Search

In materials science, composites (nanocomposites) are materials consisting of a combination of two or more micro (nano-) and / or macrocomponents, which are different in shape, chemical composition and do not have significant mutual solubility. A distinctive feature of composites that determine their importance is that two or more noticeably different components when combined form a system that has significantly improved properties compared to the properties of its individual components. It is known that for most polycrystalline materials the hardness and elastic limit increase with decreasing average particle size (Hall-Petch law). Therefore, the possibility of the existence of such a system is determined by the interaction forces between the structural parts when they are brought closer to sufficiently small distances. For the emergence of a stable structure of a solid, it is necessary to provide conditions under which the forces of attraction (van der Waals forces) will prevent the removal of the components particles from each other. Any solid body is a system consisting of a huge number of microparticles. In such systems exhibit specific patterns. To describe the state of the formations, you can use the thermodynamic approach, which considers the macroscopic structure as a whole, and not its individual parts. In this case, the magnitude of the potential of attraction (van der Waals) determines the possibility of the appearance of structural bonds at the interface. The thermodynamic criterion for evaluating such component compatibility is the Hamaker constant (A), as a criterion for the energy of dispersion interaction of highly dispersed particles. This approach allows solving two fundamental problems of building materials science: optimize the composition when creating composites of various in nature substances and predict the phenomena associated with changes in the properties (composition) of the finished composite during its operation, caused by technogenic metasomatism. In previous studies, we have shown the possibility of experimentally determining the magnitude of the complex Hamaker constant (А), which characterizes the energy of dispersion interaction of a solid surface when it comes in contact with a water-ethanol (slightly polar) solution (А01). This value is functionally related to the properties of the solution (А00) and the solid phase itself (А11). In this paper, we present an algorithm and the results of calculating А11, as a constant of the dispersive interaction of the components that make up the solid phase. Due to the fact that one of the most common composites used in the construction industry are concrete and wood (a natural composite consisting of cellulose fibers bound by a polymer matrix, which is mainly lignin), these materials were used as pilot objects for research. [ABSTRACT FROM AUTHOR]

This work is devoted to obtaining and characterization of wood-mineral composites based on wood debarking waste and basalt screenings, which have improved ecological, strength, sound and heat insulation properties. To achieve this goal, the following tasks were solved: the regularities of the process of spontaneous filling of the porous space of the wood matrix with mineral fine particles due to the capillary forces of plant raw materials were established; simulation models of the structure and functional properties of the wood-mineral composite on the basis of studying the regularities of the influence of the fractional composition and the quantitative ratio of wood filler to its physicomechanical and thermophysical properties were constructed; a method for obtaining a construction composite material based on a mixture of coarse wood aggregate and a fine dispersible cementless mineral binder, as well as methods for imparting a specified set of strength and performance properties to a construction composite, including for use in extreme North conditions, was developed; technological foundations for the production of wood-mineral composite in the form of heat and sound insulation blocks and plates were developed. The methodological basis of the study is the main provisions of the polystructural theory of composite materials, the thermodynamics of surface phenomena and methods of mathematical statistics. To solve the set tasks, the concept of the system approach is applied, in which the composition, properties and structure of the composites are presented in the form of an interconnected system. Microscopic analysis, X-ray phase analysis, infrared spectroscopy, and photon correlation spectroscopy were used to study the structural features of raw materials and synthesized materials, to evaluate their phase composition, and also to identify the samples. Methods of mechanical dispersion were used to produce nano- and fine-dispersed materials. The realization of the method for obtaining wood-mineral composite material is based on the spontaneous wooden bark reinforcement by nanodispersed basalt particles when it swells in an aqueous medium, taking into account the surface properties of the bark and basalt (electrokinetic potential, porous space, the presence of active centers, etc.); separation of the solid phase from the reaction slurry; Adding a binder based on a mixture of finely dispersed basalt and polysilicate systems synthesized by sol-gel technology from silica-containing raw material (polymineral sand), followed by molding the semi-finished product and drying it. [ABSTRACT FROM AUTHOR]

At the present time many building of Arkhangelsk are built based on standard project. In the main these project don't take into account the negative factor of northern conditions. For such territories of cities it is necessary to create specific conditions for the formation of human habitat, including special color solutions. The study analyzes the features of the formation of a harmonious color environment and the factors of color. Also the need of using the concept of forming an urban environment based on the consideration of various factors was identified. The introduction of unified color solutions was carried out on the example of a separate region on the territory of which active development is conducted. One of the methods for creating coatings for various facade materials based on the use of environmentally friendly materials is presented. The introduction of dispersed material into the coating composition can lead to improved decorative and performance properties of the coatings. The proposed options of forming and correcting the color image of the city and the method of creating color coatings for various building materials on the basis of common natural raw materials contribute to the most qualitative management of the city's coloring. This, in turn, has a positive effect on the psycho-emotional state of a local citizen. [ABSTRACT FROM AUTHOR]

Implementation of the development program for the Northern and Arctic territories is not possible without the use of modern materials and technologies in the construction industry. One of the most common and popular building materials is the fine grained concrete, for the production of which, use chemical additives, mainly imported, improving the performance characteristics of the composite. Therefore, the actual problem is the replacement of imported components with Russian-made additives. As such an additive, technogenic raw materials can be used in the form of saponitecontaining waste from the diamond mining industry. For the production of fine-grained concrete, river sand of medium size of the “Kenitsy" deposit was used, as cementing agent - Portland cement of company “Mordovcement". The saponite-containing material extracted from the recycled water of the enrichment process of kimberlite ores was mechanically activated beforehand. Control samples of concrete and experimental (with the highly disperse additive) were prepared by standard methods. After aging for 28 days, the performance characteristics of the obtained samples (compressive strength, frost resistance and water impermeability) were determined. A highly dispersed saponite-containing material with an average particle size of 445 ± 40 nm and a specific surface of 50670 ± 10 m2 / kg was used as an additive to the concrete mixture. Determination of strength and frost-resistant characteristics showed a significant increase in these parameters in the prototypes. In addition, the introduction of a mineral supplement increases the brand's water resistance. Analysis of the microstructure of the concrete samples by scanning electron microscopy showed that (in contrast to control samples), hydrosilicates of the tobermorite group play the role of an additional binder. [ABSTRACT FROM AUTHOR]

The study solves actual modern problem for obtaining polysilicate solution (as a mineral component of clinkerless binder) based on low-quality siliceous raw materials. A mechanochemical synthesis method of sustainable colloidal silica sol (with a particle size of 5-25 nm) is proposed, as well as a grounded choice of grinding parameters is made. Influence of protolytic properties of liquid phase on dispersion speed, aggregate and sedimentation stability of the silica sol are studied. The obtained dependence of the zeta-potential of particles from the pH of diluent has shown that in acidic region have equivalence point and a low zeta-potential area in which the colloidal particles become unstable (which may lead to gelification in the system). The results of experimental determination of the presence of soluble silicate in dispersion (by the spectral method) showed that during heating (up to 90 °C) in a weakly alkaline medium there is a sharp increase in its output product. It is found that the sodium polysilicate produced in this method is highly reactive and during dehydration can form water-resistant and fireresistant film on the surface of various materials. A number of recommendations on the application of polysilicate as a component of mineral clinkerless binder are given. [ABSTRACT FROM AUTHOR]

The results of experimental research of hydration process of highly dispersed systems based on saponit-containing waste, extracted as the solid phase of the recycled water suspension kimberlite ore enrichment process of the diamond industry. Saponitcontaining sludge was dehydrated and subjected to mechanical activation on the planetary ball mill. Mechanical activation of raw material more than 60 minutes does not increase the specific surface area of samples was found. Specific surface area is achieves the maximum value of 50600 m2/kg. If we increasing the time of mechanical dispergation up to 120 minutes this parameter will be decrease due to agglomeration of particles. At the same time, average particle size of saponit-containing material will be in ranges from 445 to 517 nm. The x-ray analysis of the samples showed that the mechanical activation will help to increase the content of the active surface amorphous phase up to 40%. Adding of highly dispersed additive based on mechanic activated saponit-containing material to the composition of Portland cement after the interaction of this composition mixtures with water leads to the formation of submicrocrystals of the hydrosilicates from group of tobermorite. This fact was found by scanning electron microscopy methods. Record of absorption spectra in the infrared range of the samples was revealed of the fluctuations in the hydrosilicate groups, resulting in the following wave numbers 1440-1660 cm-1 and a broad band at 3300-3500 cm-1. This fact in agreement with the microstructural research. Thus, it is shown that the mechanoactivated saponite-containing material will be able to form the hydrosilicates of additional generation. The main conclusion of our work, based on our obtained results, allow us to use the saponite-containing waste as a potentially active mineral component in the binders compositions of hydration curing type. [ABSTRACT FROM AUTHOR]

Previous researches have shown the possibility of using organic-mineral additive based on glyoxal for injection strengthening of soils in roadbases and engineering communications. Saponite containing material was used as mineral component in the composition. Saponite containing material is a solid phase, extracted from the circulating water suspension of the kimberlite ore dressing. Modification of the sandy soil by the tailored organic-mineral additive content increases its specific cohesion up to 50 times. It was established that this effect is achieved by polymerization reaction of the organic component of the additive, while the mineral component possesses the sorption properties regulating the structure formation in the system by formatting the optimum degree of the reaction mixture saturation by a liquid phase. The aim of this research presented in this paper was to study microstructural features of clay (aluminum silicate) soils stabilized by the organic additive. As the model of aluminum silicate soil saponite containing material was used. The study of the test samples composition by X-ray diffractometry method allowed to establish the presence of the following minerals: saponite 63 %, quartz 10 % and dolomite 10 %. The content of other minerals (chlorite, hematite, calcite, apatite, etc.) is 17 %. Microstructural features of samples were investigated by scanning electron microscopy method. The obtained electronic photographs of the analyzed compositions showed the formation of a homogeneous periodic colloidal structure (PCS). It should be noted that when the organic additive is used for strengthening clay soils introduction of an additional sorbent isn't required. This is due to sorption properties of clays. In this case, the polymerization process proceeds at a constant rate uniformly throughout the volume of the analyzed soil sample. The formation of the PCS is connected with increasing dispersion interaction between the particles of the soil by synthesis of a sealing layer from the organic polymer. [ABSTRACT FROM AUTHOR]

The study solves actual modern problem for the integrated use of waste from wood processing and mining industries, in particular, waste of wood debarking and basalt dropout. An optimal method for obtaining a new nanocomposite based on these materials is proposed, as well as a grounded choice of binder composition is made. Strength, thermophysical and fire properties of structural heat insulation on the basis of waste of wood debarking and basalt dropout are studied. The obtained dependence of the composite strength increase from the elapsed time has shown that the material gains the project strength in 7 day (at least 2.5 MPa). The results of experimental determination of the thermal conductivity coefficient showed that insulating properties of the composite (λ = 0.075 W/mK) are comparable to common insulating materials, such as glass wool. The experiments to determine the fire-technical characteristics showed that in comparison with the materials from wood, such basic fire-technical features as: combustibility group, flammability group, toxicity and smoke-forming ability group are significantly improved. [ABSTRACT FROM AUTHOR]

The article describes the evaluation of the binding ability of the finely-dispersed environmentally friendly saponite-containing waste (SCW), which is obtained as a result of the enrichment of diamond industry kimberlite ores (diamond deposit named after M.V. Lomonosov, Arkhangelsk region, Russia), as a binder for mineral wool insulating materials. For this purpose an express method for determining the activity of binder (A) using functional dependence of binder activity on the value of the thermal effect of the hydration reaction (δH) is provided. The obtained straight-line functional correlation of the type A = f(δH) has a high coefficient of approximation reliability (R² = 0.96), indicating the relationship of these values and the practical applicability of the obtained dependence to assess the quality of binders. The research results of the binding ability of the finely-dispersed SCW samples, previously obtained by grinding on the planetary ball mill, showed that the maximum activity value is achieved when the specific surface area of SCW is at least 800 m²/kg. [ABSTRACT FROM AUTHOR]

A method for controlling the water-cement ratio of concrete in the process of hardening by introducing highly dispersed mineral additives based on saponite-containing material (SCM), extracted from kimberlitic ore waste of the Arkhangelsk region diamond mining industry (Lomonosov deposit), is suggested. The resulting relation of the material particle size and the value of its specific surface (Ssp) showed that the addition with Ssp = 50.670 m²/kg is the most efficient. The mechanism of mineral additive sorption has shown that the process of self-saturation of solids saponite-containing material with water vapor has a continuous nature (12 days). Desorption process has a different character if compared to the adsorption isotherm, i.e., there is an adsorption-desorption hysteresis. The study of SCM samples after desorption of moisture by infrared spectroscopy showed that the chemical compounds, which are present in the material, can form calcium hydrosilicates while saturated. This fact, along with the ability of modifying additive to regulate the water-cement ratio in the process of concrete hardening, contributes to a significant improvement in the physical and mechanical characteristics (strength, frost resistance) of the concrete composite. [ABSTRACT FROM AUTHOR]