanoparticles and the promoting influence of residual copper on the catalytical activity of platinum.

The properties of nanorods made of high-energy-gap Zn x Mg1 – xO semiconductors are experimentally investigated using the new system of 3D manipulation of individual nanospecimens. The technology used to prepare Zn x Mg1 – xO nanorods via gas-phase deposition on a substrate, the process whereby individual nanorods are selected by means of nanocomposite tweezers with the shape-memory effect in the vacuum chamber of a two-beam scanning microscope, and the results obtained when their structure and morphology are experimentally studied using transmission electron spectroscopy are described. The prospects that nanophotonic, nanosensorial, and nanoelectronic devices can be fabricated from Zn x Mg1 – xO nanorods via the new nanomanipulation technique are discussed.

The research has been conducted into the impact that structural-phase state of grain boundaries in α-titanium alloy Ti-5Al-2V has on strength, plasticity and susceptibility to intercrystalline corrosion (ICC). It is found that during Equal Channel Angular Pressing (ECAP) performed at elevated temperatures there is a change in local concentration of alloying elements (aluminum, vanadium) along α-Ti grain boundaries. The current study proves that by controlling the structure of α-titanium alloy Ti-5Al-2V through ECAP it is possible to enhance its strength and resistance to hot salt intercrystalline corrosion. Plasticity of ultrafine-grained (UFG) alloy samples at room temperature is comparable with plasticity of a coarse-grained material, while plasticity of an UFG alloy at elevated temperatures is 2–3 times bigger than plasticity of a coarse-grained material.

The structure and mechanical properties of the crystals of solid solutions of zirconium dioxide, which are stabilized by yttrium and cerium oxides, have been studied. The electron paramagnetic resonance technique has been used to identify Ce3+ ions and to determine their relative concentration in the crystals. It is shown that the presence of Ce3+ ions in the crystals is the main factor responsible for their high fracture toughness. The annealings carried out during investigations, which lead to a decrease in the concentration of Ce3+ ions, show that a change in the valence state of cerium ions lowers the fracture toughness of the crystals.

We have prepared and characterized lithium titanate-based anode materials, Li4Ti5O12/C and Li4Ti5O12/C/Ag, using polyvinylidene fluoride as a carbon source. The formation of such materials has been shown to be accompanied by fluorination of the lithium titanate surface and the formation of a highly conductive carbon coating. The highest electrochemical capacity (175 mAh/g at a current density of 20 mA/g) is offered by the Li4Ti5O12-based anode materials prepared using 5% polyvinylidene fluoride. The addition of silver nanoparticles ensures a further increase in electrical conductivity and better cycling stability of the materials at high current densities.

PtCu/C electrocatalysts with bimetallic PtCu nanoparticles were synthesized by successive chemical reduction of Cu2+ and Pt(IV) in a carbon suspension prepared based on an aqueous ethylene glycol solution. The atomic structure of as-prepared PtCu nanoparticles and nanoparticles subjected to thermal treatment at 350°C was examined using PtL 3 and CuK EXAFS spectra, transmission electron microscopy (TEM), and X-ray powder diffraction (XRD). The results of joint analysis of TEM microphotographs, XRD profiles, and EXAFS spectra suggest that the synthesized electrocatalysts contain PtCu nanoparticles with a Cu core–Pt shell structure and copper oxides Cu2O and CuO. Thermal treatment of electrocatalysts at 350°C results in partial reduction of copper oxides and fusion of bimetallic nanoparticles with the formation of both homogeneous and ordered PtCu solid solutions.

The influence of severe plastic deformation on the structural-phase state of grain boundaries in a Ti–4Al–2V (commercial PT3V grade) pseudo-alpha-titanium alloy has been studied. It is established that increase in the strength, plasticity, and corrosion resistance of this alloy is related to the formation of an ultrafine- grained structure. In particular, it is shown that an increase in the resistance to hot-salt intergranular corrosion is due to diffusion-controlled redistribution of aluminum and vanadium atoms at the grain boundaries of titanium formed during thermal severe plastic deformation.

The operation-mode stability and the catalytic activity in electrode reactions are the most important properties of electrocatalysts that determine the possibility of using them in fuel cells. The negative linear correlations between stability and catalytic activity of a series of Pt/C and Pt–Cu/C materials in the oxygen electroreduction reaction are revealed and studied. A method of selecting electrocatalysts with the optimal combination of activity and stability is proposed. The Cu@Pt/C catalysts containing bimetallic nanoparticles with the core–shell architecture which demonstrate the anomalously high combination of activity and stability are synthesized.

The structure of the optical centers of Eu3+ ions in tetragonal (ZrO2)1–x–y(Y2O3)x(Eu2O3)y (х = 2.7–3.6; y = 0.1) and cubic (ZrO2)1–x–y(Y2O3)x(Eu2O3)y (х = 8–38; y = 0.1–0.5) crystals of solid solutions on the basis of zirconium dioxide is studied using the methods of optical and Raman-scattering spectroscopy. Characteristic optical centers of Eu3+ ions with different crystalline environments are revealed in the above compounds.

The effect of dysprosium added in the amounts such that it does not form an individual phase in equilibrium with solid magnesium on the decomposition of the supersaturated magnesium solid solution in Mg–Sm alloys is studied. The presence of dysprosium in Mg–Sm alloys is found to retard the decomposition of the supersaturated magnesium solid solution and to increase the hardening effect upon aging. When these alloys are aged, dysprosium is partly retained in the magnesium solid solution and partly enters into the compositions of the phases that form during the decomposition of the solid solution and are characteristic of Mg–Sm alloys.