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The structural-phase sates and defect substructure are studied by the method of transmission electron microscopy using diffraction at different distances from the wheel–rail contact surface along the central axis of symmetry of the top of rail (TOR) (rolling surface) and along the radius of rounding (fluting) of the differentially hardened rails of the DH400RK category made of hypereutectoid steel after their continuous service. Using the obtained structure parameters, the estimates are made of the hardening mechanisms (strengthening by pearlite component, incoherent cementite particles, grain- and subgrain boundaries, dislocation substructure and internal stress fields) controlling the yield stress in the steel under study. A comparison is performed of the quantitative fine structure parameters and the contributions into hardening on the rolling surface and fluting. It is found out that the prevailing morphological component near the wheel– rail contact surface is the subgrain structure, and in the fluting – strengthening by incoherent particles. [ABSTRACT FROM AUTHOR]

Abstract—For rails of increased wear resistance and contact endurance of the DH400RK category made of E–0.9C–Cr–V–Fe hypereutectoid steel, after a tonnage of 187 million tons, the fine structure in the railhead along the central axis at distances of 0, 2, and 10 mm was analyzed using transmission electron microscopy for the four morphological components of pearlite from the rolling surface. The nonmonotonic change in scalar and excess dislocation density, fragment size, cementite particles, and internal long-range stress fields in the railhead section was analyzed. [ABSTRACT FROM AUTHOR]

The study revealed no effects of pregnancy and childbirth on the course of tuberculosis in female BALB/c mice after aerosol infection with Mycobacterium tuberculosis. However, we demonstrated a negative effect of tuberculosis infection on the fertility of infected females, which manifested in a longer period from mating to pregnancy and in a smaller litter size. Impaired reproductive function in response to the effect of the systemic infectious process was accompanied by the development of immunosuppression confirmed by an immunological test (delayed-type hypersensitivity to tuberculin) and the formation of genital tract dysbiosis during pregnancy and postpartum period. [ABSTRACT FROM AUTHOR]

The structural and phase state of the surface layers of technically pure titanium (VT1-0 alloy) implanted with aluminum ions in three states (submicrocrystalline, ultrafine-grained, and fine-grained) obtained by multiple uniaxial pressing (abc pressing) followed by multipass rolling in groove rolls at room temperature and subsequent annealing at 573, 673, and 773 K for 1 h, respectively, has been studied by transmission electron microscopy and energy dispersive X-ray spectroscopy on foils cut perpendicular to the machined sample surface. Ion implantation has been performed for 8 h and 20 min at an irradiation dose of 10 × 1017 ions/cm2 and a temperature of 623 K. It has been found that the implantation led to the formation of a gradient structure consisting of five layers. For each layer, the thickness, phase composition, and shape and arrangement of second-phase particles have been determined and the α-Ti grain size and the size, distribution density, and volume fractions of separated particles have been measured. It has been established that the implantation causes the formation of Ti3Al and TiAl3 intermetallic phases. Ti3Al particles have a lamellar shape and are located inside parts of α-Ti grains, while TiAl3 particles have a rounded shape and are arranged randomly. [ABSTRACT FROM AUTHOR]

The fine structure of a submicrocrystalline (SMC) VT1-0 alloy is studied after its implantation with aluminum ions at the irradiation doses of 1·1017, 5·1017, and 10·1017 ion/cm2. A gradient structure is observed to form in the alloy in this state, which consists of five different layers: 1 – oxide layer, 2 – ion-doped layer, 3 – layer with refined grain structure, 4 – layer of residual implantation influence, 5 – layer with initial grain structure. It is shown that at all of the implantation doses used in the study there is no dislocation structure in layers 2 and 3, and the dislocations in layers 4 and 5 form a network substructure. The internal stresses in layers 2 and 3 represent an elastic component of long-range stresses, in layer 4 – long-range and shear stresses, and in layer 5 – shear stresses only. [ABSTRACT FROM AUTHOR]

The internal structure of grains, as well as the amplitude of internal stresses and their sources, in ultrafine grained technically pure nickel obtained by equal-channel angular pressing deformation was studied by the method of transmission electron microscopy. Under equal-channel angular pressing, the samples have been subjected to shear deformation by compression along two intersecting channels of equal diameter at an angle of 120° and temperature T = 400°C without intermediate annealing. Number of passes n = 4. The equal-channel angular pressing is found to lead to the formation of particles of secondary phases in ultrafine grained nickel with nanometer size and localized inside, at the boundaries and the joints of grains. The sources of internal stresses are revealed and their amplitude is determined. Determination of the amplitude of internal stresses is based on the determination of the curvature–torsion of the crystal lattice along bending extinction contours. It has been established that the sources of internal stresses are grain joints in which particles of secondary phases are present or absent; grain boundaries at which particles of secondary phases are present or absent; particles located on dislocations inside grains, and, finally, the dislocation structure in grains or parts of grains in which there are no particles of secondary phases. It has been found that internal stresses from all sources involve all grains regardless of their internal structure and are predominantly elastic in nature. This means that equal-channel angular pressing led mainly to the elastic distortion of nickel lattice. [ABSTRACT FROM AUTHOR]

The level of microscopic internal long-range stress fields σlr on the tread surface and working fillet has been determined for two rails with a carbon content of 0.74 and 0.91 wt % of categories DT350 (of general purpose) and DT400IK (with increased wear resistance and contact endurance) after a passed tonnage of 1770 million t (for DT350), and 187 million t (for DT400IK) (1) and 234 million t (for DT400IK) (2). For this purpose, the bending extinction contours are analyzed by means of transmission electron diffraction microscopy, the parameters of which are used in calculating σi. The presence of excess extinction contours indicates the bending–torsion of the lattice, which is characterized by an excess density of dislocations. A comparison is made with other methods for measuring internal stress fields at the meso and macro levels (optical and magnetic methods, X-ray diffraction analysis), which are integral. It is shown that the parameters of the bending extinction contours are the most informative and allow one to control locality of the σlr measurement. Sources of internal stress fields in rail steels are noted. An increase in the level of σlr in D400IK rails in comparison with rails of the DT350 category has been revealed. The growth in the passed tonnage for rails of the DT400IK category leads to an increase in σlr, while the values of internal stresses on the fillet surface exceed the corresponding values on the tread surface. The physical reasons for the observed changes are discussed. [ABSTRACT FROM AUTHOR]

In this paper, we study the structural-phase state of the surface layers of commercially pure titanium (VT1-0 alloy) implanted with aluminum ions by transmission electron microscopy and energy-dispersive X-ray spectroscopy. The samples are foils cut perpendicular to the treated surface. The samples are studied in three states (submicrocrystalline, ultrafine-grained, and fine-grained) obtained after a combined method of multiple uniaxial pressing (abc pressing) followed by multi-pass rolling in grooved rolls at room temperature and subsequent annealing at 573, 673, and 773 K, respectively, for 1 h. Ion implantation is carried out for 8 h 20 min at an irradiation dose of 1018 ions/cm2 and 623 K. It is established that implantation led to the formation of a gradient structure consisting of five layers: (1) oxide layer, (2) ion-implanted layer, (3) layer with a crushed grain structure, (4) layer formed under the residual influence of implantation, and (5) layer corresponding to the nonimplanted state of the alloy. The structural-phase state of layers 1–3, where the concentration of implanted aluminum was maximum, is studied. For each layer, its thickness, phase composition, shape and arrangement of particles of the phases formed by the action of ion implantation are determined, and the sizes of α-Ti grains, sizes, distribution density, and volume fractions of precipitated particles are measured. It is established that the basis of layer 1 is aluminum and titanium oxides. The matrix of layer 2 is an α-Ti solid solution supersaturated with Al atoms, and that of layer 3 is a solid solution based on α-Ti. Aluminum implantation is found to lead to the formation of the intermetallic phases Ti3Al and TiAl3. The particles of these phases are present as separately located nanograins in layer 1, Ti3Al particles have a lamellar shape and are located inside α-Ti grains in layers 2 and 3, and TiAl3 particles have a rounded shape and are found both in the bulk and at the grain boundaries of α-Ti. The volume fractions of intermetallic phases in layer 3 are maximum. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the current-voltage characteristics and optical emission spectra of an atmospheric pressure pulsed discharge plasma at a frequency of several tens of kilohertz and a pulse duration of up to 10 μs in the mode of generation of plasma flows containing metal particles. The peculiarity of the plasma generator consists in a combination of the electrode design and the modes of the electric and gas supply to the discharge system. This combination allows a low-current (from 40 mA to 1 A) operation at a sufficiently high voltage of 150 to 200 V, without a transition to the arc discharge mode. These parameters make it possible to generate atomic flows from the melting cathode insert, which are blown out by a jet of working argon gas pumped at a flow rate of 1 l/min beyond the discharge system. The entry of a metal component into the gas-discharge plasma affects the discharge operation parameters and the properties of its optical emission. In the context of this phenomenon, the spectral distributions of the intensity of optical radiation corresponding to the lines of magnesium, indium, and zinc and their time dependence are investigated during the current pulse period as applied to identification of the physical features leading to a stable generation of metal atom flows at atmospheric pressure. [ABSTRACT FROM AUTHOR]

Using transmission electron microscopy, the structure, phase composition, defects, amplitude of internal stresses and their sources are studied in the ultrafine-grained technically pure nickel produced by the method of equal-channel angular pressing (ECAP). During ECAP, the samples are subjected to shear deformation by compression along two intersecting channels of equal diameters at an angle of 120° and a temperature of T = 400°C without intermediate annealing within four passes, n = 4. An examination of the grain structure demonstrates that all grains are anisotropic. According to the dislocation structure, the grains are classified into three types: 1) the smallest grains with no substructure (practically no dislocations) – dislocation-free grains, 2) larger grains containing chaotically distributed dislocations or a net substructure, and 3) the largest grains with a cellular or fragmented substructure. The average value of the scalar dislocation density in the grains of each type is calculated. It is found out that equal-channel angular pressing results in the formation of nanosized particles of secondary phases localized inside the grains, at grain boundaries and at grain junctions of ultrafine-grained nickel. The sources of internal stresses are revealed and their amplitude is determined. The amplitude of the internal stresses is calculated using the amplitude of the crystal lattice curvature-torsion from the bending extinction contours [ABSTRACT FROM AUTHOR]

We evaluated the vaccine properties of a novel attenuated strain of M. tuberculosis BN (Mtb BN) and its impact on the gut microbiota in inbred female mice in comparison with a virulent strain Mtb H37Rv and a vaccine strain BCG. The Mtb BN strain demonstrated the highest anti-tuberculosis vaccine effect in I/St mice highly susceptible to tuberculosis infection and the same effect as BCG in mice of the recombinant strain B6.I-100 and in β2 microglobulin gene knockout mice. No adverse effects of the new Mtb BN strain on the gut microbiota of BALB/c mice were revealed. The virulent strain Mtb H37Rv and the vaccine strain BCG decreased the main indicators of normocenosis (Bifidobacterium spp., Bifidobacterium animalis subsp. lactis, Akkermansia, and Erysipelotrichaceae) and led to disappearance of Clostridium perfingens, E. coli, Pseudomonas spp., which contributed to reduction of species diversity and the development of dysbiosis. [ABSTRACT FROM AUTHOR]

We have explored the generation of plasma with high content (up to 70%) of calcium ions. The plasma is formed using an electron beam bombarding solid targets with electron energy up to 20 keV and power density up to 600 W/cm2. Target materials used are simple and readily available school chalk, limescale, and gypsum building plaster. Electron-beam erosion of the target material, production of unbound calcium atoms, and their ionization occur in a single cycle at a background pressure of a few pascals. This approach minimizes the effect of target surface charging by beam electrons and provides effective ionization of calcium-containing materials. The method described here is an alternative to the conventional method for the generation of calcium ions based on electron-cyclotron resonance systems, and is technically easier to implement. [ABSTRACT FROM AUTHOR]

Deformation relief at different stages of work hardening of Cu–12 at % Al single crystals is studied by transmission electron microscopy. The relationship between the surface topography and the stages of strain hardening and substructural evolution is analyzed. It is confirmed that stage III of deformation hardening is determined by microtwinning. The surface-topography features associated with the development of microtwinning in the slip planes are found. It is shown that the deformation relief at stage IV of deformation contains short curved slip lines. The condition for the beginning of the microtwinning process is formulated. The dislocation density required for initiation of the microtwinning process is estimated, and the estimates show good agreement with the average dislocation density measured experimentally. [ABSTRACT FROM AUTHOR]

The paper investigates commercially pure titanium VT1-0 (US analog Grade 2) in the ultrafine grain state after the aluminum ion implantation at a fluence of 1∙1017, 5∙1017 and 10∙1017 ion/cm2. The investigation techniques include X-ray diffraction analysis, scanning electron microscopy with energy dispersive X-ray analysis, and transmission electron microscopy. Auger electron spectrometer is used to analyze the chemical composition of the implanted layer. The grain size in the longitudinal and transverse directions and the phase composition of ultrafine titanium are studied depending on the irradiation exposure. It is found that the ion implantation leads to the formation of such intermetallic compounds as Al3Ti and AlTi3 phases, β-phase titanium and aluminum oxide (Al2O3). The increased irradiation exposure results in the formation of a thicker implanted layer without changing its phase composition. [ABSTRACT FROM AUTHOR]

The mechanisms of magnetite oxidation (forward reaction) and hematite dissociation (reverse reaction) are considered in terms of a general kinetic approach. The dissociation in a pellet is found to develop during sintering when temperature increases. A derivatograph is used to perform experiments with Kachkanar fluxed pellets at various heating rates in a gas containing various oxygen contents. The reaction surface and the dissociation rate are found to increase with the temperature and the slag-forming oxide content. The heating of samples in a reducing atmosphere is studied. The temperature range of reduction of partially dissociated pellets, in which their intense destruction induced by the hematite–magnetite transition does not occur, has been determined. Based on the results of analyzing the pore structure of a pellet, we conclude that, when a melt appears in the system, the dissociation in a pellet is associated with both liquid-phase sintering, when closed porosity forms, and an increase in temperature. The results obtained in this work are of great practical importance, since the use of partially dissociated pellets excludes hematite reduction in them at low temperatures and does not lead to a violation of the gasdynamic conditions of blast-furnace melting. [ABSTRACT FROM AUTHOR]

The paper reports the effect of plane tensile stresses on changes in the microstructure and phase composition in a butt joint of plates from the 304 austenitic stainless steel obtained by shielded metal arc welding. Both evolution of strain field distributions and data obtained by transmission diffraction electron microscopy are presented. The deformation-induced γ → α transformation was observed in addition to the γ → ε one. High plasticity and significant strain hardening of the steel were established. For the welded steel sample, the ratio of ultimate tensile strength to the yield point reduced from 3.3 (for the as-received metal) down to 2.6. At the elastic stage, a fragmented structure was observed in the form of local macroregions, within which strain levels differed by ±(30–40)pct from the average one over the entire area of the welded sample surface. These local macroregions were a kind of deformation or elastic-plastic domains, which could include some groups of grains. The transition from the elastic strain region to the plastic one caused a change in all strain field distributions on the welded sample surface. Small local areas merged into large homogeneous regions characterized by high strain levels. The presence of the welded joint resulted in the formation of local macroregions with both lower and higher plastic strain levels on the longitudinal and transverse field distributions in speckle images than the averaged values over the entire sample surface. These macroregions was due to the inhomogeneity of residual stresses and the deformation-induced γ → α → ε martensitic transformations. [ABSTRACT FROM AUTHOR]

Using the transmission electron microscopy of thin foils the paper studies the phase composition and fine structure of 0.18С–1Cr–3Ni–1Mo–Fe steel after plasma electrolytic carbonitriding carried out through the surface saturation with nitrogen and carbon. The steel specimens are studied before and after carbonitriding on the surface and at a ~40 μm distance from the surface. It is found that carbonitriding causes significant qualitative and quantitative changes in the steel structure. Thus, the layers of residual austenite appear along the boundaries of martensitic lamellas, and the particles of alloyed cementite and carbonitrides are observed inside the lamellas. The layers of residual austenite locate at a ~40 μm depth along the boundaries of all martensitic crystals, while inside the crystals there are only particles of alloyed cementite and carbonitride M23(C, N)6. The control parameter of changes in the structure and phase composition is the concentration of interstitial atoms of carbon and nitrogen. Changes in this concentration lead to the system deviation from thermodynamic equilibrium. The transition of system to equilibrium or quasi-equilibrium states is considered to be performed through the transition of crystal lattices, which form a gradient structural-unstable state of the matrix, intermetallics and carbonitride compounds, to a low-stability state. [ABSTRACT FROM AUTHOR]

We studied the effectiveness of anti-tuberculosis vaccination with BCG in mice of inbred strains and F1 hybrids (highly resistant to tuberculosis infection) that represent a wide range of genetically determined differences in susceptibility to infection with virulent Mycobacterium tuberculosis. The greatest relative effect was found in susceptible mice, with the exception of highly susceptible I/St mice that were practically not protected by vaccination. Despite significant effect of vaccination in inbred mice, their resistance to M. tuberculosis infection did not exceed that of non-vaccinated highly resistant F1 hybrids. [ABSTRACT FROM AUTHOR]

Nowadays, initial assessment of welding quality is performed by testing equipment with increased loads (high pressure) at technical devices of hazardous production facilities. Test requirements are regulated by standards of the Federal Service for Environmental, Technological and Nuclear Oversight of Russia (Rostekhnadzor). Recently, along with traditional tests, a "stress test" was used—the essence of which is to load pipeline sections to the yield point, followed by leak test. However, in scientific publications, there is practically no information about physical processes occurring in the base metal and in welded joints during such tests. In addition, effect of preload (deformation) on the parameters of substructure and internal stress field in welded joints of austenitic steels and, consequently, on the further trouble-free operation of the tested equipment was not evaluated. The paper analyzes changes in the structural state and values of internal stresses in the austenitic steel samples under the action of high loads, which substantiates the use of modulated current welding with automatic control of heat input process in molten weld bath. The allowed limits of plastic deformation are substantiated when testing technical devices with high pressure for this type of steel. In order to reduce the risk of damage to austenitic steel welded joints of technical devices of hazardous industrial facilities, performed by pulsed welding with small-droplet transfer and to exclude formation of microdefects in them, high pressure tests (stress test) should be performed under loads that create deformations in metal that do not exceed 5%. For joints welded by manual arc welding, deformations should be less than 5%. Welded joints made by pulsed welding with large-droplets transfer (with and without defects) are not recommended to be tested at high pressure. [ABSTRACT FROM AUTHOR]

Using transmission electron microscopy (TEM), phase composition and fine texture changes in the ferrite-pearlitic steels 0.18C–1Cr–3Ni–1Mo–Fe, 0.3C–1Cr–1Mn–1Si–Fe and 0.34C–1Cr–1Ni–1Mo–Fe due to electrolytic plasma nitrocarburizing has been studied in thin foils. The procedure of electrolytic-plasma enhanced nitrocarburizing has been performed by steel surface saturation with nitrogen and carbon in an aqueous solution at a temperature of 800–860°C for 5 min. All the steels under investigation have been studied before and after the nitrocarburizing procedure. In the initial state, the steels were discovered to be composed of a pearlitic and ferritic grain mixture. The nitrocarburizing procedure leads to the formation of modified layers. Thus, the greater is the amount of pearlite before nitrocarburizing, the thicker is the modified layer. Nitrocarburizing results in significant qualitative changes in the phase state and the steel structure. In the modified layer surface area alongside the matrix, the particles of other phases such as carbides, nitrides and carbonitrides occur. As the distance from the surface of a nitrocarburized sample increases, the phases of set and volume decrease, whereas the only carbide phase—cementite—occurs at the end of modified layer in the case of all the steels. After nitrocarburizing, the matrix of all the steels represents tempered lath and lamellar martensite. In the nitrocarburized layer surface zone, the volume fractions of lath and lamellar martensite depend on the initial steel state: the greater is the amount of pearlite in steel, the less is the amount of lath martensite; then a greater amount of lamellar martensite is formed. Such a dependence is not observed in the nitrocarburized layer central zone, whereas the volume fractions of lath and lamellar martensite at the end of the layer are close to each other. [ABSTRACT FROM AUTHOR]

The paper studies the structure and phase composition of steel 0.12C–1Cr–1Mo–1V–Fe (grade DIN 14MoV63) after a long-term operation using the transmission electron microscopyю Investigated are the nontreated specimen (not subjected to operation) and specimens after a long-term operation with and without fracture. The phase composition and morphology of the steel structure are determined for each specimen. It is found that the steel servicing leads to the destruction of lamellar perlite, intensive fragmentation of ferrite, redistribution of the carbide component and elastic distortion of the crystal lattice. [ABSTRACT FROM AUTHOR]

The principle of operation and the characteristics of the experimental equipment intended for the generation of boron ion plasma and beams are presented. The equipment comprises a vacuum arc source of boron ions with boron isotope separation in a magnetic field and a plasma generator for deposition of boron-containing coatings based on a planar magnetron sputter. Common to this equipment is the use of lanthanum hexaboride cathodes, but for planar magnetron, a pure boron cathode heated in the discharge is also used. It is shown that, when silicon wafer is implanted with beams of 10B+ and 11B+ boron isotope ions with doses of 1014–1016 ion/cm2, the isotopic effect of the diode properties of the implanted surface is observed. The results of studies of the properties of the obtained boron-containing coatings on model materials: stainless steel, crystal silicon, and E110 (Zr–1Nb) reactor alloy are presented. [ABSTRACT FROM AUTHOR]

The paper presents the transmission electron microscopy investigations of the structure and phase composition of ferritic-perlitic ST2 steel surface after electrolytic plasma quenching. The steel in the initial state represents the material after hardening at 890°С for 2 or 2.5 hours and quenching in warm (30–60°С) water with subsequent tempering at 580°C for 2.5 or 3 hours. Electrolytic plasma quenching is carried out at 850–900°С in an aqueous salt solution for 4 seconds, at 320 V voltage and 40 A current. In the initial state, the morphology of the steel matrix consists of lamellar perlite and nonfragmented and fragmented ferrite. Electrolytic plasma quenching of the steel surface results in the martensite transformation, steel self-tempering, and the formation of cementite particles in all martensite crystals. This treatment also leads to the diffusion transformation of γ → α phases, the release of residual austenite (γ -phase) along the low-temperature martensite laths and lamellas and in all crystals of lamellar martensite, the formation of М23С6 special carbides and, finally, to the enhancement of all parameters of the steel fine structure. [ABSTRACT FROM AUTHOR]

The paper presents the transmission electron microscopy investigations of the microstructure and phase composition of the nickel-based superalloy after high temperature annealing. All states of the superalloy are characterized by the single-crystal structure with [001] crystallographic orientation. The Ni–Al–Co alloy system also contains such elements as Mo, Cr, W, Ta, Re and Ru. The Ni–Al–Co system is studied in four states: initial (after directional crystallization) and after 1000°С annealing during 118, 372 and 1274 hours. The major phases forming the alloy system are γ- and γ′-phases. After annealing for 118 hours, the formation of Al6(Re, Ru) phase is observed. After longer high-temperature annealing new phases occur, such as σ-, δ- and Laves phase. The obtained alloy microstructure is classified into four types: 1) γ′-phase quasi-cuboids with γ-phase layers, 2) ribbon anisotropic microstructure of γ′+ γ-phase, 3) ribbon anisotropic microstructure with σ-phase particles in γ-phase layers, 4) γ-phase with δ-phase and Laves phase inclusions. The introduction of a large amount of various alloying elements and the annealing process modify the crystallographic texture of the superalloy. [ABSTRACT FROM AUTHOR]

The paper presents the transmission electron microscopy (TEM) investigations of the thin film structure and phase composition of the heat-affected zone (HAZ) of a weld joint produced by manual metal arc welding (MMAW) of 0.12C–18Cr–10Ni–1Ti–Fe austenite steel exposed then to plastic deformation. The test machine INSTRON-1185 is used to perform quasi-static tensile tests at room temperature and a 1.7∙10–4 s–1 strain rate up to 5 and 37% deformations. TEM investigations are carried out within the HAZ, at a 1 mm distance to the weld line, in the direction of the parent metal and at 0.5 mm distance to the weld deposit. It is shown that MMAW results in the formation of ε-martensite both in the parent metal and weld deposit regions. In the latter, γ → ε phase transformation occurs faster. Plastic strain ranging between 0–5% throughout the HAZ leads to further γ → ε phase transformation. In the weld deposit of the HAZ region, this phase transformation is also more intensive. Further increase in the degree of plastic strain from 5 to 37% results in γ → ε → α phase transformation and an elastoplastic lattice distortion of the α-phase. The plastic flexure remains in the crystal lattice of the γ-phase. The bulk material in the HAZ region satisfies the following conditions: scalar dislocation density is higher than the excess, and internal shear stresses are higher than long-ranging. [ABSTRACT FROM AUTHOR]

Electroconvection is the principal mechanism that allows markedly increasing the rate of ion transfer through ion-exchange membranes in intensive current regimes. In this work, we investigated the possibility of intensifying electroconvection in solution near heterogeneous MA-41 anion-exchange membrane (Shchekinoazot production) by the modifying of its surface. The use of weakly crosslinked ion-exchange resin (MA-41P) in the course of the membrane manufacturing, with subsequent chemical modification of its surface (MA-41PM), is shown to make it possible to increase the limiting current density almost twice. The value of the reduced potential drop (after subtracting the ohmic contribution), at which significant generation of H+ and OH– ions begins, is shifted from 0.8 V in the case of MA-41 to 1.7 V in the case of MA-41PM. The current density related to the onset of water splitting is equal to 0.9 in the case of MA-41; 2 in the case of MA-41PM (where is the theoretical value of the limiting current density). The special feature of the modified membrane behavior is the presence of a range of potential drop (between 50 and 80 mV in the reduced scale), in which the system with the MA-41PM has negative differential resistance: in this range, the potential drop decreases when the current density increases. This behavior occurs when measuring quasi-stationary I–V curves; correspondingly, in the chronopotentiogram there is a time interval, where the potential drop decreases with time. The electroconvection is intensified near a modified membrane due to a higher fraction of conductive areas on the surface of the modified membrane and the redistribution of these areas via formation of their agglomerates in the centers of the cells formed by the reinforcing mesh. Mathematical modeling shows the concentration polarization of the modified membrane being less than that of the pristine one. Meanwhile, the structure of electroconvective vortices is optimized: the vortices near the modified membrane are larger; they do not extinguish each other, unlike the case of MA-41. [ABSTRACT FROM AUTHOR]

Infectious process even at the initial stage after aerosol infection with Mycobacterium tuberculosis induced rapid changes in vaginal microbiota in mice. Rapid decrease in both the quantity and diversity of microbiota was noted, and then, partial recovery of normal flora was observed. Changes in vaginal microbiota was detected as soon as in 3-7 days after lung infection, while inflammatory changes appeared by day 35. At the early stage of infection, no signs of inflammation were observed, neither M. tuberculosis nor its DNA were detected in mouse genital organs. [ABSTRACT FROM AUTHOR]

Carbide–boride coatings applied on both sides of V96Ts aluminum alloy samples by electric spark alloying (ESA) are metallographically studied. The coated samples are processed by laser on one side. Laser treatment of the surface decreases the pronounced roughness, pores, and cracks visible after ESA. Laboratory tests suggest combined (electric-spark–laser) hardening of the surface of V96Ts aluminum alloy samples to extend the service life of tools and machine parts. [ABSTRACT FROM AUTHOR]

Abstract: The effect of pH and concentration of the NaCl solution on the exchange capacity and transport properties of the MA-40 and MA-41 anion-exchange heterogeneous membranes with different nature of fixed groups has been studied: MA-40 has weakly basic groups, and MA-41 has strongly basic groups with a small proportion of weakly basic ones. The exchange capacity, thickness, water content, and electrical conductivity of the membranes equilibrated with NaCl solutions of various concentrations and pH were measured; for the same solutions, the diffusion permeability coefficients were found. The capacity was measured in the pH range from 1.5 to 12; the remaining properties, in the pH range from 3 to 9. Using the values of electrical conductivity and diffusion permeability, the ion transport numbers in the membranes were calculated. It was shown that at the external solution pH 9 the thickness of the membranes and their electric conductivity are minimal, and the transport numbers of co-ions are maximum. This is explained by the fact that in basic solutions weakly basic functional groups are largely deprotonated, and the effective capacity of the membrane is significantly reduced. The maximum effective capacity is achieved at pH 3; in this case, transport numbers of co-ions in the MA-40 membrane are 5-fold, and in the MA-41 membrane, two-fold lower than corresponding values at pH 6 and 9. The changes in the transport properties of the membranes with increasing pH are due to a decrease in the degree of protonation of weakly basic functional groups, these changes are more pronounced for the MA-40 membrane than for MA-41. [ABSTRACT FROM AUTHOR]

We have demonstrated that long-term exposure of intact mice to rifampicin (6 months) induces resistance to this drug, which manifested in inability of rifampicin to suppress the growth of Mycobacterium tuberculosis in the lungs and spleen during subsequent infection. It the same time, isoniazid is still effective in these mice. In this case, the phenomenon of somatic resistance to rifampicin in mice was observed if the treatment was started in a short period (within 4 days) after infection with M. tuberculosis. If the interval between infection and rifampicin administration was longer (3 weeks), the resistance disappeared. [ABSTRACT FROM AUTHOR]

This article presents the results of hybrid treatment (cold working, ESA) of 09G2S structural low alloyed steel aimed at improving operation reliability. [ABSTRACT FROM AUTHOR]

Abstract: A series of anion-exchange membranes based on a Neosepta AMX-Sb homogeneous membrane (Japan) have been studied by applying parallel nonconducting strips of a 100 to 600 μm width with the interstrip distance ranging from 400 to 1900 μm. The current-voltage characteristics of the membranes and the pH of a NaCl solution (of 0.02 mol/L concentration) have been measured in the course of passing the solution through the desalination compartment of a flow-through electrodialysis cell. Two sets of membranes with a nonconducting surface fraction snc of 5 to 60%, in which the pattern steps on the surface are 1000 and 2000 μm, have been considered. It has been shown that the limiting current density, ilim, depends on the nonconducting surface fraction: ilim exceeds the corresponding value for the initial membrane in the case when snc is in the range from 5 to 20%, reaching a maximum approximately at snc = 10% followed by a decrease with the further increase in snc. At snc = 10%, the value of ilim is greater when the inhomogeneity step is 2000 μm. It has been assumed that the growth in both the limiting current density and the rate of mass transfer through the modified membranes is due to electroconvection. The obtained experimental results correlate well with known mathematical models describing ion transport in membrane systems with allowance for electroconvection in the case of homogeneous and heterogeneous membranes. [ABSTRACT FROM AUTHOR]

Pulsed electric fields (PEF) have been used to advantage in electroplating for more than half a century. Recently, interest has increased in the application of these electric modes in the membrane processes. In this work, the effect of parameters (potential, frequency of current, and duty cycle) of pulsed current mode on the average current density in the electrodialysis cell is studied. For this purpose, the plots of current vs. time were measured in the mode of pulsed potential drop on a Nafion 438 (NafionTM N438) cation-exchange membrane. It is shown that the largest gain in the current density of 33% can be attained by varying parameters of PEF. [ABSTRACT FROM AUTHOR]

Using the methods of electron diffraction microscopy and X-ray diffraction analysis, the influence of alloying of the austenitic steel, Grade 110H13, with chromium and vanadium, as well as high-melting, ultrafine-grained TiO, ZrO powders and NaAlF cryolite on its structural-phase state and microstructure is investigated. It is shown that the matrix of non-modified steel is completely austenitic and consists of an iron-based solid solution and the interstitial (C, N, O and other) and substitutional (Cr, V and other) atoms simultaneously. Alloying with chromium and vanadium changes neither its phase composition nor defect structure, while alloy modification results in qualitatively new structural features: γ → ε-transformation, high-intensity microtwinning, defect structure changes, and a sharp increase in the scalar dislocation density. The features of the deformation-induced microtwinning and ε-martensite plates identified in the modified steel promote revealing additional microtwin systems in the matrix γ-phase, which result in structural changes making it possible to classify it as a γ′-phase. It is found out that an introduction of modifying additions gives rise to the following sequence of structural-phase transformations: γ→γ′→(γ′ +ε). The experimental data obtained demonstrate that as a result of modification the crystal lattice transits into a low-stability state. This transition is accompanied by marked structural-phase changes consisting in the formation of several microtwin systems and γ → ε-transformation. These structural-phase changes in the modified steel are due to the crystal-lattice transition into the low-stability state, followed by new structural-phase alterations. [ABSTRACT FROM AUTHOR]

The preparation of inorganic brown pigment from red mud is investigated. The results of the phase and chemical analyses of raw material and the product are given. A flow diagram is proposed and the parameters of the pigment production are recommended. This approach has provided a pigment of pure color with the opacity of 8 to 10 g m-2 from red mud (up to 80%) without additives and the reduction of Fe(III) into Fe(II) using sulfide sulfur. [ABSTRACT FROM AUTHOR]

Changes in the structural and phase state of low-carbon steel with a mixed structure of tempered martensite and ferrite, and deformed by equal channel angular pressing (ECAP), are analyzed by means of transmission electronic microscopy and X-ray diffraction. The impact ECAP has on the phase composition and morphology of the alloy is determined. The behavior of the carbide phase is studied. Grain misorientations are measured. Special attention is given to the problem of fine grain formation upon ECAP. [ABSTRACT FROM AUTHOR]

The concentration dependences of the electrolyte sorption, specific electric conductivity, and diffusion permeability of MK-40 and Nafion-117 cation-Ion-exchange membranes in NaCl solutions have been obtained experimentally. Both the membranes contain macropores. The heterogeneous MK-40 membrane contains pores with a size of up to 1 μm between the particles of the ion Ion-exchange resin and polyethylene. The homogeneous Nafion-117 membrane has been subjected to a special thermal pretreatment which results in the formation of macropores. It has been shown for the first time that these experimentally found relationships can be quantitatively described using one set of structural and kinetic parameters of the microheterogeneous model. [ABSTRACT FROM AUTHOR]

The properties of high-temperature nickel alloys for manufacturing depend on the thermal stability of the structure, the particle size, the shape, the quantity of strengthening γ' phase, and the strength of the γ solid solution. Such alloys are strengthened by the addition of rhenium and lanthanum. In the present work, the structure and phase composition of high-temperature nickel alloy with added rhenium (0.4 at %) and lanthanum (0.006 at %) are qualitatively and quantitatively investigated. The methods employed are transmission diffraction electron microscopy and scanning electron microscopy. The alloy structure is considered in three states: after directed crystallization (the initial state, sample 1); after directed crystallization, annealing at 1150°C for 1 h, and annealing at 1100°C for 480 h (sample 2); and after directed crystallization, annealing at 1150°C for 1 h, and annealing at 1100°C for 1430 h (sample 3). Primary and secondary phases are observed in the superalloy. The primary phases are γ' and γ. They form the structure of the alloy and are present in the form of γ' quasi-cuboids separated by γ layers. The secondary phases due to the presence of rhenium and lanthanum are β NiAl, AlRe, NiAl2Re, σ, χ, and Ni3La2. The secondary phases seriously disrupt the structure of the γ + γ' quasi-cuboids. The rhenium and lanthanum do not uniformly fill the whole alloy volume, but only appear in local sections. Therefore, in all three states of the alloy, only some volume of γ + γ' quasicuboids is disrupted. Analysis of the secondary phases’ morphology shows that the σ particles are thin needles, whereas the Ni3La2 particles have internal structure with characteristic contrast and are relatively thick. Interestingly, the σ phase and Ni3La2 are deposited at the same locations. The introduction of rhenium and lanthanum changes the phase composition of the alloy, suppressing the formation of γ phase. The particles of secondary phase are localized in individual sections of the alloy with specific periodicity. The secondary phases are refractory: the melting point is about 1600°C for β phase, 2600°C for σ phase; and 2800° for χ phase. Thanks to the formation of refractory secondary phases and their periodic distribution in the structure, the strength of the superalloy with added rhenium and lanthanum is increased. [ABSTRACT FROM AUTHOR]

At current densities exceeding the limiting current density, H+ and OH- ions are generated at the interface of the ion-exchange membrane with a depleted solution as a result of the dissociation of water molecules. At present, it is generally accepted that water splitting occurs in a thin (a few nanometers) layer inside the membrane, this reaction being catalytic in nature. The mathematical model of ion transport in the diffusion layer near the membrane surface has been constructed and numerically studied under conditions when dissociation and recombination processes involving water molecules and H+ and OH- ions occur simultaneously. It has been shown that in overlimiting current regimes under very high voltages, intense noncatalytic dissociation of water molecules in the extended space charge region of the depleted solution can occur irrespective of the catalytic splitting of water. Since this region has macroscopic dimensions, the rate of noncatalytic water dissociation is comparable with the rate of the corresponding catalytic process. The obtained results significantly supplement modern concepts of the mechanism of generation of H+ and OH- ions in membrane systems, showing that this process can proceed not only in accordance with the conventional mechanism with the catalytic participation of functional groups and/or other compounds, but also via the noncatalytic mechanism that has not been taken into account to the present. [ABSTRACT FROM AUTHOR]

Single-pulse and double-pulse chronopotentiograms of a homogeneous anion-exchange membrane AX in 0.02 M solutions of NaCl (system 1) or NaH2PO4 (system 2) have been recorded in underlimiting and overlimiting current modes. It has been found that in the case of exceeding the limiting current (i >ilim Lev ) calculated using the convection–diffusion model, the time required to establish a steady state in system 2 increases by more than an order of magnitude compared to system 1. The slow growth of the potential drop is due to a gradual transition of the membrane from the form in which the main counterion is H2PO 4 – to the HPO4 2– form. This transition is due to the deprotonation of a part of H2PO 4– ions forming HPO 4 2– and protons as they enter the membrane. The participation of H+ in charge transfer in the depleted diffusion layer at a given current density causes a lower value of the potential drop than in system 1 for the same i/i lim Lev ratio. In intense current regimes, chronopotentiograms of system 2 exhibit two inflection points. The first point corresponds to the classical Sand transition time and is due to reaching the limiting current of H2PO 4 – ions (the main charge carrier for i < i lim Lev ) in the depleted diffusion layer. The second point is associated with a critical current that can be called the second limiting current in the system with NaH2PO4 and has no analogue in the system with NaCl. This current, which is approximately 2ilim Lev , corresponds to the state when the membrane is completely transformed into the HPO4 2– form. Meanwhile, the source of protons due to the transformation of H2PO 4 – into HPO 42– ions as they enter the membrane is exhausted. After reaching this critical value of the potential drop, either the HPO4 2– deprotonation reaction to give triply charged PO 43– ions in the membrane or the water splitting on fixed groups located at the membrane/solution interface may occur. [ABSTRACT FROM AUTHOR]

of electron microscopic study of Ni-Cr-Al based superalloy are presented. The superalloy prepared by the method of directed crystallization is investigated in the initial state and after creep for 10 h at Т = 1100°С and σ = 100 MPa. It is established that the alloy in both states is formed by γ and γ' phases based on the FCC crystal lattice; the γ' phase has ordered arrangement of atoms (the L1 superstructure) and is the main phase in all states. The phase composition and morphology are studied. The change in the phase composition and particle sizes of phases as a result of creep is analyzed. The influence of the high-temperature creep on the superalloy structure is established. [ABSTRACT FROM AUTHOR]

Overlimiting current modes are of considerable interest for the practice of electrodialysis (ED). However, the economical expedience of such ED modes is evident only for desalination of dilute solutions. Here, we show the theoretical analysis of the effect of concentration on the behavior of an ED cell with homogeneous ion-exchange membranes. The study is based on numerical solution of the two-dimensional system of coupled equations of Nernst–Planck–Poisson–Navier–Stokes. It is shown that as the electrolyte concentration in solution that enters the ED desalination chamber increases, the intensity of electroconvection decreases, which induces a decrease in the relative mass-transfer rate (the decrease in the ratio of current density to its limiting value). This effect is stronger in the region of high potential differences where the electroconvective instability of Rubinstein–Zaltzman is realized under the conditions of a nonuniform concentration field caused by solution desalination. In contrast, the increase in the counterion concentration at the membrane surface (associated with the increase in the surface charge) intensifies the electroconvection. [ABSTRACT FROM AUTHOR]

The modern concepts on the origin of electroconvection (EC) are surveyed briefly and the known mechanisms of this phenomenon are classified. Factors that influence the EC character and intensity at the surface of ion-exchange membranes are analyzed, such as electrical and geometrical heterogeneity of the membrane surface, its degree of hydrophobicity, and the surface charge. The EC mechanism is shown also to depend on the applied potential difference and the rate of solution flow between membranes. The mechanism of the EC-induced gain in the mass transfer is elucidated, the possible gain in the mass transfer is estimated, and the prospects for using the EC for reducing the membrane fouling caused by sedimentation and formation of organic deposits are assessed. [ABSTRACT FROM AUTHOR]

The features of electroconvection in a smooth rectangular desalting channel of an electrodialysis apparatus with heterogeneous ion-exchange membranes have been theoretically investigated. A 2D model of electroconvection for a binary electrolyte has been constructed for overlimiting current regimes in the form of the Nernst-Planck-Poisson and Navier-Stokes equations. The influence of surface morphology of the heterogeneous ion-exchange membranes on vortex structures and on mass transfer of salt ions has been studied. The current-voltage characteristic has been calculated for the heterogeneous ion-exchange membranes. It has been shown that mass transfer in the membrane channel can be enhanced by improving the surface morphology of the heterogeneous ion-exchange membranes. The strong-base homogeneous membrane AMX and the modified heterogeneous membrane AMH-M have been studied using the rotating membrane disk technique. [ABSTRACT FROM AUTHOR]

Using transmission electron microscopy and X-ray diffraction analysis, the structural-phase state of steel 0.1C-2V-1Ti-Fe, deformed by the SPD methods and subjected to high-temperature annealing at the temperatures 600 and 700°С, is investigated. The influence of the steady temperature on the grain size, steel phase composition, carbide transformations, carbide particle size and distribution density, carbon distribution, and fine-structure parameters are determined. A special focus is made on the sources of internal stress. [ABSTRACT FROM AUTHOR]

The high-temperature hydrolysis of magnesium nitrate hexahydrate is studied. The presence of basic magnesium nitrate in the decomposition product at 160°C is found by IR spectroscopy and X-ray diffraction analysis. A mechanism for the high-temperature hydrolysis of Mg(NO) · 6HO is proposed. [ABSTRACT FROM AUTHOR]

The paper presents the transmission and the scanning electron microscope investigations of the phase composition and fine structure of Ni-Al-Cr-based alloy alloyed by rhenium and lanthanum. The alloy is prepared by the directional crystallization technique and then subjected to 1150°С annealing during 1 hour. It is shown that γ- and γ′-phases are major and have a face-centered cubic crystal system. Solid solutions of γ- and γ′-phase have a disordered and an ordered atom arrangement, respectively. The latter has L12 superstructure. It is found that rhenium and lanthanum alloying leads to the structural modification of γ′-phase quasi-cuboids. Not dissolving in major phases, rhenium and lanthanum are phase-formation elements and form σ-phase. The phase composition and morphology of these phases are studied and described. [ABSTRACT FROM AUTHOR]

The formation of organic colloidal particles in the pores and on the surface (fouling) of membranes used in the food industry is a significant constraint on the further development of membrane technology. A model to describe the effect of these particles on electric conductivity and diffusion permeability has been proposed. It is based on a microheterogeneous two-phase model constructed in terms of the concepts of nonequilibrium thermodynamics and effective medium theory. The model takes into account the presence of two phases: (i) the gel phase comprising a polymer matrix and fixed ions whose charge is compensated for by mobile ions and (ii) the electrically neutral solution filling the intergel spaces. Each of the phases is characterized by intrinsic thermodynamic and kinetic parameters. The model takes into account changes in the values of these parameters caused by the formation of organic nanoparticles in meso- and macropores (fouling). It is assumed that the formation of colloidal particles in the intergel solution leads to a decrease in the ion mobility. In addition, these particles are capable of deprotonating a portion of the fixed ions and thereby decreasing the exchange capacity of the membrane. A high degree of hydration of these particles is responsible for an increase in the volume fraction of intergel spaces. Selection of relevant model parameters provides good agreement between calculation and experimental results. [ABSTRACT FROM AUTHOR]

By transmission diffraction electron microscopy, study of the changes in the phase composition arising in 0.3C-1Mn-1Si-Fe steel upon plasma electrolytic nitrocarburizing with increasing distance from the modified surface is performed. It is found that, with increasing distance from the surface, the list of carbonitride phases and their volume fraction are reduced. The morphology of the steel matrix is changed. [ABSTRACT FROM AUTHOR]