High entropy alloys (HEAs) with a face-centered cubic (fcc) structure are considered as promising structural materials, in particular due to their impressive ductility and toughness at cryogenic ...temperature; at the same time strength of these HEAs is often quite low. An addition of interstitial elements like carbon substantially increases the strength of the fcc HEAs at room temperature, however the effect of C on cryogenic properties has not been properly studied. Therefore in this work we examined cryogenic tensile behavior of the fcc high entropy alloys with different carbon content (0–2 at.%). The alloys had non-equiatomic proportions of principal elements, i.e. Co1Cr0.25Fe1Mn1Ni1. The lower Cr concentration in comparison with the equiatomic alloy led to the higher solubility of carbon confirmed by both ThermoCalc calculations and experimental results; only in the alloy with 2 at.% C a small (<1%) fraction of Cr-rich M7C3 carbides was found in the as-cast condition. The microstructure of the alloys was not significantly affected by the carbon content and generally consisted of coarse (250–300 μm) fcc phase grains with dendritic segregations. In turn, the carbon content influenced on mechanical behavior substantially: the strength of the alloys progressively increased with the carbon content along with some reduction in ductility. Solid solution strengthening by carbon at 77 K was much stronger than that at room temperature: 67 MPa/at% and 178 MPa/at%, respectively. The increase in solid solution strengthening agreed well with an anticipated increase in lattice friction at lower temperatures. Plastic deformation was associated with dislocations slip both at 293 K and 77 K; a decrease in temperature and an increase in the carbon concentration increased the inclination to planar slip. The obtained results offer new approaches to increase the cryogenic properties of fcc HEAs.
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•Co1Cr0.25Fe1Mn1Ni1 high entropy alloys with 0–2 at.% C produced by induction melting.•High solubility of C in the fcc matrix of the alloys due to reduced Cr concentration.•Addition of C and lower deformation temperature pronouncedly increased strength.•Solid solution strengthening was 67 MPa/at% C at 293 K and 178 MPa/at% C at 77 K.•Dislocations slip mediated plastic deformation both at 293 K and 77 K.
Effect of annealing of a cold-worked CoCrFeMnNi alloy at temperatures of 500–900 °C for 1–50 h on the structure and mechanical properties was studied in the present work. Annealing for an hour ...resulted in: i) recrystallization of the face-centered cubic (fcc) matrix at 600–900 °C; ii) precipitation of a Cr-rich body-centered cubic (bcc) phase at 500–700 °C or a sigma phase particles at 600–800 °C. Moreover, an increase in the annealing time to 50 h at 600 °C resulted in a continuous growth of both the fcc grans and bcc/sigma particles and in an increase in the fraction of the sigma phase at the expense of the bcc phase particles. The fcc grains growth was found to be controlled by the pinning effect of the second phase particles. Soaking for an hour at 500–600 °C resulted in a substantial increase in strength of the alloy due to the second phases precipitation. Meanwhile annealing at the higher temperatures as well as an increase in the annealing time at 600 °C resulted in softening; however, even after 50 h annealing, the alloy demonstrated reasonably high strength. In the latter case fine fcc grains, preserved due to the pinning effect by the second phases particles, contributed to strength mainly.
The effect of cold rolling to 80% thickness reduction and annealing at 973–1373 K for 1 h on the microstructure and mechanical properties of a C-containing CoCrFeNiMn high-entropy alloy was studied. ...Cold rolling significantly strengthened the alloy to the yield strength of 1310 MPa. Annealing at 973 K or 1073 K resulted in incomplete recrystallization of an fcc matrix and M23C6-type carbide precipitations aligned with highly elongated grains/subgrains. Complete recrystallization occurred during annealing at 1173 − 1373 K. The ordered arrangement of the carbides was not observed after annealing at 1273 K or 1373 K. The volume fraction of carbides decreased with increasing the annealing temperature that can be reasonably described by a Thermo-Calc prediction. The coarsening behavior of the microstructure constituents was studied during isothermal annealing at 1173 K for 1–50 h. It was found that the grain growth and the particle coarsening can be expressed by power law functions of annealing time with grain/particle size exponents of about 2 and 3, respectively. An increase in the annealing temperature from 973 K to 1373 K led to a gradual softening of the alloy; the yield strength decreased from 870 MPa to 320 MPa, whereas total elongation increased from 24% to 47%, respectively. Contributions of various strengthening mechanisms into the overall strength of the alloy were discussed.
The influence of anthropogenic pollution, particularly with polycyclic aromatic hydrocarbons (PAHs) on soil toxicity and spread of antibiotic resistance genes (ARGs) is extremely important nowadays. ...We studied 20 soil samples from a technogenically polluted site, municipal solid wastes (MSW) landfills, and rural settlements in the southwestern part of the Rostov Region of Russia. A close correlation was established between the results of biosensor testing for integral toxicity, the content of genes for the biodegradation of hydrocarbons, and the concentration of PAHs in soils. The relation between the quantitative content of ARGs and the qualitative and quantitative composition of PAHs has not been registered. Soils subjected to different types of the anthropogenic pressure differed in PAHs composition. The technogenic soils are the most polluted ones. These soils are enriched with 5 ring PAHs and carry the maximum variety of assayed ARGs, despite the fact that they do not receive household or medical waste.
•At biotesting soils contaminated with industrial PAHs are more toxic than landfills.•Technogenically polluted soils are enriched with 5 ringPAHs compared to landfills.•Technogenically polluted soils contain more diverse ARGs.
•The high content of pollutants negatively affects bacterial biodiversity.•The structure of soil microbiome depends on the pollutant type.•Pollutants have diverse effects on different bacterial taxa.
...Metagenomic studies of soil microbocenoses are extremely relevant nowadays. The study of pollution impact on soil microbiomes is of particular interest. The structure of microbial communities in soils with different levels of pollution by polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) was studied. High bacterial biodiversity was found in all the studied soil samples, but its lowest values are found in soil samples taken on the territory of technogenically polluted Lake Atamanskoye. Assessment of soil pollution showed the highest content of polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) for the soils Lake Atamanskoye. The high content of pollutants negatively affects the abundance of representatives of the phyla Actinobacteria, Planctomycetes, Verrucomicrobia, and Nitrospirae. Such phyla as Proteobacteria, Candidate Divisions TM7, OD1, WPS-2, Chlamydiae, Cyanobacteria are characterized by positive direct correlation with the content of pollutants, especially with PAHs. A cooperative effect of decrease in the number of Actinobacteria and Proteobacteria with an increase in Armatimonadetes probably corresponds to PTEs contamination. The proportion of Candidate Division OD1, Chlamydiae, Cyanobacteria, and Candidate Division WPS-2 was increased in the soil microbiome under the influence of severe combined pollution. Pollutants negatively affect the abundance of dominant unclassified_o__Gaiellales and unclassified_o__WD2101 genera. Iamia, Salinibacterium, Arthrobacter, Kaistobacter, Thiobacillus genera are characterized by a low abundance, but they are presumably the most resistant to soil pollution. It was revealed that the level of soil pollution largely determines the composition and diversity of bacterial communities in the soils of the studied territories. Operating taxonomic units have been established that have prognostic value for assessing the state, level of soil pollution, and their biological safety.
The task of estimating the greenhouse gas fluxes in the atmosphere from satellite data is relevant. This problem is solved based on a data assimilation system using a model of transport and diffusion ...of an impurity in the atmosphere. The paper discusses an approach to solving the problem of estimating the greenhouse gas fluxes based on the use of the ensemble Kalman filter for the global model of transport and diffusion. The paper proposes a numerical algorithm based on the decomposition of the model domain. The originality of this work is the application of the local ensemble Kalman filter algorithm. The case of this study when the greenhouse gas fluxes are considered as a variable is discussed. Here are the results of the simulated numerical experiments on the implementation of the step of analyzing the data assimilation algorithm in the case of the global model of transfer and diffusion.
The possibility of synthesizing glass-ceramic geopolymer materials based on ash and slag waste generated during the combustion of coal fuel at power plants is considered. Compositions of charge have ...been developed, and synthesis of geopolymeric materials has been carried out. The density and uniformity of the porous structure of the obtained samples were analyzed, the substances—pore-forming agents—that have the highest foaming activity were selected, and the optimal amount of an alkaline activator for the synthesis of geopolymers was selected. The phase composition of the obtained samples was studied.
This article deals with the issues of identifying and studying high-amplitude, low-frequency oscillations in the electrical regime parameters (LFO ERP) of an electric power system. These problems are ...currently important for ensuring operating stability of the generation equipment and maintaining dynamic stability of the power system. Solving the problems of identifying LFO ERP, determining the source of the oscillations, monitoring the oscillatory stability of the power system, and effective damping of the LFO, is a necessary condition for the operational reliability of a power system. In modern power systems a wide variety of possible sources of LFO are observed, such as: periodically varying load, e.g., stops and starts of pumps in the oil and gas industry or motors for machines operating over a wide range of speeds with frequent starts and stops; disconnection of the load (of individual electrical transmission lines), that cause disruption of permissible power flows at any point of the power system, which leads to dynamic oscillatory instability; incorrect adjustment of the automatic voltage regulator (AVR) and/or channels for stabilization of the automatic excitation regulator (AER) of the generator under consideration or associated with it; periodic variation in the torque on a generator shaft. The use of devices for synchronized vector measurements (DSVM) makes it possible to determine with high accuracy the sources of the LFO in a power system, regardless of their nature and, depending on the number of installed measurement devices in the power system, these can be specified for the final primary equipment.
Differential diagnosis of bacterial and viral meningitis is an urgent problem of the modern clinical medicine. Early and accurate detection of meningitis etiology largely determines the strategy of ...its treatment and significantly increases the likelihood of a favorable outcome for the patient. In the present work, we analyzed the peptidome and cytokine profiles of cerebrospinal fluid (CSF) of 17 patients with meningitis of bacterial and viral etiology and of 20 neurologically healthy controls. In addition to the identified peptides (potential biomarkers), we found significant differences in the cytokine status of the CSF of the patients. We found that cut-off of 100 pg/ml of IL-1β, TNF, and GM-CSF levels discriminates bacterial and viral meningitis with 100% specificity and selectivity. We demonstrated for the first time the reduction in the level of two cytokines, IL-13 and GM-CSF, in the CSF of patients with viral meningitis in comparison with the controls. The decrease in GM-CSF level in the CSF of patients with viral meningitis can be explained by a disproportionate increase in the levels of cytokines IL-10, IFN-γ, and IL-4, which inhibit the GM-CSF expression, whereas IL-1, IL-6, and TNF activate it. These observations suggest an additional approach for differential diagnosis of bacterial and viral meningitis based on the normalized ratio IL-10/IL-1β and IL-10/TNF > 1, as well as on the ratio IFN-γ/IL-1β and IFN-γ/ TNF < 0.1. Our findings extend the panel of promising clinical and diagnostic biomarkers of viral and bacterial meningitis and reveal opposite changes in the cytokine expression in meningitis due to compensatory action of proand antiinflammatory factors.
Preparation of Extrapure Cesium Iodide Mastryukov, M. V.; Brekhovskikh, M. N.; Klimova, V. M. ...
Inorganic materials,
10/2020, Letnik:
56, Številka:
10
Journal Article
Recenzirano
This paper presents results of a physicochemical study of the preparation of extrapure-grade (99.998%-pure) cesium iodide from a technically pure product obtained by reacting cesium carbonate and ...hydriodic acid. The synthesized CsI was purified in two steps, involving vacuum drying and high-temperature distillation. We calculated kinetic constants of vacuum drying and evaluated water content as a function of temperature. The final step in removing regulated impurities from CsI was high-temperature distillation. Metallic impurities in the samples thus prepared were determined using inductively coupled plasma mass spectrometry and X-ray diffraction. The results are presented for the first time.
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