bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of physicochemical surface treatment of on the content and composition of inclusions and impurities in synthetic diamonds
Authors:   Bakul Institute for Superhard Materials of National Academy of Sciences of Ukraine, Ilnytska Halyna , Lavrinenko Valerii , Loginova Olga , Starik Serhii , Smokvyna Volodymyr , Zaitseva Iryna , Tymoshenko Viktoriia , Kotynska Liudmyla , Bilorusets Viktor , Venikov Vladislav
Published: August 2024

The purpose of the work was to conduct research to determine the content and composition of intracrystalline inclusions and impurities in synthetic diamond powders used in grinding production. The research was conducted on diamond grinding powders of the AC20 (according to regulatory documents of Ukraine) grade with a grain size of 125/100, obtained in the Ni-Mn-C system, before and after their thermochemical treatment in an alkaline melt1. Physico-mechanical characteristics were determined: compressive strength; the specific magnetic susceptibility. The total content of inclusions and impurities was determined in the form of unburned residue, obtained after long-term high-temperature treatment to a constant mass. The surface condition, total content, and elemental composition of the original diamond grinding powders and unburned residues before and after thermochemical treatment were determined by the SEM and X-ray spectral microanalysis (processing in an alkaline melt at a temperature not exceeding 600°C). It is shown that their strength is slightly reduced as a result of the thermochemical treatment of the surface of diamond grinding powders. Due to the dissolution of a certain part of inclusions and impurities, there is a decrease in the quantitative content of the non-combustible residue by 2 times and a weakening of the magnetic properties by approximately 1.4 times. The total content of inclusions and impurities in diamond powders after their thermochemical treatment decreases by approximately 5wt.%, and the content of carbon solvent alloy elements (Mn+Ni) - by 6wt.%. Additional chemical elements (Mg, K, Ca, Fe) were detected in X-ray spectra microanalysis from the surface of diamonds after their thermochemical treatment, which were not present in the composition of diamonds before treatment. The total quantity and elemental composition of unburnt residues of grinding powders before and after thermochemical treatment decreases by 2.4 times, and the content of carbon solvent alloy elements (Mn+Ni) in them by 1.7 times.
Modification of basalt fibers to improve operational efficiency in aggressive environments
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 , Koshelenko Nataliya , Grytsak Ganna
Published: August 2024

The use of basalt fibre as a reinforcing element, including in cement-concrete compositions, is increasing. However, the surface layer of fibers is dissolved during long-term use in the cement matrix, which is associated with cement hydration. Increasing the corrosion resistance of basalt fibers can be achieved by modifying the fibers by heat treatment. The influence of the temperature and processing time of basalt fibers on the chemical stability of fibers in alkaline and acidic environments is studied. For the experiment, fibers with a surface area of 5000 cm2 were taken and kept in solutions of 2N NaOH and 2N HCl at boiling for 3 hours. Chemical resistance was evaluated by the loss of fibre weight. The fibres were preliminarily subjected to thermal treatment in a muffle furnace in the temperature range from 300 to 800 C every 100 C, and the time of treatment was 10, 20, and 30 min at each temperature. The average diameter of the studied fibres was 10-14 µm. The fibres were produced under the same forming parameters on a single-filament laboratory stand. The raw material used was basalt with an acidity modulus of Mk = 4.7 and an initial fibre stability in 2N NaOH of 83.8 % and in 2N HCl of 78.7 %. It has been determined that the maximum increase in alkali resistance is observed at holding temperatures of 400 C and 800 C. The maximum increase in acid resistance is observed during heat treatment at higher temperatures of 600, 700, 800 C and is an increase of 20-25 % from the initial one. With an increase in treatment time, the values in both cases decrease, so the optimal isothermal treatment time does not exceed 10 minutes. In the process of heat treatment of fibres, structural changes occur due to phase transitions of iron oxides Fe2+ to Fe3+, with a change in colour, basalt fibres acquire a browner (reddish) shade of colour. The phase transition is accompanied by the appearance of crystalline phase, which causes an increase in fibre density by 10-20 %
On the crack resistance of ceramic composites based on silicon nitride
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Goncharova Irina , Galanov Boris , Iefimov Mykola , Tsivilitsin Vadim
Published: August 2024

The work carried out a study of the crack resistance K₁c, calculated theoretically and experimentally determined during mechanical tests, for two systems of ceramic composite materials based on silicon nitride. 1. Electrical materials of the Si₃N₄–SiC system were obtained by reaction sintering. The grain size of the base (Si₃N₄) was 1-2 μm, the SiC additive varied in size from 1-5-120 μm and content of 0, 10, 20, 30%. 2. Structural materials of the Si₃N₄–TiN system were obtained by hot pressing. The grain size of the base (Si₃N₄) was 1-2 μm, TiN additive varied in size 1-5-30 microns and content 0, 10, 20, 30, 40, 50%. Based on theoretical concepts [1] the values of crack resistance K₁c of composites with known K₁c values for pure components were determined by calculation. Theoretical concentration dependences of crack resistance were obtained, which are curves with a maximum in the range of additive concentrations of 20-30%. By testing the bending of notched beams for all materials of the Si₃N₄–SiC and Si₃N₄–TiN system (both for pure components and for composites for all concentrations and grain sizes of the additive), the K₁c values were experimentally determined. A fairly good agreement between the experimental and calculated values of K₁c was obtained for all materials studied, with the discrepancy being less 5 %. In the case of a coarse-grained additive, the discrepancy between theory and experiment was large. This is explained by the high stress concentration in large grains and, therefore, even a small number of large grains lead to a sharp decrease in K₁c. As a result of the research it was found that physical patterns of changes in the crack resistance of composite materials depending on the concentration of components. A fairly good agreement between theory and experiment was obtained using the example of binary systems Si₃N₄–SiC and Si₃N₄–TiN (the discrepancy between the theoretical and experimental values of crack resistance does not exceed 5%).
Synthesis of Composite Powders of the Si3N4–NbN System
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Poliakov Ihor , Kud Iryna , Myslyvchenko Oleksandr , Mediukh Roman , Krushynska Larysa , Zgalat-Lozynskyy Ostap
Published: August 2024

Ceramic composites based on silicon nitride belong to the most promising materials for producing wear-resistant products operated under extreme conditions [1]-[3]. The present work is devoted to the investigation of conditions for preparing Si3N4–20 vol.% NbN highly disperse composite powders by in situ solid-state synthesis from Si3N4–Nb reaction mixture and by the traditional method of mechanical mixing of Si3N4 and NbN constituent compounds. The Si3N4–NbN and Si3N4–Nb reaction mixtures were mixed in a Pulverizette 6 planetary mill. Synthesis products were investigated by the XRD and SEM methods. The particle-size distribution of the composite powders was determined by the laser diffraction method. The behavior of reaction powder mixture of stoichiometric compositions calculated for the synthesis of higher niobium nitride in the temperature range 800–1400 °С in vacuum by the reaction 4Nb + Si3N4 was investigated [2]. Based on the established regularities, we developed a combined two-stage technological synthesis process of Si3N4–NbN powder, including vacuum annealing at 1000 °С and subsequent nitriding at 1300 °С, which enabled us to obtain Si3N4–20 vol.% NbN powder consisting of multiphase agglomerates with a mean size ≤3 µm and a nanodisperse fraction with a mean particle size of 200 nm. For the preparation of Si3N4–20 vol.% NbN composite powder by the traditional mechanical mixing method, β-Si3N4 and δ-NbN powders synthesized under laboratory conditions were used. The mean particle size of the obtained composite powder is ≤10 µm. We established advantages of the method of in situ solid-state synthesis of Si3N4–NbN powders, which guarantees obtaining fine-grained powder with a mean particle size ≤3 µm and a uniform distribution of nitride phases in a single technological cycle.
Innovative family of AlMg(X)Si(Y)Mn casting alloys for industrial applications
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Voskoboynik Igor , Grinkevych Konstantin , Voskoboynik Igor
Published: August 2024

The choice of the innovative family of AlMg(X)Si(Y)Mn for the development of high-strength aluminum foundry alloys with increased fluidity has several justified reasons. The wide regions of univariant eutectic transformation in innovative family of AlMg(X)Si(Y)Mn casting alloys allow for flexible variation of alloy component ratios while maintaining their phase composition [1]. The structure of alloys in this system morphologically resembles modern foundry alloys, and the nature of phase equilibria allows for a significant increase in magnesium content in the solid solution compared to traditional foundry alloys. Thus, materials can be created that simultaneously utilize all strengthening mechanisms (composite, solid solution, and dispersion). Considering the peculiarities of the topology of the phase diagram of innovative family of AlMg(X)Si(Y)Mn casting alloys contributed to the creation of a new high-strength (σB up to 450-500 MPa) aluminum-based casting alloy. In this alloy, the matrix is a solid aluminum solution strengthened by Mn and Cu-containing phases that do not interact with the eutectic and are precipitated during thermal treatment. The influence of natural aging on the hardness of Mn and Cu alloyed alloys has been investigated. An increase in the saturation of the solid solution during alloying or an increase in quenching temperature accelerates the processes of forming precipitates that strengthen the matrix, thus the increase in hardness in the first 48 hours after quenching depends on the temperature and composition of the alloys. Subsequent artificial aging proceeds through altered stage decomposition, increasing the hardness of the alloys and, consequently, reducing their ductility and fracture toughness. A heat treatment regimen was developed, including quenching and subsequent two-stage aging.
Model features of films of iron nanoislands that determine electron tunneling
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Korotkov Kostyantyn , Dmitriev Alexander , Kasumov Anatoliy , Ievtushenko Arsenii
Published: August 2024

Iron island films with a thickness of less than 30 nm undergo rapid surface oxidation in air, which significantly changes their conductivity-related properties, such as the inter-island electron tunneling[1]. The purpose of this work is to study this process. The study of the temperature dependence of the resistivity of oxidized iron films has shown that when the film thickness decreases below 35 nm, a transition from a metallic conduction mechanism with a characteristic linear shape to an activation (exponential) shape occurs. The activation process in this case may consist of electron tunneling between Fe islands. This means that a film thickness of 35 nm is critical [2] for initiating the process of percolation of the islands. The activation energy of oxidized Fe films is 0.018 eV, which is close to the value of 0.01 - 0.001 eV obtained for unoxidized films. In other words, the activation energy depends mainly on the size of the islands and the distance between them, rather than on their chemical composition. The arrangement of oxidized iron island films on rare earth metal (RΕΜ) oxide leads to a d-f exchange interaction between d-atoms of iron and f-atoms of REΜ. This interaction organizes the magnetic structure of Fe and magnetite, i.e., increases the orientation of electron spins in them [3]. The study showed that the resistivity of oxidized Fe films on REM oxide is lower than on glass due to the higher order of spins in the islands and the absence of energy consumption for spin transfer during electron tunneling between them. In this regard, the tunneling magnetoresistance (TMR) in oxidized Fe films has a negative sign, and when the film is on REM oxide, the TMR value is higher than when it is on substrates made of other materials. Thus, the model of island films allows us to understand the peculiarities of their conductivity under different experimental conditions.
Temperature–Composition Sections of the Hf–Rh–Ir System
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Korniyenko Kostyantyn , Kriklya Lyudmila
Published: August 2024

Alloys of the Hf-Rh-Ir system are refractory materials similar to Ni-based superalloys with higher melting temperatures, low values of thermal expansion coefﬁcients, good mechanical properties at high temperatures and oxidation resistance. Binary alloys based on HfRh3 or HfIr3 are proposed as thermal barrier coatings, on Hf2Rh — as hydrogen adsorbents. To develop high-temperature functional materials based on the Hf-Rh-Ir alloys, an understanding of phase equilibria in this system is essential. The alloys of the Hf-Rh-Ir system of 16 compositions are prepared from iodide processed Hf, Rh wire and refined Ir powder (purity of 99.98%, 99.97% and 99.97%, respectively) by arc melting. The alloys are investigated in as-cast and annealed at subsolidus temperatures states by optical microscopy, scanning electron microscopy, electron probe microanalysis, differential thermal analysis, melting points measurements (Pirani-Alterthum technique) and X-ray diffraction. Based on the results of the alloys studies, solidus surface of the Hf-Rh-Ir system [1] as well as liquidus surface, melting diagram and Scheil diagram are represented. Also the vertical temperature-composition sections of the system phase diagram by the ray Ir : Rh = 1 : 1, along the isopleths at 15,0 at.% Ir, 10,0 and 42,5 at.% Rh as well as at 30,0; 33,0 and 62,5 at.% Hf are constructed for the first time. These sections demonstrate characteristic peculiarities of phase equilibria in the system in particular temperature ranges of alloys crystallization and character of phase transformations. So, the vertical section by the ray Ir : Rh = 1 : 1 shows the influence of Hf on the phase equilibria character. It was established that liquidus and solidus curves of the continuous series of solid solutions between high-temperature modiﬁcations of HfRh and HfIr with CsCl-type structure decrease quite steeply (vertical sections by the ray Ir : Rh = 1 : 1 and along the isopleths at 15,0 at.% Ir and 10,0 at.% Rh).
Boron carbide based tungsten containing sandwich composites as neutron shield materials
Authors:   Georgian Technical University, Georgia, Chkhartishvili Levan ,   Ferdinad Tavadze Metallurgy and Materials Science Institute, Georgia, Barbakadze Natia , Otar Tsagareishvili Otar Tsagareishvili , Mikeladze Archil , Mirzayev Matlab , Lekashvili Oliko , Ketevan Kochiashvili Ketevan Kochiashvili , Roin Chedia Roin Chedia
Published: August 2024

Nuclear power industry requires structural materials that effectively absorb neutron radiation. For this purpose, boron and boron-rich compounds and, in particular, boron carbide B4C and its composites are widely used. Both theoretically (see, e.g., [1, 2]) and experimentally (see, e.g., [3, 4]) it has been shown that one such promising class of materials is boron carbide compositions with tungsten B4C–W: tungsten phase inclusions containing heavy W atoms provide effective attenuation of the secondary gamma-radiation that accompany the absorption of primary neutrons by the boron 10B isotope atoms. Composites with sandwich and poly-sandwich morphologies – W/B4C/W, W/B4C/W2B5, W2B5/B4C/W2B5, etc. – in which boron carbide layers alternate with metallic tungsten and/or tungsten boride ones, were produced and investigated. Surface metallization of boron carbide crystals or grains with tungsten (a) powder, (b) plate or (c) coating (formed by peroxpolytungstic acid aqueous solution treatment at 600°C in hydrogen flow) was done by SPS (Spark-Plasma Sintering) at temperature of 1300–1700°C and pressure of 20–40 MPa for 6–10 min. Such layered composites were also obtained by standard thermal sintering at temperature of 1300–1500°C in argon atmosphere or vacuum of the components bonded with organic compounds aqueous solutions containing 0.5–1% boric acid. SEM (Scanning Electron Microscopy) structural-morphological, XRD (X-Ray Diffraction) phase- and EDS (Energy Dispersive Spectrometry) chemical-compositions analysis of the obtained samples has established that transition layers of pentaboride W2B5 are formed on the boron carbide–tungsten interfaces, which ensures component-layers strong bonding.
EPR study of spectral characteristics of REE oxides
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Bataiev Mykola , Barchevska Natalia , Lavrynenko Olena , Bataiev Yurii
Published: August 2024

The intensities of the EPR line for Er2O3 REE samples correspond to the Lorentz line theoretical model [1]. The dependence of the intensity of the lines on the corresponding the gain value has a linear model of the parameters. Dependence plane of the EPR line corresponding to the number of spin domains of the sample, as well shows a linear model of the coefficient value. EPR spectral lines located at 3560G, 1665G, and also at 3050G on the scale of the electromagnetic resonance field refer to the main ion Er3+ rare earth oxide (REE) oxide Er2O3 [2] EPR lines indicate the presence of ions in the corresponding electronic form and refer to the spin of ions and REE oxides. The value of the factors is 1.7554 for the oxide system of Er2O3-CeO2 oxide [1, 2] testifies to the presence of Er3+ ion in the system of the cubic form of Er2O3 oxide and corresponding phase formation of rhombic Er2O3 oxide after heat treatment 1100ºС-1500ºС. The g-factor value of 1.7554 in the EPR spectrum implies the presence of the main one Er3+ ion with an additional shift, which corresponds to the appearance and new formation of an additional one of the phase part of the Er2O3 oxide after high-temperature treatment of the material oxide 1100ºС-1500ºС. The g-factor value of 2.049 is responsible for the proper transition of the main Er 3+ ion with the electronic structure 4f 11 5s 2 5p 6 of the oxide Er2O3 . Spin configuration state for Er3+ oxide Er2O3 is defined in the format 4 I 15/2 . The g-factor value is 0.958 is responsible for the Er2+ -based ion transition with an additional shift that implies the presence of Er ions in different formats in different concentrations in oxides systems based on Er2O3 . The configuration of the ion Er2+ electronic state is determined 4f 12 5s 2 5p 6 and the configuration of the spin state for the Er2+ ion is defined by 3H6.
Effect of chromium carbide on the elastic modulus of modified reaction-bonded silicon carbide
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Pinchuk Mykyta , Gadzyra Mykola , Hnylytsia Ihor
Published: August 2024

The study used industrial silicon carbide powders (3, 28, 80, 100)μm and synthesized nano-sized silicon carbide (0.07μm) in the form of its solid solution of carbon and chromium carbide with an average particle size of 0.2μm. Chromium carbide was synthesized in an induction furnace at 1550°C in an argon atmosphere[1]. Chromium oxide and thermo-expanded graphite (TEG) powders were used as synthesis components. X-ray diffraction was performed on an Ultima IV diffractometer in the Bragg-Brentano focusing geometry (CuKα - monochromatic radiation, graphite bent monochromator on the diffracted beam). The values of the first-order stresses were determined by the sin2(ϕ) method for cubic SiC. The measurements at ψ angles of 10, 20, 25 and 30 degrees were performed by the isoinclination method. Thus, the value of the first-order stresses perpendicular to the sample plane along the [311] crystallographic direction in cubic β-SiC was obtained. When 3 to 10% of highly dispersed Cr₃C₂ is introduced into the composition of the initial batch and infiltrated with liquid silicon in an argon atmosphere, a decrease in the modulus of elasticity is observed, followed by its increase in reaction-bonded silicon carbide (RBSC). The minimum on the curve corresponds to a modifier content of 5%, which corresponds to a modulus of elasticity of 260-280 GPa. This dependence was established on RBSC of different initial fractions of industrial silicon carbide, including synthesized nano-sized silicon carbide. X-ray structural studies have established that the modification process with chromium carbide leads to the occurrence of internal compressive stresses in contrast to the tensile stresses for unmodified RBSC. It is shown that the dependence of internal stresses on the modifier content correlates with the modulus of elasticity. The minimum value of the modulus corresponds to the maximum value of the internal compressive stresses.
The influence of Cr2AlC max phase additives on the mechanical properties and oxidation capacity of the medium-entropy VNiCo alloy.
Authors:   Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine, Saviak Maria ,   Instituto de Tecnología de Materiales, Universidad Politécnica de Valencia, Spain, Vicente Angel , Vicente Escuder , Borrás Amigó
Published: August 2024

FCC high-entropy alloys (HEA) have significant plasticity, deformation, but their yield strength should be higher. The strength of high-entropy alloys is due to lattice distortion due to the different sizes of the atoms. The dimensions of the vanadium atom are significantly different from the dimensions of nickel and cobalt, and if vanadium is introduced into their composition, a significant distortion of the lattice while preserving the fcc structure [1]. Equiatomic alloy VNiCo, showed a yield strength of 1GPa [1]. This yield point is reached in alloys with a grain size of 2 μm. The powder metallurgy method makes it possible to obtain HEA with fine grains. Medium-entropy equiatomic alloy VNiCo was obtained by pressing the initial powders under a pressure of 1000 MPa, followed by sintering at a temperature of 1300º C in a vacuum. Cr 2 AlC MAX- phase powder was added to the mixture of initial powders in the amount of 1, 4 mol.%. Cr 2 AlC was obtained in a single-phase state using mechanical activation in a planetary mill followed by heat treatment of the mechanically activated mixture. Oxidation of samples VNiCo, VNiCo with 1, 4% Cr2AlC was carried out in air at temperature of 900ºC for 1, 4, 8, 24, 48, 96 hours. The results. XRD analysis showed after sintering, fcc structure and an average grain size of 50 μm. Porosity after sintering was 15%. The VNiCo alloy showed a yield strength of 800 MPa, a Young's modulus of 108GPa, and a plasticity of 3%. In the presence of 4 mol. % Cr 2 AlC additives, the yield strength decreased to 620 MPa. The oxidation of the VNiCo alloy corresponds to the power function of film growth. The presence Cr 2 AlC in the alloy slows down the rate of oxidation. The oxidation with 1,4% Cr 2 AlC corresponds to the logarithmic law of oxide film growth. The oxides Ni 3 O 8 V 2 , Ni 0.66 O 3 V 1.34 and Co 0.885 O 2 are formed on the surface of the oxidized VNiCo within 96 hours. On the surface of the alloys containing Cr 2 AlC oxide enriched with Cr is formed
Abrasive wear behaviour of detonation-sprayed (Ti, Cr)C-Ni hardmetal coatings
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Storozhenko Maryna , Umanskyi Oleksandr , Rodriguez Ripoll Manel , Morshch Illia , Haltsov Kostiantyn , Bondarenko Oleksii , Brazhevskyi Valerii , Chernyshov Oleksandr Chernyshov
Published: August 2024

The (Ti,Cr)C-Ni coatings with different binder phase content (17, 25, 33 wt.%) were deposited onto the steel substrate by detonation spraying. The coatings have typical lamellar microstructure with well-bonded splats, which consist of fine (Ti,Cr)C particles and a Ni-based matrix. The coatings' high-temperature (HT) hardness was measured in the 20 - 900 °C temperature range using a hardness tester designed by the Austrian Excellence Centre for Tribology [1]. The hardness of (Ti, Cr)C-based coatings with various Ni content gradually decreased from RT to 500 C, and then a sharper decrease in hardness was observed until a final value of 78-104 HV at 900 °C was reached. The wear resistance of the coatings was evaluated in high-stress abrasion regimes at RT, 600, 800 °C by using an ASTM G65 abrasion tester modified to allow heating of both specimens and abrasive material. Wear rates of the coatings increased with rising temperature to 600 °C and then decreased at 800 °C. The (Ti, Cr)C-33%Ni coating exhibited better abrasive wear resistance compared to the (Ti, Cr)C-17%Ni and (Ti, Cr)C-25%Ni coatings. Abrasive wear of the coatings proceeds through abrasive grooving and the pull-out of splat fragments.
Modeling of the impact process of the bullet core made of hard alloy with a high entropy FeNiCrMoW binder into an obstacle
Authors:   National Technical University of Ukraine “Ihor Sikorsky Kyiv Polytechnic University”, Mykhailichenko Vitalii , Minitskyi Anatolii , Stepanov Oleh , Yurkova Olexandra , Nakonechnyi Serhii
Published: August 2024

In modern conditions, increasing the armor-piercing characteristics of small arms ammunition is an important task. One of the promising ways to solve this problem is to improve the composition of the composite materials from which bullets cores are made [1]. In order to reduce research costs and optimize the design of new products, simulation of product behavior in real conditions is widely used. During the study, a composite powder material of the tungsten carbide and high-entropy equimolar NiFeCrWMo alloy was obtained using the methods of mechanical alloying and vacuum sintering in the ratio of 90 wt. % and 10 wt. % respectively. To obtain a model of the behavior of the material under conditions of intense dynamic loads, a combination of the Johnson-Cook model, which describes the processes of deformation and destruction of the material, the equation of state of stress waves, which characterizes the speed of particles and the speed of stress waves during high-speed deformation, the shear modulus and Poisson's ratio was used. A material model was created using experimentally determined data, which can be used in other similar calculation works for modeling processes of various nature. The process of hitting an armor-piercing bullet into an armor plate was simulated using the Ansys 2020 R2 student edition software using the finite element method. For this purpose, models of the armor-piercing bullet and plates of the required thickness were created and the values of the material parameters were assigned to them. As a result of modeling, it was established that the core of the bullet made of tungsten carbide and high-entropy binder is almost not inferior in terms of strength characteristics to the core of the bullet made of tungsten carbide and cobalt and has similar parameters of penetration ability.
Peculiarities of SPS nanostructured ceramics based on Si3N4 in the presence of varying liquid phase amounts
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Zamula Maryna , Kolesnichenko Valerii , Tyschenko Nadiya , Shyrokov Oleksandr , Stepanenko Artur , Borodianska Hanna , Ragulya Andriy
Published: August 2024

Si3N4 displays excellent tribological and mechanical properties, making it promising for high-temperature applications [1]. To achieve high strength and fracture toughness, the formation of anisometric grains of β-Si3N4 due to polymorphic α→β-phase transformation during sintering of Si3N4 is crucial. This study aims to investigate the phase transformation in Si3N4 and the consolidation of materials using the spark plasma sintering (SPS) method in the presence of varying amounts of liquid phase. The starting mixtures of Si3N4 with varying ratios of oxide additives (1-7wt.% Y2O3 and ~10wt.% SiO2) were prepared by ball milling for 4 hours at 100 rpm [2]. At a SPS temperature of 1800°C, the addition of 1.5wt.%Y2O3 to Si3N4 requires more than 30 min for complete shrinkage. The sample has a remaining open porosity of 6.4%, meaning there is not enough liquid phase for complete densification. Adding 3wt.%Y2O3 allows for consolidation in about 20 min, resulting in almost pore-free ceramics. Adding 7wt.% of Y2O3 reduces the holding time to reach 0% open porosity to 15 min. The analysis of the ceramic microstructure indicates that the average grain size in sintered Si3N4 ceramics increases from 300 to about 500 nm when the quantity of Y2O3 is raised from 1.5 to 7wt.%. This increase in grain size is likely due to a longer exposure time at consolidation temperature. All ceramics have anisometric grains with a length of 1–2μm, corresponding to β-Si3N4 phase. According to the XRD results, no α-Si3N4 phase was detected in any of the sintered samples. However, a significant content (~50vol.%) of the Si2N2O phase was observed. Thus, there is a correlation between the exposure time and the amount of liquid phase formed during sintering, which changes with the amount of Y2O3 additive at a fixed amount of SiO2. Therefore, the significant volume of the liquid phase promotes densification under pressure via the mechanism of rearrangement of Si3N4 nanoparticles to obtain a dense ceramic.
Research on the formation of strength characteristics of synthetic diamond powders
Authors:   V.N. Bakul Institute for superhard materials of the National Academy of Sciences of Ukraine, Oliinyk Nonna , Ilnytska Halyna , Bazaliy Galyna
Published: August 2024

The physical and mechanical properties of the diamond powders, in particular the strength and uniformity of the strength of the powder, primarily affect the efficiency of the abrasive tool. The purpose of the work is to study the formation of powder strength characteristics under the influence of powder flotation separation with preliminary surface activation by iron ions in an ultrasonic field in a liquid. To study the formation of the strength characteristics of powders obtained by flotation separation, powder brand AC 20 with a grain size of 100/80 of the Ni-Mn-C system was chosen. The samples for the study were made by successive two-stage flotation separation into foam and chamber with preliminary activation of the surface of the powder particles with iron ions in the ultrasonic field in the liquid. The strength characteristics of the products, in particular, the strength index under static compression were studied according to the methods of regulatory documents of Ukraine [1]. . It has been established that the application of surface preparation of AC 20 powder with a grain size of 100/80 and flotation separation leads to the possibility of obtaining powders with a strength index under static compression at the level of 17.9-12.3 N, which coincides with the strength interval of the original powder. The homogeneity in strength and the amount of the obtained powders compared to the original powder (taken as 100%) are: foam product 1 - 166% (quantity - 38.5%), foam product 2 - 100% (quantity - 34.6%), chamber product - 66.6% (quantity - 26.9%). Thus, the application of surface activation of powder particles by iron ions in an ultrasonic field in a liquid and flotation separation allows to obtain a powder with increased uniformity in strength (by 66.6%) of its quantity of 38.5% relative to the original powder.
Ab initio study of the effect of substitutional impurities Mo and C on the physico mechanical characteristics of Zr(1-x)Mo(x)B2(1-y)C(2y) solid solutions
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Rozhenko Nataliia , Ovsiannikova Liubov , Kartuzov Valerii
Published: August 2024

Zirconium diboride is a promising material for creating ultra-high temperature ceramics (UHTK), since it is characterized by a high melting point, resistance to oxidation and thermal shock, and thermal conductivity. Varying substitutional impurities allows you to control the properties of ZrB2-based UHTK. An approach for calculating the values of the bulk modulus (B) and hardness of single crystals (HV) of solid solutions based on ZrB2 with substitutional impurities of Mo and/or C based on the results of an Ab initio study of isolated atomic clusters – fragments of their structure – has been developed and applied. The constructed clusters containing 19, 20, 45 and 87 atoms were studied within the DFT methods using Gaussian or GAMESS complexes. Within the developed approach, the cohesion energy of isolated clusters, obtained from first principles, is of decisive importance. The values of B and HV, calculated from the results of Ab initio studies of fragments of various geometries of the ZrB2 structure without impurities, turned out to be B = 197-219 GPa and HV = 22.3-24.8 GPa. The calculation results are in full agreement with experimental data B=218-250 GPa and HV=21.9-27.1 GPa. According to calculations carried out for the Zr(1-x)Mo(x)B2 at x={1/14, 1/6, 1/3, 4/9}, an increase in the Mo fraction contributes to an increase in the B by 2–13% and HV by 4–20% compared to ZrB2. For ZrB2(1-y)C(2y) at y={1/12, 1/8, 1/6, 1/3, 3/8} it is established that the greatest increase in B and HV achieved at y=1/8 (6% and 10% respectively). For the Zr(1-x)Mo(x)B2(1-y)C(2y) compound with both impurities, the largest increments are achieved at x=y=1/6 and amount to 12 and 20 (%) of the B and HV, respectively. The results obtained are in full agreement with available experimental data [1], [2], which means successful validation of the developed approach and its ability to adequately predict the values of the bulk modulus and hardness of new prognosticated ZrB2-based solid solutions.
Electrochemical synthesis, properties and applications of rhenium alloys with iron-group metals
Authors:   Vilnius University, Lithuania, Bersirova Oksana ,   V.I.Vernadsky Institute of General and Inorganic Chemistry NAS of Ukraine
Published: August 2024

The main objective of this study is to develop an efficient method for the electrochemical synthesis of multifunctional (magnetic and electrocatalytic) dense films of Re alloys with Iron-group metals. Heat-resistant alloys, often called superalloys, are based on the iron subgroup with refractory metals (Mo, W, Re) and are capable of operating under extreme temperature and power conditions in aggressive environments. A combination of unique physical and chemical properties makes these superalloys promising for use in high-technology sectors such as aviation, nuclear power engineering, electronics, biomedicine, and heterogeneous catalysis [1-4]. Today, the largest application of materials based on Re alloys is in superalloys, accounting for 70%, especially for jet aircraft engine turbine blades. The primary focus of this study is the Fe-Re system. The electrochemical method for producing Fe-Re alloys enables the obtainment of coatings with controlled chemical composition, structure, and thickness. Several key aspects determine the interest in studying the electrodeposition of Fe-Re alloys: i) depending on the alloy composition, they exhibit either soft or hard magnetic properties; ii) they have potential uses in microelectromechanical systems; iii) Re alloys show electrocatalytic properties in the HER. To achieve the main goal of this research, new stable, non-toxic complex electrolytes for Fe-Re alloy deposition were developed. The dependencies of the chemical composition, current efficiency, and surface morphology on the complex composition of the electrolyte (concentrations of the main components of the bath, their ratio, pH), electrolysis regimes (current density, potential), and the influence of the hydrodynamic regime were studied. Fe-Re coatings with Re content in the alloy ranging from 1 to 90 wt.% were obtained, depending on the concentrations of the main components of the developed electrolyte and deposition conditions.
The correlation between electric and thermoelectric properties in percolative Co/Al₂O₃, Co/SiO₂ and Co/TiO₂ ferromagnetic nanocomposites
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Baibara Oleksii , Bugaiova Marina , Stelmakh Yaroslav , Krushinskaya Larisa , Ievtushenko Arsenii
Published: August 2024

Ferromagnetic nanocomposites (FMNC), consisting of ferromagnetic nanoparticles distributed in a dielectric matrix, behaves as a disordered system in the strongly localized regime [1,2]. Granular structure determines the specific properties of FMNCs, in particular, the metal–insulator transition induced by a change in metal content x, so below percolation threshold, the metallic granules in ferromagnetic nanocomposites are separated by dielectric layers, and hopping transport (HT) to be predominant. From a structural point of view, FMNCs are different from doped materials, therefore, debate arises in how to extend the HT model of doped materials to granular composites. One of the primary concerns focuses on the value of characteristic temperature T₀. Ferromagnetic nanocomposites with Co nanoparticles distributed in various dielectric amorphous matrixes Al₂O₃, SiO₂ and TiO₂ were grown by the EB-PVD method in the form of film with thickness from 0.8 to 10 μm on Al₂O₃ substrates (polycor). The Cо concentration x varied in wide region from 10 to 70 at.% for all matrixes. The temperature dependences of the resistance and thermoelectric properties for FMNCs Co/Al₂O₃, Со/SiO₂ and Co/TiO₂ were investigated in the temperature range of 77 ÷ 290 K. Electric properties of FMNC were fitted by formula ρ =ρ₀exp(T₀/T)n with best fit corresponds to the value of n≈1/2. It has been shown that the value of the characteristic temperature T₀ depends from the concentration of Co and proportional s/d, where s is separations between NPs and d is the diameter of NPs. We have shown, that the temperature dependence of thermoelectric power is well described by an empirical formula α(T)~Tt/T+T where m weakly depends from concentration of Co and the superparamagnetic state of Co nanoparticles, and Tt correlated with characteristic temperature T₀.
Powders produced by the method of mechanochemical synthesis for thermal spraying of coatings containing MAX phases
Authors:   E.O. Paton Electric Welding Institute, Burlachenko Oleksii , Tsymbalista Tetiana
Published: August 2024

To produce protective coatings containing MAX phases, methods of thin films deposition such as physical vapour deposition and magnetron sputtering are mainly used [1]. Such coatings are only a few microns thick and do not meet the requirements for operation in extreme conditions. Thermal spraying (TS) makes it possible to form coatings several millimetres thick. This work is dedicated to developing compositions and technology of producing powders using commercially available starting materials for thermal spraying of coatings containing MAX phases. The technology of mechanochemical synthesis (MChS) by processing mixtures of powders of the compositions 60.9TiC+39.1TiAl, 75TiAl-25SiC, 68.5(Ti,Cr)C-31.5Al, 82Cr3C2-18Al (wt.%) in a high-energy planetary ball mill was used to produce powders for TS. The compositions were calculated to form the most promising MAX phases: Ti3SiC2, Ti2AlC, Ti3AlC2 and Cr2AlC. The MChS process was performed in air during 1.5 hours. The produced powders products of MChS have a conglomerate structure with particles size <50 μm. In the powder product of MChS of the TiAl-TiC system, the synthesis of MAX phases Ti3AlC2 and Ti2AlC occurs; in the powder of the TiAl-SiC system, Ti2AlC, Ti3AlC2, and Ti3SiC2 are synthesized; in the powder of the (Ti,Cr)C-Al system, Ti2AlC and Cr2AlC are synthesized; in the powder of the Cr3C2-Al system, Cr2AlC is synthesized. In addition to the MAX phases and the phases of the initial components of powder mixtures, the MChS products also contain phases of Ti3AlC, Ti5Si3 and Cr5Al8. It is preferable to use high velocity thermal spraying methods such as HVOF and cold spraying to preserve MAX phases in coatings. The interaction time with oxygen and the high-temperature jet is reduced, and coatings phase composition corresponds to the phase composition of the sprayed powder. In the case of using plasma spraying methods, the synthesis of MAX phases can occur directly during spraying and the formation of the coating layer.
Luminescence and UV up-conversion properties of glasses doped with Pr3+ ions
Authors:   Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Poland, Bezkrovna Olha ,   Institute for Single Crystals, NAS of Ukraine, Lisiecki Radosław , Macalik Bogusław
Published: August 2024

The relevance of the synthesis of materials that emit effectively in the UV region of the spectrum is due to the need to create self-sterilizing surfaces without the use of ultraviolet lamps [1]. Materials and surfaces created on their basis that have the ability to absorb photons of ambient or sunlight and next convert them into photons of the bactericidal range of the spectrum (220-280 nm) can contribute to a constant reduction in the content of adsorbed microbes. Pr3+ ions have an advantage as activator ions for creating such materials, since they effectively luminesce in a wide range of wavelengths, including in the UV-C region (200-280 nm) [2]. Vis-to-UV up-conversion (UC) of Pr3+ ions corresponds to the absorption of blue or violet light (430-490 nm region) through 3H4 → 3PJ transitions with followed by the UC of the excitation energy [3]. In addition, Pr3+ ions as an activator can produce greenish-blue or red emission due to its excited energy levels 3P0 or 1D2 . We chose a stable glass-based SrO-CaO-MgO-SiO 2 for doping of Pr 3+ ions. Luminescence in a wide spectral range, absorption, and excitation of luminescence were measured and the luminescence lifetimes were estimated. We obtained up-conversion luminescent radiation in the ultraviolet region in the SCMS:Pr3+ glass upon excitations at 444 nm. The up-converted luminescence spectrum of Pr 3+ -doped glass was in the 230-330 UV spectral region with the maximum at 275 nm. Intense luminescence of Pr3+ ions in the glasses studied was also observed in the visible and near-IR regions. It was found that significant non-radiative energy transfer occurs between Pr3+ ions, especially in glasses containing higher concentrations of luminescent ions. Synthesized glasses can be suitable as solid state materials for a variety of photonic applications, including the development of UV self-sterilizing surfaces.
Influence of additives of bronze powder Cu-10Al-4Fe on the tribological characteristics of coatings based on the Ni-C system
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Kushchev Oleksiy , Umanskyi Oleksandr , Terentiev Oleksandr , Varchenko Victor , Chevichelova Tetyana , Brazhevskyi Valery , Chernyshov Oleksandr , Kostiunik Ruslan
Published: August 2024

Use of plasma coatings of nickel-clad graphite powder (Ni-C) is promising for use as abradable sealing materials [1, 2, 3]. To expand the areas of application of Ni-C powder coatings, it is advisable to use them in combination with bronze [4]. For this purpose, it is proposed to use bronze powder Cu-10Al-4Fe, which has proven itself well as an antifriction material. The purpose of this work was to study the influence of the amount of bronze additives Cu-10Al-4Fe on the tribological characteristics of coatings. Plasma coatings were applied in an open atmosphere on a UPU-3D installation in a protective chamber using a Metco F4-MB plasma torch. Plasma-forming gases - mixture of argon and hydrogen. Coatings were obtained from Ni-C powder, as well as mixtures of Ni-C and Cu-10Al-4Fe powders with bronze additives in amounts of 5, 25 and 50 wt. %. Tribological tests were carried out on an M-22M friction machine. It has been established that with increasing bronze content, the abrasion resistance of the coating increases. Introduction of Cu-10Al-4Fe powder in an amount of 50% wt. into the main Ni-C powder led to a significant (~ 7 times) increase in the wear resistance of the resulting coatings. Additive 5% wt. Cu-10Al-4Fe into Ni-C powder leads to a decrease in the friction coefficient from 0.60 to 0.54. On samples of Ni-C+ 25% Cu-10Al-4Fe, a decrease in friction coefficient to 0.50 was observed Increasing the bronze content to 50% wt. in the powder composition made it possible to reduce the friction coefficient to 0.35. Conclusions. With an increase in the bronze content of Cu-10Al-4Fe to 50% wt. in the composition of Ni-C based powder, there is a tendency to improve the basic tribological characteristics of coatings, namely, wear resistance increases by 7 times, and the value of the friction coefficient decreases from 0.60 to 0.35. This makes it possible to significantly expand the scope of application of the Ni-C +Cu-10Al-4Fe material in aviation and space technology.