The research results will be of interest to specialists in the construction industry since the proposed recipes for eco-friendly, alkali-activated materials are an alternative to expensive and energy-intensive Portland cement, and they provide for the creation of strong and durable concrete and reinforced concrete composites.The cement industry is recognized as an environmental nuisance, and so there is a need to not only minimizes the consumption of cement, but also to completely recycle the waste of the cement industry. This paper’s originality lies in the fact that, for the first time, a comprehensive study of the structure formation of alkali-activated materials (AAM) based on aspiration dust and clinker dust has been carried out. The tasks for achieving this goal were to characterize cement production waste as a new binder and comprehensively research the microstructure, fresh, physical, and mechanical properties of alkali-activated material based on a cement-free binder. Grains of cement production waste are represented by coarse volumetric particles with pronounced cleavage, and a clear presence of minerals is observed. The mineral composition of cement production waste is characterized by calcium silicates, which guarantee good binding properties. The results of the X-ray diffraction analysis of the samples  confirmed the presence of calcite, quartz, feldspar close to albite, micas, and zeolites. The obtained products of the chemical interaction of the binder components confirm the effectiveness of the newly developed AAM. As a result of comparing several binders, it was found that the binder based on aspiration dust with Na Portland cement production at the world level in 2021 reached 4.1 billion tons, and it is growing rapidly from year to year due to developing countries . In addi2CO3 type and the calcium oxide of granular slag, resulting in the formation of calcium carbonate, sodium hydroxide, and potassium solutions.There is a need to search for cementless building materials, the first place among which is occupied by alkali-activated materials (AAM) . It was The traditional materials for creating alkali-activated materials include fly ash and blast-furnace granulated slag ,14. TherBernal and Provis  argued t3 of exhaust gases, with a dust content of up to 70 g/m3 [3 [Rotary clinker kilns are the main sources of dust emissions , and this is due to the fact that the clinker firing process occurs according to the counterflow principle where exhaust flue gases entrain fine particles of the fired raw mixture into their flow . In the  70 g/m3 . Thus, i 70 g/m3 . An elec g/m3 [3 .In the process of burning Portland cement clinker in electrostatic precipitators and rotary kilns, a large amount of dust accumulates—both clinker and aspiration. The rational use of these products, which contain a certain proportion of a full-fledged raw material resources, is an urgent task for the cement industry . It shouThis paper presents the results of an examination of cement industry waste since their volumes are substantial enough to provide for the rational use of a dust from electrostatic precipitators as a relevant solution to many problems comprising both economical and eco-technical issues. The aim of this work is a to complete comprehensive study of the structure formation of alkaline activated materials based on clinker dust and aspiration dust. The tasks to achieve this aim were the characterization of the cement production waste as a new binder and a comprehensive study of the microstructure, fresh, physical, and mechanical properties of alkali-activated material based on the binder.Aspiration and clinker dust from the electrostatic precipitators of rotary clinker kilns  were used as a precursor of AAM. 2SiO3 was used as the binder modifier (silicate modulus of 2.8 and density of 1.42 g/cm3). Sodium hydroxide NaOH was used as an alkali. To accelerate the hardening process of the AAM, sodium fluorosilicon Na2SiF6 was used in a dosage of 6% of the Na2SiO3 mass.Liquid glass such sodium metasilicate NaThe quartz sand obtained by fractionation of fine (1.5 mm) and coarse (2.5 mm) grains in a ratio of 22: 78% was used as a fine aggregate. 2SiO3 and K2 with water to prove the effectiveness of the precursor). The other three mixes used aspiration dust . Five different concrete mixes were developed; common to all was the use of cement industry waste . Two mixThe prepared samples hardened on the first day under normal conditions at a temperature of 20 ± 2 °C, but on the second day, the samples were placed periodically, for 28 days, in an oven at a temperature of 50 °C for two hours. Samples prepared in this way, even at a high standard consistency, will effectively structure without cracking.The granulometry of the raw material particles was carried out using the laser analyzer Analysette 22 . The specific surfaces of the bulk raw materials were studied using a PSH-12 device .The structure formation processes of the AAM were studied using the scanning electron microscope (SEM) Vega II LMU  with an energy dispersive microanalysis system )) manufactured by the company Oxford Instruments Analytical . The system provided the ability to carry out elemental analyses in the range from Na to U . The studies were carried out at an accelerating voltage of 20 kV.X-ray diffraction (XRD) analysis was performed for reflection according to Bragg–Brentano by an ARLX’TRA  diffractometer using the Θ–Θ kinematic scheme with a horizontal arrangement of a flat sample. The characteristic radiation of a copper anode was used (wavelengths CuKα1 1.5406 Å and CuKα2 1.5444 Å). The energy window of the semiconductor detector tuned to register this range also partially captured the close wavelengths of CuKβ1 1.3922 Å and WLα1 1.4763 Å.Studies of the fresh and hardened properties of the AAM were carried out in accordance with Russian standard 30744-2001. Compressive strength was determined on 70 × 70 × 70 mm samples, but for flexural strength, the tests used sample beams with a size of 40 × 40 × 160 mm (three samples of each composition) . 2O in the aspiration dust sample was 6.43%, while in the clinker dust was 1.57%. The explanation for this is that the clinker dust was formed in the hot zone of solid-phase synthesis in a rotary kiln at temperatures of 1300 °C and above, which is where the burnout and decomposition of alkali metal oxides occur.Energy-dispersive microanalysis of the studied electrostatic precipitator dust powders  showed tThe SEM images in The SEM images of the aspiration dust denote a more loose, porous grain morphology with the observed initial stage of crystallization . AnalysiThe mix with aspiration dust is characterized by a bulk inhomogeneous structure . CavitieAccording to the results of the X-ray diffraction analysis of the AAM produced with the aspiration dust, calcite, quartz, larnite, feldspars with various compositions, and magnesium oxide were present, and weak X-ray peaks corresponding to muscovite (2 Θ ~ 8.8–8.9 degrees) and zeolites were detected . The higThe electron microscopy microanalysis denoted the prevailing content of calcium silicates and their hydrates within the main microcrystalline volume. The results of the analysis of the crystal aggregates of the calcium silicates are shown in The analysis of the results obtained in this study confirmed that alkali cement bricks produced with aspiration dust contained the following minerals: calcite, quartz, larnite, feldspars with various compositions, magnesium oxide, muscovite and zeolites, hydrosilicates, and calcium hydroaluminates and hydrosulfoaluminates. The analysis of the alkali-activated materials produced with the clinker dust shows that the samples were characterized by a bulk, relatively uniform structure  formed bAccording to the results of X-ray diffraction analysis of the AAMs produced with the clinker dust, calcite, quartz, phase related to larnite, and plagioclase related to albite were present. In addition, there was a wide peak in the region of 2 Θ ~ 8.8°–9.1°, which denoted the presence of mica with various structural parameters, and some peaks corresponded to zeolite related to garrronite . The micThe analysis of the oxide composition of the typical phases denoted that it could be attributed to the phase related to larnite and calcium silicates hydrates .The analysis of the results obtained in this study confirmed that alkali cement bricks produced with the clinker dust contained the following minerals: calcite, larnite, muscovite, zeolites, hydrosilicates, and calcium hydroaluminates and hydrosulfoaluminates.The standard consistency of the AAMs based on the aspiration dust was characterized by a fairly high demand for an alkaline solution of 72.5%, and the setting time was rather short, beginning at 16 and ending at 31 min. Even when mixing with water, both dusts (clinker and aspiration) exhibited binder properties, with setting occurring in 6–7 h and compressive strengths of 7.8–7.9 MPa . SP = 210 m2/kg). The high consumption of the mixing fluid was due to the dust from the electrostatic precipitators consisting of weakly burned clay minerals, not decomposed calcite, since the temperature at the waste collection point within the kiln was 170–320 °C.The composition of the aspiration dust from the electrostatic precipitators was similar to the prepared raw material mixture, though it contained up to 7% alkalis. To obtain a slurry with a normal density, 72.5% of the alkali solution was consumed, which is a relatively high value for its low specific surface area . It appeared that it was inactive in its natural form, and an alkali solution is desirable to activate this powder.When activated with an alkali solution, the aspiration dust demonstrated good reactivity, wherein the start of the setting process was observed within 16 min and ended at 31 min. The dust–alkali slurry was quite light and plastic, and easily treatable. In order to compare and reveal the optimum formulation based on the aspiration dust, it was mixed with different mixing fluids with the use of a curing accelerator, in one instance. At the same time, in the system “aspiration dust–NaThe clinker dust from the electrostatic precipitators manifested itself in quite a different way. When mixed with sodium silicate solutes, 50% of the alkali solution was required to obtain a slurry with a standard consistency, though when mixed with water, it demonstrated a hydrophobic effect, and 30% of the water was required to obtain a slurry with a normal density. At the same time, placing the mixture in the ring caused intensive water loss, while the start of setting began at 54 min and the end was attained after 2 h and 3 min. This behavior of the clinker dust from the electrostatic precipitators was caused by over-burning, as before testing, the weighted specimen doze was sieved through a No. 09 sieve and the residual was 5% of the glassy grains. Based on the specimen’s weight, this was the reason for the observed reduction of solubility of the studied powder. It should also be noted that mixing with water led to an intense efflorescence as a result of the hydration of the alkali oxides in the clinker dust.Thus, the binder based on the aspiration dust was the most effective as it obtained the maximum compressive strength of 50.7 MPa. Its low level of water absorption (11–12 wt. %) will make it possible to predict the high durability of structures built from this material .2SiO3”. In all of the examined systems, the highest reactivity was demonstrated by the alkali mixing fluid, which is responsible for curing cementitious binder due to its contact with anhydrous carbonic acid, in accordance with Equation (1):The obtained test results provide an understanding of the complexity of the setting process in the binding system “mineral powder-alkali solution NaAt the same time, in the prepared systems with the mixed alkali, the addition of mineral powders contributes to the processes of structural formation, which has been confirmed by studies using scanning electron microscopy and X-ray diffraction analysis.Compared with traditional concrete on cement CEM I 42.5 N, it was noted that, with nearly equivalent strength properties achieved, the standard consistency is 2–3 times higher, which is not a negative factor due to the absence of water, and hence, cracks. Reducing the density by 30% allows for the use of alkali-activated materials for lightweight and high-strength structures. The several-times-faster start and end of the setting time indicates an acceleration of construction production in the case of the use of AAMs. The water absorption by weight of the developed materials and of traditional concretes is nearly the same.The importance of this study lies in the creation of new building materials with unique characteristics and the simultaneous disposal of cement production waste. This contributes to cost reductions and aims at environmental care. The areas of application of the materials follows from the characteristics obtained, and, in particular, their low density and high strength make it possible to build tall and durable buildings and structures.Further development of the research topic may be associated with the development of new constructive technological solutions for the repair and restoration of buildings and structures. This will make it possible to reduce the cost of concrete repair work and reinforced concrete elements, as well as to expand and improve the formulations and technologies used for obtaining clinker-free binders in substandard and technogenic raw materials.Grains of cement production waste are represented by coarse volumetric particles with pronounced cleavage, small leaves, and the clear presence of minerals. The mineral composition of cement production waste is characterized by calcium silicates, which guarantee good binding properties.The results of the X-ray diffraction analysis of the samples based on the cement-free binder of alkaline activation using clinker dust and aspiration dust confirmed the presence of calcite, quartz, feldspar close to albite, micas, and zeolites. The obtained products of the chemical interaction of the components of the binder confirm the effectiveness of the newly developed AAM.2SiO3 and Na2SiF6 is the most effective since its specimens achieved a density of 1.8 g/cm3, maximum compressive strength of 50.7 MPa, flexural strength of 5.6 MPa, and minimum setting time (starting at 24 min and ending at 36 min), with a water absorption of 12.8 wt. %.As a result of comparing several binders, it was found that the binder based on aspiration dust with NaCompared with traditional concrete on cement CEM I 42.5 N, it was noted that with nearly equivalent strength properties achieved, the standard consistency is 2–3 times higher, which is not a negative factor due to the absence of water, and, hence, cracks. Reducing the density by 30% allows for the use of alkali-activated materials for lightweight and high-strength structures. Its several-times-faster setting start and end times indicate a potential acceleration of construction production. The water absorption by weight of the developed materials and traditional concretes is nearly the same.The research results will be of interest to specialists in the construction industry since the proposed recipes for eco-friendly alkali-activated materials are an alternative to expensive and energy-intensive Portland cement, and they enable the creation of strong and durable concrete and reinforced concrete composites.A comprehensive study of the recycling of cement industry waste for alkali-activated materials production was carried out. The tasks for achieving this goal were to characterize the cement production waste as a new binder and to comprehensively research the microstructure, fresh, physical, and mechanical properties of the alkali-activated material based on the binder. The following main conclusions were drawn, emphasizing the scientific novelty and practical significance of the work:


The acute and subacute toxicity of a newly synthesized silver selenide nanoparticles encapsulated in a natural polymeric matrix of arabinogalactan study has been studied. The nanocomposite is a promising material for the design of diagnostic and therapeutic drugs. It can also be used for the preparation of fluorescent labels and in thermal oncotherapy. The employment of binary nanocomposites enables one to unveil the potential hidden in metals which constitute these composites. The study of acute toxicity, carried out by the oral administration of nanocomposites at a dose of 2000 mg/kg, has shown that the compound belongs to low-toxic substances of the 5th hazard class. With the subacute oral administration of nanocomposites at a dose of 500 μg/kg, slight changes are observed in the brain tissue and liver of experimental animals, indicating the development of compensatory–adaptive reactions. In the kidneys, the area of the Shumlyansky–Bowman chamber decreases by 40.5% relative to the control group. It is shown that the application of the protective properties of selenium, which is contained in the composite, helps to reduce the toxicity of silver. Silver selenide is a promising material for the creation of biomedical theranostic preparations. Due to the fact that the silver selenide luminesce is in the region of electromagnetic radiation that is not absorbed by biological tissues, the application of its quantum dots (QDs) as fluorescent labels seems to be prospective ,2. SilveThe improvement of the bioavailability of metal nanoparticles as well as the reduction of their possible toxicity represents an urgent challenge. In this regard, the synthesis of metal-containing nanocomposites using high-molecular compounds, for example, arabinogalactan (AG) of Siberian larch ,16, appeThe polymer is isolated from larch wood, where its content reaches 15%. The specified polymer is a biologically active substance with a wide spectrum of activity. It is found that it possesses good gastroprotective, immunomodulatory, membranotropic and antioxidant properties ,20,21. IThe unique characteristics of silver selenide nanoparticles encapsulated in a natural polymer matrix of AG open up wide possibilities for its application, at the same time being possible reasons for adverse effects.In the present work, the morphofunctional state of the tissue of the sensorimotor zone of the cerebral cortex and the hepato-renal system during the acute and subacute administration of silver selenide nanoparticles encapsulated in a natural AG polymer matrix has been evaluated.3 was added to 100 mL of aqueous solution containing 3.4 g of AG under vigorous stirring at room temperature. After 10 min of stirring, 225 µL of reaction medium containing Se2−-anions, previously generated from powdered elemental selenium in the basic-reduction “hydrazine-hydrate-alkali” system [3). The formation of Ag2Se nanoparticles was identified by the appearance of brown staining of the reaction medium and the absorption spectrum characteristic of Ag2Se. The synthesis time was 20 min. The nanocomposite was isolated by precipitation from the reaction medium in a 5-fold excess of ethanol.The nanocomposite was synthesized according to the slightly modified method described in . Namely,2Se-AG—Found (%): C, 38.5; H, 5.6; Ag, 2.9%; Se, 1.1%.The optical absorption spectrum of the nanocomposite aqueous solution was recorded on a Perkin Elmer Lambda 35 spectrophotometer  in a 1 cm quartz cuvette. X-ray diffractometer Bruker D8 ADVANCE ,  was used for the X-ray diffraction study. Transmission electron microscopy (TEM) was performed on a Leo 906 E transmission electron microscope . The size distribution of nanoparticles was determined by statistical processing of microphotographs. The elemental composition was determined by X-ray energy dispersive microanalysis on an electron scanning microscope (SEM) Hitachi TM 3000 with X-ray detector SDD XFlash 430-4 and on CHNS-analyzer Flash 2000 company Thermo Scientific . AG—Found (%): C, 39.5; H, 6.39; AgFor the study purposes, animals were randomly selected, labeled with individual identifiers, and kept in their cages for three to four individuals each for 5 days prior to dosing to allow them to adapt in the laboratory. The absence of external signs of diseases and the homogeneity of groups by body weight (±20%) were considered as a criterion for the acceptability of randomization. Prior to dosing, the animals remained fasted for 3–4 h with free access to water. Animals of the experimental and control groups were kept under the same environmental conditions in the chambers.Experimental animals were born by their own reproduction in the vivarium of Federal State Budgetary Scientific Institution “East Siberian Institute of Medical and Ecological Research” (FSBSI ESIMER) and kept on a standard diet. Maintenance and care of experimental animals were carried out in accordance with the interstate standard GOST 33216-2014 (Russia).All animal experiments were approved by the ethical committee of FSBSI East-Siberian Institute of Medical and Ecological Research . All manipulations with experimental animals were performed in accordance with the rules of humane treatment of animals in accordance with the requirements of the International Recommendations for Biomedical Research Using Animals .2Se nanoparticles encapsulated in a natural polymer matrix of arabinogalactan (Ag2Se-AG)) was determined by the intragastric route of administration on outbred white male mice weighing 21–32 g .The acute toxicity method  is a ste2Se-AG nanocomposite was performed using the limiting dose (2000 mg/kg of body weight). The test substance was administered orally to white mice of the experimental group with an atraumatic probe at a dose of 2000 mg/kg in 0.9% NaCl. At the same time, the volume of the injected solution did not exceed 0.5 mL. Dosing accuracy was achieved by changing the volume of the injected solution at its constant concentration. Animals of the control group were orally administered in an equivalent volume of 0.9% NaCl (placebo). The doses were prepared immediately prior to the administration. Before the introduction of the test dose, the animals were weighed and the administered dose was calculated at the rate of 2000 mg/kg of body weight. Prior to dosing, mice remained fasted for 3–4 h with free access to water. Food was absent for another 2–3 h after introduction of substance.The acute toxicity test of the AgAnimals were observed daily for 14 days, with particular attention paid to the first 4 h after administration of the test dose. The appearance and disappearance of the external signs of poisoning were assessed: changes in the skin and coat, eyes and mucous membranes, respiratory, circulatory, autonomic and central nervous systems, as well as somatomotor activity and behavior, the appearance of tremor, convulsions, salivation, diarrhea, lethargy, sleep and coma . Then th2Se-AG on white male rats weighing 200–220 g . In case of subacute exposure, the experimental group of animals was intragastrically injected with the studied nanocomposite at a dose of 500 mg/kg of body weight in 1 mL of distilled water for 10 days. This dose was chosen based on the results of previous investigations and was 1/4 of LD50. The choice of dose is due to previous studies of the toxic properties of nanocomposites of other metals  [n = 10) received 1 mL of distilled water in the same mode. For histological studies of the nervous tissue, the animals were euthanized by decapitation.The study of the subacute effect of the nanocomposite was carried out with intragastric administration of Age, etc.) ,31,32,33The brain, liver and kidneys were isolated from each animal under study and fixed in a neutral buffered 10% formalin solution . The brain was dehydrated with isopraponol  and placed in HistoMix homogenized paraffin medium for histological studies . Using a HM 400 microtome , serial frontal paraffin sections of the brain were made for subsequent staining with hematoxylin–eosin for survey microscopy. The nervous tissue of the temporo-parietal zone of the sensorimotor cortex of the brain was studied as a nerve center that provides the regulation of the basic physiological functions of the body and complex forms of behavior . The livp ≤ 0.05.Statistical analysis of the research results was carried out using the Statistica 6.1 software package. To compare the groups, the Mann–Whitney U-test was used. Changes in the studied parameters were considered statistically significant at a significance level of 2Se-containing nanocomposite based on AG with a quantitative content of the inorganic phase of 4%w was synthesized out in aqueous medium via the ion-exchange interaction of selenide anions Se2− ) and Ag+ ions, according to Equation (2), in the presence of AG macromolecules.The water-soluble Ag2Se nanoparticles and the support of their aggregative stability are probably performed by the adsorption of the polysaccharide macromolecules on their surface (steric stabilization) as well as due to the electrostatic stabilization of the Ag2Se particle surface by the highly-polar functional AG groups . A single hybrid stable water-soluble system “nanocore—Ag2Se/shell—polysaccharide matrix” is formed.The passivation of the energy-saturated surface of Ag2Se-AG nanocomposite (4%w Ag2Se) is formed as spherical Ag2Se nanoparticles dispersed in the polysaccharide matrix of AG. The particle size varies between 4–16 nm with an average value of 9.6 nm. , characterizing the presence of silver selenide with a cubic crystal lattice (α-Ag2Se) in the composite obtained [2Se  [According to the data of transmission electron microscopy, the Ag 9.6 nm. a. Using obtained . In addi2Se nanocrystallites, calculated by the Scherrer formula, is 11.2 nm which correlates well with the TEM data (The average size of AgTEM data c. The ex2Se nanocomposite (4%w Ag2Se) were studied by optical spectroscopy in the visible region of the spectrum at room temperature. It was found that the absorption spectrum is characterized by the absence of well-resolved maxima, probably due to the relatively large size of Ag2Se nanoparticles and their wide dispersed distribution, which is confirmed by TEM data.The optical properties of an aqueous solution of AgEg) of the Ag2Se nanoparticles in the AG matrix can be calculated by Tauc’s plot method. The basis of this method is the suggestion of the possibility to present the absorption coefficient α in the form of the equation:Eg is the band gap energy, h is Planck’s constant, ν is the photon frequency and B is a constant. We chose the factor γ, which depends on the nature of the electron transition, as 1/2, assuming the direct character of the transitions [2Se nanoparticles was higher (3.2 eV) than the value of 0.16 eV reported earlier for bulk Ag2Se [2Se nanoparticles compared to the value of bulk silver selenide may be due to the decrease of the particle size and appearance of the quantum confinement effect.The value of the optical band gap energy  per unit area had no statistically significant differences from the control values. The number of neuronophagy events in animals that received the nanocomposite was statistically significantly higher than in the control group .With the acute oral administration of the nanocomposite to white mice at a maximum dose of 2000 mg/kg of body weight, no mortality was noted during the entire observation. This, together with the absence of changes in internal organs during the macroscopic investigation, allows us to classify the studied Ag50, when administered intragastrically at a dose of more than 5000 mg/kg of animal weight, disorders the structure of the nervous tissue, increases the area of mitochondria, violates the structure of nerve cells and activates the apoptosis process [Many researchers have shown that exposure to silver nanoparticles in low doses leads to the emergence and development of neurotoxic effects ,40,41,42 process . At the  process ,44. SilvIn turn, exposure to individual selenium nanoparticles, also encapsulated in a polymeric matrix of arabinogalactan, at a dose of 500 μg/kg of animal body weight reduced the total number of neurons and astroglial cells per unit area in the sensorimotor zone of the cerebral cortex and increased the degeneratively altered neurons and the number of neuronophagy acts, which indirectly indicated both the penetration of the nanocomposite through the blood–brain barrier and the pronounced neurotoxic effect of selenium nanoparticles . ExposurThe absence of such effects upon exposure to silver selenide encapsulated in the arabinogalactan polymer matrix is apparently due to the simultaneous presence of nanoparticles in the nanocomposite and, possibly, to their competition for binding to the cell receptors of cerebral cortex neurons.2Se-AG nanocomposite indicates the activation and development of compensatory repair processes in the liver and stimulation of cell regeneration mechanisms, while the constant amount of Kupffer stellate macrophages evidences no inflammatory process in the liver tissue. According to the data given in [An increase in the number of polynuclear hepatocytes upon the subacute administration of the Aggiven in , silver given in . The hepgiven in . At the given in ,49,50. T2Se-AG at a dose of 500 μg/kg showed a 40.5% decrease in the area of the Shumlyansky–Bowman capsule , which the norm ,53,54. Mthe norm . PerhapsThe administration of the nanocomposite to rats for 10 days at a dose of ¼ of LD50 had a different degree of severity depending on the place of application. Of the greatest interest was the nanocomposite effect on the tissue of the cerebral cortex. The experimental studies revealed no changes in the ratio of the cellular elements of the sensorimotor zone of the cortex. Morphological disturbances of neurons were also not observed in comparison with those in control animals. In the tissue of the cerebral cortex, attention was drawn to higher acts of neuronophagy, indicating an increase in the formation of glial nodules, through which damaged or degeneratively altered nerve cells were destroyed and removed from the body with the help of macrophages. Thus, silver selenide nanocomposites, without a pronounced neurotoxic effect, still increase the number of dead neurons. It might be possible to address this issue by studying the effects of silver selenide on brain tissue in the late post-contact period.The conducted studies revealed that the toxicity of the silver selenide nanocomposite in the arabinogalactan polymer matrix is much less pronounced than that of silver or selenium nanoparticles alone. Apparently, this fact may be due to the competitive relationship of nanoparticles. At the same time, selenium, being a physiologically important trace element that is part of glutathione peroxidase, may be an antagonist for silver particles. The literature describes the antagonistic properties of selenium for such heavy metals as mercury, arsenic, lead and cadmium . Given tIn conclusion, the study of the acute toxicity of a silver selenide nanocomposite has shown that the substance belongs to the low-hazard class. The evaluation of the subacute toxicity of a silver selenide nanoparticle encapsulated in an arabinogalactan polymer matrix to white rats does not reveal any significant changes in the tissue structure of the sensorimotor cortex and liver of animals, along with minor changes in the kidney tissue. In this connection, the silver selenide nanocomposite encapsulated in a polymer matrix is a promising preparation for further biomedical research.


The rheological phenomenon of rock mass affects the long-term safety of rock mass engineering. In this study, gneiss samples with different 3D morphologies are prepared by splitting tests and are tested through multi-step creep tests. The long-term strength of rock discontinuities is determined by using several methods. The test results show that as the 3D morphological parameter increases, the creep deformation, creep rate, and the duration of failure all decrease. The long-term strength of rock discontinuities is linearly related to the 3D morphological parameter. Based on the principle of damage mechanics for rock mass, a damage variable is introduced in the creep model, and an improved non-linear Burgers model is established. Research results are of great theoretical significance and practical value for the design, construction, and long-term safety of rock mass engineering. The discontinuity of rock mass, as the weak structural planes in rock mass, plays a controlling role in the mechanical properties of rock mass . The exiExperimental study is an important and indispensable means to study the creep characteristics of rock mass. At the beginning of the last century, the study of creep behavior started and many researchers have published works on the creep characteristics of rock and rock discontinuities in the past decades ,7,8,9,10Different from intact rocks, the complex surface properties of rock discontinuities control the mechanical behavior of rock discontinuities. Previous research studies have shown that the morphological properties of rock discontinuities are one of the important factors which remarkably affect the strength and deformation characteristics of rock discontinuities under creep conditions ,15,16,17In this study, based on the 3D roughness evaluation method for discontinuities, multi-step creep tests are conducted on natural rock discontinuities formed by splitting . The creAll the samples for this test were obtained from natural gneiss blocks with 100 mm × 100 mm × 100 mm (L × W × H). In order to simulate the natural rock mass discontinuities, the discontinuities were obtained by Brazil split tests in the direction parallel to that of the gneiss schistosity, as shown in n refers to the number of effective shear dips on the whole rock discontinuities surface. The morphological characteristics parameter Z2 takes the shear direction of rock mass discontinuity into consideration, and the anisotropy of the discontinuity is considered in the evaluation process. The samples with different As Zhang et al.  stated, inuities ,25. In ti et al. , Zhang ei et al.  have proThe shear creep tests of discontinuities were carried out on a servo-controlled biaxial rheological testing machine (CSS-1950) in Tongji University . The maxThe basic mechanical parameters of rock mass discontinuities are determined through relevant basic mechanical tests. The average uniaxial compressive strength (d 1.6 mm a. The reThe creep curve of p-c-1 at the last stress level was selected and the relationship between creep deformation and creep rate was shown in The surface morphology of the rock discontinuities affects the creep characteristics. As Dv = ΔD/Δt). The creep rate slowly increased as the shear stress increased in previous loading steps, and when the shear stress level exceeded a certain value, the creep rate increased significantly. For example, the initial creep rate of p-c-1 was almost constant in the previous five shear stress levels and then increased suddenly when the shear stress was 4.32 MPa  in the time interval from creep initiation to failure was used to represent the damage during the creep process. The expression of the damage variable can be assumed as follows:b refers to a constant related to the discontinuity material, which is greater than 0. When t = 0, D = 0; when t = tb, D = 1, of which tb refers to the time that the sample is damaged. Based on the non-linear Burgers model, the damage variable was introduced to express the stress of the second part , the creep test data are fitted to obtain the fitting parameters of the non-linear Burgers model based on damage mechanics in (1)For the same normal stress, the 3D morphological features of discontinuities have a great influence on the shear creep characteristics. As the 3D morphological parameter increases, the duration of failure decreases and the damage is more intense. The creep deformation and creep rate decreased with increasing (2)The long-term strength range of discontinuities determined by transient creep method and the long-term strength value further determined by inflection point method are in good agreement. The long-term strength increases linearly with the increase of (3)Based on the non-linear Burgers model, a damage variable of discontinuities is employed, and an improved model considering damage mechanics is further proposed. This model can describe the accelerated creep characteristics of discontinuities and fits well with the experimental data under each stress level.In this paper, a series of shear creep tests of rock discontinuities was carried out to study the effect of 3D morphological features on the shear creep characteristics of rock discontinuities. Research results are of great theoretical significance and practical value for the design, construction, and long-term safety of rock mass engineering. The conclusions are summarized as follows:


Structural changes occurring in the glasses during doping with erbium ions were investigated using positron annihilation lifetime spectroscopy (PALS) and Raman spectroscopy. The X-ray diffraction (XRD) method was used to confirm the amorphous structure of the investigated samples. Based on the Faraday effect measurements and calculated values of Verdet constant, the magneto-optical properties of the glasses were determined.In this article, we present research on the influence of erbium ions on the structure and magneto-optical properties of 70TeO Their concentrations are presented below:The X-ray diffraction scans measured for the tellurite glasses are shown in 3+ was carried out in two stages. First, the obtained results were considered using a two-state trapping model. In the following work, two-state and Tao–Eldrup models were used to determine the basic parameters describing the centers of positron annihilation in the investigated tellurite glasses. The research was a preliminary analysis of the internal structures of materials. 1 and τ2 and their intensities I1 and I2  in the tested tellurite glasses doped with erbium ions, we considered two parameters obtained from the measurements, namely the lifetime values τ3 and its intensity I3. The o-Ps lifetime values τ3 and their intensities I3 are given in In all the investigated tellurite glass systems, the third component τd so far ,21. Obta−1 (bending vibrations of Te-O bonds), 600–900 cm−1 (stretching vibrations of Te-O bonds), and 940–1120 cm−1 (stretching vibrations of P-O bonds) [O bonds) ,27,28,29As shown in −1) indicates an additional role of titanium ions. However, due to the large half-width of the bands , it is not easy to precisely interpret the spectra in question. Therefore, it was necessary to decompose them into component bands . It indicates an increase in the degree of polymerization of the bond due to the formation of Te-O-Ti bridges. Thus, in the bond of the tested glasses, titanium ions play the role of network ions, and in this case, we are dealing with a tellurite–phosphate–titanium bond.As it is clear to see, the decompositions of individual spectra show the same bands, the assignment of which to the respective vibrations is presented in 3 units (E and F bands) at the expense of the intensity of the bands associated with TeO4 units (D and C bands). This effect is invisible with glasses containing titanium ions (S5–S6 pair), indicating that the titanium ions stabilize the tellurite subnetwork. The depolymerizing effect of erbium ions is also visible in the analysis of the phosphate subnetwork.The comparison of the decomposition of individual spectral pairs  also allows assessing the influence of erbium ions on their structure. The intensity of the integral individual bands  shows th0, Q1, and Q2 units were found in all tested glasses (where Q is the number of bridged oxygen). The analysis of the corresponding glasses shows that the introduction of erbium ions leads to a decrease in the intensity of the bands associated with Q2 units. It indicates the depolymerization of the truss. Thus, it can be concluded that the erbium ions depolymerize only the phosphate subnetwork in S6 glass and simultaneously the tellurite and phosphate subnetwork in the case of S2 and S4 glasses.Based on the Raman spectrum , Q0, Q1,The measurements of the Faraday effect confirmed the possibility of observing the phenomenon of torsion of the plane of light polarization under the influence of the longitudinal magnetic field in each glass system. The maximum error of the Verdet constant estimation was 4%. The greatest increase for the Verdet constant was observed for glasses where the modifier was titanium oxide. For the glass doped with erbium ions, the increase in the Verdet constant was more than 25% as compared with the glass containing bismuth oxide. Doping the glasses with paramagnetic erbium ions increases the angle of rotation of the plane of light polarization under the influence of the magnetic field in all tested glasses. Further research will be aimed at developing the optimal amount of erbium impurity in order to obtain the maximum value of the Verdet constant for the tested materials.2-5XO-10P2O5-10ZnO-5PbF2, where X = Pb, Bi, Ti) were poured into a brass mold at a temperature of 330 °C. The samples were annealed at 320–340 °C for 2 h to remove any stresses developed in the material. Before starting the tests, the obtained glasses were carefully machined to form samples with geometrical parameters required for the measurement methods used. The nominal compositions of investigated glasses are summarized in Melted 5 g sets of tellurite glasses . Positron lifetime measurements were performed using an Ortec start-stop spectrometer . The spe program . The LT −1, were collected and averaged.The Raman spectra were obtained using a WITec confocal CRM alpha 300 Raman microscope equipped with an air-cooled solid-state laser, emitting wavelengths of 488 nm and a CCD detector cooled down to −82 °C. The power of the laser ranged from 14.4 to 14.6 mW, 120 or more scans, with integration time of 0.3–0.5 s and resolution equal to 3 cmX-ray diffractometry (XRD) was used to determine the phase constitution of the glasses. The XRD patterns were collected using a Bruker D8 Advance diffractometer with CuKα radiation equipped with a LynxEye detector. In order to obtain XRD data representative for the entire volume of the material, the samples were crushed to powder.The magneto-optical properties of all investigated glass systems were determined based on the measurements of the Faraday effect as well as the calculations of the Verdet constant based on the value of the twist angle of the plane of light polarization. The maximum error in determining the Verdet constant was 4%. The measurements of the Faraday effect were carried out on a specially built measuring setup. Measurements of the angle of rotation of the polarization plane were made for a light wave ranging from 450 nm to 650 nm in a base magnetic field with an induction of 0.06 T. More information about the measurement method can be found in .The XRD measurements confirmed the amorphous nature of the tested tellurite glasses.3+ ions into glass matrix caused changes in the parameters describing the structure of the glasses. We noticed that doping glasses with erbium ions clearly changed the positron trapping rate and the fraction of trapped positrons. Results of these measurements show that due to doping of tellurite glasses with erbium ions containing the optimal amount of erbium oxide (1200 ppm), it is possible to obtain the τ3 component and its I3 intensity, values related to the formation of ortho-positronium as well as the distribution of the density of the formation of free volumes. Notably, the research for the tellurite glasses presented in [Incorporation of the paramagnetic Erented in  could no3+ ions into the structure of the tellurite glass breaks the Te-O-Te bridges and leads to the formation of new Te-O-Er bonds. The results of Faraday effect measurements indicate the possibility of changing the magneto-optical properties of tellurite glasses by the incorporation of various modifiers into the network and doping with rare earth metal ions.Raman spectroscopy reveal that the introduction of ErAnalyzing the obtained results of the conducted research, it was found that doping of tellurite glasses with erbium ions has significantly affects, with changes in the micro and nano structural properties.


In this paper, the results from studies regarding near-eutectic Al-Si alloys with Sn as an alloying addition are presented. In most Al-Si alloys, tin is regarded as a contaminant; thus, its amount is limited to up to 0.3 wt.%. The few studies that can be found in the literature regarding the behaviour of tin in aluminium alloys suggest the beneficial effect of this element on selected properties. However, these results were obtained for hypereutectic Al-Si alloys or wrought aluminium alloys. In our studies, the influence of tin contents of up to 1.7 wt.% was determined on the AlSi10 alloy. Thermal analysis, measurements of the mechanical properties of the cast and heat-treated alloy, metallographic observations , and EDS (X-ray energy dispersive spectrometry) measurement allowed us to fully describe the effect of tin on the aluminium alloy. The results of the thermal analysis showed changes in the range of the α-Al solution crystallisation and the α+β eutectic through a decrease in the alloy’s solidification start point and eutectic solidification point. As a result, the elongation of the alloy was more than double in the AlSi10Sn1.7 alloy, with an A5 value of 8.1% and a tensile strength that was above 200 MPa. The exceptional popularity of aluminium alloys in the automotive ,2,3,4,5,The literature discusses detailed aspects of selecting aluminium alloys as lightweight materials as well as recent developments in the use of aluminium alloys in passenger cars and aviation for structural and engine components.Both of the traditional techniques for manufacturing aluminium alloy components have been discussed, which include casting , metal-fThrough the introduction of alloying elements, aluminium alloys are characterised by very good mechanical properties, high plasticity, and satisfactory hardness ,16. TheyIn ref. , an analInformation about the exclusive influence of Mg, Ni, Cu, Ti, Mn, Be, Fe, and Sn can be found as well as the synergic effect of some of these. A similar approach was presented in ref. , where lThe addition of tin has also been evaluated; however, it can be stated that, compared to other elements, tin remains insufficiently analysed. The sparse experiments in this area show that the addition of Sn into Al-Si alloys can perform many functions that allow for obtaining a balance between the strength and wear resistance of this alloy group ,46,47,48During the analyses of the previous research, it can be stated that the addition of tin resulted in a considerable microstructure refinement, along with the even distribution of tin and silicon inside the α-Al alloy matrix of the Al-Si-Sn alloy. It is worth adding that such an effect was recorded for 25 wt.% Sn in the alloy; for such a content, a considerable increase in the wear resistance and reduction in the surface pressure were demonstrated. The addition of tin made these alloys less prone to abrasion than base aluminium–silicon alloys ,50,51.The tin effect on the hardness and tensile strength of the A390 alloy was researched as well , where iThe main aim of our research is to determine the method of interaction of tin additives that are introduced into aluminium-silicon alloys. -charge materials;-furnace with accessories;-moulds for making castings;-thermal analysis equipment.This research aimed to analyse the melting technology and casting of aluminium alloys, focusing on an example of the AlSi10 alloy with tin additions that were within a range of 0.2–1.7% . The scoAs part of the research, melts that contained the planned chemical composition were conducted. The quality of the liquid alloy was determined in terms of the hydrogen content, and the refining process was carried out based on the reported needs. Individual alloys were poured into prepared moulds, and the temperature changes of the alloy during the solidification and cooling were registered.The obtained castings were tested in terms of tensile strength, plasticity, and hardness. Metallographic observations of each alloy were also carried out using optical and scanning electron microscopy (SEM). The microstructure was observed in electron backscattered (BSE) contrast in order to better differentiate the formed phases according to their mean Z numbers. Additionally, the SEM equipment provided the opportunity to carry out an elemental analysis of the microregions with X-ray energy dispersive spectroscopy (EDS).The additions were selected on the basis of their own experimental research so as to show the effects of Sn at different contents. The selection of the amounts of the additives was also preceded by an analysis of the phase diagrams ,61,62,63The alloy-melting process was carried out in an electric induction furnace of a medium frequency with the use of a chamotte–graphite crucible. The crucible was cleaned of any metal residues and skim from the previous melting process.Ingots of the AlSi7Mg0.3 alloy  were used as the main charge. The alloy with a composition that was similar to theeutectic alloy (AlSi10) was obtained by adding crystalline silicon and master alloys .Before charging the batch, the furnace was heated to remove any moisture from the crucible that could adversely affect the molten alloy. After the metal charge had melted, the bath was heated to a temperature of 750 °C, and the weighed amount of silicon was introduced as we waited for its dissolution. Due to the tendency of aluminium alloys to dissolve hydrogen, the quality of the metal bath was controlled, and gas refining (argon) was used. The metal-preparation process was carried out in such a way as to eliminate any gaseous impurities and solid inclusions that could have distorted the obtained results.The well-prepared alloy was used to perform the planned research on the impact of variable tin additions to the AlSi10 alloy.Ready alloys were cast into a metal mould in order to obtain castings for further research.The chemical compositions of those alloys that were obtained according to the planned experiment were determined by an spark optical emission spectrometer (OES) . The chemical composition of the obtained alloys is presented in To assess the influence of the variable tin additions to the AlSi10 alloy, sample castings were made in metallic dies; these allowed for making castings in the shape of the sample for testing the mechanical properties. Before casting, the mould was heated to within a temperature range of 150–200 °C. The pouring temperature of the liquid melt was within a range of 730–750 °C. The set mould and melt temperatures were used for all of the scheduled melts.Those castings that were made with the use of a metal mould were tested to determine their chemical composition, HBS hardness, UTS tensile strength, A elongation, microstructure, and machinability assessment.With the use of thermal-derivative analysis (TDA), the characteristic thermal effects that resulted from phase changes that occurred during the crystallisation of the tested AlSiSn alloys were recorded and determined. For the thermal analysis, a mantle K-type (NiCr-NiAl) thermoelement (diameter—0.5 mm) was used with a centrally located thermocouple at the top. The temperature measurements were made by a Keysight 34972A laboratory multimeter  equipped with a 16-channel Module 34902A Reed Multiplexer. The obtained data made it possible to conduct a thermal analysis of the tested AlSiSn alloys.On the basis of the TDA curves and thermodynamic modelling, investigations of the phase analysis were also made. The thermodynamic analysis of the alloys was performed on the basis of the CaLPHaD method (CALcula-tion of PHAse Diagrams) with a packet Thermo-Calc ver. 3.1 for aluminium alloys TCAL2: TCS Al-based Alloy Database (TCAL).Metallographic microstructure observations were carried out by optical microscopy  together with a camera and Nis-Elements  image recording and analysis software ver. 3.22.15(Bulid 738). The SEM-EDS analyses were carried out with a Hitachi S-3400N electron microscope  with a tungsten filament as an electron source and an EDS detector by Thermo Noran. In addition, some SEM studies (including electron backscattered diffraction [EBSD] and an EDS element distribution map) were carried out with a Tescan Mira  with an FEG electron column, SW version 1.1.3.0 buulid 4348, an EBSD Symetry S2 , and an EDS Ultim Max .The UTS tensile strength and A elongation (number of tests—5) were determined by a LabTest ZD20 Labor Tech (V = 10 MPa/s), while the Brinell hardness HBS 2.5/62.5 measurements (number of tests—3) were made using an HPO-250 hardness tester . The strength tests were carried out on samples without machining (as cast); this made it possible to evaluate selected properties of the analysed alloys without machining while at the same time allowing us to obtain results that determined the nature of the changes that occurred for the real castings that were machined only in certain important places.Determining the mechanical properties of the analysed alloys was carried out in accordance with current standards while ensuring the accuracy of the measurements.Machinability tests were carried out using the Keep-Bauer method ,65. ThisThe recording of the solidification and cooling of the analysed alloys allowed us to analyse the changes that occurred in the AlSi10 alloy with variable tin additions. An aggregate diagram of the alloy’s crystallisation is shown in The thermal-derivative analysis made it possible to determine specific characteristic temperatures such as the beginning of the T1 crystallisation, the crystallisation of the T2 eutectic, the crystallisation of the T3 and T4 intermetallic phases, and the temperature at the end of the T5 crystallisation  and the SI -DIAMOND_A4 phase . In addition, there were phases with lower percentages: the AL9FE2SI2 phase, the AL3TI_D022 phase, and the AL2CU_C16 phase. These were multi-component phases that contained Fe, Ti, and Cu in the alloy. The Q_ALCUMGSI phase crystallised only in the AlSi alloy. The disclosed phase in the ThermoCalc modelling was the MG2SI_C1 phase, which changed its composition to Mg2Sn with a very low Si content when tin was added to the alloy. Tin was present in the alloy as a practically pure element in the form of the BCT_A5 phase. The content of the individual elements in the phases that occurred during the alloy crystallisation is presented in The results of the modelling of the alloys and the percentages of the individual phases that were obtained at an ambient temperature (20 °C) are presented in Selected results of the metallographic tests (OM) are presented in The obtained castings from the analysed alloys were also subjected to T6 heat treatment  (resistance muffle furnace—PEM-2). Selected results of the metallographic tests of the AlSi10Sn alloys after the T6 heat treatments are shown in The studies that were carried out with the use of the scanning electron microscope allowed us to observe changes in the microstructure and identify the shapes of the tin precipitates that were used as an alloying addition to the AlSi10. These test results are presented in Based on the electron and EDS images, the phase image was obtained: Al (α); AlSi (α+β); Si (β); SnAl (Sn) (denoting pure tin); AlSiSn; SiAl (Si) (denoting pure silicon) .The EBSD analysis confirmed the presence of the following phases in the Al-Si-Sn alloy: aluminium, silicon, tin, Mg2Si, and Mg2Sn1.1 a,b. In FStrength tests were carried out on the samples without machining; this allowed for an evaluation of selected properties of the analysed alloys without machining and, at the same time, allowed for obtaining the results that determined the nature of the changes that took place for the real castings . The results of the obtained tests are presented in The obtained and analysed results indicated a slight decrease in the tensile strength of the analysed AlSi10 alloys that had increased tin content. The plasticity of the tested alloys (determined by elongation parameter A) improved slightly. The results of the hardness tests of the AlSi alloys with variable tin additions are presented in The obtained Brinell hardness (HB) values of the analysed alloys did not show any significant changes from the impact of the variable tin additions (up to 1.7%).The next stage of the research included assessing any changes in the machinability of the analysed alloys. The results of these tests are presented in An analysis of the obtained results showed the clear influence of the variable tin additions to the analysed AlSi10 alloy. With increases in the proportion of tin, the crystallisation temperature of the α-Al solid solution decreased, and the supercooling effect in this area disappeared. This is related to the formation of the nuclei of the crystallisation, the growth of the dendrites of the solid solution, and the thermal effect of the process. Changes could also be observed in the area of the α+β eutectic solidification.The solidification point of the T2 eutectic decreased from a value of 578.0 °C  to a value of 575.2 °C . For all of the analysed alloys, a recalescence effect could be observed, i.e., supercooling in the initial area of the eutectic crystallisation. The range of the T1–T5 crystallisation also expanded.According to the TC modelling, the addition of tin to the AlSi10 alloy caused its appearance in the process of the crystallisation of the second liquid (“LIQUID_2”), which was difficult to detect in the case of the TDA.The obtained results of the TC modelling and TDA were convergent in terms of the crystallisation start temperature and eutectic crystallisation temperature—the differences were maximums of 7 °C and 2 °C, respectively. This convergence was mainly due to the relatively high proportion of aluminium and silicon. The remaining elements that remained in smaller proportions and occurred as alloying additives  or were present as impurities  caused thermal effects during the crystallisation; however, they did not directly correlate with each other.A microscopic observation clearly showed the presence of eutectic silicon in the α-Al solid solution.The metallographic tests of the analysed AlSi10 alloys with variable tin additions showed the dendritic nature of the structure of the α-Al solid solution and the precipitations of eutectic silicon in the interdendritic spaces; these are especially visible in the photos that were taken at a 50× magnification.For those alloys without heat treatment, the eutectic showed an unmodified state, with the silicon in the forms of plates/needles that were arranged in a disordered manner (sometimes forming the shape of a eutectic grain). One can also notice the precipitation of larger silicon crystals—the structure of which indicates that these were the primary silicon. With this group of alloys—the near-eutectic group, and with the actual solidification conditions in the mould, which were significantly different from the equilibrium conditions, it is not excluded. The spheroidisation of the eutectic silicon precipitates can be observed in the images of the microstructure of the samples after T6 heat treatment. This phenomenon is well-known for AlSi alloys and leads to improvements in certain properties of such castings.The tests that were carried out with the use of the scanning electron microscope allowed us to observe changes in the microstructure and identify the form of the tin that was used as an alloying addition for AlSi10.The SEM-EDS analyses are shown in Based on the electron images, colour maps of the distribution of the elements in the microstructure were also made . Based oThe tin that was introduced into the AlSi10 alloy was visible in the form of very fine microdispersive precipitates in the matrix and as separate precipitates of aluminium and tin with variable amounts of other elements, such as magnesium, iron, manganese, and silicon.The applied EDS element distribution map revealed the form of the tin that occurred in the AlSi10 alloy.The tin-containing phases featured shapes that were somewhat aligned with the interdendritic spaces. In the area of the precipitates, slightly rounded depressions could be observed; this corresponded to the filling of the spaces around the dendrite arms. This may have been due to the accumulation of free tin or Sn-Al eutectic precipitates in the interdendritic spaces or around those complex intermetallic phases that were associated with the presence of iron and manganese in the alloy. The introduced tin accumulated in the spaces of these complex crystallised AlSiFeMn phases.The obtained and analysed results indicated slight decreases in the tensile strengths of the analysed AlSi10 alloys with increased contents of tin. The plasticity of the tested alloys (determined by elongation parameter A) improved slightly, and the obtained Brinell hardness (HB) values of the analysed alloys did not show any significant changes from the impact of the variable tin additions (up to 1.7%).The obtained curves that showed the speed of the penetration of the drill bit when drilling the Ø5-mm hole with a constant feed force showed the favourable variable effect of the tin addition. As the Sn alloy addition to the AlSi10 alloy increased, the drilling speed also increased. It can be assumed that the occurring tin-related precipitates caused chip breakage and thus reduced the cutting resistance.Tests were carried out for a near-eutectic AlSi10 alloy with variable tin additions that ranged from 0.2 to 1.7 wt.%. The produced alloys were cast into a metal mould.-A TDA of the obtained alloys showed changes in the onset of the solidification as well as in the solidification period of the eutectic. The addition of tin to the analysed AlSi10 alloy lowered the solidification point of the α-Al solid solution with the simultaneous disappearance of recalescence in this area. The eutectic solidification point also decreased by about 3 °C for the AlSi10Sn1.7 alloy.-2Si_C1 (Mg2Sn).Thermodynamic modelling using CAL-PHAD with Thermo-Calc software provided an overview of the crystallisation process of AlSi10 alloy with tin additives with special attention to the dual liquid phase . Tin occurs as separate separations of the BCT_A5 phase and in a phase with magnesium identified by Thermo-Calc as Mg-The metallographic tests that were carried out by light microscopy showed the classic structure of the microstructures of the analysed AlSi alloys. The solid solution of the silicon in the aluminium α-Al adopted a dendritic structure, and the eutectics that formed during the crystallisation were located in the interdendritic spaces. Eutectic silicon adopted the structure of the plates/needles in a random arrangement, and the T6 heat treatment caused the spheroidisation of the eutectic silicon precipitates.-2Si, and Mg2Sn. Tin was mainly visible in separate irregularly shaped particles and in small secretions in the form of the Mg2Sn phase.The studies, which were carried out using a scanning electron microscope, confirmed the thermodynamic modelling of CAL-PHAD . The EBSD analysis confirmed the presence of the following phases in the Al-Si-Sn alloy: aluminium, silicon, tin, Mg-The obtained results of the mechanical properties did not show significant changes in the tensile strength and hardness of the analysed alloys. As a result of introducing tin in amounts of up to 1.7%, the plastic properties (determined by elongation parameter A) improved—reaching a value of more than 6% for the AlSi10Sn1.7 alloy. The addition of tin significantly improves the machinability of the alloy, thus causing an increase in the speed of drilling a hole of a certain diameter at a constant feed force.The conducted research allowed us to draw the following conclusions:


For fat removal, three detergents  and 96% ethanol were tested, as well as the manual separation of fat. The methodology optimized in this study combined a digestion with 30% H2O2 at 65 °C, during 24 to 48 h, with a manual separation of the fat remaining after the digestion. All steps from the present methodology were tested in six types of polymers , to investigate if these procedures altered the integrity of MPs. Results showed that the optimized methodology will allow for the efficient processing of complex seafood samples with different fat levels, without compromising MPs integrity . Marine organisms are affected by the ubiquitous occurrence of microplastics (MPs) in the environment. Several protocols have been described to extract and quantify MPs in seafood, although their complex matrices, with high level of fat, can compromise the efficiency of MPs extraction. To solve this issue, the present study aimed to develop a detailed methodology suitable to process seafood samples with different levels of fat, namely fish and molluscs, from fresh and canned sources, including the immersive liquids from the cans. Sample digestion was tested using different solutions (10% KOH, 30% H The global production of plastics has continually and dramatically increased, from 1.5 million tons in 1950 to approximately 370 million tons in 2020 ,5,6,7 asSeafood is an important source of essential nutrients, especially high-quality proteins , unsaturated fatty-acids (including Omega-3), fat-soluble vitamins, and minerals, with nutritional and physiological importance for human health ,14. In aHowever, seafood samples, particularly from canned products, have specific characteristics that can compromising the methodologies usually applied for extractions of MPs from water ,24, sediTo solve this methodological issue, the present study aimed to develop a detailed protocol to extract and characterize MPs suitable to be applied to different matrices of seafood, such as fish and molluscs from fresh and canned sources, with different levels of fat. The proposed methodology for MPs recovery from seafood samples comprises the following stages: organic content digestion, fat post-digestion removal, filtration and analysis of retrieved MPs. A summarized schematic representation is shown in Six tests were conducted to optimize the digestion of a variety of seafood samples with different levels of fat . The efficiency of each digestion test was assessed through visual inspection and expressed as the percentage of digestion of the sample: 100%-total digestion of the sample, with no visible remains at the end of the test; 95%-digestion of almost the totality of the sample, with few visible remains at the end of the test; 75%-partial digestion of the sample, with visible remains at the end of the test; 50%-digestion of approximately half of the sample, with visible remains at the end of the test.After digestion, samples follow to the next step that is filtration. Nevertheless, for samples with high levels of fat, filtration was not possible because the filters clogged easily with the fat. Hence, five tests were performed to dissolve or remove the remaining fat in digested samples .The efficiency of each test of fat elimination was assessed through visual inspection, and expressed as the percentage of fat removed from the sample: 100%-total removal of the fat from the sample, with no visible remains at the end of the test; 75%-partial removal of the fat from the sample, with visible remains at the end of the test; 50%-digestion of approximately half of the fat from the sample, with visible remains at the end of the test; 25%-digestion of a small part of the fat from the sample, with visible remains at the end of the test. Solutions obtained from the digestion of samples with low levels of fat were directly subjected to vacuum filtration using cellulose nitrate membrane filters . The other samples, after fat removal, were also filtered using the same conditions.After filtration, filters were stored in glass Petri dishes, air-dried at room temperature for two days, and observed in a stereomicroscope (Leica EZ04). Microplastics were classified according to the type , color and size, and photographed. After the development of the optimized methodology for the extraction and characterization of MPs from seafood samples with different levels of fat, the full protocol was applied to known and common types of plastic polymers to evaluate possible effects in the integrity of MPs. The most common types of plastic polymers observed in marine litter  were tested, namely: low-density polyethylene (PE-LD), polyethylene terephthalate (PET), polyethylene (PE), acrylic (AC), polystyrene (PS), and lycra. In the laboratory, all MPs were manually produced from common items , and sieved through a 5 mm mesh to discard particles larger than 5 mm. An initial mass of 0.002 g of each type of polymer was used to test MPs integrity with all the laboratorial procedures optimized in this study more in . Seafood sampling was made in a laboratory with restricted access. A clean laboratory coat  and single-use nitrile gloves were used during the entire processing. All working surfaces were thoroughly cleaned with 70% EtOH, and all glassware and metallic tools were rinsed with filtered deionised water and 70% EtOH before use. The outer part of the fish and seafood cans were also rinsed to eliminate any potential particles attached to the surface. Liquid solutions were regularly observed under a stereomicroscope to assess the occurrence of MPs contamination; if necessary, solutions were filtered through sterile cellulose nitrate membrane filters (pore size 0.45 µM) prior to use. Procedural blanks (a glass Petri dish with filtered deionised water) were left exposed in the cabinet of the laboratory where all steps were performed to capture any possible airborne contamination, and immediately observed at the stereomicroscope.The efficiency of the sample digestion tests was assessed through visual inspection, and results were provided in percentage of organic matter digested as described in the experimental section .Tests A1 and A2  presented an incomplete digestion of the organic matter during the entire experiment, where a maximum digestion rate of 95% was observed for all the samples after 72 h of incubation. The final solution obtained from the digestion presented a viscous consistency, with an orange to reddish coloration for all the samples tested. In the fresh fish gills samples, bony remains from the branchial arches persisted undigested.2O2 at 40 °C and 65 °C, respectively), a complete digestion of the organic matter (100%) was achieved for all the samples at the incubation times of 48 and 72 h, except for the fresh fish gills samples. For the later, an incomplete digestion rate of 95% was obtained for the two incubation periods (48 and 72 h), with undigested bony remains from the branchial arches of the gills.Regarding tests B1 and B2  and C2 , with an incubation period of 48 h, a complete digestion (100%) of the organic matter was generally achieved. An exception was observed for the samples presenting bony structures , where a digestion rate of 95% was observed, with undigested remains. For all the samples tested in C1 and C2, the digestion of the organic matter originated the development of fat. For samples with lower levels of fat small lipidic droplets were formed. In samples with high levels of fat, a lipidic layer was formed at the surface of the digested solution. Comparing the fat portion at the end of the digestion period for tests C1 and C2, there was a visible decrease in the levels of fat in test C2, with all the samples presenting smaller droplets or layers of fat-a very important feature for samples with high levels of fat. The visual inspection of the samples after 24 h of incubation demonstrated a complete digestion of the organic matter from the canned oil and canned sauce samples (100%). Concerning tests C1 (30% H2O2 (with a volume capable of covering the entire sample), incubated in a laboratory oven at 65 °C for 24 to 48 h (the incubation time differs according to the characteristics of the sample).So, the protocol chosen for the sample digestion was the C2: pre-treatment of seafood samples in a laboratory oven at 40 °C overnight, and sample digestion carried out with 30% HThe efficiency of the tests for fat post-digestion treatment was assessed through visual estimation, and results were provided in percentage of fat removal .The three tests using surfactant compounds (D–F) presented similar results, with all of them showing an incomplete fat dissolution in all the tested samples. For samples with higher levels of fat (canned oil and canned sauce), the percentage of fat removal was comparably lower (25%) than from the other samples (50%). Further, tests D, E and F also led to the formation of bubbles , which limited the sample visualization and the following steps of the protocol.Regarding test G (96% EtOH), an incomplete fat dissolution was observed for all the samples. Again, samples with higher levels of fat (canned oil and canned sauce) presented a lower rate of fat removal (25%) when compared to fresh high-fat fish samples . For these last samples, and in opposition to the previous tests with surfactants, the fat dissolution with 96% EtOH allowed to subsequently filtrate the samples. However, since fat removal was incomplete, the filters easily clogged, making the filtration a very slow and time-consuming process. Test H achieved the best results, presenting a complete fat removal (100%) for all the studied samples. Manually, and with the help of a steel spoon, fat (frequently occurring in the surface of the digested solution) was collected and transferred to a clean Petri dish, and immediately observed under a stereomicroscope for the presence of MPs. So, the protocol chosen for the fat post-digestion treatment was the H: manual recovery of the remaining fat, with immediate observation under a stereomicroscope.2O2, at 65 °C for 48 h. After digestion, solutions containing the plastic polymers were vacuum filtered using cellulose nitrate filter membranes (pore size 0.45 µM). After 48 h of drying at room temperature, filters were weighed in order to have the final mass and recovery rate of each polymer. Filters were observed under a stereomicroscope to conclude about the polymers’ morphological characteristics after the digestion incubation  to a maximum of 98.2% (for PE-LD), with an average recovery rate for all the polymers of 96.6%, confirming the efficiency of the proposed methodology for the recovering of MPs from seafood samples. At the end of the protocol, only PE-LD polymers (recovery rate of 98.2%) presented differences from their original characteristics, specifically color, which changed from blue to white. Tests with AC showed a recovery rate above 100% (recovery rate of 102%) but, since the initial and final mass values are very similar, it can be explained as the result of an incomplete drying of the filter before the final weighing.The present work allowed for the optimization of an analytical protocol for the extraction of MPs from seafood samples with different levels of fat, with the following considerations: Pre-treatment of seafood samples in a laboratory oven at 40 °C overnight;2O2 (with a volume capable of covering the entire sample), incubated in a laboratory oven at 65 °C, during 24 to 48 h (the incubation time may vary according to the characteristics of the sample);Sample digestion with 30% HFat post-digestion treatment with manual recovery of the remaining fat, with immediate observation under a stereomicroscope;Vacuum filtration of the digested sample (without fat) through cellulose nitrate filter membranes. After performing all protocol steps, a Fourier Transform Infrared Spectroscopy (FTIR) analysis, or an equivalent technique, is necessary to identify the polymers of the collected MPs.The optimized protocol showed high recovery rates and was also efficient in guarantying the integrity of MPs for the majority of plastic polymers tested. Hence, this protocol is suitable to retrieve MPs properly and efficiently from seafood samples with distinct levels of fat, including fresh and canned seafood. The methodology was already successfully applied in several seafood samples , allowing the observation and extraction of MPs for all the sampled species .


The latex used conventionally for oil-well cementing can lead to serious foaming issues in the cement slurry, which not only affects the accurate measurement of the density of the latex-containing cement slurry, but also is detrimental to cementing construction. A large amount of a foam stabilizer used for latex preparation is mainly responsible for foaming of the latex-containing cement slurry. In this study, soap-free emulsion polymerization was conducted using 2-acrylamido-2-methylpropanesulfonic acid (AMPS), styrene (St), and butyl acrylate (BA) as the reaction monomers and the effects of the AMPS dosage, monomer ratio, reaction temperature and stirring speed on the performance of the latex were investigated. The optimum synthesis conditions included a 30% monomer concentration, an St : BA : AMPS monomer ratio of 5 : 4 : 6, a synthesis temperature of 85°C, a stirring speed of 400 r.p.m. and 1.5% of the initiator. As-prepared latex exhibited good filtration loss control, excellent freeze–thaw stability, and extremely low foaming of the cement slurry with the added latex, which was extremely beneficial for on-site cementing construction. The cAs an important cement slurry additive, latex can effectively alleviate or avoid the issue of gas channelling during the injection of the cement slurry, improve the elastic toughness of the cement stone and prevent the stress failure of the cement sheath during the service process –9. LatexAlthough traditional latex can effectively improve various properties of the cement slurry and cement stone, it exhibits a clear disadvantage: a large number of bubbles are produced in the cement slurry, which are difficult to eliminate effectively . A largeThe presence of a stabilizer in latex primarily leads to foaming of the latex cement slurry, and the absence of a stabilizer during latex preparation is the main measure to solving the foaming issue of the latex cement slurry. Therefore, in this study, latex is prepared by soap-free emulsion polymerization with no stabilizer introduced, and butyl acrylate (BA), styrene (St) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) are used as the monomers. The stability of latex and the effect of latex on the fluid loss of the cement slurry are used as the key performance indices. In addition, the latex is characterized by infrared (IR) spectroscopy and transmission electron microscopy (TEM).. 2. 2.1St, BA, sodium hydroxide, potassium persulfate and sodium bisulfite were purchased from Sinopharm Chemical Reagent Co., Ltd. AMPS was purchased from Jiangxi Changjiu Agricultural Chemical Co., Ltd. Class G oil well cement was purchased from Sichuan Jiahua Cement Co., Ltd. The dispersant SGJZ was supplied by Shengli Oilfield.. 2.2A certain amount of AMPS was completely dissolved in deionized water, and the pH of the system was adjusted with NaOH to 5–7. Then, the AMPS solution was transferred to a four-necked flask, and the stirrer and heating switch were switched on. Next, the temperature was increased to 85°C, followed by the addition of St and BA into the solution. After 30 min of continuous stirring, an initiator with 1.5% the mass of the monomer was added (mass ratio of potassium persulfate to sodium bisulfite was 1 : 1). The latex BA-St-AMPS (BSA) was obtained after 2 h of the reaction.. 2.3First, latex and deionized water were evenly mixed at a mass ratio of 1 : 50, and the mixed liquid was absorbed using a rubber dropper into the sample tube, and the top cover of the sample tube was covered. The particle size was analysed by using a Brookhaven Zeta Potential and Laser Particle Size Analyzer 90Plus Zeta instrument. Each sample was tested in triplicate, and the average value was taken as the particle size of the sample.. 2.4−1 by using a USA Thermo Fisher Nicolet IS50 Fourier transform IR spectrometer.First, a certain amount of latex BSA was weighed and added into a test tube, followed by the addition of an appropriate amount of anhydrous ethanol and shaking to break the formed emulsion. Second, a certain amount of acetone was added into the solution after breaking the emulsion, followed by high-speed centrifugation and pouring of the supernatant in the test tube. Next, the above steps were repeated thrice, followed by the replacement of acetone with distilled water and repetition of the above steps thrice to completely wash the unpolymerized monomers from the product. Finally, the finished material was placed in an oven for drying at low temperatures. After there was no change in the sample quality, it was removed from the oven and ground into a powder using an agate mortar. Absorption spectra were recorded in the range of 4000–400 cm. 2.5In this experiment, the microscopic morphology of the sample was directly observed on a JEM-2100F field-emission TEM instrument.. 2.6The cement slurry was prepared using a Waring blender according to the American Petroleum Institute (API) standards . First, . 2.7The freeze–thaw stability of latex refers to the stability of the latex system when subjected to alternating freeze–thaw cycles . The fre. 3. 3.1Herein, AMPS was used instead of traditional latex stabilizers; thus, its dosage is extremely critical to the performance of the latex. In this section, the ability of latex to control fluid loss and appearance of latex at 10%, 20%, 30%, 40% and 50% AMPS dosages were investigated. The products synthesized by the addition of 10% and 20% AMPS exhibited a large amount of white precipitates . It can . 3.2The latex performance was investigated by the addition of 40% AMPS and a monomer St to BA mass ratios of 0 : 1, 1 : 5, 2 : 5, 1 : 2, 4 : 5, 1 : 1, 5 : 4, 2 : 1, 5 : 2, 5 : 1 and 1 : 0. −1. With the increase in the amount of the hard monomer St, the ability of latex to control fluid loss gradually increased, it reached the optimum value at an St to BA mass ratio of 5 : 4, and the fluid loss was only 18.98 ml. With the further increase in the amount of the hard monomer St, the fluid loss of the cement slurry increased gradually. The results revealed that with the addition of a high amount of soft monomer BA, the latex particles were soft, and it was difficult for the particles to bear the sealing pressure; hence, the ability to control fluid loss is poor. With the gradual increase in the amount of the hard monomer St, the content of benzene rings in the molecular structure of the product increased gradually. The presence of benzene rings resulted in the difficult internal rotation of the polymer molecular chain, considerably improving the stiffness of the molecular chain and rendering the ability to withstand a certain pressure; hence, the fluid loss of the cement slurry is well controlled. With the further increase in the addition of the hard monomer St, the latex particles became extremely inflexible, and deformation was difficult during extrusion, making the effective sealing of cement particle pores difficult.At St to BA mass ratios of 0 : 1, 5 : 1 and 1 : 0, the prepared latex solutions were unstable, with the generation of a certain precipitate, and the latex exhibited better stability under the conditions of the other monomer ratios . Figure . 3.3In this section, the effect of the synthesis temperature on the properties of latex was investigated. As can be observed in . 3.4Stirring speed typically exerts a large effect on the particle size and stability of latex . In thisUnder stirring speeds of 200 and 300 r.p.m., a small amount of white precipitate was observed in latex, indicative of poor settling stability . At a ro. 3.5−1, and the stretching vibration absorption peak of -CH in copolymer alkyl was observed at 2928.37 cm−1. The absorption peak of C=O in BA was observed at 1727.42 cm−1, and the stretching vibration absorption peaks of the benzene ring C=C in styrene were observed at 1544.22 and 1496.00 cm−1. The stretching vibration absorption peak of C-O in BA was observed at 1185.04 cm−1, and the stretching vibration peak of S=O in AMPS was observed at 1400–800 cm−1. The stretching absorption peak of S-O in the copolymer AMPS was observed at 700.03 cm−1. Hence, latex is composed of St, BA and AMPS. At the same time, as the absorption peak corresponding to the C=C stretching vibration was in the range of 1675–1640 cm−1, no absorption peak was observed in this range, indicating that a compound containing C=C is absent and that all three monomers react to produce latex.. 3.6The structure and properties of the sample were observed by TEM analysis. . 3.7a). This result revealed that latex exhibits a good freeze–thaw stability, and it is convenient for transportation, storage, and use at sub-zero temperatures. The contrast sample of styrene–butadiene latex exhibited clear gelation after one freeze–thaw cycle, and it changed into a white solid substance (b) and was crushed easily (c), indicative of the poor freeze–thaw stability of styrene–butadiene latex.The freeze–thaw stability of latex refers to the stability of latex during alternating freezing and thawing processes, which is a key index to measure the storage and transportation capacity of latex in winter. The experimental results revealed that the prepared latex BSA could still recover after seven freeze–thaw cycles without precipitation a. This rubstance b and wasd easily c, indica. 3.8For a conventional cement slurry, it is generally desirable to have as few air bubbles as possible in the prepared slurry to accurately measure the density of the slurry. The addition of cement admixtures often results in the formation of air bubbles in the cement slurry, seriously interfering with the accurate measurement of the cement slurry density. In this section, the effect of the commonly used styrene–butadiene latex in the field was compared and evaluated with the latex prepared herein on the amount of air bubbles produced during the preparation of the cement paste . As can . 4(1)The stability of latex was significantly affected by AMPS addition, with good stability at an AMPS content of greater than 30%. With the increase in the addition amount of AMPS, the fluid loss of the cement slurry decreased and then increased. The analysis suggested that this result may be attributed to the effect of the AMPS addition on the particle size of the latex, resulting in a change in the fluid loss of the cement slurry.(2)With the increase in the mass ratio of St : BA, the fluid loss of the cement slurry first decreased and then increased. This result indicated that a reasonable ratio of hard and soft monomers helps to ensure that the latex exhibits an ability to control fluid loss.(3)With the increase in the synthesis temperature, the fluid loss of the cement slurry decreased first and then increased. The synthesis temperature also mainly affected the particle size of latex as well as the fluid loss of the cement slurry.(4)With the increase in the mixing speed, the fluid loss of the cement slurry increased first and then decreased, and the fluid loss of cement slurry was the lowest at a mixing speed of 400 r.p.m.(5)BSA latex exhibited good stability after seven freeze–thaw cycles between −20°C and 20°C. In addition, BSA latex did not cause foaming issues in the prepared latex cement slurry.To prevent considerable foaming of the latex cement slurry, soap-free emulsion polymerization was employed to prepare latex, which did not require a stabilizer to achieve good stability of the latex. Based on the experimental results, the following conclusions can be drawn: