Synthesis and properties of Ferrite-based nanoparticles

The work is dedicated to the study of the structural and optical characteristics, as well as the phase transformations, of ferrite nanoparticles of CeO2-Fe2 O3 . To characterize the results obtained, the methods of scanning and transmission microscopy, X-ray diffraction (XRD) spectroscopy, and Mössbauer spectroscopy were applied. It was found that the initial nanoparticles are polycrystalline structures based on cerium oxide with the presence of X-ray amorphous inclusions in the structure, which are characteristic of iron oxide. The study determined the dynamics of phase and structural transformations, as well as the appearance of a magnetic texture depending on the annealing temperature. According to the Mossbauer spectroscopy data, it has been established that a rise in the annealing temperature gives rise to an ordering of the magnetic properties and a decrease in the concentration of cationic and vacancy defects in the structure. During the life test of synthesized nanoparticles as cathode materials for lithium-ion batteries, the dependences of the cathode lifetime on the phase composition of nanoparticles were established. It is established that the appearance of a magnetic component in the structure result in a growth in the resource lifetime and the number of operating cycles. The results show the prospects of using these nanoparticles as the basis for lithium-ion batteries, and the simplicity of synthesis and the ability to control phase transformations opens up the possibility of scalable production of these nanoparticles for cathode materials. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Synthesis of Cu/CuO nanostructures obtained by electrochemical deposition

Unique physical-chemical properties of nanostructured materials are explained by the crystal structure, geometry and conductive properties that can be controlled by changing the synthesis conditions of nanostructures. In turn, the process of electrochemical deposition makes it possible to control the formation of nanostructures and their physical-chemical properties with high accuracy. Electrochemical synthesis in tracks of the template was carried out in potentiostatic mode at a voltage of 0.5 to 1.5 V. The electrolyte temperature was 25, 35, 50 °C. The composition of the electrolyte solution: CuSO4·5H2O (238g/l), H2SO4 (21g/l). The yield of copper by current from the sulfuric acid solutions of electrolytes is 100%. The growth of nanostructures was monitored by the chronoamperometry method with the "Agilent 34410A" multimeter. Since the template PET matrices are dielectric, a layer of gold with a thickness of no more than 10 nm, which is further a working electrode (cathode) during electrochemical deposition, was deposited to create a conductive layer by magnetron sputtering in a vacuum. By controlling the deposition time, the difference in the applied potentials, the electrolyte temperature, we can change the geometric parameters of synthesized nanostructures. All possible reactions associated with the synthesis process are listed below

Study of the applicability of fe nanotubes as an anode material of lithium-ion batteries

The paper presents the results of the use of iron nanotubes as the anode material of lithiumion batteries. To assess the degradation of the morphology of nanostructures after different numbers of cycles of life tests, the method of scanning electron microscopy, Mossbauer spectroscopy, and X-ray diffraction analysis were applied. It is shown that the decrease in discharge capacity starts at the 380th cycle and is caused by the onset of degradation processes of nanostructures due to the formation of amorphous inclusions and an increase in macrostresses and distortions in the structure. The complete degradation of the structure is observed after the 492nd life cycle test. According to the data obtained by Mossbauer spectroscopy, it has been established that an increase in life cycles leads to an increase in contribution of partial spectrum characteristic of a paramagnetic state. That indicates an increase in degradation rate of nanostructures and an increase in the content of impurity inclusions and amorphous formations in the crystal structure. © 2019, Electromagnetics Academy. All rights reserved

The study of the applicability of electron irradiation for FeNi microtubes modification

The paper presents the results of a study of irradiation of high-energy electrons by an array of FeNi nanostructures with doses from 50 to 500 kGy. Polycrystalline nanotubes based on FeNi, the phase composition of which is a mixture of two face-centered phases, FeNi3 and FeNi, were chosen as initial samples. During the study, the dependences of the phase transformations, as well as changes in the structural parameters as a result of electronic annealing of defects, were established. Using the method of X-ray diffraction, three stages of phase transformations were established: FeNi3 ≌ FeNi→FeNi3 ≪ FeNi→FeNi. After increasing the radiation dose above 400 kGy, no further phase changes were followed, indicating the saturation of defect annealing and completion of the lattice formation process. It was found that an increase in the degree of crystallinity and density of the microstructures as a result of irradiation indicates electronic annealing of defects and a change in the phase composition. It was established that the initial microtubes, in which two phases are present, leads to the appearance of differently oriented crystallites of different sizes in the structure, which contributes to a large number of grain boundaries and also a decrease in density, and are subject to the greatest degradation of structural properties. For modified samples, the degradation rate decreases by 5 times. In the course of the study, the prospects of the use of electron irradiation with doses above 250 kGy for directed modification of FeNi microtubes and changes in structural features were established. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education and Science of the Republic of Kazakhstan: AP05133578Funding: This study was funded by the Ministry of Education and Science of the Republic of Kazakhstan (grant AP05133578)

Fe2o3 nanoparticles doped with gd: Phase transformations as a result of thermal annealing

The aim of this work is to study the effect of the phase composition of the synthesized Fe2O3-Gd2O3 nanoparticles on the efficiency of using magnetic hyperthermia as a basis for experiments. This class of structures is one of the most promising materials for biomedical applications and magnetic resonance imaging. In the course of the study, the dynamics of phase transformations of nanoparticles Fe2O3 → Fe2O3/GdFeO3 → GdFeO3 were established depending on the annealing temperature. It has been determined that the predominance of the GdFeO3 phase in the structure of nanoparticles leads to an increase in their size from 15 to 40 nm. However, during experiments to determine the resistance to degradation and corrosion, it was found that GdFeO3 nanoparticles have the highest corrosion resistance. During the hyperthermal tests, it was found that a change in the phase composition of nanoparticles, as well as their size, leads to an increase in the heating rate of nanoparticles, which can be further used for practical purposes. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan (No. BR05235921)

Evaluation of the Efficiency of Detection and Capture of Manganese in Aqueous Solutions of FeCeOx Nanocomposites Doped with Nb2O5

: The main purpose of this work is to study the effectiveness of using FeCeOx nanocomposites doped with Nb2O5 for the purification of aqueous solutions from manganese. X-ray diffraction, energy-dispersive analysis, scanning electron microscopy, vibrational magnetic spectroscopy, and mössbauer spectroscopy were used as research methods. It is shown that an increase in the dopant concentration leads to the transformation of the shape of nanoparticles from spherical to cubic and rhombic, followed by an increase in the size of the nanoparticles. The spherical shape of the nanoparticles is characteristic of a structure consisting of a mixture of two phases of hematite (Fe2O3) and cerium oxide CeO2. The cubic shape of nanoparticles is typical for spinel-type FeNbO4 structures, the phase contribution of which increases with increasing dopant concentration. It is shown that doping leads not only to a decrease in the concentration of manganese in model solutions, but also to an increase in the efficiency of adsorption from 11% to 75%

Study of helium swelling and embrittlement mechanisms in SiC ceramics

This work is devoted to the study of the radiation damage kinetics and subsequent embrittlement of the near-surface layer of SiC ceramics subjected to irradiation with low-energy He2+ ions. Interest in these types of ceramics is due to their great prospects for use as structural materials for nuclear power, as well as for use in the creation of protective structures for longterm storage of spent nuclear fuel. During the study, the dependences of changes in the structural, mechanical,strength, and morphological characteristics of SiC ceramics depending on irradiation fluence were obtained. It has been established that the greatest changes in the strength properties are associated with the dominance of the crystal lattice swelling effect in the structure due to an increase in the concentration of implanted helium, and its further agglomeration with the formation of vacancy complexes of the He-V type. A model for changing the structural properties of ceramics irradiated with low-energy He2+ ions based on the change in the contributions of the dislocation density concentration, anisotropic distortion of the crystal lattice, and the effect of swelling as a result of implantation is proposed

Study of Helium Swelling and Embrittlement Mechanisms in SiC Ceramics

This work is devoted to the study of the radiation damage kinetics and subsequent embrittlement of the near-surface layer of SiC ceramics subjected to irradiation with low-energy He2+ ions. Interest in these types of ceramics is due to their great prospects for use as structural materials for nuclear power, as well as for use in the creation of protective structures for longterm storage of spent nuclear fuel. During the study, the dependences of changes in the structural, mechanical, strength, and morphological characteristics of SiC ceramics depending on irradiation fluence were obtained. It has been established that the greatest changes in the strength properties are associated with the dominance of the crystal lattice swelling effect in the structure due to an increase in the concentration of implanted helium, and its further agglomeration with the formation of vacancy complexes of the He-V type. A model for changing the structural properties of ceramics irradiated with low-energy He2+ ions based on the change in the contributions of the dislocation density concentration, anisotropic distortion of the crystal lattice, and the effect of swelling as a result of implantation is proposed. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This study was supported by Tomsk State University Development Programme (Priority 2030)

Template synthesis and magnetic characterization of FeNi nanotubes

Iron-nickel nanotubes consisting of 20% Ni and 80% Fe with an aspect ratio of about 100 were synthesized by electrochemical deposition in the pores of polyethylene terephthalate ion-track membranes. The main morphological parameters such as composition, wall thickness and structural characteristics were defined. Macro- and micromagnetic parameters of FeNi nanotubes were determined. © 2017, Electromagnetics Academy. All rights reserved

Study of Corrosion Mechanisms in Corrosive Media and Their Influence on the Absorption Capacity of Fe2O3/NdFeO3 Nanocomposites

This paper presents the results of a study of the change in the stability of Fe2O3/NdFeO3nanocomposites when exposed to aggressive media over a long period of time. The main purpose of these studies is to investigate the mechanisms of degradation and corrosion processes occurring in Fe2O3/NdFeO3nanocomposites, as well as the influence of the phase composition on the properties and degradation resistance. According to the X-ray phase analysis, it was found that the variation of the initial components leads to the formation of mixed composition nanocomposites with different Fe2O0/NdFeO3phase ratios. During corrosion tests, it was found that the dominance of the NdFeO3phase in the composition of nanocomposites leads to a decrease in the degradation and amorphization rate of nanostructures by a factor of 1.5–2 compared to structures in which the Fe2O3phase dominates. Such a difference in the degradation processes indicates the high stability of two-phase composites. Moreover, in the case of an aqueous medium, nanocomposites dominated by the NdFeO3phase are practically not subjected to corrosion and deterioration of properties. The results obtained helped to determine the resistance of Fe2O3/NdFeO3nanocomposites to degradation processes caused by exposure to aggressive media, as well as to determine the mechanisms of property changes in the process of degradation. The results of the study of the absorption capacity of Fe2O3/NdFeO3nanocomposites in the case of the purification of aqueous media from manganese and arsenic showed that a change in the phase ratio in nanocomposites leads to an increase in the absorption efficiency of pollutants from aqueous media. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education and Science of the Republic of Kazakhstan: AP09259184Funding: This study was funded by the Ministry of Education and Science of the Republic of Kazakhstan (grant AP09259184)