Search

Structure and phase formation in the course of fabricating composite ion–plasma vacuum-arc nanocrystalline TiN–Ni coatings are investigated in a broad range of nickel concentrations (from 0 to 26 at %). It is established that the introduction of Ni into the coating composition refines the nitride phase crystallites. The arithmetic mean size of TiN grains decreases from 100–120 to 15–18 nm upon varying the Ni concentration from 0 to 12 at % and normal particle-size distribution. The further increase in the Ni content is accompanied by the transition to the polymodal particle distribution with an increase in their arithmetic mean diameter to 27 nm for the third mode. Nickel in coatings at a concentration of 12–13 at % Ni is in the X-ray amorphous state. As the concentration increases above 13 at %, the TiNi intermetallic compound is formed in the composition of coatings. This phenomenon in turn causes the appearance of porosity in the structure of the deposited layer. The blocking role of nickel simultaneously weakens with the formation of the intermetallic compound, which manifests itself in the growth of separate TiN grains to 30–35 nm. The TiN–Ni coatings are characterized by the thermal stability of the structure and composition upon heating to 800°C.

This paper presents the results of investigations of the structure, phase composition, and spectral-luminescent properties of Er2O3-doped zirconia crystals with different Y2O3 concentrations: 99.7 mol % ZrO2-0.3 mol % Er2O3, 97.2 mol % ZrO2-1.0 mol % Y2O3-1.8 mol % Er2O3, 97.2 mol % ZrO2-2.0 mol % Y2O3-0.8 mol % Er2O3, 97.2 mol % ZrO2-2.5 mol % Y2O3-0.3 mol % Er2O3, 96.3 mol % ZrO2-3.4 mol % Y2O3-0.3 mol % Er2O3, and 86 mol % ZrO2-13.4 mol % Y2O3-0.6 mol % Er2O3. The transmission electron microscopy investigation has revealed the presence of twins in the 99.7 mol % ZrO2-0.3 mol % Er2O3 crystals with a monoclinic structure and in the 97.2 mol % ZrO2-2.5 mol % Y2O3-0.3 mol % Er2O3 and 96.3 mol % ZrO2-3.4 mol % Y2O3-0.3 mol % Er2O3 crystals with a tetragonal structure. No twins have been found in the 86 mol % ZrO2-13.4 mol % Y2O3-0.6 mol % Er2O3 crystals with a cubic structure. The phase composition of these crystals has been investigated using X-ray diffraction. It has been found that the 97.2 mol % ZrO2-1.0 mol % Y2O3-1.8 mol % Er2O3 crystals contain only the transformable tetragonal phase t, whereas the 97.2 mol % ZrO2-2.0 mol % Y2O3-0.8 mol % Er2O3, 97.2 mol % ZrO2-2.5 mol % Y2O3-0.3 mol % Er2O3, and 96.3 mol % ZrO2-3.4 mol % Y2O3-0.3 mol % Er2O3 crystals include two tetragonal phases with different degrees of tetragonality c/a: the transformable phase t and nontransformable phase t′. Specific features of the formation of Er3+ optical centers in zirconia crystals with different concentrations of stabilizing oxides have been revealed using the results of experiments on optical spectroscopy.

The results of studying the structure and composition of the surface layer of a Si plate after 64Zn+ ion implantation and thermal annealing in oxygen are presented. The ions are implanted into a substrate heated to a temperature of 400°C. Radiation defects and profiles of implanted Zn and oxygen diffused into the substrate are studied by means of 1.7-MeV He+-ion Rutherford backscattering spectroscopy using the channeling technique. The implanted layers are visualized using high-resolution transmission electron microscopy in combination with electron diffraction and energy dispersive microanalysis. Atomic-force microscopy is used to study the surface morphology.

The phase composition and spectral-luminescent characteristics of yttrium partially stabilized zir- conia (YSZ) crystals doped with Nd2O3 and CeO2 (ZrO2-Y2O3-Nd2O3-CeO2) are studied. X-ray diffrac- tion shows that YSZ ZrO 2 -2.5 mol %Y 2 O 3 -0.2 mol %CeO 2 -0.1 mol %Nd 2 O 3 , ZrO 2 -2.03 mol %Y 2 O 3 - 0.435 mol %CeO2-0.334 mol %Nd2O3, and ZrO2-2.03 mol %Y2O3-0.653 mol %CeO2-0.111 mol %Nd 2O2 YSZ crystals contain two different tetragonal phases (transformable t and nontransformable t � ). The spectral- luminescent properties of these crystals indicate that Nd 3+ ions occupy sites mainly in the transformable (t) phase.

Decomposition of the magnesium supersaturated solid solution during ageing and reversion after ageing in the commercial wrought magnesium alloy containing two rare earth metals (Mg–4.7%Y–4.6%Gd–0.3%Zr (wt.%)) were investigated using Brinell hardness, electrical resistivity measurements and transmission electron microscopy observation. The Mg–4.7%Y–4.6%Gd–0.3%Zr (wt.%) alloy is significantly hardened during ageing in the hot extruded condition owing to the decomposition of the magnesium supersaturated solid solution. The decomposition process in the alloy has been found to consist of precipitation sequence: β″(D019) → β′(cbco) → β(bcc). The maximum hardness is achieved after ageing at 200 °C, 64 h and caused by precipitation of the metastable β′(cbco) phase. It has been found that the Mg–4.7%Y–4.6%Gd–0.3%Zr (wt.%) alloy tends to the reversion after ageing when is subjected to annealing at temperatures higher than the ageing temperature. Dependence of the reversion after ageing on the annealing temperature and time has been established. During the reversion treatment the dissolution of the precipitates occurs, which leads to the softening of the alloy. The reversion effect increases with increasing annealing temperature.

Using kinetic microindentation, we have studied the strength and elastic characteristics of partially stabilized zirconia (PSZ) crystals. The results demonstrate that the mechanical properties of the crystals depend on yttria stabilizer concentration. Additional doping with ceria leads to an increase in the kinetic hardness, kinetic Young’s modulus, and plasticity of the crystals, thus improving their mechanical characteristics. The PSZ crystals have high plasticity for nonmetallic materials.

We have studied the effect of process parameters (temperature) in the reduction of titanium oxide with calcium hydride and calcium carbide on the concentrations and state of light elements (H, O, N, C, and S) in the reaction product and identified the oxygen-containing phases present in the titanium carbide (TiC) nanopowders obtained by reducing TiO2 with calcium hydride and calcium carbide. The oxygen present in the powders can be divided qualitatively and quantitatively into oxygen in adsorbed water, oxygen in organic compounds on the surface, and oxygen in the oxide layer on the surface of the carbide nanoparticle. We have performed fractional gas analysis for carbon in the titanium carbide nanopowders and assessed the effect of synthesis temperature on the average particle size and oxygen content of the nanopowders.

An evolution of Al–Cu–Mn alloy microstructure during its mechanical alloying with zirconium 20 wt% and after subsequent annealing was studied by X-ray diffraction, light microscopy and transmission electron microscopy. The effect of milling time on powder microhardness, Al lattice parameter, lattice microstrain and crystallite size was determined.

The effect of two-stage equal-channel angular pressing (ECAP) on the microstructure, the texture, and the mechanical properties of an MA2-1hp magnesium alloy is analyzed. ECAP leads to the formation of a submicrocrystalline structure with an average grain size of 640 nm, which includes Mg17Al12 phase particles with an average grain size of 240 nm and a volume fracture of 5.5%. A scattered tilted basal texture forms after ECAP, and its experimental pole figures are used for calculating orientation distribution functions and determining the volume fractions of the main orientations and the Schmid factors for different deformation systems. An increased activation of basal slip is found after both the first and the second stages of ECAP. As a result of two-stage ECAP, the strength properties of the alloy that correspond to the minimum acceptable values achieved by direct compression are obtained. Ductility is 44 and 18% after the first stage of ECAP plus subsequent annealing and after the second stage, respectively, which is almost four and two times higher than the initial value. The resulting strength mechanical properties of the alloy after the first and the second ECAP stages are analyzed using the Hall-Petch relation.

We have studied the influence of the yttrium oxide (Y2O3) dopant (1 and 2 mol %) on the phase composition, structure, and electrical properties of ZrO2–9 mol % Sc2O3 solid solution. Stabilization of ZrO2 jointly with 9 mol % Sc2O3 and 2 mol % Y2O3 is shown to allow the acquisition of high phase stability transparent homogeneous crystals with a cubic structure. Their mechanical grinding is established to cause no change in the phase composition of these crystals, whereas the powders retain the initial fluorine structure. The powders preserved the original structure of the fluorite crystals. All the probed crystals reveal high microhardness and low fracture toughness. Increasing the Y2O3 concentration in the crystals led to a reduction of the maximum loads on the indenter, which the sample withstood without cracking. As is shown, the specific conductivity exhibits nonmonotonic behavior depending on the Y2O3 concentration in the crystals. Increasing the Y2O3 content to 2 mol % in the solid electrolyte reduces the conductivity of the crystals in the entire temperature range that is attributed to a decrease in the carrier mobility due to the increasing ion radius of the stabilizing ion.

The structure and properties of castable alloy AN2ZhMts of the Al – Ni – Fe – Mn – Zr system based on an (Al) + Al9FeNi eutectic are studied after multistage annealing. The mode of annealing for maximum hardness is determined. The effect of the processes occurring during the annealing on the hardness and electric resistivity is estimated. The properties of alloy AN2ZhMts in annealed condition are compared to those of widely used heat treated copper-free silumins of types AK7ch and AK9ch.

We have studied the temperature dependence of the mechanical strength at uniaxial compression for solid solutions based on bismuth and antimony chalcogenides, which were prepared by three methods: (i) vertical zone melting (VZM), (ii) hot extrusion, and (iii) spark plasma sintering (SPS). In the samples of solid solutions obtained by VZM and extrusion, a brittle–ductile transition was observed in a wised temperature interval of 200–350°C. In nanostructured SPS samples, transition from brittle to plastic fracture was observed within 170–200°C. The room-temperature strength of nanostructured samples was eight to nine times as large as that of VZM samples, and the stress–strain curves of these materials were significantly different. At a temperature of about 300°C, the strength of nanostructured solid solutions decreases to nearly zero.

The melt spinning technique is a process for obtaining materials based on ultrafast cooling and solidification of a melt in contact with a liquid-cooled rotating wheel. In this work, p-Bi0.5Sb1.5Te3 powders were obtained and compacted by spark plasma sintering at various temperature conditions, and the changes in their structural and dimensional characteristics were investigated. It is shown that the sintering temperature conditions significantly affect the structure of the material, causing active recrystallization processes even at short sintering times (5 min to 10 min). Material obtained in this work has slight preferential orientation of (0 0 1) planes perpendicular to the pressure axis, which disappears with increasing sintering time. Power factor values for all samples were greater for current direction perpendicular to the pressure axis, which corresponds to compacted nonspun material. It is shown that annealing in vacuum negatively affects the material, reducing the power factor for all current directions.

The structure and properties of TiN-Cu coatings with a broad range of copper concentrations (C Cu = 0.6–20 at %), which were fabricated by the ion-plasma vacuum-arc deposition on a TT10K8B hard-alloy tool, including its cutting resistant tests, were investigated. The introduction of copper into the coating composition diminishes crystallites of the nitride phase from 100 to 20 nm. The hardness of coatings increases from 20 to 40 GPa, with an increase in C Cu to 7–8%. The further increase in the copper content, which is accompanied by diminishing crystallites of the nitride phase, is characterized by a decrease in hardness to 14–15 GPa, which is associated with the influence of soft plastic metal. Resistant cutting tests of steel 35KhGSA of removable multifaceted plates (RMP) with the TiN-Cu coatings indicate that the optimally selected composition (TiN-7-8 at % Cu) increases RMP resistance more than by a factor of 6 and 2.5 as compared with tools without the coating and with the TiN coating deposited according to the basic technology, respectively.

The crystal structure of ultrathin InSb nanowires fabricated by an injection of the molten semiconductor into the channels of chrysotile asbestos is studied. It is shown that the nanowire structure is polycrystalline. The average crystallite size is comparable to the nanowire diameter and corresponds to 4.4 nm.

A nonmonotonic variation of crystallite size in thermoelectric materials depending on spark plasma sintering (SPS) temperature was found in this work by using X-ray diffraction. The crystallite size grows with increasing temperature from 250 °C to 400 °C and decreases at temperatures from 400 °C to 500 °C. The transmission electron microscopy results suggest that the decrease in the average crystallite size is associated with an intense formation of fine grains at an SPS temperature of 450 °C as a result of repeated recrystallisation. New grains in the structure precipitate faster than the old grains grow. The total density of the defects including the twins decreases. The initiation of new repeated recrystallisation centres occurs on the grain boundaries, on the dislocation defects and in the grain bulk, most likely on the subgrains. The pattern that has been discovered solves the problem of nano state preservation at elevated SPS temperatures.

The data presented in this article are related to the research article entitled “Phase stability and transport characteristics of (ZrO2)1-x(Sc2O3)x(СeO2)y and (ZrO2)1-x-y-z(Sc2O3)x(СeO2)y(Y2O3)z solid solution crystals” https://www.sciencedirect.com/science/article/pii/S2352340917302329 [1]. It contains data on densities and microhardness of the as-grown crystals. The data on the specific conductivity of the as-grown and annealing at 1000 °С for 400 h ScCeSZ and ScCeYSZ crystals in the temperature range 623–1173 K is also included in this article. The article describes also the growth of the (ZrO2)1-x(Sc2O3)x(СeO2)y and (ZrO2)1-x-y-z(Sc2O3)x(СeO2)y(Y2O3)z solid solution crystals using directional melt crystallization in a cold crucible. Keywords: Single crystals, Solid oxide fuel cell, Solid solutions, Ionic conducting materials, ZrO2–Sc2O3-CeO2

The electronic and optical properties of Si doped by Zn diffusion have been studied for a long time. Recently the defect structure and properties of n-Si (111) compensated by Zn during high-temperature diffusion annealing with subsequent quenching were investigated. The large-scale rod-like defects with μ-sizes have been observed. These defects were connected with Zn precipitates or/and dislocations. In the present paper we study the modification of defect structure and properties of Zn diffusion doped Si after swift heavy ion (SHI) irradiation. The SHI irradiation is known to lead to the formation of latent tracks (nanometer-sized disordered regions around ion trajectory) in many semiconductor and oxide crystals. It was established that the craters with a size of about 100nm surrounded by hillocks are fixed on the Si surface. The traces of dislocation group along Xe ion beam direction were revealed on Si surface. The small-angle boundaries and interstitial-type planar defects have appeared. After Xe ion irradiation with a fluence of 5×1012 cm−2 the number of radiating centres in dislocation core increasing so, that increasing the dislocation-related luminescence (DRL) from the lines D1 and D2. When the Xe ion irradiation fluence is increased to a value of 1×1014 cm−2 the DRL in the Si sample is almost extinguished.

The structure of partially stabilized zirconia crystals is investigated by X-ray diffractometry and transmission electron microscopy. It is shown that the combination of structural methods allowed one to reveal features of the structure and phase composition of these materials. Partially stabilized zirconia has a complex twin-domain structure. X-ray diffractometry with the use of Kβ radiation shows the presence of two phases of the tetragonal modification of zirconia with different tetragonality in all investigated samples independently of the content of the stabilizing impurity. The combination of the locality of transmission microscopy with the integral nature of X-ray diffractometry allowed one to reveal the dependence of the dispersion of twin domains on the concentration of the stabilizing impurity. The use of transmission microscopy with high resolution demonstrates the hierarchy of twinning and the presence of twin domains ∼10 nm in width.

The microstructures of Pt/C and PtM/C (M = Ni, Cu, or Ag) electrocatalysts were studied using X-ray diffraction and transmission electron microscopy (TEM). The electrochemically active surface areas of the prepared materials were estimated by cyclic voltammetry in 1 M H2SO4. The materials, with metal contents ranging from 30 to 35 wt.%, were synthesized by chemically reducing the metal precursors in water–ethylene glycol solutions. The actual composition of the bimetallic nanoparticles corresponds to a theoretical (1:1) composition for the PtAg/C catalysts, whereas in the PtNi/C and PtCu/C materials, a portion of the alloying component exists in an oxide form. Decreasing the average metallic crystallite sizes from 3.5 to 1.6 nm does not increase the electrochemically active surface area. This apparent contradiction is because a majority of the PtNi and PtCu nanoparticles consist of 2–4 disordered crystallites. In addition, a portion of the PtNi or PtCu nanoparticle surface is covered by nickel or copper oxides, respectively. PtAg nanoparticles, which have a smaller size relative to other bimetallic particles according to the TEM data, are characterized by an intense platinum surface segregation. The agglomeration processes are lowest for the PtAg nanoparticles.

The dependence of the thermoelectric properties of the nanostructured bulk (Bi,Sb)2Te3 material on the composition and the spark plasma-sintering (SPS) temperature TSPS has been studied. It has been revealed that the Bi0.4Sb1.6Te3 solid solution sintered at a temperature of 450–500°C has a thermoelectric figure of merit ZT = 1.25–1.28. The dependence of thermoelectric properties on the sintering temperature TSPS above 400°C is correlated to the transformation of the fine structure of the material due to the rearrangement of point vacancy-donor defects in the process of repeated recrystallization. It has been established that point structural defects make a considerable contribution to the formation of the thermoelectric properties of nanostructured material.

This work is a complex experimental and theoretical study of the extrusion process by equal-channel angular pressing in the production of chalcogenides based on bismuth telluride, which are of interest for the creation of new functional thermoelectrics.

Structural transformations in melt-spun Ti2NiCu ribbon are studied by means of X-ray diffraction. The phase composition of a ribbon during crystallization and martensitic transformations is determined qualitatively and quantitatively. Temperatures of crystallization and the onset and finish of forward and reverse martensitic transformations are established.

Data from investigating the formation of nanoparticles (NPs) on a surface of silicon wafers after zinc ion implantation and thermal annealing are presented. The investigation is conducted by means of trans-mission electron microscopy, electron diffraction analysis, energy dispersive microanalysis, scanning tunneling microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. It is found that on their surfaces, the implanted samples have only films of amorphous silicon containing implanted zinc, oxygen, and carbon contamination. Thermal treatment in the range of 400–800°C leads to the formation NP with 20–50 nm wide and 10 nm tall on a wafer’s surface, plus a silicon oxide layer about 20 nm thick. NPs are composed of zinc compounds of the ZnO, ZnSiO3, or Zn2SiO4 types. These NPs disappear after annealing at 1000°C.

The phase composition and morphology of the twin structure of the Y2O3-stabilized zirconia crystals (from 2.8 to 4.0 mol %) after the thermal treatment at 1600°C have been investigated by X-ray diffractometry and transmission electron microscopy. It is shown that as the concentration of the stabilizing Y2O3 impurity increases, the character of the twin structure changes, and the amount of the untransformed phase t′ increases. The dependence of the hardness and crack resistance of the crystals of partially stabilized zirconia on the Y2O3 concentration and the indenter orientation is investigated using the microindentation method. The sample with the lowest concentration of the stabilizing Y2O3 impurity turned out the most crack resistant. This can be explained by a high content of tetragonal phase t in it, which provides the transformation strengthening mechanism of the material, and by a more multilevel character of twinning.

Using X-ray diffraction and scanning electron microscopy, we have studied general aspects of defect structure formation in thermoelectric materials in different stages of plastic flow in the equal-channel angular pressing process with three channels. The results demonstrate that materials prepared using this deformation configuration have a fine-grained, homogeneous microstructure with a favorable texture, such that the cleavage planes of the grains are oriented along the extrusion axis. Studies of the structure and properties of the thermoelectric materials allowed us to optimize the equal-channel angular pressing temperature, which should be below the recrystallization onset temperature.

Kinetics and structural transformations upon the decomposition of a magnesium-based supersaturated solid solution in Mg-Sm-Tb alloys have been studied at various relations between the concentrations of terbium and samarium. It has been established that with increasing terbium content in the alloys the strengthening upon the decomposition of the supersaturated magnesium-based solid solution increases. The decomposition of the supersaturated magnesium-based solid solution in the Mg-Sm-Tb alloys with a percentage ratio (wt %) Tb: Sm of about 2.5 exhibits signs characteristic of the decomposition of the supersaturated solid solution in binary Mg-Tb alloys. With allowance for the equilibrium Mg-Sm-Tb phase diagram, this gives grounds to suppose that samarium is mainly dissolved in the products of the decomposition of the magnesium solid solution that are characteristic of Mg-Tb alloys.

To optimize the chemical composition of the crystals of nanostructured partially stabilized zirconium dioxide for fabricating cutting parts of an electrosurgical tool, the structural and strength properties of these crystals were investigated in dependence on the stabilizing impurity (Y2O3) content and the effect of additional dopants on the critical properties of the material was studied. It was established that in all the investigated crystals without additional doping, regardless of the stabilizing impurity content, there are two phases of zirconium dioxide tetragonal modification with different tetragonality factors, c/a = 1.006–1.007 and 1.014–1.015, the first being nontransformable and the second being transformable to a monoclinic phase. All the synthesized crystals are characterized by a pronounced twin domain structure, which forms upon cooling the single crystal during the transition of the cubic structure to the tetragonal one. It was established that the Y2O3 concentration in the range from 2.5 to 3.0 mol % is optimal for ensuring high values of the strength characteristics and fracture toughness of the material. Doping of the crystals with the rare-earth elements notice-ably affects their strength characteristics. One of the most promising materials for fabricating cutting blades of the electrosurgical tool is the crystals of partially stabilized zirconium dioxide doped with Ce2O3+Nd2O3, which are characterized by high fracture toughness and enhanced bending strength.

Ball milling with subsequent spark plasma sintering (SPS) was used to fabricate bulk nanothermoelectrics based on Bi x Sb2−x Te3. The SPS technique enables reduced size of grains in comparison with the hot-pressing method. The electrical and thermal conductivities, Seebeck coefficient, and thermoelectric figure of merit as functions of temperature and alloy composition were measured for different sintering temperatures. The greatest value of the figure of merit ZT = 1.25 was reached at the temperature of 90°C to 100°C in Bi0.4Sb1.6Te3 for sintering temperature of 450°C to 500°C. The volume and quantitative distributions of size of coherent dispersion areas (CDA) were calculated for different sintering temperatures. The phonon thermal conductivity of nanostructured Bi x Sb2−x Te3 was investigated theoretically taking into account phonon scattering on grain boundaries and nanoprecipitates.

Thin epitaxial gadolinium manganite (GdMnO3) films were manufactured on single-crystal substrates of neodymium gallate (001) (NdGaO3) and strontium titanate (001) (SrTiO3) by the high-frequency magnetron sputtering method. The RBS analysis demonstrated that the thickness of the obtained films was ∼100 nm and the chemical composition corresponded to the stated stoichiometry. It was established by the X-ray diffraction analysis of the structure and phase composition of the obtained films that all films were single-phase but, depending on the temperature of the substrate during sputtering they have one or several types of orientations relative to the substrate. The X-ray diffraction analysis and high-resolution electron microscopy data on gadolinium manganite films on neodymium gallate substrates were verified. Features pointing to phase transitions in GdMnO3 that were earlier discovered on bulk single-crystal samples were found in the temperature dependence of the magnetic susceptibility.

A comparative analysis of structures of compact samples of Bi0.5Sb1.5Te3 thermoelectric materials, obtained by the spark plasma sintering (SPS) and traditional hot-pressing methods, was performed by the X-ray diffractometry and scanning electron microscopy methods. It is shown that the spark plasma sintering method failed to obtain structure sizes smaller than the hot-pressing method. However, the sintering quality, characterized by the absence of pores and cracks, and sizes of fragments of the fractured surface, is higher at comparable temperatures in the samples obtained by the SPS-method.

Investigations of nanoscale silicon powders obtained by plasma chemical synthesis in various process parameters were carried out by transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared (IR) spectroscopy. It was demonstrated that the powders consist of spherical particles with an average diameter from 20 to 30 nm. Each particle includes a single-crystal silicon core and amorphous shell whose chemical composition is defined by bonds of silicon with oxygen and hydrogen. The measurements of photoluminescence (FL) show the presence of dim near-infrared FL in the specimen powders, and more intensive emission around 420 nm in the suspension of the powder in ethanol. The character of this emission has not been determined yet.

The structure of bulk specimens of powders of Bi2Te2.7Se0.3 solid solution after severe torsional plastic deformation at a pressure of 250 MPa and a temperature of 380°C is studied. The microstructure of the specimens is determined by the methods of x-ray diffractometry and scanning and transmission electron microscopy. The effect of the size of the particles of the initial powder on the faulted structure of the material and on its heat resistance is studied.

The shape memory effect (SME) in alloys with thermoelastic martensitic transformation provides a unique possibility to create the tiny mechanical devices for NEMS / MEMS technology. SME observed in layered composite microstructors produced by FIB CVD technology, consisting of Ti2NiCu alloy layer with SME and platinum elastic layer at reducing the thickness of the active layer for at least 80 nm. In this paper the physical and technological restrictions were experimentally examined on the minimum thickness of the active layer of the composites for SME manifestation.

The structure of partially stabilized zirconia crystals has been studied by transmission electron microscopy before and after annealing. Structural characterization of Y2O3-doped (2.8 to 4 mol %) zirconia before annealing showed that all of the samples consisted of twin domains whose size was dependent on the stabilizer content. Annealing at 2100°C increased the domain size in the composition range 2.8–3.7 mol % Y2O3 and reduced it at 4 mol % Y2O3. These structural changes allowed us to determine the position of the representative point relative to the phase boundary in the equilibrium phase diagram of the system.

The properties anisotropy of thermoelectric solid solutions of bismuth chalcogenides are investigated. The ingot texture obtained with the help of zone melting and by the modified Bridgeman method (the procedure for thermoelectric plates growing in a flat cavity) is studied. The texture has been investigated and it is revealed that if the crystallization is performed by the modified Bridgeman method, not only the crystallization rate but also the crystallization cavity embodiment are important for forming the solid structure of thermoelectric material.

An analysis of anisotropy of the properties of a Bi2Se0.3Te2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.

The controllable annealing of amorphous Ti2NiCu ribbons by a pulsed electric current was developed, and samples with different fractions of crystalline phase were obtained. The samples’ structure was studied using high-resolution electron microscopy. Annealing conditions allowing us to obtain an amorphous nanocrystalline structure with grain sizes of less than 10 nm were determined. Conditions for obtaining samples with the two-wave shape memory effect were found. A prototype micromanipulator was designed and successfully tested.

Samples containing anatase and η-TiO2 nanoparticles have been prepared from titanyl sulfate solutions and characterized by X-ray diffraction, transmission electron microscopy, and electron diffraction. Unit-cell parameters of η-TiO2 have been proposed that do not rule out a relationship between the anatase and η-TiO2 structures. The samples containing anatase and η-TiO2 differ in crystallite size and specific surface area and consist of agglomerates of particles of various sizes covered with an amorphous layer. We have studied the effect of synthesis conditions on the ability to prepare a particular titania polymorph with various functional characteristics.

The development of micromechanical devices (MEMS and NEMS) on the basis of nanostructured shape memory alloys is reported. A Ti50Ni25Cu25 (at. %) alloy fabricated by the melt spinning technique in the form of a ribbon with a thickness around 40 μm and a width about 1.5 mm was chosen as a starting material. Technological parameters were optimized to produce the alloy in an amorphous state. The thickness of the ribbon was reduced to 5–14 μm by means of electrochemical polishing. A nanostructural state of the thin ribbons was obtained via the dynamic crystallization of the amorphous alloy by application of a single electric pulse with duration in the range of 300–900 μs. A microtweezers prototype with a composite cantilever of 0.8 μm thick and 8 μm long was developed and produced on the basis of the obtained nanostructured thin ribbons by means of the focused ion beam technique. Controlled deformation of the micromanipulator was achieved by heating using semiconductor laser radiation in a vacuum chamber of s...

The real structure of samples of optical fluoride ceramics is studied by atomic force, scanning electron, and transmission electron microscopy. It is shown that the optical ceramic samples based on CaF2 have a lamellar structure, and the distance between lamellae is 25–50 nm. Most likely, lamellae have a twin nature. For BaF2 ceramic, lamellae are not typical, and they are concentrated near grain boundaries.

In this work, we used x-ray structural diagnostic data to reveal the formation of structural regularities in profiled polycrystalline ingots based on Bi and Sb chalcogenide solid solutions. In Bi2Te3 lattice crystals, the solid phase grows such that the cleavage surfaces are perpendicular to the crystallization front. The crystallization singularity determines the nature of the growth texture. Because texture is an important factor determining the anisotropy of properties, which in turn determines the suitability of an ingot for production of modules and the possibility of figure of merit improvement, its diagnostics is an important issue for technology testing. Examples of texture analysis using the method of straight pole figure (SPF) construction for profiled crystals are provided. The structure of the surface layers in the profiled ingots was studied after electroerosion cutting. In addition, the method of estimation of the disturbed layer depth based on the nature of texture changes was used.

Zirconia single crystals doped with 2.8, 3.2, 3.7, and 4.0 mol % of Y2O3 have been studied. The phase composition and structure have been studied by X-ray diffraction analysis and transmission electron microscopy. It has been established that all investigated samples has two ZrO2 tetragonal phases with tetragonality c/a = 1.006–1.007 and c/a = 1.014–1.015 independent of the stabilizing impurity content. The former phase is not transformed, whereas the latter is transformed into a monoclinic one. In all cases the samples have a developed twin structure. Twinning hierarchy is observed: there are first-, second-, third-order, etc., twins, each of them containing the next-order twins inside them. Elastic stress relaxation occurs by twinning rather than by generation of dislocations. The stabilizing impurity content affects the structure nonmonotonically; the minimum dimensions of the twin lamellas refer to the Y2O3 concentration of 3.2 mol %.

The dependences of the electrical conductivity and thermopower on the size of grains in a nanocrystalline material based on Bi2Te3-Sb2Te3 solid solutions of the p type have been investigated theoretically and experimentally. The relaxation time in the case of hole scattering by nanograin boundaries in an isotropic polycrystal has been calculated taking into account the energy dependence of the probability of tunneling of charge carriers and the dependence of the scattering intensity on the nanograin size L n . A decrease in the probability of boundary scattering with an increase in the energy of charge carriers leads to an increase in the thermopower. The dependences of the thermopower and electrical conductivity on the nanograin size, which have been obtained taking into account the boundary scattering and scattering by acoustic phonons, are in good agreement with experimental data. For the material under consideration, the thermopower coefficient increases by 10–20% compared to the initial solid solution at L n = 20–30 nm. This can lead to an increase in the thermoelectric figure of merit by 20–40%, provided that the decrease in the electrical conductivity and the decrease in the lattice thermal conductivity compensate each other. Despite the absence of a complete compensation, it has been possible to increase the thermoelectric figure of merit for the samples under investigation to ZT = 1.10–1.12.

Samples of Ti 2 NiCu rapidly-quenched alloy with different fractions of crystalline phase were prepared from as-spun amorphous ribbons by two different techniques: applying electric pulse and annealing in differential scanning calorimeter (DSC). The structure and thermomechanical properties of these samples were studied. Spherulites were found in a structure of the samples prepared by DSC. And the mixture of amorphous and nanocrystalline structures with mean grain size less than 10 nm was observed by TEM for samples annealed by electric current. The two-way shape memory was induced in the fractionally crystallized samples by single deformation at cooling below the martensite transformation temperature.

Bulk nanostructured polycrystals are prospective thermoelectrics. Fabrication and examination of nanostructured polycrystalline p-Bi-Sb-Te are discussed. The influence of fabrication conditions and the composition of the material on sizes of nanograins was investigated experimentally. Basic physical properties of fabricated nanothermoelectrics including nanocomposites were also studied. Theoretical estimation of the influence of phonon scattering on nanograin boundaries in bulk nanostructured thermoelectrics is presented.

The technology of obtaining titanium carbide powders by reduction-carbidization of titanium dioxide with calcium hydride and carbide at temperatures up to 1200°C is developed. The dispersity of the TiC particles is determined by thermal desorption and scanning electron microscopy: the average size of crystals is no larger than 1 μm. It is revealed by the methods of coulometry and energy dispersive spectrometry that calcium-hydride titanium carbide is characterized by a high content of bound carbon and a low content (0.01–0.03 wt %) of free carbon. It is established by X-ray structural analysis and transmission electron microscopy that TiC particles are uniform (their composition is close to stoichiometric TiC1.0) and are single crystals. The investigation of the structure and properties of hard alloys of the compositions 60% TiC + 29.6% Ni + 10.4% Mo and 72% TiC + 18.3% Ni and 9.7% Mo, which were obtained on the basis of calcium-hydride titanium carbide powders, showed that they completely satisfy the requirements to tungsten-free hard alloys.

The article provides an example of applying the technology of spark plasma sintering (SPS) to ensure high-rate diffusion welding of high-strength ultra-fine-grained UFG titanium alloys. Weld seams produced from Ti-5Al-2V UFG titanium alloy and obtained through SPS are characterized by high density, hardness and corrosion resistance.

Temperature-dependent strength of Bi-Sb-Te under uniaxial compression is investigated. Bi-Sb-Te samples were produced by three methods: vertical zone-melting, hot extrusion, and spark plasma sintering (SPS). For zone-melted and extruded samples, the brittle-ductile transition occurs over a temperature range of 200-350 °C. In nanostructured samples produced via SPS, the transition is observed in a narrower temperature range of 170-200 °C. At room temperature, the strength of the nanostructured samples is higher than that of zone-melted and extruded samples, but above 300 °C, all samples decrease to roughly the same strength.

A nanopowder from p-Bi-Sb-Te with particles ~ 10 nm were fabricated by the ball milling using different technological modes. Cold and hot pressing at different conditions and also SPS process were used for consolidation of the powder into a bulk nanostructure and nanocomposites. The main factors allowing slowing-down of the growth of nanograins as a result of recrystallization are the reduction of the temperature and of the duration of the pressing, the increase of the pressure, as well as addition of small value additives (like MoS2, thermally expanded graphite or fullerenes). It was reached the thermoelectric figure of merit ZT=1.22 (at 360 K) in the bulk nanostructure Bi0,4Sb1,6Te3 fabricated by SPS method. Some mechanisms of the improvement of the thermoelectric efficiency in bulk nanocrystalline semiconductors based on BixSb2-xTe3 are studied theoretically. The reduction of nanograin size can lead to improvement of the thermoelectric figure of merit. The theoretical dependence of the electric and heat conductivities and the thermoelectric power as the function of nanograins size in BixSb2-xTe3 bulk nanostructure are quite accurately correlates with the experimental data.