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Rearrangement of cluster structure during fission processes

Results of molecular dynamics simulations of fission reactions $Na_{10}^{2+} \to Na_7^+ + Na_3^+$ and $Na_{18}^{2+} \to 2 Na_9^+$ are presented. Dependence of the fission barriers on isomer structure of the parent cluster is analyzed. It is demonstrated that the energy necessary for removing homothetic groups of atoms from the parent cluster is largely independent of the isomer form of the parent cluster. Importance of rearrangement of the cluster structure during the fission process is elucidated. This rearrangement may include transition to another isomer state of the parent cluster before actual separation of the daughter fragments begins and/or forming a "neck" between the separating fragments

Static and dynamic management models production at the entity

Static and dynamic economic-mathematical models for the solution of tasks of information support and optimization of integrated management of engineering procedures at the entity are described. Within these models algorithms of the solution of static and dynamic tasks of information support and complex optimization of management of engineering procedures at the entity are proposed

Sol-gel synthesis and determination of optimal sintering conditions of the Li6.75La3Zr1.75Nb0.25O12 solid electrolyte

Solid electrolytes are widely used in electrochemical devices. Among these materials, electrolytes with the lithium-ion conductivity can be used in high-energy lithium and lithium-ion power sources. The perspective Li6.75La3Zr1.75Nb0.25O12 solid electrolyte was synthesized by modified sol-gel synthesis method using the sparingly soluble Nb2O5 as one of the initial compounds. The influence of pressure and final sintering temperature on phase composition, density and lithium-ion conductivity was studied. Solid electrolyte obtained at 1150°C was single phase and had a cubic structure with the space group Ia-3d. Thus in the presented work, the cubic modification of Li6.75La3Zr1.75Nb0.25O12 was obtained by thermal treatment for 1 h at 1150°C (versus 36 h at 1200°C in the literature). Moreover at this temperature the samples had the highest density and total lithium-ion conductivity (3.9•10-5 Scm-1 at 25°C). According to the SEM study ceramic samples have a dense structure with a particle size ∼1-3 μm. Solid electrolyte was also obtained by isostatic pressing at a pressure of 500 MPa but the values of density and total lithium-ion conductivity were comparable with that of the samples compressed statically. © Published under licence by IOP Publishing Ltd.Council on grants of the President of the Russian Federation: MK-1382.2019.3The reported study was funded by the grant of the President of the Russian Federation according to the research project No MK-1382.2019.3. The research has been carried out with the equipment of the Shared Access Center “Composition of Compounds” of the Institute of High-Temperature Electrochemistry of Ural Branch of RAS, Ekaterinburg, Russian Federation

Impurity effects on the melting of Ni clusters

We demonstrate that the addition of a single carbon impurity leads to significant changes in the thermodynamic properties of Ni clusters consisting of more than a hundred atoms. The magnitude of the change induced is dependent upon the parameters of the Ni-C interaction. Hence, thermodynamic properties of Ni clusters can be effectively tuned by the addition of an impurity of a particular type. We also show that the presence of a carbon impurity considerably changes the mobility and diffusion of atoms in the Ni cluster at temperatures close to its melting point. The calculated diffusion coefficients of the carbon impurity in the Ni cluster can be used for a reliable estimate of the growth rate of carbon nanotubes.Comment: 27 pages, 13 figure

Electrophoretic Deposition and Characterization of Thin-Film Membranes Li7La3Zr2O12

In the presented study, films from tetragonal Li7La3Zr2O12 were obtained by electrophoretic deposition (EPD) for the first time. To obtain a continuous and homogeneous coating on Ni and Ti substrates, iodine was added to the Li7La3Zr2O12 suspension. The EPD regime was developed to carry out the stable process of deposition. The influence of annealing temperature on phase composition, microstructure, and conductivity of membranes obtained was studied. It was established that the phase transition from tetragonal to low-temperature cubic modification of solid electrolyte was observed after its heat treatment at 400 °C. This phase transition was also confirmed by high-temperature X-ray diffraction analysis of Li7La3Zr2O12 powder. Increasing the annealing temperature leads to the formation of additional phases in the form of fibers and their growth from 32 (dried film) to 104 μm (annealed at 500 °C). The formation of this phase occurred due to the chemical reaction of Li7La3Zr2O12 films obtained by electrophoretic deposition with air components during heat treatment. The total conductivity of Li7La3Zr2O12 films obtained has values of ~10−10 and ~10−7 S cm−1 at 100 and 200 °C, respectively. The method of EPD can be used to obtain solid electrolyte membranes based on Li7La3Zr2O12 for all-solid-state batteries. © 2023 by the authors.Russian Academy of Sciences, РАНThis research was funded by the Research Program № 122020100210-9 (IHTE UB RAS), Russian Academy of Sciences, Ural Branch, Russia

Features of Forming a Cubic Li7La3Zr2O12 Film by Tape Casting

Thin films of Li7La3Zr2O12 solid electrolyte were obtained by tape casting.The optimal heat treatment mode without films’ deformation was proposed.The highest conductivity values were observed for the Li7La3Zr2O12 film annealed at 800 °С – 1.5·10–5 S·cm–1 at 215 °С.Received: 13.10.23. Revised: 07.11.23. Accepted: 17.11.23. Available online: 21.11.23.Currently, interest to lithium and lithium-ion all-solid-state power sources is rapidly growing all over the world. However, several issues should be addressed before all-solid-state batteries production: high resistance values of the solid electrolyte membrane and poor contact between electrolyte and electrode materials. The transition to thin-film technologies is one of the promising ways to solve these problems. Tape casting can be proposed to obtain thin-film solid electrolytes. In this research, the features of the structure formation, morphology and lithium-ion conductivity of Li7La3Zr2O12 films were investigated. Li7La3Zr2O12 films with the thickness of 35 μm were obtained by tape casting on Ni substrate. The influence of organic components’ content on homogeneous coatings formation was established. Heat treatment conditions for dried films were chosen based on differential scanning calorimetry and optical dilatometry. Phase change from tetragonal to cubic modification occurs after annealing the Li7La3Zr2O12 films at 700 °C and higher. The annealed Li7La3Zr2O12 films have developed surface, which can lead to improved contact between the solid electrolyte and an electrode in an electrochemical cell. Li7La3Zr2O12 films annealed at 800 °C have the highest lithium-ion conductivity values (2.5·10–7 and 1.5·10–5 S·cm–1 at 90 and 215 °С, respectively). The technology of Li7La3Zr2O12 films formation with the thickness of ~23 μm by tape casting was developed.This research was funded by the Research Program No. 122020100210-9 (IHTE UB RAS), Russian Academy of Sciences, Ural Branch, Russia.The research has been carried out with the equipment of the Shared Access Center “Composition of Compounds” at the IHTE UB RAS

ELECTRICAL CONDUCTIVITY OF Li6.75-3xAlxLa3Zr1.75Nb0.25O12 (x=0–0.25) SOLID ELECTROLYTES

В представленной работе с помощью золь-гель метода синтеза получены твердые электролиты Li6.75-3xAlxLa3Zr1.75Nb0.25O12 (x=0–0.25). Изучены их фазовый состав и электропроводность. Согласно данным РФА, полученные твердые электролиты с x>0.10 содержали примесь в виде La2Zr2O7. Показано, что состав Li6.6Al0.05La3Zr1.75Nb0.25O12 имеет наибольшую электропроводность при 25 °C, которая составляет 6.3·10-4 См/см.Li6.75-3xAlxLa3Zr1.75Nb0.25O12 (x=0–0.25) solid electrolytes have been obtained by sol-gel method. Their phase composition and conductivity have been studied. According to XRD analysis the obtained solid electrolytes with x>0.10 have impurity in the form of La2Zr2O7. The Li6.6Al0.05La3Zr1.75Nb0.25O12 solid electrolyte has the highest total conductivity, 6.3·10-4 S/cm at 25 °C.Исследование выполнено при финансовой поддержке гранта Президента РФ № МК-1382.2019.3

SOL-GEL SYNTHESIS OF Li7-xLa3Zr2-xTaxO12 (x=0.1-0.7) SOLID ELECTROLYTES

Твердые электролиты Li7-xLa3Zr2-xTaxO12 (x=0.1-0.7) были синтезированы с помощью золь-гель метода. Полученные соединения имеют кубическую структуру Ia-3d. В исследуемой системе наибольшей электропроводностью при 25 °C обладает твердый электролит Li6.4La3Zr1.6Ta0.4O12, 1.2·10-4 См/см.Li7-xLa3Zr2-xTaxO12 (x=0.1-0.7) solid electrolytes have been synthesized by solgel method. The obtaining compounds have a cubic structure Ia-3d. The Li6.4La3Zr1.6Ta0.4O12 solid electrolyte has the highest total conductivity, 1.2·10-4 S/cm at 25 °C

Impact of co-adsorbed oxygen on crotonaldehyde adsorption over gold nanoclusters : a computational study

Crotonaldehyde (2-butenal) adsorption over gold sub-nanometer particles, and the influence of co-adsorbed oxygen, has been systematically investigated by computational methods. Using density functional theory, the adsorption energetics of crotonaldehyde on bare and oxidised gold clusters (Au13, d = 0.8 nm) were determined as a function of oxygen coverage and coordination geometry. At low oxygen coverage, sites are available for which crotonaldehyde adsorption is enhanced relative to bare Au clusters by 10 kJ mol−1. At higher oxygen coverage, crotonaldehyde is forced to adsorb in close proximity to oxygen weakening adsorption by up to 60 kJ mol−1 relative to bare Au. Bonding geometries, density of states plots and Bader analysis, are used to elucidate crotonaldehyde bonding to gold nanoparticles in terms of partial electron transfer from Au to crotonaldehyde, and note that donation to gold from crotonaldehyde also becomes significant following metal oxidation. At high oxygen coverage we find that all molecular adsorption sites have a neighbouring, destabilising, oxygen adatom so that despite enhanced donation, crotonaldehyde adsorption is always weakened by steric interactions. For a larger cluster (Au38, d = 1.1 nm) crotonaldehyde adsorption is destabilized in this way even at a low oxygen coverage. These findings provide a quantitative framework to underpin the experimentally observed influence of oxygen on the selective oxidation of crotyl alcohol to crotonaldehyde over gold and gold–palladium alloys