The application of aminothioether sorbent — 2-(1,3,5-dithiazinan-5-yl)acetic acid (DTAA) — for the sorption concentration of rare earth elements (REE) from aqueous solutions and solutions of REE-doped hydroxyapatites (HA) and tricalcium phosphates (TCP) has been proposed. The subsequent determination of REE was carried out directly in the sorption concentrate by atomic emission spectrometry with the spectrum excitation in a DC arc (arc AES). It was found that the addition of hydrofluoric acid (10^–7 g/liter) is necessary for the complete recovery of REE from hydrochloric acid solutions. Using model solutions, the conditions of sorption extraction of REE (acidity of solution, sorbent mass, sorption temperature and time) were selected. The ability of DTAA to completely extract REE under selected conditions was confirmed by analyzing real HA and TCP samples using inductively coupled plazma atomic emission spectrometry (ICP AES). The conditions for REE impurities determination, such as generator mode, current strength, exposure time, shape of the electrodes and the distance between them, weight of the sample, were selected. To reduce the matrix effect, the samples were diluted with graphite powder and a carrier, NaCl, was added to the sample to improve the atomization of REE in arc discharge plazma. The limits of determination, relative standard deviation and error were estimated. The results of the developed approach are comparable with those obtained by ICP AES.

The new sample preparation method of rock samples for elemental analysis using emission spectral analysis (ICP-AES) and inductively coupled plasma mass spectral analysis (ICP-MS) is proposed. International standard samples of rock composition GM (granite), JA-2 (andesite), BHVO-1 (basalt) and JR-1 (rhyolite) were the material for the study. The major elements detection in terms of oxides TiO₂, Al₂O₃, MnO, CaO, MgO, Fe₂O₃, Na₂O, K₂O, P₂O₅, was carried out by inductively coupled plasma atomic emission spectrometry (ICP-AES). The ICP-MS method was used to determine the trace element composition of the studied samples: Li, Be, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Zr, Nb, Mo, Cd, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Pb, Th, U. The rocks interaction with the bifluoride and ammonium sulfate mixture at heating up to 350°C for 2 h was applied for complete decomposition of minerals. It was found that at the process all components of the investigated samples are completely dissolved in 13% nitric acid. The elemental analysis for micro- and macro-components of the solutions has shown good agreement with the certified characteristics, which indicates the completeness of the rock components transition into solution. The interaction mechanism of rock minerals with ammonium bifluoride and ammonium sulfate was investigated. It has been established that the combination of fluorination and sulfation stages allows for the effective decomposition of silicate rocks. This is achieved by breaking Si–O bonds with NH₄HF₂ with the formation of simple and complex fluorides and converting insoluble fluorides of the raw material elements into more soluble sulfates with (NH₄)₂SO₄. It was shown that in the sample preparation process silicon being the main rocks component is sublimated in the form of (NH₄)₂SiF₆ as a result of which a significant mass reduction of dissolved salts was achieved. The advantage of the proposed method, for example, compared to acid decomposition, is its rapidity and completeness of opening due to the reduction in the number of stages in the process of decomposition of rocks.

Quantitative assessment of reliability of forensic testing methods (FTM) is not given sufficient attention. In this paper, we use the metrological parameter of validation — «reliability», which is understood as the reproducibility of test results, with multiple repetitions of tests for samples with known characteristics/properties under varying conditions: different operators, use of different equipment, different time. The quantitative characteristic of FTM reliability is the level of false positive and false negative results in the total number of tests. The specificity of control samples for the experiment and the need to take into account the variability of features in them are emphasized, the use of samples with a distinct manifestation of controlled features for validation is recommended. Statistical assessment of test results consists in calculating the indicators (experimental probability) of errors according to the given formulas. Formulas for calculating various indicators related to truene positive and negative results are also given. A binary classification table is provided to present the results of the validation experiment. As an example, the correspondence of the indicators (experimental probabilities) to the true probabilities of events is given for the case of a comparative study of the situation with a pair of samples: «the same source of origin (coincidence)» and «different sources of origin (mismatch)». Formulas are given for the approximate calculation of the confidence limits for the binomial distribution, which most of the binary response methods considered in the work obey. A practical example of calculating the confidence interval in the validation of a specific SEMT method is considered. It is shown that, based on the experimentally established indicators of the correct results of «sensitivity» and «specificity» and in the presence of a priori data on the prevalence of samples by a set of controlled characteristics, using the Bayesian formula, it is possible to calculate the proportions of false positive/negative analytical signals (FPS and FNS). Low values of the FPS and FNS indicators indicate the correctness of testing or the correctness of the decision made and the suitability of the method for its intended purposes.

The purpose of this work is to evaluate the effect of crystallohydrate water in the composition of alkalis: potassium hydroxide and sodium hydroxide on the process of selective etching of single-crystal gallium arsenide plates used to identify dislocation etching pits on the crystallographic surface {100} as part of technological quality control of single-crystal GaAs ingots. Selective etching was carried out in melts of alkali crystallohydrates (KOH · H₂O, NaOH · H₂O), as well as in melts of anhydrous alkalis (KOH, NaOH). As a result of the experiments carried out, it was proved that when etching in anhydrous potassium and sodium hydroxides, the etching process of gallium arsenide plates does not proceed selectively — there is an almost uniform dissolution of the entire surface. At the same time, the formation of erosion zones occurs in the melt of KOH · H₂O crystallohydrate — dislocation etching pits characteristic of the crystallographic plane {100}. In the melt of NaOH · H₂O crystallohydrate, the selective etching process does not proceed, all other things being equal, under experimental conditions. As a result of the analysis of the experimental data, the mechanism of selective etching was identified and justified, which consists in the course of high-temperature hydrolysis of the {100} GaAs surface with the participation of crystalline hydrate water residues in the composition of KOH · H₂O. It has been shown that the temperature and the presence of water in the composition of the selective etchant are the determining factors of the course of this process. The use of the results of this work will make it possible to control the process of selective etching of GaAs plates to a greater extent, as well as to standardize the methodology of their technological control.

The use of single-element eddy current transducers in eddy current testing devices limits the flaw detector performance, since the formed eddy current contour corresponding to the average turn of the eddy current transducer coil is limited by the area of this turn and the scanning speed of the tested surface. The presence of several single-element eddy current transducers inevitably has a negative mutual influence. The paper presents the results of increasing the performance of a three-phase eddy current flaw detector (ECF), including increasing the scanning speed and reducing the mutual influence of single-element eddy current transducers. A three-element three-phase eddy current transducer is used as a source of the informative parameter in the ECF, represented by three single-element transformer transducers, the excitation windings of which are connected to a source of three-phase alternating high-frequency voltage. Based on the Wagner – Evans theory, a mathematical model is proposed that describes the formation of the so-called asymmetric system when the symmetry of a three-phase voltage system is violated. This system can be represented as a sum of symmetric components: direct, reverse, and zero sequences. Taking into account the mathematical model, a structural diagram of the eddy current tester has been developed. The diagram assumes that the exciting windings of the single-element converters that make up the flaw detector are connected to a source of three-phase symmetrical voltage, and the measuring windings receive the introduced voltage in the form of a three-phase system when the eddy current converter interacts with the test object. In addition, using a filter for symmetric components, the voltage of the reverse sequence is isolated, which is formed only when the symmetry of the introduced voltages on the measuring windings of the three-phase eddy current converter is violated and can be used as an informative parameter for detecting such defects as, for example, discontinuities in the test object. The obtained results can be used in eddy current flaw detectors based on electromagnetic non-destructive testing methods to detect defects of various natures.

The structural-phenomenological concept (SPC) and model of the evolution of destruction of a composite material are considered, connecting its load-bearing capacity with the kinetics of redistribution of the weight content of micro, meso and macroscale damage during loading. By monitoring changes in the values of partial accumulation of damage in the structure of the material at different scale levels in the loading mode, and comparing them with threshold values, it is possible to control the actual state of the load-bearing capacity of the product. The correspondence between the surface of micro, meso, macro-destruction of structural bonds of a structural material and the energy parameters of the acoustic emission pulses recorded in this case, forming in the field of descriptors of relative energy (E_i) and maximum amplitude (u_m), clusters of the lower (L), middle (M), and upper (H) levels with boundaries: E_i < 85 dB, u_m < 55 dB; E_i = 85 – 115 dB, u_m = 55 – 80 dB; E_i > 115 dB, u_m > 80 dB. An algorithm and software (software) have been developed that controls the dynamics of the redistribution of parameters of partial activity (Ń_i) and weight content (W_i) of location pulses in energy clusters characterizing the kinetics of micro-, meso- and macro-damage «in situ» of violation of the structural bonds of a product under loading mode. By comparing the current values of the most informative parameters W_L and W_M, with their threshold values [W_L] and [W_M], corresponding to the state of the product when the material is destroyed, we get the opportunity to control the actual level of the load-bearing capacity of the structure. The developed concept, algorithm and software were used to evaluate the load-bearing capacity of the panel mesh structure during compression tests under loading conditions.

The article described studies of the consequences of hydrogen corrosion of the steel walls of a chemical reactor during operation. Service life is 100,000 h. The walls are made of steel 09G2S. They worked under external thermomechanical load at low pressure of a hydrogen-containing internal environment (0.05 MPa). A comparison was made of the data obtained during the study of samples cut from the walls of the reactor with the data obtained during testing of isolated, hydrogen-charged samples made of steel of the same grade. New data were obtained regarding the influence of hydrogen and external load on the mechanical properties, structural and chemical transformations of steels. The differences between operational hydrogen corrosion and the consequences of hydrogen charging and from numerous previously published results were the increase in the ductility of the metal after operational hydrogen degradation (it becomes higher than that of new samples made of steel of the same grade) and the formation of a brittle fracture of this metal at a sufficiently high the value of its impact strength. It was also discovered that with complete decarbonization of some microstructure elements during operation, observed under a microscope, the average carbon concentration does not change, carbon accumulates at the grain boundaries.

Nothing similar is observed in hydrogen-charged samples. Assumptions have been made about possible mechanisms, chemical reactions, the structure of the carbon formed in this process and its effect on the mechanical properties of the metal.

The purpose of the work is to solve the problem of constructing schemes and models taking into account the peculiarities of conducting full-scale strain gauge studies of structures operated at temperatures up to 550°C, in the elements of which local elastoplastic deformations may occur. To solve the problem, the results of strain gauge studies of a heat exchanger, the elements of which are subjected to intense thermal effects from a liquid metal coolant with variable temperature, were used. Based on the analysis performed, schemes for constructing measuring systems are proposed that are used at various stages of research and allow the use of equipment with alternative methods of powering strain gauge transducers. The use of alternative schemes for constructing a measuring system provides data on changes in the metrological characteristics of primary transducers directly in the process of a full-scale experiment. For this purpose, the principle of dependence of the magnitude of the dissipation of the temperature characteristics of strain gauges on changes in the temperature components of their output signals is used. To construct a mathematical model of creep of strain gauges at high temperatures, experimental results were obtained that made it possible to substantiate the exponential model of changes in the uninformative output signal associated with creep. As a result of the analysis performed, a method for determining the creep of strain gauges, based on measuring the output signals under cyclically changing deformation, was substantiated. Algorithms for taking into account errors associated with the creep of strain gauges under conditions of non-stationary thermal loading of the heat exchanger under study are proposed. As a result of the research, an adjustment was made to the experimentally obtained functions for changing the stress state of the structure under study. The results obtained make it possible to increase the reliability of the assessment of the strength and service life of power engineering structures, carried out on the basis of field studies.

The most important regularity of plastic deformation process is its tendency to localize at all stages. Localization accompanies plastic deformation from beginning to end (until failure), taking on various regularly changing forms along the way. Localization of plastic flow can cause destruction of materials during technological processes associated with large plastic deformations. In this regard, it is necessary to clarify the laws governing the localization of plastic deformation throughout the entire length of the strain — stress curve from the yield strength to the strength limit. Knowledge of the patterns of localization of plastic flow will allow us to formulate a criterion for predicting the plasticity reserve of materials. The use of the speckle photography method has proven promising in studying the characteristics of plastic deformation of metals. The spatial resolution of this method corresponds to the level of optical microscopy with a significant advantage in the size of the field of view. This method makes it possible to obtain the values of the components of the plastic distortion tensor of the working surface of the sample with an interval of 30 sec (the maximum displacement of surface points is 100 μm) and, ultimately, to analyze the evolution of localization patterns, as well as to determine the kinetic parameters of moving localization foci, which is its main advantage. In this work, the kinetics of development of localized plastic deformation sites in the polycrystalline copper-nickel alloy Cu-40%Ni-1.5%Mn was studied using speckle photography. It was possible to find out that the forms of localization are completely determined by the laws of strain hardening of the material operating at the corresponding stage of the process. The localization of plastic flow in a copper-nickel alloy has an autowave character. At the same time, at the yield site, stages of linear and parabolic strain hardening, as well as at the pre-fracture stage, the observed localization patterns are different types of autowave processes. Analysis of the characteristics of such processes made it possible to measure their propagation speed and wavelength. In conclusion, a method for identifying the source of destruction to predict the ductility reserve of metals is proposed.