The results of the specialists’ and scientists’ researches. Рубрика в журнале - Nanotechnologies in Construction: A Scientific Internet-Journal
Scientific article
Colloidal systems in form of emulsions or suspensions are widely used in various of industries including oil-gas fields development industry. Invert emulsions and suspensions are actively applied in fields development, including enhanced oil recovery, intensification of oil production, drilling and wells workover. Results of laboratory tests for studying physical properties of heterogeneous systems as an emulsion system with nanoparticles and emulsion-suspension system with nanoparticles are presented in this paper. Having unique physical and chemical properties these systems can be effectively applied in upstream of oil and gas as a water-limiting agent or blocking pack with reversible effect. In framework of this research, laboratory tests for evaluation of the influence of the new systems on filtration characteristics of hydraulic fractures are carried out. Laboratory tests are planned in accordance with requirements of international standards and conducted under the closest conditions to subsurface thermal and pressure conditions of formations STyr Abdylovskoe, SBASh Yugomashevskoe and YuS-2 and YuS-4 of Tortasinskoe oil-gas fields. Based on the results, permeability and conductivity indexes of the models of hydraulic fractures before and after filtration of the new types of colloidal systems are calculated. In order to evaluate an efficiency of the new systems and to study a possibility to regulate its blocking properties an analysis of the impact made by a type and a quantity of nanosized solids on to the blocking properties is carried out. An optimal concentration of nanoparticles in the compositions for a range of formation conditions of particular carbonate and sandstone subsurface reservoirs of oil-gas fields of Russian Federation are represented in this paper.
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Fabrication of W nanodot and Nitrogen Co-decorated Carbon Skeleton for Hydrogen Evolution Reaction
Scientific article
Metal dots-nitrogen-carbon catalysts have become a hot topic in recent years because of special coordination environment. Herein, for the study the W nanodots and nitrogen co-decorated carbon skeleton (W@NC) was prepared for hydrogen evolution reaction (HER). In particular, NaCl templates not only restrict the growth of nanodots, but also improve the purity of phase. By optimizing the feeding ratio of ammonium metatungstate, W nanodots (the size is about 1.2 ± 0.6 nm) dispersed well on N-doped C skeleton, and this special structure could effectively promote electron transfer and ion diffusion during HER process. As a result, the optimized W@NC hybrids exhibited excellent HER performance in alkaline media with a rather low over-potential (228 mV at 10 mA cm–2) and outstanding durability over 10 h.
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Fine-grained concrete with recycled polyvinyl chloride fiber
Scientific article
Introduction. Polymer fiber is widely used in the production of structural concrete components, in shotcrete for tunnels, concrete slabs, blast-resistant concrete, and solid road pavements. Recently, numerous studies have been devoted to the use of fibers derived from recycled polymers in fiber-reinforced concrete. Most of these studies address the effect of fiber on the compressive, flexural and tensile strength properties of concrete. Fibers of various lengths based on nylon, aramid, polyester, polyethylene terephthalate, polypropylene, polyvinyl alcohol, and polyvinyl chloride are used in concrete. However, the insufficient amount of data, or its complete absence, regarding the effect on the properties of concrete with polymer fibers based on recycled PVC necessitates further research, which is particularly relevant given the generation of significant volumes of PVC waste during the production of plastic windows. Materials and methods. The electron microscopy and thermomechanical analyses (TMA) were used to investigate the properties of PVC-based polymer fibers. The effect of the polymer fiber on properties of fine-grained concrete mixtures and hardened concrete, the standard testing methods were used, including the determination of workability by flow table test diameter on a vibrating plate, the average density of concrete mixtures and concrete, and tensile strength under flexural and compressive loading. Results. It is shown the positive effect of the grinding process determined by electron microscopy, which produces a rough surface and fibers of 2.5–4 cm in length, 1.75–4 mm in width, and 0.2–0.3 mm in thickness. It is established that the PVC-based fiber belongs to amorphous polymers of linear structure with a crystallization temperature of 86.4 °C and a destruction temperature of 208.91 °C. It is determined that the optimal fiber content in concrete does not impair the workability of concrete mixtures or affect their cohesion. It is shown that the addition of PVC-based fiber to fine-grained concrete in amount up to 1.2% increases the concrete density of 1.6 times, increases flexural tensile strength by 22%, and has no effect on compressive strength. Conclusion. Conducted studies confirm the feasibility of using polyvinyl chloride-based fiber as a component of fine-grained concretes. However, there is the lack of sufficient data of fiber introduction method in concrete which requires additional scientific research to prevent fiber clumping, establish its compatibility with chemical additives added to the concrete mixture and the effect of curing conditions.
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High-viscosity nanoemulsions of petroleum products in a sand matrix: problems and solutions
Scientific article
Introduction. Oil spills on sandy shores lead to the formation of stable emulsions that are difficult to eliminate. The research is aimed at a comprehensive analysis of the physical and chemical properties of such an emulsion and the development of effective methods for its separation using modern chemical and technological approaches that have aspects of nanolevel interaction at the phase boundary. Methods and materials. The object of the study was a sample of contaminated soil. Visual inspection was performed; density and dynamic viscosity were determined in the range of 25–90 °C. The separation of the emulsion was tested by centrifugation (including the use of a demulgator) and water distillation (Dean-Stark method). The content of mechanical impurities was determined gravimetrically, and their composition was determined using Fourier transform IR spectrometry. For demulsification and viscosity reduction, dilution with diesel fuel and solvent was used, followed by centrifugation. Results and discussion. The sample was a highly viscous (105 379 MPa•s at 25 °C) emulsion that could not be separated by standard centrifugation. The content of water (33%) and mechanical impurities (23.8%) identified as sand (SiO2) was determined. The high stability of the emulsion is probably due to the formation of strong interfacial layers. Dilution of the sample with diesel fuel and Nefras-C280 in a 1:1 ratio significantly reduced the viscosity and achieved effective separation into the oil phase and mechanical impurities during subsequent centrifugation. Conclusion. It is shown that traditional methods of emulsion destruction are ineffective without preliminary modification of the system. The most effective strategy is chemical dilution followed by thermomechanical treatment, which disrupts the stable nanostructure of the emulsion and facilitates separation. The data obtained are important for developing practical recipes for oil spill response in coastal areas.
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Scientific article
Introduction. This study is part of a broader investigation into the phenomenon of delayed ettringite formation (DEF) in concrete and its consequences on the durability of concrete–mortar systems. The objective of the research is to analyze the influence of the initial thermal conditions of fresh concrete on the development of internal sulfate reaction (ISR), the mechanical properties of concrete, and the behavior of mortar applied to the surface after hardening. Materials and Methods. Three concrete mixtures, designated BP1, BP2, and BP3, were produced and subjected to DEF testing on cubic specimens, including continuous temperature monitoring. The temperature of fresh concrete was intentionally varied in order to evaluate its influence. The experimental program was carried out in Africa, specifically in Benin. Compressive and tensile strength tests were performed. After verifying that the concrete was suitable, mortar was applied to the concrete surface. The behavior of the mortar was then monitored over a period of 90 days through visual observation of the mortar surface. It was particularly interesting to observe the evolution of the mortar surface over time. Results and Discussion. The results has shown that for concretes BP1 and BP2, when the initial temperature was below 35 °C, the thermal behavior during the DEF test was stable, and the maximum temperature did not exceed 80 °C. Under such conditions, appropriate mechanical properties and a uniform coating of mortar were obtained without any visible cracking or surface damage. Nevertheless, for concrete BP3 with initial temperature higher than 35 °C, the thermal behavior became unstable, but the maximum temperature remained lower than the critical one. It was observed that this instability negatively affected the mechanical properties and reduced the durability performance of the material. Conclusion. The control of the initial thermal conditions of fresh concrete is a key parameter for limiting the development of DEF, preserving the mechanical properties of concrete, and ensuring the durability of applied mortars. In particular, the initial temperature of fresh concrete should not exceed 35 °C, since higher temperatures may promote the development of internal sulfate reaction (ISR) within the concrete itself.
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Influence of nanoadditives on PVC composition properties
Scientific article
Introduction. In this scientific article a scheme of the no synergistic effect is observedion process is considered. It has been shown that to slow down or suppress the main process occurring in the condensed phase and determining the formation of gaseous fuel several methods can be used: addition of polymers with increased thermal stability; addition of nanoadditives that reduce the amount of gaseous degradation products; introducing nanoadditives that affect the heat capacity or thermal conductivity of the system, thus changing the thermophysical characteristics of the polymer material. At the same time reduced reaction speeds, occurring in the gas phase and supporting the combustion process, can be achieved through reduction of the concentration of combustible gases and inhibition of the reactions responsible for the branching of the combustion chain process. Methods and materials. The composition and physical properties of kaolin are given. Kaolin monocrystal is a two-layer aluminosilicate containing water of hydration and consisting of chemically bonded layers of silicon dioxide and hydrated alumina. Results and discussion. We have studied the dependence of the attenuation time of a PVC composition on a composition containing from 3 to 10% kaolin. The introduction of kaolin into the PVC compound has led to decrease of decay time from 4.5 to 1 seconds. The effect of the amount of plasticizer on the oxygen index has been studied. We used dibutoxyethyl adipate (DBEA) as a plasticizer. It has good polymer compatibility and is environmentally friendly. The possibility of reducing the content of dibutoxyethyl adipate in the basic formulation of the original plasticate I40-13A by increasing the amount of calcium carbonate was studied, then the performance properties of the resulting compositions were studied. The content of PVC and other components in the basic recipe remained unchanged. Analysis of the data showed that for plasticization of 62% wt PVC contained in I40-13A, 20% wt DBEA is sufficient, while the filler content can be increased at least twice. The oxygen index (OI) value at a component ratio of 20% DBEA + 13.56% CaCO3 increases by 4 OI units and becomes equal to 29.1%. The dependence of the oxygen index of PVC compound on the composition containing from 5 to 20% kaolin has been studied. The results showed that the oxygen index of plastic compound increases significantly with increasing kaolin content. The OI drops with a decrease in the amount of the introduced, and it remains unchanged with its increase. Thus, the optimal content is 15%. Conclusion. Thus, kaolin is a promising, inexpensive and environmentally friendly filler for PVC materials, which effectively reduces their combustibility. The same effect is achieved by increasing the content of calcium carbonate in the original PVC compound formulation. However, no synergistic effect was observed while mixing kaolin and an excess of calcium carbonate.
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Liquid crystaloptical shutter for stained glass and windows
Scientific article
Introduction. Liquid crystal as a nanomaterial has found application in science, engineering and technologies. The unique physical properties of liquid crystals make them sensitive to external influences. The article presents the results of an experimental study of the flexoelectric effect in a liquid crystal, when shear deformations occur, thin layers of which can serve as an optical shutter for the stained glass windows of buildings. Materials and methods. Nematic liquid crystals with a homeotropic orientation of molecules 10÷100 μm thick were used by the birefringence method. Shear frequency 1 kHz. Methods. The experimental cell was assembled from two glass plates in the form of a flat capacitor, spacers were placed between the glasses, which set the sample thickness. A source of shear vibrations was located on the side of the microscope stage, which was connected to the LC cell using a thin waveguide. Results and discussion. According to the geometry of the problem, the director is headed vertically parallel to the Z axis, the velocity vector of the plate vibrations is horizontal along the X axis. The orientation of the liquid crystal molecules in the volume is characterized by the angle θ. An elastic-viscous wave propagates between the moving and stationary substrates of the LC cell, which leads to a perturbation of the initial homeotropic orientation of the director field. The dependences of the first and second harmonics of the shear-induced EMF, as well as the optical signal, on the plate oscillation speed are obtained. They have a threshold nature of occurrence at a critical speed υc~8 mm/s, while the liquid crystal molecules are oriented at an angle θс. The temperature dependences of EMF harmonics far from the nematic – isotropic liquid phase transition showed that when approaching the phase transition, the regression of the signal U1ω stops, and then its value increases up to the temperature transition of the nematic – isotropic state TNI. The magnitude of the optical signal I2ω/Io(T), approaching the phase transition, increases, which is explained by the increase in the amplitude of the director oscillation Θd. Conclusion. The article considers the flexoelectric effect observed in thin layers of nematic liquid crystals with homeotropic orientation of molecules placed between two glass plates. The occurrence of the effect has a threshold character, the critical strain rate is about 8 mm/s. The conditions and parameters of the effect (shear amplitude, sample temperature) on a condenser cell for various liquid crystals are considered. It is proposed to use the results obtained to create an optical shutter (shutter) for stained glass windows or windows of buildings and structures.
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Management Analytics: A Bibliometric Analysis
Scientific article
Introduction. As nanotechnology continues to evolve and its industrial applications expand, the need for effective data management, analysis, and dissemination is becoming more urgent. Management analytics has emerged as a critical new interdisciplinary field in current business environments, enabling organizations to leverage data-driven insights for informed decision-making and strategic planning. Methods and materials. This study reviews and analyzes research in the interdisciplinary field of management analytics for the period from 2021 to 2023. To conduct bibliometric analysis, data from various sources were used, including academic publications, monographs, reviews, reports, etc. Through a systematic review of the relevant literature, this study aims to provide insight into key topics, methodologies and outcomes in the field of management analytics, as well as to identify directions for future research directions. Results: according to the results of the analysis, it was found that the main source of articles in this area is the Journal of Management Analytics. The total number of publications on this topic for the period amounted to 83 units, the total number of citations for a certain time period has been increasing. The leading countries in terms of the number of citations of academic articles on the topic under study are the United States, India and China. Discussion. So far, the interdisciplinary field of management analytics has not been widely discussed in academic circles. However, leading countries in the world in terms of the number of academic articles and citations are at the forefront of this emerging field. This should be taken into account especially in the development of the nanosystems and nanomaterials industry, which is one of the priority areas for the development of science and technology, where management analytics technologies will be in demand and can provide competitive advantages to companies. Conclusion. The importance of the new interdisciplinary field of management analytics will continue to grow. In the course of the study, it was found that this emerging field has been increasing its popularity and it could be an effective tool for organizations in the nearest fu-ture.
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Scientific article
Introduction. Existing automated construction inspection technologies do not allow the user to select the level of detail. At the same time, in the context of the use of nanotechnology, there is a growing need to expand the capabilities of monitoring and control of construction projects. The aim of the research is to develop, implement software, and validate a technology for controlling the speed and accuracy of constructing three-dimensional models from dense point clouds for automated monitoring of construction works. Materials and methods. The research is based on the methodology of non-binary data trees, including the method of constructing octant trees. An unmanned aerial vehicle with an aerial laser scanner, a ground-based scanning total station, and specialized software were used, including the web application “Management System for Monitoring Construction Works on Objects that have undergone state expertise” developed with the participation of the authors. Results and discussion. In the course of the study, a technology was developed and implemented in software that allows the user to select the required balance between accuracy, degree of detail of monitoring and control data for construction work and time costs and computing power requirements. The comparison is made between a construction project, presented in the form of a building information model, and a three-dimensional model of a real object, obtained from a dense point cloud. The degree of comparison accuracy is set by choosing the level of octrees used. By default, the web application uses level eight. However, in the early stages of construction, when the geometric parameters of a dense point cloud deviate significantly from the design boundaries, the ninth, tenth and other levels can be used. In this case, the accuracy and degree of detail increases. Positive and negative deviations are visualized in red and blue colors, respectively, which allows the user to monitor and control the progress of work at the site. Conclusions. The developed technology can be used by customers and other decision makers to control and monitor work.
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Scientific article
Introduction. Modern trends in the construction and paint industries are aimed at creating environmentally friendly materials with improved protective and decorative properties. Water-based styrene-acrylic dispersions are widely used for painting facades and wooden structures, but their performance characteristics, particularly hydrophobicity, moisture resistance, and adhesion strength, are often subject to increased requirements. A promising method of nanomodification is the introduction of organosilicon compounds for targeted modification of surface properties and interfacial interactions in the polymer matrix. Materials and мethods. The study was conducted on a styrene-acrylic dispersion using three types of additives: a wetting agent based on polyether-modified polysiloxane, a water-repellent agent in the form of a polysiloxane emulsion, and a wax silicone emulsion. The coating properties were tested using standard methods. Results and discussion. It was found that the introduction of a water-repellent ensures a reduction in the surface energy of the coating from 45.9 to 9.6 mN/m. The surface transitions from a hydrophilic state with a contact angle of 54° to a hydrophobic state with an angle of up to 106°. A wax emulsion also enhances hydrophobicity, increasing the contact angle to 92°. Nanomodified styrene-acrylic dispersions exhibit a significant increase in gloss (up to 56 GU) and enhanced resistance to aqueous media while maintaining high adhesion. A plasticizing effect of the additives, leading to a decrease in coating hardness, was revealed. Conclusion. The developed formulations, based on aqueous styrene-acrylic dispersions and organosilicon additives, improve their processing properties. They can be used to produce coatings with increased hydrophobicity, water resistance, and improved decorative properties. The ability to specifically control the hydrophobicity-mechanical strength ratio has been demonstrated. This opens up prospects for the use of these compounds in conditions of high humidity and other atmospheric influences.
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Scientific article
Introduction. The article considers the issue of modifying the initial chrysotile fiber and its bundles by the action of hydration products of Portland cement and various acidity value of the treated medium. A brief justification of the relevance of the research topic is provided. It is noted that recently, issues of production of composite materials based on natural and man-made raw materials, which are a promising area of modern economics, have aroused great scientific and practical interest. The availability and low cost of raw materials, as well as low energy, transportation, and overhead costs, contribute to reducing the cost of composite materials. At the same time, the high contractual prices and strong demand in both domestic and foreign markets provide incentives for increasing production volumes. The aim of the research is to study the behavior of the initial chrysotile fibers and their aggregates in the composition of the cement component under the influence of different acidity of the treated medium. Research objective: to investigate the behavior of chrysotile cement dust components under an aggressive environmental condition with electron microscopy examination; calculation of the number and dimensional characteristics of nanofibers and dust particles under the influence of various exposure times of the aggressive factor; microdifraction studies of the nanostructure of the studied samples after exposure to acidic media. Materials and methods. The materials used in the research and their characteristics are given, in particular, chrysotile cement dust containing fibers of commercial chrysotile, acidity of the medium, exposure time, micro- and nanofibers obtained after exposure to aggressive medium. Samples of chrysotile cement dust were taken at the slate production No.1 of JSC “BelACI” and collected at the place of sawing of chrysotile cement products, underwent the stage of dispersion using a centrifugal separator. In the work chrysotile cement dust was used as an object of environmental pollution and its further use in the production of composite chrysotile cement products. Results. The results of studies on the influence of aggressive environment on the components of chrysotile-cement dust, their size characteristics, and structural nano-changes are presented. The studied samples have been examined in a scanning ion-electron microscope at magnifications of 200x, 500x, 5000x, 10000x, and their chemical composition have been analyzed. Discussion. The results of analysis of the obtained experimental data are given. Quantitative composition of fibers and aggregates of fibers in chrysotile cement dust changes after its exposure in acidic medium in comparison with their quantity in initial chrysotile cement dust, and the quantity of separate thin fibers increases, it is explained by the fact that in acidic medium there is not only destruction of cement stone, but also splitting of bundles of chrysotile fibers into micro- and nanofibers. Conclusions. Electron microscopic examination of initial commercial chrysotile fibers and their bundles in cement dust have shown changes in their dimensional and quantitative characteristics, including the products of Portland cement hydration under the influence of the factor of aggressiveness of the environment.
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Scientific article
Introduction. Currently, the development of photocatalytically active cement-based materials with self-cleaning properties is a promising area of building materials science. Self-cleaning concrete is obtained by using photocatalytic additives, of which titanium dioxide (TiO2) is the most common. It has been found that the functional properties of TiO2 depend largely on its phase composition. This study aimed to establish the patterns of influence of phase composition on the photocatalytic activity of titanium dioxide under the impact of artificial ultraviolet and natural solar radiation and to identify the most effective titanium oxide-based photocatalysts for subsequent use in the composition of self-cleaning concrete. Methods and materials. Four titanium dioxide samples, namely two industrial samples and two samples synthesized by hydrolysis of titanium alkoxide in acidified water-alcoholic medium followed by calcination at 500 °C, were the objects of the study. X-ray powder diffractometry was the method used to investigate the structure parameters of TiO2 samples. The model reaction of oxidative degradation of methylene blue under UV- and daylight exposure was the means for studying the photocatalytic activity of titanium dioxide samples. Results and discussion. It was found that polymorphic modifications of titanium dioxide had a multidirectional effect on its functional characteristics, in particular, a rise in the content of anatase and rutile led to an increase and decrease in the photoactivity of TiO2 samples, respectively. The single-phase sample with anatase structure was most effective under UV irradiation, while the three-phase sample with the anatase : brookite : rutile ratio of 67% : 13% : 20% had the highest activity under daylight exposure. The photocatalyst composition, including several polymorphs of TiO2 with a predominance of anatase form (more than 50%), allowed to achieve a synergistic effect of increasing the photocatalytic activity of titanium dioxide under conditions of solar radiation due to the formation of type-II semiconductor heterojunctions. Heterostructures made it possible to improve the spatial separation of charge carriers and to reduce the recombination rate of photogenerated electron-hole pairs. Conclusion. The obtained results indicated the possibility of improving the functional characteristics of titanium oxide-based additives for self-cleaning concrete due to the targeted regulation of their phase composition by optimizing the synthesis parameters of photocatalytic modifiers.
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Nanotechnology in Construction: State of the Art and Future Trends
Scientific article
The construction industry has long been regarded asenergy-intensive and high pollution industry. The emergence of nanotechnology provides an ideal solution for the construction industry to energy saving and consumption reduction. The introduction of nanotechnology has greatly promoted the development of new green building materials and brought huge economic and social benefits. This paper applies bibliometric analysis to review the nanotechnology-construction research collected by Web of Science database during 2000–2020, and further visualize their literature characteristics. At the global level, the number of literatures on nanotechnology-construction research has been on the rise in 2000-2019, although it has experienced a small decline in individual years. At the national level, the United States has become the global leader in nanotechnology-construction research with 63 articles, far more than other countries. Considering the income gap, developed countries play an indispensable role in the global nanotechnology-construction research system, while the role of developing countries is relatively weak. We found that the existing nanotechnology-construction research mainly focused on the fields of chemistry and materials science. According to the frequency of keywords, the research focus of nanotechnology-construction research mainly focused on the development and application of new building materials. It is concluded that with the extensive attention of researchers, the future research on nanotechnology-construction will continue to appear and increase at increasing rate.
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Ni-SiC composite coating obtained by electrodeposition
Scientific article
Introduction. One of the common types of coatings is a composite coating based on nickel reinforced with solid particles of silicon carbide SiC. It has high anti-wear properties and is widely used to increase the strength of the working surfaces of internal combustion engine cylinders. The basic technology for applying the coating is electrodeposition. The quality of the coating is affected by the size of the solid particles. Difficulties in forming a composite arise when moving to a large fraction of 20–25 μm, especially when moving from flat samples to long axisymmetric parts. The aim of the research is to study the technological potential of creating a Ni-SiC coating on flat samples simulating a sector of an axisymmetric part. Methods and materials. The research part of the work was carried out on samples of aluminum alloy AK7. Electrodeposition mode: current density 10 A/dm2; duration 60 minutes; temperature 60 °С. The microstructure of the coatings was studied using an Olympus GX51 optical microscope. Coating wear resistance tests were performed using a CSM Micro-Scratch Tester. Microhardness was assessed using a DuraScan 50 microhardness tester. Roughness Ra was determined using a Mitutoyo Surftest profilometer. Results and discussion. The article considers the features of the process of forming a composite coating based on Ni-SiC by the electrodeposition method. A model of the action of electrostatic, gravitational and centrifugal forces on SiC particles in the electrolyte solution for electrodeposition is presented. Based on the model, an installation was designed, on which the technological process of applying a composite Ni-SiC coating to flat samples of aluminum alloy AK7, simulating a sector of an axisymmetric part, was successfully tested. Due to the possibility of rotating the installation during the electrodeposition, three types of coating were obtained: nickel-based «Ni»; nickel-based with silicon carbide particles ”Ni-SiC”; layered coating. Conclusion. The nickel coating with a uniform distribution of SiC particles is characterized by the maximum microhardness value, increased roughness and a small groove width after the scratch test, which indicates good adhesion to the substrate material.
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Scientific article
Introduction. The management of physical and chemical processes of structure formation of high performance cement composites can be provided at several scale levels through the use of modifiers of various nature and mechanism of action, in particular, micro- and nanoscale mineral additives of natural and technogenic origin. It is known that clays and carbonate rocks are promising raw materials to obtain mineral modifiers for cement systems. The purpose of this study was to establish the influence regularities of the prescription and technological parameters (material and granulometric compositions, temperature calcination) to obtain mineral additives based on calcined clays and carbonate rocks on their activity in cement systems. Methods and materials. Polymineral clays and carbonate rocks (dolomite and chalk) from several deposits of the Republic of Mordovia were used as raw materials for obtaining mineral additives. The specific surface area of modifiers was determined on the PSX-12 dispersion analysis device using the Kozeny-Carman method. The study of the granulometric composition of sedimentary rock powders was carried out by laser diffraction method. The research of physical-chemical processes occurring during the heat treatment of polymineral clays and carbonate rocks was carried out using the synchronous thermal analysis method. Optimization of calcination temperature of clay-carbonate mixtures was carried out based on the research results on the effect of their additives on the cement binder activity with the determination of the modifier activity index in accordance with the methodology of the Russian State Standard GOST R 56178-2014. Results and discussion. The optimum calcination temperature, located for polymineral clays in the area of 500–800оC, was established according to the study results of dehydration processes of clay minerals using the synchronous thermal analysis. This temperature range corresponds to the initial restructuring processes in the crystal structure of minerals of the kaolinite and illite groups, associated with their dehydroxylation, which contributes to the transition of these phases to the active form. The study results of influence of additives of calcined clay-carbonate mixtures on the cement binder activity proved the thermal analysis data. It was found that calcination of clays and clay-carbonate mixtures at 700°C contributes to obtaining of the most effective mineral modifiers. Conclusions. On the totality of studies, regularities were revealed in the system “modifier composition – calcination temperature of sedimentary rocks – mixed binder activity”, which allow optimizing the prescription and technological parameters for obtaining mineral additives to achieve the required level of strength characteristics of cement composites.
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Optimization of the composition and properties of a ceramic composite based on barite and bentonite
Scientific article
Introduction. Currently, barium sulfate is actively used in various industries, including paper manufacturing, construction, paints and coatings, rubber, chemical, metallurgical, and electrical engineering industries, as well as in agriculture and medicine. Literature analysis has shown that the composition and properties of barium sulfate depend on its deposit. Different processing technologies have been developed for barium sulfate, including methods for producing materials for a wide range of applications. Particular attention is given to creating radiation-resistant and radiation-shielding materials, including radiation-resistant concretes and ceramics. Methods and materials. In Kyrgyz Republic, there are more than 40 barium sulfate deposits. Among them, the "Arsy" deposit stands out particularly, with sufficient reserves. The chemical composition of barium sulfate from the "Arsy" deposit was analyzed using atomic emission spectrometry, X-ray fluorescence method, and silicate chemical analysis. The analysis results showed that the chemical composition of barium sulfate includes barium sulfate (BaSO₄) at about 89–91%. The remaining components are impurities: calcium (Ca) – 8–8.4%, silicon dioxide (SiO₂) – 1.6–1.8%, aluminum oxide (Al₂O₃) – 0.1–0.13%, and iron oxide (Fe₂O₃) – 0.15–0.25%. Micro-silica is a fine-dispersed powder consisting of silicon dioxide (SiO₂) particles ranging from 0.1 to 0.3 micrometers in size. Its SiO₂ content is approximately 85–98%. It also contains impurities: aluminum oxide (Al₂O₃) – 0.2–0.8%, iron oxide (Fe₂O₃) – 0.1–0.5%, and calcium oxide (CaO) – about 0.5%. The chemical composition of bentonite from the Abshir deposit is characterized by the following component contents: silicon dioxide (SiO₂) – 65.84%, aluminum oxide (Al₂O₃) – 14.8%, iron oxide (Fe₂O₃) – 4.35%, calcium oxide (CaO) – 2.85%, magnesium oxide (MgO) – 1.76%, loss on ignition (LOI) – 2.72%, and other impurities – 7.68%. For processing barium sulfate powder, a hydrocavitator was used, which ensures effective treatment of liquid media through a combination of cavitational and mechanical effects. Results. To develop the technology and optimize the composition and properties of the ceramic composite, bentonite clay, finely ground barium sulfate, and micro-silica were used as raw materials. The experiment was conducted based on a four-factor plan B4. Regression equations describing the dependence of the material’s density, water absorption, strength, and shrinkage on the varying levels of the factors were constructed from the levels of factor variation and the experimental data obtained. Corresponding nomograms reflecting the influence of the studied factors within the experimental plan were developed based on these equations. Optimal parameters ensuring high strength of the ceramic composite were identified: barium sulfate content of about 20–25%, micro-silica content of approximately 5%, firing temperature around 850 °C, and heat treatment duration of 30–45 minutes. Subsequently, the barium sulfate powder was processed using a hydrocavitator, after which the technological modes and physical-technical characteristics of the powder after cavitation treatment were determined. The composition and properties of the barium sulfate powder were analyzed using X-ray diffractometry, performed on an AL-27MINI diffractometer within the 2θ range of 10° to 70°. Fourier-IR spectra were recorded on an IRSpirit-T spectrometer equipped with a QATR-S accessory, within the range of 400–4000 cm–1. Conclusion. Optimization of the composition and properties of the ceramic composite based on the analysis of mathematical models indicates that it is advisable to use barium sulfate powder in an amount of about 20–30% and micro-silica up to 10%, at a firing temperature of 850–900 °C and a heat treatment duration of 30–45 minutes. Such a composition allows achieving high strength and water resistance of the material. After cavitation treatment, barium sulfate powder changes its chemical activity and can be used in the composite in an amount up to 20% by mass relative to the bentonite. Adding more than 20% of barium sulfate powder causes intense chemical reactions due to the presence of sulfur, leading to the destruction of the material’s structure. Therefore, it is recommended to limit the barium sulfate content to a maximum of 20% to avoid undesirable effects, including explosive or destructive processes within the ceramic composite structure.
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Scientific article
Introduction. Active mineral additives that allow controlling the structure formation processes and properties of cement systems are important components of modern modified concretes. Among the numerous types of modifiers for cement composites, the most effective ones include siliceous and aluminosilicate additives containing a significant amount of nanoscale particles, in particular, nanoparticles of silicon dioxides, clays, aluminum oxides and iron oxides. At the same time, common sedimentary rocks, such as diatomites, trepels, opokas, polymineral clays, etc., along with industrial wastes (silica fumes, fly ashes, metallurgical slags) can be promising raw materials for obtaining such modifiers. The purpose of this study was to establish the influence regularities of mineral additives based on sedimentary rocks of various composition and genesis on the technological and physico-mechanical properties of cement systems with the identification of the most effective modifiers. Methods and materials. Siliceous rocks (diatomite and opoka), calcined polymineral clays and carbonate rocks (dolomite and chalk) from several deposits of the Republic of Mordovia were used as mineral additives. The study of the chemical and mineralogical composition of sedimentary rocks was carried out using X-ray spectral fluorescence spectrometry and X-ray powder diffraction methods. In addition to the chemical and mineralogical composition, at the initial stage of the study, the specific surface area of mineral additives and Portland cement was determined on the PSX-12 dispersion analysis device using the Kozeny-Carman method. Prescription and technological efficiency of the applied mineral modifiers was evaluated by their effect on water demand, water-holding capacity, flowability of cement paste and mixed cement binder activity. The physical and mechanical characteristics of cement systems were determined using standardized and well-known authorial methods. Results and discussion. There were established correlation dependences between indicators of water demand, water-holding capacity, flowability of cement systems and specific surface of mineral additives used. In addition, relationship between the activity index of the studied modifiers and the content of silicon dioxide in their composition was revealed. Conclusions. According to the totality of the conducted studies, diatomite, opoka and calcined polymineral clay were identified as the most promising types of mineral additives. The increased effectiveness of these modifiers in cement systems is due to the peculiarities of their chemical and mineralogical composition, in particular, the presence of active silica-containing components (reactive minerals with an amorphized structure) such as opal-cristobalite-tridymite phase in diatomite and opoka as well as products of partial thermal destruction (dehydroxylation) of minerals of kaolinite and illite groups in the calcined polymineral clay.
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Processing of rice huskss and obtaining a ceramic composite based on it
Scientific article
Introduction. Every year, the demand for rice around the world is steadily increasing, leading to an expansion of its cultivation and production. However, this increase in production also leads to the generation of large amounts of waste, particularly rice huskss. The introduction provides a literature review of the processing and use of rice huskss for various purposes. When producing 1 ton of polished rice, about 200 kg of rice huskss is formed, from which approximately 40 kg of ash remains after burning. Methods and materials. As a result of the research it was established that the main components of rice huskss are: cellulose (40-45%), lignin (about 20–25%) and hemicellulose (about 15%). The rest of the composition depends on the deposit and variety of rice. Processing rice huskss using hydrocavitation and pyrolysis units opens up new possibilities for producing ceramic composites. A spectral analysis of the chemical composition of rice husks from the Suzak district was carried out. The results of the analysis showed that the main component of the solid mass of rice husks is SiO2 – 400 mg/kg, MnO – 195 mg/kg, K2O – 120 mg/kg, MgO – 30 mg/kg, CaO – 20 mg/kg, P – 13 mg/kg, Na2O – 3.9 mg/kg, Fe2O3 – 3 mg/kg, Ag – 0.04 mg/kg, and other impurities. The article presents a methodology for studying the composition and properties of rice huskss components. A flow chart for the process of fast pyrolysis of rice husks is presented. The preliminary chemical composition of bentonite from the Tegerek deposit was determined by the spectral method as part of the development of a ceramic composite. Main components: SiO₂ – 50%, Al₂O₃ – 12%, Fe₂O₃ – 12%, MgO – 4%, CaO – 3%, K₂O – 2%; other elements are present as minor impurities. Results. The experimental part used hydrodynamic cavitation technology, as a result of which rice huskss was processed using a hydrocavitator. Results: It was found that after cavitation treatment, rice husks is divided into three fractions: coarse mass – 75%, plastic mass – 15.83%, and a fine fraction, constituting 9.6%, suspended in water. The composition, structure and physical and technical characteristics of the coarse and plastic fractions of rice husks were studied. Rapid pyrolysis of the coarse fraction after cavitation treatment was carried out. Based on the resulting ash and silicon-carbon material formed during the pyrolysis process, dense and porous ceramics for various purposes were synthesized. Conclusion. A technology for processing rice huskss using the created hydrocavitator and the method of fast pyrolysis for obtaining a ceramic composite has been developed. A study has been conducted of the composition and structure of rice huskss after cavitation treatment, as well as solid residues formed as a result of fast pyrolysis. As a result, both dense (ρ = 1.19–1.22 g/cm³) and porous (ρ = 0.51–1.02 g/m³) ceramic composites based on processed rice husks were obtained using hydrocavitation and pyrolysis.
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Scientific article
Introduction. In the article we analysed the technology for producing silicon from rice husks. The analysis showed that the production of polycrystalline and amorphous silicon based on rice waste in the form of rice husk solves the simultaneous disposal of rice waste. Rice husk processing produces valuable organic products, and the residual solid waste mainly contains silicon, carbon and other trace metal elements. Therefore, obtaining silicon and silicon-containing materials from rice husk is relevant. Methods and materials. Various methods for obtaining silicon from rice husk are given. Among them, the methods of chlorination and sublimation were chosen, and experimental installations were assembled to conduct the experiment. The object of study was samples obtained from rice husks of Uzgen rice in the Kyrgyz Republic. Results. The composition and structure of rice husks for the production of crystalline silicon were studied. Lime milk was used to purify toxic chlorine-containing gases in the air of the working area and atmospheric air. The condensing system, designed to capture volatile chlorides, has two receivers. In the first receiver at a temperature of 60°C, condensation of iron, aluminum and magnesium chlorides occurs. It has been established that highly volatile silicon (IV) chloride (SiCl4) at a given temperature remains in the gaseous phase and is completely distilled off in the next receiver of the refrigerator. This indicates that the silicon is in the form of SiCl4 (60°C) and condenses only at a lower temperature in the next receiver. The data obtained indicate that when the temperature rises to 200°C, the process of chlorination of metal compounds initiates. The optimal conditions for maximum extraction of metals and silicon tetrachloride from rice husk were identified: temperature 500–550°C and time 120 minutes. Non-volatile chlorides of calcium, sodium, potassium and other elements form a floating mixture at 450°C. During the reaction, metal chlorides harden and settle on the cold walls of the reactor. Therefore, at this temperature there is not enough heat to maintain them in a gaseous state, and they condense to form solid precipitates. Lime milk containing CaO – 130 g/dm2 is a very effective and cheap means for purifying toxic chlorine-containing gases in the air of the working area and atmospheric air. At high temperatures (1050–1100°C), it is possible to activate chemical reactions between the carrier gas (hydrogen) and silicon chloride (SiCl4), which promotes the decomposition of SiCl4 into components, including silicon and hydrogen chloride, and also provides certain conditions for the formation and deposition silicon crystals. Conclusion. A technology for producing polycrystalline silicon by chlorination from rice husks of Uzgen rice of the Kyrgyz Republic has been studied and developed.
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Resource-saving nanotechnologies in waste water treatment
Scientific article
This paper examines the prospective field of nanotechnology development in the area of wastewater treatment and water processing. The introduction showed (no need for comma) that the Russian problem is not the lack of water – but its quality. Water treatment is needed to prevent water facilities from pollution. Self-cleaning methods cannot withstand the massive impact of pollutants, some of which are unknown for their natural reproduction processes. The degree of purification depends on the concentration of the pollution and the content of different substances within it. The use of nanotechnologies in effluent neutralization (EN) processes will allow removing insoluble sludges, wastes of chemical industry, and harmful microorganisms. Methods and materials. This work presently uses analytical methods to study nanotechnologies. Nanofiltration and membrane methods are frequently used in wastewater treatment. Methods such as arc charge, ablation, and gas-phase deposition are applied to obtain carbon nanotubes. Results. The authors describe promising carbon nanomaterials for production of membranes used in purification/decontamination/ desalination of water. The new generation of membranes for filtering, disinfection, and desalination have been shown. These include graphene and carbon nanotubes which present absolutely new nanomaterial. Discussion. It was revealed that such membranes are characterized not only by a high water percolation rate, but also by extraordinary selectivity. Such membranes are particularly promising in the field of biomedicine, as large membranes are necessary for the nanofiltration and desalination processes. Conclusions. This paper examines new ecological and resource-saving technologies making possible improved research, industrial and commercial activities (which by means of practical implementation of inventions will lead to improved products), technologies and organizational decisions. One of the most promising areas for the development of nanotechnologies applied in waste water treatment is the advancement of membrane technology employing innovative materials, specifically graphene and carbon nanotubes.
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