Molecular dynamics study of the stability of aluminium coatings on iron

Among the available protection systems for steel, the use of coatings is the most popular and economical method. One can protect the steel electrode from aggressive media with an aluminum coating. A thin Al film on an Fe substrate has been studied by the molecular dynamics method at a heating temperature from 300 K to 1500 K. A significant horizontal displacement of individual Al atoms on the edges of the film is observed during the simulation. The film begins to “spread” slightly near the edges. This “spreading” creates the conditions for the beginning of diffusion of iron atoms into aluminum. Some Al atoms were found to penetrate the Fe matrix at a temperature of 873 K. The total energy curve of the system shows both the melting transition in aluminum and phase transition from the body-centered cubic lattice to the face-centered cubic one at 1173 K. The binding energy for the Al atom in the lattice of the Fe crystal is smaller than that for Fe atoms. The calculated diffusion coefficients for Al and Fe have a significantly slower growth with a temperature in the range of 673 K ≤ T ≤1500 K. To describe the diffusion in a crystal using the molecular dynamics model, a temperature-dependent correction to the activation energy is calculated. The temperature dependence of the diffusion coefficient of aluminum atoms in an iron crystal can be represented as an Arrhenius expression with a temperature-dependent energy barrier for diffusion. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved

Physical aspects of the lithium ion interaction with the imperfect silicene located on a silver substrate

Epitaxy of Si on a silver substrate is the main method to obtain silicene. The latter does not separate from the substrate. In the present paper, the possibility of using silicene on a silver substrate as an anode for lithium-ion batteries is studied by the method of molecular dynamics. Structural and mechanical effects arising from the motion of a Li + ion through a planar channel formed by a perfect and defective two-layer silicene are studied. Generally, the defect stability and silicene sheet integrity are independent of the Ag(001) or Ag(111) substrate type. The transverse vibrations of Si atoms in the channel have a significant effect on the motion of lithium ions. This effect is taken into account by using the interference factor that describes the slowing down of the motion of the Li + ion in the channel. The dependence of this coefficient on the size of vacancy defects in silicene is determined. The presence of the substrate makes this dependence less relevant. The stress distribution in the defective silicene while driving a lithium ion along the planar silicene channel is calculated. The strongest stresses in the silicene are created by forces directed perpendicular to the strength of the external electric field. These forces dominate in the silicene channel placed on the substrates of both types. © 2018, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Acknowledgements. This study is supported by the Russian Science Foundation (project no. 16‑13‑00061)

Computer modeling of electrochemical processing of waste nuclear fuel

The purpose of the work is to study the influence of the electrodes geometry and the mutual arrangement of functional elements in the working space of a metallization electrolyzer on the distribution of the oxygen flux density in the electrolyte, as well as on the distribution of electric and temperature fields. In a computer model, the stationary operation mode of the electrolyzer for processing spent nuclear fuel immersed into the LiCl molten salt with the addition of Li2O was studied. The calculations were performed using the ANSYS software package. We studied eight designs of the electrolyzer, which differ in the immersion depth of the anodes into the melt as well in the types anode protective covers and the cathode baskets. Verification based on the comparison of the computer modeling with experimental data indicates the adequacy of the models used. The electrolyte velocity field and the temperature field are calculated, as well as the steady-state picture of the distribution of electric current density over the working space of the electrolyzer. The efficiency of the electrochemical cell is determined. © 2020 John Wiley & Sons LtdState Atomic Energy Corporation ROSATOM, ROSATOM, (17706413348200000540)Funding text 1: The present paper is partly supported by the agreement No. 18, 04.06.2018 under support of the State Atomic Energy Corporation ROSATOM. The work was carried out as a part of R&D “Development of technology and equipment for the pyrochemical processing of SNF of fast neutron reactors” in the “Breakthrough” project area.Funding text 2: The present paper is financially supported by the State Atomic Energy Corporation Rosatom (State contract No H.4o.241.19.20.1048 dated 17.04.2020, identifier 17706413348200000540)

Kinetic test of a doped silicene-graphite anode element in a computer experiment

The stability of the system "bi-layer silicene on the graphite substrate" is studied in the molecular dynamics simulation. Silicene sheets are doped with phosphorus, and graphite sheets are doped with nitrogen. Lithium ion moves along a silicene channel with a gap in the range of 0.6-0.8 nm. The time for the ion to pass the channel and leave it decreases with an increase in the channel gap. There is a tendency of the silicene sheets roughness growth with an increase in the gap between silicene sheets (except, 0.75 nm). Doping phosphorus and nitrogen atoms stabilize the silicene and graphite structure. © 2020 Published under licence by IOP Publishing Ltd.Russian Science Foundation, RSF: 16-13-00061The study is supported by the Russian Science Foundation (project no. 16-13-00061)

Modeling the UO2 reduction process

Methods of molecular dynamics and DFT calculations have been used to study the reduction mechanisms of UO2 as the most representative part of spent nuclear fuel to metallic uranium. It is shown that the critical softening of the combined modulus of elasticity C11-C12 to zero is the reason for the destruction of the UO2 crystal as a result of the removal of oxygen from it. This destruction is accompanied by an order-disorder phase transition in the oxygen subsystem of the crystal under consideration. DFT calculations indicate a continuous decrease in the band gap as oxygen is removed from the UO2 crystal. When the system reaches the composition U2O3, the band gap disappears and the system becomes electrically conductive. The appearance of the dielectric-conductor transition explains the realization of the FFC Cambridge process during the recovery of spent nuclear fuel. The passage of Li+ and Cl– ions of the LiCl melt through cylindrical channels in a UO2 crystal with cross-sectional radii from 0.25 up to 2 nm has been studied. The strength of the external electric field required for the passage of these channels decreases with an increase in the channel cross section, and the number of Cl– ions entering the channel increases. On the walls of the channels that pass ions with charges of both signs, colonies of adsorbed Cl– and Li+ atoms appear separated from each other, between which strong electric fields are formed. The existence of such fields can cause Li+ ions to move deep into the material being reduced.https://doi.org/10.15826/elmattech.2023.2.01

Towards the stability of low-temperature aluminum electrolysis

The results of several different tests related to the low-temperature aluminum electrolysis were considered in this work. The role of mass transfer processes in the anode-cathode space was recommended to be significant during electrolysis in the low-temperature KF-AlF3 and NaF-AlF3-based melts. The stationary polarization and voltammetry methods were applied in order to study the kinetics of the electrode processes on the carbon and metal electrodes in the KF-AlF3-Al2O3 melts and to select the electrolysis parameters. The schemes of electrode processes were suggested on the basis of electrochemical tests, the flows of substances in the anode-cathode distance were analyzed and the main reasons of the cathode current efficiency decrease during the low-temperature electrolysis in the KF-AlF3-Al2O3 and KF-NaF-AlF3-Al2O3 melts were discussed. It was revealed that the cathode current density should not exceed 0.4-0.55 A cm-2 during the electrolysis at 750 °C-800 °C. © 2021 The Author(s).U.S. Department of Energy, USDOENational Renewable Energy Laboratory, NRELMinistry of Education and Science of the Russian Federation, Minobrnauka, (FEUZ-2022-0031)Funding text 1: The research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) is gratefully acknowledged. The youth laboratory with Grant number: FEUZ-2022-0031.Funding text 2: The modelling of the CSP was performed using SAM version 2020.2.29, provided by the National Renewable Energy Laboratory (NREL), funded by the Department of Energy. SAM is commonly used by researchers for techno-assessment analysis worldwide. The SAM model also includes the simulation of the parabolic trough, power tower, and linear Fresnel for electric power generation []. In this present investigation, a solar tower power plant is modeled in India. The flow diagram of the simulation in the SAM software is presented in

Исследование эффективности автоматической системы обнаружения и распознавания объектов на радиолокационном изображении с применением нейронных сетей

The main factors influencing the efficiency of an automatic object recognition system in a radar image obtained with a synthetic aperture radar are considered A clustering algorithm of selecting objects on a radar image has been developed. The results of applying the radar image clustering algorithm, which makes it possible to increase the probability of correct recognition of objects, are presented. An analysis of the effectiveness of the application of the clustering algorithm depending on the threshold detection is given. The structure of the two-stage system of the algorithm of the automatic recognition of objects on a radar image has been developed and presented.  Weber V. I., Kuprits V. Y., Zaikov K. D. Research of the efficiency of the automatic system of detection and recognition of objects on radar image using neural networks. Ural Radio Engineering Journal. 2022;6(3):225–309. (In Russ.) DOI: 10.15826/urej.2022.6.3.004. Рассмотрены основные факторы, влияющие на эффективность автоматической системы распознавания объектов на радиолокационном изображении, полученном с помощью радиолокатора с синтезированной апертурой антенны. Разработан алгоритм кластеризации для выделения объектов на радиолокационном изображении. Приведены результаты применения алгоритма кластеризации радиолокационного изображения, позволяющего повысить вероятность правильного распознавания объектов. Приведен анализ эффективности применения алгоритма кластеризации в зависимости от порогового обнаружения. Разработана и приведена структура двухэтапной системы алгоритма автоматического распознавания объектов на радиолокационном изображении.  Вебер В. И., Куприц В. Ю., Зайков К. Д. Исследование эффективности автоматической системы обнаружения и распознавания объектов на радиолокационном изображении с применением нейронных сетей. Ural Radio Engineering Journal. 2022;6(3):296–309. DOI: 10.15826/urej.2022.6.3.004.

Electrodeposition of Silicon from the Low-Melting LiCl-KCl-CsCl-K2SiF6Electrolytes

The possibility of silicon electrodeposition from the low-melting LiCl-KCl-CsCl-K2SiF6 electrolytes has been studied. The stability of a silicon-containing additive was studied by cyclic voltammetry, and the rate constant of the chemical reaction of SiF4 release at a temperature of 827 K was calculated. It is determined that the constants of velocity values in the melt based on eutectic composition are 2 orders of magnitude higher, which indicates a higher rate of formation of volatile compounds. Cyclic voltammetry was also used to study the electrochemical behavior of K2SiF6 in the melts under study. It was found that the silicon electroreduction at the cathode is not reversible and proceeds in one 4-electron reaction. The diffusion coefficient calculated by the Matsuda-Ayabe equation was 0.72·10-5 cm2·s-1 at temperature of 823 K. According to the obtained voltammograms, the parameters for the silicon electrodeposition were selected. At a potential of -0.4 V vs QRE, dendritic silicon deposits were obtained. © 2022 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BYNC- ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: [email protected]. [DOI: 10.1149/1945-7111/ac5a1c]

Ab Initio Study of the Mechanism of Proton Migration in Perovskite LaScO3

The mechanism of proton motion in a LaScO3 perovskite crystal was studied by ab initio molecular dynamics. The calculations were performed at different temperatures, locations, and initial velocity of the proton. Different magnitudes and directions of the external electric field were also considered. It is shown that initial location and interaction between proton and its nearest environment are of great importance to the character of the proton movement, while the magnitude and direction of the initial velocity and electric field strength are secondary factors characterizing its movement through the LaScO3 crystal. Four types of proton-jumping between oxygen atoms are determined and the probability of each of them is established. Energy barriers and characteristic times of these jumps are determined. The probable distances from a proton to other types of atoms present in perovskite are calculated. It is shown that the temperature determines, to a greater extent, the nature of the motion of a proton in a perovskite crystal than the magnitude of the external electric field. The distortion of the crystal lattice and its polarization provoke the formation of a potential well, which determines the path for the proton to move and its mobility in the perovskite crystal. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.122020100205-5, FUME-2022-0005; Government Council on Grants, Russian Federation: 075-03-2022-011, FEUZ-2020-0037Funding: This work is partly supported by Government of Russian Federation, the State Assignment number FEUZ-2020-0037, registration number 075-03-2022-011; and is partly executed in the frame of the scientific theme of Institute of high-temperature electrochemistry UB RAS, number FUME-2022-0005, registration number 122020100205-5

DFT-based calculations of silicon complex structures in KF–KCl–K2SiF6 and KF–KCl–K2SiF6–SiO2 melts

The length and energy of bonds in the complex anions of silicon formed in KF−KCl−K2SiF6 and KF−KCl−K2SiF6–SiO2 melts were evaluated using the method of first-principles molecular dynamics, accomplished by means of the Siesta program. The effect of K+ (from the second coordination sphere) on the stability of these complexes was studied. The bond lengths in the silicon complexes was found to change with increasing amount of the potassium ions. It was established that the following complexes [SiO4]4-, [SiO3F]3- and [SiF6]2- are the most stable in KF−KCl−K2SiF6 and KF−KCl––K2SiF6–SiO2 melts. The [SiO4]4- and [SiF6]2- complexes are thermally stable in the molten salt in the temperature range of 923–1073 K, whereas the [SiF7]3-structure, which is typical for the lattice of crystalline K3SiF7, is unstable in this temperature range. In the KF−KCl−K2SiF6−SiO2 melts, conditions above 1043 K were created allowing the transformation of [SiО3F]3- into [SiO4]4-. Within the studied temperature mode, the Si–F bond length is in the range 1.5––1.9 Å and the Si–O bond lengths is 1.5–1.7 Å. The obtained results are in a good agreement with in situ data of Raman spectroscopy for the KF−KCl−K2SiF6 and KF–KCl–K2SiF6–SiO2 melts. © 2019 Serbian Chemical Society. All rights reserved.Russian Science Foundation, RSF: 18-73-00227The work was accomplished with the financial support of the Russian Science Foundation, Project No. 18-73-00227