The purpose. Investigation of the propensity of chromium steels to carbide formation during cementation and determination of the factors determining the increased propensity of chromium steels to carbide formation.

Methods. For the study, 12 melts of 0.5 kg of iron alloys with manganese, chromium and vanadium were melted in an induction furnace. The charge was technically pure iron and ferroalloys of these metals. Cementation was carried out in a wood-coal carburetor (grain size 1...3 mm) containing 30% of VaSО₃. Cementation mode: 920°C - 6 h, air cooling in an unpacked container.

Results. It is noted that the release of cementite in the granular form is facilitated by large positive deviations from the ideal in solid solutions of chromium in iron. The activity coefficient of chromium in Fe-Cr alloys is much higher than unity and is at 1000°C for alloys containing less than 10% Cr, 2.38. A large value of the chromium activity coefficient indicates a strong tendency for the separation of Fe-Cr solutions into two phases and the formation of chromium fluctuations, on which the nucleation of carbides is facilitated. Manganese stabilizes cementite so weakly that the latter, as in unalloyed austenite, cannot form in a granular form. Vanadium, in contrast to chromium and manganese, does not stabilize cementite, since it practically does not dissolve in it (the solubility of V in Fe₃C is only 0.4...0.5%, and forms a more stable carbide VC compared to chromium carbides. For this reason, Fe₃C is not formed in vanadium steel during carburization, and the total content of the carbide phase formed during carburization is determined by the content of carbide particles VC, which is determined by the content of vanadium in the steel.

Conclusion. The increased tendency of chromium steels to carbide formation during cementation is due to the stabilization of cementite with chromium. As a result of the dissolution of chromium, the value  ΔG₀ of cementite increases so much that it becomes energetically possible to form it in a granular form. The formation of cementite in granular form in chromium steels is also facilitated by a significant value of the coefficient of thermodynamic activity of chromium in austenite.

The purpose. A comparative analysis of the cost of electricity for a charge by the method of electroerosion dispersion for the production of hard alloy, and the comparison of physical and mechanical properties obtained EDM powder materials, and alloy of them.

Methods. To obtain experimental powder materials (charge), an installation for producing nanodisperse powders from conductive materials (patent RU 2449859), waste of a tungsten - free hard alloy of the KNT16 brand (GOST 2653085), working fluids carbon - (ethyl alcohol, GOST 26530-85) and oxygen-containing (distilled water GOST 6709-72) were used.

Using a scanning electron microscope "QUANTA 600 FEG", the morphology of an experimental electroerosive powder material of the KNT16 alloy was studied.

The elemental composition of the resulting powder material was studied by electroerosion of the KNT16 alloy using an energy-dispersion X-ray analyzer manufactured by EDAX.

The size distribution of microparticles of the experimental electroerosive powder material of the KNT16 alloy is determined.

Results. In the course of the study, it was found that: when dispersed in a carbon-containing working fluid, the energy costs are lower compared to the oxygen-containing one; the particles of the powder material obtained during the experiment have a predominantly spherical and elliptical shape; the main chemical elements of the charge obtained in ethyl alcohol are: Ti (66.1%); Ni (20.02 %); C (7.41 %); Mo (6.47 %); the average particle size of the powder material obtained by electroerosion was 18.69 microns.

Conclusion. The results obtained allow us to conclude that the dispersion by electroerosion of a tungsten-free hard alloy of the KNT16 brand in a carbon-containing working fluid of ethyl alcohol is less energy-consuming compared to the same process occurring in an oxygen-containing working medium of distilled water. According to the presented results of morphological studies, elemental and dimensional analysis, it can be concluded that the charge obtained during the experiment is suitable for obtaining sintered samples and their further study.

The purpose. The aim of the work is to develop recommendations for the optimization of the chemical composition of the steel to be produced, intended for the manufacture of welding wire Sv-08G2S, by the criterion of guaranteed production of a given value of the impact toughness of the metal deposited by the wire during arc welding in shielding gas.  

Methods. The equations reflecting statistically significant correlation in the sample of 22 low-alloy structural steels between the generalized relations of metallicity and covalency for the set of interatomic bonds in these steels with their impact viscosity are considered. It is proposed to use a regression dependence, linking the respect to the generalized degrees of metallicness and covalently for the totality of interatomic bonds in the metal of welding wires with impact toughness of metal weld in arc welding in the protective gas data wires. 

Results. The relative influence of molar fractions of chemical elements (within the limits of possible variation of their mass content in the welding wire Sv-08G2S, regulated by GOST 2246) at different temperatures on the toughness of the metal deposited in carbon dioxide by the wire Sv-08G2S. It is shown that the set value of the impact toughness of the deposited metal can be provided at different content of alloying elements and impurities in the welding wire Sv08G2S, but the ratio of the generalized degrees of metallicity and covalency for the set of interatomic bonds in the metal wire remains unchanged. It is shown that when smelting steel intended for the production of welding wire Sv08G2S, to ensure the guaranteed required value of the impact strength of the metal deposited by the welding wire, it is required by varying the chemical composition (within the limits determined by GOST 2246) to provide in various smelters the specified value of the ratio of the generalized degrees of metallicity and covalency for the set of interatomic bonds in the smelted steel. 

Conclusion. The algorithm reflecting the developed recommendations on optimization of chemical composition of welding wire Sv-08G2S at its smelting by criterion of providing the set shock viscosity of the metal deposited by this wire at arc welding in shielding gas is developed.

The purpose of this work was to study the influence of silica additive on transformability (at concentrated loads) of the tetragonal phase of zirconia stabilized with calcium oxide, toughened by aluminum oxide.

Methods. To study of phase transformations in the area of local deformation, a five-cycle indentation method with an increasing load was used. The effectiveness of tetragonal-monoclinic transformations was judged by the quantitative evaluation of the ratios of hysteresis loss energy to plastic deformation energy δ calculated from P-h diagrams.

Results. It has been found that increase of SiO₂ impurity concentration from 0 to 5 mol.% in zirconia (stabilized by CaO and containing 5 wt.% Al₂O₃) causes an increase in the values of δ, that is, an increase in hysteresis losses recorded when the indenter is repenetration into the formed imprint. The reason of observed hysteresis losses are tetragonalmonoclinic transformations t-ZrO₂ → m-ZrO₂. Therefore, the introduction of SiO₂ impurity contributes to improving the transformability of zirconia tetragonal phase. The reason for this may be the interaction of SiO₂ and CaO with the formation of calcium silicates and, as a result, imbalance in the concentrations of ZrO₂ and its stabilizer CaO. Conclusion. Increasing the transformability of the t-ZrO₂ tetragonal phase with the introduction of SiO₂ impurity enhances the role of transformation toughening in zirconia reinforced with Al₂O₃ particles, which provides a significant increase (by more than 70 %) of its fracture toughness. However, exceeding the critical value of SiO₂ impurity concentration causes spontaneous (in the absence of mechanical loads) t-ZrO₂ → m-ZrO₂ transformation, which abruptly reduce the role of the transformation toughening and worsens the strength properties of the studied ceramics.

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.

The purpose of the work is to study in external gradient magnetic fields the regularities of magnetophoresis processes in magnetic fluids in thin optically transparent layers and their relationship with the structuring and parameters of the magnetic fluid system.  

Metods. To study the influence of the structure and parameters of a magnetic fluid on the dynamics of the magnetophoresis process, a set of experimental installations was created for the long-term effect of inhomogeneous magnetic fields of various configurations. As the images, the images of magnetic fluid with different dispersed composition were studied, including non-centrifuged ones containing large magnetic particles.

Results. In magnetic fluid samples with different dispersed composition, the phenomenon of magnetophoresis in a thin layer in inhomogeneous magnets of various configurations, created by an annular permanent magnet, as well as an axial magnetic system based on unipolar magnets, has been investigated. Based on the phenomenological equations of magnetophoresis and Brownian diffusion, a theoretical interpretation of the dynamics of the magnetophoresis process in magnetic fluid systems in an inhomogeneous magnetic field is proposed.

Conclusion. It was found that for a sample containing larger magnetic nanoparticles, the magnetophoresis process proceeds 5 times faster. Methods and installations for the study of magnetophoresis in magnetic fluids in inhomogeneous magnetic fields of various configurations have been developed, which are applicable to assess the size of magnetic particles and the stability of magnetic fluids, to study the processes of separation and structure formation in them under prolonged exposure to high-gradient magnetic fields. 

Purpose. To investigate the complex spectra of bending oscillations (Lamb waves) with exponential temporal decay of the driving force amplitude for a rectangular plate with simply supported boundary conditions.

Methods. Complex spectral analysis of nonlinear interactions of optical, magnetic and acoustic waves in limited samples.

Results. Acoustic methods for examination of material structure and properties are now well investigated. By the analysis of Lamb waves propagation and scattering in various structures we may assume the presence of heterogeneities (layers, defects, etc.). But in some cases, such methods are not effective enough due to the complexity of the results interpretation – for example, resonance curves of several waves with different attenuations can’t be isolated. In the present study the complex frequency spectrum analysis was carried out for two vibration modes with equal frequencies and different attenuation factors. Scanning not only the real, but also the imaginary part of the amplitude-frequency spectrum allows one to determine the oscillation’s mode composition with a higher level of precision. The effect of complex resonance was previously considered for optical media, but the similarity between acoustic and electromagnetic wave equations allowed us to extend the complex spectroscopy principle to acoustics.

Conclusion. We suppose that application of complex spectral analysis of generated and recorded waves would significantly expand the potential of resonant acoustic methods. The complex spectrum allows one to distinguish normal modes with identical frequencies and different attenuation coefficients, besides the range of resonant curve along the axis of real frequency is bigger than one along the imaginary axis. This method can be applied to the investigation of non-linear interaction of magnetic, electro-magnetic and acoustic waves in limited medium. The complex spectral analysis can also be used for non-destructive testing and in seismology.  

Purpose. The aim of the work is to study the dynamics of non-magnetic gas bubbles and droplets in a magnetic liquid in an inhomogeneous magnetic field

Methods. The experiments were carried out on installations developed on the basis of known methods and equipment for magnetic measurements and manufactured independently). Modern digital high-speed video recording systems with high resolution are used as measuring systems. Samples of magnetite magnetic fluid, oleic acid as a surfactant, and kerosene as a carrier fluid are studied.

Results. Two options for studying a levitating nonmagnetic volume in a magnetic fluid are experimentally considered: with contactless manipulation in a measuring cell with a magnetic fluid using an inhomogeneous magnetic field created by an annular permanent magnet, as a result of which nonmagnetic drops or gas bubbles separated from it and floated up, as well as during injection non-magnetic phase with a syringe pump through a capillary, the end of which was located in the "magnetic vacuum region" of a non-uniform magnetic field.

Conclusion. Within the framework of the theoretical interpretation, it is shown that the configuration of the inhomogeneous magnetic field and the properties of the magnetofluid system play a decisive role in the formation of a levitating nonmagnetic volume. It has been experimentally demonstrated that the sizes of non-magnetic inclusions floating up in a magnetic-fluid system in an inhomogeneous magnetic field do not depend on the flow rate and hydrostatic pressure, while it is possible to control the size of non-magnetic liquid and gaseous inclusions by changing the parameters of magnetic fluids and the magnetic field, which can be used in as micro-batchers or gas meters in microfluidic systems.

The purpose of this work was to study the process of adsorption of direct light-resistant dyes from aqueous solutions by cellulose raw materials.

Methods. Waste of the woodworking industry was used as a sorbent - sawdust of deciduous trees with a particle size of 3.25 to 4.25 mm. Three direct lightfast dyes were selected by preliminary tests as adsorbates: turquoise SV, blue KU, red 2C.

To determine the maximum light absorption of the direct light-resistant dyes studied in this work, the absorption spectra were taken over the entire wavelength range.

To determine the residual concentration, calibration graphs of the dependence of the optical density on the concentration of the corresponding dyes (turquoise CB, blue KU, red 2C) were built. The paper presents the linearized equations of the calibration graphs obtained using the least squares method and the approximation reliability values, the values of which show the degree of compliance of the trend model with the initial data.

Results. The maximum light absorption was determined: for the dye direct turquoise CB - 611 nm, for the blue KU - 563 nm, for the red 2C - 523 nm.

The optimal conditions for the adsorption of direct light-fast dyes by cellulose raw materials have been established and the parameters characterizing the adsorption of direct light-fast dyes (turquoise CB, blue KU, red 2C) by cellulose raw materials from aqueous solutions at different mass values have been determined.

Analysis of the kinetic curves of sorption suggests that under the indicated optimal conditions, the highest degree of sorption (more than 99%) by cellulose raw materials from aqueous solutions is achieved in 30 minutes for the direct lightfast dye blue KU.

Conclusion. The results obtained will show that 2C direct red dye is sorbed 2 times less than other dyes used in this work. The dye direct blue KU reached the highest degree of sorption with the lowest mass of cellulose raw material of 3.0 g.

Purpose. To study condensation reactions as a method for obtaining compounds of the acridine series and to investigate their reactivity.

Methods. We used the techniques and methods of organic chemistry in the synthesis of new derivatives of the acridine series. The purity of the products was controlled using the chromatographic method of analysis, and the structure was confirmed by a set of spectral methods of analysis on the instrument base of the Department of Fundamental Chemistry and Chemical Technology of the South-Western State University.

Results. N-acridoneacetic acid was isolated by cyclization of N, N-diphenylglycine-2-carboxylic acid while boiling in concentrated sulfuric acid. The cyclization of N,N-diphenylglycine-2-carboxylic acid, subject to the use of phosphorus chloroxide and phosphorus trichloride as a cyclizing agent, which is widely used in organic synthesis to obtain substituted 9-chloroacridine, bypassing the step of obtaining acridone-9, led to nucleophilic substitution of hydroxy residues on halogen with the release of 2[(2-chloro-2-oxoethyl)phenylamino] benzoyl chloride. It was found that the closure of the cycle to the corresponding 2-(9-chloroacridin-10 (9H)-yl) acetyl chloride does not proceed. 2- (9-Oxoacridin-10-yl) acetyl chloride was obtained in high yield by refluxing 2-(9-oxoacridin-10-yl)acetic acid in thionyl chloride in the absence of solvent. Substitution of the oxo group for halogen under the experimental conditions does not occur due to the structure of the starting acridine. Substitution of hydrazine for the chlorine atom in the acid chloride by refluxing it with 84% hydrazine hydrate led to 2-(9-oxoacridin-10-yl)acetohydrazide in high yield. The structure of the compounds was proved using spectral methods of analysis.

Conclusion. 2-(9-Oxoacridin-10-yl)acetyl chloride was synthesized by the reaction of thionyl chloride with  2-(9-oxoacridin-10-yl)acetic acid, on the basis of which a promising laboratory method for the preparation of  2-(9-oxoacridin-10-yl)acetohydrazide.