Nanotechnologies in Construction: A Scientific Internet-Journal @nanobuild-en
Статьи журнала - Nanotechnologies in Construction: A Scientific Internet-Journal
Все статьи: 591
Статья научная
Introduction. The production of plasticizing additives using nanoparticles for the construction industry represents a promising sector in the development of advanced building materials. By incorporating nanoparticles, such as silicon dioxide, into complex additives, it is possible to significantly enhance the structural and mechanical characteristics of cement-based systems, resulting in increased strength, durability, and resistance to external forces. This study aims to investigate the process of synthesizing silicon dioxide nanoparticles in aqueous media and creating a complex organic-mineral additive comprising phloroglucinol- furfural oligomers with silicon dioxide nanoparticles. Materials and methods of research. A modifier based on phloroglucinol-furfural oligomers was used as an organic component of the complex additive. To synthesize silicon dioxide nanoparticles, which are the mineral component of the additive, liquid glass (sodium silicate solution) was used. Additionally, Aerosil, with a specific surface area of 2,000 m3/kg, was used as the dispersed phase in the organic mineral additive to study the compatibility of the components and the mechanism of their interaction. The particle and size distribution were determined using laser light diffraction on the Malvern Mastersizer 3000 device and dynamic light scattering on the Microtrac S3500 device. Microscopic analysis of the complex additive was performed on a TESCAN MIRA 3 LMU scanning electron microscope. The chemical structure and composition of the obtained additive were monitored by UV and IR spectrophotometry on Specord 200 Plus and Alpha Bruker Optics devices, respectively. Results and discussion. The article presents the results of the development of a method for the synthesis of silicon dioxide nanoparticles and creating an organic-mineral additive based on phloroglucinol-furfural oligomers containing these nanoparticles. The additive is designed for use in mineral suspensions in construction additive technologies. It has been shown that it is possible to obtain nanoscale particles of silicon dioxide through the hydrolysis of sodium silicate. It has been demonstrated that as the concentration of sodium silicate increases, the number of silica particles increases significantly, the number of silicon dioxide particles increases significantly. This leads to faster coagulation of the particles, resulting in the formation of larger aggregates. It has been shown that silicon dioxide particles smaller than 10 nm can be obtained through acid titration. During the maturation period, particles increase in size by about 7 times over a period of 1 to 7 days. The optimal ratio for particle synthesis should be considered to be a 2:1 ratio of reagent solutions (sodium silicate to hydrochloric acid) by volume. It is shown that the introduction of the specific additive at the stage of particle formation can help to stabilize their growth. Conclusion. The complex organic-mineral additive based on a phloroglucinol-furfural oligomer and silicon dioxide nanoparticles has been developed. It has been established that the introduction of the specific additive in the process of synthesis of silicon dioxide particles contributes to an increase in the aggregate stability of the dispersed system of the complex additive, reduces the tendency of particles to enlargement and sedimentation.
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Статья научная
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
Статья научная
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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Production method of nanostructured wood-polymer composition with microwave application
Статья научная
Introduction. Currently, wood-polymer compositions (WPC) are widely used in the national economy and construction. The composition of WPC varies widely depending on the further purpose. Improving the binding quality in the wood-polymer system is one of the promising areas for enhancing operational characteristics. Organic and inorganic substrates nanostructured with individual substances, including metal particles, are used as binding components. In the petrochemical industry, most high-capacity productions use catalysts based on active carriers like heavy metals when developing targeted products for various purposes. After several stages of regeneration, recovering these heavy metals becomes impossible. Consequently, spent catalysts accumulate in sedimentation tanks and sludge collectors, lacking an efficient method for disposal and secondary use. One of the components included in the composition of spent catalysts is chromium (+6), which belongs to carcinogenic metals. Numerous disposal methods are currently inadequate for neutralizing this metal on an industrial scale, which is of interest for research. Methods and materials. The study is aimed at converting carcinogenic chromium (+6) into non-carcinogenic chromium (+3) by ultrahigh frequency exposure (microwave), which will open up opportunities for its use as a chromium-containing nanocomplex binding a tree-polymer. Results and discussions. The ultrahigh-frequency effect on the mixture of wood-polymer composition and spent chromium (+6) causes an increase in the penetration depth of high–frequency waves, characterized by a uniform distribution of energy over the entire area of the composite, which is explained by the reduction of chromium (VI) oxide into chromium (III) oxide, and there is also a change in the color of the nanostructured wood-polymer composition (WP – compositions) from yellow to malachite. Conclusion. This study, which consists in the application of microwave exposure to the wood-nanoparticle-polymer system, confirms the receipt of a durable construction product and its use in the construction of roofs, facade boards, sidewalks, piers, port facilities, etc.
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Production of a nanostructured bitumen modifier in the reprocessing of automobile tires
Статья научная
Introduction. Polymer-bitumen binders are innovative nano-binders for asphalt concrete pavement. Introduction of a polymer modifier improves the characteristics of bitumen and asphalt concrete. The use of waste tires rubber for bitumen modification is considered to be an environmentally friendly solution, but it is limited due to the poor cosite of rubber with bitumen. Various methods based on activation of the rubber surface, dispersion of rubber to nanosized particles, and thermochemical transformations of rubber into individual organic compounds are known to overcome this limitation. Methods and materials. The method of joint pyrolysis of rubber with oxygen-containing oil under pressure is proposed to be used for converting it into a nanostructural bitumen modifier. The resulting product is studied by the methods of thermogravimetry, NMR-spectroscopy, chromatomasspectrometry, scanning electron microscopy and solubility in toluene. Results and discussion. It has been established that during joint pyrolysis rubber undergoes devulcanization, cracking and dispersion to nanosized particles, and as a result the product becomes compatible with bitumen. Thermochemical reprocessing of waste automobile tires can be considered to be a promising method for the production of a nanostructured bitumen modifier. Conclusion. The use of thermochemical pressure treatment of waste tire rubber in the presence of oxygen-containing oil makes it possible to obtain a nanostructured product compatible with bitumen for further use of the resulting modifier in the production of asphalt concrete.
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Статья научная
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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Properties of Nano Engineered Concrete Subjected to Accelerated Corrosion
Статья научная
Introduction. Many research had worked on improving the performance of concrete subjected to severe environment and improve concrete corrosion resistance. Using nano-materials is one of the methods had been used recently to improve concrete properties. In this research, a comparison between the performance of nano-silica and nano-clay in enhancing the durability properties of concrete was investigated. Methods and Materials. The experimental program was carried out through examining water absorption, water permeability, rapid chloride penetration test, corrosion resistance, bond strength of steel rebar before and after subjected to corrosion, and finally microstructure test. Nano-silica and nano-clay were added at 1%, 3%, and 5% as a partial replacement by weight of cement. Results. Both nano-silica and nano-clay showed significant performance in reducing the permeability and porosity of concrete and improve corrosion resistance of concrete. For comparison, nano-clay had a significant impact than that of nano-silica on concrete properties; in which the water permeability resistance of nano-clay mixes was enhanced by 87% than that of the control mix, while for nano-silica, it was 51% only. The chloride ion penetration was reduced by 72% for nanoclay mixes, while in nano-silica was 28%. Discussion. Nano-clay had a significant effect than that of nano-silica on the concrete durability properties; the flat-shaped of nano-clay particles had improved the microstructure of the cement matrix through the damping effect, besides the filling effect through the microstructure of the matrix which reduces the chloride ion penetration and improves water absorption and permeability of concrete. Conclusion. The optimum percentage of nano-silica is 1% by weight of cement as a partial replacement of cement by weight. However, for nano-clay is 5%, which gives the best performance in improve the durability properties of concrete.
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Properties of porous heat-resistant composition materials. Part I
Статья научная
This article is a continuation of a series of articles on the production of porous composite nanomaterials. This paper presents an overview of the properties of porous, heat-resistant inorganic composite materials. The physicochemical and mechanical characteristics of various porous refractory materials produced industrially are presented. A separate class of materials with a regular and quasi-regular porous structure is considered. Such materials include the so-called cellular or «lattice» materials, that are becoming widely applied in modern industry. An example of such materials is ceramic foam – a sintered ceramic material with a foamy cellular structure. A special group of materials with opal pore structure has been also focused. Synthetic opals have received intensive development in recent years because they are model objects for the development and research of new spatial-periodic structures with nonlinear optical properties. Such structures include composites based on classical and inverted opals, in which the pores are filled with various dielectric, semiconductor, or metallic substances. The optical properties of these systems are determined by the size of the close-packed particles, as well as the dielectric constant of the components.
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Properties of porous heat-resistant composition materials. Part II
Статья научная
This article is a continuation of a series of articles on the production of porous composite nanomaterials. This paper presents an overview of the properties of porous, heat-resistant inorganic composite materials. The physicochemical and mechanical characteristics of various porous refractory materials produced industrially are presented. A separate class of materials with a regular and quasi-regular porous structure is considered. Such materials include the so-called cellular or «lattice» materials, that are becoming widely applied in modern industry. An example of such materials is ceramic foam – a sintered ceramic material with a foamy cellular structure. A special group of materials with opal pore structure has been also focused. Synthetic opals have received intensive development in recent years because they are model objects for the development and research of new spatial-periodic structures with nonlinear optical properties. Such structures include composites based on classical and inverted opals, in which the pores are filled with various dielectric, semiconductor, or metallic substances. The optical properties of these systems are determined by the size of the close-packed particles, as well as the dielectric constant of the components.
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