Search Results (16)

Rigid polyurethane foams (RPUFs) are widely used as lightweight thermal insulation materials. Their properties can be improved by incorporating inorganic fillers. However, the effect of filler particle size has not been sufficiently investigated. This study examines the influence of aluminosilicate microsphere diameter (80, 150, 300, and 500 μm) on the properties of RPUFs. Foams containing 10 wt.% microspheres (M) were prepared by the free-rise method. Their cellular structure, apparent density, mechanical, acoustic, thermal, and thermomechanical properties were evaluated. The addition of microspheres reduced the average cell diameter from 184 ± 29 μm for PU_0 to 147–174 μm, depending on microsphere size, and increased the apparent density from 31.3 to approximately 37 kg·m⁻³. The compressive strength decreased from 186 ± 6 kPa for PU_0 to 159 ± 2 kPa for PU_500M, whereas the tensile strength increased from 257 ± 14 kPa for PU_0 to 323 ± 14 kPa for PU_500M. The highest average sound absorption coefficient (0.14) was obtained for PU_300M, representing a 75% improvement over PU_0 (0.08). The composites also showed improved thermal stability and storage modulus. Among the investigated composites, PU_300M exhibited the most balanced combination of mechanical and acoustic properties. Full article

Dispersed ferrospheres (FSs) are a valuable component of coal fly ash, whose application potential is determined by their microspherical design, fine particle size, and high concentration of magnetic iron compounds. This study proposes an efficient technological scheme for extracting dispersed FSs from high-calcium fly ash, comprising (i) aerodynamic classification and (ii) dry magnetic separation. The isolated fractions were characterized, including determination of the particle-size distribution, morphology, chemical and phase composition, Mössbauer parameters, magnetic properties, and surface distribution of magnetic phases. It was shown that the average particle diameters of the FS narrow fractions are 3 and 8 µm. The major chemical components are FeO, CaO, and SiO₂, whose total content amounts to 81–83 wt %. Regarding the phase composition, Fe-spinel and calcium ferrites are predominant, accounting for 38–46 and 13–16 wt %, respectively. The efficiency of the proposed process for extracting FSs reaches the level achieved by conventional wet magnetic separation. The saturation magnetization of the dispersed FS samples increases by more than an order of magnitude (up to 23–28 emu/g) compared to the initial fly-ash fractions (1.7–1.8 emu/g). For the first time, magnetic topography investigation of single microspheres directly demonstrates that the surface of the aluminosilicate matrix is enriched with magnetic microcrystals formed during coal combustion. The obtained results may prove useful in the design of functional materials with magnetically active surfaces for advanced applications. Full article

Microspheres recovered from energy sector processes, primarily as by-products of large-scale power generation, represent a valuable aluminosilicate resource with significant application potential. Their effective upgrading is essential to maximize material recovery and support circular economy strategies aimed at reintegrating industrial by-products into high-value applications. However, the heterogeneity of microspheres in terms of grain size distribution, density, and mechanical strength poses a challenge for their efficient processing and standardization. This study presents a refinement method and process line for upgrading microspheres obtained from the energy sector into high-mechanical-strength products. The proposed approach is based on the systematic fractionation of raw material, supported by the detailed characterization of feedstock from different sources and continuous control of key technological parameters. Particular emphasis is placed on optimizing separation processes and final blending strategies to ensure consistent product quality. The developed technology enables the production of microspheres meeting stringent requirements, thereby expanding their applicability in demanding industrial sectors such as drilling engineering. At the same time, the approach contributes to increased resource efficiency by redirecting a significant portion of energy sector by-products back into the economic cycle, in line with circular economy principles. Full article

In this paper, the effect of aluminosilicate microspheres (ASMs) from thermal power plant (TPP) ash on the properties of epoxy composites was studied. A method for modifying the ASMs’ surface using aminoacetic acid was developed to improve the adhesion at the polymer–filler interface. Complex analysis methods, including scanning electron microscopy, infrared spectroscopy, a thermogravimetric analysis, DSC, and DMA, showed that adding the optimal amount of ASMs significantly improved the physical and mechanical properties of the composites: the flexural strength increased by 112%, the elastic modulus by 198%, and the impact strength by 50%. Functionalization of the ASMs enhances their interaction with the matrix, providing the composites with the best strength and thermal stability indicators among the studied materials. The study of the curing kinetics showed the initiating effect of functionalized ASMs on the curing process of epoxy compositions, associated with the presence of active amino groups on the surface of the particles. The resulting composites demonstrate potential for application in structural and fire-resistant materials; have high-deformation and -strength characteristics; and facilitate the disposal of industrial waste. Full article

Ferrospheres (FSs) are a microspherical component of fly ash from pulverized coal combustion. The wide variations in chemical and phase composition, morphology, and the spherical design of FSs suggest their use as functional materials capable of replacing expensive synthesized materials. A general understanding of the formation of FSs from thermochemical transformations of the mineral components of the original coal is important for identifying the most promising sources of FSs with a high content of a certain morphological type active in a specific process. A systematic SEM-EDS study of the composition–structure relationship of the skeletal-dendritic FSs isolated from fly ash has revealed common routes of their formation. These FSs are formed as a result of thermochemical transformations of iron-containing minerals with the participation of aluminosilicates of the original coals. The aluminosilicate precursor that determines the skeletal-dendritic structure is illite. The crystallization of skeletal-dendritic globules occurs due to the “seed” of Al, Mg-ferrospinel formed from the thermochemical transformation of illite. The general trend of change in the structure of globules from a coarse skeletal to a fine dendritic structure is associated with a decrease in the main spinel-forming oxides content and an increase in the silicate melt viscosity. Full article

This research aims to explore how functionally active structures affect the physical, mechanical, thermal, and fire-resistant properties of elastomeric compositions using ethylene–propylene–diene rubber as a base. The inclusion of aluminosilicate microspheres, microfibers, and a phosphorus–boron–nitrogen–organic modifier in these structures creates a synergistic effect, enhancing the material’s heat-insulating properties by strengthening coke and carbonization processes. This results in a 12–19% increase in heating time for unheated sample surfaces and a 6–17% increase in residual coke compared to existing analogs. Microspheres help counteract the negative impact of microfibers on composition density and thermal conductivity, while the phosphorus–boron–containing modifier allows for controlling the formation of the coke layer. Full article

This article presents the results of research aimed at optimizing the process of recovery of valuable components from ash and slag waste from thermal power plants. In this work, both experimental and theoretical studies were carried out to substantiate the use of magnetic separation methods for ash and slag waste processing. Ash and slag wastes were chosen as an object of research due to the presence of valuable components such as iron, aluminum, etc., in them. The research results showed that the method of magnetic separation, including high-gradient magnetic separation, can be effectively used in ash and slag waste processing. As a result, the topology of a magnetic beneficiation technological scheme has been proposed to obtain high-value-added products such as high-magnetic iron minerals, low-magnetic iron minerals, and aluminosilicate microspheres. By using magnetic separation in a weak magnetic field, magnetic microspheres containing high-magnetic iron minerals associated with intermetallics, ranging in size from 20 to 80 µm, were recovered. In the second stage of magnetic separation (high-gradient magnetic separation), an iron ore product with an iron content of 50% with a recovery of 92.07% could be obtained. By using scanning electron microscopy, it was found that the main part of microspheres, which contain low-magnetic iron minerals and aluminosilicates, with sizes from 2 to 15 microns, was recovered in the magnetic fraction. This paper proposes a new approach to the enrichment of ash and slag materials using magnetic separation, which will increase the efficiency of their processing and make the process environmentally sustainable. Full article

Elastomeric materials are utilized for the short-term protection of products and structures operating under extreme conditions in the aerospace, marine, and oil and gas industries. This research aims to study the influence of functionally active structures on the physical, mechanical, thermophysical, and fire- and heat-protective characteristics of elastomer compositions. The physical and mechanical properties of elastomer samples were determined using Shimazu AG-Xplus, while morphological research into microheterogeneous systems and coke structures was carried out on a scanning electronic microscope, Versa 3D. Differential thermal and thermogravimetric analyses of the samples were conducted on derivatograph Q-1500D. The presence of aluminosilicate microspheres, carbon microfibers, and a phosphor–nitrogen–organic modifier as part of the aforementioned structures contributes to the appearance of a synergetic effect, which results in an increase in the heat-protective properties of a material due to the enhancement in coke strength and intensification of material carbonization processes. The results indicate an 8–17% increase in the heating time of the unheated surface of a sample and a decrease in its linear burning speed by 6–17% compared to known analogues. In conclusion, microspheres compensate for the negative impact of microfibers on the density and thermal conductivity of a composition. Full article

The article considered the issues of the modification of gypsum stone to improve its performance properties. The influence of mineral additives on the physical and mechanical characteristics of the modified gypsum composition is described. The composition of the gypsum mixture included slaked lime and an aluminosilicate additive in the form of ash microspheres. It was isolated from ash and slag waste from fuel power plants as a result of their enrichment. This made it possible to reduce the carbon content in the additive to 3%. Modified compositions of the gypsum composition are proposed. The binder was replaced with an aluminosilicate microsphere. Hydrated lime was used to activate it. Its content varied: 0, 2, 4, 6, 8 and 10% of the weight of the gypsum binder. Replacing the binder with an aluminosilicate product for the enrichment of ash and slag mixtures made it possible to improve the structure of the stone and increase its operational properties. The compressive strength of the gypsum stone was 9 MPa. This is more than 100% higher than the strength of the control composition of gypsum stone. Studies have confirmed the effectiveness of using an aluminosilicate additive—a product of enrichment of ash and slag mixtures. The use of an aluminosilicate component for the production of modified gypsum mixtures allows the saving of gypsum resources. Developed formulations of gypsum compositions using aluminosilicate microspheres and chemical additives provide the specified performance properties. This makes it possible to use them in the production of self-leveling floors, plastering and puttying works. Replacing traditional compositions with a new composition based on waste has a positive effect on the preservation of the natural environment and contributes to the formation of comfortable conditions for human habitation. Full article

The regularities of obtaining foamed alkali-activated geopolymer materials based on different wastes of coal power engineering (fly ash, fuel (boiler) slag, ash, and slag mixture) were considered. The phase composition of the studied waste showed the presence of a significant amount of the amorphous phase, as well as a crystalline phase. mostly in the form of high quartz. The microstructure of studied the waste showed that the fly ash consisted of monodisperse hollow aluminosilicate microspheres, the fuel slag was represented by polydisperse irregular particles, and the ash and slag mixture included both of these materials in different ratios. Blowing agents such as aluminum powder, hydrogen peroxide, and sodium hypochlorite were chosen to achieve the porous structure of the geopolymer materials. The calculations of the geopolymer precursor compositions were carried out. Samples were synthesized, and their physical and mechanical properties, such as density, strength, porosity, and thermal conductivity, were analyzed. The micro- and macrostructure of the samples, as well as the pore distribution of the obtained geopolymers were studied. Conclusions were made on the choice of the most-optimal foaming agent and the optimal coal combustion waste suitable for the synthesis of the geopolymer materials. Full article

Coal fly ash hollow aluminosilicate microspheres (cenospheres) of stabilized composition (glass phase—95.4; (SiO₂/Al₂O₃)_glass—3.1; (Si/Al)_at. = 2.6) were used to fabricate lutetium-176 encapsulated aluminosilicate microspheres as precursors of radiolabeled microspheres applied for selective irradiation of tumors. To incorporate Lu³⁺ ions into cenosphere’s aluminosilicate material, the following strategy was realized: (i) chemical modification of cenosphere globules by conversion of aluminosilicate glass into zeolites preserving a spherical form of cenospheres; (ii) loading of zeolitized microspheres with Lu³⁺ by means of ion exchange 3Na⁺ ↔ Lu³⁺; (iii) Lu³⁺ encapsulation in an aluminosilicate matrix by solid-phase transformation of the Lu³⁺ loaded microspheres under thermal treatment at 1273–1473 K. Two types of zeolitized products, such as NaX (FAU) and NaP1 (GIS) bearing microspheres having the specific surface area of 204 and 33 m²/g, accordingly, were prepared and their Lu³⁺ sorption abilities were studied. As revealed, the Lu³⁺ sorption capacities of the zeolitized products are about 130 and 70 mg/g Lu³⁺ for NaX and NaP1 microspheres, respectively. It was found that the long-time heating of the Lu³⁺-loaded zeolite precursors at 1273 K in a fixed bed resulted in the crystallization of monoclinic Lu₂Si₂O₇ in both zeolite systems, which is a major component of crystalline constituents of the calcined microspheres. The fast heating–cooling cycle at 1473 K in a moving bed resulted in the amorphization of zeolite components in both precursors and softening glass crystalline matter of the NaX-bearing precursor with preserving its spherical form and partial elimination of surface open pores. The NaX-bearing microspheres, compared to NaP1-based precursor, are characterized by uneven Lu distribution over the zeolite-derived layer. The precursor based on gismondin-type zeolite provides a near-uniform Lu distribution and acceptable Lu content (up to 15 mol.% Lu₂O₃) in the solid phase. Full article

The modern energy-saving vector of development in building materials science is being implemented in a complex way through the development of new heat-insulating materials with the simultaneous exclusion of low-ecological cement from them. This article presents the results of the development of resource-saving technology for a heat-insulating composite material. The research is devoted to the development of scientific ideas about the technology and properties of effective cementless lightweight concretes. The aim of the work is to create a heat-insulating composite material based on porous granules and a matrix from mixtures of liquid glass and thermal energy waste. The novelty of the work lies in establishing the patterns of formation of a stable structure of a porous material during thermal curing of liquid glass with technogenic fillers. Studies of liquid glass mixtures with different contents of fly ash and aluminosilicate microspheres revealed the possibility of controlling the properties of molding masses in a wide range. To obtain a granular material, liquid glass mixtures of plastic consistency with a predominance of aluminosilicate microspheres are proposed. The matrix of composite materials is formed by a mobile mixture of liquid glass and a combined filler, in which fly ash predominates. The parameters of heat treatment of granular and composite materials are established to ensure the formation of a strong porous waterproof structure. The possibility of regulating the structure of composite materials due to different degrees of filling the liquid glass matrix with porous granules is shown. A heat-insulating concrete based on porous aggregate has been developed, characterized by the genetic commonality of the matrix and the granular component, density of 380–650 kg/m³, thermal conductivity of 0.095–0.100 W/(m °C) and strength of 3.5–9.0 MPa, resistance under conditions of variable values of humidity and temperature. A basic technological scheme for the joint production of granular and composite materials from liquid glass mixtures is proposed. Full article

Co-processing of radioactive effluents with coal fly ash-derived materials is recognized as a resource-saving approach for efficient stabilization/solidification of radioactive components of wastewater. In this context, the paper is focused on the hydrothermal synthesis of Sr²⁺-bearing aluminosilicate/silicate phases as analogs of a mineral-like ⁹⁰Sr waste form using hollow glass-crystalline aluminosilicate microspheres from coal fly ash (cenospheres) as a glassy source of Si and Al (SiO₂-Al₂O₃)_glass) and Sr(NO₃)₂ solutions as ⁹⁰Sr simulant wastewater. The direct conversion of cenosphere glass in the Sr(NO₃)₂-NaOH-H₂O-(SiO₂-Al₂O₃)_glass system as well as Sr²⁺ sorption on cenosphere-derived analcime (ANA) in the Sr(NO₃)₂-H₂O-ANA system were studied at 150–200 °C and autogenous pressure. The solid and liquid reaction products were characterized by SEM-EDS, PXRD, AAS and STA. In the Sr(NO₃)₂-NaOH-H₂O-(SiO₂-Al₂O₃)_glass system, the hydrothermal processing at 150–200 °C removes 99.99% of the added Sr²⁺ from the solution by forming Sr-tobermorite and Sr-plagioclase phases. In the Sr(NO₃)₂-H₂O-ANA system, Sr²⁺ sorption on analcime results in the formation of solid solutions (Na_1−nSr_n/2)AlSi₂O₆·H₂O of the Na-analcime–Sr-wairakite series. The results can be considered as a basis for the development of environmentally sustainable technology for ⁹⁰Sr removal from wastewater and immobilization in a mineral-like form by co-processing waste from coal-fired and nuclear power plants. Full article

Aluminosilicate microspheres are a valuable fraction of coal fly ash with diverse applications due to their low density. Currently, there is no efficient and ecologically rational method of cenosphere recovery from fly ash. A combination of dry methods for the recovery of both fine ash particles and aluminosilicate microspheres from coal fly ash is presented. It is comprised of fluidised bed separation followed by screening and pneumatic separation in a free-fall air chamber. Fluidised bed separation was assisted by a mechanical activator to prevent agglomeration. This step reduced the portion of material that required further treatment by 52–55 wt.%, with the recovery of microspheres exceeding 97%. Then, the concentrates were individually subjected to pneumatic separation. The final separation product for the fly ash containing 0.64 wt.% cenospheres was a cenosphere concentrate that constituted about 17 wt.% of the initial fly ash. The recovery of cenospheres was around 81%. Usage of a combination of dry methods allowed for maintaining almost 83 wt.% of the raw material in its dry form. Furthermore, the produced fly ash grain fractions could be used for different industrial purposes. Full article

The article presents the recipe for ultra-lightweight cement slurry for wellbore sealing. In ordinary lightweight cement slurries, the addition of microspheres and a large amount of water are used to maintain rheological parameters. This is a problem because the light particles of microspheres segregate. The cement sheath from such a cement slurry has an anisotropic microstructure and does not stabilize the casing column. In the new ultra-light cement slurry, 60% aluminosilicate microspheres and a large amount of water were used. The ultra-light weight slurry has a density below 1.2 g/cm³. This cement slurry does not segregates and in the sedimentation stability test has the same density at all measuring points. The cement slurry, despite the larger amount of water, has the same filtration as the control sample. The technological parameters of the slurry are adapted to the borehole conditions. Cement slurry is a ready-made application to seal a borehole with poor wellbore stability under conditions of 40 °C and 10 MPa pressure. The cement sheath structure in the wellbore after binding is homogeneous. The use of such slurry allows to reduce the risk of wall damage in wellbores of poor stability. Full article