Alexander Fedorets

The paper presents new experimental data on the influence of post-annealing temperature conditions on the microstructure and optical properties of Ce:GGAG (Gd3Al2Ga3O12 doped with Ce3+) ceramics obtained by spark plasma sintering (SPS). Post‐annealing was carried out in an oxygen‐containing atmosphere in the temperature range of 1200–1350 °C for 5 h. Microstructural analysis revealed thermally activated grain growth from 3.5 to 11.5 μm with increasing temperature. At 1300 °C, the onset of secondary recrystallization was observed, as evidenced by the deviation of the grain size distribution from the log‐normal law, which leads to the formation of a coarse‐grained and less homogeneous structure at 1350 °C. Spectroscopic studies demonstrated that annealing at 1200 °C provides high luminescence characteristics, including maximum emission intensity and an average decay time of 52.4 ns. In contrast, increasing the annealing temperature (1250–1350 °C) results in deteriorated optical properties, manifested as a decrease in luminescence intensity and a reduction of the decay time to 44.4 ns. It has been proven that these effects are associated with enhanced light scattering at coarsened pores and an increased contribution of non‐radiative recombination at grain boundaries. The obtained results establish a clear relationship between structure and properties, demonstrating that post‐annealing at 1200 °C for 5 h is the optimal regime for Ce:GGAG ceramics synthesized by SPS, ensuring high optical transparency and efficient scintillation characteristics.

This comparative study investigates binder-free binary WC-TiC and ternary WC-TiC-TaC carbide ceramics as alternatives to cobalt-bonded hard materials. Equimolar compositions were processed via high-energy ball milling (HEBM) and consolidated by spark plasma sintering (SPS) at 1700–2100 °C. X-ray diffraction analysis (XRD) revealed fundamentally different homogenization kinetics: the ternary system achieved a complete single-phase structure at 2000 °C, 100 °C earlier than the binary system. This acceleration correlates with finer initial particle size (2–5 μm vs. 3–10 μm) and near-stoichiometric TaC, facilitating interdiffusion. Lattice parameter evolution confirmed the formation of (W,Ti)C and (W,Ti,Ta)C substitutional solid solutions. Mechanical characterization showed contrasting behaviors: binary WC-TiC exhibits maximum hardness at 1900 °C (1793 HV30, fracture toughness 5.07 MPa·m^1/2), while ternary WC-TiC-TaC peaks at 1700–1800 °C (1947–1782 HV30) with higher toughness (max 5.42 MPa·m^1/2). Optimal processing windows with acceptable property uniformity are 1800–1900 °C (binary) and 1700–1900 °C (ternary). The binary system offers superior toughness and stability; the ternary system enables faster processing and higher initial hardness, defining distinct application domains.

In this study, medium- and high-entropy carbide systems with compositions WC-TiC-TaC-HfC and WC-TiC-TaC-HfC-ZrC were successfully synthesized via a combination of mechanical activation (using high-energy ball milling, HEBM) and spark plasma sintering (SPS) at 1900 °C. Investigation of the SPS consolidation kinetics revealed that both systems undergo single-stage active densification via a solid-state sintering mechanism within the temperature range of 1316–1825 °C. The introduction of ZrC into the five-component system led to a 22% decrease in the maximum shrinkage rate (from 0.9 to 0.7 mm·min⁻¹), which is attributed to the manifestation of a sluggish diffusion effect, characteristic of high-entropy systems. X-ray diffraction analysis of the consolidated samples confirmed the formation of predominantly single-phase high-entropy solid solutions (W-Ti-Ta-Hf)C and (W-Ti-Ta-Hf-Zr)C with a NaCl-type cubic structure (space group Fm-3m) and lattice parameters of 4.4101 Å and 4.4604 Å, respectively. Energy-dispersive X-ray spectroscopy revealed a near-equimolar distribution of metallic components with deviations not exceeding ±1.9 at. %. The addition of ZrC increased the average crystallite size by 84.3% (from 83.6 to 153.1 nm). Both systems achieved comparable relative densities of ~91.75%; however, they exhibited differences in hardness distribution: the four-component system is characterized by a higher average microhardness (1860 HV), while the five-component system exhibits a higher macrohardness HV30 (2008.1). The established correlations between composition, phase formation, microstructure, and properties provide a fundamental basis for the targeted design of high-entropy carbide ceramics with tailored characteristics for high-temperature applications.

The article examines the synthesis and electrophysical properties of spinel ferrite ZnFe₂O₄, produced using the sol–gel method with a solid-state finishing process; as well as through classical ceramic technology with mechanochemical activation. The study includes a detailed analysis of the phase composition and crystalline structure using X-ray diffraction; infrared spectroscopy; mass spectrometry; and thermogravimetric and differential thermal analyses. These methods help identify thermal effects and the stages of synthesis. Impedance spectroscopy is used to investigate the electrophysical properties, revealing a significant influence of firing temperature on electrical ionic conductivity. The results show that the electrophysical properties differ based on the synthesis conditions and methods. This suggests potential applications for ZnFe₂O₄ as a cathode material in metal-ion batteries. The work highlights the importance of optimizing synthesis conditions to achieve high-performance characteristics in electrode materials.

This article presents the results of a study of ceramics associated with the Valdivia and San Pedro complexes at the Real Alto site, southwestern Ecuador. The test sample, studied in 2022, includes fragments of vessels from two morphological and functional groups, relating to the first two phases of the Valdivia culture (bowls and pots) and those representing the San Pedro complex (vessels with necks and a bowl). A comparative analysis was based on identified technological indicators marking various stages of pottery manufacture. Certain differences are seen in the composition of paste and in the hand-shaping of the vessels. Significant differences were revealed in surface treatment and decoration. This is evidenced by the use of colored and plain coating, high-quality solid or matte striped polishing, and complexity of decoration. Distinctive features of firing include the use of different kilns and various atmospheric modes. Parallels include broadly similar firing temperatures. The technological difference between the two morphological and functional groups of the Valdivia complex is that bowls were manufactured with more complex and labor-consuming techniques, whereas pots are technologically somewhat similar to those from San Pedro. Radiocarbon dates (4640–4450 BP) suggest that the two traditions coexisted. Differences may reflect their cultural distinctness.

In this study, we explored the atomic structure and orderliness of amorphous alloys through advanced electron microscopy and analytical techniques. Amorphous alloys, characterized by disordered atomic structures, exhibit promising applications in technology. The research addresses a crucial knowledge gap by investigating cluster distribution, particle arrangement, and orderliness within the amorphous matrix. High-resolution electron microscopy (HREM) images are analyzed using diverse algorithms and software tools. The study establishes a correlation between angles approaching 180 degrees and increased orderliness within clusters, highlighting the reliability of angle distribution analysis. Robust indicators, including Div (SP(B/V)) and Div (Mu(B/V)) metrics, assess and compare amorphous alloy samples. Kullback–Leibler (K-L) divergence indicates the significance of cluster ordering, validated by the S-K test. Radial Distribution Function (RDF) analysis uncovers local short-range order, deepening understanding despite limited orderliness discernment. These findings not only enhance our understanding of metallic glasses or amorphous alloys but also offer opportunities for tailored design and improved applications across various technological domains.

This article unveils EMICA, a Python-based software tool revolutionizing electron microscopy image processing for amorphous alloys. EMICA addresses the unique challenges posed by these materials, which lack long-range order, by providing specialized capabilities for cluster analysis and spatial pattern recognition. This research explored software tool development and application through illustrative examples, answering the key question of how they enhance amorphous alloy analysis. By integrating advanced image processing techniques and algorithms, EMICA uncovers hidden patterns, offering quantitative insights into cluster distributions. The key message emphasizes the application’s transformative impact on material science research, providing a specialized solution for electron microscopy image analysis in the amorphous alloy domain. Our key findings, presented through real-world examples and case studies, attest to the efficacy of the software in revealing nuanced details of amorphous alloy structures. From identifying subtle variations in atomic configurations to quantifying cluster distributions, EMICA represents a significant leap forward in the field of advanced electron microscopy image processing, contributing significantly to the advancement of this domain.

В статье представлены результаты изучения керамики культуры вальдивия и комплекса Сан-Педро с археологического памятника Реаль-Альто (Юго-Западный Эквадор). Исследованная в 2022 г. тестовая коллекция включает фрагменты сосудов двух морфолого-функциональных групп, относящихся к первым двум фазам культуры вальдивия (чаши и горшковидные сосуды), и керамики Сан-Педро (сосуды с горловиной и чаша). Сравнительный анализ проводился на основе выявленных технико-технологических признаков, соответствующих определенным стадиям производства посуды. Некоторые различия прослежены в составе пластичного сырья для формовочных масс и в технологии формовки изделий. Существенная разница выявлена в технологии обработки поверхности и орнаментации керамических сосудов. Это проявляется в использовании окрашенных или неокрашенных покрытий, применении качественного сплошного либо матового полосчатого лощения, нанесении разного по уровню сложности орнамента. Определены как отличительные особенности обжига посуды (вероятное применение разных теплотехнических устройств, различия в атмосферных режимах), так и черты сходства (приблизительно одинаковые температурные режимы). Выявлены различия технологического характера между двумя морфолого-функциональными группами керамики вальдивии: представленная чашами демонстрирует признаки использования более сложных и трудоемких приемов; группа горшковидных сосудов по технологическому уровню имеет определенное сходство с керамикой Сан-Педро. Полученные радиоуглеродные даты (4 640-4 450 л.н.) позволяют говорить об одновременности существования двух гончарных традиций. Различия технико-технологических характеристик керамики, вероятно, отражают культурную специфику носителей этих традиций.

A novel solid-phase synthetic approach was developed to produce a mineral-like composite ceramic based on strontium titanate (SrTiO₃) and yttrium titanate (Y₂Ti₂O₇) matrices for immobilizing radionuclides such as ⁹⁰Sr and its daughter product ⁹⁰Y, as well as lanthanides and actinides, via reactive spark plasma sintering technology (SPS-RS). Using XRD, SEM, and EDS analyses, the sintering kinetics of the initial mixed oxide reactants of composition Y_xSr_1–1.5xTiO₃ (x = 0.2, 0.4, 0.6 and 1) and structure-phase changes in the ceramics under SPS-RS conditions were investigated as a function of Y³⁺ content. In addition, a detailed study of phase transformation kinetics over time as a function of the heating temperature of the initial components (SrCO₃, TiO₂, and Y₂O₃) was conducted via in situ synchrotron XRD heating experiments. The composite ceramic achieved relatively high physicomechanical properties, including relative density between 4.92–4.64 g/cm³, Vickers microhardness of 500–800 HV, and compressive strength ranging from 95.5–272.4 MPa. An evaluation of hydrolytic stability and leaching rates of Sr²⁺ and Y³⁺ from the matrices was performed, demonstrating rates did not exceed 10⁻⁵–10⁻⁶ g·cm⁻²·day⁻¹ in compliance with GOST R 50926-96 and ANSI/ANS 16.1 standards. The leaching mechanism of these components was studied, including the calculation of solution penetration depth in the ceramic bulk and ion diffusion coefficients in the solution. These findings show great promise for radioactive waste conditioning technologies and the manufacturing of radioisotope products.