The purpose. Investigation of the effect of heat treatment on the mechanical properties of low-carbon and low-alloy reinforcing steels.

Methods. Three batches of samples of reinforcing steels of the following grades were selected as objects of research: low-carbon steel St5, low-alloy steel 25G2S and 30XG2S. The first batch of samples with a length of 250 mm was subjected to furnace heating (muffle furnace), quenching and furnace tempering at various temperatures. The second batch of samples – rods with a length of 1300 mm were subjected to furnace heating (tube furnace), and then quenched and cut into samples with a length of 250 mm. One part of the samples was subjected to furnace tempering, the otherto electric start-up. The third batch of samples was made from rods with a length of 2000 mm. After furnace heating (tube furnace), they were quenched and electro-fired, and then cut into samples with a length of 250 mm. After furnace heating, samples with a length of 250 mm were quenched in water from temperatures of 850, 880, 900, 910, 930 and 950°С.

Results. Mechanical tests were carried out. The regularities of changes in the characteristics of mechanical properties are revealed: time resistance, yield strength, true elongation stress of the initial working length. It is established that the optimal tempering temperature of the reinforcing bar for all tested steels is 900 ±20°С.  It is shown that the electric start-up provides better mechanical properties, in comparison with furnace tempering in the temperature range of 250400°С. It is revealed that the 30XG2S, 25G2S and St5 rod fittings, strengthened by drawing during heat treatment, as well as high-strength steel wire can be subjected to electric heating at 400 ℃ without significant influence on the strength of the steel.

Conclusion. The results obtained can be used to determine the behavior patterns of different types of ingot, powder, and composite materials with high dispersion in the phase and structural components under different conditions and states.

Purpose. Optimization of the process of obtaining an electroerosive charge of BrS30 bronze for the production of sintered bronze alloys based on it.

Methods. To obtain experimental powder materials (charge), an installation was used to obtain nanodispersed powders from conductive materials, waste of lead bronze alloy BrS30 in the form of shavings (GOST 493-79), working liquids carbon- (lighting kerosene, GOST 11128 -65) and oxygen-containing (distilled water GOST 6709-72). Dimensional analysis of electroerosive materials obtained from BrS30 lead bronze wastes was carried out on an Analysette 22 NanoTec laser particle size analyzer. The determination of the optimal operating parameters of the EED unit was carried out by setting up a full factorial experiment (FFE) on the average particle size of the resulting electroerosive materials.

Results. In the course of the calculations, the limiting values of the optimization parameter (average size of electroerosive particles) were determined, which amounted to: for water ‒ 44.19 microns with a capacity of 65.5 microfarad discharge capacitors, a voltage on the electrodes of 200 V, a pulse repetition rate of 200 Hz; for kerosene ‒ 53.88 microns with a capacity of the discharge capacitors of 65.5 microfarads, a voltage on the electrodes of 200 V, a pulse repetition rate of 200 Hz.

Conclusion. Based on the presented research results and calculations. it can be concluded that the average particle size obtained in lighting kerosene is 1.2 times higher than the average particle size obtained in distilled water, and is 44.19 μm and 53.88 μm, respectively, which is associated with large energy losses electric discharge on the breakdown of the working fluid due to the difference in the dielectric constant of water and kerosene.

The purpose. To develop and research a new technology for restoring and strengthening worn machine parts with composite electroplating coatings using micro - and nanofractionated tungsten-containing electroerosive powders as the strengthening phase.

Methods. When setting up the experiments, a sample was used – a metal circle with a thickness of 5 mm and a diameter of 50 mm. The area of the side on which the coating was applied is 0.1963 . The composition of the electrolyte used in the experiments: iron sulfate 450 g / l; sodium chloride 250 g/l; temperature 100℃; current density 20 A/ ; current output 90-98%.

Transformer steel plates were used as anodes. The plates have an easy-to-use shape, are accessible, and have a chemical composition close to pure iron. Hard-alloy powders of micro-and nanofractions were obtained on an electrodispersion unit (Patent for invention of the Russian Federation No. 2449859) from the waste of the T30K4 alloy in water.

Results. When setting up the experiments, a coating was applied using a standard composition, and then a coating with the addition of an electroerosive powder obtained from a T30K4 hard alloy in an amount of 5 g/l of the solution. The structure and properties of the resulting composite electroplating coatings were investigated as a result of the research aimed at improving the technology of restoring automotive parts by the method of ironizing by introducing a strengthening additive based on electroerosive materials into the electrolyte. The results obtained in the course of the work make it possible to obtain composite electroplating coatings based on sulfuric acid electrolytes with the addition of a powder material obtained by the EED method from the T30K4 alloy.

Conclusion. The study of composite electroplating is an important and relevant topic. This type of coating has many advantages over the classic, single-component coatings. The introduction of special additives in the electrolyte makes it possible to increase the strength of coatings, their resistance to high temperatures, increases their resistance to longterm operation in conditions of oil starvation, some types of composite electroplating coatings can also give the surface dirt-repellent properties.

The purpose. The aim of the work is to study the effect of heat treatment on the mechanical properties of three-layer bimetallic materials obtained by continuous casting and their components.

Methods. In this work, we determined the mechanical properties of three-layer wear-resistant bimetallic materials steel 60 + steel 15 + steel 60; steel 60 + steel 10 + steel 60; U9 + steel 10 + U9; ShKh15 + steel 10 + ShKh15 obtained by continuous casting in LLC "Tulachermet-steel", and their components after various types of heat treatment (quenching, quenching + tempering). The casting of bimetals was carried out using two crystallizers located one above the other in a vertical plane. The upper mold is designed to form the main layer, the lower – the cladding layer. Next, the bimetal was rolled according to the following scheme: the first 2...4 passes-along the axis of the slab, then up to 10...11 passesacross (splitting the width) and then again along until the end of the rolling. After rolling, the strips were straightened on the correct machine, and the end and side edges were cut. As a result, sheets of 7×1465×4037...4471 mm were obtained. To determine the mechanical characteristics, tensile tests were performed according to GOST 1497-84 "Metals. Methods of tensile testing" of samples for mechanical tests on the R-5 breaking machine.

Results. Mechanical tests were carried out. The regularities of changes in the characteristics of mechanical properties are revealed: time resistance, yield strength, relative elongation of the initial working length, relative narrowing. It is shown that the strength characteristics of the studied wear-resistant bimetals after rolling on a 7 mm thick cast and subsequent heat treatment can be arranged in the following sequence: U9 + steel 10 + U9, steel 60 + steel 15 + steel 60, steel 60 + steel 10 + steel 60, ShKh15 + steel 10 + ShKh15. The low properties of bimetal ShKh15 + steel 10 + ShKh15 are probably associated with an underestimated chromium content – 0.48%.

Conclusion. The results obtained can be used to determine the behavior patterns of different types of ingot, powder, and composite materials with high dispersion in the phase and structural components under different conditions and states.

Purpose of research. Form a film structure from stabilized CdSe/CdS/ZnS quantum dots by the Langmuir – Blodgett method and comprehensively characterize it using modern nanoinstrumental methods.

Methods. Determination of surface morphology by atomic force microscopy; chemical structure by Raman scattering of light; the size of CdSe/CdS/ZnS quantum dots, including by the method of small-angle X-ray scattering.

Results. A family of compression isotherms of Langmuir monolayers is obtained on a colloidal system of CdSe / CdS / ZnS quantum dots stabilized by trioctylphosphine and its oxide. From the analysis of isotherms, rational parameters of the formation of a Langmuir film and its transfer to a solid substrate have been established. It is found that the control parameters of the formation of quantum dots in a Langmuir film are the temperature of the water subphase and the surface concentration of quantum dots. The decisive role in the deposition of the film is assigned to the speed of the dipper movement.

Atomic force microscopy revealed its regularity in the film structure, and determined the lateral size of the aggregates of stabilized quantum dots (about 50 nm). Longitudinal optical phonon modes characteristic of CdSe/CdS/ZnS have been detected by the method of Raman light scattering.

A theoretical calculation of the position of Langmuir barriers is carried out when a monolayer structure with a hexagonal close packing of quantum dots is formed between them.

Conclusion. The Langmuir – Blodgett method, which allows the formation of quantum dots into film structures, acts as an alternative, for example, to eleonic methods, differing in automation, repeatability and unpretentiousness to environmental conditions. Using the method of atomic force microscopy, it is possible to establish a rational regime for the formation of Langmuir films with their subsequent complex characterization.

Purpose of the study. Investigation of the antioxidant properties of ablated cerium dioxide nanoparticles under conditions of oxidative degradation of the organic dye methylene blue during the Fenton reaction, depending on their size and structural-phase characteristics.

Methods. Characterization of ablated cerium dioxide nanoparticles using transmission electron microscopy equipped with an energy Ω-filter and a scanning HAADF detector; examination in the visible and ultraviolet range of the absorption spectra of samples using an optical spectrophotometer; study of the antioxidant activity of ablated nanoparticles in the Fenton oxidative reaction using the example of the organic dye methylene blue depending on the content and size composition of cerium dioxide nanoparticles.

Results. Cerium dioxide nanoparticles with pronounced antioxidant properties have been obtained by laser ablation. With an increase in the content of CeO₂ nanoparticles, the antioxidant properties of a colloidal solution based on them increase. The dependences of the antioxidant activity of cerium dioxide nanoparticles on their dimensional and structural characteristics have been determined.

Conclusion. A new method for obtaining nanodispersed particles of cerium oxide enriched with functional structural defects is proposed. Cerium dioxide nanoparticles, ablated by pulsed laser radiation, are new nanomaterials that are antioxidants capable of inactivating reactive oxygen species in oxidative processes such as the Fenton reaction.

Purpose. The dynamics of the rotation of liquid masses, the study of the equilibrium shapes of rotating liquids and  their nonequilibrium states have traditionally attracted the researchers’ attention. The key problem of this work is  the experimental study of the rotational effect in magnetic fluids. A macroscopic capsule filled with magnetic fluid acquires a rotational moment because of spatial orientation of magnetite nanoparticles under the action of an external rotating magnetic field. The magnitude of this effect depends on many parameters. We discuss how it depends on the frequency and amplitude of the external rotating magnetic field, as well as on the concentration and viscosity of the magnetic fluid.

Methods. Our research object is magnetic fluids APG 942 and APG 2135, produced at the Ferrotec Corporation (Japan), and their derivants obtained by mixing with dodecane and durazin. Magnetic nanoparticles are from magnetite, dispersion medium is synthetic hydrocarbon oil.

The experimental data were obtained using a torsion pendulum in a rotating magnetic field. A spherical capsule was filled with the samples and suspended on a thin elastic thread. A webcam placed under the capsule registered the angle of its rotation relative to the equilibrium position. Taking into account the elastic coefficient of the thread, we plotted the dependences of the rotational moment of the sample on the parameters of the external rotating magnetic field.

Results. The result of our experimental research is the dependences of the rotational effect in a magnetic fluid on the amplitude and frequency of the external magnetic field. The influence of the concentration, magnetic characteristics and viscosity of magnetic fluid samples on the rotational effect is also discussed. We suggest the aggregation model of the rotational effect, which describes the experimental data from the point of view of the formation and destruction of aggregates and clusters of magnetic nanoparticles.

Conclusion. The research results allow analyzing the structure of magnetic dispersed systems. It can be used in the development of devices based on the action of alternating magnetic fields on a magnetic fluid.

Purpose of research. Complex characterization of the degradation of magnetron Zr nanofilms upon atmospheric annealing at temperatures up to T_an = 973 K, satisfying the condition T_D < T_an < T_m (above the Debye temperature T_D, but below the melting temperature T_m) and a qualitative description of the clustering processes of both metallic zirconium and its oxides.

Methods. Magnetron sputtering of a Zr target in a constant current mode (power 300 W, sputtering time 300 s, working gas Ar, flow rate0.7 L / h). Magnetron nanofilms were deposited in an MVU TM - "Magna T" installation on silicon substrates (with IR heating - up to 403 K, ion cleaning - 60 mA for 120 s). The characterization of magnetron nanofilms was carried out by the methods: X-ray phase analysis and annealing (T_an) in air in an Anton Paarthermocell (with a step of 100 K to 973 K), atomic force microscopy, and Raman scattering of light. The fractal dimension (D) of MN was determined by the Hausdorff-Besicovich method.

Results. The particle size distribution of nanoclusters in Zr films at all temperatures T_an was Gaussian. The dimensions of the coherence region (L) and the relative changes in microstrains (ε) are calculated from the diffractograms. The chemical structural changes during the annealing of zirconium nanofilms have been studied both by XRD and Raman scattering. The temperatures of phase structural transitions and associated chemical transformations were determined from AFM images of the MN surface.

Conclusion. Degradation changes recorded during the complex use of nanoinstrumental methods in the analysis of MN (in particular, from Zr) both in the initial state immediately after MR and after annealing in an atmosphere with annealing temperatures up to Tan = 973 K (T_D < T_an <T_m) , have shown the practical significance of the obtained quantitative parameters such as the size of crystallites, microstrains, texture, fractal dimension and roughness of their surface.

Purpose. The article is devoted to the description of adsorption isotherms of perrhenate ions by ash and slag waste from thermal power plants from the standpoint of the Langmuir and Freundlich models. 

Methods. Sorption was carried out on model solutions in the range of analyte concentrations from 0.10 to 0.40 mg / ml at pH = 2 and pH = 7 under static conditions. The contact time of the phases was 60 min. The content of rhenium (VII) in solutions before and after sorption was monitored photometrically. The values of the constants were determined graphically from linearized adsorption isotherms. 

Results. The shape of the linearized adsorption isotherms indicates the applicability of both models for describing the equilibrium adsorption processes of perrhenate ions. The correlation coefficients calculated by the least squares method for the two adsorption models are comparable with each other. However, the closest closeness to unity of the correlation coefficient is achieved for the Langmuir model (at pH = 7: R² = 0.9748 for the Langmuir model, R² = 0.9275 for the Freundlich model; at pH = 2: R² = 0.9846 for the Langmuir model and R² = 0.9659 for the Freundlich model), which confirms the formation of a monomolecular layer on the surface of the adsorbent. The limiting adsorption capacity of ash and slag waste from thermal power plants in relation to perrhenate ion was 6.211 mg / g at pH = 7 and 5.988 mg / g at pH = 2. 

Conclusion. The results obtained give reason to believe that the adsorption of perrhenate ions by ash and slag wastes from the thermal power plant is complex. At the initial stage, sorption is a physical process; in the region of medium and low analyte concentrations, chemisorption is possible. The adsorption models derived from the analysis of the Langmuir and Freundlich isotherms adequately describe the adsorption equilibria.

Purpose. Study the inhibitory effect of some industrial dyes in the acid corrosion of steel.

Methods. Industrial dyes of different classes were used as acid corrosion inhibitors: acid violet, active red 5CX, direct diazobordo C, cationic blue, dispersed yellow 4C, single-chromium olive Zh. The value of the inhibitory effect of the dye was determined by the weight method. To determine the possibility of interaction of iron (III) ions with the dye, a spectrophotometric method was used.

Results. All the dyes had a protective effect. Probably, the organic dye film isolates the metal from the corrosive environment, and also changes the structure of the double electric layer at the metal / solution interface. This leads to a slowdown in both chemical and electrochemical corrosion. It was found that dyes with a low inhibitory effect react with iron ions formed during corrosion to form new compounds, which was confirmed by spectrophotometry.

Conclusion. For the first time, such dyes as acid violet, active red 5CX, direct diazobordo C, cationic blue, dispersed yellow 4C, and single-chromium olive W were studied as inhibitors, and their inhibitory effect was compared with the structure of the dye. It was found that the dyes have an inhibitory effect on the acid corrosion of steel, even when added in small quantities. The dyes with the nitrogen atom combined with hydrocarbon radicals have the greatest protective effect, and the least protective effect is that of the azo group, which is confirmed by the absorption spectra of the dyes and their mixtures with iron ions. When the acid concentration increases, it reduces the protective effect of the dye. Over time, the protective effect changes ambiguously. In the acid violet dye, it decreases by 29.5% -37.8%, and in the direct diazobordo dye with an inhibitory effect, on the contrary, it increases by 1.5-2 times over time.