Due to unique electromagnetic and magneto-optical properties, iron- yttrium garnet (Y₃Fe₅O₁₂, YIG) and its solid solutions are used in the production of film structures for a new field of spin electronics, known as magnonics. It is essential to control the chemical composition of synthesized YIG, including both primary (Fe, Y) and trace elements (Li, Be, B, Na, Mg, Al, Si, P, K, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Zr, Nb, Mo, Cd, Sn, Sb, Te, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Tl, Pb, Bi, Th, U), because the presence of impurities above 10^–2 wt.% significantly broadens the ferromagnetic resonance line of the films and deteriorates the properties of the film structures. It is shown that the use of two methods, atomic emission (ICP AES) and mass spectrometry with inductively coupled plasma (ICP MS), under selected conditions of analysis, allows for the accuracy of its results and a wide range of detectable elements. The peculiarities of the synthesis of YIG film structures on a gallium arsenide substrate using a novel none-epitaxial method proposed by the authors have been studied. The effect of YIG impurity composition on the structure and properties of the resulting films is shown. To prevent the interaction between Y³Fe⁵O¹² and GaAs at the interface during film crystallization, a barrier layer of aluminum oxide was pre-sprayed onto the substrate. The ferromagnetic resonance spectra of Y³Fe⁵O¹²/AlOx/GaAs films obtained by various methods have been studied. It was found that the width of the FMR line for films obtained by spraying YIG single crystals is 30 – 40 Oe less than for films contained impurity elements.

An approach to the determination of manganese separately on the surface and in the volume of SnO₂/MnO_x nanocomposites is proposed to establish the «synthesis conditions – composition» relationship. The approach includes the determination of the total content of Mn and Sn in solutions of composite and Mn on its surface by the ICP MS, followed by the calculation of the additive content in the volume of the material. Solutions of HCl, H₂C₂O₄, Na₄P₂O₇, and formaldoxime were studied as acid reduction etching reagents for the determination of manganese on the surface. It is shown that when the surface of the samples is treated with a formaldoxime solution at 20°C, manganese dissolves on the surface of the sample, while tin does not pass into the solution. A 4- step temperature program transferring SnO₂ synthesized at high temperature to a solution using a mixture of acids in an autoclave with microwave intensification has been developed for subsequent determination of the Mn and Sn content by the ICP MS method. It is shown that the application of internal Mn/Cu and Sn/Rh standards makes it possible to reduce the relative standard deviation of the analysis results (s_r) to 0.02. Based on the obtained results of the determination of Mn and Sn on the surface and the total content, the distribution of manganese in SnO₂/MnO_x composites between the surface and volume is calculated. It is shown that manganese is distributed unevenly between the volume and the surface of the samples. As the annealing time increases, the manganese content on the surface of the composite decreases due to the diffusion of the additive into the SnO₂ particle.

A technique for stripping voltammetric determination of arsenic on a gold-film electrode (GFE) with a simplified procedure for preliminary reduction of As (V) to As (III) is proposed. A mixed reducing reagent based on sodium metabisulfite and thiosulfate was used to convert arsenic into an electroactive form, allowing complete quantitative reduction to be achieved within 10 min. The GFE was prepared ex situ by electrodeposition of a gold layer on a rotating glassy carbon electrode (GCE) substrate using potentiostatic electrolysis 300 sec from 1 mM HAuCl4 solution at a potential of –300 mV. With the selected optimal parameters of analyte electroaccumulation, the linear range of the arsenic electrodissolution current was observed from 10 to 200 μg/L, the detection limit was 1 μg/L with an accumulation time of 120 s. The effect of the presence of Cu (II), Bi (III), Pb (II), Fe (III), Mn (II), Zn (II), Cl– ions on the arsenic signal was estimated. To eliminate the contribution of interfering influences to the results, a background electrolyte was used, which was a mixture of 1 M acetate buffer and 0.01 M EDTA. To standardize the technique the measurement quality indicators were assessed in accordance with RMG 61–2010. The proposed technique was applied to determine arsenic in natural water, seafood and inorganic materials; the accuracy of the analysis results is confirmed by atomic absorption spectrometry with electrothermal atomization.

Polychlorinated biphenyls (PCBs), persistent organic pollutants, have become widespread during their production and use as dielectric fluids, due to transboundary transport via water, air, and the food chain. Nitro derivatives of PCBs — secondary pollutants — also pose a hazard to the environment and humans, but data on their thermal properties are insufficient. The aim of this study was to investigate the thermal properties of nitro derivatives of PCBs. Synthesized nitro derivatives of PCBs, which are components of technical mixtures of the brands «Trichlorbiphenyl» and «Sovol», were analyzed. Using simultaneous thermal analysis it was established that the studied mixtures of nitro derivatives are prone to sublimation rather than thermal decomposition. Onset temperatures of sublimation and enthalpies of sublimation were determined. It was found that as chlorine substituents accumulate in the biphenyl structure, the thermal stability of the nitro derivatives decreases. Furthermore, with increasing ambient temperature, polychlorinated nitroarenes can migrate into atmospheric boundary layers characterized by temperature inversion and increased pollution. The obtained results can be used to improve methods for monitoring nitro derivatives of polychlorinated biphenyls in environmental samples.

When obtaining a finished product with minimal porosity using compaction methods, it is necessary to evaluate the material’s formability. Metal-ceramic materials, especially refractory ones, are characterized by a very narrow temperature-time interval in which they possess the ability for plastic deformation. The paper presents the results of a study on the high-temperature forming of composite metal- ceramic materials based on TiC with a metal matrix. A high-alloy steel powder Kh18N15M was used as the metal matrix in an amount of 10 – 70 wt.%. Powder materials (titanium and carbon black) were used in the synthesis of the metal-ceramic composite, which form titanium carbide through direct exothermic interaction. The formability of the synthesized material was determined using the free SHS-compression method. The criterion was the deformation degree — the ratio of the difference between the areas of the deformed sample and the initial workpiece to the area of the deformed sample. It was found that with an increase in the amount of metal binder from 10 to 60 wt.%, the combustion temperature and rate decrease by 1.6 and 23 times, respectively, and with a metal binder content of 70 wt.%, synthesis is impossible. It is shown that, regardless of the metal matrix content in the material, its structure and phase composition do not change qualitatively. The obtained results can be used to improve the methodology for synthesizing compact composite materials based on TiC with a Kh18N15M metal matrix to achieve minimal porosity.

The development of microwave electrical technologies requires accurate and reliable measurements of the dielectric properties of materials. This is especially important for materials with a wide range of dielectric constant and dielectric loss tangent values, for which traditional analysis methods are either insufficiently sensitive or excessively complex. The purpose of this work is to determine the dielectric characteristics of materials using a volume resonator at a frequency of 2.45 GHz. The parameters of the resonator, such as the resonant frequency and quality factor, were analyzed to determine the dielectric properties of the materials. Numerical modeling of the resonator was performed to study the distribution of electric and magnetic fields of the main mode TM010. The analysis of the excitation conditions of the main and parasitic modes revealed their influence on the accuracy of measuring the parameters of the resonator and determining the dielectric properties of objects. It is shown that the calculated values of the dielectric constant and the tangent of the loss angle of materials are in good agreement with the literature data (the error is ~3 and ~6%, respectively). The results obtained can be used to determine the dielectric characteristics of materials in a wide range of values by the resonator method and to study the electrophysical properties of materials and media.

Transition metals, as trace elements, play an important role in redox reactions in the human body and act as catalysts in enzymes, and exhibit pronounced biological activity in the form of nanoparticles. The paper presents the results of a study of the chemical composition and structure of nanoparticle fractions using X-ray methods. The physicochemical parameters of copper nanoparticles obtained by plasmochemical method were analyzed. The nanoparticle sizes were determined by backscattering and scanning electron microscopy. The phase composition of nanoparticles of various dispersities and the chemical composition of their surface have been qualitatively determined and quantified. It has been established that the surface of copper nanoparticles is represented by oxide forms. The ratio of oxide forms in the total volume of coarse and fine nanoparticles was determined. The results obtained can be used in studies of the processes of modification of the surface of nanoparticles by various functional groups, and the adsorption of high-molecular-weight surfactants on the surface of nanoparticles to increase biocompatibility.

Northern regions of Siberia and the Far East are characterized by extreme natural and climatic conditions, including significant seasonal (from –60 to 40°C) and daily (up to 30°C) temperature fluctuations with repeated transitions through 0°C, high humidity and intense solar radiation. The paper presents the results of a study of the climatic resistance of high-density polyethylene (HDPE) in difficult natural and climatic conditions. HDPE grade 273-83 containing the stabilizer grade SO-4 was studied. Full-scale exposure at the test site was carried out for 15 months. When studying the relative elongation at break, it was found that materials containing 1.0 wt.% SO-4 have the highest climatic resistance. In addition, the stabilizer makes it possible to significantly increase the resistance of HDPE to oxidative processes, without participating in the Norrish II reaction, accompanied by the formation of terminal vinyl groups. The analysis of the melt flow index showed that during aging at the initial stages (up to 3 months), predominantly crosslinking reactions of macromolecular chains occur in the materials. With increasing exposure time, reactions accompanied by macromolecular chain scission reactions begin to prevail over crosslinking processes, leading to a decrease in melt viscosity. The use of a stabilizing additive makes it possible to reduce the rate of both competing reactions. It was found that the efficiency of the stabilizer is determined by its optimal concentration, which depends on the solubility of the additive in the polymer matrix. An insufficient amount of the stabilizer leads to its premature consumption during inhibition of radical chain reactions occurring under the influence of UV radiation and oxygen of air. With an excess, part of the additive appears on the surface of the material, causing the formation of internal defects leading to embrittlement of HDPE. The obtained results can be used to assess the reliability and durability of parts and structures made of HDPE and stabilized materials based on it under direct exposure to specified natural and climatic conditions, to assess their service life and prevent equipment failures during operation.

It is noted that experimental and computation studies of kinetics of stresses and strains and properties of materials are an essential principle for working out and application of criteria of cyclic fracture, and also for carrying out of the refineded computations of structures parts on low cycle strength. Improvement and evolution of these methods in the direction of the accounting of factors of various service conditions, including forms of the loading cycles influencing on characteristics of hardening or softening of material is based on establishment of patterns of relationship of change of basic parameters of the state equations describing a kinetics of local cyclic elastic- plastic strains depending on parameters of service cycles of a loading. At the same time the relation between stresses and strains at a cyclic loading outside elasticity is characterized by diagrams of a cyclic elastoplastic deformation in the parameter of number of half-cycles (cycles) of a loading. The greatest distribution for the description of diagrams of a cyclic deformation outside elasticity in established practices was gained by their power approximation which key parameter is the module of cyclic hardening — an exponent of power dependence between relative values of cyclic stresses and strains in a cycle. For the choice of basic parameters of the state equations in this case along with characteristics of stress-strain states the data on mechanical properties of materials received at their short-term and long static and cyclic tests are initial. The analysis of the obtained computation and experimental data shows that consideration and establishment of patterns of relationship of a kinetics of the cyclic hardening module in relation to the diagrams of a cyclic elastoplastic deformation of austenitic stainless steel received experimentally in a wide range of temperatures and parameters of a deformation allows to characterize its kinetics in view of forms of cycles of a loading including effect both hardening, and softening of material owing to action of high-frequency strain at the two-frequency mode of a loading with the level of cyclic stresses, equal with the single-frequency forms of a cycle.

The use of modern pendulum impact testers capable of recording specimen deformation curve during loading has made it possible to consider the impact bending test not only as a standard type of technological acceptance test for assessing metal quality in accordance with regulatory requirements. Recording curves in force-displacement coordinates provide an additional opportunity to obtain a more objective assessment of metal fracture resistance, and also generally expands the understanding of the fracture mechanism, especially in the transition temperature range. In this regard, it is of interest to analyze dynamic impact bending curves to obtain information about the nature of fracture, in particular about the quantitative ratio of ductile and brittle components in the fracture surface. In this study, using the example of steel grades 06GFBA, 26KhMFA and 35KhGMA, developed as a material for oil and gas pipes, it is experimentally shown that using force values at characteristic points on a pre- smoothed dynamic impact loading curve allows for a high-accuracy determination of the shear fracture appearance (SFA) by the evaluation method without visual analysis of the fracture surfaces of the failed specimens. Research has shown that the brittle component in the fracture occurs at the moment a sharp drop appears on the curve while the magnitude of the specimen deflection characterizes its resistance to the initiation and growth of a brittle crack during fracture. Temperature dependency of characteristic force and displacement values is determined. The pronounced dependence of the parameters of the impact bending curve on the test temperature can serve as a qualitative indicator for identifying incorrectly determined characteristic point values. Ductile-to-brittle transition curve is plotted by fitting calculated SFA values and ductile-to-brittle transition temperature is obtained. A comparison of ductile-to-brittle transition curves constructed from proposed and experimental (fractographic measurement) SFA data showed similar values of the ductile-to-brittle transition temperature. This confirms the possibility of using the proposed method for rapid and qualitative assessment with satisfactory approximation, especially when dealing with a large number of specimens, and also as an additional control method during acceptance tests.

A technique for determining the mechanical properties of aluminum alloys by instrumented indentation with a ball indenter was developed. The technique is based on the correlation between the maximum equal strain during specimen tension and the indentation strain hardening parameter in the plastic region. This made it possible to obtain a formula for calculating the ratio of yield strength to ultimate strength using the strain hardening parameter. The values of the loading ratio necessary to achieve the maximum Brinell hardness, which is proportional to the ultimate tensile strength with a constant conversion factor for the tested aluminum alloys, were established. The ultimate tensile strength value and the ratio of yield strength to ultimate tensile strength allow calculating the yield strength of the alloy, which is usually determined quite difficult by indentation according to other known methods. Given the unambiguous correlation between the ratio of yield strength to ultimate tensile strength and the strain hardening parameter, it is proposed to use it as a diagnostic parameter in the estimation the degree of fragility of structural materials. The higher this parameter, the more prone the material is to brittle fracture. The proposed method for determining mechanical properties by instrumented indentation is quite simple and easily responds to automation, which increases the productivity of monitoring the mechanical properties of aluminum alloys.

Engine oil requires frequent replacement, so it is necessary to diagnose the mechanochemical process of wear (processing) of detergent additives. The paper presents the results of a study of the wear process of detergent additives and the natural aging of M-6z/12G1 engine oil after friction treatment and the appearance of wear particles at the initial stage of engine operation. Metallography and nuclear magnetic resonance methods were used in the tests. It was found that the relaxation time of protons of the engine oil under study decreases with an increase in the number of ferromagnetic particles in its colloidal solution, which are wear products. At the same time, as the number of wear particles in the oil increases, the size of the molecular complexes of detergent additives increases due to their coagulation (achieving a minimum energy state). The complexes envelop the wear particles and keep them suspended in a colloidal solution. It is shown that after mechanical friction for 0.5 and 3.0 h and an increase in the number of wear particles, 10-day exposure (with the engine not running) and subsequent shaking, the spin-spin relaxation time of the oil does not increase, but, on the contrary, is significantly reduced (by 1.6 and 2.8 times, respectively) due to oxidative processes occurring during the interaction with oxygen in the air (natural aging). After natural aging, oil that does not contain wear products loses its performance properties 2 – 3 times slower than its spent and aged counterparts. The results obtained can be used for tribodiagnostics of the initial wear stage of detergent additives in engine oil.

One of the main problems in designing composite structures is the creation of reliable fastening methods, since traditional drilled holes destroy load-bearing fibers, leading to significant stress concentration and reduced strength. The aim of this work is to develop and illustrate a bio-inspired method for fastening composite parts by creating a curved reinforcement structure that mimics the knot zone in wood. It is shown that an iterative algorithm for computer modeling of fiber trajectories «flowing» around the hole, allows the construction of a reinforcement structure in which the «fiber overload coefficient» is only 1.3 instead of a stress concentration coefficient of about five in a unidirectional carbon fiber plate with a circular hole. Experiments on wooden samples with removed knots and drilled holes, as well as on composite samples with curved reinforcement made using 3D printing, confirmed the effectiveness of the proposed approach. Preserving the reinforcement structure in the knot area means that the hole from the removed knot does not affect the strength at all, and failure occurs away from the hole. The results confirm the promise of using bio-like joints to significantly increase the load-bearing capacity and durability of composite fasteners, which is especially important for large aerospace structures.