Structure Formation Processes Research Articles

Https://doi.org/10.47191/ijcsrr/V6-i2-09

The results of physical and chemical studies of the processes of hydration and structure formation during hardening of pozzolanic cements containing dry–selection ash and slag waste from the Angren TPP as an active mineral additive are presented. It has been established that, despite the replacement of up to 50% of the clinker part, the experimental cements acquire high hydraulic activity, which ensures their grade 400–500, which is facilitated by the presence of active silica, alumina and low–basic calcium silicates in the composition of the additive, which in the process of chemical interaction with hydration products clinker minerals are involved in the formation of a dense microstructure of the cement composite.

Large-scale ecologically-based farming systems foster earthworm communities and their contribution to ecosystem processes

In the Pampean region of Argentina, large-scale ecologically-based farming systems (EBS) are proposed as a more sustainable alternative to the conventional systems (CS). EBS rely on soil biological functioning, where earthworms are essential by their contribution to ecosystem processes such as nutrient cycling and soil aggregation. Our aim was to assess the effect of EBS, compared to CS and undisturbed grasslands (GS), on earthworm communities and their contribution to the process of soil structure formation, evaluated through direct sorting and quantification of earthworm casts. EBS and GS had similar earthworm richness and abundance, in both cases significantly higher than in CS. Earthworm biomass was higher in GS than in both farming systems and higher in EBS than in CS. Cast production was higher in EBS compared to CS, and similar in EBS and GS. Cast production was linearly related to earthworm abundance and to a greater extent to earthworm biomass. We conclude, in the first direct assessment of earthworm contribution to soil structure formation in EBS of the Pampean region, that this farming system provides better conditions for earthworm development compared to CS, enhancing their role in the soil ecosystem processes. Thus, we confirmed the ability of EBS to increase soil biological fertility replacing chemical inputs by ecosystem processes thus achieving more resilient and sustainable farming systems.

On the Influence of High Pressures and Boron Nitride on the Processes of Structure Formation and Microhardness of a High-Entropy Equiatomic Composition AlNiCoFeCr Alloy

On the Influence of High Pressures and Boron Nitride on the Processes of Structure Formation and Microhardness of a High-Entropy Equiatomic Composition AlNiCoFeCr Alloy

Structure formation processes in fullerene mixtures

Glass formation processes in condensed matter are characterized by some specific short-range order changes in the arrangement of particles (atoms/molecules/ions). So, the short-range structural order in supercooled liquids and glasses is characterized by fivefold symmetry in the arrangement of particles, often referred to as icosahedral (ideal or distorted) short-range order. This article is devoted to the study of local structural features of the supercooled melt of the A20B80 fullerene mixture (where A = C60 and B = C70) obtained under various cooling protocols in order to elucidate the mechanism of formation of the icosahedral short-range order in binary molecular liquids. Comprehensive studies of the properties of a fullerene mixture melt were carried out using large-scale molecular dynamics simulations followed by structural and cluster analysis. The crystallization temperature and the critical glass transition temperature of the system were calculated to be T_m~1439 K and T_c~1238 K, respectively. It has been established that the crystallization of a binary fullerene mixture proceeds according to the polycrystalline scenario with the formation of clusters with fcc and hcp symmetries. It is shown that in a supercooled fullerene mixture, the short-range icosahedral order is formed by an insignificant number of ideal icosahedral clusters and a certain set of distorted icosahedral clusters, the fraction of which remains practically unchanged at temperatures below the critical glass transition temperature. Keywords: molecular dynamics, fullerenes, short-range order, structural ordering.

Study of the hygrometric condition of cement stone and concrete

Cement systems are thermodynamically non-equilibrium, non-linear systems. Since it is far from equilibrium, it must be characterised by structure formation processes. Here it is necessary to consider the definition of ‘structure formation’. This term is used in two meanings. The first is generally accepted in concrete science -the formation of mechanical bonds between the dispersed particles of a solidifying system as a result of ongoing chemical and physicochemical processes, culminating in the formation of a solid body -the cement stone and concrete. The second meaning of the term describes the emergence of dissipative structures, i.e. the destruction of the initial homogeneity of the system due to the emergence of streams, concentration gradients, chemical waves, etc. By measuring the parameters of the resulting dissipative structures of different formation methods, it is possible to assess the degree of disequilibrium in the solidifying system and hence the directed methods of structure formation and structure optimisation. It should also be noted that a non-linear, non-equilibrium hydration process leading to a concentration potential difference proceeds with equal probability in all directions. Applying a gradient of a high-intensity physical field to the disperse system, one should expect a synchronisation of the fluctuations of the concentration potential of local areas of the disperse system, which will result in a sharp increase of the physical and mechanical properties of the hydration products of the binder and of the concrete in general.

Temperature-Rate Conditions of Deformation and Structure-Forming Processes in Nickel during High-Pressure Torsion

Temperature-Rate Conditions of Deformation and Structure-Forming Processes in Nickel during High-Pressure Torsion

Temperature-Rate Conditions of Deformation and Structure-Forming Processes in Nickel during High-Pressure Torsion

Scanning and transmission electron microscopy has been used to investigate the nickel structure formed by high pressure torsion deformation at temperatures of 100–250°C. The relationship between the structure and temperature–rate conditions of deformation, which is characterized by the Zener–Hollomon parameter (Z), has been found. A change in the temperature–rate conditions of deformation has been shown to alter the dominant structure-forming process and to change the resultant structure. We have identified lnZ ranges where these processes occurred, namely, dynamic recovery at lnZ 25, dynamic recrystallization at 21 lnZ 25, and dynamic polygonization at lnZ 21.

Structure formation of hyper-compacted and modified concrete

Production of axisymmetric products -pressure and non-pressure pipes, rings, wells, bridges and drainage elements represents one of the main branches of construction industry in water and wastewater industry of Uzbekistan and Central Asian republics. However, positive tendencies of its development are only emerging and still do not meet the potential of progressive, competitive and economical modern technology, capable of providing significant shifts in reduction of resource intensity of new products, expansion of raw material base of construction industry and involvement of technogenic products into its balance, as well as solution of important economic and environmental problems. Prospects for further development of high-efficiency tubular goods production and scientific and technological progress of their production are largely determined by the importance of regularities and methods of controlling technological processes of structure formation with regard to given high level of product quality and criteria of resource intensity of production. In this regard, the analysis of general regularities of material structure formation in the complex process of hypercompaction and cementations modification in axisymmetric concrete is of primary importance.

Expanding of the, food industry participation in foreign economic activity of the food complex

The processes of structure formation of agricultural products exports by three main components - primary products, finished products and processed products are analyzed. It is established that in 2009-2021 the volume of exports increased almost three times, but the primary production - more than three times, finished - less than three times, processed - almost twice. The different rates of growth of exports of various components of agricultural products led to the fact that the share of primary production in the structure of exports increased slightly and amounted to more than half, the other two groups - decreased, of which the share of processed products - one and a half times. The strategy for the exports development of agricultural products for the period up to 2026 provides for bringing the proportions of components (primary / finished / processed) to 39/40/21, but last year we have 54/39/7. In order to ensure the achievement of the planned indicators, it is necessary to carry out innovative and technological modernization of processing facilities of the food industry, complete the implementation of permanent safety procedures based on HACCP principles in primary production, ensure strict compliance with regulations primary products, etc.

Influence of bed ash on the rheology and properties of gypsum building mixtures

In the article, the influence of the aluminosilicate part of fuel bottom ash and slag mixtures on the water demand of gypsum raw materials of dry building mixtures is considered. It is shown that the aluminosilicate filler has a plasticizing effect. This is due to the presence of microspheres in the composition of the filler. They reduce the amount of water needed to achieve normal gypsum paste consistency. This is reflected in other physical, mechanical and structural characteristics of gypsum. The ash filler in the optimal ratio with the gypsum binder compacts the structure of the stone. does not participate in chemical transformations. To increase the efficiency of the ash filler, it is necessary to introduce additional components that activate the processes of structure formation in ash-gypsum binders.

НЕРУЙНІВНІ МЕТОДИ КОНТРОЛЮ ПРОЦЕСІВ ТУЖАВЛЕННЯ І ТВЕРДІННЯ БУДІВЕЛЬНИХ КОМПОЗИЦІЙНИХ МАТЕРІАЛІВ ІЗ КРУПНИМ НАПОВНЮВАЧЕМ

The article deals with the problem of non-destructive control of the processes of setting and hardening of composite materials, for which coarse filler granules or mixtures of fillers of different granulometric composition are used. Since the use of standardized penetration methods in the cases under consideration becomes impossible, it is possible to draw conclusions about the stages of the processes of structure formation of a composite binder dough only by indirect signs. In such a study, methods are preferable that least disturb the structure of the hardening composite, up to non-contact ones. The article provides a comparative description of several such methods. Two of them are based on the measurement of electrical responses associ-ated with structure formation, the other two are based on the study of exothermic processes and, accordingly, the propagation velocity of ultrasonic pulses in a hardening binder dough. For a typical sample of the studied material, the time dependences of the corresponding physical characteristics are constructed. Qualitative changes in the course of these curves are comparedwith the boundaries of the stages of the structure formation process. The main qualitative changes in the time dependences of physical properties are interpreted from the standpoint of structural transformations occurring in the material. The measure-ment results are considered both from a theoretical standpoint, related to the interpretation of changes in the structure and properties of the hardening binder dough, and from an applied standpoint, focused on determining the setting time of the material, which is important for the technology of its application. Changes in physical characteristics are reduced to a single scale, which improves the accuracy of determining the setting time. It is shown that the main method, adequate to the problemunder consideration, is conveniently taken to be ultrasonic, which makes it possible to effectively display both the beginning and the end of setting. The remaining methods seem to be complementary, allowing a more thorough study of the processes during the completion of the setting. The considered research methods are also applicable to conventional materials, and some of them, with minimal modification, to hardening samples and products in the practice of building production.

Деякі аспекти використання сталей під час позареакторного зберігання та транспортування відпрацьованого ядерного палива. (Огляд)

In the world, the nuclear industry is considered an ideal option for an environmentally friendly source of energy generation, based on the separation of the radioactive nuclide of the chemical element 235U. When generating electricity from nuclear power plants, the main disadvantage is the generation of radioactive waste. After spent fuel is removed from a nuclear reactor, it is placed in special containers containing absorption and retention elements. It is obvious that the storage and transportation of spent nuclear fuel plays an important role in the development and overall safety of the nuclear industry, and high-quality neutron-absorbing materials are the basis for the successful manufacture of reliable structures and containers. The development of modern neutron absorption materials ensures reliability, safety, storage duration, as well as reducing the cost of logistics operations associated with the transportation of radioactive waste. Based on the results of the analysis of scientific and technical sources, modern ideas about materials for the manufacture of containers, which are used for storage and transportation of nuclear fuel waste, are summarized. The advantages and disadvantages of the main materials used in the disposal of spent nuclear fuel are considered. It has been established that, from an economic point of view, the most rational material for storing and transporting radioactive waste is ferritic stainless steel with a high boron content, which, in addition to absorption abilities, is characterized by other properties required for this type of product. Since boron has a low ability to dissolve in both austenite and ferrite, this leads to the formation of borides of various types, which contribute to the embrittlement of the structural material. At the same time, the distribution of borides over the volume of a metal product is determined not only by a set of properties, but also by the protective properties of the material, as well as the manufacturability of the final product from it. Despite the fact that boron-containing steels of the ferritic class have been known for a long time, issues related to the processes of structure formation, increasing technological and operational properties still remain insufficiently studied and controversial. There is also no information on the influence of heat treatment on the formation of the structure and mechanical properties of finished products made of ferritic stainless steels. Successful solution of these scientific and technical problems will ensure the production of modern high-quality neutron-absorbing containers for off-reactor storage and transportation of spent nuclear fuel.

About the processes of hydration and hardening of cement

The paper deals with some poorly studied issues of cement hydration and hardening. It is shown that the interaction of cement with water begins with the attack of oxygen atoms of clinker minerals by water protons. In this case, the process of structure formation of a cement stone can be represented as a process of inversion of the dispersed cement – water system, when the dispersion medium (water) in the initial periods turns into a dispersed phase at the later stages of hardening. Conversely, the dispersed medium (cement) becomes the dispersion medium. Attention is drawn to the relevance, but insufficient knowledge of information interactions in the cement – water system, as well as the influence of a hydrated electron on the reactivity of the system under consideration.

Study of structure formation processes in matrices of mixed components with reinforcing natural fillers

The article presents the results of a study on the development of compositions of heterocomposite materials based on natural dispersed and reinforcing fillers. Using the mechano-chemical modification method, structures were obtained that ensure the compatibility of elements of heterocomposites at the interfacial level at the interface of complex phases where components of different nature and composition are present. By studying the wetting process of the reinforcing filler - spruce fiber obtained from waste, the concentration of the chemical modifier was selected. It has been established that the activity of charged particles of mineral dispersed filler mechanically activated by an unconventional method, crushed with natural stones, lasts for 10-12 hours, which makes it possible to provide time for the maximum use of activity in the formation of stable structures.

Ethylene-Vinyl Acetate Copolymers as Potential Thermoplastic Modifiers of Photopolymer Compositions.

The possibility of using thermoplastic polymers in photopolymer compositions for SLA and DLP is discussed in this article. The diffusion and mutual solubility of uncured systems based on tert-butyl acrylate (tBA) and ethylene-vinyl acetate copolymers (EVA) or low-density polyethylene (LDPE) were studied. The solubility and diffusion of tBA with EVA containing 7, 20, and 40 wt.% vinyl acetate (VA) and with LDPE in the temperature range 20-75 °C were studied by optical micro-interferometry method. Phase diagrams of LDPE-tBA, EVA-7-tBA, and EVA-20-tBA systems were obtained. It is shown that the compositions are characterized by the phase-state diagrams of amorphous separation with the upper critical solution temperature (UCST). The concentration dependences of the interdiffusion coefficients as well as dependences of the self-diffusion coefficients on VA content and on temperature were plotted. The activation energy of self-diffusion of EVA and LDPE was calculated. It was shown that the most promising tBA modifier is EVA-40, which is completely soluble at all studied temperature ranges. The obtained data on the mixing of the initial components is valuable for further studies of the processes of structure formation during photocuring of compositions, regulation of the phase structure and, as a consequence, the performance characteristics of the 3D printable materials.

Emulsion imaging of a DNA nanostar condensate phase diagram reveals valence and electrostatic effects.

Liquid-liquid phase separation (LLPS) in macromolecular solutions (e.g., coacervation) is relevant both to technology and to the process of mesoscale structure formation in cells. The LLPS process is characterized by a phase diagram, i.e., binodal lines in the temperature/concentration plane, which must be quantified to predict the system's behavior. Experimentally, this can be difficult due to complications in handling the dense macromolecular phase. Here, we develop a method for accurately quantifying the phase diagram without direct handling: We confine the sample within micron-scale, water-in-oil emulsion droplets and then use precision fluorescent imaging to measure the volume fraction of the condensate within the droplet. We find that this volume fraction grows linearly with macromolecule concentration; thus, by applying the lever rule, we can directly extract the dense and dilute binodal concentrations. We use this approach to study a model LLPS system of self-assembled, fixed-valence DNA particles termed nanostars (NSs). We find that temperature/concentration phase diagrams of NSs display, with certain exceptions, a larger co-existence regime upon increasing salt or valence, in line with expectations. Aspects of the measured phase behavior validate recent predictions that account for the role of valence in modulating the connectivity of the condensed phase. Generally, our results on NS phase diagrams give fundamental insight into limited-valence phase separation, while the method we have developed will likely be useful in the study of other LLPS systems.

Особенности формирования структуры спеченных порошковых материалов с использованием отходов металлообработки стальных заготовок

Introduction. Manufacturing processes, to one degree or another, are associated with the metal waste production in the form of metal chips. The development of technologies for recycling of waste from mechanical facilities is a popular solution both from the resource saving and from an environmental points of view. Among many traditional approaches to the problem of recycling metal chips, the most interesting may be the method of using chips as one of the components in a powder material. The aim of this work is to analyze the possibility of using metalworking wastes from steel 45 (metal chips) in powder compositions based on titanium and aluminum not only as a source of iron, but also as a possible source of Fe2O3 oxide. Attention to the oxide was paid in terms of initiating reduction reactions in the powder mixture based on titanium and aluminum with the formation of the Al2O3 oxide phase to obtain a metal matrix composite. Research methods: steel chips after processing workpieces from steel 45 were additionally oxidized in water and crushed in a vibrating mill to an average particle size of 300 μm for use in powder compositions with titanium and aluminum powders. Grinded and oxidized chips were mixed with titanium and aluminum powders in various proportions in order to study its interaction with these powder components. The obtained mixtures were pressed in the form of cylindrical samples and sintered in a vacuum furnace at a temperature of 1,000 °C. The phase composition and microstructure were studied using an XRD-6000 X-ray diffractometer with CuKα – radiation and an AXIOVERT-200MAT optical microscope. Results and discussions. It is shown that after milling without coolant, steel 45 chips did not accumulate a noticeable amount of iron oxides, which required additional oxidizing procedures. The interaction of grinded oxidized chips with the components of powder mixtures is considered, and its effect on volumetric changes in compacts and structure formation of metal-matrix composites is shown. The results of optical metallography and X-ray diffraction analysis (XRD) of sintered powder compositions using oxidized ground chips of steel 45 made it possible to evaluate the ongoing processes of structure formation depending on the combination of interacting components, its mutual influence, and the prospects for obtaining composites with a dispersed oxide phase.

Innovative methods of restoration by bac-teria, which secrete calcium, overgrowing microcracks

Innovative building materials are considered, allowing the use of new design solutions and the construction of durable structures that meet technical requirements and aesthetic requirements. The main properties, characteristics, objects and methods of application of hydraulic concrete and self-healing concrete are described. Self–healing concrete is a new stage in the development of building materials. The new self-healing concrete differs from classical recipes by adding fungi and bacterial spores to the composition, which can survive in alkaline conditions and give new properties to the building material. From the analysis of literary sources, we came to the conclusion that the long-term operation of various hydraulic structures is affected by water and the environment. All these factors lead to a decrease in the structural strength of hydraulic structures. A new self-healing material is needed in places where the production of minor repairs and regular inspection of the condition of structures is impossible: underground construction; underwater construction; high-rise buildings; bridge-type transport structures. Another advantage of new generation building materials is the possibility of budget savings, since there is no need for constant minor repairs of structures. The purpose of this work is the research and development of technology for the production of self-healing concrete modified with a micro-biological additive. In accordance with the goal, we analyzed the physical and mechanical properties of concrete and other cement composites, ways to improve them, studied damages and defects that reduce the durability of reinforced concrete structures, the process of structure formation, as well as ways to repair and restore them. Based on the analysis, a technology for creating industrial-scale concrete modified with a microbiological additive and self-healing structures is proposed. This area of research is very promising; the potential profit from the use of such concretes in hydraulic structures is huge.

A Demonstration Bench for Representing the Character of Phase Transitions of the First and Second Kind

The paper presents the description of a demonstration bench, which includes a mathematical model and analysis tools for understanding the features of phase transitions of the first and second kind. The advantage of this demonstration bench is the rejection of all phenomenology and the obvious limitation of the application of various approximations and hypotheses. The description is formed on the well-known equations of hydrodynamics, which are well-tested and are a reliable basis for the construction of realistic models. The Proctor-Sivashinsky model, which was used to describe the process of convection development in a thin layer of liquid with poorly conductive heat boundaries, is the basis for the demonstration bench. Exactly this model allows to observe phase transitions of the first and second kind. The feature of the model is that it allocates one spatial scale of interaction, leaving for the evolution of the system the possibility to choose the nature of symmetry. All spatial disturbances of the same size but of different orientation interact with each other. This allows us not to distract from the main task of this work, which is to demonstrate the process of structure formation as a result of a cascade of phase transitions. The mechanism of phase transitions associated with the presence of minimums of the interaction coefficients of modes of the spectrum of the instability. There are a large number of structural defects, which appear as attributes of phase transition. The instability spectrum modes interference is the reason of the high rate of correlations in the propagation of a new phase.

Structure and solidification of the (Fe0.75B0.15Si0.1)100-xTax (x=0–2) melts: Experiment and machine learning

Fe–B–Si system is a matrix for synthesis of new functional materials with exceptional magnetic and mechanical properties. Progress in this area is associated with the search for optimal doping conditions. This theoretical and experimental study is aimed to address the influence of Ta alloying on the structure of undercooled (Fe0.75B0.15Si0.1)100-xTax (x = 0–2) melts, their undercoolability and the processes of structure formation during solidification. Small concentration of Ta complicates standard ab initio and machine learning investigations. We developed a technique for fast and stable training of machine learning interatomic potential (MLIP) in this case and uncovered the structure of undercooled (Fe0.75B0.15Si0.1)100-xTax (х = 0–2) melts. Molecular dynamic simulations with MLIP showed that at Ta concentration of 1 at.% there is a sharp change in the chemical short-range ordering in the melt associated with a change in the interaction of Ta atoms. This effect leads to a restructuring of the cluster formation in the system. At the same time, our experimental investigation shows that melts with a Ta content of 1 at.% have the greatest tendency to undercoolability. Alloying with Ta promotes the formation of primary crystals of Fe2B, and at a concentration of more than 1.5 at.% Ta, also of FeTaB. Herewith, near 1 at.% Ta, the crystallization of the melt proceeds nontrivially: with the formation of two intermediate metastable phases Fe3B and Fe2Ta Laves phase. Also, the highest tendency to amorphization under conditions of quick quenching is exhibited by a melt with a Ta concentration of 1 at.%. The results not only provide understanding of optimal alloying of Fe–B–Si materials but also promote a machine learning method for numerical design of metallic alloys with a small dopant concentration.