Nanotechnologies in Construction: A Scientific Internet-Journal @nanobuild-en
Статьи журнала - Nanotechnologies in Construction: A Scientific Internet-Journal
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Статья научная
Introduction. The simplest and most common method of obtaining fine mineral powder is mechanical dispersion. In the process of grinding the material went through some work (energy), which is spent on the formation of a new surface. Therefore, it is not always clear whether the destruction of the crystal lattice of a solid lead to the activation of the resulting crushed material. Thus, the key characteristics of finely dispersed mineral powders, by which activation processes can be judged, are the value of the specific surface area (Ssp) and the specific free surface energy, numerically equal to the surface tension (σ) of the solid. Therefore, a number of models based on the determination of these characteristics have been proposed to estimate the mechanical activation process of the raw material. So, one of the most correct methods, in our opinion, is the method based on an energy approach to the evaluation of mechanical activation processes. This model determines the relative change in the free surface energy (ΔES/ES0) of the material when obtaining a dispersed system. At the same time, the choice of the most effective raw materials for obtaining composite binders can be carried out on the basis of the surface activity criterion (ks), which is used as a criterion characterizing the reactivity of fine mineral powders after their mechanical disintegration. Therefore, the aim of this study was to calculate the relative change in the surface energy of fine mineral powders of various raw materials and to identify possible functional relationship between the parameter ΔES/ES0 and the amount of surface activity for the studied rock systems. Methods and Materials. Sedimentary rocks formations the Arkhangelsk region were selected as materials for the research: polymineral sand and saponite-containing material (a representative of bentonite clays). Before conducting experiments, rock samples were brought to a constant mass at a temperature of 105оС. The chemical composition of the samples was determined on an X-ray fluorescence analyzer “Metexpert”. Highly dispersed rock fractions were obtained by dry grinding on a planetary ball mill Retsch PM100. The dimensional characteristics were determined using the DelsaNano submicron particle size analyzer by photon correlation spectroscopy. The specific surface area was determined by the gas permeability method on the PSX-10 device. To calculate the surface tension, the edge angle was measured on the “Easy Drop” installation. The surface tension for highly dispersed samples was calculated by the OWRK method. Results and Discussion. The calculated macro-energy characteristics of the studied samples have showed that the atomization energy for polymineral sand was 1910.72 kJ/mol, and for saponite–containing material was 1826.94 kJ/mol. At the same time, the mass specific atomization energy for sand and SCM are 30.41●103 kJ/kg and 26.94●103 kJ/kg, respectively. In the process of dispersion, several fractions of highly dispersed rock powders were obtained, which are characterized by an average particle size and specific surface area. The surface tension (and its components) calculated by the OWRK method showed that for all the samples studied, the polarization effect (σS P) prevails over the dispersion interaction (σS D). At the same time, as Ssp increases, the numerical value of the ratio σS P/σS D increases. This indicates an increase in the number of active surface centers associated with the redistribution of the energy potential of the system. The calculated values of free surface energy (ЕS), surface activity (ks) and the relative change in free surface energy showed, that ks and ΔES/ES0 increase as the duration of powder dispersion increases.The obtained functional dependences ks = f(ΔES/ES0) for the studied samples of polymineral sand and saponitecontaining material are linear in nature and obey the general equation у = a●x + b. In this case, the coefficient “a” characterizes the dynamics of changes in the reactivity of the material with an increase in the duration of mechanical grinding, and the parameter “b” – reactivity in the microstate. Comparison of the coefficients “a” of the studied dispersed systems showed that, unlike polymineral sand, the reactivity of saponitecontaining material increases 1.5 times faster as the grinding duration increases. The obtained functional relationship between the criteria used for evaluating the process of mechanical activation of mineral raw materials of various natures shows the correctness of the models used. Conclusion. The calculated macro-energy characteristics of rock samples showed that the atomization energy for polymineral sand and saponitecontaining material has similar values. To assess the effectiveness of the process of mechanical activation for mineral raw materials, it is proposed to use the relative change in free surface energy or surface activity.
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Regulation of the aggregate stability for binary polymer-mineral dispersions
Статья научная
Introduction. In the binary dispersed systems of different origins (mineral and polymer) with particles differing in size by an order of magnitude, heterocoagulation is observed. Regulation of the aggregate stability is crucial in controlling the properties of functional dispersed materials based on such mixed dispersions. This study focuses on the investigation of waterborne mono and binary dispersions of polyvinyl acetate, Portland cement, and chalk by means of static laser light scattering and optical microscopy. Materials and research methods. In order to investigate the action mechanism of the FF modifier based on phloroglucinol furfural oligomers as disperse phase we used chalk (CaCO3 – chalk dispersed technical MTD-2, LLC “Technostroy”, Kopanishchenskoe deposit), Portland cement CEM I 42.5N (JSC “Belgorod Cement”), and polyvinyl acetate (LLC “Kuban-Polymer”). Particle distribution and the aggregate stability of dispersions were studied with an Analysette 22 NanoTecplus device. The particle sizes were determined by optical microscopy with “Axio.Scope.A.1” microscope, and the adsorption of oligomers on the particles of dispersions was analyzed using a UV spectrometer (SPECORD UV). Results and discussion. It has been established that the phloroglucinol furfural modifier contributes to the stabilization of binary polymer-mineral dispersions. Integral and differential distribution curves of polymeric particles have been obtained in a wide range of 0.01–2100 μm. Research has shown the regularity of the modal diameter reduction of adsorption-modified particles with a transition from a narrow to a wider distribution with the absence of large coagulums. Conclusion. The hypothesis has been proposed that the adsorption-solvation factor of aggregate stability makes a significant contribution to the aggregate stability of binary polymer-mineral dispersions. The impact of this factor is different for mono-mineral and binary polymer-mineral dispersions and depends on the hydrophilicity of the surface, increases with the transition from mineral surface to the polymer surface as the Hamaker constant increases.
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Статья научная
Introduction. To improve the performance properties of lime coatings, modifying additives are introduced into their formulation. The development of a technology for the synthesis of an additive containing calcium hydro- and aluminosilicates, which promote the binding of lime and increase the resistance of the lime composite, is of current interest. Materials and methods. To prepare an additive based on a mixture of hydro silicates and calcium aluminosilicates, liquid sodium glass (GOST 13078), technical (purified) aluminum sulfate (GOST 12966), and quicklime were used. The pozzolanic activity of the materials was determined by the absorption of lime from lime mortar. Results. It has been established that the mineralogical composition of the additive obtained at the 1st stage of synthesis is represented by hydro silicates of the tobermorite group. The mineralogical composition of the additive obtained at the 2nd stage of synthesis is represented by hydro silicates of the tobermorite group, gypsum, and calcium aluminosilicates. The particle size of the additive is from 10 to 40 μm. The pozzolanic activity of the additive obtained at the first stage of synthesis was 238.6 mg/g, and that obtained at the second stage of synthesis was 3.2 times higher and amounted to 762.5 mg/g. The introduction of an additive obtained at the 2nd stage of synthesis into the composition increases the compressive strength of lime composites by 2.87 times. Conclusion. It is proposed to use a modifying additive obtained by a two-stage synthesis technology in heat-insulating DBM. The optimal concentration of the proposed modifying additive is selected, which is 10% by weight of lime.
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Статья научная
Results of a research of efficiency of sorbents on the basis of the waste of production and processing of micaceous quartzites (MQ), montmorillonite clays (MC) modified by humic connections (HC), received by extraction of waste brown coal are shown. Chemical composition of mica quartzite processing waste depending on the fraction size was previously investigated: element structure by method of the power-dispersive X-ray fluorescent analysis and mineral structure by method of X-ray phase analysis, for purpose of interrelation establishment between the structure of fraction and adsorptive properties of the received composite sorbents and also for the purpose of an exception as a part of MQ and, respectively, a sorbent of dangerous and toxic substances I-III of hazard classes. The efficiency of adsorption of the obtained sorbents was studied, an increase in sorption activity was found depending on composition of sorbent and method of modification (preliminary temperature processing and drawing on a surface of a sorbent of HC nano- and a microdimensional layer). It is determined that the greatest efficiency of adsorption of ions of heavy metals is observed for the sorbent which underwent temperature modification at 800оC and then HC covered with a layer up to 1% of masses. Use of waste of MQ containing 40–60% of quartz (SiO2) in composition with MC and with further modification of a surface (up to 1% of masses.) humic connections will allow receiving highly effective, universal and inexpensive sorbents for sewage treatment from heavy metals and other pollutants. The offered composite sorbents will allow to solve several ecologically important problems in a complex: to carry out effective purification of industrial sewage (machine and instrument-making, metallurgical, petrochemical and other enterprises) of heavy metals ions and to utilize waste of micaceous quartz processing of and brown coal extraction.
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Статья научная
Introduction. Phenols and petroleum products are common wastewater contaminants in many industries. Due to their persistence and toxicity in the natural environment, an efficient waste disposal technology is needed. Ozonation in the presence of heterogeneous catalysts is one of the advanced methods for treating wastewater from these toxicants. Since most catalysts are expensive, they are being sought on the basis of transition metals and their oxides, which have high activity and relatively low cost. In this regard, the Scientific and Educational Center for Innovative Technologies (SECIT) of USPTU carried out work on the search for an effective and affordable catalyst for the deep oxidation of phenol and petroleum products in wastewater under the influence of ozone. Methods and materials. To study catalytic ozonation, we used model waste water containing phenol and oil products at concentrations of 8 and 30 mg/dm3, respectively. Ozonation was carried out in the presence of fresh (1) and spent (2) NiO–MoO3 catalyst deposited in the form of a film on cylindrical Al2O3 granules weighing 0.5 – 2 g. Results. Optimal conditions of ozonation have been found (1), within 10 min of the decomposition process in its presence, COD decreased by 25% compared to the oxidation process with a catalyst (2), and by 40% compared to classical ozonolysis. It was found that the optimal loading of catalyst (1) is 1 g, duration is 35 min, pH = 8.5, temperature – 22 – 30оC, ozone dose – 5 g/dm3. Discussion. At catalyst dosages of less than 1 g/dm3, the low efficiency of removing phenol and hydrocarbons is probably due to a lack of the adsorption surface of the catalyst. Conclusion. The studied method of purification allows to reduce the content of phenol and oil products to the standard indicator of drinking water quality (0.001 and 0.05 mg/dm3, respectively), COD by 96% and solve the problem of the harmful effects of these toxicants on ecosystems.
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Research on the impact of nano carbon fillers on the morphology of epoxy binder
Статья научная
Introduction. When developing a composite material, it is important to understand how the components included in its composition affect its properties. Fillers, by interacting with the matrix, can alter its initial structure, resulting in the composite acquiring characteristics different from the matrix. The high modifying ability of nanofillers is determined by their significant specific surface area. This allows for the total interfacial area between the matrix and the dispersed phase to be covered even with a relatively low concentration of particles, thereby enabling the use of a small amount of filler. Methods and materials. Composite materials with nano carbon fillers were investigated, including fullerenes, nanotubes, and graphene. Fractographic analysis of the tensile fracture surfaces of the samples was chosen to evaluate the structure of the composites, which allows determining the nature of the failure and the ability of the composite to restrain crack propagation. The microstructure of the composite materials, as well as the morphology of the reinforcing nano carbon fillers, were examined with a Tescan MIRA3 scanning electron microscope. Results and discussion. In a graphene composite, crack energy is dissipated through branching and elongation of the crack path. Carbon nanotubes, being embedded in the crack walls, hinder the opening of the crack edges. Crack energy is also consumed in overcoming friction forces during the extraction of nanotubes from the epoxy matrix. Agglomerates of fullerenes act as effective crack front arresters, forcing the crack to circumvent them, thereby creating new areas of fracture surfaces. This leads to an increase in the crack front length and the energy required for material failure. Conclusion. Adding nano-carbon fillers (graphene, CNT and fullerenes) as reinforcing components in the epoxy binder alters the structure. The study defines possible mechanisms for hardening of the composite materials due to adding the nano-carbon fillers.
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Resource-saving nanotechnologies in waste water treatment
Статья научная
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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Статья научная
Introduction. For handling the problem of mixtures design for additive construction technologies, the paper presents the results of experimental studies of rheological behavior and production characteristics (plasticity and shape stability) of cement mixtures based on various types of fillers with different size, shape, and grade. Methods and materials. Rheological properties of 3Dprintable mixtures were investigated using squeezing rheometry methods. The constant strain rate mode of 5 mm/s was used to evaluate plasticity and the constant load rate of 5 N/s was used to evaluate form stability. Scanning electron microscopy method (Phenom XL) was used to evaluate the size-geometry characteristics of cement and filler particles. Image processing to determine particle length and width was performed using ParticleMetric software. The size and gradation of the cement and filler particles were evaluated using a laser particle size analyser “Analyzette 22”. Results and discussion. It was found that a necessary condition for the plasticity and stability of mixtures is the creation of dense spatial packing of disperse phase particles. The values of the plasticity limit rational for extrusion are ensured if the filler particles have a size comparable to cement particles and multi-size gradation. The characteristics of the fillers are not decisive for the shape stability of the mixtures. Conclusion. The numerical criteria of fillers for design of 3D-printable mixtures have been substantiated, including mean average particle diameter, particle shape factor, particle distribution constant as a characteristic of the particle size gradation.
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Статья научная
Utilizing the unique properties of CNTs and CNFs to enhance the mechanical and fracture properties of cement based materials and develop smart cementitious nanocomposites can be a challenge in terms of developing scalable manufacturing methods. Scaling up the manufacturing size of CNT and CNF reinforced cement based materials and produce multifunctional concrete that exhibits exceptional strength, stiffness and toughness and multifunctionality requires optimization of dispersion procedure. The effectiveness of successfully using CNTs and CNFs in concrete depends on the fiber count, the volume fraction of sand and coarse aggregates. In this work, we present the flexural strength and stiffness, fracture toughness and brittleness of nanomodified pastes and mortars reinforced at amount of 0.08 and 0.1 wt% and an investigation on the optimization of the fiber count proportioning of concrete. The addition of a very low amount, 0.1 wt%, of both CNTs and CNFs, increases approximately 1.5 times the flexural strength and the Young`s modulus of concrete nanocomposites. The nanomodified concrete also exhibits 60% higher energy absorption capability.
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Self-healing cements – the key to maintaining the integrity of cement sheath. Part 1
Статья научная
To control water production, it is necessary to seal the channels of 20–25 mm thickness in the cement sheath at a depth of hundreds and thousands of meters. The most promising solution is the use of self-healing cements. The concept of self-healing materials has been known since the 1980s due to the studies of Donald Jud. The most fundamental works are by Sybrand van der Zwaag, Sheba D. Bergman and Fred Wudl, Richard P. Wool, D.Y Wu, N.R. Sottos, Erin B. Murphy, Henk Jonkers, who substantiated the concept, suggested technologies and additives to restore the integrity of polymer and cement materials. Despite active research in this area, Schlumberger is the only service company which elaborated and successfully applied the «self-healing» well cement called Futur. The authors of the article set the task of well cement modification that enables autonomous «healing» of water-conducting channels through which formation water migrates. The following materials were used in the study: polyacrylamide (PAA), water-swellable polymer (VNP V-615), sodium polyacrylate (SP), cross-linked PAA copolymers, active waterproofing mineral additives and swelling elastomers. Most of the additives have a degree of swelling of more than 150%, they effectively reduce a permeability of the cement stone, however multi-layer coating is required to control the speed of their swelling. A significant drawback of the analyzed materials was the complexity of the coating. A cross-linked AA copolymer based on anionic polycrylamide was the most effective reagent, which was easy to cover with a water-soluble shell. The cement stone with integrated agent of AA copolymer demonstrated a permeability of 0.0018 μm2 with the strength of the samples for bending at the age of 2 days equal to 8.0 MPa.
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Self-healing cements – the key to maintaining the integrity of cement sheath. Part 2
Статья научная
To control water production, it is necessary to seal the channels of 20–25 mm thickness in the cement sheath at a depth of hundreds and thousands of meters. The most promising solution is the use of self-healing cements. The concept of self-healing materials has been known since the 1980s due to the studies of Donald Jud. The most fundamental works are by Sybrand van der Zwaag, Sheba D. Bergman and Fred Wudl, Richard P. Wool, D.Y Wu, N.R. Sottos, Erin B. Murphy, Henk Jonkers, who substantiated the concept, suggested technologies and additives to restore the integrity of polymer and cement materials. Despite active research in this area, Schlumberger is the only service company which elaborated and successfully applied the «self-healing» well cement called Futur. The authors of the article set the task of well cement modification that could enable autonomous «healing» of water-conducting channels through which formation water migrates. The following materials were used in the study: polyacrylamide (PAA), water-swellable polymer (VNP V-615), sodium polyacrylate (SP), cross-linked PAA copolymers, active waterproofing mineral additives and swelling elastomers. Most of the additives have a degree of swelling of more than 150%, they effectively reduce a permeability of the cement stone, however multi-layer coating is required to control the speed of their swelling. A significant drawback of the analyzed materials was the complexity of the coating. A cross-linked AA copolymer based on anionic polycrylamide was the most effective reagent that was easily covered with a water-soluble shell. The cement stone with integrated agent of AA copolymer demonstrated a permeability of 0.0018 μm2 with the strength of the samples for bending at the age of 2 days equal to 8.0 MPa.
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