bluuebunny/crossref_metadata_2025 huggingface dataset:
Ailelerin Tip 1 Diyabet Tanılı Çocuklarında Tamamlayıcı ve Alternatif Terapileri Kullanma Durumlarının, Kullanılan Yöntemlerin ve Metabolik Kontrole Etkisinin İncelenmesi
Authors: Yetim Perihan , Özgüven Öztornacı Beste , Ardahan Akgül Esra , Yıldırım Sarı Hatice , Dündar Bumin Nuri
Published: August 2024

Amaç: Bu çalışma, Tip 1 diyabetes mellitüs (DM) tanılı çocukların ailelerinin çocuklarının diyabet tedavisinde tamamlayıcı ve alternatif terapileri (TAT) kullanma durumlarının, kullanılan yöntemlerin ve metabolik kontrole etkisinin incelenmesi amacıyla planlanmıştır.

Gereç ve Yöntem: Nicel olarak tasarlanmış, tanımlayıcı ve kesitsel tipteki bu çalışma, Eylül 2023 ile Mart 2024 tarihleri arasında, İzmir ilindeki bir üniversite hastanesinin çocuk endokrinoloji kliniğinde tedavi gören Tip 1 DM tanılı 120 çocuğun ailesi ile gerçekleştirilmiştir. Verilerin toplanmasında; Kişisel Bilgi Formu ve Ailelerin Tip 1 DM Tanılı Çocuklarında TAT Kullanma Durumuyla İlgili Soru Formu kullanılmıştır. Araştırma verileri SPSS for Windows Version 26.00 bilgisayar programı ile işlenmiş ve analiz edilmiştir. Araştırmanın etik izinleri alınmıştır.

Bulgular: Çalışmaya katılan ailelerin %30’unun Tip1 DM tanılı çocuklarında TAT kullandığı belirlenmiştir. Ailelerin en çok tercih ettiği TAT yöntemi %30,6 ile kabuk tarçınlı su içirmektir. Annenin eğitim durumu, çocuğun diyabet takibini yapan kişinin kim olduğu ve çocuğun bir egzersiz programına düzenli olarak uyma durumu değişkenleri ailelerin TAT uygulama durumları üzerinde anlamlı olarak etkilidir (p
Papel do Mindful Eating e Comer Intuitivo na mudança do Comer emocional e obesidade: Uma revisão narrativa
Authors: Eduarda Santos Carregosa  , Medreiros Luana Santos , Karolaine de Almeida Lima  , Marcus Vinicius Santos do Nascimento  , Rodrigues Millena Angel Silva , Brenda Laise Anchieta dos Santos  , Fernanda Silva Franco  , Karina de Brito Santos Souza  , Josiane de França Vieira  , Vivian Lee Franco Barreto  , Karla Kristhiane Batista Barreto  , Steffany Almeida Santos
Published: August 2024

O comportamento alimentar é um dos fatores centrais subjacentes à obesidade, por isso, o objetivo da presente revisão de literatura é revisar a relação entre comer emocional e desenvolvimento de sobrepeso e obesidade, bem como o papel do mindful eating e comer intuitivo na mudança desse comportamento alimentar. Para a revisão bibliográfica foi realizada busca de documentos, artigos e livros nas bases de dados PubMed, Science Direct e SciELO e sites oficiais de órgãos públicos, no período de fevereiro a novembro de 2022. Constatou-se que o comer emocional é um comportamento alimentar disfuncional associado ao ganho de peso, maior IMC, sintomas depressivos e curta duração de sono. Programas convencionais de emagrecimento não lidam com o comer emocional. Mindful eating e comer intuitivo mostram-se como estratégias eficazes para atender as necessidades de comedores emocionais. Dessa forma, programas direcionados para perda de peso devem levar em consideração o comportamento alimentar individual e adotar abordagens comportamentais que ensinem habilidade de regulação emocional.
Biotecnología aplicada al diagnóstico y tratamiento de la osteoporosis. Avances en biofármacos, bioterapias y biomarcadores. Parte 2
Authors: Sterin Prync Aída Edith , Carlucci Adriana Mónica , Bentivegna Silvina , Fracalossi Martínez Ornella , Pedernera Santiago , Scibilia María Agustina , Tamburini Glas Florencia
Published: August 2024

Introducción: La osteoporosis constituye un problema sanitario tanto por su morbilidad y mortalidad como por los costos aparejados. Los avances provenientes de la biotecnología bioquímico - farmacéutica buscan aportar mejoras significativas tanto en el diagnóstico como en el tratamiento. Objetivos: Recopilar y revisar la bibliografía científica sobre los hallazgos relacionados con técnicas diagnósticas, biofármacos, bioterapias y biomarcadores de osteoporosis disponibles o en ensayos clínicos. Materiales y Métodos: Se efectuó una revisión de la literatura usando las palabras clave: osteoporosis, monoclonal antibodies, biopharmaceuticals, biotherapies, y biomarkers en Pubmed, Scielo, Lilacs BVS y Google Scholar. Se analizaron 82 trabajos en inglés o español, del período 2014 - 2019, relacionados con biofármacos, bioterapias o biomarcadores usados para osteoporosis. Resultados: Existen 3 biofármacos aprobados (teriparatide, denosumab y rosozumab) y uno (blosozumab) en fase 2 clínica. De las bioterapias, el uso de células madre mesenquimales resultó la más promisoria, aunque con limitaciones. También existen moléculas indicadoras de formación/resorción ósea como biomarcadores, y hay otras nuevas como microRNA. Conclusión: La biotecnología bioquímico - farmacéutica participa activamente de la búsqueda de nuevas y mejores alternativas para el diagnóstico, seguimiento y tratamiento de la osteoporosis.
Penguatan Moderasi Beragama dan Kearifan Lokal Melalui Manajemen Kurikulum Madrasah Ibtidaiyah
Authors: Sholihah Mar’atus , In'Ratnasari Khurin , Ratu Balqis Rizqiyah
Published: August 2024

Radikalisasi di zaman teknologi ini tidak hanya menyasar para mahasiswa,namun juga mulai dikembangkan lebih luas lagi ke usia anak-anak. Pendoktrinan radikalisasi di usia-usia ini semakin berbahaya, dikarenakan nilai-nilai radikalisme akan lebih kuat melekat dalam alam bawah sadar mereka. Radikalisasi di dunia anak dibuktikan dengan berbagai data dari berita yang muncul terkait penanaman nilai radikasime di lingkungan anak pada beberapa tahun belakangan. Portal berita seperti Tempo, ABC dan Kompas sama-sama menunjukkan kepada masyarakat Indonesia bahwa radikalisasi anak sudah dimulai di jenjang pendidikan usia dini, bahkan. Anak-anak diajarkan oleh gurunya sendiri tentang cerita-cerita perang di Israel dan Palestina, serta tidak adanya upacara bendera dan cerita-cerita tentang kebudayaan setempat. Oleh karena itu tujuan daripendampingan ini yaitu Memberikan penguatan moderasi beragama dan kearifan lokal melalui manajemen core curriculum di Lembaga Pendidikan,metode pengabdian yang digunakan menggunakan PAR ( (Participatory Action Research). Hasil dari dampingan yaitu Bentuk penguatan moderasi beragama dapat dituangkan kedalam menajemen kurkulum MI dengan mata pelajaran, muatan local maupun kebiasaan embiasaan  tersebut  menjadi  produk budaya    siswa    dan    dapat    dimanfaatkan    dan    diaplikasikan    dalam    kehidupan    bermasyarakat (pemberdayaan),  Implikasi penguatan moderasi beragama dan kearifan lokal agar siswa yang memiliki budaya berpikir moderat dala, pemikiran, tingkah laku, maupun kebiasaan dalam lingkungan masyarakat.
SPS of conductor–insulator system close to percolation threshold based on Si3N4–ZrN
Authors:   Institute for Problems in Materials Science NAS of Ukraine, Pokhylko Bohdan , Kolesnichenko Valerii , Ragulya Andrey
Published: August 2024

There is a difference in how conductive and insulating materials are heated during Spark Plasma Sintering (SPS) [1]. Conductive materials can be additionally heated by Joule heating, which may cause changes in shrinkage behaviour and structure evolution [2]–[3], and even thermal runaway [3]–[4]. It may be especially crucial for the conductor-insulator system which can drastically turn from insulator to conductor during SPS due to porosity reduction to a certain level called percolation threshold [5]. SPS of (Si3N4–30vZrN)–5vY2O3, SEM analysis of powders and sintered samples were carried out. To regulate the current density in the powder, combinations of die and powder were isolated from the current flow by applying an insulating coating (BN). A rapid rise in current indicators was observed when the die was isolated. It is assumed to be caused by the drop in powder resistivity after reaching the percolation threshold. In contrast, other isolation schemes with no applied isolation and isolation of both the powder and the die show nearly linear dependences. SPS with the isolated die appears to be more sensitive to the change in the powder conductivity due to concentrating most of the current in the powder instead of the die. The application of higher current density in the powder caused a lowering of the temperature at which shrinkage began up to 60 °C, and the shrinkage intensification at the final stage up to 2 times. The calculations of the resistance of the electric circuit of die and powder with different combinations of isolation of die and powder proved it. Displacement of punches, changes in height and conductivity of the powder sample were considered. The derived equation allows to evaluate the change in the powder conductivity during sintering. Therefore, SPS with the isolated die is quite a useful technique for the investigation of conductor-insulator systems with the percolation threshold.
Calcination of metatitanic acid to nano-TiO₂ anatase
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Baranovskyi Dmytro , Kolesnichenko Valerii , Ragulya Andrey
Published: August 2024

Titanium dioxide crystallizes in three polymorphic modifications: anatase, rutile, and brookite. While rutile is acknowledged as the most thermodynamically stable polymorph of TiO₂, anatase commands considerable attention owing to its photocatalytic prowess. This study is focused on the synthesis of anatase, which finds diverse applications. The chosen method involves the decomposition of metatitanic acid, esteemed for its procedural simplicity and reliability in titanium oxide synthesis. Titanium dioxide was synthesized utilizing a multi-section rotary furnace developed by the Frantsevich Institute for Problems of Materials Science, NASU. Adjustment parameters of the powder synthesis process were meticulously balanced to minimize the ingress of powder particles into the air without compromising final product quality. The dependency of TiO₂ crystallite size, ranging from 9 to 13.5 nm, on gas flow rate from 2.5 to 16.5 l/min was elucidated. Furthermore, varying the reactor's rotational speed from 4 to 18 rpm yielded crystallite sizes ranging from 13.8 to 9.8 nm. Characterization via X-ray diffraction, scanning electron microscopy, and ASAP confirmed the predominance of anatase (approximately 99%) in the obtained powder, with particle sizes ranging from 20 to 30 nm and a specific surface area of 80-100 m²/g. The final product underwent comprehensive characterization employing various analytical techniques, including Fourier transform infrared spectroscopy, transmission electron microscopy, and thermogravimetric analysis.Assessment of the microclimate and dust levels within the working environment was also conducted. The estimated concentration of titanium dioxide in the air during TiO₂ nanopowder production stages did not surpass the maximum permissible limit, and no exceedance of occupational exposure limits for titanium and OBRV of titanium dioxide nanoparticles was recorded. [1].
The process of degradation of ceramic balls made of Si3N4-based materials in hybrid bearings
Authors:   V. Bakul Institute for Superhard Materials, Kustovskyi Dmytro , Vasylchuk Oleksandr , Bilorusets Viktor
Published: August 2024

The characteristic operating parameters for such equipment, like aviation GTEs, primarily include high speeds of the power shaft rotation and, consequently, high mechanical and thermal loads on the bearings. Ceramic materials, i.e., hybrid bearings, are proposed for the rolling elements in these bearing units. Ensuring the operational safety of bearings of this class, the problem of predicting wear of their components, is extremely relevant. In our work, we investigate the patterns of the degradation process and determine the optimal composition and structure of sintered ceramics for bearing rolling elements. Search for optimal sintering parameters for materials that provide corresponding physico-mechanical properties[1]. Methods for assessing the degradation of investigated materials after operation under specific conditions: Morphometric analysis of wear products. Various types of microscopy and profilometry of damaged surfaces of ceramic balls. Methods for analyzing the operational characteristics of the "in situ" unit[3][4]: Changes in the unit's vibration spectrum[2]. Changes in the spectrum of acoustic emission. Changes in temperature[2]. Resource prediction based on the analysis of obtained data. Various types of ceramics were considered for the study, among which Si3N4-based material proved to be the best. Microscopy and profilometry revealed changes in surface roughness and the formation of characteristic "material tears" and "pits", known as pitting corrosion. This is a specific case of fretting corrosion, which occurs during the cyclic movement of two contacting surfaces. The images show that the pits have a layered shape, torn due to the formation of subsurface cracks. The structure of the materials of worn balls, the surfaces of which are covered with "pits", has a fragmented structure consisting of particles smaller in size than the original powder used for sintering. The research suggests dividing the operational process into stages: I - cyclic loading of ceramic balls of the hybrid friction pair rolling at high temperatures until the initial damage is detected; II - accumulation of damage in the surface layer due to contact fatigue and initiation of subsurface cracks in ceramic balls; III - formation of surface pitting.
To the design of grain structure in ceramics
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Oleynik Galina , Kotko Andrii
Published: August 2024

Design of ceramics with predetermined microstructure is based on the arrangement of concordant structure transformations under sintering of selected phase components, whose evolution determines the formation of required microstructure elements, their crystal morphology, scale, content, and distribution throughout the volume. Such elements may include grains, intergrain and interphase boundaries, elements of substructure responsible for the appearance of intragrain boundaries,such as dislocation, twinning, domain, and interphase ones, and pores of different types. Knowledge of these mechanisms is the base for design of novel materials an dimprovement of the currentones. The grain structure is a basic material structure component. Based on our research (using TEM with microdiffraction and SEM with microanalysis) and literature data, general regularities of grain structure formation in ceramics are considered in the course of primary (PR) and collective (CR) recrystallization and during formation of composites under sintering. It’s worth noting that recrystallization in ceramics was first studied by G.V. Samsonov at our Institute. PR in ceramics can occur under different conditions of loading such as free sintering, hot pressing including that under highpressure, uniaxial compression, rolling, friction, etc. The structural mechanisms of the PR evolution in ceramics are similartometals. The formation of grain structure in composites is determined by structure transformations due to the contact interaction of phase components; transformations in the grain volume of initial phases (plastic fragmentation, polymorphic transformations, decomposition of solid solutions, twinning, domainization, etc.); transformations in grain boundaries (phase transitions, boundary faceting, etc.). All of them lead to refining grain structure due to the formation of new grains and saturation of the initial ones with internal boundaries resulting from substructure formation [1].
Effect of electric arc spraying of Al-4.6Cu-1.5Mg coating and its plasma-electrolyte treatment on the corrosion resistance of Mg-8.5Al alloy in 3% NaCl
Authors:   Karpenko Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Veselivs'ka Halyna , Hvozdets’kyi Volodymyr , Student Mykhailo , Zadorozhna Khrystyna
Published: August 2024

Since magnesium alloys, which are widely used in the automotive and aviation industries, have insufficient wear resistance and corrosion resistance, there is a need to improve their surface properties. The purpose of the study was to determine the effect of the Al-4.6Cu-1.5Mg aluminium electric arc coating (EAC) sputtered at an air jet pressure of 1.2 MPa and the synthesized plasma-electrolyte oxidized (PEO) layer on it on the structure and some characteristics of the Mg-8.5Al magnesium alloy. The microstructure of the coated samples was studied on an EVO 40XVP scanning electron microscope. X-ray phase analysis of the coating was performed in Cu-Kα radiation. The porosity of the PEO layers was determined by hydrostatic weighing. Microhardness was determined using a microhardness tester. The electrochemical characteristics in 3% NaCl of the obtained coatings were determined from the potentialdynamic polarization curves taken at a scanning speed of 1 mV/s. EAC with a thickness of ~ 250 μm on magnesium alloy have a typical lamellar structure and are porous. The lamellae are separated by thin Al2O3 oxide films. In the process of PEO, the electrolyte penetrates the EAC, accumulates in its pores, and the formation process occurs as if from its middle, the lamellae disappear and its porosity is reduced by half. This increases the microhardness of the coating. Electrochemical studies have shown that the PEO of an aluminium coating additionally increases its corrosion resistance in NaCl solution by more than an order of magnitude [1]. Thus, spraying coatings from aluminum alloys onto magnesium alloys, followed by PEO treatment, makes it possible to produce oxide ceramic coatings with properties on par with PEO coatings on aluminum alloys. This integrated approach makes it possible to create oxide ceramic coatings on other alloys that are not subject to PEO treatment, such as steels and cast irons.
High-temperature ceramic composites directionally reinforced with high-entropy borides
Authors:   National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Bogomol Iurii , Ferkhatly Elmira , Duan Mantang , Rieznik Dmytro , Ponomarchuk Serhii , Zaulychnyi Yaroslav , Stepanov Oleh , Mosiak Vasyl , Kryvenko Kira , Palagecha Dmytro
Published: August 2024

Materials based on boron and silicon carbides are increasingly used in industry due to its unique complex of physical and mechanical properties mostly at high temperatures up to 2000 o C [1]. One of the most effective ways to improve the strength of the ceramics is a fiber reinforcement, which is realized in the directional solidification of eutectic alloys. In recent years, high-entropy borides (HEB) have attracted considerable interest due to their potential applications as high-temperature structural materials [2]. I this work authors used high-entropy borides as the reinforced phase during directional solidification of eutectic alloys based on boron and silicon carbides [3]. The directionally solidified composites (В 4 С-HEB, SiC-HEB) were prepared by the floating zone method based on the crucible-free zone melting of compacted powders and Spark Plasma Sintering. B 4 C, SiC and powders of transitional metals diborides (TiB 2 , ZrB 2 , HfB 2 , TaB 2 and NbB 2 ) with technical purity were used as the initial materials. The microstructure of all as prepared alloys consists of B 4 C or SiC matrix uniformly reinforced by single phase diboride fibers and lamellas. The formation of eutectic structure, phase compositions and some mechanical properties of the directionally reinforced composites were discussed.
Heat-resistant non-combustible material for covering surfaces of special configurations
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Diduk Iryna , Chuvashov Yurii , Yashchenko Olga , Trofimova Tamara
Published: August 2024

Thermal insulation products are available in a wide range. Organic and inorganic binders are used to produce thermal insulation coatings that provide adhesion to the coating surface. Basalt Super Thin Fibres (BSTF) with an average diameter of 2 µm; canvas density of 20 kg/m3; thermal conductivity of no more than 0.038 W/m K at a temperature of 25 °C were used for the study. Both inorganic binders (gypsum, cement, bentonite clay) and organic binders (resin FRV 1-A and hardener VAG-3, hydrolysed ethyl silicate, bakelite varnish) were used as binders. The criterion for selecting the composition of the sprayed coating was the need to obtain a fibrous composition with the highest possible thermal insulation properties. Therefore, the research was focused on the development of a binder with high frost and moisture resistance and insignificant changes in physical characteristics over a wide temperature range. The introduction of BSTV into the binder was carried out by mixing it with hydromass. As a result, samples were obtained dispersed reinforced with basalt fibres. The selection of the composition of the thermal insulation samples was evaluated by the coefficient of thermal conductivity, water absorption, and density. Experiments with bentonite clay showed the best results, as the resulting material has a lower bulk density, is chemically inert, and is environmentally friendly to use. According to the conducted researches it is established that the content of clay binder in clay-fibre compositions should be within the limits from 5 to 30 %, depending on the required density and strength of thermal insulation. Other conditions being equal, with increasing density the thermal insulation properties of fibre insulation at ordinary temperature deteriorate, while at increasing temperature from 300 to 500 C the thermal insulation properties improve with increasing density. It was found that the optimum density is 220 to 250 kg/m3 for the above conditions.
Phase transformations in the Al-Fe-Mo system
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Fartushna Iuliia , Bulanova Maryna , Samelyuk Anatolii , Vitusevych Victor
Published: August 2024

Introduction Fe3Al-based alloys are considered to be potential high-temperature structural materials due to their excellent resistance to thermal corrosion, high-temperature oxidation and sulfidation, combined with high strength, low density and comparably low cost. However, they have several disadvantages, such as low ductility at ambient temperatures and insufficient strength above 600°C. The addition of molybdenum increases the yield strength, tensile strength and resistance to wet corrosion [1, 2]. Methods Bulk metals of Al-99.995%, Fe-99.9%, Mo-99.9% were used to produce the ternary alloys. Alloys of 1-3 g were prepared by arc-melting under a puriﬁed Ar atmosphere (99.998%) using a non-consumable tungsten electrode on a water-cooled copper hearth. The samples were homogenized at 1450, 1300 and 1200°C during 30-100 h in a resistance furnace SShVL-0.6.2/16. The annealed alloys were then examined by scanning electron microscopy, electron probe microanalysis, and X-ray diffraction. Results Isothermal sections at 1450, 1300 and 1200°C have been determined experimentally for the first time in the entire range of compositions. The ternary intermetallic compound Al8FeMo3 (τ) with Al3Ti-type structure was observed at all investigated temperatures. It was shown that the (Mo) and (αFe) phases form the continuous solid solution (αFe,Mo) at 1450°C, which decomposes into (Mo) and (αFe) phases with the temperature decreases. The Fe7Mo6 (μ) phase, which in the binary Fe-Mo system is formed in solid state at 1368°C, extends into the ternary system up to 16 and 15 at.% at 1300 and 1200°C, respectively. Addition of Mo stabilizes the Al8Fe5 phase, and at 1300°C a narrow homogeneity region of this phase is present, the solubility of Mo in Al8Fe5 at 1200°C was measured as 14.4 at.%. The ternary Al-Fe-Mo and binary Al-Mo systems are thermodynamically re-modelled. The calculated phase diagrams are in good agreement with the corresponding experimental data.
Electrical Resistivity of AlN-hBN-TiB2 Ceramic Composite
Authors:   Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, 2 Avtozavodska Str., Kyiv, 04074, Ukraine, Fesenko Igor , Kaidash Oksana , Sergienko Nina
Published: August 2024

Dielectric matrix ceramic composites based on high thermal conductivity AlN are important for engineering of new electronic devices with lower operation temperature. Composites of AlN dielectric matrix with electroconductive inclusions of TiB2 have been prepared and investigated with the aim to establish their electrical resistivity for possible applications. The ceramic composites AlN–hBN–TiB2 have been prepared by hot pressing (T=1950 °С, P=30 MPa) with TiB2 content from 45 to 66 wt.%. The four-probe electrical resistivity measurements of as-obtained specimen at room temperature showed correspondingly values between 1.0•10–5 and 0.2•10–5 Ohm•m. The observed relatively small decrease of electrical resistivity of the hot-pressed AlN–hBN–TiB2 system composite for increasing conductive phase content by 21 wt.%, and when conductive phase content is higher than a percolation threshold may testify in favor of a tunnel character of charge transfer, discussed in [1]. Addition of hBN under mixing of the starting powder system may form an additional dielectric layer at the surface of the conductive particles (TiB2). Thus a tunnel mechanism of charge transfer in the hot-pressedAlN–hBN–TiB2 ceramic composites may dominate in a wide region of concentrations including the percolation threshold.
Electronic structure of cubic and rhombohedral tantalum carbide phases: DFT calculations and X-ray photoelectron and X-ray emission spectroscopy measurements
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Luzhnyi Ivan , Shcherbakov Egor , Bystrenko Tetyana , Bystrenko Oleksiy , Khyzhun Oleg
Published: August 2024

Transition metal (TM) carbides are generally nonstoichiometric compounds crystallized within high-symmetry FCC and HCP structures. Carbides based on refractory metals of the IVb - VIb groups are of great importance for scientists and engineers because of their possibility to form intermediate phases in the region of compounds between MC phases (which crystallize in the FCC structure) and M₂C phases with HCP structure. Such intermediate carbide phases are superstructures. Unit cells of these superstructures are described in hexagonal or rhombohedral (trigonal) systems and are characterized by large values of hexagonal lattice parameter ratio [1]. In the present work we study from both experimental and theoretical approaches the electronic structure of cubic TaCₓ phases (x = 0.98 and 0.75) and rhombohedral Ta₄C₃ (C/M=0.74) and Ta₃C₂ (C/M=0.67) phases synthesized following the technique [2]. In particular, we have measured energy distributions of the C 2p- and Ta 5d-electronic states and determined experimentally the valence-band structures employing X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) measurements, respectively. Furthermore, the present XES and XPS data are verified theoretically by first-principles calculations of total and partial densities of states that are made using the Quantum Espresso software package. We have achieved good correspondence between the experimental and theoretical data in the present work. The present results indicate that, in the sequence TaC₀.₉₈→TaC₀.₇₅→Ta₄C₃→Ta₃C₂ the main maximum of the XPS valence-band spectra shift toward the Fermi energy. In all studied tantalum carbides, a strong hybridization between Ta 5d- and C 2p-electronic states is detected and the charge transfer occurs from tantalum atoms to carbon atoms.
Consolidation features of ZTA-composite with eutectic composition
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Marek Iryna , Smirnova-Zamkova Maria , Red'ko Victor , Martsenyuk Iryna , Gerashchenko Viktor , Mosina Tetyana , Ruban Olexiy
Published: August 2024

ZTA are ceramics in the Al2O3–ZrO2–Y2O3–CeO2 system, which are characterized by high-temperature mechanical strength, heat resistance, wear resistance, oxidation resistance, low thermal conductivity, as well as a small ratio between the coefficients of thermal expansion of ZTA and metals [1]. The mechanical properties of ceramics depend mainly on the amount of ZrO2, its grain size, as well as the ratio of T-ZrO2 and M-ZrO2 and their location in the Al2O3 matrix. ZTA with a composition close to the Al2O3–ZrO2 eutectic are considered as a promising ceramics. The purpose of the research is to determine the consolidation features of the ZTA composite containing 58.5% (wt.) ZrO2 (Y2O3, CeO2). The composition of a solid solution based on ZrO2 (ZrO2 (Y2O3, CeO2)) (mol.%) is 90 ZrO2–2Y2O3–8 CeO2. Cold uniaxial pressing were used for the green bodies formation. Sintering was carried out in the Nabertherm LTH08/17 laboratory electric furnace at 1500 °С, 2 hours. Grinds of sintered samples longitudinal sections were made to determine of Vickers hardness. Sintered materials were investigated by X-ray phase analysis (XRF) and scanning electron microscopy. The Vickers hardness was measured using a "Falkon 509" hardness tester (manufactured in the Netherlands) with an indenter load of 300 N (30 kg). The relative density of green bodies 0.46. The relative density of sintered samples was up to 0.97. Phase composition – T-ZrO2, α-Al2O3. A certain orientation of Al2O3 grains was found observed in homogeneous areas, which is a manifestation of the ceramics "topochemical memory", since the composition of the composites corresponds to the eutectic of the binary system Al2O3–ZrO2. Microhardness was 190 MPa, Vickers hardness reached 3.7 GPa, K1c = 7 MPa m 0.5. Using of improved approaches under consolidation of the ZTA eutectic composition will help improve their mechanical characteristics under the microstructural design of high-tech instrumental, structural and functional ceramics
Properties of Multilayer Nitride Coatings Based on Chromium and Niobium
Authors:   National Science Center ", Serdiuk Iryna ,   Kharkiv Institute of Physics and Technology",   , Ukraine, Stolbovyi Viacheslav , Kryvoshapka Ruslan , Andreev Anatoliy , Petrushenko Sergiy , Fijalkowski Mateusz
Published: August 2024

In recent years, the development of coatings for different applications is based on the combination of coating components with different physical, mechanical, electrical, optical properties and the complication of the coating structure (1-3). One of important factors affecting the functional properties of multilayer coatings is the state of the interphase boundary between layers with the different phase composition and structural state. This becomes especially significant when the thickness of layers is reduced to tens of nm. Nitride multilayer coatings based on chromium and niobium were deposited in a modified installation “BULAT-6” (4). AISI 430 stainless steel samples were used as substrates for deposition of coatings. Three series of coatings were obtained. Planar raster electron microscopic images were obtained using a Tescan Vega 3 SBU. Cross sections were examined in a field emission scanning electron microscope (Zeiss ULTRA Plus). Investigation of multilayer nitride СrN/NbN coatings, which were obtained under different technological parameters of deposition (constant negative voltage on the substrate is from −70 to −200 V, nitrogen pressure in the vacuum chamber is from 0.08 to 0.27 Pa, the total number of layers N (68, 270, 1080), the bilayer period is from 6.7 to 230 nm) made it possible to expand the understanding of the technological parameters’ influence on properties of obtained coatings. Cross-sections analysis of multilayer nitride CrN/NbN coatings of three series with different number of layers and bilayer period showed that the total thickness of coatings was 3.6 µm for coatings of the first series, which were obtained by continuous rotation of the substrate holder, and about 8 and 9 µm for coatings of the second and third series, respectively. Elemental analysis showed that obtained coatings of series II and III have high planarity of layers and practically no droplet phase in the volume of multilayer nitride CrN/NbN coatings.
On changes in the mechanism of chemical affinancy in the synthesis of compounds of refractory metals with oxygen group elements
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Petrash Kostiantyn , Bagliuk Gennadii , Solntseva Tetiana
Published: August 2024

Thermodynamic interpretation of chemical affinity as the tendency for chemical components to interact was given by Théophile de Donde. It manifests itself in systems up to the threshold of thermodynamic stability. In work [1], during the decomposition of unstable chalcogenides of refractory metals and during their interaction with metals of IVA, VA groups and chromium, both the existence and synthesis of unstable compounds of these metals with chalcogen type MeX3, MeX4 were established. An increase in the amount of chalcogen is observed during decomposition. To clarify the nature of the mechanisms of formation of chalcogenides beyond the threshold of thermodynamic stability, their interaction in complex metal systems containing the active reducing agent aluminum and diselenide was studied. The compacts were sintered in vacuum at temperatures above the existence of these chalcogenides. When studying the distribution of elements after sintering, the existence of titanium compounds of various stoichiometries, which is the basis of the composition, was established. No compounds of aluminum with selenium were found. Beyond the limit of thermodynamic stability, compounds are formed with metals that are less prone to interact with chalcogen. Moreover, these compounds are formed and exist at temperatures significantly higher than the region of their existence in the individual state. This phenomenon is due to the formation of a dissipative structure with a characteristic feature of dynamic stability. This type of stability occurs far from thermodynamic equilibrium due to the appearance of autowave processes in the reacting system. In such systems, self-oscillatory reactions occur, which was shown in [2, 3]. Namely, due to the catalytic properties of the seven elements, the manifestation of autowave properties is determined. Thus, the chemical affinity in these systems is determined by the tendency for the catalytic reproduction of atomic elements of the oxygen group.
Application of clad powders for the creation of high-density tungsten heavy alloys
Authors:   National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Polishchuk Kyrylo , Minitsky Anatoly
Published: August 2024

Heavy tungsten alloys are used in many industries due to their high specific gravity and are essential in the production of flywheels, counterweights, gyroscope rotors, gyrocompasses, ammunition, X-ray and radiation screens, etc.) However, when manufacturing parts from heavy alloys using powder metallurgy, difficulties arise due to the uneven density distribution over the volume of lightweight metals, which negatively affects the performance of the products. Therefore, the aim of this work is to study the effect of the chemical deposition of nickel on tungsten particles to ensure uniform distribution of the low-melting metal when creating high-density heavy tungsten alloys. A composite powder based on tungsten with a nickel layer of 2-3 microns thick was obtained. The study of the particle size distribution of the clad powder showed a bimodal particle size distribution, which indicates that not all tungsten powder particles have the same coating thickness. This is due to the fact that the uniformity of the coating deposition depends on the shape and morphology of the initial tungsten particles. The influence of tungsten powder cladding modes on the physical (shape, size, surface morphology, coating thickness), chemical (chemical composition, amount of nickel), and physical and technological properties of clad powders (fluidity, bulk density, density), depending on the concentration of the solution relative to the tungsten powder and on the average size of the tungsten powder, was investigated. The possibility of creating heavy alloys with a uniform distribution of nickel in the material structure, which provides high density and high physical and mechanical properties, is shown. The presented research can be useful in the development of heavy alloys for the military and machine-building industries.
Production of nanosized composite Al-Fe-Cr-Ti alloys and study of their plasticity in the temperature range
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Iefimov Mykola
Published: August 2024

The technological and physical principles for production of nanoquasicrystalline (QC) Al-Fe-Cr-Ti alloys with an increased level of mechanical properties have been developed. The strength of such alloys is provided by high hardness and elastic modulus of QC well as their stability up to relatively high temperatures, plasticity ensured by a special deformation mechanism of QC nanoparticles. The Al₉₄Fe₂.₅Cr₂.₅Ti₁ rods are produced using powder extrusion technology without sintering of high-pressure water atomization powders. The TEM and X-ray methods were used to characterize the structure; the mechanical properties were studied by indentation and mechanical tensile tests. To characterize the behavior of the Al-Fe-Cr-Ti alloys the physical plasticity characteristic δ* was first used. δ* is the ratio of plastic strain to total strain was determined both during indentation and tensile tests. It is shown that Al-Fe-Cr-Ti alloys have record heat resistance characteristics at 300°C: UTS 345MPa, YS 330MPa and elongation 4%, with elongation at room temperature up to 8%. The Al-Fe-Cr-Ti alloys show an abnormal behavior of plasticity change: with increasing temperature, the value of elongation δ gradually decreases in the temperature range of 20-300°C and with further temperature increase its value increases again. This effect is explained by the processes of dynamic strain aging (DSA) which is the instability of the plastic flow of materials associated with the interaction of moving dislocations and diffusing dissolved substances [1]. The δ*(δн) determined both tensile and hardness tests behave without taking into account the DSA effect: δ* and δн increase monotonically with increasing temperature. Thus, the use of δ* to characterize the change in plasticity in the temperature range allows us to characterize the plasticity of the material without considering the processes accompanying its fracture.
Interaction Energy in the Melts of the Fe-Mn-Si-C-Ti System
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Baranovska Oksana , Romanova Larysa , Sudavtsova Valentina , Bagliuk Gennadii
Published: August 2024

Ferrosilicomanganese (Fe0.21Mn0.62Si0.14C0.07) and silicomanganese are widely used in metallurgical and materials science industries due to their ability to melt at low temperatures. The addition of reactive titanium leads to the formation of various phases, each possessing unique properties. Thorough study of their thermodynamic properties, particularly the melts, is essential for optimizing technological processes. However, determining these properties is complex and time-consuming. Preliminary evaluation using geometric and Redlich-Kister-Muggianu models across concentration ranges is advisable, based on data from limiting binary systems. In the work [1], the thermochemical properties of melts of the Fe-Mn-Si system were determined by calorimetry at 1873 K. Comparison of experimental and predicted thermochemical properties of melts of the Fe-Mn-Si system showed that the best agreement is characteristic for the Redlich-Kister-Muggianu model with a ternary contribution of 300 kJ/mol. Applying the same model, thermochemical characteristics of melts of ternary systems Fe(Mn)-Si-Ti, Fe-Mn-Ti, and Si-Ti-C were calculated across the entire concentration range. It was found that the minimum enthalpy of mixing corresponds to the melts of Si-Ti is -70 kJ/mol, Fe-Ti is -20 kJ/mol, and Ti-C is -115 kJ/mol, indicating predominance of pairwise interactions. This is supported by the results of X-ray diffraction analysis (XRD) and electron microscopy studies. However, according to XRD, the synthesis of the mentioned metal-matrix composites (MMCs) results in the formation of the ternary compound Ti3SiС2. According to our modeling, melts of such composition exhibit a significant heat release (-110 kJ/mol), suggesting the formation of such a compound is expected. The formation of various binary and ternary phases enhances the strength, hardness, and other properties of the metal-matrix composites.
Development of cubic boron nitride synthesis processes using non-traditional technologies (overview)
Authors:   V. Bakul Institute for Superhard Materials of NASU, Borymskyi Oleksandr , Starik Sergey
Published: August 2024

Cubic boron nitride (cBN) powders are widely used for construction and instrumental materials in various fields of science and production. The purpose of this work is to monitor the efficiency of processes for the synthesis of cBN powders using a variety of non-traditional technologies, including mechanically activated reaction mixtures and additional crystallization centers (DCC) [1]. It was established that the use of a mechanically activated reaction charge allows to increase the degree of conversion of hBN→cBN from 30-50 achieved without activation to 85-90 % (by mass) and to obtain a product that mainly consists of micropowders of a deficient narrow grain size range with an average grain size of 3-4 to 10-14 microns. The possibility of synthesizing lithium bornitride Li3BN2 by mechanical activation of the initial components is shown and the high efficiency of its use in the synthesis of cBN powders is established. The process of synthesis of mixtures of the Mg3N2–MgО system in the mode of combustion of Mg powder in air was studied and the high efficiency of their manufacture and use as components of the reaction charge in the synthesis of cBN powders was established. It is shown that the grains obtained by crushing compacts based on dense modifications of boron nitride, such as hexanite-A and kyborite, are effective DCC in the synthesis of cBN. It was found that the use of hexanite-A grains with a wurtzite content of about 20% (by mass) in the synthesis of cBN as a DCC leads to the formation of two-layered hexanite-cBN grains, which consist of a polycrystalline inner part (hexanite-A) covered with an outer layer that has grown on it layer with cBN. The effectiveness of using such two-layer hexanite-cBN grains as an abrasive tool material is being investigated.
Phase Relation of the ZrO2–HfO2–La2O3 System at 1500-1100 °C
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Korniienko Oksana , Korichev Sergey , Sameljuk Anatoliy , Barchevska Hanna , Subbota Irina
Published: August 2024

Complex oxides such as the rare-earth zirconate and hafnate ceramic materials in the fluorite-type (space group Fm3m) and/or pyrochlore-type structure (space group Fd-3m) display a variety of interesting and promising physical, chemical, thermal and magnetic properties which render them excellent candidates in applications such as thermal barrier coatings, solid electrolytes, materials for nuclear industry, and are of interest as luminescent materials, scintillators for applications in radiation detectors and others. The phase diagrams of multicomponent systems are the theoretical basis for the creation of new functional and structural materials. In the presented work, for the first time phase equilibria and physicochemical properties of phases formed in the ZrO2–HfO2–La2O3 ternary system at a temperature of 1500, 1250 and 1100 °C (in the air) in the entire concentration range were researched using powder X-ray diffraction and microstructural analysis. The samples were prepared with a concentration step of 1-5 mol.%. X-ray diffraction analysis (XRD) of the samples was performed by the powder method on the DRON-3 device at room temperature. The scanning step was 0.05-0.1 degrees, the exposure was 4 sec. in the 2 angles range from 10 ° to 100°. In the present work, phase equilibria in the ZrO2–HfO2–La2O3 ternary system have been studied, and isothermal sections of this system at temperatures of 1500 1250 and 1100 °С were constructed. It was found that, at these temperatures, the formation of new compounds in the studied system is not observed. The studied isothermal sections are characterized by the formation of a continuous series of solid solutions based on an ordered phase with a pyrochlore-type structure. It was found that the isothermal sections of the state diagram of the ZrO2–HfO2–La2O3 system at 1500 and 1250 °C are characterized by the existence of four two-phase regions (A+Py, Py+T, Py+M, T+M) and one three-phase region (Py+T+M).
Application of Samsonov’s configuration model in establishing the influence of the electronic structure of d-metals on thermal electron emission of WBa cathodes
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Makarenko Olena , Podchernyaeva Iryna , Hetman Olha
Published: August 2024

Electron emission from WBa-cathodes is carried out from an adsorbed layer of barium and oxygen atoms on W or other d-metal adsorbents. When films of the d-metals Re, Os, Ir and Ru are deposited on the emitting surface, the work function φ decreases by 0.2 eV; and in the case of Pt, Pd and Au, it increases by 0.2 eV. The aim of the work is determine the effect of the electronic structure of d-metals on the work function of the WBa cathode using the Samsonov configuration model. According to Samsonov’s configuration model, the formation of a condensed state is accompanied by the division of valence electrons into two subsystems: localized and itinerant electrons. Free-filled and half-filled configurations such as s2, s2р6, d0, d5, d10 are the most energetically stable in the spectrum of configurations.According to Samsonov’s model, oxygen atoms are electron acceptors, since they tend to fill the valence orbitals 2s22p4 with electrons in the energetically more stable state of 2s22p6. Ba atoms are electron donors, donating their 6s2 valence electrons to oxygen to form surface dipoles Ba+– O- with ionic bonds. These dipoles reduce the work function of W. Re, Os, Ir and Ru atoms have unpaired electrons in the orbitals d6 and d7, which, upon energy absorbing, transform into sp-valence states and can be electron donors, ensuring the maximum population of sp - states of oxygen. As a result, the degree of polarizability of Ba+ – O- dipoles on the surface of these adsorbents increases, which further reduces φ. Pt, Pd and Au atoms with stable d9 and d10 orbitals have a reduced donor ability and do not have the effect of reducing the work function. Сonclusion. The main mechanism of emission of WBa cathodes is the donor-acceptor interaction of adsorbed atoms among themselves and with the adsorbent, leading to the formation of polarized dipoles responsible for the escape of electrons into vacuum.