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In this work, a Fe–Mn–Pd alloy was produced by methods of equal channel angular pressing (ECAP) in order to obtain an alloy with a high rate of degradation for the development of biodegradable devices. Special efforts were made to the obtaining of an ultrafine-grained structure of alloys in a fully austenitic state at temperatures of 300 °C and 450 °C. Further investigation of its effect on the corrosion rate and mechanical properties was carried out. The formation of an austenitic structure with structural element sizes of 100–250 nm after deformation was confirmed by X-ray diffraction analysis. ECAP proved to be the reason for a significant increase in strength with maximum σUTS = 1669 MPa and σYS = 1577 MPa while maintaining satisfactory plasticity. The alloy degradation rate was investigated using the potentiodynamic polarization analysis. The corrosion rate of the alloy after ECAP (~1 mm/y) is higher than that of the coarse-grained state and significantly higher than that of annealed iron (~0.2 mm/y). ECAP in both modes did not impair the biocompatibility of the Fe–Mn–Pd alloy and the colonization of the sample surface by cells.

Magnesium alloys are attractive candidates for use as temporary fixation devices in osteosynthesis because they have a density and Young’s modulus similar to those of cortical bone. One of the main requirements for biodegradable implants is its substitution by tissues during the healing process. In this article, the Mg–Zn–Ga–(Y) alloys were investigated that potentially can increase the bone growth rate by release of Ga ions during the degradation process. Previously, the effectiveness of Ga ions on bone tissue regeneration has been proved by clinical tests. This work is the first systematic study on the microstructure and mechanical properties of Mg–Zn–Y alloys containing Ga as an additional major alloying element prepared by the hot-extrusion process. The microstructure and phase composition of the Mg–Zn–Ga–(Y) alloys in as-cast, heat-treated, and extruded conditions were analyzed. In addition, it was shown that the use of hot extrusion produces Mg–Zn–Ga–(Y) alloys with favorable mechanical properties. The tensile yield strength, ultimate tensile strength, and elongation at fracture of the MgZn4Ga4 alloy extruded at 150 °C were 256 MPa, 343 MPa, and 14.2%, respectively. Overall, MgZn4Ga4 alloy is a perspective for applications in implants for osteosynthesis with improved bone regeneration ability.

A multi-metal composite was consolidated from the Ti50Ni25Cu25 and Fe50Ni33B17 alloys by room-temperature high-pressure torsion (HPT). The structural research methods used in this study were X-ray diffractometry, high-resolution transmission electron microscopy, scanning electron microscopy with an electron microprobe analyzer in the mode of backscattered electrons, and the measurement of indentation hardness and modulus of the composite constituents. The structural aspects of the bonding process have been examined. The method of joining materials using their coupled severe plastic deformation has been established to play a leading role in the consolidation of the dissimilar layers upon HPT.

The effect of high-pressure torsion (HPT) on the microstructure, phase composition, mechanical characteristics, degradation rate, and bioactive properties of the Zn–1%Mg alloy is studied. An ultrafine-grained (UFG) structure with an average grain size of α-Zn equal to 890 ± 26 nm and grains and subgrains of the Mg2Zn11 and MgZn2 phases with a size of 50–100 nm are formed after HPT. This UFG structure leads to an increase in the ultimate tensile strength of the alloy by ~3 times with an increase in elongation to 6.3 ± 3.3% due to the formation of a basal texture. The study of corrosion resistance did not show a significant effect of HPT on the degradation rate of the alloy. In addition, no significant changes in the bioactivity of the alloy after HPT: hemolysis, cellular colonization and Escherichia coli growth inhibition.

TiNi-TiCu quasibinary system alloys with a high Cu content produced by rapid quenching from liquid state in the form of thin amorphous ribbons exhibit pronounced shape memory effect after crystallization and are promising materials for miniaturized and fast operating devices. There is currently no complete clarity of the mechanisms of structure formation during crystallization from the amorphous state that determine the structure-sensitive properties of these alloys. This work deals with the effect of the initial amorphous state structure and crystallization method of the alloys on their structure and phase transformations. To this end the alloy containing 30 at.% Cu was subjected to thermal and mechanical impact in the amorphous state and crystallized using isothermal or electropulse treatment. We show that after all types of treatment in the amorphous state the structure of the alloy remains almost completely amorphous but the characteristic temperatures and enthalpy of crystallization become slightly lower. Isothermal crystallization of alloy specimens produces a submicrocrystalline structure with an average grain size in the 0.4–1.0 μm range whereas electropulse crystallization generates a bimorphic structure consisting of large 4–6 μm grains and 2–3 μm high columnar crystals in the vicinity of the surface. The grains have nanosized plate-like and subgrain structures. The largest grains are observed in thermally activated samples, meanwhile, mechanical impact in the amorphous state leads to the formation of equiaxed finer grains with a less defective subgrain structure and to the shift of the temperature range of the martensitic transformation toward lower temperatures.

Based on the conceptual Al–Cu–(Fe + Co) phase diagram we found an optimal initial composition and developed a method to grow Al–Cu–Fe–Co single-grain quasicrystals. Our original two-stage cooling process includes (i) fast cooling of the melt down to the quasicrystalline single phase region with rate of ∼165 K/h to prevent growing of nonquasicrystalline phases in the melt, and (ii) slow cooling down with rate of ∼2–3 K/h to grow large (mm-size) single-grain quasicrystals. As a result a new stable quaternary Al-based icosahedral quasicrystal has been obtained. The chemical composition of the grown quasicrystal determined by both the energy dispersive X-ray analysis and inductively coupled plasma mass spectrometry was Al64.36Cu22.20Co3.05Fe10.39. Powder XRD and selected area electron diffraction were carried out for the phase identification and confirmed the icosahedral structure. The temperature dependencies of the electrical resistance measured on the oriented samples in the temperature range of 1.4 K–300 K is typical for icosahedral quasicrystals.

The amorphous rapidly quenched quasi-binary TiNi–TiCu alloys containing 30–38 at.% Cu were crystallized by isothermal annealing at 500 °C for 300 s and by exposing to short electric pulse with a duration of 10 ms to study the effect of the annealing rate on their properties. The results obtained showed that electropulse crystallization fundamentally changed the microstructure of the alloys due to almost completely hindering the formation of brittle Ti-Cu phases. This leads to a significant increase in the enthalpy of the martensitic transformation and a considerable shift of the transformation range towards higher temperatures. It was found that reducing the crystallization time dramatically increases the plasticity and shape memory effect of the alloys.

This study analyzes the precipitation phenomenon in the Al-3%Mg-1%Mn alloy and shows that low-temperature annealing at 360 °C enables the decomposition of an as-cast Mn-enriched supersaturated solid solution and precipitation of the quasicrystalline icosahedral phase. Icosahedrons are predominantly formed heterogeneously on the dislocations and dislocation walls. Precipitates with quasicrystalline structure contain Al and Mn, free of Si, and their size varies in a range of 17–71 nm. The Ashby-Brown contrast and the ordered positions of the precipitate and matrix reflections in the SAED and in high-resolution TEM images suggest partial coherency of the quasicrystalline precipitates and aluminum matrix.

The local phase composition was studied in the vicinity of indentations for partially stabilized zirconia crystals doped with rare-earth ions with constant and variable valence. Our aim was to study the effect of co-doping rare-earth ion type (Сe3+, Сe4+, Nd3+ and Yb3+) on the intensity of the tetragonal to monoclinic transition which determines the transformation hardening mechanism in the crystals. We demonstrated the effect of co-doping ion type on the degree of the tetragonal to monoclinic transition. The phase transition is the most intense in ceria ion doped crystals, this being one of the factors contributing to their high fracture toughness.

Hafnium carbide (HfC) and carbonitride (HfC x N y ) nanoparticles were synthesized via reduction of the HfO 2 oxide with calcium hydride in the presence of carbon or carbon/nitrogen, refractory phases were synthesized at 1473 K, respectively. An average particle size of the obtained materials laid in the range of 50 - 90 nm, allowing them to be ranged in a class of nanodispersed powders. The synthesized HfC had a lattice parameter of 0.4640 nm, which corresponds to the HfC 1.0 stoichiometry. The diffraction spectra of the HfC x N y can be described by two isomorphic phases of approximate stoichiometry HfC 0.91 N 0.09 (0.4629 nm) and HfC 0.58 N 0.42 (0.4591 nm). Both HfC and HfC x N y nanoparticles had a predominantly cubic morphology, TEM observations revealed presence of the continuous amorphous film with a thickness of 4 - 5 nm on their surface. Excess of reducing agent and external atmospheric pressure (argon) above the reaction volume were identified as the technological parameters, which strongly affect the quality of the synthesized HfCN powder. Also, it was shown that the formation of refractory HfC and HfCN particles under the presented experimental conditions is controlled by the dissolution-deposition mechanism.

The effect of the precursor and surface modification by sulfate and phosphate groups on the properties of cerium oxide was studied. The obtained materials were characterized by infrared (IR) and Raman spectroscopy, X-ray powder diffraction, scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), thermogravimetric analysis (TGA) with the gas phase composition analysis, Brunauer–Emmett–Teller (BET) method, and impedance spectroscopy. The significant fraction of Се3+ ions at the surface of cerium oxide particles obtained from Ce(NO3)3 promotes the formation of double sodium cerium sulfate and cerium phosphate upon treatment with solutions of sodium hydrogen sulfate and sodium dihydrogen phosphate, respectively. The modification of ceria surface by sulfate groups leads to a decrease in specific surface area and water content of the obtained materials, as well as to a significant decrease in their proton conductivity. CeO2 samples prepared from cerium ammonium nitrate have a significantly smaller particle size and higher conductivity. Its value for cerium oxide modified with phosphate groups increases up to 3.5 × 10−4 S/cm at 65 °C. The effect of hydration degree as well as Ce3+ content on the cerium oxides properties is discussed.

Shape memory effect associated with martensitic transformations is a rapidly developing field in nanotechnologies, where industrial use of systems established on that effect provide greater flexibility on the nanodevice fabrications of various kinds. And therefore it addresses questions to the phase transition phenomena at low scale and its limitations and control. In this report we studied the crystal structure of tapered plates of ${\mathrm{Ti}}_{2}\mathrm{NiCu}$ alloy and the temperature ${T}_{c}$ at which the martensitic transition occurs. We demonstrated that ${T}_{c}$ has a strongly descending character as a function of the plate thickness $h$. The critical thickness value at which the transition is completely suppressed is 20 nm. Moreover, the obtained results for ${T}_{c}(h)$ curves indicate the hysteretic nature of the transition. These findings open the pathway for size limit indications and regime modulations where the alloy-based nanomechanical devices can be tuned to operate more efficiently.

The influence of the atmosphere composition (CO, Ar, air), in which wet synthesis of Pt/C electrocatalyst was carried out, on the structural and morphological characteristics, and electrochemical behavior of electrocatalysts have been studied. For comparison, commercial Pt/C electrocatalysts with the same platinum loading were also studied. It has been shown that the adsorption of CO molecules on the surface of the growing platinum nuclei leads to the decrease in the average size of the nanoparticles and the narrowing of the size distribution in the Pt/C. Homemade electrocatalysts, with the values of electrochemically active surface area being from 94 to 139 m2 g−1 (Pt), prove to be in no way inferior to their commercial counterparts in oxygen reduction reaction mass activity. Durability of the homemade Pt/C samples in accelerated stress tests exceeds durability of the commercial ones.

The crystallographic structure of the wedge-shaped plates of the alloy Ti 2 NiCu was studied by transmission electron microscopy (TEM) in the temperature range 100–400K. The results obtained show that as the plate thickness decreases the temperature at which the martensitic transition occurs decreases too with the transition comes to an end when the plate thickness reaches 20 nm. A plot showing the relationship between the extent of martensitic transition and plate thickness has been obtained, bringing to light the hysteretic character/nature of the transition. The fundamental limitations derived from the theoretical and experimental considerations confirm in principal submicron overall size of the robotic systems based on martensitic transition and shape memory effect.

The mechanisms of stress-induced transformation in ultimately fine-grained Ti-50.61 at.%Ni shape memory alloy subjected to severe cold rolling and short-term post-deformation annealing were studied using transmission electron microscopy and in situ X-ray diffractometry. An unambiguous evidence of a discrete mechanism of stress-induced B2→B19’ transformation in nanograined Ti–Ni alloys with an average grain size down to 2.3 ± 0.2 nm was obtained (this grain size is considered to be the smallest ever obtained for the severe plastic deformation processing route). No signs of continuous transformational lattice changes were found. It has been shown that the critical austenite grain size for the stress-induced transformation exists, and it amounts to ∼4.5 nm in the case of room-temperature tensile straining and further cold plastic rolling.

Carbon supported Pt–Cu and Pt–Co electrocatalysts with increased platinum content on the surface layer of nanoparticles were synthesized by different chemical methods. The compositions, microstructures and electrochemical behaviors of these electrocatalysts were studied using the X-ray diffraction, thermogravimetry, X-ray fluorescence analysis, TEM and cyclic voltammetry. During stability tests (1000 voltammetric cycles in HClO4 solution) the values of electrochemically active surface area (ESA) for Pt–Cu/C catalysts reduced by 34%. Commercial Pt/C catalyst HiSPEC 3000 decreased ESA value by 70% (from 102 to 30 m2g−1 (Pt)) in the similar tests. High stability of the prepared Pt–Cu/C catalysts combined with the high ESA values and ORR activity may be due to the fact that despite a comparatively large size of nanoparticles most of them have a core-shell or hollow (nanoporous) structure. The obtained result demonstrates a great potential for using bimetallic catalyst systems with an uneven surface distribution of metals in nanoparticles as electrocatalysts in low temperature fuel cells and show the way for combining high activity and durability of electrocatalysts.

Ultrafine-grained (UFG) microstructures in Cu–Cr alloys were processed by high pressure torsion (HPT). The improved hardness was accompanied by a reduced electrical conductivity due to the large amount of grain boundaries. The effect of heat-treatment after HPT-processing on the hardness and the electrical conductivity was studied for different chromium contents (0.75, 9.85 and 27 wt%). For low Cr concentration (0.75%) the electrical conductivity increased considerably above 250 °C, however the hardness decreased concomitantly. At the same time, for high Cr content (9.85% and 27%) the hardness was only slightly reduced even at 500 °C, while the electrical conductivity increased to a similar level as before HPT due to grain boundary relaxation and decomposition of Cu–Cr solid solution. Our study demonstrates the capability of SPD-processing and subsequent heat-treatment to achieve a combination of high strength and good electrical conductivity.

The effect of high-temperature annealing in various atmospheres on the change in the valence state of Ce ions as well as on the phase composition and mechanical properties of (ZrO2)0.972(Y2O3)0.02(CeO2)0.008 crystals has been studied. The crystals have been grown by directional crystallization of the melt in a cold crucible. Electron paramagnetic resonance method has been used to identify Ce3+ ions and their relative amount in crystals. The phase composition and structure of the crystals have been studied by X-ray diffraction and transmission electron microscopy. Hardness and fracture toughness of crystals have been studied by indentation. We show that (ZrO2)0.972(Y2O3)0.02(CeO2)0.008 crystals have high values of hardness and fracture toughness. Anisotropy of fracture toughness values has been detected. Thus the observed increase in the fracture toughness of crystals after vacuum annealing is caused by the increasing transformable t phase content and Ce3+ ion concentration. Sequential annealing in oxidizing and reducing atmospheres has led to reversible changes in the valence state of Ce ions as well as in the phase composition and fracture toughness of (ZrO2)0.972(Y2O3)0.02(CeO2)0.008 crystals.

New composite functional material with shape memory effect (SME) has recently been proposed and tested for actuation on microscale. The composite nanotweezers have been designed and tested in manipulation of nano-objects. This report presents the new experiments on shape memory alloy’s (SMAs) properties on submicron scale of dimensions and the development of the technology of nanomanipulation on their bases. The minimal thickness of shape memory layer that undergoes SME was experimentally estimated for Ti 2 NiCu alloy. Impact of the focused ion beam modification of SMA superficial layer on the shape memory properties of micro-sized samples is discussed. Composite actuator of Ni–Mn–Ga magnetic SMA with the size of 20 × 4 × 2 μm 3 was fabricated for the first time and its thermal actuation was experimentally demonstrated ( http://www.smwsm.org/microactuators/NiMnGa.html ).

An enhanced scheme for a functional bilayered composite material with shape memory effect has been successfully applied on the microscale to fabricate a thermally controlled microactuator. Fabrication of cantilever-type microactuators from melt spun ribbon of TiNiCu shape memory alloy included electro-chemical polishing followed by focused ion beam milling and ion-assisted chemical vapor deposition of Pt elastic layer. The smallest working microactuator had a volume of 0:9 m 3 . The structure and thermal stability of the Pt layer have been investigated. The fabricated actuator has been proposed for use as micromechanical nanotweezers for manipulation of submicron- and nano-sized objects. Manipulation of a carbon nanotube bunch has been demonstrated. (Some figures may appear in colour only in the online journal)