Изучение физико-химических и сорбционных свойств гексацианоферратов никеля и железа по отношению к цезию

The decontamination of liquid media contaminated by anthropogenic radionuclides provides a serious technological challenge. Sorption methods are often used to perform this task. The paper studies the physico-chemical and sorption characteristics of pure samples of iron (samples 1 and 2) and nickel (samples 3 and 4) hexacyanoferrates with respect to caesium radionuclides. It is shown that iron hexacyanoferrates have better granulometric composition than nickel hexacyanoferrates due to a smaller quantity of fine fraction (0.5-10 µm), thus providing for easier sedimentation and filtration. The results of thermal gravimetric and differential thermal analysis have shown that the lower limit of thermal stability of all hexacyanoferrates was at least 200°С. This means that spent sorbents can be dried at 100–150°С. Nickel hexacyanoferrates demonstrated a slightly higher thermal stability as compared with iron hexacyanoferrates. The experiment performed with simulated solutions demonstrated that pH does not affect the sorption of caesium by hexacyanoferrates with the рН range of 0.5 to 11.5. The distribution coefficients of caesium varied from 3·104 to 3·105 cm3/g. The effect of sodium and potassium on the sorption of cesium by iron and nickel hexacyanoferrates was studied at the concentrations of Na+ and K+ of up to 5 mol/dm3. The study demonstrates that the sorption of caesium by iron hexacyanoferrates does not depend on sodium and potassium concentration; whereas in case of nickel hexacyanoferrates distribution coefficients of caesium slightly decrease with concentrations of sodium and potassium of 1 mol/dm3and higher. However, distribution coefficients of caesium remained at least 104 cm3/g under any of the conditions studied. Ammonium ions showed significantly stronger suppressing effect on caesium sorption at the concentration of 0.5 mol/dm3, which can be explained by similar ionic radii of hydrated Cs+ and NH4+. Thus, the iron and nickel hexacyanoferrates can be recommended for caesium separation from a wide spectrum of acidic, neutral, slightly alkaline and salty intermediate-level liquid radioactive wastes. © 2021 MEDICC Review. All rights reserved

The Prospect of Using Centrifugal and Screw Compressors in the Systems of Centralized and Decentralized Compressed Air Supply of the Industrial Enterprises

Рассмотрены вопросы использования действующих центробежных и локальных винтовых компрессоров в системах централизованного и децентрализованного снабжения сжатым воздухом, а также состояние магистральных воздухопроводов на промышленных предприятияхDiscuss the use of the existing centrifugal and screw compressors in the systems of centralized and decentralized compressed air supply and the condition of the trunk air ducts in industr

Analysis of the Effect of Temperature on the Ultimate Strength of Refractory Materials

The energy efficiency of high-temperature batch aggregates largely depends on the modes of their heating and cooling. The modes of heating and cooling of aggregates in which thermal stress does not exceed the critical values of the ultimate strength of the refractories make it possible to increase their service life. The increase in the service life of refractories will lead to a reduction in the number of lining repairs and a decrease in the specific consumption of refractory materials per ton of technological product. Shorter warm-up and cool-down times result in lower energy consumption. Reducing the time for variable modes for casting ladles increases their turnover (the number of melt discharges into the ladle per day). Increasing ladle turnover not only reduces the number of ladles but also improves the economic performance of the enterprise. The ultimate strength of the refractory material significantly affects the rate of temperature change during heating and cooling of the refractory masonry. The purpose of this research is to study the dependence of the ultimate compression and tensile strengths of chamotte materials of the ShKU brand on temperature. The determination of the compression and tensile strengths was carried out on new samples of refractory materials as well as on samples of refractories that were in operation until the intermediate repair. To determine the ultimate compression strength of chamotte refractories, the standard technique for axial compression of the test specimen until its destruction was used. To determine the ultimate tensile strength, a three-point bending test was used with additional control of the surface temperature of the test sample during the test. The ultimate compression strength of chamotte refractories of the ShKU-32 brand increased for the new refractories by a maximum of 44%. For refractories that were in operation until the intermediate repair, the ultimate compression strength increased by a maximum of 56%. The value of the ultimate tensile strength at elevated temperatures turned out to be higher than the value at a temperature of 20 °C. For new refractories, the maximum ultimate tensile strength is 25% higher than the ultimate tensile strength under normal conditions. For refractories that were in operation until the intermediate repair, the maximum ultimate tensile strength increased by 24%. The obtained results can be used to increase the rate of heating or cooling of linings

Analysis of the Characteristics of Bio-Coal Briquettes from Agricultural and Coal Industry Waste

One of the options for reducing harmful emissions in the production of heat energy is the use of biomass, including in combination with industrial waste (for instance, coal and coke dust). Recent studies demonstrate that a mix of biomass and coal makes it possible to obtain a bio-coal briquette with better characteristics, which is a motivating factor in the search for alternative sources of heat energy from local agricultural waste. The aim of this research is to study the properties of bio-coal briquettes from biomass (sunflower husks and leaves) and industrial waste (coal and coke dust). The raw material was grinded and used for the production of bio-coal briquettes of 20%, 30%, 40%, 50%, 60%, and 70% of biomass. The biomass was grinded to the size of no more than 2 mm for the fine fraction and no more than 6 mm for the coarse fraction. The briquettes were made mechanically using a hydraulic press with a compression pressure of 25 MPa without the use of any binder. The characteristics of the investigated bio-coal briquettes, such as density, strength, moisture content, ash content, volatile yield, calorific value, ignition time, burning duration, and burning rate, have good enough values. The fine fraction briquettes compared to the coarse fraction briquettes have a longer burning time (about threefold longer) and a lower burning rate. For all briquettes, an increase in the composition of coal dust results in a rise in the burning time, whereas the burning rate falls. The best in terms of strength, calorific value and combustion parameters are the following briquettes: 70% sunflower husk and 30% coal dust from the Karazhyra deposit; 60% sunflower husk and 40% coal dust from the Shubarkul deposit; briquettes from 70% sunflower husk and 30% coke dust; briquettes from 80% leaves and 20% coal dust from the Karazhyra deposit; and briquettes from 70% leaves and 30% coal dust from the Shubarkul deposit. The selected briquettes are suitable as an alternative source of fuel

Defining of Mixing Volume of Three-Component Metal Alloys on Nickel Basis in Accordance with Mixing Volume of Two-Component Metal Alloys

Исследована зависимость молярного объёма, а также объёмов смешения трехкомпонентных металлических сплавов Ni-Cr-Mo от состава сплава. Доказана возможность определения этих величин через соответствующие молярные объёмы и объёмы смешения двухкомпонентных сплавов, входящих в данную систему.Molecular volume and mixing volume of three-component metal alloys dependence from alloy composition has been examined. The opportunity of defining these notions in accordance with molecular volumes and mixing volume of two-component metal alloys included in the system has been proved

Defining of Mixing Volume of Three-Component Metal Alloys on Nickel Basis in Accordance with Mixing Volume of Two-Component Metal Alloys

Исследована зависимость молярного объёма, а также объёмов смешения трехкомпонентных металлических сплавов Ni-Cr-Mo от состава сплава. Доказана возможность определения этих величин через соответствующие молярные объёмы и объёмы смешения двухкомпонентных сплавов, входящих в данную систему.Molecular volume and mixing volume of three-component metal alloys dependence from alloy composition has been examined. The opportunity of defining these notions in accordance with molecular volumes and mixing volume of two-component metal alloys included in the system has been proved

The Prospect of Using Centrifugal and Screw Compressors in the Systems of Centralized and Decentralized Compressed Air Supply of the Industrial Enterprises

Рассмотрены вопросы использования действующих центробежных и локальных винтовых компрессоров в системах централизованного и децентрализованного снабжения сжатым воздухом, а также состояние магистральных воздухопроводов на промышленных предприятияхDiscuss the use of the existing centrifugal and screw compressors in the systems of centralized and decentralized compressed air supply and the condition of the trunk air ducts in industr

Analysis of the Cooling Modes of the Lining of a Ferroalloy-Casting Ladle

An important element of the operation of high-temperature aggregates are modes that change over time. During these modes, maximum temperature changes are recorded in the cross-section of the lining of the aggregate. The difference in temperature leads to the formation of thermal stresses, which are the main reason for the repair of aggregates. During rapid heating, the inner layers of the lining are subjected to compressive stresses, while during rapid cooling, these layers experience tensile stresses. Under the same conditions, rapid cooling of the lining is more critical, since refractories have poor resistance to tension. The purpose of the study is to calculate and analyze the thermal stresses that arise during cooling of the casting ladle lining. The stresses are determined based on the calculation of the unsteady temperature field of the lining. Thermal stress values are necessary for analysis of the current cooling rates of casting ladles and subsequent development of optimal cooling modes for the lining. To solve the heat conductivity equation, a numerical method was chosen using an implicit four-point difference scheme. To study the cooling process of the casting ladle lining, temperature measurements were carried out in the zone of the greatest wear of the lining. Under conditions of natural convection, cooling of the casting ladle lining occurs unevenly. Cooling schedules during natural convection are characterized by significant unevenness and high rates of temperature decrease. The cooling rates of the inner surface of the lining at the initial stage of cooling significantly exceed the values recommended in the technical literature. Such cooling rates lead to the appearance of significant thermal stresses in the lining. For a refractory that has not been in service, the maximum thermal compressive stresses exceed the ultimate compressive strength by 1.27 times, and the tensile stresses exceed the corresponding limit values by 4.4 times. For refractories that have worked three fuses in the ladle lining, the maximum thermal compressive stresses exceed the ultimate compressive strength by 1.28 times, and the tensile stresses exceed the corresponding limit values by 3.19 times. The studied cooling modes for the casting ladle lining are unacceptable for operation. Cooling, taking into account the indicated rates, leads to the destruction of the lining material. To increase the resistance and duration of the working campaign of casting ladle linings, it is necessary to develop cooling modes for the lining at speeds at which the resulting thermal stresses do not exceed the strength of the refractory materials

Morphology, Structure, and Optical Properties of Semiconductor Films with GeSiSn Nanoislands and Strained Layers

Abstract The dependences of the two-dimensional to three-dimensional growth (2D-3D) critical transition thickness on the composition for GeSiSn films with a fixed Ge content and Sn content from 0 to 16% at the growth temperature of 150 °С have been obtained. The phase diagrams of the superstructure change during the epitaxial growth of Sn on Si and on Ge(100) have been built. Using the phase diagram data, it becomes possible to identify the Sn cover on the Si surface and to control the Sn segregation on the superstructure observed on the reflection high-energy electron diffraction (RHEED) pattern. The multilayer structures with the GeSiSn pseudomorphic layers and island array of a density up to 1.8 × 1012 cm−2 have been grown with the considering of the Sn segregation suppression by the decrease of GeSiSn and Si growth temperature. The double-domain (10 × 1) superstructure related to the presence of Sn on the surface was first observed in the multilayer periodic structures during Si growth on the GeSiSn layer. The periodical GeSiSn/Si structures demonstrated the photoluminescence in the range of 0.6–0.85 eV corresponding to the wavelength range of 1.45–2 μm. The calculation of the band diagram for the structure with the pseudomorphic Ge0.315Si0.65Sn0.035 layers allows assuming that photoluminescence peaks correspond to the interband transitions between the X valley in Si or the Δ4-valley in GeSiSn and the subband of heavy holes in the GeSiSn layer