The results of measurements of the bulk diffusion of tracer oxygen atoms in the oxides LnMnO3+δ (Ln = La, Nd, Sm) in the temperature range 400 – 750°С are presented. The measurements were carried out on micro-and nanopowders. Nanoscale powders were prepared by mechanical activation. A method based on the study of the kinetics of oxygen isotope exchange between the powder and gaseous oxygen enriched with 18O isotope was used to obtain data on the diffusion coefficients. The average concentration of 18O isotope in the powders was measured using NRA technique. The obtained diffusion coefficients lay in the range of 10-21 - 10-24 m2/s, the diffusion activation energy for all the oxides have been close to 1 eV. These results suggest that the migration of tracer oxygen in oxides LаMnO3+δ, NdMnO3+δ and SmMnO3+δ at low temperatures is realized via structural defects. As for the oxide LaMnO3+δ, its oxygen diffusion coefficients at low temperatures have been lower than the values extrapolated from high temperatures. Such behavior of diffusion properties has not been previously observed in other metal oxides. In this regard, the vacancy formation energy in the rare earth manganites has been supposed to increase with decreasing temperature.

The thermophysical properties of the Ti-5Al-5V-5Mo-3Cr-1Zr titanium alloy in a wide range of temperatures from room temperature to 1000°C have been studied by the methods of differential scanning calorimetry, the laser flash method, and dilatometry. The obtained data on heat capacity, thermal diffusivity, and thermal expansion have been used for calculating coefficient of thermal conductivity. The sequence and temperatures of structural transformations during heating of the alloy have been established. It has been shown that the studied alloy possesses a coefficient of thermal conductivity that is 3.5–4 times smaller than that of pure titanium.

The effect of mechanical processing in different types of activators on the structure and physicochemical properties of the oxides LnMnO 3+δ (Ln = Sm, Nd, La) has been studied.The optimal modes of mechanical activation for transformation the oxides under consideration to nanostructured state have been defined.Mechanical processing has been shown to cause a significant change of Jahn-Teller distortion parameters and temperatures of the cooperative Jahn-Teller phase transition.The presence of connection between redox processes and destruction of orbital ordering has been demonstrated.Very low values (10 -21 -10 -24 m 2 /s) of the oxygen bulk diffusion coefficient have been obtained for the oxides under consideration in the temperature range of 400 -750°C.The diffusion activation energies are close to 1 eV, indicating the oxygen diffusion proceeds through structural defects at these temperatures.

sotope exchange of oxygen 18О2 with oxides NdMnO3+δ was investigated. The oxide was obtained from oxides Nd2O3 and Mn2O3 using a ceramic technology with annealing in air at 1400°C for 90 hours followed by cooling in a furnace. A planetary mill AGO-2 with a centrifugal factor of g = 60 was used for mechanical treatment of oxides. The study of isotope exchange was carried out by nuclear microanalysis. The concentration of the isotopes 18O and 16O in oxides was determined using a Van de Graaff accelerator and 18O(p, α)15N and 16O(d, p)17O* reactions at the energies of incident beams 762 and 900 keV. Isothermal annealing of powders was carried out in oxygen, enriched to 80% by the isotope 18O. It was established that the concentration of the isotope 18O in mechanically activated powders was several times higher than in the initial micropowder under the same conditions of annealing. The effect increased with increasing of mechanical activation time (30 - 300 s). The isotope exchange parameters connected with the processes at the boundaries of the particles of mechano-activated powder and within their volume were analyzed.

The results of preliminary experimental researches of possibility of metallurgical processing of ores of Actually Kachkanarsky deposit are presented in the work.

Magnetic properties of the initial (pre-milling) and mechanically activated SmMnO3 polycrystalline powders were studied. Magnetization measurements were carried out in the temperature range of T = 4–300 K and the magnetic fields up to ±20 kOe. The powders were subjected to both high-energy and low-energy ball milling. The samples studied were analyzed by X-ray diffraction method and X-ray photon-emission spectroscopy. It was found that all the mechanically activated powders SmMnO3 have significantly different magnetic characteristics (transition temperatures, coercive forces, remanent magnetizations) in comparison with initial samarium manganite. The inversion of field cooled (FC) and zero-field cooled magnetizations was observed for the initial sample only. Mechanically activated samples demonstrate positive FC magnetizations in the whole measured temperature range. It is established that the magnetic properties of the samples are strongly dependent on the mode of mechanical activation. Much noticeably, modifications in magnetic characteristics of powder studied were obtained in the case of low-energy mechanical treatment.

Oxygen isotope exchange (OIE) between nanosized powders of the aluminum oxide Al2O3 and oxygen-containing gases 18O2 and C18O2 has been studied in a temperature range of 100–500°C. The concentration of the oxygen isotope 18O in the powders was determined by nuclear microanalysis technique (NRA). It has been shown that for this oxide the OIE exhibits a significant size effect. It has been established that the OIE of the Al2O3 nanopowder is characterized by a specific time dependence of the concentration of the 18O isotope at the surface of grains and by a low level of the content of 18O in the oxide. A linear dependence of the concentration of 18O in the nanopowders on the specific surface of the nanoparticles has been revealed. The experimental data are discussed in terms of several models of the process of isotope exchange.

sotope exchange of oxygen 18О2 with oxides Mn2O3 and Mn3O4 was investigated in the temperature range of 300700°C. It was established that the content of the isotope O18 in mechanically activated powders was noticeably higher than in the initial ones. Already at relatively low annealing temperatures isotope exchange leads to nearly the maximum possible under the given conditions replacement of atoms 16O to 18O. The isotope exchange parameters connected with the processes at the boundaries of the particles of mechanoactivated powder and within their volume were determined.

The peculiarities of the Faraday rotation in the imperfect garnet-type crystals for which the lattice irregularities are represented by the mixed valence clusters of transition metal ions are analyzed. The model takes into account the cubic and low symmetry crystal fields acting on the metal ions and migration of the "extra" hole. The electric dipole transitions in these types of clusters with migrating hole coupled to the spin core through the double exchange mechanism are shown to lead to a significant magnetooptical activity in the visible range of spectrum. The intensity of these transitions can be comparable or higher than those for the magnetic dipole ones in the same range of frequencies.

The formation of gas-saturated defects in titanium alloys during vacuum-arc remelting is studied theoretically and experimentally. The defects of a metallurgical origin that were detected upon long-term monitoring of a commercial process of production are considered. The light-element contents are determined with a high-locality nuclear accelerator microanalysis technique. A theoretical model is developed to describe the dissolution of solid gas-saturated inclusions in liquid titanium; it is based on a mechanism of diffusion of modifying defects in melting. The critical parameters of defect sources (defect size, nitrogen concentration in a defect) at which defects do not dissolve in titanium upon melting are determined. The obtained dependence of the average light-element concentration in a defect on the defect size is explained.

The subject of investigation in this work is oxygen isotope exchange (OIE) between oxides and oxygen-containing gases 18О2 and С18О2. OIE studies yield information about the rate of processes on the gas – solid interface and oxygen self-diffusion in oxides. In turn, the surface processes can involve some elementary stages, in particular, physical and chemical adsorption. Several types of diffusion processes can be observed also inside oxides, for example, volume and grain boundary diffusion. OIE investigations are of much practical interest, for example, in connection with the problems of catalytic oxidation of metals and development of materials for chemical and electrochemical devices (fuel cells, electrolyzers, sensors, hydrogen storage devices, devices for separation of gas and isotope mixtures, etc.). Two experimental approaches to OIE examination are known. The pioneer approach was based on measurements of the isotope composition of a gas mixture interacting with oxide. In the alternative approach developed in the last decades, the isotope composition of the oxygen subsystem of oxides was measured, which was studied usually by secondary ion mass spectrometry (SIMS) and nuclear microanalysis (NRA). The present work is devoted to the examination of the isotope composition of solid-state samples. The overwhelming majority of studies by means of this approach were performed on bulk samples. A distinguishing feature of this work is its orientation toward isotope exchange examination in nanoscale oxides. As will be shown below, this results in novel or supplementary data on the surface reaction rates during isotope exchange and the rates of diffusion processes in oxides. Moreover, the investigations into oxygen isotope exchange in oxide nanomaterials are of great practical importance. It is not improbable that the use of nanomaterials may lead to favorable changes in the functional properties of oxides when it is necessary to increase the quantity of absorbed gas or to increase rates of gas absorption or extraction etc.

An investigation has been undertaken of the structural characteristics of the manganese oxides to understand these characteristics affected by mechanochemical treatment conditions. Chemically pure manganese (II, III) oxides and their mixtures were used as the initial components.

We have studied the effect of grinding in planetary mills on the phase composition, morphology, and water content of hydroxyapatite powder. The results indicate that milling for even relatively short times, which reduces the average particle size by a factor of 2, causes the monetite present in the unmilled powder to disappear and reduces the crystallite size of the hydroxyapatite. The fraction of nanoparticles in the powder is then 98% and remains constant during further milling. Milling for longer times leads to hydroxyapatite amorphization. For an average size of large particles R ≥ 1 μm, the surface area of the particles per unit volume, E (cm−1), is determined only by R (E ∼ 1/R).

Specific features of the structural phase transitions of the first order were investigated in nanosized crystals with Jahn-Teller ions. As an example the phase transitions of martensite type with changes in symmetry from a cubic to a tetragonal one have been considered. The Kanamori model was used to take into account the size of nanocrystallites and the distribution of cations over non-equivalent crystallographic sublattices in such systems. It was shown the temperature and the latent heat of the transition decrease significantly for the nanoscaled grains. A possibility of multi-phase state for nanocrystalline materials was considered.

The thermal expansion of samples of high-density nanoceramic CuO is investigated. The nanoceramic is obtained by the method of loading coarse-grained copper oxide by spherically convergent shock waves. Anomalous behavior of the thermal expansion coefficient α of the oxide is observed in the temperature region below 50K (α⩽0). The appearance of these anomalies is explained by the presence of orientationally degenerate tunneling centers and/or low-temperature phase separation.

The electrochemical behavior of perovskite type LaMnO3 (LMO) oxides with different mean particle size was studied by voltammetry with the use of a carbon paste electroactive electrode. Three stages of electrochemical reduction were recognized. The first two of them are related to the release of oxygen from the crystal lattice in the range of two side nonstoichiometry of LaMnO3±δ whereas the final stage is conditioned by the decomposition of LaMnO3-δ into new phases. The nature of these phases and their formation mechanisms are different for nano- and microparticles. The utmost size effect appears on cathodic curves recorded from the stationary potential. The effect is not only due to the size factor but also due to the difference in electrochemical properties of nano- and microparticles. While the decomposition of LaMnO3 microparticles proceeds into La2O3 and MnO oxides, the nanoparticles decompose through the intermediate stage of Mn3O4 formation in accordance with the transformation sequence principle.