Mechanisms of plastic deformation of CoCrFeNi high-entropy alloy single crystals during solid solution hardening by Mo atoms

The effect of alloying with Mo atoms 4 at % on the temperature dependence of critical resolved shear stresses (CRSS) τcr(T), strain hardening coefficient, plasticity and deformation mechanism was studied on [1¯11]-oriented crystals of the fcc CoCrFeNi (at %) high-entropy alloy (HEA) within the temperature range T = 77-973 K under tension. It was shown that during solid solution hardening by Mo atoms, the CRSS τcr increased by 45 and 23 MPa, respectively, at 77 and 296 K compared to crystals of this orientation of the equiatomic CoCrFeNiMn HEA. The onset of plastic deformation is associated with slip, and a planar structure with dislocation pile-ups was found at T = 77-296 K. At 77 K, with the development of twinning in one system simultaneously with slip, high values of Θ = dσ/dϵ = 1750 MPa and maximum stresses before failure σmax = 1650 MPa were found, and the plasticity was 57%. With an increase in the test temperature, deformation developed only by slip; Θ = dσ/dϵ, and σmax decreased, but the plasticity remained at the level of 50-57%

Critical resolved shear stress for twinning and twinning-induced plasticity in single crystals of the CoCrFeNiMo0.2 high-entropy alloy

The effect of alloying with Mo atoms 4 at.% on the twinning deformation, critical resolved shear stresses (CRSS) for slip τslcr and twinning τtwcr and plasticity was studied in [111]-, [144]- and [001]- oriented crystals of the Co24Cr24Fe24Ni24Mo4 (at.%) high-entropy alloy (HEA) under tension at 296 and 77 K. The stacking fault energy of the Co24Cr24Fe24Ni24Mo4 HEA, measured in the resent paper on the triple dislocation nodes, is equal to 0.027 J/m2. It is shown that initial yield behavior along studied orientations is governed by dislocation slip and the CRSS for slip are independent of crystal orientation. Under tensile strain, twinning develops in the [111]- and [144]- oriented crystals only at 77 K and is not detected in the [001]-oriented crystals. Two types of twins are found in the [111]- and [144]-oriented crystals (thin nanotwins and macrotwins). Nanotwins develop after a low slip deformation of 5–10% and are observed only by transmission electron microscopy. Macrotwins are detected after a significant slip deformation of 20 and 60% and are determined metallographically and X-ray by the precession of the crystal axis, respectively, in the [111]- and [144]-oriented crystals. In the [111]- oriented crystals, there is no precession of the crystal axis due to the development of slip simultaneously in several systems. It is shown that CRSS for nano- and macrotwins are dependent on the crystal orientation. In the [144]-oriented crystals, τtw cr = 212 MPa for nanotwinning and τtw cr = 400 MPa for macrotwinning. In the [111]-oriented crystals, τtw cr = 250 MPa for nanotwinning and τtw cr = 335 MPa for macrotwinning. For the transition to deformation by macrotwinning, it is necessary that the effective stacking fault energy γef is approaching to zero and the condition τtwcr <τslcr is satisfied. Deformation by macrotwinning suppresses slip multiplicity and shifts the formation of the neck formation according to the Consid`ere condition to higher stress levels. This increases plasticity from 72% at 296 K to 108% at 77 K in [144]-oriented crystals and from 48% at 296 K to 57% at 77 K in [111]-oriented crystals

Shape memory effect of [111]-oriented Cr20Mn20Fe20Co35Ni5 high-entropy alloy single crystals

Shape memory effect (SME) governed by the γ–ε martensitic transformation (MT) was studied in the [111]-oriented Cr20Mn20Fe20Co35Ni5 high-entropy alloy crystals under tension. The dependence of SME on the conditions of isothermal and isobaric deformation was established. It was shown that the maximum reversible strain of 7.4% and SME of 6.8% were observed under conditions of isothermal deformation

EVALUATION OF SEWAGE WITHIN MAKHACHKALA BY CHEMICAL PARAMETERS

Abstract. Theme. Assessment of the quality of wastewater within Makhachkala by chemical parameters.Location. Makhachkala, Dagestan, Russia.The aim of the study is to determine the chemical quality of sewage water polluting the Caspian Sea within the city of Makhachkala.Method. Object of study is the sample of wastewater sampled 10–11 January 2012 within the city of Makhachkala. Sampling of wastewater and chemical analysis was carried out in accordance with the International Organization for Standardization. Quality test samples evaluated in terms of water pollution index and coefficient calculation integrated pollution.Results. Using certified measurement techniques in 9 samples of wastewater identified 26 normalized parameters. Found that wastewater selected in two paragraphs refer to quality very dirty, 7 points extremely dirty; in all samples of wastewater content from 6 to 10 standardized components exceeds the MCL and the coefficient of the complex water pollution 7 samples belong to category II and contamination of sample 2 to Category III contamination.Main conclusion. The data obtained can be considered as the primary material for further chemical monitoring the quality of wastewater into the Caspian Sea within the administrative boundaries of the city of Makhachkala

ADDRESSING ENVIRONMENTAL CHALLENGES UNDER COMPREHENSIVE UTILIZATION OF GEOTHERMAL SALINE WATER RESOURCES IN THE NORTHERN DAGESTAN

Aim. The aim of the study is to develop technologies for processing geothermal brine produced with the extraction of oil as well as to solve environmental problems in the region.Methods. In order to determine the chemical composition and radioactivity of the geothermal water and solid samples, we used atomic absorption and gamma spectrometry. Evaluation of the effectiveness of the technology was made on the basis of experimental studies.Results. In the geothermal water, eight radionuclides were recognized and quantified with the activity of 87 ± 5 Bq / dm3. For the processing of this water to produce lithium carbonate and other components we propose a technological scheme, which provides a step of water purification from radio-nuclides. As a result of aeration and alkalinization, we can observe deactivation and purification of the geothermal water from mechanical impurities, iron ions, hydrogen carbonates and organic substances. Water treatment allows recovering lithium carbonate, magnesite caustic powder and salt from geothermal water. The mother liquors produced during manufacturing operations meet the requirements for the water suitable for waterflooding of oil reservoirs and can be injected for maintaining the reservoir pressure of the deposits.Conclusion. The implementation of the proposed processing technology of mineralized geothermal water produced with the extraction of oil in the Northern Dagestan will contribute to extend the life of the oil fields and improve the environmental problems. It will also allow import substitution in Russia for lithium carbonate and edible salt

Online training during a pandenic COVID19: evaluation of the practical application of remote technologies to students

2020 has become an important audit for the medical education system: theoretical and practical training of future doctors to move to the online format. This article will consider how students USMU are satisfied with the transfer of lecture and practical exercises in the remote format. The positive dynamics of students' satisfaction with the educational process in the period from the beginning of the pandemic (March 2020) on November 2020 was noted.2020 год стал важной проверкой для системы медицинского образования: теоретическую и практическую подготовку будущих врачей пришлой перенести в онлайн-формат. В данной статье будет рассмотрено, насколько студенты УГМУ удовлетворены переносом лекционных и практических занятий в дистанционный формат. Отмечена положительная динамика удовлетворенности студентов учебным процессом в период от начала пандемии (март 2020 года) по ноябрь 2020г

Creating and improving the image of a medical organization through the official website

This article describes the results of a sociological survey on the quality of filling and accessibility of information on the official websites of medical organizations. According to the results of the survey and according to the requirements of the order of the Ministry of Health of Russia dated December 30, 2014 No. 956n, criteria were selected and a quality audit of 25 sites of medical organizations in Yekaterinburg was conducted.В данной статье описаны результаты проведения социологического опроса о качестве наполнения и доступности информации наофициальных сайтах медицинских организаций. По результатам опроса и согласно требованиям приказа Минздрава России от 30.12.2014 №956н, отобраны критерии и проведен аудит качества 25-ти сайтов медицинских организаций г. Екатеринбурга

THE INFLUENCE OF CARBON NANOTUBES ON MORPHOLOGICAL AND ANALYTICAL CHARACTERISTICS OF CARBON SCREEN-PRINTED ELECTRODES

Multi-walled carbon nanotubes (CNT) are used as a modifier of carbon containing thick film electrodes for adsorptive stripping voltammetry. Morphological and analytical characteristics of electrodes with and without CNT were compared. It was found that the addition o f CNT increases the effective surface of the electrode and to facilitate the reduction of calomel. Electrodes with CNT have a twice higher sensitivity and 3 - 5 times ower limit of detection were shown

Global fine-resolution data on springtail abundance and community structure

Springtails (Collembola) inhabit soils from the Arctic to the Antarctic and comprise an estimated ~32% of all terrestrial arthropods on Earth. Here, we present a global, spatially-explicit database on springtail communities that includes 249,912 occurrences from 44,999 samples and 2,990 sites. These data are mainly raw sample-level records at the species level collected predominantly from private archives of the authors that were quality-controlled and taxonomically-standardised. Despite covering all continents, most of the sample-level data come from the European continent (82.5% of all samples) and represent four habitats: woodlands (57.4%), grasslands (14.0%), agrosystems (13.7%) and scrublands (9.0%). We included sampling by soil layers, and across seasons and years, representing temporal and spatial within-site variation in springtail communities. We also provided data use and sharing guidelines and R code to facilitate the use of the database by other researchers. This data paper describes a static version of the database at the publication date, but the database will be further expanded to include underrepresented regions and linked with trait data.</p