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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 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.

(ZrO2)1-x(Gd2O3)x (x= 0.028–0.04) is heat-treated at 1600°C in air or in vacuum. Partially gadolinia-stabilized zirconia crystals are grown by the skull melting technique. The effect of annealing on the phase compositions, structures, and mechanical properties of the crystals is studied using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and indentation. A comparison with previously obtained data on the structure and properties of crystals after growth shows that annealing the crystals leads to the redistribution of gadolinia between the tetragonal phases: the t phase is depleted of gadolinia while the t’ phase becomes enriched. The gadolinia-enriched t’ phase undergoes multistage twinning. Thus, the sizes of the twins in the t’ phase are far smaller than those in the t phase. Annealing the crystals increases their fracture toughness, and this increase is larger for all crystals after air annealing. The increase in the fracture toughness of the crystals is caused by a decrease in the gadolinia concentration in the transformable t phase, which enhances the effect of the transformation hardening mechanism. The fracture toughness of the crystals is further increased by the ferroelastic hardening mechanism, the effect of which is enhanced with an increase in the quantity of the t’ phase in the crystals.

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 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.

Due to their tunable current–voltage characteristics, Zn-doped thin SiO2 films are promising for microelectronic devices, e.g., memristors. In this work we studied single-crystal Si (100) substrates with 200 nm SiO2 surface layers implanted with 64Zn+ using Zn K-edge x-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM) and electron diffraction. We used two specimens: as-implanted and annealed in oxygen at 700°C. Cross-section TEM analysis showed that 64Zn+ implantation leads to the formation of a subsurface layer consisting of Zn nanoparticles approximately 7 nm in size. The nanoparticles are distributed in depths from 10 nm to 90 nm, with a concentration peak at 45 nm. Electron microscopy showed that most of the Zn nanoparticles are amorphous. However, XAS data indicated that almost all the Zn atoms are coordinated with oxygen. Thus, only a small fraction of zinc atoms are involved in the formation of nanoclusters. Annealing at 700°C leads to the oxidation of particles with the formation of the Zn2SiO4 phase. The particle sizes in the surface layer of SiO2 after annealing vary from 3 nm to 20 nm.

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.

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.

It is shown based on the structural analysis by reciprocal space mapping and the experimental secondary ion mass spectrometry and transmission electron microscopy data that, along with lateral compressive stress, vertical compressive stress is induced in a multilayer epitaxial heterostructure with a metamorphic step-graded buffer. The reason for this stress is that interphase boundaries hinder complete stress removal at strain relaxation. The analysis carried out within the linear elasticity theory showed that the elastically strained state of the heterostructure layers is similar to the state arising during a two-stage deformation process (bulk and biaxial compression). It is shown that the free energy of the system in the metastable state is minimal in this case.

The single crystal CZ n-Si(1 0 0) substrates were implanted by 64Zn+ ions with a fluence of 5 × 1016/cm2 and energy of 50 keV to form Zn nanoparticle (NP). During implantation, the Si substrate the temperature was constant at about 350 °C. After that, the samples were irradiated at room temperature by 167 MeV 132Xe26+ ions with fluence at 7.5 × 1014/cm2 at 45° incident angle. The sample surface topology before and after Xe ion irradiation was studied using scanning electron microscopy. Structural changes in pre-implanted and Xe ion irradiated samples were examined by transmission electron microscopy in cross-sectional mode. It was found that swift Xe ion irradiation results in arise of radiation-induce defect of different kind. Defect structure of Si substrate consists of small-angle boundaries, dislocation and interstitial type planar defects. After swift Xe ion irradiation the form change of Zn NPs and increase of the NP average size were observed.

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 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

On the basis of data on X-ray structural analysis performed by the method of reciprocal-space mapping and investigations using secondary-ion mass spectrometry and transmission electron microscopy, it is shown that vertical compressive stresses also arise in a multilayer epitaxial heterostructure comprised of a step-graded metamorphic buffer along with lateral compressive stresses. The cause of the appearance of vertical stresses is the effect of interlayer hardening, which arises due to the deceleration of fragments of glide dislocations by interphase boundaries. Analysis performed within the framework of the linear theory of elasticity shows that the elastically stressed state of the buffer steps is similar to the state that can be achieved as a result of a two-stage deformation process: bulk and biaxial compression. Bulk compression leads to large energy expenditures in the formation of the structure of the buffer steps, which is reflected, in particular, in violation of the coherence between the dislocation-free and the underlying layers.

The development of aluminum alloys with superior mechanical properties and high strain rate superplasticity is an important prerequisite for advancing applications of superplastic blow-forming technology. This study focuses on the effect of Ce and Fe additions on the microstructural parameters and tensile properties of a superplastic Al-4.8%Mg-0.6%Mn-0.15%Cr (AA5083-type) alloy. The studied alloy exhibits a bimodal particle size distribution with coarse crystallization origin inclusions and fine secondary precipitates. Both the coarse and fine particles lead to grain refinement. The coarse Ce-, Fe-, and Mn-rich intermetallic particles of crystallization origin provide evidence of a particle-stimulated nucleation effect. The semi-coherent Mn-enriched compact-shaped dispersoids with an Ashby-Brown contrast, a quasicrystalline structure, and a mean size of 38 nm are precipitated after low-temperature homogenization and exhibit a strong Zener pinning effect. The proposed thermomechanical treatment results in the development of a grain size of 4 μm and an ultimate tensile strength of 340 MPa in the recrystallized sheet. The superplastic deformation behavior in a strain rate range of 1 × 10−2 to 1 × 10−1 s−1 and the associated strain-induced changes in the grain structure and mechanical properties of the developed alloy are presented and discussed.

Crystals of (ZrO2)1 –x – y(Sc2O3)x(Y2O3)y (x = 0.003–0.045, y = 0.005–0.03) solid solutions have been grown by directional solidification in a cold crucible. All of the crystals consist of a mixture of two tetragonal phases of zirconia, t and t', differing in the degree of tetragonality (c/ $$\sqrt 2 a$$ ): 1.014–1.015 and 1.004–1.005 for the t- and t'-phases, respectively. All of the crystals have high microhardness (13.5–15.0 GPa) and high fracture toughness (on the order of 6–7 MPa m1/2). Their fracture toughness decreases with an increase in the total content of the stabilizing oxides, which is well consistent with the associated changes in phase composition, namely, with the increase in the percentage of the (transformable) t-phase. All of the crystals are similar in electrical conductivity: on the order of 0.04 S/cm at a temperature of 1173 K.

We have studied the structure, phase composition and mechanical properties, e.g. microherdness and impact toughness of partially stabilized zirconia crystals in the 2–4 mol.% stabilizing yttria concentration range. We have shown that with increasing concentration of stabilizing yttria the microhardness increases while the impact fracture toughness varies nonmonotonically and reaches the maximum for the partially stabilized zirconia crystal with 3 mol.% Y2O3. The anisotropy of the microhardness and impact fracture toughness was studied for wafers perpendicular to the 〈100〉, 〈110〉 and 〈111〉 directions with different indenter diagonal orientations. We have shown that the microhardness of the partially stabilized zirconia crystals depends but slightly on crystallographic orientation whereas the impact fracture toughness differs between crystallographic faces of the crystals. The highest impact toughness was obtained for the {100} plane and the indenter diagonal aligned parallel to the 〈100〉 direction, while the lowest impact toughness was obtained for the {110} plane and the indenter diagonal aligned parallel to the 〈110〉 direction. Local Raman study of the monoclinic phase distribution in the vicinity of the indentation shows that the maximum quantity of the monoclinic phase forms along the 〈110〉 direction regardless of indenter diagonal orientation. We have shown that the strain anisotropy during the phase transition has variable effect on crack impedance. The effect of transformation hardening mechanism depends on crack plane orientation and transition induced stress.

This work is a study of the effect of co-doping (ZrO2)0.9(Sc2O3)0.1 solid solution with yttria and/or ceria on the phase composition, local structure and transport properties of the crystals. The solid solution crystals were grown using directional melt crystallization in cold crucible. We show that ceria co-doping of the crystals does not stabilize the high-temperature cubic phase in the entire crystal bulk, unlike yttria co-doping. Ceria co-doping of the (ZrO2)0.9(Sc2O3)0.1 crystals increases their conductivity, whereas the addition of 1 mol.% yttria tangibly reduces the conductivity. Equimolar co-doping of the (ZrO2)0.9(Sc2O3)0.1 crystals with ceria and yttria changes the conductivity but slightly. Optical spectroscopy of the local structure of the crystals identified different types of optical centers. We found that the fraction of the trivalent cations having a vacancy in the first coordination sphere in the ceria co-doped crystals is smaller compared with that in the yttria co-doped crystals. Keywords: Single crystals, Solid oxide fuel cell, Solid solutions, Ionic conducting materials, ZrO2-Sc2O3-CeO2-Y2O3

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 effect of high-pressure torsion (HPT) on the structural and phase transformations in a new eutectic aluminium alloy (94.9%Al; 3.5%Ca; 0.9%Mn; 0.5%Fe; 0.1%Zr; 0.1%Sc) was studied. HPT leads to the formation of a nanocrystalline structure with a predominant grain size of 11–34 nm. HPT causes the refining of eutectic [(Al) + Al4Ca] and the formation of nanoclusters and segregations. The phase composition of the alloy after HPT tends to the phase composition at elevated temperatures.

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.

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.

The specific features of the local structure of ZrO2–Sc2O3–Y2O3 and ZrO2–Sc2O3–Yb2O3 crystals are revealed by optical spectroscopy using the Eu3+ ion as a spectroscopic probe. It is shown that the local structure of crystals strongly affects their transport properties.

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.

The size and morphology of Ti3Ni4 precipitates, as well as their transformation behavior after isothermal aging, were studied in a Ti-50.7 аt.%Ni shape memory alloy with various B2 austenite grain sizes. A 0.3 mm thick band with an accumulated strain of e = 44% (e = 0.6) obtained by cold rolling was used. The samples were then solution-treated at 600–800°С for 0.3–1 h with subsequent quenching in water to obtain the structure with different grain size (GS) from 5 to 15 μm. The samples were then subjected to isothermal annealing at 430 °C for 1, 3 and 10 h. The SEM observations were carried out using a JSM-6460LV. The microstructure was studied using a JEOL 2100 TEM. Characteristic temperatures were measured using a “Mettler Toledo” DSC. The results of the microstructure study prove that the GS strongly affects Ti3Ni4 particle size and morphology, as well as the degree of microscale microstructure heterogeneity, transformation kinetics and transformation sequences. This influence is non-unique and depends on the duration of isothermal annealing. After 1 h of aging, the particle thickness and diameter maintain the nanometer range in the whole GS range of 5–15 μm. The increase of aging time to 3 and 10 h leads to localization of nanosized precipitates in the grain-boundary region, with the width of these regions decreasing with increasing GS. After aging for 1 h, the samples with the GS of 5 μm show the B2→R transformation. The increase in the GS to 15 μm and aging duration to 10 h is accompanied by multiplication of martensitic transformations to four stages. The study explains the influence of GS on the precipitated particle size and morphology, transformation kinetics and staging.

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.

Aluminum-based metal glasses are a promising new family of materials. However, the influence of thermal treatment on the structure and properties of amorphous alloys of the Al–Y–Ni–Co system is still not studied in detail. In this work, amorphous ribbons of the Al85Y8Ni5Co2 alloy are formed by quenching on a rotating copper disc. The influence of annealing in vacuum at temperatures from 100 to 500°C for 30 min on the structure and hardness of these ribbons is investigated. To investigate the variations occurring in their structure after thermal treatment, scanning electron microscopy, X-ray structural analysis, and differential scanning calorimetry are used. To investigate the influence of annealing on mechanical properties of ribbons, the Vickers microhardness is measured. Conclusions on the variation in hardness depending on the structure of ribbons of the Al85Y8Ni5Co2 alloy are made based on these results. It is established that their microhardness increases with an increase in temperature, reaching the maximal value of 575 ± 7 HV after annealing at 350°C, and then decreases with a further increase in the thermal-treatment temperature. It is shown that ribbons of the Al85Y8Ni5Co2 alloy remain totally amorphous after annealing at t ≤ 250°C for 30 min, and crystalline phases are absent in the structure. An abrupt increase in hardness after annealing at 350°C is associated with the formation of nanocrystals of the aluminum solid solution 10–30 nm in size in an amorphous matrix surrounded by the residual amorphous matrix, while its further decrease is caused by an increase in the size of these crystals and the appearance of Al3Yand Al19Ni5Y3 intermetallic compounds in the structure.

The comparative analysis of electrotransport characteristics and structure of ceramic and single crystal solid electrolytes with the (ZrO2)0.89(Sc2O3)0.10(Y2O3)0.01 composition is carried out before and after their life tests. It is shown that before the life tests, the specific conductivities of single-crystal and ceramic materials virtually coincide. During the 3000 h life tests, the specific ionic conductivity decreases for both single crystal and ceramic samples down to about 0.1 S cm–1 but the degradation of conductivity in single crystal proceeds more slowly as compared with the ceramic material. The reason for degradation of electrotransport characteristics in the single crystal is associated with the transition of its bulk structure from the t′′ phase to a phase with the higher degree of tetragonality, whereas in the ceramic material, in addition to the latter process, a rhombohedral phase appears presumably along grain boundaries.

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.

Crystallization of metallic glasses produced by rapid solidification and supercooled liquids on heating takes place at large undercooling which has some peculiarities compared to crystallization on casting. By using transmission electron microscopy we present a detailed in-situ study of an unusual isothermal crystallization reaction observed in the Al85Y8Ni5Co2 metallic glassy alloy below Tg. It started from the formation of a primary intermetallic compound (IMC) immediately followed by a pseudo-eutectic reaction consisting of IMC and nanoscale Al (solid solution) particles while α-Al particles are significantly smaller in size than the intermetallic phase. Moreover, a majority of these nanoscale α-Al particles do not have a common interface with the primary IMC particles but are separated by the residual glassy phase which remains present within these pseudo-eutectic colonies. On the other hand, as can be assumed from the Gaussian type of the heat flow plot at the isothermal conditions and reasonable linearity of the Avrami plot this reaction takes place like a single stage process. This residual glassy phase has a high stability versus crystallization and crystallizes only at a higher temperature. However, such a crystallization mechanism is observed only on slow heating or isothermal exposure at a temperature below Tg. On rapid heating or at isothermal annealing in the supercooled liquid, primary nanocrystallization of the aluminum solid solution is observed followed by the formation of intermetallic compounds at a higher temperature.

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.

Effects of equal-channel angular pressing (ECAP) with subsequent aging on the microstructure and phase transformation of Al–Mg2Si alloys with combined (Sc + Zr) and (Sc + Hf) additions were studied. The microstructure processed by ECAP and the precipitation of phases of Al–Mg2Si alloys were thoroughly examined by transmission electron microscopy (TEM). An analysis of the precipitation and determination of the temperatures of these precipitations in Al–Mg2Si alloys after ECAP was carried out by DSC. It has been revealed that transition metals added to Al–Mg2Si alloys do not change the character of decomposition of the solid solution but shift the precipitation temperatures of the β'', β' and β phases to lower temperatures compared to the quenched state. Recovery processes have been revealed in the temperature range 200–600 °C based on the changes in hardness and electrical resistivity of Al–Mg2Si alloys with additions of transition metals (Sc + Zr) and (Sc + Hf) and without them after ECAP.

The effect of Sc on plasticity at elevated temperatures(from 300 to 500 °C) and strain rates(from 10−3 to 10−1 s−1)of ultrafine-grained (UFG) Al–0.5%Mg–Sc alloyswas investigated. In the UFG alloys with 0.4% and 0.5%Sc at 500 °C and strain rate 1·10−1 s−1, high elongation to failure (~1060%) was achieved. The fractographic analysis of the fracturesin the Al–0.5%Mg alloy demonstrated the crack growth zone to occupy almost whole fracture area.The self-destruction in the crack growth zone has a viscous character.In the UFG alloys with Sc, numerous pits formed as a result of micropore junction were observed. Dependencies of dynamic grain growth (DGG) rate on the temperature and strain rate were determined. The DGG in the Al–0.5%Mg–Sc alloys was found. The kinetics of the DGG in the Al–0.5%Mg–0.2%Sc alloy was shown to be limited by mobility of junction disclinations. In the Al–0.5%Mg–0.5%Sc alloy, it is limited by mobility of oriented misfit dislocations. Al3Sc particles were shown to be possible origin of the micropore formation and of accelerated destruction of the Al–0.5%Mg–Sc alloys at high temperature deformation.

The article analyzes the effect of the addition of iron in the Zr–Cu–Al system metallic glassy alloys on the phase separation process during thermo-mechanical treatment. The addition of Fe causes formation of nanostructured regions of chemical inhomogeneity after cold rolling and annealing below the glass transition temperature. The resulted effect on the mechanical properties of the investigated alloys is established. Changes in the structure during thermo-mechanical treatment are studied in detail by transmission electron microscopy. The increase in the microhardness of the alloys during the formation of inhomogeneities in the amorphous matrix is explained by the difficulty of propagation of the shear bands formed during deformation.

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.

Spatial distribution of residual elastic strain in the layers of two step-graded metamophic buffers of various designs, grown by molecular beam epitaxy from ternary InxAl1–xAs solutions on GaAs(001) substrates, is obtained using reciprocal space mapping by three-axis X-ray diffractometry and the linear theory of elasticity. The difference in the design of the buffers enabled the formation of a dislocation-free layer with different thickness in each of the heterostructures, which was the main basis of this study. It is shown that, in spite of the different design of graded metamorphic buffers, the nature of strain fields in them is the same, and the residual elastic strains in the final elements of both buffers adjusted for the effect of work hardening subject to the same phenomenological law, which describes the strain relief process in single-layer heterostructures.