Search

TEM and X-ray diffraction studies were carried out to examine changes in the structure, phase composition, and defect substructure in the head of a differentially hardened rail after 691.8 and 1411 million gross tons (MGT) of traffic. The rail material was examined along the central axis of the head and along the gauge corner radius at distances of 0, 2, and 10 mm from the tread surface. The redistribution of carbon atoms was quantitatively analyzed. It was shown that long-term operation of rails is accompanied by two simultaneous processes related to the evolution/degradation of the structure and phase composition of lamellar pearlite colonies, namely, cutting and cold dissolution of cementite lamellae. The first process involves the cutting of carbide particles and the subsequent dragging of their fragments, which causes changes only in their linear dimensions and morphology. The second process is the fracture of cementite lamellae in pearlite colonies due to the migration of carbon atoms from the cementite lattice to dislocations, which creates favorable conditions for a structural-phase transformation in the rail metal. The reason of this is the low average binding energy of carbon atoms with dislocations (~0.6 eV) and with iron atoms in the cementite lattice (~0.4 eV). Cementite nanoparticles were revealed in the ferrite matrix; their appearance was accompanied by dislocation glide and deformation-induced decomposition of carbon solid solution in α-iron. The curves of the change in the total yield strength versus the distance to the tread surface along different directions in the rail head were plotted. The carbon content in the structural elements of rail steel was estimated. It was found that carbon in the initial state is mainly contained in cementite particles, while in rails subjected to traffic loading it is located, along with cementite particles, at crystal structure defects (dislocations, grain boundaries, subgrains). In the surface layer of steel, carbon is also present in the crystal lattice of α-iron. The results on the redistribution of carbon atoms are interpreted using the concept of interstitial bifurcation structural states in lattice curvature zones.

The paper studies the effect of the temperature of helical rolling, which creates nanoscale mesoscopic structural states in lattice curvature zones, on the low-temperature impact toughness of Ti–6Al–4V alloy. The polymorphic transformation temperature Tс = 950°C is shown to play the decisive role in this effect. The impact toughness is very high at helical rolling temperatures above Tс, while in the low-temperature range up to T = –70°C it decreases monotonically. This is a very important aspect of the technology. Starting from the helical rolling temperature T = 950°C, the toughness sharply decreases at T = –70°C. At T = 900°C, it decreases sharply already at T = –20°C. At T = 850°C, the level of the entire toughness curve of the alloy is low. The high level of impact toughness at T > Tс is found to be due to a two-stage transformation of the bcc β phase into a mixture of (α + β) phases. The first stage involves nonequilibrium microscopic decomposition into the α and β phases. At the second stage, the nonequilibrium β phase decomposes into (α + β) subbands in accordance with the interstitial structural states associated with lattice curvature. In helical rolling at T < Tс, the formation of martensite phases in the close-packed lattice of the α phase of titanium reduces its impact toughness. The fatigue life of Ti–6Al–4V alloy helically rolled at T = 1000°C remains unchanged.

The effect of hydrogen charging, ultrasonic treatment, and hydrogen charging after ultrasonic treatment on the fatigue life of VT6 alloy is investigated. Ultrasonic treatment causes the formation of a continuous nonetching α2(Ti3Al) layer within the surface layer, which reduces the fatigue life. Below this layer there are bands of the α2(Ti3Al) phase which, on the contrary, increase the fatigue life. These two effects together give a 1.3-fold increase in the fatigue life of the alloy. A catastrophic decrease in hydrogen charging after ultrasonic treatment is explained by the formation of regions of short-range displacements with a bcc lattice similar to the β phase. As a result of radial shear rolling, a martensitic phase with very high strength is formed in the alloy. Its formation is predicted by positron annihilation spectroscopy and is detected by transmission electron microscopy. The high stability of the martensitic phase contributes to the lower fracture toughness of the alloy processed by radial shear rolling.

Ultra-high molecular weight polyethylene (UHMWPE) possesses distinctive properties, but has an extremely low melt flow rate (MFR) of about zero, which makes it unsuitable for processing by standard methods for polymers. The aim of this paper was to investigate the tribological properties of two-component UHMWPE-based composites with different content of isotactic PP. The composites were fabricated by three methods: a) hot pressing of the powder mixtures; b) hot compression of granules; and c) 3D printing (FDM). It was shown that the UHMWPE-based composites obtained by extrusion compounding (hot compression of granules and 3D printing) in terms of the mechanical and tribological properties (wear resistance, the friction coefficient, Young's modulus, and yield strength) were superior to the ones manufactured by hot pressing of the powder mixtures. The most effective was the ‘UHMWPE+20% PP’ composite in terms of maintaining high tribological and mechanical properties and the necessary melt flow rate (MFR) in a wide range of loads. It was recommended as a feedstock for additive manufacturing of complex-shaped products (joint components) for friction units in orthopedics.

Introduction. Electrospark alloying is used to produce hardening coatings. Anodic materials with unique properties include metal matrix composites based on aluminum. The aim of the work is to develop new aluminum matrix anode composite materials with high efficiency indicators during electrospark alloying of carbon steel 45. Materials and Methods. Structural carbon steel 45 was used as the substrate (cathode). Aluminum matrix materials are chosen as the anode materials. The value of the cathode weight increment and the anode erosion were determined by the gravimetric method on the Shinko Denshi HTR-220 CE electronic scale with an accuracy of ±∙10–4 g. To study the microstructure and metallography of the surface of the anode materials, the microscopes EVO-50 XVP and Altami MET 3 APO from S. ZEISS were used. The device CALOTEST CSM Instruments was used to study coatings for microabrasive wear. Results. There is developed a methodological scheme for achieving the efficiency of the electric spark alloying parameters and the properties of the doped layer depending on the composition of the anodic metal matrix composite material based on aluminum with the addition of chromium and processing modes. The mode of Institute of Materials Science electrospark installation with pulse energy of 14.4 J was set for anode material application during electrospark alloying. It is established that after electric spark alloying of steel 45, the hardness and wear resistance of the surface increase by 2-3 times, and the heat resistance ‒ by 5–18 times. Discussion and Conclusion. The series of increasing the cathode mass, the erosion resistance of the electrode materials, mass transfer coefficient, heat resistance, hardness and wear resistance of the alloyed layer are obtained. The obtained series are a convenient tool for achieving various efficiency parameters in electric spark alloying depending on the selected anode material and processing modes.

How adhesion influences tribotechnical properties of polymer composites based on ultrahigh-molecular-weight polyethylene is assessed from mechanical and tribological characteristics of the compositions filled with 10 wt % glass fiber with various commercial coupling agents. The experimentally derived and interpolated data are used to build surfaces of effective tribotechnical characteristics, relating the type of coupling agent and the load-velocity mode in tribotests. A model is proposed for the tribological behavior of filled ultrahigh-molecular-weight polyethylene, which allows for an analysis of the stress-strain state with consideration for the friction coefficient, level of adhesion, and yield stress of the matrix material. Their effect on friction and wear is also studied by introducing fracture criteria. It is shown that the applied load significantly affects the wear mechanism, while the adhesive interaction between the composite phases has a much smaller effect.

X-ray diffraction analysis, transmission electron microscopy, and energy-dispersive analysis are used to study the phase and element compositions and microstructure of surface layers of the Ti–6Al–4V alloy prepared by additive 3D-printing and subjected to electropulsing assisted ultrasonic impact treatment (EAUIT). The firing pin material has been steel. It has been found that, in the course of EAUIT, the microalloying of the surface layer with iron to a depth of 5 µm takes place; the iron content reaches 22 at %. During the EAUIT, the nanocrystalline multiphase structure, which consists of titanium and iron oxides and metastable Ti4Fe and α"-Ti phases, forms within the surface layer to 2 µm deep; under the nanocrystalline layer, the layer consisting of coarse-crystalline metastable Ti4Fe phase and amorphous phase is present. At a depth of more than 4 µm, the Ti4Fe phase with a submicrocrystalline structure forms; at a depth of 5 to 10 µm, the submicrocrystalline structure formed by (α-Ti + β-Ti) phases is present. Within α- and β-Ti grains, the nanocrystalline α"-Ti phase is present. The microhardness of surface layer increases by 0.9–1.1 GPa as compared to that of untreated metal far from the surface.

A method is developed to slow down and prevent the penetration of oil and its distillation products into the ground. It is shown that impregnation of the soil with an aqueous solution of sodium polyacrylate (PAN) in low concentrations (up to 0.75 wt %) practically does not affect the throughput. However, with a further increase in the PAN concentration in a relatively small range from 0.75 to 1.5 wt %, the rate of oil and oil products’ (OOPs) seepage into the soil drops sharply, reaching almost zero at a PAN concentration in the impregnating aqueous solution of 2 wt % and the thickness of the impregnated soil layer 1 cm. This effect of impregnation on the ability to filter oil and oil products is observed for almost all the studied types of soils.

Previously, an algorithm based on two control parameters was applied to computer aided design of materials, and here the algorithm is extended to three parameters controlling the effective physicomechanical properties of polymer matrix composites: (i) the average particle size of a polymer powder, (ii) the length of reinforcing fibers, and (iii) the level of fiber–matrix adhesion. The use of these control parameters is dictated by the possibility of their ranging in terms of degrees of influence on effective material characteristics. The algorithm with built-in experimental data is applied to design a composite with specified properties on the example of ultrahigh molecular weight polyethylene reinforced with milled or chopped glass fibers. The form of data presentation shows the whole range of the three parameters which provides the desired result.

The fracture behavior of Ti0.45Al0.55N coatings under uniaxial tension was investigated at different scale levels. The coatings were deposited on 12Cr18Ni9Ti steel substrates by direct current reactive magnetron sputtering. According to molecular dynamics simulation, the nonuniform distribution of aluminum in the coatings affects the initiation and growth of cracks in them. It was found experimentally that the macroscopic fracture of Ti0.45Al0.55N coatings on a metal substrate under uniaxial tension occurs in four stages, whose duration is determined by the competition between different stress relaxation mechanisms. The effect of the coating thickness on the development of competing deformation and fracture mechanisms in the coatings is demonstrated.

In this article, the models of steel-copper and steel-aluminum bimetallic wires obtained in the course of computer simulation in Deform program were studied, the main parameters of the stress state (equivalent stress and average hydrostatic pressure) were considered. When considering the equivalent stress, it is found that in the model with an aluminum shell, a fairly uniform distribution of stress is observed over all layers; in the model with a copper shell, due to the intensification of compression of the steel core, the stress distribution in both layers is extremely uneven – in the shell, the stress level decreases sharply in the direction from the outer layers to the inner ones. When considering the average hydrostatic pressure, it is found that when the aluminum shell changes to copper, the hydrostatic pressure in both layers increases in absolute values, which is a consequence of an increase in the overall level of deformation resistance.

The applicability of a high-pressure xenon based spectrometer for determining the parameters of radioactive contamination of soil or building structures by 137Cs resulting from a radiation accident was studied. For soil contaminated by 137Cs with an exponential depth distribution, the Monte Carlo method was used to calculate the characteristics of the radiation field at the detection height and the instrumental gamma spectra. It is shown that there is promise in using such a detector to determine the parameters of the contamination penetration into the interior volume of the material. It is shown that the sensitivity of the measurement of activity along depth depends on the width of the working zone in the valley and the influence of the thickness of the body of the detector is determined.

Here we report the study on synthesis and characterization of nanocomposites obtained by in situ catalytic polymerization of ethylene and hexene-1 on metallocene catalyst in the presence of dispersed surface-functionalized -Al2O3 nanofibers (Nafen). It has been determined that surface treatment of Nafen nanofibers with organosilanes allows to obtain stable nanoscale dispersions under ultrasonication. It has been shown that nanocomposites based on copolymers of ethylene with hexene-1 demonstrate improved resistance to thermal oxidative degradation in comparison with nanocomposites based on copolymers of ethylene with propylene, while the influence of the silane chemistry on the mechanical characteristics in these nanocomposites is less pronounced. The best mechanical characteristics were achieved for nanocomposite with Nafen treated with trimethoxyvinylsilane. The melt flow index drop is observed after moderate heat treatment or combined temperature/humidity.

The mechanical and tribological characteristics of ultra-high molecular weight polyethylene (UHMWPE) with identical molecular weight, but different sizes of the initial polymer powder (5–15, 120–150, and 330 μm), are investigated at various load-speed parameters of tribological tests (P∙V). Structural analysis of subsurface layers beneath the friction track was carried out in the investigated range of loads and sliding velocities (P = 60–140 N, V = 0.3–0.5 m/s). The relationship between the wear intensity and the level of elastic recovery (reversible deformation) is estimated in order to assess the possibility of subsequent practical use of its value for predicting the service life of products under various operating conditions. It is shown that the initial UHMWPE powder size determines the parameters of structural elements (spherulites), as well as the degree of crystallinity of samples fabricated by hot pressing. For the studied materials and the range of load-speed parameters, it is shown that the ratio of the crystalline -to-amorphous phases, as well as the magnitude of the load under tribological loading, determine the level of elastic recovery. It is shown that under moderate triboloading conditions (P∙V = 60 N∙0.3 m/s), the highest value of elastic recovery (63%) is possessed by UHMWPE fabricated from a fine powder and having a maximum degree of crystallinity 56.5%. In UHMWPE samples obtained of the medium-dispersed and coarse powders with the crystallinity of ~30%, the level of elastic recovery is about 40%. Under severe conditions of tribological tests (P∙V = 140 Н∙0.5 m/s), the level of elastic recovery for all sizes of UHMWPE powder does not exceed 8%. It follows from the results obtained that the level of elastic recovery (reversible deformation) of ultra-high molecular weight polyethylene is one of the factors limiting the permissible operating intervals (P∙V) of the tribounit components and can be used to predict their service life.

A kinetic model is proposed to describe the key features of development of an acute viral infection, accumulation of antibodies, and immune response in the human body. The general features of immune system stimulation by thermoheliox are described. The model can be used for developing the basis for the application of thermoheliox in the treatment of patients affected by coronavirus.

The effect of carbon fiber dimensions on mechanical and tribological properties of the composites based on two thermoplastic matrices of different physical-chemical nature (polyphenylene sulfide, PPS, and ultrahigh molecular weight polyethylene, UHMWPE) is compared. It is shown that the supermolecular structure formed by compression sintering of PPS and UHMWPE controls the distribution pattern of carbon fibers in the matrix, which affects the level of tribological properties. The composites on a high-strength PPS-matrix, designed for structural/tribotechnical applications and loaded with short carbon fibers (70 μm), can be fabricated at a high loading degree (40 wt.%), which provides a five-fold increase in wear resistance and a 1.7-fold decrease in friction coefficient. The wear resistance increases due to the formation of a third body consisting of wear debris, which essentially reduces the friction coefficient. Loading the PPS with carbon nanofibers modifies the polymer matrix structure through the dispersion hardening mechanism but does not improve its tribological properties. Adding chopped carbon fibers (with a length of a few millimeters) into the PPS matrix gives rise to substantial hardening but significantly degrades the tribological properties. The UHMWPE composites can be manufactured via filling the matrix with 10 wt.% chopped carbon fibers evenly distributed in it. Carbon nanofibers are thought to be the most efficient fillers for the UHMWPE matrix of a spherulitic supermolecular structure in terms of increasing its wear resistance. They play the role of a solid lubricant medium (wear resistance increases 2.7 times, the friction coefficient is decreased twice). Comparatively long chopped carbon fibers of the millimeter range (2–3 mm) play a reinforcing role in contrast to the short carbon fibers measuring tens and hundreds of micrometers (70, 200 μm). They neither increase the friction coefficient nor result in the abrasive wear of the steel counterpart. The role of interphase adhesion, polymer matrix hardness, its chemical reactivity and supermolecular structure in forming the tribomechanical properties of carbon composites based on thermoplastic matrices of different physical-chemical nature is discussed.

A kinetic model of the development of acute viral infection is proposed and the dynamic behavior of key variables, including the concentrations of viral particles, infected cells, and pathogenic microorganisms, is described. The change in the hydrogen ion concentration in the lungs and pH dependence of the activity of carbonic anhydrase, a key respiration enzyme, are critical factors. An acute bifurcation transition determining either the life or collapse of the system is demonstrated. The transition is associated with exponential increase in the concentrations of participants in the process and with functioning of the key enzyme, carbonic anhydrase. A physicochemical interpretation is given for the therapeutic effect of temperature rise and potential therapeutic effect of "thermoheliox", that is, breathing by heated helium-oxygen mixture.

—A comparative analysis of the structural, tribological, and mechanical properties of polymer–polymer composites with the optimized composition UHMWPE + 15 wt % HDPE-g-SMA + 15 wt % PP, obtained by FDM (fused deposition modeling) and compressive sintering (hot-pressing) methods has been performed. It is shown that the tribomechanical characteristics (wear resistance, friction coefficient, elasticity modulus, yield limit, strength, elongation at break) of 3D-printed extrudable polymer–polymer UHMWPE composites exceed those of hot-pressed composites due to a more homogeneous supramolecular structure with enlarged crystallinity. Tribotests of extrudable UHMWPE composites in different friction modes (PV) demonstrates their applicability in joints operating in a wide range of loads and sliding rates.

Experimental data are presented concerning the changes in the characteristics of different polymeric electrical insulating compounds after a rather long holding in water and salt solutions at room temperature and 80°C. It has been found that the water absorption level of thermosetting compounds, as well as the worsening of their electrical properties, such as specific bulk electrical resistance and dielectric loss tangent dielectric permittivity under the action of water–salt media, is determined by the chemical nature of these polymers. The prolonged holding of epoxy compounds in salt solution at a normal and at an elevated temperature leads to water absorption lower than 1% and does not exert any significant effect on the electrical characteristics thereof. The holding of polyurethane compounds in a salt solution leads to a more than a twofold increase in water absorption compared to the epoxy compounds and to such a dramatic change in their electrical characteristics that it makes it impossible to use some of these compounds as insulating materials for manufacturing products that are to be exposed to water and water–salt solutions. The low water resistance inherent in polyurethane compounds and other nitrogen-containing polymers can be caused by a low hydrolytic resistance of the C–N bond occurring in the structure thereof. It is shown that water transpenetration through the layer of the SPB-KhP-80 polyurethane elastomer is quite possible.

Reactions of the gas-phase synthesis of lead antimonates were studied. Standard enthalpies of formation and atomization of gaseous PbSbO2 and PbSb2O4 were determined.

The necessary composition and content of fillers of a multicomponent extrudable composition based on an ultrahigh-molecular polyethylene (UHMPE) with specified mechanical and tribotechnical characteristics are determined. For the purpose of effective and operational development of extrudable composites based on an UHMPE, a minimum amount of experimental data and an algorithm for determining the governing parameters (formulations) is used, which give the needed (restrictive) values for the effective characteristics of multicomponent polymer-polymer compositions. This allows one to secure the tribological, mechanical and technological properties required. The limited amount of experimental data for the relation between the effective properties and the formulation required is supplemented by values calculated using the Lagrange interpolation polynomial. The relations obtained are represented as surfaces and the corresponding level lines. The imposition of level lines allows one to determine the area that meets the requirements specified and to find the formulation necessary for it. On the basis of this algorithm, the optimum formulation of a three-component mixture consisting of an UHMPE, a high-density polyethylene grafted with maleic anhydride, and a polypropylene having tribomechanical properties at the level of an UHMPE, but with a melt flow-behavior index suitable for 3D printing by fused deposition modeling, is determined. According to the formulation found, samples were made and tested, and they completely satisfied the properties prescribed.

The microstructure, phase composition, and parameters of α-Ti-based solid solutions in a Ti–6Al–4V alloy obtained by the 3D printing method without cooling and with water cooling of the titanium substrate are investigated using X-ray diffraction analysis, transmission diffraction and scanning electron microscopy, and optical metallography. It is found that water cooling of the substrate reduces the sizes of prior β-grains, increases the volume fraction of the β-phase, and decreases the volume fraction of the α"-phase and the total mean square displacement of atoms in the α-Ti crystal lattice, and also increases the elastic macrostrain of the samples.

The microstructure, mechanical properties, and deformation behavior of wrought and electron beam additive manufactured (EBAM) Ti-6Al-4V samples under scratching were studied. As-received wrought Ti-6Al-4V was subjected to thermal treatment to obtain the samples with microstructure and mechanical characteristics similar to those of the EBAM samples. As a result, both alloys consisted of colonies of α phase laths within prior β phase grains and were characterized by close values of hardness. At the same time, the Young’s modulus of the EBAM samples determined by nanoindentation was lower compared with the wrought samples. It was found that despite the same hardness, the scratch depth of the EBAM samples under loading was substantially smaller than that of the wrought alloy. A mechanism was proposed, which associated the smaller scratch depth of EBAM Ti-6Al-4V with α′→α″ phase transformations that occurred in the contact area during scratching. Ab initio calculations of the atomic structure of V-doped Ti crystallites containing α or α″ phases of titanium were carried out to support the proposed mechanism.

This work studies the rheological properties of aqueous solutions of acrylamide copolymers. The prevailing role of elastic properties over viscous properties in predicting the proppant suspension capacity of the resulting fracturing fluid is shown. Furthermore, the potential of the use of oscillatory rheometry for studying fracturing fluid stability is demonstrated.

The proteome of exhaled breath condensate was analyzed by mass spectrometry before, immediately after the thermoheliox procedure and after a 3 h relaxation. The major part of the proteome remained unchanged and there was no extensive cell destruction

The proteome of exhaled breath condensate was analyzed by mass spectrometry before and immediately after the thermoheliox procedure and after a 3 h relaxation. The major part of the proteome remained unchanged and there was no extensive cell destruction.

Memristive heterostructures, composed of reduced graphene oxide with different degree of reduction, were demonstrated through a simple method of ‘direct electron-beam writing’ on graphene oxide. Irradiation with an electron beam at various doses and accelerating voltages made it possible to define high- and low-conductivity graphene-oxide areas. The electron beam-reduced graphene oxide/graphene oxide heterostructure clearly exhibited a nonlinear behavior and a well-controlled resistive switching characteristic at a low operating-voltage range (

The kinetic features of bimodal gelation in viscous flow fluids, in particular, petroleum products, are analyzed by viscometry. The gelation and densification of petroleum products facilitate the elimination of consequences of their spill. Experimental dependences on the viscosity time of gasoline, kerosene, and winter and summer diesel fuel mixtures with lithium tetralkoxyborate as a gelator are measured. These dependences are found to have a bimodal sigmoidal shape called the dose-response form in scientific publications. A mathematical formula is proposed to describe these bimodal dependences. In accordance with this formula, the gelation process consists of two stages: (1) a reaction of lithium tert-butylate Li–O–C(CH3)3 and trialkoxyborate B(OC8H17)3 with the formation of lithium tetralkoxyborate; (2) a gelation reaction of lithium tetralkoxyborate and hydrocarbons of the mentioned petroleum products. The formula contains a number of fitting parameters, e.g., tinf1 and tinf2 (h) are the onset times of gelation and the formation of a stable gel respectively; h1 and h2 (h–1) are the rate constants of the first and second stages of gelation, and so on. The concentration dependences of gelators on these parameters are determined. Based on these dependences, the conclusions are drawn about the kinetic features of bimodal gelation in viscous flow fluids.

An algorithm for computer design (calculated determination of the composition) of a multicomponent antifriction material is proposed. First, the minimum initial set of composite characteristics is determined experimentally for a number of controlling parameters from tribological and mechanical tests. The subsequent computer-aided design of the material in the form of constructing the corresponding response surfaces in the space of states makes it possible to identify the range of variation of the controlling parameters to provide the specified operational and technological characteristics. This approach is illustrated by the computer-aided design of the material composition (feedstock) in the form of an extrudable polymer composite based on ultra-high molecular weight polyethylene (UHMWPE) for applications in additive technologies. An optimal formulation is proposed for the UHMWPE + n wt % HDPE-g-SMA + n wt % PP ternary mixture that has tribological and mechanical properties at the level of unfilled UHMWPE and, at the same time, the melt flow index required for 3D printing by the fused deposition modeling method.

—The hardness and the tribological properties of the AK10M2N silumin subjected to irradiation by a high-energy pulsed electron beam with an energy density of 35 J/cm2 are studied. As compared to the as-cast state, the microhardness of the surface layers increases by ≈20% (up to ≈1.2 GPa), the friction coefficient decreases by a factor of ≈1.3 (down to 0.42), and the wear parameter decreases by a factor of ≈6.6 (down to 0.74 × 10–3 mm3/(N m)). These changes are shown to be caused by the dissociation of silicon and intermetallic compounds in the surface layer during irradiation by a high-energy pulsed electron beam.

The paper reports on a molecular dynamics simulation of plastic deformation in polycrystalline titanium under scratch testing with explicit account of crystallographic orientations determined by electron backscatter diffraction for individual Ti grains. The simulation shows that the presence of a grain boundary breaks the lattice translation invariance and induces a constrained strain zone in which the deformation changes its dislocation mechanism for rotations such that misoriented local regions appear near the grain boundary. The pattern of consistent dynamic rotations of atoms near the grain boundary is governed by the crystallographic orientation of grains. If the indenter sliding direction coincides with one of the easy slip directions of a loaded grain, the material in the grain boundary region is fragmented and atomic clusters move along the grain boundary plane from the surface deep into the material. The simulation results allow us to explain why the profile of scratches differs depending on the scratching direction.

The resilience of adhesive compounds in water—salt media was shown experimentally to depend on the nature of the bonding surfaces, as well as on the chemical peculiarities of adhesives. Unlike compounds based on epoxy resins and anhydride hardeners, adhesive compounds based on epoxy resins and aliphatic amine hardeners are unsteady in water-salt media. The resilience of systems on the basis of polyurethane adhesives to the water-salt environment is sensitive to the adhesive structure and may vary in a very broad range.

The possibility of using amides of halogen-substituted acetic acids as acyl donors in penicillin acylase-catalyzed reactions has been investigated, and the ability of this group of compounds to inactivate enzymes in the course of the catalytic conversion has been established. The strongest inactivating effect was demonstrated by iodoacetamide and bromoacetamide. However, the negative contribution of this side activity can be minimized by decreasing the temperature, when the rate of acyl donor conversion by penicillin acylases is still high enough, but the impact of enzyme inactivation becomes less significant. The catalytic activity of penicillin acylase from Alcaligenes faecalis in the conversion of 2-haloacetamides was significantly (5-8 times) higher than that of penicillin acylase from Escherichia coli.

Nanofibers of Al2O3 (commercial product Nafen™), which were modified by various silane coupling agents have been used to create hybrid materials based on copolymer of ethylene and propylene. Nanocomposites were obtained by in situ catalytic copolymerization on the rac-Et(2-MeInd)2ZrMe2/isobutylalumoxane system. Trialkoxysilanes with alkenyl (vinyl and octenyl) and alkyl (octyl) functional groups were used for modification. CP MAS NMR analysis (13C and 29Si) of all modified nanoparticles showed the absence of residual alkoxy groups and allowed to identify the type of formed siloxane groups (mainly T2, T3). EDX analysis of trimethoxyalkenylsilanes modified nanoparticles showed significant contribution of self-condensation reactions, otherwise, in the case of triethoxyoctylsilane condensation with surface Al OH groups prevailed. It is found that octylsilane modification leads to remarkable improvement of mechanical properties (tensile strength - approx. 150%, elongation at break - approx. 50% with regard to neat copolymer) at low nanofiller dosage (0.63 wt %), significantly exceeding those for the materials with alkenylsilane treated nanofibers. In the case of octenylsilane even major decline in mechanical performance was observed. We believe that this behavior is determined by the distribution of nanofiller in the polymer matrix, which is markedly different for different surface treatments. TEM observations show that octylsilane modification leads to efficient dispersion of Nafen in polymer matrix, while the use of alkenylsilanes leads to partial or significant aggregation of Nafen particles.

The possibility of growing modified polyvinylidene fluoride (PVDF-2M) films by laser sintering is shown. The effect of laser radiation with a wavelength of 10.6 µm on the polymer structure and the quality of the film sintering is studied.

In this paper we focused on the micromorphology of the Late and Middle Pleistocene paleosols exposed in twelve loess-paleosol sequences sections in the central part of the East European Plain. Each studied paleosol complex known as Mesin (MIS 5), Kamenka (MIS 6 (8) - 7 (9)), and Inzhavino (MIS 8 (10) - 9 (11)) pedocomplexes (PCs) consists typically of two members, the earlier - main - phase of the soil development taking place during an interglacial, and the later one - at the subsequent interstadial time. Interglacial paleosols formation is associated with the thermal optimum of climatic macrocycles and corresponds to conditions close to modern in the territory under consideration. Interstadial paleosols formation characterizes the intervals within the glacial period, accompanied by an increase in heat and moisture. However, the heat supply of such intervals did not reach modern level in this region (Velichko and Morozova 2015). As follows from the analysis of the soil micromorphology over the studied area, the soil microstructure experienced notable changes under changing latitudinal zonality. During the interglacial periods clay coatings and Fe-Mn pedofeatures dominated the soil microfabric; in the south loess-paleosol sequences coatings are in negligible quantities, Fe-Mn pedofeatures decrease in amount, and carbonate pedofeatures appear instead. In the microfabric of the interstadial paleosols, Fe-Mn pedofeatures are abundant, but unlike interglacial paleosols, the coatings are rare. Basically, the coatings are humus-clayey in composition, but in the more southern sections coatings are absent.

The regularities of the effect of the variation in the chemical composition of the new Russian β‑solidifying TiAl-alloy (Ti–44.5 Al–2 V–1 Nb–2 Cr/1 Zr–(0–0.1) Gd, at %) within the chromium content from 1.5 to 2.5 at % (2.0–3.5 wt %) and zirconium from 0.5 to 1.5 at % (1.2–3.5 wt %), as well as the effect of gadolinium microalloying on the phase composition and the structure of ingots, have been studied. The ingots were obtained using double vacuum-arc remelting with the subsequent vacuum-induction melting and pouring of the melt into the steel chill mold at the melting-casting unit with a cold crucible. It is shown that 0.1 at % gadolinium microaddition results in a decrease in the average size of the macro grains from 3000 ± 500 μm to 400 ± 80 μm in the peripheral part of the ingots after the first remelting. It was found that the phase composition of TiAl-alloy compositions with Cr and Zr is represented by three main phases: γ-TiAl, α2-Ti3Al, and β-phase. The volume fraction of β-phase does not exceed 2–3% in ingots containing Zr, while it reaches 5–6% in ingots containing Cr. It was revealed that the microstructure of the ingots of all studied chemical compositions has a lamellar morphology. Sprouting of lamellar colonies through the grain boundaries was noted for ingots containing Zr.

In the manufacture of products instead of unfilled polymers, such as ultra-high-molecular-weight polyethylene (UHMWPE), it is more effective to use composite systems with reinforcing inclusions. The paper discusses the possibility of creating a composition with the given physical and mechanical properties. An approach to the determination of control parameters (phase composition, phase properties) giving the material the specified effective properties or their entry into predetermined intervals is proposed. In accordance with this approach, on the basis of the analysis of experimental data containing information about the effective characteristics depending on the values of the control parameters, the corresponding surfaces of the response of physical and mechanical characteristics to the values of the control parameters are constructed in the state space. The obtained surfaces make it possible to identify the range of control parameters for the given characteristics of multicomponent polymer compositions based on UHMWPE.

In order to develop dispensable materials for additive manufacturing technologies, the structural and functional analysis of antifrictional polymer-polymer blends based on ultrahigh-molecular weight polyethylene (UHMWPE) are performed. The problem of the optimal selection of polymer plasticizers from the commercially available thermoplastic is solved in order to improve the extrudability of UHMWPE. It is shown that the effective plasticizing filler for UHMWPE from the standpoint of maintaining its tribological and mechanical characteristics and providing the required melt flow index is a double mixture of 10 wt % HDPE-g-SMA + 10 wt % PP. Using the developed materials will make it possible to manufacture parts of a complex shape for tribojoints, including endoprostheses, by the 3D printing method.

Using the methods of X-ray diffraction analysis, the concentration-dependent transformation plasticity effect +TPE) is investigated during hydrogenation of the technically pure titanium (VT1-0) irradiated on one side with a low-energy high-current electron beam in a SOLO facility using three 50 μs pulses at the pulse repetition frequency 0.3 s–1 and the beam energy density W = 18 J/cm2. Its irradiation is performed in an argon atmosphere at the residual pressure 0.02 Pa. It is found out that the concentration-dependent TPE in the course of hydrogenation is due to the low stability state of the α-Ti crystal lattice formed in the specimen surface layer upon its e-beam irradiation. Relaxation of the elastic plane macrostresses occurs as a result of the development of concentration inhomogeneity of hydrogen or formation of α″-Ti and ω-Ti martensitic phases.

Background: Chronic rhinosinusitis (CRS) in European country ranges in elderly patients from 4.5 to 12% of population and has a significant effect on quality of life. In these patients, rhinosinusitis is linked to immune functions changes with age and to mucosal paraphysiological alterations such as crusting formations with atrophic epithelium, variations of nasal airflow and modifications of the mucociliary clearance. Failure of medical treatments leads to surgery in patients with persistent symptoms and radiographic signs of CRS. The choice of appropriate post-surgical topic treatments is important for healing time and for preventing mucosal complications such as synechiae, crusting formation and atrophy with secondary bacterial and fungal infections. Aims: Defining the effects of topic alpha-tocopherol acetate administration on nasal mucosa healing after endoscopic sinus surgery in CRS of elderly patients. Methods: In this study were included 32 patients, mean age 68.6, who underwent FESS because affected by CRS not responsive to medical treatments. After surgical treatment, we distinguish two groups basing on local nasal therapy. Results: We investigated, in the postoperative time, the role of alpha-tocopherol acetate compared to gomenol oil. Follow-up was performed at 7–15 days and 1–3 months after surgery. We evaluated mucosal restoration using Rhinoscopy Sum Score and quality of life using Nasal Six Items Symptom Questionnaire. We observed a faster healing time and less recurrence of complications in patients who underwent topic treatment with alpha-tocopherol acetate. Discussion: In our research, we observed that alpha-tocopherol acetate has no contraindications and side effects. Conclusions: Our study showed the effectiveness of alpha-tocopherol acetate topic treatment in elderly patients affected by CRS after FESS, in improving and speeding up the process of restoring the sinonasal mucosa, compared to another topic medication.

Experimental and theoretical studies helped to reveal patterns of surface roughening and the microstructure refinement in the surface layer of commercial pure titanium during ultrasonic impact treatment. Applying transmission electron microscopy technique, a gradient microstructure in the surface layer of the ultrasonically treated sample, where the grain size is varied from nano- to micrometers was revealed. It was shown that the surface plastic strains of the titanium sample proceeded according to the plastic ploughing mechanism, which was accompanied by dislocation sliding, twinning, and the transformations of the microstructure and phase composition. The molecular dynamics method was applied to demonstrate the mechanism of the phase transformations associated with the formation of stacking faults, as well as the reversible displacement of atoms from their sites in the hcp lattice, causing a change in coordination numbers. The role of the electronic subsystem in the development of the strain-induced phase transformations during ultrasonic impact treatment was discussed.

The aim of the paper was to improve the functional properties of composites based on ultra-high molecular weight polyethylene (UHMWPE) by loading with reinforcing fibers. It was achieved by designing the optimal composition for its subsequent use as a feedstock for 3D-printing of guides for roller and plate chains, conveyors, etc. As a result, it was experimentally determined that loading UHMWPE with 17% high density polyethylene grafted with VinylTriMethoxySilane (HDPE-g-VTMS) was able to bind 5% glass fillers of different aspect ratios, thereby determining the optimal mechanical and tribological properties of the composites. Further increasing the content of the glass fillers caused a deterioration in their tribological properties due to insufficient adhesion of the extrudable matrix due to the excessive filler loading. A multi-level approach was implemented to design the high-strength anti-friction ‘UHMWPE+17%HDPE-g-VTMS+12%PP’-based composites using computer-aided algorithms. This resulted in the determination of the main parameters that provided their predefined mechanical and tribological properties and enabled the assessment of the possible load-speed conditions for their operation in friction units. The uniform distribution of the fillers in the matrix, the pattern of the formed supermolecular structure and, as a consequence, the mechanical and tribological properties of the composites were achieved by optimizing the values of the main control parameters (the number of processing passes in the extruder and the aspect ratio of the glass fillers).

Modification of the composition of grain storage proteins is an intensively developing area of plant biotechnology, which is of particular importance for sorghum – high-yielding drought tolerant crop. Compared to other cereals, the majority of sorghum cultivars and hybrids are characterized by reduced nutritional value that is caused by a low content of essential amino acids in the seed storage proteins (kafirins), and resistance of kafirins to protease digestion. RNA interference (RNAi) by suppressing synthesis of individual kafirin subclasses may be an effective approach to solve this problem. In this chapter, we review published reports on RNAi silencing of the kafirin-encoding genes. In addition, we present new experimental data on phenotypic effects of RNAi-silencing of γ-KAFIRIN-1 gene in sorghum cv. Avans. To obtain RNAi mutants with γ-KAFIRIN-1 gene silencing we used Agrobacterium-mediated genetic transformation. Transgenic kernels had modified endosperm type with reduced vitreous layer and significantly improved in vitro protein digestibility (93% vs. 57%, according to the densitometry of SDS-PAGE patterns). SDS-PAGE of transgenic kernels showed lowered level of kafirins and appearance of globulin proteins, which were not observed in the original cultivar. For the first time, the cases of instability of inserted genetic construct were identified: elimination of ubi1-intron that is a constituent part of the genetic construct for RNAi silencing, or nos-promotor governing expression of the marker gene (bar) (in the RNAi mutants of cv. Zheltozernoe 10). The research findings presented in this chapter provide strong evidence that RNA interference can be used for improvement of the nutritional properties of sorghum grain.

Particle knockout scattering experiments1,2 are fundamental for mapping the structure of atomic nuclei2–6, but their interpretation is often complicated by initial- and final-state interactions of the incoming and scattered particles1,2,7–9. Such interactions lead to reduction in the scattered particle flux and distort their kinematics. Here we overcome this limitation by measuring the quasi-free scattering of 48 GeV c–1 12C ions from hydrogen. The distribution of single protons is studied by detecting two protons at large angles in coincidence with an intact 11B nucleus. The 11B detection suppresses the otherwise large distortions of reconstructed single-proton distributions induced by initial- and final-state interactions. By further detecting residual 10B and 10Be nuclei, we also identified short-range correlated nucleon–nucleon pairs9–13 and provide direct experimental evidence for separation of the pair wavefunction from that of the residual many-body nuclear system9,14. All measured reactions are well described by theoretical calculations that include no distortions from the initial- and final-state interactions. Our results showcase the ability to study the short-distance structure of short-lived radioactive nuclei at the forthcoming Facility for Antiproton and Ion Research (FAIR)15 and Facility for Rare Isotope Beams (FRIB)16 facilities, which is relevant for understanding the structure and properties of nuclei far from stability and the formation of visible matter in the Universe. Initial- and final-state interactions distort the kinematics in particle knockout scattering experiments, complicating their interpretation. These effects are suppressed by detecting 11B nuclei in quasi-free scattering of 12C ions from hydrogen.