The paper presents the results of a systematic study of the influence of thermal annealing on changes in the structural properties and phase composition of metallic nanostructures based on cobalt, as ...well as the possibilities of using an anode material for lithium ion batteries. It was established that as a result of thermal annealing, a four-stage phase transition of nanowires (Co-C/Co-H) → (Co-C) → (Co-C/CoCo2O4) → (CoCo2O4) is observed, accompanied by a rearrangement of the crystal structure, coarsening of the crystallites and the formation of oxide growths on the surface of nanowires. It has been established that with an increase in temperature up to 700 °C, a partial destruction of the oxide layer occurs, which confirms the results of a decrease in the degree of crystallinity and an increase in stresses and strains in the structure. In the course of life tests, the prospect of using nanostructures as the basis for anode materials of lithium-ion batteries has been established. For the initial sample, the number of cycles is about 300 cycles. For oxide nanostructures, an increase in the amount of the resource lifetime of the anode material is observed and in the case of annealed at 500 °C, the resource lifetime exceeds 500 cycles. That corresponds to the average lifetime of the anode materials based on silicon or carbon nanostructures. The dependences of degradation rate of nanostructures in highly concentrated solutions of sulfuric acid were obtained. That will later make it possible to predict the amorphization rate and oxidation of nanowires.
•Phase transition of nanowires (Co-C/Co-H) .→ (Co-C) → (Co-C/CoCo2O4) → (CoCo2O4)•Phase transformation diagram.•Dynamics of the dependence of the change in the degree of crystallinity of Co nanowires on the annealing temperature.•Dynamics of changes in the morphology of Co nanowires as a function of the annealing temperature.
The work is devoted to the study of the radiation resistance of CeO2 microparticles to irradiation with low-energy Не2+ ions with an energy of 40 keV, the irradiation fluence was 1015–1016 ion/cm2. ...The study found that, in contrast to the initial spherical microparticles, irradiated microparticles are a mixture of sintered sphere-like agglomerates, with porous inclusions. According to energy dispersive analysis, an increase in the irradiation fluence leads to an increase in the oxygen content and its uneven distribution over the structure, which leads to a violation of the stoichiometry of the microparticles under study. It was found that the displacement of atoms from the lattice sites as a result of irradiation, as well as their subsequent migration, leads to a change in interplanar spacings and the appearance of distortions and deformations of the crystal lattice. According to X-ray diffraction data, changes in the crystal structure of the microparticles under study are associated with deformation and distortion of the crystal structure due to migration of defects and an increase in the vacancy density of oxygen defects, as well as partial swelling of the crystal structure.
•Study of the stability of the structural properties of CeO2•Irradiated microparticles are a mixture of sintered sphere-like agglomerates, with porous inclusions.•Data on changes in elemental composition and stoichiometric ratio•Changes in the mean square displacements of atoms and the concentration of defects in the structure
The aim of this work is to study the prospects of using Co/CoCo2O4 nanowires as catalysts for the reduction reactions of para-nitroaniline to para-phenyldiamine, as well as CO conversion. Interest in ...these structures is due to their physicochemical properties, spinel structure, leading to an increase in catalytic activity, high stability to external influences and degradation over a long period of operation, etc. The initial nanowires were obtained by electrochemical deposition using polymer template matrices. In turn, the method of electrochemical synthesis makes it possible to control with high accuracy not only the geometry of nanostructures, with the possibility of producing nanostructures with a large aspect ratio of 1:100–1:1000, but also to scale this technology for producing nanostructures on a semi-industrial scale. The use of thermal annealing to initiate phase transformations contributes to the complete rearrangement of the nanowire structure along its entire length, with the formation of a stable phase of the CoCo2O4 spinel type. During the study of the catalytic activity of Со/CoCo2O4 nanowires it was found that the use of oxide nanowires makes it possible to carry out catalytic PNA–PPD reduction reactions, while the initial nanostructures do not exhibit catalytic activity for these compounds. As a result of the study of the catalytic activity of CO gas oxidation, it was found that the presence of Со3+ cations in the structure of oxide nanowires leads to intensification of CO adsorption processes with the formation of intermediate СО2* compounds and an increase in the rate of CO conversion.
•Phase transformations (Со-С/Со-Н) .→ (СоСо2О4) in nanowires.•Catalytic reduction reaction of para-nitroaniline .→ para-phenyldiamine.•High stability of the structural properties and morphology of nanowires after 10 cycles.•The presence of Со3+ cations in the structure of oxide nanowires leads to enhanced CO adsorption processes.
The results of the synthesis and subsequent phase transformations of FeCo nanowires depending on the annealing temperature are presented. An annealing temperature range of 200–800 °C was chosen to ...initialize the processes of annihilation of point defects at low temperatures, as well as phase transformations as a result of oxidation of nanostructures at high annealing temperatures. In the course of the research, a three-stage process of phase transformations was established, accompanied by oxidation of the structure followed by the formation of oxide phases of the spinel type Fe2CoO4 and Co3O4. It was found that at temperatures of 400 °C and 600 °C, the introduction of oxygen occurs nonuniformly along grain boundaries with the subsequent formation of oxide compounds, and in the case of annealing at a temperature of 800 °C, the oxygen distribution in the structure of nanowires becomes uniform, which indicates the complete oxidation of nanowires with isotropic the formation of oxide phases in the entire volume of nanowires. The prospects of using oxide biphasic nanowires for catalytic reduction reactions para-nitroaniline - para-phenyldiamine are shown.
The work is devoted to the study of the effect of lithium doping on the structural and electrical properties of ferroelectric ceramics LixSr1-xTiO3. The concentration of lithium dopant varied from ...x = 0.01 to 0.15. It was found that an increase in lithium during the synthesis leads to phase transformations of the type SrTiO3/TiO2 → SrTiO3/TiO2/Li2Ti3O7 → SrTiO3/Li2Ti3O7. According to the data obtained, the capacitance value for samples with a lithium content in the structure x = 0–0.01 is 0.05–0.07*10-9 F*cm-1, an increase in lithium concentration to x = 0.05–0.1 in the structure leads to an increase in the capacity value of 0.6*10-9 F*cm-1 with a further drop in the frequency range 103–105 Hz to 0.05–0.07*10-9 F*cm-1, and at a lithium concentration of x = 0.15, the capacitance increases sharply and retains its value throughout frequency range within the range of 0.9–1.2 0.05–0.07*10-9 F*cm-1. According to the data obtained, the deviation ΔT from the Curie-Weiss law for the studied ceramics is no more than 4, while the value of the Curie-Weiss constant is characteristic of ferroelectrics. The small value of ΔT indicates that for the initiation of phase transitions from tetragonal/orthorhombic to cubic at temperatures not exceeding 100–110 °C.
This article is devoted to the study of the efficiency of thermal annealing of nanostructures for phase transformations of the FeCo – Fe
2
CoO
4
/Co
3
O
4
-spinel type, as well as the subsequent ...application of the obtained nanotubes as a basis for anode materials of lithium-ion batteries. The choice of these types of nanotubes for use as a basis for anode materials is due to their structure, as well as the great potential of using spinel structures in this area, interest in which is manifested due to the possibility of accelerating lithiation processes and long-term preservation of the specific capacity of batteries. During the study, it was found that for spinel structures, the formation of oxide growths on the surface of nanotubes, the presence of which is associated with oxidative processes during annealing, is observed. Testing the applicability of these structures as anode materials showed that the formation of oxide spinel structures of type Fe
2
CoO
4
/Co
3
O
4
leads to an increase in the number of cycles by 1.5–1.7 times compared to the original nanotubes. The efficiency of increasing the lifetime of anode materials is due to an increase in resistance to degradation of Fe
2
CoO
4
/Co
3
O
4
structures, due to the formation of oxide phases, leading to an acceleration of lithation processes.
Absract
The paper presents the results of studying of structural and phase properties of films based on copper–bismuth, copper–magnesium, copper–nickel, obtained by the method of electrochemical ...deposition. The dependences of the influence of the synthesis conditions on the phase composition and the strength and corrosion properties of the synthesized films are established. Interest in two-component films based on selected metals is due to their structural properties and the prospect of using them as protective coatings. The choice of elements of bismuth, magnesium and nickel in combination with copper is due to the possibility of obtaining structures with different phases, which can have a significant impact on the corrosion properties of films when interacting with aggressive media. During tests for corrosion resistance, it was found that a decrease in the concentration of copper and copper-containing phases leads to an increase in resistance to degradation and oxidation of thin films.
The paper presents the results of a study of the phase composition, structural properties, and applicability of perovskite-like ceramics of the LiZrBaOx type obtained by solid-phase synthesis. ...According to the data of X-ray phase analysis, mapping, and TEM images, it was established that the ceramic structure consists of core-shell particles where the ZrO2 phase acts as the core, and the ZrBa2O4 and Zr2Li6O7 phases are a double shell, one of which is the disordered Zr2Li6O7 shell. The presence of three phases in the structure leads to a sufficiently strong distortion of the crystalline structure, as well as its deformation. In the course of the research, the prospects of using ceramics based on LiZrBaOx as the basis for the cathode materials of lithium-ion batteries were established.
The paper presents results of helium accumulation processes in structure of the near-surface layer of WO3 microparticles as a result of irradiation with low-energy helium ions He2+ 40 keV. The ...dependences of changes in morphology of surface layer at irradiation, as well as the structural characteristics of microparticles at irradiation, are established. According to the data obtained, an increase in the irradiation fluence leads to the formation of cracks and fused regions in the surface layer. It was found that, at an irradiation dose of 1016 ion/cm2, the formation of disordered regions in the structure characteristic of helium inclusions is observed.
The paper presents the results of the study of structural, morphological, optical, and mechanical properties of lithium-containing ceramics obtained using the method of mechanochemical solid-phase ...synthesis. The purpose of this work is to assess the possibility of obtaining lithium-containing ceramics of the two-phase type, as well as the formation effect of the cubic phase of LiTiO
2
on changes in the properties of ceramics. The relevance of this study is to obtain new data on the properties of lithium-containing ceramics, which have great prospects in their use as blanket materials for tritium reproduction. During the study, it was found that the formation of the LiTiO
2
cubic phase leads to a change in the morphological features of ceramics, with the formation of sphere-like agglomerates of a nanoscale scale. An increase in the contribution of the LiTiO
2
phase leads to a shift of the fundamental absorption edge, as well as the appearance of additional absorption bands. During mechanical tests for the determination of resistance to destruction by single compression, it was found that an increase in ceramic density, which is due to an increase in the contribution of the cubic phase, leads to an increase in resistance by 70–85%.
