Nanotechnologies in Construction: A Scientific Internet-Journal @nanobuild-en
Статьи журнала - Nanotechnologies in Construction: A Scientific Internet-Journal
Все статьи: 538
Статья научная
Introduction. Currently one of the focus areas for the development of construction material science is the creation of self-cleaning concretes characterized by polydisperse multicomponent composition with the presence of nanoscale photocatalytic additives, primarily based on TiO2. These photoactive modifiers give the material a number of positive properties, including the ability to decompose atmospheric pollutants, to self-clean the surface, etc. The promising method for improving the functional characteristics of titanium oxide photocatalysts is the creation of nanostructured systems with ‘core (substrate) – shell (photocatalyst)’ architecture. Previous research results show that the final efficiency of the synthesized composite photocatalytic modifiers largely depends on the level of substrate reactivity in the cement system. The purpose of this study is to investigate the impact of three types of siliceous rocks (diatomite, trepel, and opoka) on cement stone formation processes and to identify the most effective raw materials for use as photocatalytic carriers in self-cleaning concrete compositions. Methods and materials. The methods of Kozeny-Karman, laser diffraction and X-ray fluorescence spectrometry were used to determine the specific surface area and parameters of granulometric and chemical compositions of silicite samples. The phase composition of siliceous rocks and modified cement systems was studied by X-ray powder diffractometry. Results and discussion. The main parameters of granulometric composition of diatomite, trepel and opoka were determined. The predominance of reactive modifications of free silica (47.6–78.0 wt. %), represented by amorphous opal-A or cryptocrystalline OCT-phase (opal-CT), were revealed in the structure of silicites. It was found that increasing the dosages of silica-containing additives from 0 to 10% resulted in decreased by 10–27% in the quantity of portlandite in the phase composition of cement stone aged 28 days, while the content of high-strength low-basic calcium hydrosilicates (C–S–H (I)) increased by 11–27%. Conclusion. The chemical and mineralogical composition peculiarities of silicites, as well as the nature of the impact of silica-containing modifiers on the structure formation processes of cement systems, determine the prospects of using opal-cristobalite rocks as dispersed photocatalyst carriers for self-cleaning concrete.
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Статья научная
Introduction. Recently, the term “nature-like technologies” has appeared in the everyday life of scientists and politicians, which quite deservedly include the so-called alternative energy sources (sun, wind, heat). At the same time, despite the fact that installations using these sources are “seasonal” and low concentrated, their use is rapidly and haphazardly developing, and many economists and politicians mistakenly consider them as basics, misleading business. Based on the analysis of the epistemology of the origin of the term "nature-like technologies", this article shows the groundlessness, and even the harm of the rapid and unsystematic use of wind turbines. Evidence is given of the inconsistency of the "myths" that Nature cannot cope with the compensation of the economic activity of mankind, therefore, according to Academician Sergeyev S.M., President of the Russian Academy of Sciences, "reengineering of the technosphere" is required. At the same time, modern economic science is far from taking into account in his models of the assimilation potentials of the biosphere of regions and the functions of entropy production in them, preferring to model various “cycles and modes”, as well as calculate different “coefficients” in order to predict “crises and equilibria”, without taking into account the interaction nature and society. In this connection, a scientific and technical task about determinating the “place of reengineering of the technosphere” in the structure of the life support systems of society, and, consequently, to evaluate its effectiveness. Methods, models and tools. To solve the tasks set, it is proposed to use the “retro-forecast method” of socio-economic losses from the introduction of “natural nanotechnologies”, using as “tools” the method of “spatio-temporal analysis”, model of the Leontief-Ford and adaptive taxation systems of “harm production”, the use of which in solving the problems of fire and environmental safety in the "technospheres of the regions" of the South of Russia (in road transport infrastructures, in cities and towns, in buildings and structures), proved their adequacy to the processes under study and usefulness. Results and discussion. The results of modeling the costs of efficiency of "reengineering of the technosphere" in Russia, in particular individual residential buildings, and a retro-forecast of changes in socio-economic and environmental losses during the autonomy of their resource supply (electricity, water and heat) are presented. It is shown that the production of domestic innovations in this area (“Shukhov’s” wind turbines, atmospheric water condensation devices and electric heating) will allow stopping the “total gasification” of rural settlements, as well as more economically than abroad, to implement decentralized supply of resources in Russia more than 10 million individual houses and about 40 million country houses, thus determining the “true place of alternative energy” in the structure of the Russian systems of electricity, gas, water and heat supply. Conclusion. The proposed approach allows us to determine the place of the socalled renewable energy in the structure of resource supply systems for cities and rural settlements. At the same time, it is possible that the emergence of more productive design solutions of the proposed innovations in the field of wind energy and solar panels will expand the "autonomization" to low-rise and multi-apartment buildings in regional centers and workers' settlements, instead of a major restoration of centralized engineering systems with boiler houses and mini- CHP.
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Structural and heat-insulating cement-based concrete with complex glyoxal based additive
Статья научная
Introduction. The article presents the results of studies of the effect of complex additive based on glyoxal on the properties of cement-based foam concrete mix and foam concrete of natural hardening. The relevance of the study is determined by the necessity to provide the required process parameters of mixture for transportation and laying the formwork, as well as providing strength and thermal and physical characteristics of wall structures for the development of the northern regions of Russia, including the Arctic zone. It has been proposed to decrease the shrinkage deformations of the concrete mix and increase compressive strength of hardened foam concrete by affecting the cement matrix with complex modifier based on glyoxal. Materials and methods. The effect of modifying additives on the properties of the foam concrete mixture and foam concrete was studied at a W/S mixture ratio of 0.45. Research has been carried out using test methods set out in national standards. The results of the study of the effect of complex modifying additives (CMA) based on an aqueous solution of glyoxal and organic acids on the rheological and strength properties of foam concrete are presented, the regularities of the processes and the mechanism of structure formation of the modified foam concrete are determined. Results. The use of modifying additives leads to increase result in increasing the aggregative stability and reducing the plastic shrinkage of the foam concrete mix by 22–70%. In foam concrete with the complex additive LA 0.5% + Gl 0.55% the compressive strength rises from 1.96 to 2.43 MPa at the age of 28 days while maintaining the average density of D600. The thermal conductivity coefficient of foam concrete modified with various additives decreased by 5–30% compared to references. Conclusions. The obtained results of the study create in the construction industry the basis for the import substitution of modifying additives on the domestic mineral resource base and the production of effective structural and heatinsulating concretes for the development of the northern regions of Russia.
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Structural and heat-insulating foam concrete for individual monolithic housing construction
Статья научная
Introduction. The article presents the results of studies of structural and heat-insulating cement-based foam concrete for monolithic individual housing construction using porous aggregates sand and superplasticizers. The relevance of the study is to improve the technological properties of foam concrete mixtures to enhance their transportation and laying in formwork, as well as to increase the strength and thermal insulation parameters of wall materials used in individual housing construction. A synergistic effect is ensured and increased stability of the foam concrete mixture is achieved, resulting in an increase in the grade of compressive strength of foam concrete and a decrease in thermal conductivity by partially replacing quartz sand with expanded clay or slag sand in the amount of 25% by volume and introducing the superplasticizer “Steinberg MP-4”. Materials and methods. The study of foam concrete mixture and foam concrete was carried out in the accredited laboratory of TSUAB in accordance with the requirements of national standards. Results. The use of combined additives, including a superplasticizer and a mineral porous aggregate, leads to increase the grade of compressive strength of foam concrete from B1 to B2 while maintaining the average density grade D600, and also allows reducing the thermal conductivity coefficient of foam concrete to 17% compared to the basic composition. Conclusion. The developed compositions for the production of monolithic structural and heat-insulating foam concrete of natural hardening with a combined additive, including mineral porous aggregate and current plasticizers, are recommended for individual housing construction of low-rise buildings.
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Structure formation in the «clay soil – carbide sludge» dispersed system
Статья научная
Introduction. Clay soil is a multiphase, multicomponent aluminosilicate dispersed system with specific properties determined not only by its composition but also by the formation of coagulative and transition contacts (binds) between the soil particles. One of the methods of changing soil properties is the introduction of active mineral additives that promote the formation of phase contacts (binds) between soil particles as a result of the pozzolanic reaction. The effectiveness of using carbide sludge, which is a multi-tonnage lime-containing waste (the content of active calcium oxide reaches 56%) as an additive, has been proved. However, to date, the proposed mechanism of interaction in the «clay soil – carbide sludge» system is based only on the literature data and has not been experimentally verified. The purpose of this research is to study the mechanism of structure formation in the «clay soil – carbide sludge» dispersed system. Methods and materials. A soil model has been created by mixing saponite-containing material with sand, which corresponds to the composition and properties of sandy loam. The carbide sludge in the form of a suspension was selected from the sludge collector, dried to a constant mass and sieved. Microstructural analysis, differential thermal analysis (DTA), and X-ray phase analysis were used to study the mechanism of structure formation. Results and discussions. Based the results of the differential thermal analysis, there is a decrease in the intensity of the endothermic effect in the range of 460 to 470°C associated with the decomposition of calcium hydroxide in the treated sample. Additionally, an endothermic effect is observed at 750°C, which indicating the decomposition of calcium silicate hydrate. The results of differential thermal analysis are confirmed by X-ray phase analysis, which shows the presence of tobermorite group hydrosilicates in the reaction medium. The study of the microstructure of the analyzed mixtures revealed a decrease in the specific volume of pores with a diameter of 4–5 nm in the modified clay soil. This is associated with gelling from particles of new hydrate formations. Besides that, the volume of pores with a diameter of more than 6 nm increased, which indicates the process of contraction. Conclusion. The mechanism of structure formation in the «clay soil – carbide sludge» system has been established.
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Structure formation of lime composites with polysaccharide additives
Статья научная
Introduction. The research is aimed at obtaining a lime composition and coating based on it for the restoration of cultural heritage sites. Materials and methods. We used for study slaked lime (fluff) with an activity of 83%. Sunbo PC 1021 (a superplasticizer based on polycarboxylate ether), MasterGlenium 115 and Sika ViscoCrete-226 P were used as plasticizing additives. The cohesive strength of the coatings was determined by the axial tensile strength. Rheological properties were assessed by plastic strength, which was determined using a KP-3 conical plastometer. Results and discussions. It was revealed that the introduction of polysaccharide additives contributes to a sharp increase in plastic strength compared to the control composition. The additive Sika ViscoCrete-226 P has the greatest plasticizing effect. It was revealed that the qualitative mineralogical composition of lime composites is the same. However, analysis of X-ray diffraction patterns indicates an increase in the intensity of CaCO3 reflections, which indicates an increase in the carbonization front. Control samples contain higher amounts of portlandite. A slight increase in the width of the CaCO3 peaks is observed, which indicates the possible introduction of organic molecules into the calcite composition. A change in the parameters of the crystal lattice was established in samples prepared with slaked lime in the presence of polysaccharides. Conclusion. The absence of chemical interaction between lime and polysaccharides has been established. It has been shown that coatings based on lime compositions with the addition of polysaccharides are characterized by higher cohesive strength. A change in the parameters of the crystal lattice was established in samples prepared with slaked lime in the presence of polysaccharides.
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Study of flocculating effects of ozone on wastewater of woodworking enterprises
Статья научная
The sewer of woodworking enterprises in the construction industry are characterized by a high content of suspended and dissolved toxic substances, including phenol, and a high value of chemical oxygen consumption (COD). At the same time, some enterprises do not have their own local treatment facilities and need to develop their own integrated treatment systems. One of the effective methods for removing pollution is wastewater ozonation, used in three versions: flocculation with small doses of ozone (pre-ozonation) at the initial stage to remove suspended substances, oxidative ozonation and decontamination. However, methods for treating wastewater from wood processing plants using ozone have not been sufficiently studied. Therefore, we investigated the flocculating effect of ozone in the process of cleaning the effluents of the plywood-plate mill, tested the effect of the dose of ozone during flocculation in the presence of a small number of coagulants VPK-402 and Kaustamine-15 on the concentration of suspended substances, phenol and COD value. VPK-402 and Kaustamine-15 – reagents of regional production, are low-toxic and are allowed for use in the treatment of even drinking water. The results of the experiments on the pre-ozonation of wastewater showed a high efficiency of this method, which allows reducing COD by 3.8 (VPK-402) and 2.3 times (Kaustamine-15), phenol content by 2.9 (VPK-402) and 1.9 times (Kaustamine-15), suspended content by 4.0 (ВПК-402) and 3.5 times (Kaustamine-15). The use of pre-ozonation makes it possible to completely abandon flocculants in the physicochemical stage of wastewater treatment. Coagulation-flocculation can be successfully carried out with ozone and coagulant in small doses of 2–5 and 40 mg/dm3 (VPK-402) or 50 mg/dm3 (Kaustamine-15), respectively, for 5 minutes. Physicochemical indicators of water quality improved compared to treatment with coagulant alone: COD decreased by 23%, phenol content by 55%, suspended substances by 22%. The use of ozone as a flocculant in the clarification of wastewater reduces the cost of reagents, prevents secondary contamination of water, and increases the efficiency of further oxidative treatment.
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Статья научная
Introduction. This study aims to carry out comprehensive comparative research of thermal degradation and inflammation parameters of timber covered with fire resistant biological flame retardants of different chemical composition. We also looked at the efficiency and the action mechanism of the latter. Materials and methods. As the objects of research, the means were selected – phosphorase-containing water-soluble compounds of the nanoscale series, complex biocides and special bioplasticizers (Agent 1) and water-soluble nanoscale diammonium hydrophosphate (Agent 2) applied to pine wood by surface treatment and deep impregnation methods. Results and discussion. Thermogravimetric studies of wood treated with flame retardants have shown that its decomposition occurs in the following temperature ranges: 30–150°C – the process of loss of moisture by wood; 150–400°C – the effect of protective mechanisms of the compositions, as well as the process of decomposition of the main components of wood (hemicellulose, cellulose, lignin) and the formation of a coke layer; 400–800°C – the process of gradual burnout of the coke layer taking into account its thermophysical characteristics up to the ash residue. It has been established that both flame retardants act by the mechanism of catalytic dehydration and reduce the rate of decomposition of wood from 29 to 10%/min. Conclusion. The features of the thermal decomposition of wood protected by two different chemical composition and method of its processing means are determined. The parameters of the flammability of pine wood treated with fire-protective compounds by surface and deep impregnation were obtained, which indicate their high efficiency, which is confirmed by the values of the coke residue at 400°C, the nature of DTG peaks and DSC curves. The possibility of using the obtained materials from wood for interior decoration and cladding of facades of buildings that meet regulatory requirements for their safe use is shown.
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Study of the effect of additives on biodegradation of PVC materials
Статья научная
Modern operating conditions of polyvinyl chloride (PVC) materials impose increased requirements for the additives used. Intensification of processing and expansion of PVC application areas, as well as providing a wide variety of its performance characteristics, are associated to a large extent with the successful solution of the problem of creating effective plasticizers. Therefore, when developing formulations of PVC plasticates, it is important to obtain and select plasticizers that meet modern high requirements for operation and environmental safety. One of the modern approaches to creating materials that can be destroyed in natural conditions is based on the use of additives that increase the ability of polymer materials to biodegrade. This paper presents the results of developing a PVC composition with increased biodegradation. For this purpose, a mixture of plasticizers was used: dibutoxyethyl phthalate (DBOEP) with a degree of ethoxylation of 1.5 and dibutoxyethyl adipate (DBOEA) with a degree of ethoxylation of 1.5. The results of testing samples of obtained PVC compositions for biodegradation are presented. It is shown that partial replacement of a phthalate plasticizer with a non-toxic biodegradable dibutoxyethyl adipate makes it possible to obtain PVC compositions with increased biodegradation, while maintaining excellent performance properties.
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Study of the kinetics structure formation of cement dispersed systems. Part I
Статья научная
Introduction. The study of the kinetics structure formation is rarely the subject of a careful study. Although it is important for materials used to create elements of building structures, energy elements, thermoelements and materials for other purposes. The article proposes refinements of the methodology for determining the parameters of the kinetics structure formation of cement composites, including modified compositions. Methods and materials. The structure formation of cement systems with plasticizers, microsized mineral additives (hydrosilicates of barium, copper and zinc) and nanosized particles of zinc hydrosilicates has been studied. Results and discussion. It is proposed to single out two stages of initial structure formation: the stage of setting the cement paste and the stage of hardening. The selection of the setting stage is connected with the natural laws of the development of natural systems, namely, the initial formation of a structural grid obeys an exponential law. Moment of time when a deviation from this law is observed is the time of occurrence of spatial and/or prescription difficulties that hinder the exponential development of the system. Conclusions. A strong negative relationship between the parameters φ and β of the equation H(t) = a exp(φt β) has been established. These parameters characterize the rate of structure formation at the setting stage (parameter φ) and the density of the structure (parameter β or the internal dimension Di, 0 associated with it). The presence of such a negative relationship indicates the inadvisability of accelerating the processes of structure formation at the stage of setting. This is supported by a strong positive relationship between the period of initial structure formation t0, s1 and the strength of the material R28.
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Study of the kinetics structure formation of cement dispersed systems. Part II
Статья научная
Introduction. The study of the kinetics structure formation is rarely the subject of a careful study. Although it is important for materials used to create elements of building structures, energy elements, thermoelements and materials for other purposes. The article proposes refinements of the methodology for determining the parameters of the kinetics structure formation of cement composites, including modified compositions. Methods and materials. The structure formation of cement systems with plasticizers, microsized mineral additives (hydrosilicates of barium, copper, iron and zinc) and nanosized particles of zinc hydrosilicates has been studied. Results and discussion. It is proposed to single out two stages of initial structure formation: the stage of setting the cement paste and the stage of hardening. It was found that the strength of the material at the stage of hardening should be influenced by an additional factor, depending on the type of the introduced substance. A strong negative relationship between the parameters α and n of the equation R(t) = Rmax(1–eatn) at the hardening stage was confirmed. The trends identified at the setting stage also demonstrated, namely: an increase in the rate of structure formation leading to the formation of a less dense structure. Conclusions. An analysis of the change in the value of the internal dimension of the system during the transition from the stage of setting to the stage of hardening made it possible to identify two trajectories of the system development. The first trajectory appears only by combining the elements of the structure (trajectory No. 1). Preservation of the characteristic dimensions of structural elements, but an increase in the proportion of elements with small dimensions (when the conditions that prevent the combination of elements of the structure are realized) describes the second trajectory (trajectory No. 2). The implementation of trajectory No. 2 is typical for compositions which the structure formation of cement stone is carried out in the presence of Melment F15G plasticizer or microsized particles of copper or zinc. For other studied compositions, structure formation is proceeding with the enlargement of structural elements.
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Study of the properties of nanomaterials
Статья научная
To improve physical and mechanical properties of pavements new materials with nanomodified additives are being actively developed. The authors are investigating the properties of road petroleum bitumen with nanomaterial Taunit. At the initial stage, oil bitumen was heated to 100о C. Then carbon nanomaterial «Taunit» was added. After that, the mixture was stirred in an ultrasonic homogenizer until even distribution of the carbon nanomaterial in the total volume. The process of cooling of the final structure was carried out until the end of the crystallization process. Then, the specimens are exposed to tension and strength tests with a constant rate of deformation or loading until the moment of rupture on the testing machines. Mixing with other components of asphalt concrete in the standard mode follows the nanomodification of the bituminous mixture. Under increased temperatures the bitumen mixture keeps properties of an effective binder. It was revealed that the modified carbon bitumen has good thermal properties, namely, it has a higher softening temperature (Δt is in the range from 6 to 10ºС). The indicator, which indirectly characterizes the degree of hardness of bitumen solutions, is within the limits of GOST standards, decreases by 15–20%.
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Study of the stability of zeolite suspensions for cement systems
Статья научная
Introduction. In Russia, the focus of scientific research in the construction industry is on the development of new materials with high functionality, durability, and strength. These materials also have various unique properties that make them suitable for a wide range of applications. Fine dispersed additives are used in the binder, for the construction of objects that require increased strength, or for repair work where early strength gain of the repair mixture is important. To improve the physical and mechanical properties of the hardened cement paste, which contains finely dispersed additives, it is necessary to consider the issue of uniform distribution of submicron particles in the volume of the cement composite. The study of this issue is one of the objectives of this study. Materials and methods. Fine dispersed zeolite, which has high ion-exchange, sorption, catalytic properties, was selected as the object of study, and the possibility of its introduction into the cement composition in the form of a stabilized suspension instead of mixing water was assessed/ Zeolite suspension with concentration of 10, 30, 50 g/l was prepared by mechanical stirring with a magnetic stirrer and ultrasonic dispersion under thermostatted conditions. The time of mechanical and ultrasonic treatment of suspensions was 20 min. Suspensions were prepared in two dispersion media – water and water-polymer (water + plasticizer). Physicomechanical tests of samples were carried out in accordance with current national and international standards and methods. Results. Studies of sedimentation stability of suspensions showed that the most stable suspension was stabilized by ultrasonic treatment and plasticizer. The sedimentation velocity of suspension particles in the first period was (3.43÷3.83)•10–6 m/s, in the second period – (0.98÷1.17)•10–6 m/s. The study of zeolite particle dispersion in suspensions showed that ultrasonic dispersion leads to a more significant shift in particle dispersion downwards from 25 μm to 3 μm, both in aqueous and aqueous-polymer suspensions with a concentration of 10–30 g/l. The conducted physical and mechanical tests of the samples showed that the introduction of an ultrasonic-stabilized aqueous-polymer zeolite suspension into the cement composition results in an increase in the initial and grade strength by 3.3 times and 51%, respectively. The analysis of the results for compressive strength showed the greatest efficiency when introducing a zeolite suspension into the cement composition instead of mixing water in an amount of 10–30 g/l. Conclusion. The studies conducted have shown the effectiveness of using ultrasonic treatment in combination with a plasticizer to stabilize the zeolite suspension. Stabilized zeolite particles, uniformly distributed in the volume of the cement matrix, act as a substrate for the nucleation and growth of crystal hydrate phases, thereby intensifying the process of hydration and formation of a crystal hydrate framework with a dense and strong structure of cement stone. Thus, the feasibility of considering zeolites as components of composite materials is a promising direction in solving multifaceted problems in the construction industry.
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Статья научная
Introduction. As part of the solution for the problem of creating a new class of materials for building additive technologies, cement composites reinforced with high-strength fiber, this work presents the results of experimental studies of the strength of the adhesive bonding between cement matrices and reinforcing fibers with different chemical compositions, diameters, and tensile strength. Materials and methods. Rheological properties of cement systems were studied using shear and squeeze rheometry, the method of micromechanical testing for determining the strength of the adhesive bonding “cement matrix – reinforcing fiber” based on the pull-out test, which involves pulling out the fiber from the cement matrix layer; after the pull-out test for all the studied systems, the microstructure of the contact surface “cement matrix – reinforcing fiber” was assessed using a Thermo Scientific™ Phenom ™ Desktop SEM scanning electron microscope; the compressive strength of hardened cement paste-samples was determined using an INSTRON Sates 1500HDS testing machine. Results and discussions. It was established that the combination of strength characteristics of matrices, fibers, and adhesive strength at their interface allowed securing the required strength characteristics of reinforced construction composites. In the “cement matrix – carbon fiber” systems, the value of adhesive strength was 9 – 11 MPa; in the “cement matrix – steel wire” systems, the value of adhesive strength was 3 – 4 MPa. Conclusions. Matrices with viscosity modifiers containing nano- and micro-sized particles of SiO2 (complex nano-sized additive and metakaolin) are reasonable options for combinations of the “cement matrix – reinforcing fiber” components. Carbon fiber and steel wire are recommended to be used as reinforcing fibers.
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Study of thermal effect based on liquid crystal nanoparticles
Статья научная
Introduction. Currently, the development of composite systems doped with nanoparticles and based on liquid crystal (LC) media is being actively pursued. The latter, having unique properties, can be used to improve various LC devices. For this purpose, it is very important to investigate the mechanism of change in the properties of liquid crystal systems from the size and concentration of nanoparticles. Recently, a sufficient number of methods have been applied to measure the flow of liquid or gas based on different physical principles. Information about the average mass flow rate of a liquid or gas can be obtained by a measurement method based on steady-state heat injection into the flow. The average flow velocity can be measured by electromagnetic and ultrasonic sensors, while the average volume flow rate can be measured by hydrodynamic (aerodynamic) as well as mechanical turbine methods. In heat transfer and mass transfer, convective motion in a fluid medium plays an important role in the vast majority of natural phenomena and technological processes. Many processes of convective mass transfer and heat transfer in chemical, petrochemical, construction, nuclear and other industries are carried out in heat pipes. Up to the present time the question about efficiency of heat pipes application with bodies from composite materials also remains open. In the presented work the following objectives were set: to assemble an experimental setup to study the thermal effect (flow), to conduct studies of temperature change on the surface of the conductor of the compound based on nanoparticles of liquid crystals and viscosity of liquid crystals from the concentration of nanoparticles. Methods and Materials. In this experimental work, a heat flux acts in the region of the outer boundary of the conductor. Note that the redistribution of the thermal field is influenced by such processes as heat conduction and heat transfer. To observe the thermal effect, compounds based on liquid crystal nanoparticles were used. Nanostructured liquid crystal systems have a unique property as fluidity inherent in ordinary liquids. For opaque conductor walls, a method for determining the direction of heat flow is proposed. Earlier experimental studies have shown that temperature measurement is possible only by pyrometric method. Therefore, the redistribution of temperature change on the conductor flow surface was recorded using an optical pyrometer that perceives thermal (infrared) radiation. In this work, a compound based on liquid crystal nanoparticles, namely with the addition of cholesteryloleate, was used as a base. Results and discussion. In the course of the study, temperature dependences in the heat flow zone of the conductor in the absence and in the presence of liquid motion were experimentally obtained. Dependences of temperature change on the surface of the conductor with compounds based on nanoparticles of liquid crystals have been measured. Inhomogeneous redistribution of the thermal field is shown. The results of the study of the dependence of the viscosity of nematic liquid crystals on the concentration of nanoparticles are presented. Conclusion. The above data show that the thermal effect on the surface is not uniformly distributed. For visualization of the thermal effect, compounds based on nanoparticles of liquid crystals turned out to be more effective. A technique has been developed to determine the direction and calculate mathematically the magnitude of the liquid heat flux in the opaque conductor flow. It should be noted that the viscosity of liquid crystals changes when nanoparticles are coupled.
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Статья научная
Introduction. Particular interest for research has dispersed systems. Dispersed systems are multiphase systems, consisting of a quantity of smallest particles, evenly distributed in the liquid, gaseous or solid medium. Such systems are the majority of the real bodies around us: soil, bodies of plant and animal life, clouds and fogs, many industrial products, such as building materials, metals, polymers, paper, leather, fabrics and foodstuffs. Disperse systems have many unusual physical properties, which require separate study and are of great importance in practice. Methods and materials. This article explores the influence ion-forming additives on the thermophysical properties of paraffin-containing disperse systems. The widespread use of ion-forming additives is associated with a number of positive features. Ion-forming additives is a new type of modifiers of crystalline solid phase and liquid crystals, significantly affect the process of micelle formation of paraffin in dispersed paraffin-containing environment. Therefore, studies on their effect on the processes of nucleation and growth of crystals are of particular interest. During the research, samples were prepared with various ion-forming additives and obtained temperature dependences of dielectric permittivity for dispersed systems petrolatum – methyl ethyl ketone – water solution of NaCl and KCl. Polynomial models are selected as the model type, which are widely used in the processing of various data, including experimental, and are also an effective tool for solving a wide range of scientific and technical problems. Results and discussion. It has been established that an increase in the degree of crystallinity of the solid phase with the introduction of additives is associated with a decrease in surface tension and increase in secondary nucleation. Resulting universal regression dependence of permeability allows us to describe the experimental results with the reliability of the approximation 0.99. Conclusion. The analysis of the obtained results shows reliability of the considered regression models and their applicability in practice, as well as in further studies of the dynamics of the process in disperse systems and the process of nucleation and growth of crystals.
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Study on the influence of zeolite nanoparticles on selected properties of portland cement
Статья научная
Introduction. Cement microstructure imaging is an emerging field of non-destructive compositional investigation. Some data may be available via one method but not the other due to various physical and chemical mechanisms that could cause cement decay. In order to quantitatively and qualitatively evaluate cement stone, it is necessary to investigate it as a complex multi-phase composite material, identify its crystalline phases, and estimate the precise size of its nanoparticles. Materials and methods. This work presents the results of a microscopic study of the effect of Nanozeolites (particle size ≤ 100 nm) on cements for cementing wells. To study the surface properties (chemical bonds between molecules, analysis of mineral composition, and surface topography and morphology) of class G cement stone, three types of microscopes – IR spectrum, X-ray diffraction (XRD), and atomic force microscopy (AFM) – were used. Zeolite nanoparticle additives were introduced at varying concentrations (0.5%, 1%, 1.5% by weight of cement) after 8 hours of curing in a water bath at atmospheric pressure and a heating temperature of 60оC (140оF). Results and discussion. The infrared spectra revealed changes in surface properties, indicating a decrease in free water and an increase in the strength of the system with the addition of nano zeolite. X-ray diffraction method (XRD) allowed for the identification of the main phases of crystalline hydration. The highest peak intensity is due to calcium hydroxide CH, which decreases with the addition of nano zeolite. This phenomenon elucidates the pozzolanic behavior of nano zeolite, which reacts with precipitated calcium hydroxide upon hydration to form C–S– H, reduces the calcium hydroxide content of the layered structure and increases C–S–H. The topography and surface morphology of the samples were studied at the nanoscale using atomic force microscopy. The images show the nanoparticles propagate along the cracks and appear to increase the surface layer's resistance to deformation and stress relaxation in cement-based materials. In addition, they promote viscoelastic C–S–H behavior. Conclusion. Adding nano zeolite to Portland cement affects the process of early hydration of cement stone and increases its early strength. Additionally, the introduction of 1.5% nano zeolite into cement results in the formation of irregular peaks and valleys of low porosity filler, ultimately enhancing the cement's strength.
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Статья научная
Introduction. Literature analysis and patent search revealed that basalt rock and its fibers have exceptional physical and technical characteristics and alongside abundant raw material reserves. Based on this, the use of basalt rocks and their fibers as a material for the development of advance composite materials with high performance characteristics is a promising direction. Diverse technological fields and economic sectors, as well as various material requirements, necessitate a spectrum of systems, compositions, and properties for basalt and its melts, whether for generating superthin or continuous fibers. Methods and materials. The chemical and mineralogical compositions of some basalt rocks from deposits in the Kyrgyz Republic were studied to determine their suitability for production of superthin fibers and continuous fibers. The acidity modulus and fusibility modulus were determined by calculation based on the chemical composition of basalts of the Kyrgyz Republic. Among them, the quality of basalts from the Suluu-Terek deposit and basalts from the Toru-Aigyr deposit fully meets the requirements for the quality of raw materials for creating the production of basalt superthin fibers (BSF) and basalt continuous fibers (CBF). In the research we used physical and chemical analysis methods to determine the chemical and mineralogical composition of basalt. By calculating the acidity and fusibility modulus of basalt raw materials from the Kyrgyz Republic, as well as comparing them with relevant standards, their suitability for the production of basalt superthin fiber (BSF) and basalt continuous fiber (CBF) was established. The object of the study was the basalts of the Sulu-Terek deposit. Results of the study include an analysis of the chemical and mineralogical compositions of certain basalt rocks from deposits in the Kyrgyz Republic in order to assess their suitability for the production of superthin and continuous fibers. The acidity modulus and fusibility modulus of basalts of the Kyrgyz Republic were determined by the calculation method. Among them, it was revealed that the quality of basalts from the Suluu-Terek deposit and basalts from the Toru-Aigyr deposit fully meets the requirements for the quality of raw materials for the production of basalt superthin fibers (BSF) and basalt continuous fibers (CBF). Conclusion. The suitability of basalt rocks from various deposits, especially Suluu-Terek, Taldy-Bulak and Kashka-Suu, was confirmed, with recommendations for use. The results also highlight the importance of compliance with standards when selecting deposits and setting production parameters.
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Surface activity of concrete waste powders
Статья научная
Introduction. One of the most large-tonnage wastes of the construction industry is a concrete scrap, obtained as a result of the dismantling of buildings and structures, the service life of which has reached its maximum or requires significant capital changes. In our opinion, works on the use of the resulting dust-like fraction are of particular interest. One of the promising methodological approaches in this direction is the observance of the principles of nanotechnology, which consists of obtaining finely dispersed components as active components of the created compositions. Materials and methods. Therefore, the objects of research in this work were fine powders obtained by mechanical grinding of lightweight (sample 1) and heavy (sample 2) concrete of a five-story residential panel house built in 1979. The elemental composition and specific surface area of the samples were determined, thermogravimetry of the studied powder systems was carried out, the surface tension of the experimental samples and the dispersion and polarization components of this indicator were determined by the OVRK method. A new methodological approach to the determination of the surface tension of powder systems is proposed, based on the determination of the functional dependence of the surface tension on the pressing force of the prototypes. The possibility of calculating macroenergy characteristics (atomization energy, specific mass atomization energy) of waste concrete samples is shown. These physicochemical indicators characterize the potential supply of internal energy of the system, which is capable of transforming into free surface energy during mechanical destruction of the material. Results and discussions. Thermogravimetric analysis of experimental concrete samples showed the presence of a residual amount of belite. Calculations of the surface activity of the samples showed that it is more preferable to use a powder obtained by crushing a sample of heavy concrete as an active additive in compositions capable of exhibiting the properties of a binding agent. Conclusions. To assess the activity of dusty fractions of concrete scrap as a component in binding compositions of the hydration type of hardening, it is proposed to use the value of the surface activity of powder systems as a criterion. The absolute numeric value of this criterion is equal to the ratio of the values of the free surface energy of the investigated powder and the specific mass energy of atomization of the initial waste concrete. It was found that for concrete waste the value of this criterion is determined by the polarization component of surface tension.
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Introduction. Recent years have seen a pressing need to dispose of municipal solid waste due to rapid urbanization. The municipal solid waste incineration fly ash (MSWIFA) produced from solid waste incineration power plant exhibits pozzolanic properties and poses concern of toxicity leaching when used directly as building materials. This paper presents an alkali-activation method to produce sustainable alkali-activated MSWIFA materials (AAFMs) with various MSWIFA dosages and investigate the corresponding fabrication and performance. Materials and Methods. Composited alkali activators activate the MSWIFA with constant alkalinity of 5% and the molar ratio of Si/Na = 0.86. The resulting geopolymers' bulk densities, mineral composites, morphology, and compression strength are thoroughly examined. Results and discussions. Results show that the use of MSWIFA may lead to more loose structures because the bubbles are generated from metallic aluminum and alkali activators. Additionally, the production of multiple crystals also accounts for increasing porosity. The generated multi-crystals such as Sylvite, Halite, Hydrocalumite, Calcium Hydroxide, and Ettringite are further detected from the morphology and mineral analysis. Furthermore, compression tests and toxicity characteristic leaching procedures (TCLP) are conducted to investigate the mechanical performance and heavy metals solidification performance of AAFMs, with an optimal compression strength of 19.99MPa at 28 days for AAFM-10 while toxicity leaching is subject to regularity limits. Conclusions. This study shows that great potential of using the alkali-activation method to recycle hazardous municipal solid fly ash into construction materials with both ecological safety and high performance.
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