Modern Materials Science Research Articles

Deformation strengthening mechanisms of rails in extremely long-term operation

The quantitative estimation of strengthening mechanisms of rails’ surface layer is carried out on the basis of regularities and formation mechanisms of structure-phase states revealed by the methods of modern physical materials science. It is performed at different depth of rail head along central axis and fillet of differentially quenched 100-m rails after extremely long-term operation (gross passed tonnage of 1411 mln. tons). The contributions caused by the matrix lattice friction, intraphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution strengthening of pearlite component of steel structure were estimated. It is shown that in the surface layer the main mechanism of strengthening is due to the interaction of moving dislocations with low-angle boundaries of nanometer dimensional fragments and subgrains. In a near-surface layer at a depth of 2–10 mm the main dislocation strengthening mechanism is due to interaction of moving dislocations with immobile ones.

60 Years of physica status solidi

60 Years of <i>physica status solidi</i>

Regimes of mass transfer in a 2D crystal in nonequilibrium states

A variety of new technologies associated with the severe impact on materials have been developed recently. The promotion of these technologies is, in turn, associated with the stability of the structure and properties of materials under nonequilibrium conditions. It is well known that under such conditions new mechanisms of structure evolution can occur. The study of these mechanisms is an important task of modern materials science. In our work,a we present the results of an analysis of possible scenarios of impact induced mass transfer in a two-dimensional crystal with a Morse interaction potential including a topological compression soliton, a acrowdion complex and a moving vacancy – a voidion. The influence of the initial impact energy distribution is analysed. The obtained results contribute to the fundamental understanding of mass transfer processes under nonequilibrium conditions.

Influence of the chemical composition of cast iron on the tem-perature of loss of magnetic properties when heating by high-frequency currents

One of the important tasks of modern materials science concerning technical issues is the need to ensure the surface properties of hardened products. An increase in the resource of machines and an increase in reliability are limited by the wear resistance of their components and assemblies: the less wear of the main rubbing pairs, the longer the service life [1]. For example, according to [1], a piston internal combustion engine accounts for 36-52% of the total number of machine failures. Modern technologies have a large number of hardening methods that can increase almost any characteristic of the structural strength of the material. Surface hardening of parts can be carried out in two ways - by changing (modifying) the state of the surface layer or by coating.

Hardening mechanisms for rails metal during long-term operation

A quantitative comparative analysis of the mechanisms of hardening of the surface layers of differentially hardened 100-m rails is carried out. It was based on structure formation, phase composition, defect substructure regularities revealed by the methods of modern physical materials science. The studies were carried out at different depths of up to 10 mm in the rail head along the central axis and along the axis of symmetry of the fillet in the initial state and after various periods of extremely long-term operation (passed tonnage of 691.8 and 1411 mln. tons brutto). The contributions due to the friction of the matrix lattice, interphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution hardening of the pearlite component of the steel structure are estimated.

Progress in Modern Marine Biomaterials Research.

The growing demand for new, sophisticated, multifunctional materials has brought natural structural composites into focus, since they underwent a substantial optimization during long evolutionary selection pressure and adaptation processes. Marine biological materials are the most important sources of both inspiration for biomimetics and of raw materials for practical applications in technology and biomedicine. The use of marine natural products as multifunctional biomaterials is currently undergoing a renaissance in the modern materials science. The diversity of marine biomaterials, their forms and fields of application are highlighted in this review. We will discuss the challenges, solutions, and future directions of modern marine biomaterialogy using a thorough analysis of scientific sources over the past ten years.

Antimicrobial Activities of Metal Containing Compounds and Hybrids.

Normally, antibiotics are used for the growth inhibition of a variety of pathogens. The ever- increasing resistance of the various disease-causing pathogens to the antibiotics has drawn tremendous attention of researchers to find efficient alternatives. The recent era of modern material science and nanotechnology has made it possible to replace the existing antibiotics up to some extent. Currently, a vast library of materials has been prepared, which shows excellent performance against pathogens. Such materials consist of certain metals. Through this review, we present some notable studies concerning the antimicrobial activities of various metal containing compounds and their mode of action.

On the effect of plasma electrolytic oxidation on the fatigue strength of V96Ts1 (Al-Zn-Mg-Cu) aluminum alloy

One of the tasks of modern material science is to obtain new functional high-strength resistant coatings on structural materials like aluminum alloys. This paper shows the effect of plasma electrolytic oxidation (PEO) on the fatigue strength of V96Ts1 (Al-Zn-Mg-Cu) aluminum alloy. Fatigue tests were carried out with uniaxial loading in accordance with the harmonic law with a constant stress of 205 MPa. The modification of the PEO-coated surface layer led to a 5-fold decrease in the cyclic durability of the V96Ts1 alloy. The dependencies of the temperature of dissipative heating and the accumulated strain on the amplitude of the effective load were obtained for the inelastic cyclic strain of V96Ts alloy samples, with and without a PEO-coated surface layer. These dependencies describing material degradation correlate with the data of the fatigue tests. A fractographic analysis of the destroyed samples was also performed.

Effect of isovalent substitution on the crystal structure and properties of two-slab indates BaLa2−xSmxIn2O7

AbstractExploring the effect of isomorphic substitution of atoms on crystal structure and features of oxide compounds is one of the main tasks of modern materials science. This paper deals with the La/Sm isovalent substitution in a two-slab perovskite-like BaLa2In2O7 structure and its effect on the structural features and magnetic properties of BaLa2−xSmxIn2O7 indates synthesized. A complete characterization including data of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), structural calculations (Rietveld method), second optical harmonic generation of the laser radiation, calculations of valence bond sums (VBS), and magnetic susceptibility data of phases obtained is presented. The existence region of BaLa2−xSmxIn2O7 solid solutions with a two-slab perovskite-like structure (0 ≤ x ≤ 1.8) was established, and their coordinate parameters were refined. The character of barium and RE atoms distribution in BaLa2−xSmxIn2O7 structure has determined, and the correlation between substitution degree of lanthanum atoms and the length of Ln–O2 interblock distance has revealed. The magnetic properties of BaLa2−xSmxIn2O7 were considered in terms of the crystal field effect.

Liquid-phase boriding of high-chromium steel

Using the methods of modern physical materials science, structuralphase states and tribological properties of 12Kh18N10T steel, subjected to electroexplosive alloying with titanium and boron and subsequent electron-beam processing in various modes depending on electron beam energy density, exposure pulse duration and their quantity have been analyzed. It has been established that electroexplosive alloying of steel with titanium and boron leads to formation of surface layer with multiphase submicro-nanocrystalline structure, characterized by presence of micropores, microcracks, and microcraters. Complex processing, combining electroexplosive alloying and subsequent irradiation with high-intensity pulsed electron beam, leads to formation of 60 μm thick multiphase submicro-nanocrystalline surface layer. It is shown that phase composition of surface layer of steel is determined by mass ratio of titanium and boron during electroexplosive alloying. Microhardness of modified layer is defined by relative mass fraction of titanium borides in surface layer and can be more than 18 times higher than microhardness of steel in its initial state (before electroexplosive alloying). Modes of complex processing have been determined at which surface layer containing exclusively titanium borides and intermetallic compounds based on titanium and iron is formed. The maximum (approximately 82 % by weight) titanium boride content is observed when steel is processed at regime with the highest mass of boron powder in the sample (mB = 87.5 mg; mTi /mB = 5.202). With decrease in mass of boron powder, relative content of borides in surface layer of steel decreases. It was found that integrated processing of steel is accompanied by sevenfold increase in microhardness of surface layer, wear resistance of steel increases by more than nine times.

CAN THE FRICTION FORCE BE THE DRIVING FORCE?

Friction is one of the types of interaction between bodies. It occurs when two bodies touch. The forces acting between the surfaces of contacting solids are called dry friction forces. They are always directed tangentially to the touching surfaces and are divided into the forces of friction at rest, sliding and rolling. The friction forces depend on many factors that accompany the movement of bodies in the presence of friction. In this regard, the description of friction forces is possible only with the help of empirically found approximate laws, which are often quite rough. The rest friction force is a variable value, it can change from zero to a certain maximum value. By applying a force to the body that exceeds the maximum resting friction force, we will move the body from its place, and it will begin to move. The article considers examples of motion in which the friction force can be mistakenly interpreted as a driving force. The nature of the forces of friction at rest and rolling is considered from the perspective of modern physical materials science.

ВЛИЯНИЕ РЕЖИМОВ НАПЛАВКИ НА ХАРАКТЕРИСТИКИ ТЕПЛОМАССОПЕРЕНОСА ЭЛЕКТРОДНОГО МЕТАЛЛА, ФОРМИРОВАНИЕ СТРУКТУРЫ И СВОЙСТВ ПОКРЫТИЙ

The peculiarities of structure formation in coatings deposited under conditions of controlled heat and mass transfer with the pulse change of power parameters of the mode are considered. &#x0D; It is shown that as a result of the pulse control of mode power parameters, in a coating there is observed of structural heterogeneity decrease on a coating section at the expense of the decrease of structural constituent dimensions in it that increases considerably of operation properties of strengthened products operated under conditions of low temperatures of the extreme North. The investigations are carried out with the use of the complex of fast processes of heat and mass transfer that ensured high productivity of the investigation process at lower cost of time and material costs. &#x0D; It is recommended for a wide range of experts in the field of modern physical material science, hydrodynamics, chemistry and mechanics of a deformable solid, reliability and technogenic safety, control of fast processes of the formation of permanent connections modified with pulse high-energy impact.

Tailoring \u03c0-conjugation and vibrational modes to steer on-surface synthesis of pentalene-bridged ladder polymers

The development of synthetic strategies to engineer π-conjugated polymers is of paramount importance in modern chemistry and materials science. Here we introduce a synthetic protocol based on the search for specific vibrational modes through an appropriate tailoring of the π-conjugation of the precursors, in order to increase the attempt frequency of a chemical reaction. First, we design a 1D π-conjugated polymer on Au(111), which is based on bisanthene monomers linked by cumulene bridges that tune specific vibrational modes. In a second step, upon further annealing, such vibrational modes steer the twofold cyclization reaction between adjacent bisanthene moieties, which gives rise to a long pentalene-bridged conjugated ladder polymer featuring a low bandgap. In addition, high resolution atomic force microscopy allows us to identify by atomistic insights the resonance form of the polymer, thus confirming the validity of the Glidewell and Lloyd´s rules for aromaticity. This on-surface synthetic strategy may stimulate exploiting previously precluded reactions towards π-conjugated polymers with specific structures and properties.

Assessment of current trends in production of molybdenum, its alloys and molybdenum-containing products

The unique combination of physical and chemical properties of molybdenum, required by modern material science, predetermines the variety of applications of molybdenum-containing alloys and molybdenumcontaining metal products: metallurgy, various-profile mechanical engineering, electro-thermal equipment, as well as the need to systematize and update the scientific and technological information accumulated in molybdenum metallurgy. The purpose of the present work was to evaluate the current state of molybdenum production and application, including such issues as production of molybdenum trioxide, molybdenum and its alloys, industrial range of molybdenum and its alloys products, molybdenum consumption structure, identification of dominant trends and their forecasting in the medium term.Technical and economical information on production and consumption of molybdenum trioxide, molybdenum and its alloys was evaluated and systematized. The existing range of products from molybdenum and its alloys, the structure of world molybdenum consumption were evaluated, dominant trends and forecasts for the nearest period were determined. It was stated, that the main technology of molybdenum production is hydrogen reduction from high purity trioxide (up to 99.9%) in the form of powder followed by its compaction. The main producers of molybdenum are the United States, Chile, China, Peru, Canada and Mexico, which account for more than 90% of world production. In 2018, global consumption of molybdenum was about 262,000 tons, about 20% less than in 2011–2012. Ferromolybdenum is produced in Russia and abroad of various brands with molybdenum content of 50– 70%. Currently, the producers of ferromolybdenum in Russia are Sorsky, Zhireken ferromolybdenum and Nizhnevolzhsky ferroalloy plants. The total production capacity of Russian enterprises is estimated at 8.5 thousand tons of ferromolybdenum per year. Metallurgical enterprises of Russia declare production of 33 different types of intermediate products and final products from molybdenum and its alloys.

Control of high-order photonic band gaps in one-dimensional anodic alumina photonic crystals

Abstract One-dimensional (1D) photonic crystals based on porous anodic alumina are of high practical importance in modern materials science owing to their promising applications in the field of photonics. Although the positions of photonic band gaps can be controlled precisely by electric charge passed during the formation of repeating layers of anodic alumina, the methods for tuning the transmittance and reflectance within the photonic band gaps are limited. Here we demonstrate a simple and highly reproducible method for obtaining 1D anodic alumina photonic crystals with several reflecting layers in the unit cell. A theoretical model for the calculation of the optical properties of the prepared 1D anodic alumina photonic crystals is suggested and used for the design of an anodizing profile. The ability to tune the transmittance and reflectance within high-order photonic band gaps by controlling the position of the reflecting layers in the unit cell of the photonic crystal is demonstrated.

Thermal smearing in DFT calculations: How small is really small? A case of La and Lu atoms adsorbed on graphene

The thermal smearing is an efficient tool to accelerate self-consistent field (SCF) convergence, and therefore widely employed in the modern computational materials science. One of the values most frequently used is 0.005 Ha. However, the fact that its equivalent temperature of 1578.9 K goes far beyond conditions of the very stability for most systems studied in the conventional materials science rises concerns on credibility of the data obtained. In the present report, we studied the effect of variable smearing values on different calculated parameters of selected lanthanide atoms (Ln = La and Lu) interacting with cluster and periodic graphene models, using Perdew-Burke-Ernzerhof (PBE) functional in conjunction with the empirical long-range dispersion correction by Grimme. In the cluster calculations for the La and Lu complexes with the supercoronene model for graphene, only the use of thermal smearing of the order of 10−4 Ha or below (down to Fermi occupancy) can yield convergent total energies, Ln…C interatomic distances, charge and spin of Ln atom, spin density and HOMO-LUMO plots. The results of periodic calculations were less sensitive to the choice of the smearing value. In this case, the smearing values at which convergent results can be obtained for total energies, Ln…C interatomic distances, charge and spin of Ln atom, as well as DOS plots are from 0.00004 to 0.001 Ha. In both cluster and periodic calculations, the value of 0.005 Ha was too high for reliable computed parameters to be obtained.

Сравнительный анализ удерживания производных хинолина различного строения в ОФ ВЭЖХ

The study results of the structure and physicochemical parameters effect of various quinoline derivatives on their retention under conditions of reversed-phase high-performance liquid chromatography are presented. It is shown that since the establishment of the relationship between the structure of a substance and its properties is still one of the most important problems of modern chemistry and materials science, chromatography is a very convenient and effective method for obtaining the information necessary for this. To establish the relationship between the structure and sorption characteristics of substances, on the one hand, the parameters of the electronic structure of sorbate molecules, their hydrophobic properties, quantum-chemical, topological and other physicochemical characteristics of organic compounds are used, as well as various computer programs and computer modeling methods that make it possible to analyze and to compare the numerous data on the chromatographic retention of compounds of various chemical nature, on the other. At the same time, for the final conclusions about the possibility of using the obtained dependences and correlations for assessing and predicting the properties of new compounds, a significant sample of compounds of various compositions is required, with the use of which the corresponding "structure – property" relationships are obtained. By now, reference books and computer databases on the chromatographic retention of organic compounds are known, containing information on a fairly large number of objects. However, these databases usually contain information predominantly about the retention of compounds under gas chromatography conditions. There are practically no corresponding libraries and databases for liquid chromatography, which is primarily due to the variety of liquid chromatographic systems differing both in the nature and composition of stationary phases and eluents, and in the chromatographic conditions. For the conditions of liquid chromatography, the possibility of using such schemes is complicated by the existence of a large number of interactions in the chromatographic system, due, first of all, to the presence of an active eluent. It is shown in this work that heterocyclic compounds are suitable models for these purposes, a feature of which is the possibility of modifying their properties by varying the structure within wide limits. In this work, the influence of the presence of heteroatoms, a change in the position of the same heteroatom in the main heterocyclic fragment, and the presence of functional groups and substituents of various natures on chromatographic retention under RP HPLC conditions were studied.

A study of new phase of elongated shape in granular structure of WС-(Ti,W)С-Со cemented carbide after its solid-phase annealing

The results of the investigations by scanning electron microscopy, Auger spectroscopy and X-ray diffraction of the structure of Т5К10 cemented carbide (WC-(Ti,W)C-10Co group) sintered at 1520 °C before and after its additional heat treatment in vacuum at 1200 °C for 7 h are presented. It was shown that in addition to faceted WC grains, globular (Ti,W)C (γ-phase) grains of equilibrium (ratio Ti:W ~ 1:3) chemical composition for sintering temperature 1520 °C and Co-based layers, new inclusions of elongated shape up to 30 μm wide and up to 200 μm long were revealed in the structure. They are distributed stochastic both singly and in the form of clusters. The new phase contains the chemical elements W, Ti, C in the ratio (wt%) of the average values as 6.26:9.39:84.35, which is described by the stoichiometric formula W2.3TiС2.6. In contrast to the cubic cell of (Ti,W)C solid solution, the new phase has a hexagonal GaSe type crystal cell (quality H) with parameters a = 3.750 nm and c = 15.950 nm. On the surfaces of the new phase there are dispersed grains WС and (Ti,W)С solid solution, the sizes of which are 3–6 times smaller than the sizes of similar grains of the basic structure. The content (4.77%) of C in the dispersed grains of WC and in the same grains of the main structure is less than the calculated one. The cobalt phase in the adjacent surface of the new phase of the basic structure is superseded by W (3.57%) and C (0.85%).The formation of a new phase W2.3ТіС2.6 elongated shape in the structure of the T5K10 cemented carbide for the above annealing conditions cannot be explained by the basics of modern material science of its production.

Effect of mechanical stresses on the domain structure of barium titanate single crystals

This review article summarizes the material of years of research on the impact of mechanical stresses on the domain structure of multiaxhetoelectrics using the example of barium titanium monocrystals. Since the discovery of the ferroelectric properties of barium titanate in 1944, this material has been the subject of comprehensive investigation as the first practically important and perhaps the most famous ferroelectric. The domain structure of barium titanate is sensitive to mechanical stresses arising both from simple uniaxial compression and from point impacts by local mechanical loading. Mechanical stress applied to a ferroelectric crystal may have a significant effect on dielectric and piezoelectric properties. In particular, 90-degree domain switching is possible under the influence of stresses. The most interesting experimental results are obtained in the study of elastoplastic processes in BaTiO 3 originating from local mechanical stresses. The following features are found and studied: development of strained region around the point of application of the load; “internal” 90-degree domain that does not extend to the crystal surfaces and does not close upon other domains; the growth of 90-degree domains under the influence of residual mechanical stresses; growth of cracks along charged 90-degree domain walls. The notions of “ferroplastic effect” (crystal deformation due to the formation of 90-degree ferroelectric domains) and “ferromechanical effect” (crack formation and growth along charged 90-degree domain walls) are introduced. The hypothesis of a significant role of oxygen vacancies in the processes of 90-degree domain reorientation was put forward and experimentally confirmed. In particular, an increase in the concentration of oxygen vacancies by reducing annealing of barium titanate single crystals creates more favorable conditions for the appearance of an "internal" 90-degree domain under local mechanical load. The study of the mechanisms governing the formation of a domain structure in ferroelectric crystals remains an important problem of modern materials science.

Hyperelastic Bone Involving the Washer Method

The research conducted focuses on 3D printing and its application in medical equipment. A recent breakthrough in modern material science was made with the creation of hyperelastic bone. This exploration looks at how hyperelastic bone is created, the cost comparison to older tools, and the possible design for hyperelastic bone. Detailed calculations and descriptions are also included to explain the reasoning behind the work conducted.