Elemental analysis of ferromanganese formations (first, determination of the ore elements) is a necessary stage in the development of ore deposits. A technique for X-ray fluorescence quantitative determination of iron, manganese, cobalt, nickel, copper and zinc in oceanic ferromanganese formations (nodules and crusts) is proposed. The study was performed on wavelength-dispersive spectrometer S4 Pioneer (Bruker AXS, Germany) with LiF (200) crystal and scintillation detector. To plot the calibration curves, sets of certified reference materials of ferromanganese nodules, cobalt-bearing ferromanganese crusts and pelagic sediments, previously dried for 24 hours at 105°C to remove hygroscopic moisture were used. Two sample

preparation techniques were compared: pressing of powder samples on a boric acid substrate and homogenization by fusion with lithium tetraborate in a ratio of 1 : 30 in an electric furnace at 1050 °C. For each sample preparation technique spectral overlaps and matrix correction methods (theoretical and empirical) were considered and optimal calibration curves for determination of ore elements were selected. The accuracy of the X-ray fluorescence technique was assessed in analysis of a certified reference material FeMn-1 and reference ferromanganese nodule sample using atomic absorption spectrometry on an M403 spectrometer (PerkinElmer, USA). Both homogenization by fusion and analysis of pressed samples provide quantitative X-ray fluorescence determination of the main ore elements and can be used to assess the industrial significance of oceanic ferromanganese formations.

The results of sorption preconcentration of some heavy metal (HM) ions with their subsequent determination in natural and drinking water by electrothermal atomization atomic absorption spectrometry (ETAAS) are presented. The sorption and desorption (0.01 – 1 M HNO₃) of lead, copper, iron, cobalt and manganese ions from aqueous media on nanofiber samples obtained from polyacrylonitrile (PAN) with subsequent directed modification by 1.25 M NaOH solution upon heating (70°C) (PAN*) are studied and optimized. Nanofibers were obtained by capillary-free electroforming from solutions of PAN in dimethylformamide. This method is advantageous for the simplicity of equipment, high energy efficiency of nanofiber production, versatility and flexibility in controlling process parameters and allows production of nanomaterials with desired properties. The values of the extraction degree (95.8 – 99.5%) and selectivity coefficients for competing pairs of metal ions are calculated: в_Pb/Cu = 1.2; в_Pb/Co = 2.8; в_Pb/Mn = 3.2;в_Cu/Co = 1.7; в_Cu/Mn = 3.7; в_Co/Mn = 2.5. A comparative analysis of the sorption activity of the obtained nanofibers revealed that the character of lead, copper, cobalt and manganese ion sorption by nanofibers is non-selective at pH 6 – 8 and selective for iron (III) ions at pH  3. A technique of sorption-atomic absorption determination of the aforementioned metal ions in real objects with preliminary nanofiber concentration at the level of tenths and hundredths of MPC is proposed. Non-woven materials based on modified PAN are used as effective extractants of nanogram quantities of HM ions. The detection limits for heavy metal ions are 40 – 80 ng/dm³.

An effective and easy to use method for estimating the molecular weight of starting oligomeric diols used for the synthesis of polyurethanes is developed. The prepolymers – linear oligomers with terminal isocyanate groups – are first synthesized as an intermediate product. To synthesize such prepolymers used in the free-casting manufacture of polyurethane and polyurethane urea compositions, oligodiol is reacted with an excess of diisocyanate, the ratio of NCO/OH groups being equal to or slightly higher than 2. This is very important for the second stage of synthesis when the prepolymer interacts with hardeners usually containing amine and hydroxyl groups. When the ratio NCO/OH  2 the resulting prepolymer contains a large amount of low molecular weight diisocyanate with a much higher activity compared to the repolymer. As a result, the potlife of polyurethane and polyurethane urea compositions can decrease to an nacceptable level. On the other hand, when the ratio NCO/OH < 2, the prepolymers with high molecular weight and relatively high viscosity can occur, which also complicates the processing of the aforementioned compositions. Maintaining the desired value of the ratio in the synthesis of prepolymers necessitates precise data on the molecular weight of the oligomeric diols used in the synthesis. Current methods for determining the molecular weight of oligomeric diols, based on the analysis of the content of hydroxyl groups have a number of disadvantages, namely the duration and complexity of the procedure and the high cost of the reagents. The developed method is based on conducting advanced syntheses of prepolymers with predetermined ratios between the initial oligomeric diols and diisocyanates. The equations linking the expected content of isocyanate groups in the prepolymer with the weight amounts of the starting components are derived. Testing of the method was carried out using ligoester and oligobutadiene isoprendiol as initial oligomeric diols.

Regulation of the process parameters allows obtaining the desired properties of the metal. Computer simulation of technological processes with allowance for structural and phase transformations of the metal forms the basis for the proper choice of those parameters. Methods of mathematical modeling are used to study the main diffusion and diffusion-free processes of transformations in alloyed steels during heating and cooling. A comparative analysis of the kinetic equations of phase transformations including the Kolmogorov – Avrami and Austin – Rickett equations which describe in different ways the time dependence of the diffusion transformation rate and attained degree of transformation has been carried out. It is shown that the Austin – Rickett equation is equivalent to the Kolmogorov – Avrami equation with a smooth decrease of the Avrami exponent during the transformation process. The advantages of the Kolmogorov – Avrami equation in modeling the kinetics of ferrite-pearlite and bainite transformations and validity of this equation for modeling the kinetics of martensite transformations during tempering are shown. The parameters for describing the tempering process of steel 35 at different temperatures are determined. The proposed model is compared with equations based on the Hollomon – Jaffe parameter. The diagrams of martensitic transformation of alloyed steels and disadvantages of the Koistinen – Marburger equation used to describe them are analyzed. The equations of the temperature dependence of the transformation degree, similar to the Kolmogorov – Avrami and Austin – Rickett equations, are derived. The equations contain the minimum set of the parameters that can be found from published data. An iterative algorithm for determining parameters of the equations is developed, providing the minimum standard deviation of the constructed dependence from the initial experimental data. The dependence of the accuracy of approximation on the temperature of the onset of transformation is presented. The complex character of the martensitic transformation development for some steels is revealed. The advantage of using equations of the Austin – Rickett type when constructing models from a limited amount of experimental data is shown. The results obtained make it possible to extend the approaches used in modeling diffusion processes of austenite decomposition to description of the processes of formation and decomposition of martensite in alloyed steels.

The main magnetic parameter sensitive to the structure of steel is the coercive force (H_c). However, the coercive force of steels with a carbon content more than 0.3% appeared unsuited for control of the tempering temperature (T_t), hardness (HRC), and mechanical properties of hardened products made of such steels due to non-monotonous character of H_c dependence on the tempering temperature after their quenching The goal of the study is to develop a method for control of the structural changes of medium-carbon steels that occur upon heat treatment proceeding from the information parameters generated using the coercive force H_c and the ratio K_S of their residual magnetization (M_r) to the magnetization of technical saturation (M_s) in a practically important temperature range. The advantage of the developed approach compared to those based on measuring the relaxation magnetic parameters of steels is that the parameters H_c and K_S can be measured using standard methods with the minimal relative errors of measurement (2 and 1%, respectively). We consider three different combinations of the parameters H_c and K_S – H₀, H_c1, and H_c2 — and analyzed their dependence on the tempering temperature and hardness of medium carbon steels C30 and C45. The parameters H₀, H_c1, and H_c2 monotonously change as the hardness of medium-carbon steels decreases. The correlation coefficient between the values of H₀, H_c1 and H_c2 and HRC £hardness of steel 30 in the range of 32  HRC  41 is 0.959, 0.965 and 0.978, respectively. The results obtained makes it possible to abandon the complex and inaccurate measurements of the relaxation magnetic parameters of steels when developing the methods and devices for magnetic structuroscopy, and focus on enhancing of the accuracy of measuring£ H_c and M_r/M_s ratio of the material.

Electrophoretic deposition is currently one of the most relevant technological methods for production of electrically conductive materials. In the work, the method of electrophoretic deposition obtained Electrically conductive materials based on carbon fibers (CF) have been obtained for the first time by electro-phoretic deposition using graphene oxide (GO) and silver nanoparticles. The obtained materials exhibit increased electrical conductivity, surface activity, and enhanced physical and mechanical properties. The purpose of the study is development of the methods for producing electrically conductive carbon textile materials by electrophoretic deposition of graphene oxide using galvanic deposition of silver nanoparticles from an electrolyte. Electrophoretic deposition was performed in 1 cm increments and at a constant voltage of 160 V during 20, 40, and 60 sec. Infrared spectroscopy data showed that GO particles are fixed on carbon textile materials. The carbon textile materials (CF/GO/NP Ag/60) thus obtained formed a new structure with several layers of graphene oxide and silver nanoparticles. The CF deposition increases the surface roughness of the hydrocarbon and thus improving the wettability and adhesion. An analysis of the spectra obtained by X-ray photoelectron spectroscopy for CF showed significant changes in the binding energy and the energy of excited photoelectrons. Compared with the initial hydrocarbons, the obtained carbon materials exhibited an increased content of silver and oxygen, whereas carbon to oxygen ratio decreased. The developed technique allowed us to obtain carbon textile materials with high electrical conductivity being 2.5 as much the original CF. Introduction of the silver nanoparticles contributes to filling of the surface cracks in CF. An increase in the share of reduced graphene oxide can significantly increase the surface roughness, electrical conductivity, surface energy and improve the screening properties of carbon textile materials. The effectiveness of screening in the obtained materials is 24.4 % higher than that in the initial CF which expands the potentiality of their application in novel technical textile products of the future.

The results of studying operational destruction of a high-loaded cardan shaft of the propeller engine made of steel 38KhN3MFA are presented to elucidate the cause of damage and develop a set of recommendations and measures aimed at elimination of adverse factors. Methods of scanning electron and optical microscopy, as well as X-ray spectral microanalysis are used to determine the mechanical properties, chemical composition, microstructure, and fracture pattern of cardan shaft fragments. It is shown that the mechanical properties and chemical composition of the material correspond to the requirements of the regulatory documentation, defects of metallurgical origin both in the shaft metal and in the fractures are absent. The microstructure of the studied shaft fragments is tempered martensite. Fractographic analysis revealed that the destruction of cardan shaft occurred by a static mechanism. The fracture surface is coated with corrosion products. The revealed cracks developed by the mechanism of corrosion cracking due to violation of the protective coating on the shaft. The results of the study showed that the destruction of the cardan shaft of a propeller engine made of steel 38Kh3MFA occurred due to formation and development of spiral cracks by the mechanism of stress corrosion cracking under loads below the yield point of steel. The reason for «neck» formation upon destruction of the shaft fragment is attributed to the yield point of steel attained during operation. Regular preventive inspections are recommended to assess the safety of the protective coating on the shaft surface to exclude formation and development of corrosion cracks.

The goal of the work is to study the effect of severe plastic deformation (SPD) on the impact toughness and fracture mechanism of St3sp low-carbon structural steel within a test temperature range of 293 – 213 K. The issues of deformation processing of steel St3sp billets using SPD method in conditions of the equal-channel angular pressing scheme (ECAP) are considered. The results of low-temperature tests by impact bending of Charpy steel samples in various states are presented. The impact toughness decreased by ~1.3 times as a result of ECAP in 16 passes. It is shown that the temperature dependence of the impact toughness of steel subjected to ECAP differs from that for steel in the delivery condition. A fractographic study of the fracture mechanisms of the steel in the initial state and after processing by ECAP at a test temperature of 293 – 213 K is carried out. It is shown that for the steel in the initial the transition from fracture with the formation of viscous and brittle fracture zones at 293 K to brittle at 213 K occurs through successive expansion of the brittle fracture area with decreasing temperature, whereas for hardened steel, the mixed fracture area appears in the local region at 233 K and expands to the entire cross section of the sample at 213 K. The microstructure formed as a result of ECAP in 16 passes in the temperature range up to 213 K prevents pure brittle fracture and leads to a mixed fracture pattern.

Heating and thermal cycling of carbon steel rope wire significantly affect the mechanical properties and durability of the entire rope under operating conditions. However, despite a large amount of studies aimed at determination of the reasons for destruction of the ropes of foundry cranes at metallurgical plants and development of measures for their elimination, accidents attributed to sudden rupture unfortunately occur. Therefore, the problem is still urgent and requires further research. Nowadays, new exhaust air suction systems for hot air streams mounted in converter shops of metallurgical enterprises reduce dangerously high temperatures to T = 240 – 300°C thus providing the possibility to avoid overheating of the ropes. However, the rope metal is exposed to a strong impact of blue brittleness – phenomenon, which causes reduction of the metal plasticity in this temperature range. We present the results of studying the impact of the heating temperature and number of cycles in thermocycling on changes in the characteristics of the mechanical properties of steel 70KK wire ropes in tensile tests. Tests of the wire samples are carried out at room temperature and after their exposure to high-intensity heating and thermal cycling at different temperatures and number of cycles. confirmed Presence of zones of blue brittleness is proved experimentally for the wire rope with a diameter of 1.65 mm in a temperature range of 200 – 240°C. It is shown, that the largest reduction in the relative narrowing (21%) and increase in the ultimate tensile stress by 4.8% occurred at a temperature of 240°C. This phenomenon should be taken into account when assessing the structural strength of steel. It is shown that there are reserves to increase the life cycle of ropes, taking into account the data on diagnostics of the mechanical and magnetic characteristics in industrial conditions.

The results of studying the tribological characteristics of thin coatings of steel parts on a modernized friction unit of a KT-2 machine in the boundary lubrication mode are presented. To provide high accuracy and reproducibility of the results standard elements of rolling bearings — balls and rollers, which are characterized by the uniformity of the structure and composition, as well as high quality of the surface treatment are used as samples. The developed design of the mandrel ensured friction contact of the ball mounted on the machine spindle with the ends of three rollers mounted with high accuracy at an angle of 35°30’ to spindle axis of the installation to ensure the same distribution of the axial load between three rollers like in the case of the four-ball contact between three lower balls. The coatings under study were applied to the flat ends of the rollers, which is much easier than their application to cylindrical or spherical surfaces. A standard ball made of steel ShKh-15 or wear-resistant ceramics served as a counterbody. The modernized unit is recommended to be used on traditional four-ball machines for laboratory assessment of the effect of thin wear-resistant coatings on the antifriction properties of lubricants.