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Abstract ZrO2 ceramics have wide applications as structural materials in industrial, scientific, and technological fields. Despite the large number of works devoted to the influence of synthesis parameters on the formation of different phases of ZrO2 and the properties of the obtained ceramics, the effect of sintering temperature on the characteristics of the porous ZrO2 ceramics has not been addressed sufficiently. This study focuses on examining how sintering temperature affects the phase composition, microstructure, dielectric properties, and mechanical properties of porous stabilized zirconium dioxide ceramics. Phase transformations during sintering at various temperatures were identified using powder X-ray diffraction and Raman spectroscopy. The results indicate that fully stabilized cubic ZrO2 with satisfactory mechanical properties (HV0.5 = 580) and a porosity of 21.5% was achieved at temperatures of 1400 and 1500 ℃. At lower sintering temperatures, the obtained samples exhibited multiphase composition and high porosity. The reasons for the formation of the CaZrO3 phase at sintering temperatures of 1000–1200 ℃ were established using scanning electron microscopy, energy dispersive analysis, and thermodynamic considerations of the solid-phase reactions. AC dielectric measurements showed that the synthesized samples have high-Q characteristics; and that the dielectric constant can be controlled by changing the sintering temperature.

The key objective of this study is to determine the effect of interphase boundaries, the formation of which is caused by the variation of Li2ZrO3/MgLi2ZrO4 phases in lithium-containing ceramics based on lithium metazirconate, on the resistance to near-surface layer destruction processes associated with irradiation with He2+ ions. During the observation of the deformation effects that have an adverse impact on the volumetric swelling of the near-surface layers of ceramics, the thermal expansion factor caused by high-temperature irradiation was considered, simulating conditions as close as possible to the operating conditions of these materials as blankets for tritium propagation. During the studies conducted, it was established that an elevation in the contribution of MgLi2ZrO4 in the composition of ceramics leads to a rise in resistance to deformation swelling caused by structural distortions of the crystal lattice, due to a decrease in the effect of thermal expansion, alongside the presence of interphase boundaries. The established dependencies of the change in the hardness of the near-surface layer of the studied ceramics made it possible to establish the kinetics of softening caused by the deformation distortion of the crystalline structure, as well as to determine the relationship between volumetric swelling and softening (change in hardness) and a decrease in crack resistance (change in the value of resistance to single compression).

The article presents the results of experimental studies of the effect of the stabilizing MgO dopant using the electron spin resonance (ESP) method on enhancement of the stability of Li2ZrO3 ceramics to defect formation processes and accumulation of radiolysis products in the near-surface layer in the case of high-dose irradiation with protons simulating the hydrogenation effects characteristic of processes associated with tritium production. During the conducted studies, it was established that the addition of the stabilizing MgO dopant results in formation of inclusions in the form of the tetragonal MgLi2ZrO4 phase, which leads to an increase in the resistance of the near-surface layers to destructive damage due to the accumulation of structural damage (oxygen vacancies and point defects), as well as products of the physicochemical processes of radiolysis, characteristic of high irradiation fluence values. It was found that in the case of unmodified Li2ZrO3 ceramics, the formation of HC2 – centers is observed at a fluence of 1016 proton/cm2, while for two-phase ceramics, the formation of HC2 – centers is observed at higher fluences, while the intensity of the bands is significantly less than in the case of single-phase unmodified ceramics. The difference in the nature of changes in the intensities of singlet bands responsible for the presence of vacancy defects in the damaged layer, as well as HC2 – centers for single-phase and two-phase ceramics is a direct confirmation of the inhibition of structural degradation mechanisms in two-phase ceramics.

The aim of this study is to determine the differences in the damaged layer degradation kinetics in two-phase lithium-containing ceramics based on Li2ZrO3 and Li4SiO4 compounds in the case of irradiation with protons and helium ions, simulating the gas swelling and blistering processes, as well as the accumulation of radiolysis products in the damaged layer. During the conducted studies it was established that in the case of proton irradiation, the dominant role at fluences of 1015–1017 cm−2 is played by oxygen vacancies, the change in the concentration of which upon reaching critical values causes a decrease in the thermophysical properties, and disordering of the damaged layer. In this case, the accumulation of radiolysis products in the form of HC2 – and Zr3+ -defects in the structure of the damaged layer is observed at fluences of 5 × 1017 cm−2, while when irradiated with He2+ ions, the formation of these types of HC2 – and Zr3+ -defects is observed at a fluence of 1017 cm−2. Comparison of the concentration dependences of defects in the damaged layer on the atomic displacement value under irradiation with protons and He2+ ions revealed that the formation of oxygen vacancies under irradiation with He2+ ions is more intense than in the case of irradiation with protons, which in turn results in more pronounced processes of accumulation of radiolysis products in the case of high-dose irradiation.

The study investigates alterations in the mechanical and thermophysical properties of ceramics composed of xLi2ZrO3–(1−x)Li4SiO4 as radiation damage accumulates, mainly linked to helium agglomeration in the surface layer. This research is motivated by the potential to develop lithium-containing ceramics characterized by exceptional strength properties and a resistance to the accumulation of radiation damage and ensuing deformation distortions in the near-surface layer. The study of the radiation damage accumulation processes in the near-surface layer was conducted through intense irradiation of ceramics using He2+ ions at a temperature of 700 °C, simulating conditions closely resembling operation conditions. Following this, a correlation between the accumulation of structural modifications (value of atomic displacements) and variations in strength and thermophysical characteristics was established. During the research, it was observed that two-component ceramics exhibit significantly greater resistance to external influences and damage accumulation related to radiation exposure compared to their single-component counterparts. Furthermore, the composition that provides the highest resistance to softening in two-component ceramics is an equal ratio of the components of 0.5Li2ZrO3–0.5Li4SiO4 ceramics.

The paper presents the results of studies of the resistance of lithium ceramics to helium swelling during its accumulation in the structure of the near-surface layer, and the identification of the three types of lithium ceramics most resistant to radiation degradation: Li4SiO4, Li2TiO3, and Li2ZrO3. The simulation of helium swelling under high-dose irradiation was carried out by irradiation with He2+ ions with fluences of 1 × 1016 ion/cm2–5 × 1017 ion/cm2, which allows for simulating the implanted helium accumulation with a high concentration in the damaged surface layer (about 500 nm thick). The samples were irradiated at a temperature of 1000 K, the choice of which was determined by the possibility of simulating radiation damage as close as possible to real operating conditions. Such accumulation can result in the formation of gas-filled bubbles. Through the application of X-ray phase analysis, indentation testing, and thermophysical parameter assessments, it was ascertained that among the three ceramic types, Li4SiO4 ceramics exhibit the highest resistance to helium-induced swelling. These ceramics experienced less significant alterations in their properties compared to the other two types. An analysis of the correlation between the structural and strength parameters of lithium-containing ceramics revealed that the most significant changes occur when the volumetric swelling of the crystal lattice becomes the dominant factor in structural alterations. This phenomenon is manifested as an accelerated degradation of strength characteristics, exceeding 10%. At the same time, analysis of these alterations in the stability of thermophysical parameters to the accumulation of structural distortions revealed that, regardless of the type of ceramics, the degradation of thermophysical properties is most pronounced under high-dose irradiation (above 1017 ion/cm2).

The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of long-term thermal exposure, accompanied by the processes of oxidation and softening. The relevance of this research consists of determining the influence of the phase composition of ceramics on the change in their strength and thermophysical parameters, on the basis of which, we can draw a conclusion about the optimal composition of composite ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant structural materials. During this study, the dynamics of the changes in the phase transformations of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by the thermal annealing of the samples, was established. According to the assessment of the phase transformations with variations in the ratio of the components, it was found that thermal annealing in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an orthorhombic Al2(SiO4)O phase and an elevation in its contribution at concentrations above 0.5 M, which causes a rise in the thermophysical parameters and resistance to high-temperature degradation. During the heat resistance tests, it was found that the formation of the composite ceramics with the Si3N4(SiO2)/Al2(SiO4)O/Al2O3 phase composition results in an increase in the stability of their strength properties when exposed to thermally induced oxidation, which has a negative impact on their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2(SiO4)O phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation resistance of strength properties by more than 4–7 times, in comparison with the softening data established for single-component ceramics.

This paper presents the results of the influence of variation of the synthesis conditions of CuBi/CuBi2O4 films with a change in the applied potential difference, as well as a change in electrolyte solutions (in the case of adding cobalt or nickel sulfates to the electrolyte solution) on changes in the phase composition, structural parameters and strength characteristics of films obtained using the electrochemical deposition method. During the experiments, it was found that, in the case of the addition of cobalt or nickel to the electrolyte solutions, the formation of films with a spinel-type tetragonal CuBi2O4 phase is observed. In this case, a growth in the applied potential difference leads to the substitution of copper with cobalt (nickel), which in turn leads to an increase in the structural ordering degree. It should be noted that, during the formation of CuBi/CuBi2O4 films from solution–electrolyte №1, the formation of the CuBi2O4 phase is observed only with an applied potential difference of 4.0 V, while the addition of cobalt or nickel sulfates to the electrolyte solution results in the formation of the tetragonal CuBi2O4 phase over the entire range of the applied potential difference (from 2.0 to 4.0 V). Studies have been carried out on the strength and tribological characteristics of synthesized films depending on the conditions of their production. It has been established that the addition of cobalt or nickel sulfates to electrolyte solutions leads to an increase in the strength of the resulting films from 20 to 80%, depending on the production conditions (with variations in the applied potential difference). During the studies, it was established that substitution of copper with cobalt or nickel in the composition of CuBi2O4 films results in a rise in the shielding efficiency of low-energy gamma radiation by 3.0–4.0 times in comparison with copper films, and 1.5–2.0 times for high-energy gamma rays, in which case the decrease in efficiency is due to differences in the mechanisms of interaction of gamma quanta, as well as the occurrence of secondary radiation as a result of the formation of electron–positron pairs and the Compton effect.

Ceramics based on zirconium dioxide are very important compounds for dental, implant, and structural material applications. Despite the fact that tetragonally stabilized YSZ has been well studied, the search for new compositions of zirconia-based ceramics is still in progress. The ZrO2-CeO2 system is one of the alternatives for YSZ materials, but there is conflicting experimental data on its phase composition and mechanical properties depending on the ratio of components. In this study, we investigated the phase composition, and microstructural, mechanical, and physical properties of (1 − x)∙ZrO2-x∙CeO2 (step of x = 0.05) ceramics obtained by the solid-state sintering process from micron-sized powders. For the characterization of samples, XRD, Raman spectroscopy, SEM, the Vickers Microhardness Test, and dielectric spectroscopy were implemented. The results showed that by varying the CeO2 concentration, it is possible to synthesize stable tetragonal ZrO2 at room temperature with a high microhardness HV0.05 value of ~1500, low porosity (~2.5%), and a high dielectric constant of 36. The pronounced combined effect of tetragonal phase formation, densification, and grain size reduction on the mechanical and dielectric properties of the experimental samples was investigated. Refined experimental data make it possible to synthesize high-quality zirconia–ceria ceramics for use as refractories, dispersed nuclear fuel, or solid oxide fuel cells.

The article outlines findings from a comparative analysis of the effectiveness of doping CeO2 ceramics with a stabilizing additive Y2O3 on alterations in the strength and thermophysical parameters of ceramics under high-temperature irradiation with heavy ions comparable in energy to fission fragments of nuclear fuel, which allows, during high-temperature irradiation, to simulate radiation damage that is as similar as possible to the fission processes of nuclear fuel. During the studies, it was found that the addition of a stabilizing additive Y2O3 to the composition of CeO2 ceramics in the case of high-temperature irradiation causes an increase in stability to swelling and softening because of a decrease in the thermal expansion of the crystal lattice by 3–8 times in comparison with unstabilized CeO2 ceramics. It has been determined that the addition of a stabilizing additive Y2O3 leads not only to a rise in the resistance of the crystal structure to deformation distortions and swelling, but also to a decrease in the effect of thermal expansion of the crystal structure, which has an adverse effect on the structural ordering of CeO2 ceramics exposed to irradiation at high temperatures.

The aim of this work is to study the hydrogenation processes in lithium-containing ceramics under high-temperature irradiation. Irradiation was carried out with protons with an energy of 1 MeV and fluences of 1015–1017 ion/cm2 at irradiation temperatures of 300–1000 K. The choice of irradiation conditions is due to the possibility of simulation of the radiation damage accumulation processes in the near-surface layer of Li2TiO3 ceramics, as well as establishing the dependences of changes in structural parameters during temperature heating of samples during irradiation. It has been established that at irradiation fluences of 1015–1016 ion/cm2, the formation of dislocation defects is observed, the density of which has a pronounced dependence on the irradiation temperature. At irradiation fluence above 5 × 1016 ion/cm2, an increase in the crystal structure deformation is observed, due to swelling processes as a result of implanted hydrogen accumulation in the near-surface layer structure. At the same time, an increase in the irradiation temperature leads to a decrease in the swelling value, which is due to the accelerated migration of implanted hydrogen in the near-surface layer and its release through the existing pores. Results of mechanical tests showed that the swelling of the crystal structure and its deformation leads to embrittlement and a partial decrease in the strength of the near-surface layer. The obtained research results will further allow us to evaluate the resistance of lithium ceramics to the processes of hydrogenation and destruction as a result of the formation of gas-filled cavities in the structure of the near-surface layer.

In this work, the structural, electrical, and mechanical properties and phase composition of high-content cubic zirconium oxide ceramics stabilized with Ca were investigated. The novelty of this work lies in evaluating the potential use of porous ceramics obtained using calcium carbonate as a matrix for dispersed nuclear fuel. Experimental samples were prepared using solid-phase synthesis through sintering in air at 1500 °C. The X-ray diffraction method and Raman spectroscopy showed that the fraction of the cubic zirconium oxide ZrO2-c phase gradually increased as the mass concentration changed from Cw = 0.00 to Cw = 0.15, and the CaZrO3 phase was present at concentrations of Cw = 0.20 and Cw = 0.25. When the phase composition was altered, significant changes occurred in the internal microstructure of the ceramics due to the processes of grain sintering and pore formation. Quantitative XRD analysis demonstrated the incorporation of Ca into the cubic structure of the ZrO2-c polymorph. Dielectric spectroscopy at low frequencies revealed that the synthesized ceramics had a dielectric constant of 16.8–22 with a low dielectric loss of ~ 0.005. The microhardness value at a load of 200 kgf (HV0.2) of the obtained samples varied between 5 and 12 GPa and depended on the internal microstructure and phase composition. The obtained results clearly indicate that the mechanical and electrical properties and phase composition of synthesized ceramics make them suitable as a matrix for dispersed nuclear fuels.

This research investigated how changes in the composition of Nb–Ti–V–Zr-based alloys affect their resistance to radiation damage and the preservation of strength characteristics when exposed to the heavy ions Kr15+ and Xe23+. These heavy ions simulate the impact of nuclear fuel fission fragments on the material. The primary objective of this study was to explore how variations in alloy components influence radiation resistance and the retention of alloy strength properties. Accumulation of radiation defects can potentially lead to embrittlement and a decrease in resistance to external factors during operation. An analysis of the X-ray diffraction data obtained from the initial alloy samples, in relation to the variations in the number of components, revealed that an increase in the number of components leads to the formation of a denser crystal structure. Additionally, this resulted in the emergence of a dislocation strengthening factor associated with changes in crystallite size. Concurrently, when assessing changes in the strength characteristics of the irradiated alloys, it was observed that the NbTiV and NbTiVZr alloys demonstrated the highest resistance to strength property degradation, specifically a 2.5- to 5-fold increase in resistance against a significant decrease in hardness. It was confirmed that the significant factor contributing towards the enhancement and preservation of the structural and strength properties is the dislocation strengthening mechanism. An increase in dislocation strengthening effectively enhances resistance against destructive embrittlement, particularly when exposed to high-dose irradiation.

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.

This work is dedicated to the study of the properties of perovskite ceramics based on lanthanum–strontium ferrite, and to the evaluation of their resistance to long-term thermal aging. As a method for obtaining perovskite ceramics, the method of solid-phase mechanochemical grinding and consequent thermal annealing of the resulting mixtures was chosen. The novelty of the study consists in the assessment of the phase transformation dynamics in lanthanum–strontium ferrite-based ceramics in relation to the annealing temperature, alongside the study of the effect of the phase composition of ceramics on the resistance to high-temperature aging, which is characteristic of the operating modes of these ceramics as materials for solid oxide fuel cells. To study the properties, the methods of scanning electron microscopy, energy dispersive analysis, and scanning electron microscopy were applied. Pursuant to the outcome of elemental analysis, it was established that no impurity inclusions appear in the ceramic structure during the synthesis, and a growth in the annealing temperature results into a decline in the grain size and a growth in their density. During the analysis of the acquired X-ray diffraction patterns, it was found that a growth in the annealing temperature above 500 °C results in phase transformations of the LaFeO3/SrFe2O4 → La0.3Sr0.7FeO3/LaSr2FeO8/La3FeO6 type, followed by structural ordering and a decline in deformation distortions with a growth in the annealing temperature. An analysis of the conductive properties of ceramics has established that the dominance of the La0.3Sr0.7FeO3 phase in the structure results in a growth in conductivity and a decline in resistance. Life tests for degradation resistance have shown that for three-phase ceramics, the rate of degradation and amorphization is significantly lower than for two-phase ceramics.

The purpose of this paper was to study the kinetics of accumulation of radiation damage in the near-surface layer of a high-entropy NbTiVZr alloy upon irradiation with heavy Kr15+ ions and fluences of 1010–1015 ion/cm2. According to the data of X-ray diffraction analysis, it was found that irradiation with heavy ions lead to structural changes associated with the accumulation of deformation distortions and stresses. In this case, the nature of deformation distortions was associated with tensile distortions of the crystal lattice and swelling of the near-surface layer. An analysis of the strength properties of the irradiated samples showed that the accumulation of deformation distortions in the near-surface layer lead to a decrease in the resistance to cracking and destruction of the near-surface layer. In this case, the main changes occurred at fluences above 1013 ion/cm2, which are characterized by an excess of the threshold for overlapping defective regions that appear along the trajectory of incident ions. Tribological tests showed that an increase in defective inclusions in the structure of the near-surface layer lead to an increase in friction and a decrease in crack resistance.

The purpose of this work is to study the effect of lanthanum (La) concentration on the phase formation, conductivity, and thermophysical properties of perovskite-like strontium ferrite ceramics. At the same time, the key difference from similar studies is the study of the possibility of obtaining two-phase composite ceramics, the presence of various phases in which will lead to a change in the structural, strength, and conductive properties. To obtain two-phase composite ceramics by mechanochemical solid-phase synthesis, the method of the component molar ratio variation was used, which, when mixed, makes it possible to obtain a different ratio of elements and, as a result, to vary the phase composition of the ceramics. Scanning electron microscopy, X-ray phase analysis, and impedance spectroscopy were used as research methods, the combination of which made it possible to comprehensively study the properties of the synthesized ceramics. Analysis of phase changes depending on lanthanum concentration change can be written as follows: (La0.3Sr0.7)2FeO4/LaSr2Fe3O8 → (La0.3Sr0.7)2FeO4/LaSr2Fe3O8/Sr2Fe2O5 → (La0.3Sr0.7)2FeO4/Sr2Fe2O5. Results of impedance spectroscopy showed that with an increase in lanthanum concentration from 0.10 to 0.25 mol in the synthesized ceramics, the value of the dielectric permittivity increases significantly from 40.72 to 231.69, the dielectric loss tangent increases from 1.07 to 1.29 at a frequency of 10,000 Hz, and electrical resistivity decreases from 1.29 × 108 to 2.37 × 107 Ω∙cm.

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 (Fe3−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.

This article is devoted to the study of the mechanical and strength properties of Y2O3-doped ZrO2–CeO2 composite ceramics. The choice of these ceramics is due to their prospects in the field of nuclear energy, structural materials and as the basis for materials of dispersed nuclear fuel inert matrices. The choice as objects for research is due to their physicochemical, insulating and strength properties, the combination of which makes it possible to create one of the promising types of composite ceramics with high resistance to external influences, high mechanical pressures and crack resistance. The method of mechanochemical synthesis followed by thermal annealing of the samples at a temperature of 1500 °C; was used as a preparation method; to study the effect of Y22O3 doping, scanning electron microscopy methods were used to determine morphological features. The X-ray diffraction method was applied to determine the structural features and phase composition. The mechanical methods of microindentation and single compression for determination were applied to determine the strength characteristics. During the tests, it was found that the most resistant materials to external mechanical influences, and thermal heating for a long time of testing, are ceramics, in which the CeZrO4 phase dominates. At the same time, the strengthening of ceramics and an increase in crack resistance is due to a change in the phase composition and to a decrease in the grain size, leading to the formation of a large dislocation density, and, consequently, the appearance of the dislocation strengthening effect. The relevance and novelty of this study lies in obtaining new types of ceramic materials for inert matrices of nuclear fuel, studying their morphological, structural, strength and thermophysical properties, as well as assessing their resistance to external influences during prolonged thermal heating. The results obtained can later be used as fundamental knowledge in assessing the prospects for the use of oxide ceramics as nuclear materials.

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.

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.

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.

Lithium-containing ceramics have several great potential uses for tritium production, as well as its accumulation. However, their use is limited due to their poor resistance to external influences, mechanical pressure, and temperature changes. In this work, initial nanostructured ceramic powders were obtained using the sol-gel method, by mixing TiO2 and LiClO4·3H2O with the subsequent addition of NiO nanoparticles to the reaction mixture; these powders were subsequently subjected to thermal annealing at a temperature of 1000 °C for 10 h. Thermal annealing was used to initiate the phase transformation processes, and to remove structural distortions resulting from synthesis. During the study, it was found that the addition of NiO nanoparticles leads to the formation of solid solutions by a type of Li0.94Ni1.04Ti2.67O7 substitution, which leads to an increase in the crystallinity and structural ordering degree. At the same time, the grain sizes of the synthesized ceramics change their shape from rhomboid to spherical. During analysis of the strength characteristics, it was found that the formation of Li0.94Ni1.04Ti2.67O7 in the structure leads to an increase in hardness and crack resistance; this change is associated with dislocation. When analyzing changes in resistance to cracking, it was found that, during the formation of the Li0.94Ni1.04Ti2.67O7 phase in the structure and the subsequent displacement of the Li2TiO3 phase from the composition, the crack resistance increases by 15% and 37%, respectively, which indicates an increase in the resistance of ceramics to cracking and the formation of microcracks under external influences. This hardening and the reinforcing effect are associated with the replacement of lithium ions by nickel ions in the crystal lattice structure.

The aim of this work is to study the properties of nanostructured (1 − x)ZrO2 − xCeO2 composite ceramics, depending on the content of oxide components, as well as to establish the relationship between the phase composition of ceramics and strength properties. The choice of (1− x)ZrO2 − xCeO2 composite ceramics as objects of study is due to the great prospects for using them as the basis for inert matrix materials for nuclear dispersed fuel, which can replace traditional uranium fuel in high-temperature nuclear reactors. Using X-ray diffraction, it was found that the variation of the oxide components leads to phase transformations of the Monoclinic-ZrO2 → Monoclinic − Zr0.98Ce0.02O2/Tetragonal − ZrO2 → Tetragonal − Zr0.85Ce0.15O2 → Tetragonal − ZrCeO4/Ce0.1Zr0.9O2 type. As a result of mechanical tests, it was found that the formation of tetragonal phases in the structure of ceramics leads to strengthening of ceramics and an increase in crack resistance, which is due not only to an increase in the crystallinity degree, but also to the effect of dislocation hardening associated with a decrease in grain size. It has been established that a change in the phase composition due to phase transformations and displacement of the ZrO2 phase from the ceramic structure with its transformation into the phase of partial replacement of Zr0.85Ce0.15O2 or Ce0.1Zr0.9O2 leads to the strengthening of ceramics by more than 3.5–4 times. The results of resistance to crack formation under single compression showed that the formation of the ZrCeO4 phase in the structure of ceramics leads to an increase in the resistance of ceramics to cracking by more than 2.5 times.

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.

The work is devoted to the study of technology that can be used to obtain lithium-containing ceramics of the Li2+4xZr4−xO3 type using the method of solid-phase synthesis combined with thermal annealing at a temperature of 1500 °C. A distinctive feature of this work is the preparation of pure Li2ZrO3 ceramics with a high structural ordering degree (more than 88%) and density (95–97% of the theoretical density). During the study, it was found that a change in the content of initial components for synthesis does not lead to the formation of new phase inclusions; however, an increase in the LiClO4·3H2O and ZrO2 components leads to changes in the size of crystallites and dislocation density, which lead to the strengthening of ceramics to external mechanical influences. The results of the measurements of thermophysical characteristics made it possible to establish that the compaction of ceramics and a decrease in porosity lead to an increase in the thermal conductivity coefficient of 3–7%.

The key aim of this paper is to study the presence effect of LiO impurity phases in Li2ZrO3 ceramics on the resistance to helium swelling and structural degradation during implanted helium accumulation in the near-surface layer structure. The hypothesis put forward is based on a number of scientific papers, in which it was reported that the presence of two or more phases in lithium-containing ceramics led to a decrease in the rate of radiation damage and gas swelling due to the presence of additional interfacial boundaries that prevent the point defect accumulation. As a result of the evaluation of the crystal structure deformation, it was found that the presence of the LiO impurity phase in the structure of Li2ZrO3 ceramics led to a threefold decrease in the deformation of the crystal lattice due to helium swelling at doses of 5 × 1017–5 × 1018 ion/cm2. At the same time, the nature of the crystal lattice deformation for different ceramic types is different: in the case of Li2ZrO3 ceramics, an anisotropic distortion of the crystal structure is observed, in the case of Li2ZrO3/LiO ceramics, the crystal lattice deformation has an isotropic nature.

In this work, using a mechanochemical solid-phase synthesis method, ZrO2—CeO2 ceramics doped with yttrium were obtained, which have great prospects for use as a basis for dispersed nuclear fuel materials or inert nuclear fuel matrices. The purpose of this work was to study the formation of the ZrO2—CeO2 phase composition, depending on the concentration of yttrium dopant, as well as to study their structural and strength properties. The relevance of this study is in obtaining new data on the properties of composite ceramics based on oxides having a cermet structure, as well as the effect of doping with yttrium on increasing the resistance of ceramics to deformation and thermal properties. During the studies, the dynamics of the phase transformations depending on the concentration of the dopant, as well as changes in the structural characteristics and dislocation density, were established. It was found that at a dopant concentration of 0.25 mol, the main phase in the structure was Ce3ZrO8–triclinic P1 (1), the formation of which led to an increase in the mechanical and strength properties of the ceramics as well as a 1.5-fold increase in the thermal conductivity coefficient.

This paper considers the possibilities of increasing radiation resistance to helium swelling of beryllium oxide ceramics due to preliminary irradiation with heavy ions. Interest in this topic is due to the possibility of using these ceramics as materials for inert matrices of nuclear fuel and structural materials reflectors of high-temperature reactors. The samples studied were irradiated in two stages, namely irradiation with heavy Ar8+, Kr15+, and Xe22+ ions with a fluence of 1012 ion/cm2 and subsequent irradiation with He2+ ions with a fluence of 5x1017 ion/cm2. The main parameters used to compare and determine radiation modification efficiency were the crystal-structure swelling degree, a decrease in the hardness, and wear resistance of ceramics after irradiation with He2+ ions. During the studies carried out, it was found that preliminary irradiation with heavy Ar8+, Kr15+, and Xe22+ ions leads to a significant increase in radiation swelling resistance, as well as to an increase in crack resistance and wear resistance.

The paper is devoted to the study of radiation-induced damage kinetics in beryllium oxide ceramics under irradiation with low-energy helium ions with fluences of 1015–1018 ion/cm2. It was revealed that at irradiation fluences above 1017 ion/cm2, a decrease in radiation-induced damage formation and accumulation rate is observed, which indicates the saturation effect. At the same time, the main mechanisms of structural changes caused by irradiation at these fluences are amorphization processes and dislocation density increase, while at fluences of 1015–1016 ion/cm2, the main mechanisms of structural changes are due to the reorientation of crystallites and a change in texture, with a small contribution of crystal lattice distorting factors. It was discovered that the radiation-induced damage accumulation as well as an implanted helium concentration increase leads to the surface layer destruction, which is expressed in the ceramic surface hardness and wear resistance deterioration. It was determined that with irradiation fluences of 1015–1016 ion/cm2, the decrease in thermal conductivity is minimal and is within the measurement error, while an increase in the irradiation fluence above 1017 ion/cm2 leads to an increase in heat losses by more than 10%.

The article is dedicated to the study of the phase formation processes in Li2ZrO3 ceramics obtained by the method of solid phase synthesis. Interest in these types of ceramics is due to their great potential for use as blanket materials in thermonuclear reactors, as well as being one of the candidates for tritium breeder materials. Analysis of the morphological features of the synthesized ceramics depending on the annealing temperature showed that the average grain size is 90–110 nm; meanwhile the degree of homogeneity is more than 90% according to electronic image data processing results. The temperature dependences of changes in the structural and conducting characteristics, as well as the phase transformation dynamics, have been established. It has been determined that a change in the phase composition by displacing the impurity LiO and ZrO2 phases results in the compaction of ceramics, as well as a decrease in their porosity. These structural changes are due to the displacement of LiO and ZrO2 impurity phases from the ceramic structure and their transformation into the Li2ZrO3 phase. During research, the following phase transformations that directly depend on the annealing temperature were established: LiO/ZrO2/Li2ZrO3 → LiO/Li2ZrO3 → Li2ZrO3. During analysis of the obtained current-voltage characteristics, depending on the annealing temperature, it was discovered that the formation of the Li2ZrO3 ordered phase in the structure results in a rise in resistance by three orders of magnitude, which indicates the dielectric nature of the ceramics.

The aim of this work was to study resistance to helium accumulation processes in the structure of the surface layer of lithium-containing ceramics and the subsequent destruction and embrittlement processes, depending on radiation fluence. The objects of study were Li2TiO3-type ceramics obtained by thermal sintering. The fluence dependency of changes in the structural and strength properties of ceramics was determined to be in the range from 1018 to 1022 ion/m2, which corresponded to the concentration of implanted helium from 0.01% to 0.8–1 at.%. Irradiation was carried out at a temperature of 700 °C, which made it possible to simulate the processes of radiation damage that were closest to the real conditions in the reactor core. During the studies carried out, it was found that, at irradiation fluences of 1018–1020 ion/m2, the formation of point radiation defects was equaled by the process of thermal annealing of defects, as a result of which the concentration of defects and their effect on the change in the structural and strength properties of ceramics were insignificant. An increase in the concentration of implanted helium in the structure of the surface layer to above 0.5 at.% led to the dominance of radiation damage processes over the annealing of defects and the formation of gas-filled cavities, which negatively affects the strength of ceramics.

Today, one of the most promising materials for a wide range of practical applications is lithium-containing ceramics based on Li2TiO3. At the same time, despite the high potential of their practical application, a number of questions remains related to the methods of their preparation, as well as the formation of a stable crystal structure and a pure-phase composition. To solve these issues, this paper proposes a method for obtaining stable Li2TiO3 ceramics, which is based on solid-phase synthesis combined with the high-temperature sintering of ceramics. During the studies carried out using X-ray diffraction methods, temperature dependences of phase transformations of the TiO2/Li2Ti6O13 → Li2TiO3 type were determined, according to which, at temperatures above 800 °C, the formation of a stable Li2TiO3 phase characterized by a high structural ordering degree of 89–91% is observed. The dependence of changes in structural, optical and ferroelectric characteristics on the conditions of synthesis and phase composition of ceramics was also determined.

The paper presents the results of changes in the structural characteristics, and the degree of texturing of FeNi nanostructures close in composition to permalloy compounds as a result of directed modification by gamma radiation with an energy of 1.35 MeV and doses from 100 to 500 kGy. The choices of energy and radiation doses were due to the need to modify the structural properties, which consisted of annealing the point defects that occurred during the synthesis along the entire length of the nanotubes. The initial FeNi nanostructures were polycrystalline nanotubes of anisotropic crystallite orientation, obtained by electrochemical deposition. The study found that exposure to gamma rays led to fewer defects in the structure, and reorientation of crystallites, and at doses above 300 kGy, the presence of one selected texture direction (111) in the structure. During tests of the corrosion resistance of synthesized and modified nanostructures in a PBS solution at various temperatures, it was found that exposure to gamma rays led to a significant decrease in the rate of degradation of nanotubes and an increase in the potential life of up to 20 days. It was established that at the first stage of testing, the degradation of nanostructures is accompanied by the formation of oxide inclusions, which subsequently lead to the formation of pitting corrosion and subsequent partial or complete destruction of the nanostructures. It is shown that gamma radiation is promising not only for targeted modification of nanostructures and increasing resistance to degradation, but also for increasing the rate of catalytic reactions of the PNA-PPD type.

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.