Synthesis and Structural and Strength Properties of xLi2ZrO3-(1-x)MgO Ceramics-Materials for Blankets

The article considers the effect of doping with magnesium oxide (MgO) on changes in the properties of lithium-containing ceramics based on lithium metazirconate (Li₂ZrO₃). There is interest in this type of ceramics on account of their prospects for application in tritium production in thermonuclear power engineering, as well as several other applications related to alternative energy sources. During the investigations undertaken, it was found that variation in the MgO dopant concentration above 0.10-0.15 mol resulted in the formation of impurity inclusions in the ceramic structure in the form of a MgLi₂ZrO₄ phase, the presence of which resulted in a rise in the density of the ceramics, along with elevation in resistance to external influences. Moreover, during experimental work on the study of the thermal stability of the ceramics to external influences, it was found that the formation of two-phase ceramics resulted in growth in the preservation of stable strength properties during high-temperature cyclic tests. The decrease in strength characteristics was observed to be less than 1%.

Study of the Aid Effect of CuO-TiO2-Nb2O5 on the Dielectric and Structural Properties of Alumina Ceramics

The aim of this work is to study the structural, dielectric, and mechanical properties of aluminum oxide ceramics with the triple sintering additive 4CuO-TiO₂-2Nb₂O₅. With an increase in sintering temperature from 1050 to 1500 °C, the average grain size and the microhardness value at a load of 100 N (HV0.1) increased with increasing density. It has been shown that at a sintering temperature of 1300 °C, the addition of a 4CuO-TiO₂-2Nb₂O₅ additive increases the low-frequency permittivity (2-500 Hz) in alumina ceramic by more than an order of magnitude due to the presence of a quadruple perovskite phase. At the same time, the density of such ceramics reached 89% of the theoretical density of α-Al₂O₃, and the microhardness value HV0.1 was 1344. It was observed that the introduction of 5 wt.% 4CuO-TiO₂-2Nb₂O₅ in the raw mixture remarkably increases values of shrinkage and density of sintered ceramics. Overall, the results of this work confirmed that introducing the 4CuO-TiO₂-2Nb₂O₅ sintering additive in the standard solid-phase ceramics route can significantly reduce the processing temperature of alumina ceramics, even when micron-sized powders are used as a starting material. The obtained samples demonstrated the potential of α-Al₂O₃ with the triple additive in such applications as electronics, microwave technology, and nuclear power engineering.

Study of the Mechanisms of Radiation Softening and Swelling upon Irradiation of TiTaNbV Alloys with He2+ Ions with an Energy of 40 keV

This paper presents simulation results of the ionization losses of incident He²⁺ ions with an energy of 40 keV during the passage of incident ions in the near-surface layer of alloys based on TiTaNbV with a variation of alloy components. For comparison, data on the ionization losses of incident He²⁺ ions in pure niobium, followed by the addition of vanadium, tantalum, and titanium to the alloy in equal stoichiometric proportions, are presented. With the use of indentation methods, the dependences of the change in the strength properties of the near-surface layer of alloys were determined. It was established that the addition of Ti to the composition of the alloy leads to an increase in resistance to crack resistance under high-dose irradiation, as well as a decrease in the degree of swelling of the near-surface layer. During tests on the thermal stability of irradiated samples, it was found that swelling and degradation of the near-surface layer of pure niobium affects the rate of oxidation and subsequent degradation, while for high-entropy alloys, an increase in the number of alloy components leads to an increase in resistance to destruction.

Eco-Friendly Electroless Template Synthesis of Cu-Based Composite Track-Etched Membranes for Sorption Removal of Lead(II) Ions

This paper reports the synthesis of composite track-etched membranes (TeMs) modified with electrolessly deposited copper microtubules using copper deposition baths based on environmentally friendly and non-toxic reducing agents (ascorbic acid (Asc), glyoxylic acid (Gly), and dimethylamine borane (DMAB)), and comparative testing of their lead(II) ion removal capacity via batch adsorption experiments. The structure and composition of the composites were investigated by X-ray diffraction technique and scanning electron and atomic force microscopies. The optimal conditions for copper electroless plating were determined. The adsorption kinetics followed a pseudo-second-order kinetic model, which indicates that adsorption is controlled by the chemisorption process. A comparative study was conducted on the applicability of the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption models to define the equilibrium isotherms and the isotherm constants for the prepared composite TeMs. Based on the regression coefficients R², it has been shown that the Freundlich model better describes the experimental data of the composite TeMs on the adsorption of lead(II) ions.

Investigation of the Effect of PbO Doping on Telluride Glass Ceramics as a Potential Material for Gamma Radiation Shielding

The purpose of this paper is to study the effect of PbO doping of multicomponent composite glass-like ceramics based on TeO₂, WO₃, Bi₂O₃, MoO₃, and SiO₂, which are one of the promising materials for gamma radiation shielding. According to X-ray diffraction data, it was found that the PbO dopant concentration increase from 0.10 to 0.20-0.25 mol results in the initialization of the phase transformation and structural ordering processes, which are expressed in the formation of SiO₂ and PbWO₄ phases, and the crystallinity degree growth. An analysis of the optical properties showed that a change in the ratio of the contributions of the amorphous and ordered fractions leads to the optical density increase and the band gap alteration, as well as a variation in the optical characteristics. During the study of the strength and mechanical properties of the synthesized ceramics, depending on the dopant concentration, it was found that when inclusions in the form of PbWO₄ are formed in the structure, the strength characteristics increase by 70-80% compared to the initial data, which indicates the doping efficiency and a rise in the mechanical strength of ceramics to external influences. During evaluation of the shielding protective characteristics of the synthesized ceramics, it was revealed that the formation of PbWO₄ in the structure results in a rise in the high-energy gamma ray absorption efficiency.

Synthesis and Characterization of the Properties of (1-x)Si3N4-xAl2O3 Ceramics with Variation of the Components

The aim of this paper is to study the effect of variation in the component ratio of (1-x)Si₃N₄-xAl₂O₃ ceramics on the phase composition, strength and thermal properties of ceramics. To obtain ceramics and their further study, the solid-phase synthesis method combined with thermal annealing of samples at a temperature of 1500 °C typical for the initialization of phase transformation processes was used. The relevance and novelty of this study lies in obtaining new data on the processes of phase transformations with a variation in the composition of ceramics, as well as determining the effect of the phase composition on the resistance of ceramics to external influences. According to X-ray phase analysis data, it was found that an increase in the Si₃N₄ concentration in the composition of ceramics leads to a partial displacement of the tetragonal phase of SiO₂ and Al₂(SiO₄)O and an increase in the contribution of Si₃N₄. Evaluation of the optical properties of the synthesized ceramics depending on the ratio of the components showed that the formation of the Si₃N₄ phase leads to an increase in the band gap and the absorbing ability of the ceramics due to the formation of additional absorption bands from 3.7-3.8 eV. Analysis of the strength dependences showed that an increase in the contribution of the Si₃N₄ phase with subsequent displacement of the oxide phases leads to a strengthening of the ceramic by more than 15-20%. At the same time, it was found that a change in the phase ratio leads to the hardening of ceramics, as well as an increase in crack resistance.

Evaluation of the Influence of Grain Sizes of Nanostructured WO3 Ceramics on the Resistance to Radiation-Induced Softening

The main purpose of this study is to test a hypothesis about the effect of grain size on the resistance to destruction and changes in the strength and mechanical properties of oxide ceramics subjected to irradiation. WO₃ powders were chosen as objects of study, which have a number of unique properties that meet the requirements for their use as a basis for inert matrices of dispersed nuclear fuel. The grain-size variation in WO₃ ceramics was investigated by mechanochemical grinding of powders with different grinding speeds. Grinding conditions were experimentally selected to obtain powders with a high degree of size homogeneity, which were used for further research. During evaluation of the strength properties, it was found that a decrease in the grain size leads to an increase in the crack resistance, as well as the hardness of ceramics. The increase in strength properties can be explained by an increase in the dislocation density and the volume contribution of grain boundaries, which lead to hardening and an increase in resistance. During determination of the radiation damage resistance, it was found that a decrease in grain size to 50-70 nm leads to a decrease in the degree of radiation damage and the preservation of the resistance of irradiated ceramics to destruction and cracking.

Study of Radiation-Induced Damage Processes in CeZrO4-YZrO3 Ceramics Caused by Helium Irradiation

Composite oxide ceramics CeZrO₄-YZrO₃ obtained by mechanochemical synthesis were chosen as objects of study. The most dangerous type of radiation defect in structural materials is associated with helium accumulation in the structure of the near-surface layer. This can lead to the destruction and swelling of the material, resulting in a decrease in its strength and thermal characteristics. During the studies, it was found that the most significant structural changes (deformation of the crystal lattice, the magnitude of microdistortions of the crystal lattice) are observed with irradiation fluence above 5×10¹⁶ ion/cm², while the nature of the changes is exponential. X-ray diffraction analysis found that the nature of the crystal structure deformation has a pronounced type of stretching due to the accumulation of implanted helium and its subsequent agglomeration. A comparative analysis with data on microdistortions of the crystal lattice and the values of microhardness and softening of ZrO₂ and CeO₂ showed that two-phase ceramics of the cubic type CeZrO₄-YZrO₃ are more resistant to radiation-induced degradation than single-phase ZrO₂ and CeO₂. Results of strength and thermophysical characteristics showed that the presence of two phases increases resistance to destruction and disorder, leading to a decrease in strength and thermal conductivity.

Study of Phase Transformations and Hyperfine Interactions in Fe3O4 and Fe3O4@Au Nanoparticles

The paper presents the results of a study of iron oxide nanoparticles obtained by chemical coprecipitation, coated (Fe₃O₄@Au) and not coated (Fe₃O₄) with gold, which were subjected to thermal annealing. To characterize the nanoparticles under study, scanning and transmission electron microscopy, X-ray diffraction, and Mössbauer spectroscopy on ⁵⁷Fe nuclei were used, the combination of which made it possible to establish a sequence of phase transformations, changes in morphological and structural characteristics, as well as parameters of hyperfine interactions. During the studies, it was found that thermal annealing of nanoparticles leads to phase transformation processes in the following sequence: nonstoichiometric magnetite (Fe_3-γO₄) → maghemite (γ-Fe₂O₃) → hematite (α-Fe₂O₃), followed by structural ordering and coarsening of nanoparticles. It is shown that nanoparticles of nonstoichiometric magnetite with and without gold coating are in the superparamagnetic state with a slow relaxation rate. The magnetic anisotropy energy of nonstoichiometric magnetite is determined as a function of the annealing temperature. An estimate was made of the average size of the region of magnetic ordering of Fe atoms in nonstoichiometric magnetite, which is in good agreement with the data on the average sizes of nanoparticles determined by scanning electron microscopy.

Study of the Effect of Two Phases in Li4SiO4-Li2SiO3 Ceramics on the Strength and Thermophysical Parameters

The paper studies the effect of Li₂SiO₃/Li₄SiO₄ phase formation in lithium-containing ceramics on the strength and thermophysical characteristics of lithium-containing ceramics, which have great prospects for use as blanket materials for tritium propagation. During the phase composition analysis of the studied ceramics using the X-ray diffraction method, it was found that an increase in the lithium component during synthesis leads to the formation of an additional orthorhombic Li₂SiO₃ phase, and the main phase in ceramics is the monoclinic Li₄SiO₄ phase. An analysis of the morphological features of the synthesized ceramics showed that an increase in the Li₂SiO₃ impurity phase leads to ceramic densification and the formation of impurity grains near grain boundaries and joints. During determination of the strength characteristics of the studied ceramics, a positive effect of an increase in the Li₂SiO₃ impurity phase and dimensional factors on the strengthening and increase in the resistance to external influences during compression of ceramics was established. During tests for resistance to long-term thermal heating, it was found that for two-phase ceramics, the decrease in strength and thermophysical characteristics after 500 h of annealing was less than 5%, which indicates a high resistance and stability of these ceramics in comparison with single-phase orthosilicate ceramics.

Study of the Reinforcement Effect in (0.5-x)TeO2-0.2WO3-0.1Bi2O3-0.1MoO3-0.1SiO2-xCNDs Glasses Doped with Carbon Nanodiamonds

The purpose of this study is to examine the influence of carbon nanodiamonds on the reinforcement and hardening of telluride glasses, as well as to establish the dependence of the strengthening properties and optical characteristics of glasses on CND concentration. According to X-ray diffraction data, the synthesized glasses have an amorphous structure despite the addition of CNDs, and at high concentrations of CNDs, reflections characteristic of small crystalline particles of carbon nanodiamonds are observed. An analysis of the strength properties of glasses depending on the concentration of the CND dopant showed that an increase in the CND concentration to 0.10-0.15 mol. leads to an increase in hardness by 33-50% in comparison with undoped samples. The studies carried out to determine the resistance to external influences found that doping leads to an increase in the resistance of strength characteristics against destruction and embrittlement, and in the case of high concentrations, the change in strength properties is minimal, which indicates a high ceramic stability degree. The study of the radiation resistance of synthesized glasses found that the addition of CNDs leads to an increase in resistance to radiation damage when irradiated with gamma rays, while also maintaining resistance to high radiation doses. The study of the shielding characteristics found that the addition of CNDs is most effective in shielding gamma rays with energies of 130-660 MeV.

Investigation of the Efficiency of Shielding Gamma and Electron Radiation Using Glasses Based on TeO2-WO3-Bi2O3-MoO3-SiO to Protect Electronic Circuits from the Negative Effects of Ionizing Radiation

This article considers the effect of MoO₃ and SiO additives in telluride glasses on the shielding characteristics and protection of electronic microcircuits operating under conditions of increased radiation background or cosmic radiation. MoO₃ and SiO dopants were chosen because their properties, including their insulating characteristics, make it possible to avoid breakdown processes caused by radiation damage. The relevance of the study consists in the proposed method of using protective glasses to protect the most important components of electronic circuits from the negative effects of ionizing radiation, which can cause failures or lead to destabilization of the electronics. Evaluation of the shielding efficiency of gamma and electron radiation was carried out using a standard method for determining the change in the threshold voltage (∆U) value of microcircuits placed behind the shield and subjected to irradiation with various doses. It was established that an increase in the content of MoO₃ and SiO in the glass structure led to an increase of up to 90% in the gamma radiation shielding efficiency, while maintaining the stability of microcircuit performance under prolonged exposure to ionizing radiation. The results obtained allow us to conclude that the use of protective glasses based on TeO₂-WO₃-Bi₂O₃-MoO₃-SiO is highly promising for creating local protection for the main components of microcircuits and semiconductor devices operating under conditions of increased background radiation or cosmic radiation.

Study of Radiation Resistance of WO3 Microparticles under Irradiation with Heavy Kr15+ and Xe22+ Ions

In this work, we consider the effect of irradiation with heavy Kr¹⁵⁺ and Xe²²⁺ ions on the change in the structural and strength properties of WO₃ microparticles, which are among the candidates for inert matrix materials. Irradiation with heavy Kr¹⁵⁺ and Xe²²⁺ ions was chosen to determine the possibility of simulation of radiation damage comparable to the impact of fission fragments. During the studies, it was found that the main changes in the structural properties with an increase in the irradiation fluence are associated with the crystal lattice deformation and its anisotropic distortion, which is most pronounced during irradiation with heavy Kr¹⁵⁺ ions. An assessment of the gaseous swelling effect due to the radiation damage accumulation showed that a change in the ion type during irradiation leads to an increase in the swelling value by more than 8-10%. Results of strength changes showed that the most intense decrease in the hardness of the near-surface layer is observed when the fluence reaches more than 10¹² ion/cm², which is typical for the effect of overlapping radiation damage in the material. The dependences obtained for the change in structural and strength properties can later be used to evaluate the effectiveness of the use of refractory oxide materials for their use in the creation of inert matrices of nuclear fuel.

Study of Structural and Strength Changes in Lithium-Containing Ceramics-Potential Blanket Materials for Nuclear Power, Subjected to High-Dose Proton Irradiation

The paper considers the hydrogenation processes in Li₂TiO₃ ceramics under irradiation with protons with an energy of 500 keV and fluences of 1 × 10¹⁰-5 × 10¹⁷ ion/cm². The choice of the type of irradiation, as well as the irradiation fluences, is based on the possibilities of modeling hydrogenation processes and studying the kinetics of structural changes caused by the accumulation of radiation damage. The choice of Li₂TiO₃ ceramics as objects of research is due to their prospects for using as blanket materials of thermonuclear reactors for the tritium production and accumulation. It was found that the formation of point defects and their subsequent evolution associated with the formation of complex compounds and the filling of pores, followed by the formation of gas-filled bubbles, the presence of which leads to a decrease in crack resistance and resistance to destruction of the near-surface layer. Based on the data on structural changes and evolution of the crystal lattice parameters, its swelling, a description of the destruction processes associated with hydrogenation in Li₂TiO₃ ceramics was proposed. Also, during the studies, it was found that at irradiation fluences above 1 × 10¹⁷ ion/cm², the appearance of impurity inclusions characteristic of the TiO₂ phase was observed, the presence of which indicates the crystal lattice destruction processes because of accumulation of radiation damage and deformations caused by them. Critical doses are established at which there is a sharp deterioration in strength and crack resistance, reflecting the resistance of ceramics to mechanical external influences.

Study of Degradation Mechanisms of Strength and Thermal-Physical Properties of Nitride and Carbide Ceramics-Promising Materials for Nuclear Energy

The dependences of changes in the strength properties of nitride and carbide ceramics under high temperature irradiation with Kr¹⁵⁺ and Xe²²⁺ heavy ions at irradiation doses of 10¹²-10¹⁵ ions/cm² are presented in this work. The irradiation was chosen to simulate radiation damage processes that are closest to the real conditions of reactor tests in operating modes of increased temperatures. Polycrystalline ceramics based on AlN, Si₃N₄ nitrides, and SiC carbides were chosen as objects of research, as they have great prospects for use as a basis for structural materials for high-temperature nuclear reactors, as well as materials for nuclear waste disposal. During these studies the effect of radiation damage caused by irradiation with different fluences on the change in mechanical strength and hardness were determined, and the mechanisms causing these changes depending on the type of irradiated materials were proposed. The novelty of this study is in the results obtained determining the stability of the strength and thermophysical parameters of nitride and carbide ceramics exposed to high-temperature irradiation, which made it possible to determine the main stages and mechanisms for changing these parameters depending on the accumulated radiation damage. The relevance of this study consists not only in obtaining new data on the properties of structural materials exposed to ionizing radiation, but also in the possibility of determining the mechanisms of radiation damage in ceramics.

Boron and Gadolinium Loaded Fe3O4 Nanocarriers for Potential Application in Neutron Capture Therapy

In this article, a novel method of simultaneous carborane- and gadolinium-containing compounds as efficient agents for neutron capture therapy (NCT) delivery via magnetic nanocarriers is presented. The presence of both Gd and B increases the efficiency of NCT and using nanocarriers enhances selectivity. These factors make NCT not only efficient, but also safe. Superparamagnetic Fe3O4 nanoparticles were treated with silane and then the polyelectrolytic layer was formed for further immobilization of NCT agents. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), ultraviolet-visible (UV-Vis) and Mössbauer spectroscopies, dynamic light scattering (DLS), scanning electron microscopy (SEM), vibrating-sample magnetometry (VSM) were applied for the characterization of the chemical and element composition, structure, morphology and magnetic properties of nanocarriers. The cytotoxicity effect was evaluated on different cell lines: BxPC-3, PC-3 MCF-7, HepG2 and L929, human skin fibroblasts as normal cells. average size of nanoparticles is 110 nm; magnetization at 1T and coercivity is 43.1 emu/g and 8.1, respectively; the amount of B is 0.077 mg/g and the amount of Gd is 0.632 mg/g. Successful immobilization of NCT agents, their low cytotoxicity against normal cells and selective cytotoxicity against cancer cells as well as the superparamagnetic properties of nanocarriers were confirmed by analyses above.

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.