Научные публикации
Uniaxial compaction and sintering of ZrO2−3 mol% Y2O3 using rubber and PEG solutions as binders
Materials Chemistry and Physics Available online 23 September 2024, 129981
https://doi.org/10.1016/j.matchemphys.2024.129981
M.I. Dvornik , O.O. Shichalin, E.A. Mikhailenko, A.A. Burkov, S.V. Nikolenko, N.M. Vlasova , E.V. Chernyakov, A.A. Gnidenko, P.G. Chigrin, I.Yu. Buravlev, N.S. KonovalovaIn the study, investigations were conducted on the uniaxial compaction of samples made from ultrafine ZrO2–3 mol% Y2O3 powder with varying concentrations of binders. Butadiene rubber solution in petrol and aqueous solutions of polyethylene glycols (PEG-400, PEG-1500 and PEG-4000) at concentrations of 6, 12 and 18 % were employed as binders. An exponential increase in the density of all obtained compacts followed a logarithmic trend, reaching 100 % as the compaction pressure increased from 50 to 400 MPa. The density of all green bodies after binder removal, as a function of pressure and initial binder concentration, can be satisfactorily described by a single equation. According to this equation, the binder fills the pores in the green body while having a minimal impact on the volumetric concentration of the solid phase (Zirconia Oxide). The utilization of the PEG-1500 solution as a binder enabled the attainment of the maximum density, which was 4 % higher than the presented averaged trend. The phase composition of the sintered samples consisted solely of tetragonal zirconia. It was determined that increasing the sintered sample density by augmenting the compaction pressure and reducing the binder concentration led to an increase in the green body density from 96.9 to 99.6 %, hardness from 1100 to 1350 HV, fracture toughness from 4.5 to 5.9 MPa*m1/2 and strength from 123 to 960 MPa. The use of powders with a binder mass fraction of 6–12 % enabled the fabrication of cups with a diameter of 5 mm, which could not be compacted at lower binder concentrations or without a binder due to cracking
Spark plasma sintering of cenosphere-derived Cs/Sr-aluminosilicates for 137Cs and 90Sr immobilization in mineral-like ceramics
Journal of Environmental Chemical Engineering. Available online 22 August 2024, 113893
O.O. Shichalin, T.A. Vereshchagina, Buravlev I. Yu, E.A. Kutikhina, A.G. Anshits, A.A. Belov
In this study, a promising method of spark plasma sintering (SPS) was investigated for the fabrication of ceramic matrices designed for the reliable immobilization of highly radioactive radionuclides 137Cs and 90Sr. The ceramic matrices were derived from a mixed composition of two aluminosilicate mineral-like phases – pollucite (Cs,Na)AlSi2O6 and gehlenite Sr2Al2SiO7. The originality of the developed approach lies in the utilization of hydrothermal synthesis for obtaining granulated precursor material. Hollow aluminosilicate microspheres (cenospheres) from coal fly ash served as the initial raw material, which were treated with alkaline solutions containing Cs+ and Sr2+ ions as simulants for the corresponding radionuclides. This method facilitated the achievement of high efficiency in cation removal from solutions exceeding 98%. For a comprehensive examination of the composition and morphology of cenosphere-derived precursor particles, and the influence of sintering temperature on phase and structure formation of ceramic matrices under non-equilibrium conditions of spark plasma heating, various analytical techniques were employed. These included thermogravimetry/differential thermal analysis (TG/DTA), powdered X-ray diffraction analysis (PXRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), as well as the method of low-temperature nitrogen adsorption for determining the specific surface area. The obtained ceramic samples exhibited high values of specific density (2.688–2.915 g/cm³), compressive strength (666–808 MPa), and Vickers microhardness (1.8–2.5 GPa), attesting to their high quality and stability. The results of the hydrolytic stability assessment revealed that the leaching rates of Cs+ and Sr2+ ions from the ceramics are extremely low, within the range of 10-5–10-6 g/cm²·day. These values fully satisfy the requirements of GOST R 50926-96 and the international standard ISO 6961:1982 for solidified forms of high-level waste.
Microstructural evolution and mechanical behavior of WC–4wt.%TiC–3wt.%TaC–12wt.%Co refractory cermet consolidated by spark plasma sintering of mechanically activated powder mixtures
Advanced Powder Technology. Volume 35, Issue 10, October 2024, 104625
https://doi.org/10.1016/j.apt.2024.104625
https://doi.org/10.1016/j.apt.2024.104625
I.Yu. Buravlev, O.O. Shichalin, A.A. Belov, P.A. Marmaza, E.S. Kolodeznikov, M.I. Dvornik, A.N. Sakhnevich, A.A. Buravleva, S.V. Chuklinov, E.K. Papynov
The paper studied the structural features and physicomechanical properties of the WC–4wt.%TiC–3wt.%TaC–12wt.%Co composite refractory hard alloy system obtained by spark plasma sintering (SPS) from a preliminarily mechanically activated powder. It has been shown that preliminary mechanical activation in a planetary mill contributed to the comminution of agglomerates and the formation of a monomodal particle size distribution with a predominance of the submicron fraction, which intensifies the densification processes during subsequent consolidation by the SPS method. Kinetic analysis of the SPS process showed a two-stage sintering pattern with intense densification at temperatures above 790 °C due to rearrangement of WC, TiC, TaC particles and melting of the cobalt binder. It has been found that the SPS method does not lead to the formation of undesirable secondary phases in the entire sintering temperature range. A sintering temperature of 1200 °C is optimal for achieving the best structural homogeneity, density and mechanical properties, providing optimal distribution of carbide phases and the cobalt binder. The microstructure of the sample obtained at 1200 °C represents a refractory skeleton of WC grains with TiC and TaC carbide particles uniformly distributed throughout the volume. Improved fluidity of the melted cobalt binder and its mobile redistribution contribute to increased compactness of the structure and reduced porosity of the material. Samples sintered at 1200 °C possess high physicomechanical characteristics: relative density 99.99 %, hardness HV30 1623.2, bending strength 1125.1 MPa, fracture toughness 10.5 MN⋅m1/2. The abrasive wear resistance of a newly synthesized hard material was evaluated through a turning operation. Results showed durability, indicating promise for cutting tool applications and the need for further research to fully characterize the performance of this novel material.
Production of X-ray Absorbing Ceramics and Products Based on Them for Radiotherapy of the Periorbital Eye Region
Ceramics International. Available online 6 August 2024
https://doi.org/10.1016/j.ceramint.2024.08.008
https://doi.org/10.1016/j.ceramint.2024.08.008
Papynov E.K. Shichalin O.O. Apansevich V.I. Nikiforova N.O. Belov A.A. Buravlev I.Yu. Azon S.A. Buravleva A.A. Gnilyak E.A. Pankratov I.V. Stegniy K.V.
The paper presents an innovative method for producing high-density ceramics based on bioinert tantalum oxide (Ta2O5) and eye shield products utilizing spark plasma sintering (SPS) technology. Eye shields are in high demand for protecting the cornea and other parts of the eye from ionizing radiation during periorbital eye procedures, such as laser therapy, radiotherapy, and Mohs micrographic surgery (MMS). The dynamics of consolidation of microcrystalline Ta2O5 powder under spark plasma heating conditions in the temperature range of 1000–1400 °C were investigated. The structure, phase, and elemental composition of polycrystalline ceramic samples, including the calculation of crystal structure parameters, were studied using XRD, SEM, and EDS methods. The optimal SPS parameters for achieving maximum relative density (up to 100 %) and Vickers microhardness (up to 510 HV) of the obtained ceramics were determined. The performance properties of the ceramics were examined under conditions of a session of short-focus radiation therapy applied to the periorbital facial area. A dosimetric assessment of the absorbing capacity of the ceramics under X-ray irradiation in modes from 40 to 120 keV was conducted. A prototype of a ceramic eye shield product based on Ta2O5 was developed and manufactured for the first time using SPS technology.
Additive manufacturing development of construction materials for a lunar base via spark plasma sintering of volcanic rocks using in-situ resource utilization concept
Construction and Building Materials, Volume 442, 6 September 2024, 137553
https://doi.org/10.1016/j.conbuildmat.2024.137553
Oleg Shichalin, Anton Belov, Igor Buravlev; Erhan Kolodeznikov, Alexander Fedorets, Alexey Lembikov, Semen Zolotnikov, Vitaliy Maiorov, Evgeniy Nozdrachev, Alexei Ruslan, Semen Azon, Alexander Chashchin, Papynov Evgeniy
This work presents an innovative approach for creating ceramic materials based on andesite-basalts for construction on the Moon. Employing the concept of in-situ resource utilization (ISRU), the authors simulated the composition of lunar regolith using volcanic rocks from Kamchatka and Primorsky Krai (Russia, Far East). These rocks were ground into submicron powders and sintered via spark plasma sintering (SPS) at temperatures of 800, 900, and 1000 °C. The resulting ceramic samples demonstrate exceptional physicomechanical properties comparable to lunar regolith – compressive strength up to 566 MPa and Vickers hardness up to 650 HV. Optimal characteristics were achieved at a sintering temperature of 1000 °C with a heating rate of 300 °C/min. It was determined that the heating rate during sintering has a decisive influence on the density of the resulting ceramics.
This research vividly demonstrates the potential of SPS technology and the ISRU concept for creating high-strength construction materials on the Moon using local lunar raw materials, paving the way for large-scale construction of lunar bases utilizing the Moon's own mineral resources..
https://www.sciencedirect.com/science/article/abs/pii/S0950061824026953
Immobilization of 137Cs in NaY type zeolite matrices using various heat treatment methods
Solid State Sciences, Volume 154, August 2024, 107619
https://doi.org/10.1016/j.solidstatesciences.2024.107619
O.O Shichalin E.K. Papynov A.A. Belov a N.P. Ivanov I.Yu Buravlev A.O. Lembikov M.I. Dvornik P.G. Chigrin N.M. Vlasova Yu.A. Mirovoy N.D. Kulagin E.S. Mirovaya A.V. Syuy T.A. Borisenko A.V. Ukhina V.O. Kaptakov A.P. Zavjalov Yun Shi i A.I. Ivanets
The accumulation of liquid radioactive waste presents a significant global challenge, necessitating effective strategies for safe management. This study investigates the immobilization of 137Cs radionuclides, a prominent component of liquid radioactive waste, in ceramic matrices based on 137Cs-saturated NaY Faujasite zeolite. Various thermal methods were employed, including cold pressing and sintering, cold pressing and sintering with microwave assistance, hot pressing, and spark plasma sintering, to enhance immobilization capabilities. Zeolite powder was saturated with 137Cs radionuclides using an adsorption technique with low-activity model liquid radioactive waste. In-situ XRD and dilatometry methods were used to study the thermal behavior during NaY Faujasite annealing. The influence of calcination temperature on lattice parameters and crystallite size was assessed. Immobilization effectiveness was evaluated through relative density, Vickers microhardness, compressive strength, and metal ion leaching kinetics. Mechanistic evaluation was performed using XRD and SEM-EDX studies. Results showed that spark plasma sintering exhibited the highest efficiency for immobilizing 137Cs radionuclides in NaY Faujasite matrices. This research contributes to liquid radioactive waste management by providing insights into the thermal behavior and enhanced immobilization capabilities of ceramic matrices.
https://www.sciencedirect.com/science/article/abs/pii/S1293255824001845
Solidification of cesium containing magnetic zeolite sorbent by spark plasma sintering
Materials Chemistry and Physics, Volume 302, 1 July 2023, 127648
https://doi.org/10.1016/j.matchemphys.2023.127648
by E.K. Papynov, O.O. Shichalin, A.A. Belov, V.S. Pechnikov, A.V. Ognev, A.L. Shkuratov, I. Yu Buravlev, M.I. Dvornik, P.G. Chigrin, N.M. Vlasova, A.N. Fedorets, S.A. Azon, O.V. Kapustina, A.O. Lembikov, V.A. Nepomnyushchaya, Z.E. Kornakova, Е.А. Gridasova, I.G. Tananaev, Yun Shi, A.I. Ivanets
The possibility of effective solidification of spent sorbents containing radioactive cesium by spark plasma sintering (SPS) technology for their safe and long-term disposal was studied. The kinetics of consolidation spent sorbent based on magnetic zeolite after adsorption saturation with cesium (∼23 wt %) under SPS conditions in the range of 700–950 °C was carried out. The structural, elemental and phase composition changes during high-rate (minutes) heating of zeolite powder saturated with Cs+ ions was studied by SEM, EDX and XRD methods. As a result, ceramic samples with mineral-like structure of Fe-substituted pollucite CsFeSi2O6 were successfully obtained. It was determined that the optimal temperature of SPS consolidation was 900 °C, at which the formation of CsFeSi2O6 ceramics with a relative density of 91.2%, compressive strength of 497.6 MPa, Vickers microhardness of 1019 HV, rate of cesium leaching of 2.33 × 10−8 g/cm2 × day was reached. It was found that the mechanism of cesium diffusion from the volume of ceramics corresponded to flushing from the available surface of the sample, the lowest diffusion coefficient was 2.71 × 10−16 cm2/s, as well as the lowest penetration depth of the solution into the volume of ceramics was 1.04 × 10−5 cm. The adsorbents prepared by SPS up to 900 °C retained the magnetization, and at higher temperature the magnetization decreased, which was caused by phase and structural changes of ceramics. The characteristics of ceramic obtained from spent adsorbent complied with the requirements of GOST R 50926–96 and ISO 6961:1982 for solidified Cs-containing radioactive waste.
https://www.sciencedirect.com/science/article/abs/pii/S0254058423003565?via%3Dihub
Synthetic Calcium Silicate Biocomposite Based on Sea Urchin Skeleton for 5-Fluorouracil Cancer Delivery
Materials 2023, 16(9), 3495
This article belongs to the Special Issue Inorganic Functional Materials: Synthesis, Characterization and Application
Received: 21 March 2023 / Revised: 28 April 2023 / Accepted: 28 April 2023 / Published: 1 May 2023
https://doi.org/10.3390/ma16093495
by Evgeniy K. Papynov, Oleg O. Shichalin,Olesya V. Kapustina, Igor Yu. Buravlev, Vladimir I. Apanasevich,Vitaly Yu. Mayorov, Alexander N. Fedorets, Alexey O. Lembikov, Danila N. Gritsuk, Anna V. Ovodova, Sofia S. Gribanova, Zlata E. Kornakova and Nikolay P. Shapkin
Synthetic calcium silicates and phosphates are promising compounds for targeted drug delivery for the effective treatment of cancerous tumors, and for minimizing toxic effects on the patient’s entire body. This work presents an original synthesis of a composite based on crystalline wollastonite CaSiO3 and combeite Na4Ca4(Si6O18), using a sea urchin Mesocentrotus nudus skeleton by microwave heating under hydrothermal conditions. The phase and elemental composition and structure of the obtained composite were studied by XRF, REM, BET, and EDS methods, depending on the microwave heating time of 30 or 60 min, respectively, and the influence of thermo-oxidative post-treatment of samples. The role of the sea urchin skeleton in the synthesis was shown. First, it provides a raw material base (source of Ca2+) for the formation of the calcium silicate composite. Second, it is a matrix for the formation of its porous inorganic framework. The sorption capacity of the composite, with respect to 5-fluorouracil, was estimated, the value of which was 12.3 mg/L. The resulting composite is a promising carrier for the targeted delivery of chemotherapeutic drugs. The mechanism of drug release from an inorganic natural matrix was also evaluated by fitting its release profile to various mathematical models.
https://www.mdpi.com/1996-1944/16/9/3495
Thermal Annealing Driven Enhancement of Perpendicular Magnetic Anisotropy and the Interfacial Dzyaloshinskii–Moriya Interaction in Ultrathin Ru/Co/W/Ru Films
ACS Applied Electronic Materials.
Publication Date:May 4, 2023
https://doi.org/10.1021/acsaelm.3c00254
by Aleksei Yu. Samardak, Alexander Kolesnikov, Maksim E. Stebliy, Andrey V. Gerasimenko, Alexandr V. Sadovnikov, Sergei A. Nikitov, Anastasiia A. Pervishko, Dmitry Yudin, Alexey V. Ognev, Oleg A. Tretiakov, Caihua Wan, Xiu-Feng Han, and Alexander S. Samardak*
Abstract
Spin-related effects discovered in ultrathin magnetic films generally have an interfacial nature. The quality of interfaces between a heavy metal and a ferromagnet is the main driver of surface anisotropy, antisymmetric exchange, chiral damping, spin Hall effect, and spin–orbit torques. To understand the physics and usage of these phenomena for future atomic-scale devices, one has to study systems with disordered interfaces and search there for novel practically desirable effects, which lie beyond the atomic order and surface flatness. Here, we report the interface-related effects in Ru/Co/W/Ru ultrathin films treated by thermal annealing in vacuum. The surface roughness and degree of atomic intermixing at Ru/Co and Co/W interfaces change with increasing annealing temperature up to 240 °C, promoting an enhancement of perpendicular magnetic anisotropy and the interfacial Dzyaloshinskii–Moriya interaction (i-DMI). Further annealing at higher temperatures brings the interface deterioration and, consequently, a drastic degradation of the magnetic properties. Our first-principles calculations qualitatively support the experimental findings, providing an understanding of the i-DMI enhancement nature.
https://pubs.acs.org/doi/10.1021/acsaelm.3c00254
Canonical Monte Carlo multispin cluster method
Journal of Computational and Applied Mathematics.
Volume 427, 1 August 2023, 115153, 138; https://doi.org/10.1016/j.cam.2023.115153
by Kseniia Makarova, Aleksandr Makarov, Vladislav Strongin, Iuliia Titovets, Yuriy Shevchenko, Vitalii Kapitan, Alexey Rybin, Dmitrii Kapitan, Alena Korol, Egor Vasiliev, Pavel Ovchinnikov, Konstantin Soldatov, Viacheslav Trukhin, Konstantin Nefedev
Abstract
We present a new Canonical Multispin-flip Cluster Monte Carlo algorithm for Ising model and describe efficient implementations for hybrid supercomputer. Our method takes advantage of the computing architecture for parallel and multi-threaded operations and uses a sequential cluster state update scheme. Due to the peculiarity of the implementation, the method is more effective for models with a restricted radius of interaction. It is based on combining a random selection of spin cluster by the Monte Carlo method with a complete enumeration of the all states of the selected cluster. To show how it works we applied our method to models of interacting magnetic Ising-moments: ferromagnetic Ising model, the Edwards–Anderson spin glass model, dipolar spin ice on hexagonal and pentagonal Cairo lattices.
https://www.sciencedirect.com/science/article/pii/S0377042723000973
Functionally Gradient Material Fabrication Based on Cr, Ti, Fe, Ni, Co, Cu Metal Layers via Spark Plasma Sintering
Coatings 2023, 13(1), 138; https://doi.org/10.3390/coatings13010138
by Oleg O. Shichalin, Evgeniy K. Papynov, Igor Yu. Buravlev, Anastasiya A. Buravleva, Sergey V. Chuklinov, Ekaterina A. Gridasova, Anton V. Pogodaev, Valreiia A. Nepomnyushchaya, Zlata E. Kornakova, Alexey O. Lembikov, Danila V. Gritsuk, Olesya V. Kapustina, Sofia S. Gribanova and Yun Shi
Abstract
The paper presents a method of obtaining functionally graded material (FGM) of heterogeneous (layered) type based on joined metals Cr-Ti-Fe-Co-Ni-Cu using spark plasma sintering (SPS) technology. The structure, elemental and phase composition of FGM obtained on the basis of joined metals with different values of the temperature coefficient of linear expansion (CTLE) were studied by SEM, EDS and XRD methods with regard to the phase states of the alloy system. Based on the Vickers microhardness data, the evaluation of the mechanical characteristics of FGM in the whole sample body and locally at the contact boundaries of the joined metals was carried out. The results of the study are new and represent a potential for FGM, as well as functionally graded coatings (FGC), which have special physical, chemical and mechanical properties and are highly demanded for the manufacture of structures and products for industrial applications.
https://www.mdpi.com/2079-6412/13/1/138
Ionizing radiation source-open type fabrication using additive technology and spark plasma sintering
Ceramics International – Volume 49, Issue 2, 15 January 2023, Pages 3083-3087
https://doi.org/10.1016/j.ceramint.2022.11.020
E.K. Papynov, O.O. Shichalin, A.A. Belov, I. Yu. Buravlev, A.S. Portnyagin, A.G. Kozlov, E.A. Gridasova, I.G. Tananaev, V.I.Sergienko
Abstract
The paper presents an original method for open-type ionizing radiation source (IRS) fabrication by the means of spark plasma sintering-reactive synthesis (SPS-RS) of SrTiO3 ceramics as an active zone component reinforced by the titanium alloy framework produced by additive technology. Rapid heating regimes of SPS-RS are described with the focus on fabrication of perovskite-phase SrTiO3 crystalline ceramics integrated within the reinforcing Ti–Al–V framework yielding defect- and pore-free monolith. The product is characterized by the excellent crack resistance, Vickers microhardness (480–554 HV), and hydrolytic stability (leaching rate as low as 10−5 g/cm2·day). Presented results show bright prospects for high-tech radioisotope production in the form of open-type IRS meeting the requirements of international standards.
https://www.sciencedirect.com/science/article/pii/S0272884222040044
Order and disorder, crossovers, and phase transitions in dipolar artificial spin ice on the Cairo lattice
Phys. Rev. E 106, 064105 – Published 5 December 2022
DOI:https://doi.org/10.1103/PhysRevE.106.064105
Yuriy Shevchenko, Vladislav Strongin, Vitalii Kapitan, Konstantin Soldatov, Aleksandr Makarov, Mihail Padalko, Roman Volotovskii, and Konstantin Nefedev
Abstract
We study the thermodynamic properties of the magnetic dipolar spin ice on a 2D pentagonal Cairo lattice by using the numerical Metropolis and the complete enumeration methods. We use the model of point Ising-like dipoles considering long-range interactions with up to 100 nearest neighbors and with periodic boundary conditions. There are two explicit peaks both in the temperature behavior of the heat capacity and in the magnetic susceptibility. The low-temperature peak is caused only by long-range interactions and is not present in the model where each dipole interacts only with four nearest neighbors. The height of the peak depends logarithmically on the quantity of dipoles, which indicates a phase transition. The nature of the low-temperature phase transition is related to the transformation from order to disorder in orthogonal sublattices while maintaining the spin ice state and the spin ice rule in the sublattice of crosses. The high-temperature heat capacity peak is associated with the melting of spin ice, i.e., with the crossover from spin ice to paramagnetic chaos. Its height is constant and does not depend on the quantity of dipoles. It is shown that the choice of the radius of the dipole-dipole interaction has a significant effect on the statistical properties of the model. The model may even show the appearance of the long-range order and the phase transition in the case of long-range interaction or its absence in the case of short-range interaction.
https://journals.aps.org/pre/abstract/10.1103/PhysRevE.106.064105
Magnetic phase transition in an amorphous alloy: The theory of random fields of exchange interaction
Journal of Magnetism and Magnetic Materials
Volume 564, Part 2, 15 December 2022, 170172
https://doi.org/10.1016/j.jmmm.2022.170172
V.Belokon, R.Lapenkov, O.Dyachenko
Abstract
In this study, an attempt was made to sequentially calculate the Curie temperature of iron-containing alloys based on the theory of random fields of exchange interaction. This method makes it possible to determine the conditions for the occurrence of ferromagnetism in an amorphous alloy depending on the concentration of exchange-interacting ions, their Holschmidt radius, and the type of crystal lattice of the transition metal.
https://www.sciencedirect.com/science/article/pii/S0304885322010575?via%3Dihub
Titania coatings decorated with ultra-thin gold films: Optical, electrochemical and photoelectrochemical properties
Journal of Alloys and Compounds
Volume 913, 25 August 2022, 165320
https://doi.org/10.1016/j.jallcom.2022.165320
M.S.Vasilyeva, I.V.Lukiyanchuk, K.A.Sergeeva, A.A.Sergeev, E.V.Shchitovskaya, bV.S.Egorkin, V.G.Kuryavii, A.Yu.Ustinov, S.L.Sinebryukhov, S.V.Gnedenkov
Abstract
The coating with a porous structure, having a good adhesion to the substrate and containing titanium dioxide in the modifications of rutile and anatase, has been obtained by plasma electrolytic oxidation of VT1–0 technically pure titanium in a 0.1 M neutral aqueous solution of Na2SO4. Gold 10-nm-layer has been deposited on surface by electron-beam evaporation to obtain Ti/TiO2/Au composite. This gold layer consists of 5 nm gold nanoparticles, which has been determined based on the coherent scattering regions for the diffraction peak (111) using the Debye-Scherrer method. Deposition of 10-nm gold layer on the surface of Ti/TiO2 results in increase in photocurrent densities from 3·10−9 A/cm2 to 4·10−6 A/cm2. Calculation from the slopes of the Mott-Schottky plots enable one to estimate the number of charge carriers (donors) and the flat band potential vs Ag/AgCl, which are ND = 3.9·1019 cm−3, Efb = – 0.14 V for Ti/TiO2 and ND = 3.0·1020 cm−3, Efb = – 0.4 V for Ti/TiO2/Au composite.
https://www.sciencedirect.com/science/article/pii/S092583882201711X
Reaction synthesis of SrTiO3 mineral-like ceramics for strontium-90 immobilization via additional in-situ synchrotron studies
Ceramics International
Volume 48, Issue 14, 15 July 2022, Pages 19597-19605
https://doi.org/10.1016/j.ceramint.2022.03.068
O.O. Shichalin, A.A. Belov, A.P. Zavyalov, E.K. Papynov, S.A. Azon, A.N. Fedorets, I. Yu. Buravlev, M.I.Balanov, I.G.Tananaev, Yun Shi, Qian Zhang, Mingjun Niu, Wentao Liu, A.S.Portnyagin
Abstract
The paper presents spark plasma sintering-reaction synthesis (SPS-RS) of SrTiO3-based mineral-like ceramics with a perovskite structure, which is promising for immobilization of Sr-90 radionuclides. Detailed time-resolved study of phase transformations taking place in the reactive mixture (SrCO3 and TiO2) within 20–1000 °C temperature range was conducted using both in situ heating synchrotron XRD and TGA. Structure and composition dependence on consolidation temperature was revealed by the means of SEM and EDX. We determined optimal temperature conditions for rapid formation of SrTiO3 ceramics with density – 4.49 g cm−3, Vickers hardness – up to 6.2 GPa, compressive strength – 279 MPa, and strontium leaching rate of 10−5–10−6 g cm−2·day. These results clearly show strong applied potential of the presented material for radioactive waste management and isotope production fields.
https://www.sciencedirect.com/science/article/pii/S0272884222008446?via%3Dihub
Synthesis and spark plasma sintering of solid-state matrices based on calcium silicate for 60Co immobilization
Journal of Alloys and Compounds
Volume 912, 15 August 2022, 165233
https://doi.org/10.1016/j.jallcom.2022.165233
O.O.Shichalin, S.B.Yarusova, A.I.Ivanets, E.K.Papynov, A.A.Belov, S.A.Azon, I. YuBuravlev, A.E.Panasenko, P.A.Zadorozhny, V.Yu. Mayorov, D. Kh. Shlyk, V.A.Nepomnyushchaya, O.V.Kapustina, A.E.Ivanova, A.A.Buravleva, E.B.Merkulov, P.S.Gordienko
Abstract
An effective sorption material for the immobilization of cobalt radionuclides into highly safe and reliable solid-state matrices is proposed. The resulting silicate sorbent СaSiO3 had an amorphous mesoporous structure (ABET 53 m2/g) and a sorption capacity Co ions of 3.32 mmol/g. The physico-chemical characteristics of the СaCoSi2O6 sample obtained after Co2+ ions sorption were studied using XRD, N2 and Ar adsorption-desorption, SEM-EDX and TG/DTA methods. Solid-state silicate matrices characterized by high density values (2.86–3.16 g/cm3), compressive strength (150–637 MPa) and Vickers microhardness (1.80–5.25 GPa) were obtained by spark plasma sintering (SPS). The sample obtained at 1000 °C had the lowest values of Co2+ ions leaching (RCo ~10−7 g/(cm2×day)) and diffusion coefficient (De 1.73 ×10−17 cm2/s) from silicate matrices. Thus, the obtained СaCoSi2O6 silicate matrices saturated with Co ions comply with the regulatory requirements of GOST R 50926–96 and ANSI/ANS 16.1 for 60Co immobilization.
https://www.sciencedirect.com/science/article/pii/S0925838822016243?via%3Dihub
Spark Plasma Sintering of WC-Based 10wt%Co Hard Alloy: A Study of Sintering Kinetics and Solid-Phase Processes
Materials 2022, 15(3), 1091;https://doi.org/10.3390/ma15031091
Anastasia A. Buravleva, Alexander N. Fedorets, Anastasia A. Vornovskikh, Alexey V. Ognev, Valeria A. Nepomnyushchaya, Vladimir N. Sakhnevich, Aleksey O. Lembikov, Zlata E. Kornakova, Olesya V. Kapustina, Anna E. Tarabanova, Victor P. Reva, Igor Yu. Buravlev
Abstract
The paper describes the method for producing WC-10wt%Co hard alloy with 99.6% of the theoretical density and a Vickers hardness of ~1400 HV 0.5. Experimental data on densification dynamics, phase composition, morphology, mechanical properties, and grain size distribution of WC-10%wtCo using spark plasma sintering (SPS) within the range of 1000–1200 °C are presented. The high quality of the product is provided by the advanced method of high-speed powder mixture SPS-consolidation at achieving a high degree of densification with minimal calculated grain growth at 1200 °C.
https://www.mdpi.com/1996-1944/15/3/1091
Interwire and Intrawire Magnetostatic Interactions in Fe-Au Barcode Nanowires with Alternating Ferromagnetically Strong and Weak Segments
First published: 03 October 2022https://doi.org/10.1002/smll.202203555
Aleksei Yu. Samardak,Yoo Sang Jeon, Vadim Yu. Samardak, Alexey G. Kozlov, Kirill A. Rogachev, Alexey V. Ognev, Eunjin Jeong, Gyu Won Kim, Min Jun Ko, Alexander S. Samardak,Young Keun Kim
Abstract
Metallic barcode nanowires (BNWs) composed of repeating heterogeneous segments fabricated by template-assisted electrodeposition can offer extended functionality in magnetic, electrical, mechanical, and biomedical applications. The authors consider such nanostructures as a 3D system of magnetically interacting elements with magnetic behavior strongly affected by complex magnetostatic interactions. This study discusses the influence of geometrical parameters of segments on the character of their interactions and the overall magnetic behavior of the array of BNWs having alternating magnetization, because the Fe and Au segments are made of Fe-Au alloys with high and low magnetizations. By controlling the applied current densities and the elapsed time in the electrodeposition, the dimension of the Fe-Au BNWs can be regulated. This study reveals that the influence of the length of magnetically weak Au segments on the interaction field between nanowires is different for samples with magnetically strong 100 and 200 nm long Fe segments using the first-order reversal curve (FORC) diagram method. With the help of micromagnetic simulations, three types of magnetostatic interactions in the BNW arrays are discovered and analy. This study demonstrates that the dominating type of interaction depends on the geometric parameters of the Fe and Au segments and the interwire and intrawire distances.
https://onlinelibrary.wiley.com/doi/10.1002/smll.202203555
Field-Free Spin–Orbit Torque Switching Enabled by the Interlayer Dzyaloshinskii–Moriya Interaction
Nano Lett. 2022, 22, 17, 6857–6865
Publication Date:July 18, 2022
https://doi.org/10.1021/acs.nanolett.1c04786
Wenqing He, Caihua Wan*, Cuixiu Zheng, Yizhan Wang, Xiao Wang, Tianyi Ma, Yuqiang Wang, Chenyang Guo, Xuming Luo, Maksim E. Stebliy, Guoqiang Yu, Yaowen Liu, Alexey V. Ognev, Alexander S. Samardak, and Xiufeng Han*
Abstract
Perpendicularly magnetized structures that are switchable using a spin current under field-free conditions can potentially be applied in spin–orbit torque magnetic random-access memory (SOT-MRAM). Several structures have been developed; however, new structures with a simple stack structure and MRAM compatibility are urgently needed. Herein, a typical structure in a perpendicular spin-transfer torque MRAM, the Pt/Co multilayer and its synthetic antiferromagnetic counterpart with perpendicular magnetic anisotropy, was observed to possess an intrinsic interlayer chiral interaction between neighboring magnetic layers, namely, the interlayer Dzyaloshinskii–Moriya interaction (DMI) effect. Furthermore, using a current parallel to the eigenvector of the interlayer DMI, we switched the perpendicular magnetization of both structures without a magnetic field, owing to the additional symmetry breaking introduced by the interlayer DMI. This SOT switching scheme realized in the Pt/Co multilayer and its synthetic antiferromagnet structure may open a new avenue toward practical perpendicular SOT-MRAM and other SOT devices.
https://pubs.acs.org/doi/10.1021/acs.nanolett.1c04786
Field-free superconducting diode effect in noncentrosymmetric superconductor/ferromagnet multilayers
Nature Nanotechnologyvolume 17, pages 823–828 (2022) Cite this article
Hideki Narita, Jun Ishizuka, Ryo Kawarazaki, Daisuke Kan, Yoichi Shiota, Takahiro Moriyama, Yuichi Shimakawa, Alexey V. Ognev, Alexander S. Samardak, Youichi Yanase & Teruo Ono
Abstract
The diode effect is fundamental to electronic devices and is widely used in rectifiers and a.c.–d.c. converters. At low temperatures, however, conventional semiconductor diodes possess a high resistivity, which yields energy loss and heating during operation. The superconducting diode effect (SDE) which relies on broken inversion symmetry in a superconductor, may mitigate this obstacle: in one direction, a zero-resistance supercurrent can flow through the diode, but for the opposite direction of current flow, the device enters the normal state with ohmic resistance. The application of a magnetic field can induce SDE in Nb/V/Ta superlattices with a polar structure, in superconducting devices with asymmetric patterning of pinning centres or in superconductor/ferromagnet hybrid devices with induced vortices. The need for an external magnetic field limits their practical application. Recently, a field-free SDE was observed in a NbSe2/Nb3Br8/NbSe2 junction; it originates from asymmetric Josephson tunnelling that is induced by the Nb3Br8 barrier and the associated NbSe2/Nb3Br8 interfaces. Here, we present another implementation of zero-field SDE using noncentrosymmetric [Nb/V/Co/V/Ta]20 multilayers. The magnetic layers provide the necessary symmetry breaking, and we can tune the SDE by adjusting the structural parameters, such as the constituent elements, film thickness, stacking order and number of repetitions. We control the polarity of the SDE through the magnetization direction of the ferromagnetic layers. Artificially stacked structures, such as the one used in this work, are of particular interest as they are compatible with microfabrication techniques and can be integrated with devices such as Josephson junctions. Energy-loss-free SDEs as presented in this work may therefore enable novel non-volatile memories and logic circuits with ultralow power consumption.
https://www.nature.com/articles/s41565-022-01159-4
Новое поколение фотокатализаторов видимого света – висмутаты щелочноземельных металлов: синтез, состав, структура и свойства
Journal of Photochemistry & Photobiology, C: Photochemistry Reviews 50 (2022) 100501https://doi.org/10.1016/j.jphotochemrev.2022.100501
Полупроводниковые материалы, содержащие висмут, привлекают внимание исследователей в течение последних нескольких десятилетий в связи с их высокой фотокаталитической активностью в различных реакциях и высокой эффективностью фотоэлектрического преобразования солнечной энергии. Этот интерес также обусловлен тем, что как правило висмутсодержащие полупроводники имеют достаточно малую ширину запрещенной зоны, что делает их чувствительными к излучению в видимой области спектра. Среди различных висмутсодержащих полупроводниковых материалов в отдельную группу выделяют висмутаты щелочноземельных металлов (магния, кальция, стронция и бария). В данной статье проводится обзор исследований по известным методам получения висмутатов различных щелочноземельных металлов с дальнейшим анализом их состава, строения и фотокаталитической активности.
Авторы:
Штарев Дмитрий Сергеевич, в.н.с. лаборатории фотоактивных полупроводниковых материалов ИНТиПМ ДВФУ (Россия)
Ник Серпоне, профессор университета Павии (Италия).
Топологически нетривиальные спиновые текстуры в тонких магнитных пленках
Журнал: «Физика металлов и металловедение»Том: 123 Номер: 3 Год: 2022 Страницы: 260-283
DOI: 10.31857/S0015323022030093;
Представлены результаты передовых исследований в развивающейся области современного магнетизма и спинтроники – топологического наномагнетизма, в рамках которого изучается природа нетривиальных спиновых текстур и топологических эффектов. Наибольшее внимание уделяется киральным спиновым текстурам, недавно открытым в тонких магнитных пленках, таким как скирмионы, скирмиониумы, антискирмионы и другие, их статическим и динамическим свойствам, методам их зарождения и управления, а также перспективам создания функциональных устройств на их основе. Интерес к одно-, двух- и трехмерным магнитным структурам обусловлен не только спектром новых свойств и эффектов, требующих проведения теоретических и экспериментальных исследований, но и потенциалом их практического использования. Возможность получения малых и стабильных магнитных текстур, таких как скирмионы, открывает перспективы для создания новых типов оперативной памяти, конфигурируемой логики и развития нейроморфных вычислений.
Авторы: Cамардак А.С., Колесников А.Г., Давыденко А.В., Стеблий М.Е., Огнев А.В.
Температурная зависимость скорости движения доменной стенки в ферримагнитной структуре Tb/CoFeB/MgO
Journal of Magnetism and Magnetic Materials. Volume 553, 1 July 2022, 169251;
https://doi.org/10.1016/j.jmmm.2022.169251
Одним из возможных направлений развития электроники является использование магнитоупорядоченных сред для задач обработки и хранения информации. Область науки, которая занимается этими подходом, называется спинтроника, и одной из ее актуальных задач является исследование процессов и состояний, реализуемых в ферримагнитных средах. В простейшем случае ферримагнетики – это сплавы состоящие из атомов двух сортов, каждый из которых обладает магнитным моментом. Практически значимой особенностью ферримагнетиков является возможность управления их магнитными свойствами посредствам изменения взаимной концентрации атомов или температуры образца. Изменяя эти параметры, можно добиться состояния с нулевым магнитным или угловым моментом. Первое соответствует максимальной стабильности системы, так как она становится невосприимчива к магнитным полям, второе – максимальной скорости движения доменной стенки.
Влияние ферромагнитного слоя с плоскостной анизотропией на возможность токоиндуцированного перемагничивания в многослойной структуре
Appl. Phys. Lett. 120, 122402 (2022); https://doi.org/10.1063/5.0079400
Разработка надежных методов локального управления ориентации намагниченности посредствам пропускания электрического тока является одной из ключевых задач спинтроники. В работе проведено экспериментально исследование одного из возможных подходов для решения этой задачи посредствам использование двух магнитносвязанных слоев. Пропускание тока через структуру содержащую бислой “тяжелый металл”/ферромагнетик (ТМ/ФМ), может приводить к генерации тока спин-поляризованных электронов из слоя ТМ в слой ФМ в следствие спинового эффекта Холла. Действие такого тока может приводить к переключению ориентации намагниченности в слое ФМ, при условии нарушения симметрии состояния, которое проще всего создается с помощью постоянного магнитного поля в плоскости образца [2]. Практическая сложность реализации такого механизма привела к разработке нескольких методов, позволяющих отказаться от необходимости использования внешнего поля.
Нейросеть «Ограниченная машина Больцмана» помогает в изучении спиновых стекол
Статья на сайте журнала «Письма в ЖЭТФ»: http://jetpletters.ru/ps/2371/article_35091.shtml
Статья «Вычисление основных состояний спиновых стекол, используя ограниченную машину Больцмана» принята к публикации в 8 номере «Письма в ЖЭТФ» – ведущего российского журнала по теоретической физике. Ее авторы – сотрудники Лаборатории суперкомпьютерных и квантовых вычислений и Лаборатории статистической физики конденсированных сред, Департамента теоретической физики и интеллектуальных технологий ИНТиПМ, студенты и аспиранты ДВФУ.