bluuebunny/crossref_metadata_2025 huggingface dataset:
Micro-photoluminescence analysis of the redistribution of NV and SV defects in individual CVD diamond microcrystal with the distance from Si substrate
Authors:   V. Ye. Lashkaryov Institute of Semiconductor Physics of National Academy of Sciences of Ukraine, Nasieka Iurii ,   National University of Life and Environmental Sciences of Ukraine, Strel’nitskij Volodymyr , Horobei Oksana , Lozinskii Volodymyr , Temchenko Volodymyr
Published: August 2024

The vertical distribution of NV-, NV0 and SiV defects in the individual 60 µm height diamond microcrystal of PECVD film grown on Si single crystalline substrate was studied using the micro-photoluminescence method. The presence of N-related defects in the studied crystal is caused by the imperfection of the PECVD vacuum system [1]. The excitation of micro-photoluminescence signals was carried out using the 2.54 eV (488 nm) Ar-Kr laser line focused by the microscope 100x objective in the spot with the diameter equal to 2 µm. The changes in the shape of room-temperature micro-photoluminescence spectra of diamond micro-crystal measured, depending on the position of focused laser excitation spot along the crystallite height, were analyzed. All spectra were deconvoluted on the elementary Lorentzians including zero-phonon luminescence bands related to each NV-, NV0 and SiV defects and their phonon replicas. Comparing the emission bands intensity the area under the corresponding elementary contours was calculated. It was obtained that the processes of SiV defects formation non-monotonically depends on the distance from Si substrate. At the distances of 2 – 20 µm the concentration of SiV defects increases sharply, then at the distances larger than 20 µm the number of SiV defects decreases. The concentration of NV- and NV0 defects monotonically increase with increase in the distance from the Si substrate. The predomination of SiV defects formation at the beginning stages of the crystal growth is explained by the substantial density of carbon divacancies required their formation. With increase in the distance from the substrate the crystalline perfection increases, the number of carbon divacancies decrease and the processes of NV- and NV0 defects formation dominates. The obtained results are important for the developers of CVD diamond film based sensors, which performance is defined by the concentration and distribution of NV-, NV0 and SiV optical centers.
Finite element analysis of scratch test of films on substrate
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Valeeva Irina , Goroshko Ivan
Published: August 2024

Scratch test is an important investigation method which is used to evaluate mechanical properties of materials and structures, adhesion of coatings, etc. The stress distribution in the sample is the most important information, which affects its deformation, damage and fracture of the sample material. Simulation of scratch tests of samples with refractory, hard and other coatings or different film-substrate systems allows us to understand which type of load occurs between the substrate and the coating, which type of load affects delamination of coatings [1]. The aim of this study is to implement finite element simulation of the elasto-plastic deformation during scratch test using ANSYS software. The scratch tests were performed to study the adhesive properties of films on substrates. The test was performed with a linearly increasing force of 13 mN/s applied vertically to the indenter. The force was increased until the load reached 500 mN. At the same time, the Rockwell indenter was moved at a speed of 10 μm/s in the horizontal direction. The radius of the Rockwell indenter was 10µm. Finite element analysis of scratch test was applied to film-substrate systems. Large deformation in scratch zone causes essential difficulties during finite element analysis that related to mesh distortion, which leads to an abort of solution process. To overcome these computational difficulties, researchers use special approaches and software. Nonlinear mesh adaptive technology was applied to overcome the distortion of finite elements. The fields of displacement, stress, and strain in the film-substrate systems were obtained as a result of scratch test simulation. Numerical simulation allows us to study the influence of each parameter on the scratch test results. Finite element analysis can explain how the results of scratch test depend on the mechanical properties of the film-substrate systems.
Features of sintering compositions based on titanium with refractory compounds
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 , Mamonova Alevtina , Molchanovska Galina
Published: August 2024

Titanium-based powder alloys are of particular interest for aerospace engineering due to their high specific strength, corrosion resistance and other properties. To increase wear resistance, it is usually necessary to introduce solid phases and compounds that ensure heterogenization of the structure and, accordingly, localize the development of plastic deformation. The materials that most effectively resist wear are those that form dissipative structures during sintering [1-3]. They arise in complex physicochemical systems due to the competition of chemical reactions that are observed during interaction with refractory compounds with the participation of unstable chalcogenides, which are sources of excitation of autowave processes. Being constantly excitable systems in which continuous transfer is observed due to self-organization processes, it should be expected that activation of sintering will be observed in such compositions. Molybdenum diselenide and disulfide were introduced into titanium compositions with compounds of various natures. Thus, when sintering in systems with titanium carbide, titanium boride and titanium nitride, the introduction of diselenide and molybdenum disulfide leads to significant compaction. When they are introduced into compositions with covalent compounds (B4C, BN, SiC, Si3N4), activation of titanium-based compositions is observed both in certain concentration regions of covalent compounds and chalcogenides. Threshold concentrations are observed at which shrinkage gives way to growth. This is due to the activation of the process of interaction of the covalent compound with titanium. In this case, corresponding titanium compounds are formed with elements that form one or another covalent compound, for example borides, nitrides, carbides, and auto-dispersion of the material structure occurs.
Effect of heat treatment on the structure and properties of tungsten cathodes produced by pressing
Authors:   The E.O.Paton Electric Welding Institute, NASU, Krushynska Larisa , Tkach Roman , Olexander Yukalchuk Olexander Yukalchuk
Published: August 2024

In vacuum metallurgy, electron beam guns (EB guns) are widely used, in which tungsten thermal cathodes (W-cathodes) are the source of electrons. The problem of improving technological processes for producing W-cathodes from the point of view of improving the cost/efficiency criterion remains relevant. The purpose of the work is to study the effect of vacuum heat treatment (HT) on the structure and properties of flat W-cathodes obtained by hot pressing tungsten wire blanks [1]. Comparative studies of the structure (by optical and scanning electron microscopy), mechanical (microhardness measurements) and operational properties (during tests in EB guns) have been carried out. The “as delivered” W-cathodes are plates 0.6 mm thick, 3 mm wide and 100 mm long. It was found that the microstructure of the cathodes in the delivered state is elongated grains, the average width is 3...5 µm, the length is 20...40 µm, the microhardness is at the level of 5.4...5.6 GPa. To study the recrystallization process in the W-cathodes, vacuum HT was carried out in the range of 800...1200°C for a duration of 20 to 120 minutes. It has been established that vacuum HT in the range of 800...1150°C does not have a significant effect on the structure and properties of W-cathodes. Starting from 1200°C, a mixed microstructure is formed, which is a mixture of initial and equiaxed recrystallized grains, the number and size of which increases with increasing exposure time at this temperature. Microhardness decreases to 4.7...4.9 GPa. It has been established that to improve the performance characteristics of W-cathodes, a mixed structure must be formed in them: up to 10-30% - equiaxed recrystallized grains, and at least the volume of the cathode material must retain the original structure. The optimal HT regime has been determined. The durability of cathodes heat-treated according to this mode is at least 50 hours, which corresponds to the level of durability of the best foreign cathodes.
Mechanical behavior of SOFC electrolytes based on zirconium dioxide
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Brychevskyi Mykola
Published: August 2024

The materials based on zirconium dioxide are popular to using for high-temperature SOFCs[1]. In particular, there are occurs due to flexibility of phase and structural changes and opportunity of symmetry raising by replacing the four-valent zirconium ion with a three- or five-valent ion. This leads to the formation of an additional sublattice of oxygen vacancies [2]. But mechanical behavior is of critical importance too for a carrier-electrolyte technological scheme. Since increased mechanical properties allow to manufacturing of thinner electrolyte, which will proportionally reduce the total resistance as of the component and the device as a whole [3]. Three different starting powders of zirconium dioxide stabilized with 10 mol. % scandium oxide and 1 mol. % cerium oxide were used. One-sided pressing with follow by isothermal sintering in air in the temperature range of 1200-1550 ℃ during 1,5 hours was used to produce of ceramic specimens. The base research methods were biaxial strength studying and SEM of fracture surface. It was shown that using of initial powders to allow producing the various type ceramics with significant structure changes: porosity and sizes of effective structure components, and implement all possible fracture micromechanisms: interparticle, intergrain and cleavage fracture. The produced materials can be classified by changes of structural features with increasing of thermal influence, which are manifested with fracture surface studying. Type I material is porous, has a low recrystallization rate and was fractured exclusively by cleavage. Type II is a dense material, with has a high rerycstallization rate and has fractured by cleavage. Type III material has a high rapid recrystallization rate and intergranular fracture. It was found that the shift of activation energy of densification and grain size grow was taking place in the temperature range of 1300-1400 ℃ and was coincided with the dominant fracture micromechanism changes.
The effect of preliminary grinding of the charge on the structure and properties of hot-forged heat-resistant alloys of the Nb-Ti-Cr-Al-Mo system
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Marych Myroslav , Rokytska Olena , Golubenko Alex
Published: August 2024

The development of alloys based on niobium is a promising direction for the creation of heat-resistant alloys with a low specific gravity. Therefore, the task was set to investigate the possibilities of obtaining the alloy by methods of powder metallurgy, in particular hot forging [1-2]. Ti, Al, Mo, Nb, and Cr powders were used as starting materials. 2 types of powder mixtures were formed: without grinding and with preliminary grinding. Grinding of the charge was carried out in a planetary mill for 15 min.Consolidation of powder blanks by the method of hot forging (HF) was carried out on an arc stator press at a temperature of 1200 °C. The annealing of the samples after HF was carried out in a vacuum electric furnace at a temperature of 1600 °C. As a result of the work, powder polycomponent alloys based on niobium were obtained. The technological operation of preliminary grinding of the charge had a significant impact on the microstructure and properties of the alloys. It was established that preliminary grinding of the charge within 15 min. significantly grinds the elements of the structure after hot forging. Porosity decreases due to a more active surface of the particles after grinding. Imaging in the characteristic rays shows that the elements of the alloy are distributed evenly. This indicates a greater degree of diffusion homogenization of the alloy. Grind the mixture of powders for 15 minutes. brings the compressive strength of the hot-forged material closer to the values of the cast one at temperatures up to 800 °С, even with greater porosity of the former. The yield strength of hot forged alloy of NbTiCrAlMo (with grinding) at 800 °С is about 700 MPa, which is almost 2 times more than that of a similar alloy without grinding. Therefore, the production of NbTiCrAlMo alloys by powder metallurgy methods eliminates the problem of element liquation, and preliminary grinding of the charge significantly increases the strength of the obtained alloys.
Influence of time and power of microwave radiation on the heating temperature of composite materials based on silicon carbide
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Davidchuk Nadia , Gadzyra Mykola
Published: August 2024

Absorption of microwaves by various materials is accompanied by heating of varying degree [1]. The purpose of this work is to study the dependence of the heating temperature of briquetted SiC powders on the microwave radiation time and power. Study of the influence of time from 1 min. up to 3 min. and power from 350 W to 700 W on the heating temperature of the investigated powder materials was carried out due to the absorption of microwave radiation with a frequency of 2.45 GHz . Six samples of silicon carbide synthesized under different conditions were used: 1 – synthesized from electrode graphite and Si; 2 – synthesized from petroleum coke and SiO₂; 3 – synthesized from thermally expanded graphite (TEG) and Si; 4 –ground ceramics infiltrated TEG by Si at 2000°С; 5 – synthesized from TEG and Si and purified in HF; 6 – ground reaction-bonded silicon and boron carbide (SiC-B₄C-Si). The weak dependence of the heating temperature on the time of microwave action at a power of 350 W for samples 1, 2 and 4 is due to the presence of crystalline silicon in the compositions of synthesized silicon carbide powders. The monotonous increase in the heating temperature of samples 3.5 and 6 from the time of microwave exposure is evidence of their high dielectric properties in a wide temperature range. An increase in temperature over 950°C during of 3 minutes is a main evidence of cubic modification silicon carbide in the form of a solid solution of carbon in silicon carbide. Dissolved carbon in the form of planar carbon clusters with sp3 hybridization of atoms leads to an increase in dielectric properties. The phase composition of sample 6 is characterized by the presence mainly of hexagonal 4H-SiC, as well as crystalline silicon. However, the presence of silicon does not affect microwave absorption. A monotonous increase in temperature up to 750°C is observed during 3 minutes.
Residual thermal stresses in cemented carbide with mesostructure
Authors:   V.M. Bakul Institute for Superhard Materials, Litoshenko Nataliya
Published: August 2024

The development of composite materials with mesostructures is a relevant task today [1, 2]. One of the effective methods to increase the workability of products made of WC–Co, WC–Ni, TiC–WC–Co hard alloys is to form a mesostructure in them, which will make it possible to improve physical and mechanical properties and simultaneously achieve high wear resistance and fracture toughness [3], as well as double the value of the strength limit and four times the fracture deformation during compression tests. In hard alloys, the meso-structure consists of mesoelements - an ensemble of carbide particles cemented by a binding metal and a metal phase. The properties of such compositions depend on the composition, structure and state of the mesoelements and the matrix. Carbide products with a mesostructure are promising in the mining industry and mechanical engineering. In particular, using them in hard alloy elements of friction pairs and sealing units, it is possible to achieve the most optimal ratio of wear resistance and fracture toughness. The level of residual thermal stresses in granules and interlayers of mesostructural hard alloys (WC–Со)gran–Со, (WC–Ni)gran–Ni, (TiC–Со)gran–Со, (TiC–Ni)gran– Ni , arising during its cooling from the sintering temperature to room temperature was established by analytical methods. The dependence of local stresses on the content of the binder phase in the granule and hard alloy was studied for a layer thickness equal to 10% of the radius of the granule. With an increase in its content from 15 to 30 wt%, compressive stresses in a WC carbide with a binder content of 3...25 vol% increase from –25 to –366 MPa, and the tensile stresses in the Co layer change from 1134 to 687 MPa. The tensile stress values in the matrix layers are lower than in standard hard alloys of similar brands, in particular for (WC–Ni)gran–Ni – by 69%, and for (WC–Со)gran–Со – by 30%.
Ceramic material based on TiB2-FeSi using the reaction sintering method under SPS conditions
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Derev'yanko Oleksandr , Istomina Tetyana , Lytvyn Roman , Myslyvchenko Oleksandr , Verbylo Dmytro , Zgalat-Lozynskyy Ostap
Published: August 2024

When creating new heterogeneous structural materials based on TiB2, the addition of binding components [1]. This has a positive effect on wear resistance, strength, and crack resistance. One of the promising directions for the consolidation of ceramics based on TiB2 is the use of spark plasma sintering (SPS) technology. In order to obtain a ceramic composite material based on the TiB2-FeSi composition, a mixture of powders with a composition (vol. fr.) of 27%TiH1.5-62%TiB2-9%TiSi2-2%Fe was used [2]. The SPS process was performed without the use of a protective chamber with a vacuum/gas environment [3]. The total duration of electromechanical processing was 210 s. The required temperature level of 970 С was reached in the first 60 s. The last 150 s was spent isothermally holding at the specified temperature. The total electric current through the mold was constant after 60 s, and was kept at 2.0 kA, as was the temperature. The mechanical load during SPS was at the level of 35-40 MPa. X-ray structural analysis showed a difference in the composition from the initial one, which was obtained after mixing the components. Vickers HV microhardness measurement at a load of 100g showed an average value at the level of 19.7-22.39 GPa. Rockwell hardness was 75-77 HRC units. Ceramic fracture occurs at 112.2 MPa per bend without, in fact, deformation of the tested material. Research has shown that it is quite possible to obtain ceramics based on TiB2-FeSi by the SPS method without the use of a vacuum, gas, etc. environment and in a fairly short period of time in comparison with the known methods of obtaining ceramics based on TiB2. Also, in contrast to hot pressing in a vacuum, a rather small mechanical load is used for pressing. Under such insignificant conditions of electro-mechanical load and a short SPS time, sufficient mechanical characteristics of ceramics were obtained, which allow its use as a cutting tool or a sliding body in friction pairs.
Characteristic features of formation of structure, composition, and properties of films of refractory compounds
Authors:   Institute of Materials Science, Slovak University of Technology in Bratislava, Slovak Republic, Goncharov Oleksandr ,   Sumy State University, Ukraine, Kolinko Ivan , Yunda Andrey , Goncharova Svitlana , Shyrokorad Dmytro , Kornich Gregori
Published: August 2024

Functional coatings of refractory compounds, i.e. transition metal nitrides, carbides and borides, having unique physical and mechanical properties, are widely used in various industries [1,2]. Nanocomposite nanostructured coatings of transition metal nitrides and borides due to their high melting point are usually deposited by ion-plasma and magnetron sputtering methods [3,4]. Research of the formation of structural characteristics, physical and mechanical properties of transition metal nitride and boride films, obtained by RF and DC magnetron sputtering, is carried out in this work. It is shown that optimal energy conditions at the deposition are resulted in the formation of a columnar structure (fibrous) and a growth texture of given films. The growth texture (111) with a crystallite size of 10-12nm is formed for both single component (TiN, HfN, etc.) and multicomponent (Ti–Zr–Si–N) films of transition metal nitrides. At the same time, the hardness of multicomponent films is higher compared with single-component TiN and ZrN films. The corresponding tendency is preserved for high-entropy ulticomponent nitride coatings (TiHfZrVNb)N. Depending on the deposition conditions, the texture (111) is formed. In this case, the nanohardness increases up to 44,3GPa, that is related to the characteristics of the resulting electronic structure. Transition metal multicomponent and high-entropy (Hf,Ta,V,W,Zr)B2 diboride films are characterized by the formation of a columnar structure, and a growth texture in the (00.1) plane. It is noted that the physical properties of the resulting diboride films are identical. The nanohardness and the elastic modulus are varied within 44–48GPa and 400–500GPa, respectively, for both mono- and multi-component films.
Electrical conductivity of nanocomposite FexOy(Fe)/SiO2(Si) films
Authors:   Institute of High Technologies, Taras Shevchenko National University of Kyiv, Pylypova Olha , Bratus’ Oleh , Kizjak Anatoliy , Antonin Serhii , Muryi Yaroslav , Evtukh Anatoliy
Published: August 2024

Nowadays the synthesis and investigation of the materials, containing metal and semiconductor nanoparticles in amorphous matrix are of the great interest for the material engineering and also various applications. Particular attention is given to the nanocomposites in which nanosized particles of soft ferromagnetic alloys are randomly distributed in dielectric matrix [1]. The investigation of electrical conductivity and its dependence on the technological processes is еру necessary condition for many applications. The nanocomposite FexOy(Fe)/SiOx films were deposited by Ion Plasma Sputtering (IPS) technique at sputtering of combined silicon-iron target in O2+Ar ambient at 150 °C on Si substrates. Among the varying parameters of deposition process were ratio of Fe and Si parts of target, content O2 in gas mixture, and film thickness. In the second stage, FexOy(Fe)/SiOx films were annealed in the argon atmosphere at the temperature of 1100 °C during 60 min to form nanocomposites. Current-voltage characteristics of MIS structures containing FexOy(Fe)/SiO2(Si) films were measured in the temperature range of 95–340 K using the Source Meter 2410 Keithley. As a result of the study of the electrical characteristics of nanocomposite films on direct current, it was established main pequliarities of electron thatsport through the nanocomposite FexOy(Fe)/SiO2(Si) films.For all films under investigation the current for non-annealed films is smaller than for annealed ones in the region of the applied electric fields E < 2.0×106 V/cm, but the ratio becomes the opposite with the increase of the applied fields higher E > 2.0×106 V/cm.Some electron transport mechanisms are realized in dependence on the applied electric field, namely: quadratic current-voltage dependence, the Child-Langmuir law, space charge limited current with shallow traps in bandgap, Poole-Frenkel and Fowler-Nordheim mechanisms.
Supercritical fluid synthesis and structure of C96 zeolite-like carbon allotrope
Authors:   M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine, Pokropyvnyi Oleksii , Smolyar Anatolii
Published: August 2024

Since the beginning of the 21st century, we have entered the era of carbon allotropes. Among this wide spectrum of carbon structures, only four allotropes of carbon with cubic symmetry are currently known. Two of them are the well-known diamond and fullerite. Others are «cubic graphite» and cubic C8. Their structures were proposed as LTA and SOD carbon zeolites, respectively. Other possible structures are only hypothetical. In this report the structure of «cubic graphite» is reinvestigated based on a new electron diffraction experiment and ab initio calculations of carbon zeolites from an available structure database. Carbon microcrystals associated with the «cubic graphite» phase were synthesized using the fluid synthesis method at a pressure of up to 200 MPa and a temperature of 500-700 oС from carbon black as a precursor. According to the results of experiments, methods of experimental electron and X-ray diffractions, as well as ab initio calculations, it is proved that the carbon phase is cubic with lattice parameters ~0.895 nm and space group Im-3m [1]. The crystal structure is proposed as carbon C96 zeolite with KFI topology consisting of 96 carbon atoms per unit cell with sp3 hybridization and sp3/sp2 bond types. This type of zeolite consists of eight 6-6 prisms as secondary building units with T-atoms as individual carbon atoms instead of SiO2 in true zeolites. The hybrid structure is more stable by 0.22 eV per atom. New phase has a density of 2.67 g/cm3 and a high hardness up to 10-20 GPa.
Thermodynamics and Chemical Ordering of Glass-Forming Liquid Cu–Co–Ni–Ti–Zr, Cu–Co–Ni–Ti–Hf Alloys
Authors:   Donbas State Engineering Academy, Ukraine, Agraval Pavlo , Dreval Liya , Vodopyanova Anna
Published: August 2024

Metallic glasses have attracted much attention from materials science researchers. At the same time, finding new compositions of multicomponent metallic glasses by trial-and-error method requires significant costs and efforts associated with conducting experimental research. Therefore, to search for new promising compounds, scientific forecasting methods should be used, among which the thermodynamic approach occupies an important place. In this work, the results of calculating the temperature-composition dependence of the thermodynamic mixing functions of equilibrium and supercooled Cu–Co–Ni–Ti–Zr and Cu–Co–Ni–Ti–Hf liquid alloys are presented, and the chemical short-range ordering in them, are discussed. The obtained results were used to predict the composition regions of glass formation. A database containing interaction parameters for boundary binary and ternary systems was used for calculations of thermodynamic properties of multicomponent liquid alloys. The phenomenological Associate Solution Model (ASM) is used to describe the thermodynamic mixing functions of glass-forming liquid alloys. The degree of chemical short-range ordering in liquid alloys is estimated in the framework of ASM as the total mole fraction of associates in the solution. Glass-forming composition regions are predicted using the empirical rule, according to which amorphization by quenching proceeds successfully for melts in which the total molar fraction of associates exceeds 0.3 at the glass transition temperature. The analysis of predicted composition regions of amorphization of the melts of the Cu–Co–Ni–Ti–Zr and Cu–Co–Ni–Ti–Hf systems allows us to specify the certain total concentration of metals, which are donors (Ti, Zr, Hf – IVB metals) and acceptors (Co, Ni, Cu – Late Transition Metals, LTM) of electrons in the melt. The composition of rapidly quenched metallic glasses of the Cu–Co–Ni–Ti–Zr and Cu–Co–Ni–Ti–Hf systems must be fulfilled the conditions ΣxLTM > 0.25 and ΣxIVB > 0.28.
Game-changing key materials in the future sustainable economy
Authors:   National Institute of Materials Physics, Badica Petre
Published: August 2024

Human history has periods defined by a game-changing key material, e.g. stone, bronze, iron, silicon, polymers, etc. although other materials were also used at the same time. What should the key materials of the future look like? To answer this question we assess in a multidisciplinary manner ancient materials revealing unexpected features specific for modern materials, thus showing that learning from the past can be rewarding. As a case study we also analyze multifunctional properties of MgB2, a 2D-like compound, and learn on its potential as a sustainable material based on our results and literature data.
Light dense materials of the AlB12-SiC system
Authors:   V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, Barvitskyi Pavlo , Prikhna Tetiana , Lokatkina Anastasiia , Muratov Valeriy , Moshchil Victor , Karpets Myroslav
Published: August 2024

The work describes the creation hard AlB12C2-based ceramic materials under by hot pressing and by high pressure-high temperature conditions. The high mechanical performance of the materials we obtained are similar to those of boron carbide, which can be explained by the structural features of B4C and AlB12/ AlB12C2 [1], namely the presence of almost identical structural elements - regular icosahedrons of boron atoms. The possibility of modifying the structure and properties by introducing additives became the reason for conducting research. To obtain the material, sintering of a powder mixture of of αAlB12 and SiC was used. Relatively cheap nanopowders (50-150 nm, with a specific surface area of 21-15 m2/g) α-AlB12 synthesized by PhD. V.B. Muratov (IPM NASU) were used in work [2]. The hot pressing at 30 MPa 1800-1970 оC of two compounds from α-AlB12 nanopowder with 15 (I) and 20 (II) wt.% SiC addition can result in formation of ceramic elements having according x-ray an-is 88 wt.% AlB12C2-12 wt.% Al2O3-SiC(additives) and 85.5 wt.% AlB12C2-14.5 wt.% Al2O3-SiC(additives) phases compositions respectively. Both materials turned out to be light (density rI=2.6 and rII=2.36 g/cm3) and quite dense (porosity PI=5 %; PII=8 %). Samples of the first (I) material were demonstrated HV - 23.3 GPa hardness, fracture toughness K1c - 5.0 MPa•m0.5 and samples of the second (II) material showed HV - 25.6 GPa, K1c - 5.7 MPa•m0.5 accordingly. The sintering under high-pressure apparatus at 4,1 GPa generally allows to reduce sintering temperatures. At a reduced temperature to 1700 oC at 4.1 GPa and holding for 8 min, the samples were perfect on the outside, but with a large amount of internal stress. This material had hardness HV - 25.2 GPa and fracture toughness K1c - 4.2 MPa•m0.5 at density rIIІ=2.75 g/cm3 and porosity PIII=5 %. High performance characteristics of the obtained composites can be explained by the formation of solid solutions in the structure.
Phase diagram of the Tb3Sc2Al3O12–TbScO3 system
Authors:   ENSEMBLE3, Centre of Excellence, Lakyza Serhii , Tomchzyk Monica , Korol Jaroslaw , Pawlak Dorota-Anna
Published: August 2024

Eutectics present the unusual characteristic of being at the same time a monolith and a multiphase material. They have the potential for optical, electronic and magnetic applications. Their properties can be divided into two categories: additive properties and product properties. The additive properties depend on volume fraction and spatial distribution of the phases, while the product properties depend on interaction between the phases and depend on periodicity and the size of the phases. The Tb3Sc2Al3O12–TbScO3 (TSAG-TSP) eutectic is interesting optically active material in which both radiative and measured lifetimes of 5D4 manifold of Tb3+ ions are longer than in bulk TSAG and TSP crystals. These eutectic materials have a high potential for photonic applications. The authors [1] grew TSAG single crystals by micro-pulling down method and found the formation of areas of binary eutectic TSAG-TSP at the edge of TSAG single crystal. The reason was the composition deviation during the growing process. So the quasibinary section TSAG-TSP was stablished in the system Tb2O3–Sc2O3–Al2O3. Then the directional solidification of TSAG-TSP eutectic was performed [2], but the coordinates of this eutectic was not established and bulk material with primary TbScO3 crystals was obtained. At the present time we have no information about phase diagram of this system, so the construction of it is the purpose of given investigation. The bulk directionally solidified µPD crystal was analyzed by DTA, SEM+EDS methods and coordinates of TSAG-TSP eutectic was established (1805 °C, 25 mol.% TbScO3). TbScO3-based solubility area does not exceed ~1 mol.%. TSAG-based solubility was not determined.
New composites based on aluminium alloy grinding waste for post-printing machines
Authors:   National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Roik Tetiana , Gavrysh Oleg , Maistrenko Iuliia
Published: August 2024

Post-printing equipment contains many antifriction parts made of cast aluminum alloys that work at sliding speeds up to 2.0 m/s and loads up to 3.0 MPa with liquid lubrication. Such parts often have unsatisfactory functional properties due to unstable lubricant supply to the contact area or other emergencies [1]. This leads to damage to the part, the unit, and the post- printing equipment as a whole. The use of grinding waste has become an alternative for creating new effective aluminium antifriction composites. The objective of the study is to determine the structure and properties of new antifriction composites based on grinding waste of aluminium alloy D16+(6.0‒8.0) wt.% MoS2. The initial D16 alloy grinding waste was subjected to regeneration: cleaning from abrasives and drying. D16 alloy powders were mixed with (6.0-8.0)wt.%MoS2, cold-pressed at 550 MPa, and followed by hot pressing at 300 MPa and 400°C to minimise porosity. The structure was studied using metallographic, scanning electron microscopes and X-ray spectroscopy [1]. The tribological tests were carried out on the VMT-1 friction machine at a speed of 1.0-2.0 m/s and friction pair loads of 2.0-3.0 MPa in pair with a 40Kh steel counterface (HRC 47-49). The microstructure is a metal matrix (Al α-solid solution) based on the D16 aluminium alloy regenerated grinding waste and uniformly distributed MoS2 solid lubricant. Antifriction tests showed the advantages of the new composite made from the D16 alloy waste over cast aluminium alloy D16. The friction coefficient of the new composite was 0.16-0.18, and wear intensity was 32-37 µm/km in tribological tests at 3.0 MPa and sliding speed of 2.0 m/s. While the cast alloy D16 at operation without lubrication had a friction coefficient of 0.38-0.39 and wear intensity of 75-80 µm/km. The developed technology provided a high level of functional properties and stable operation of the composite in self-lubrication mode.
Simulation of densification of ceramic materials based on boron carbide during high-speed sintering under pressure
Authors:   V. Bakul Institute for Superhard Materials, Dutka Vasyl' , Kulich Vitaliy , Borymskyi Oleksandr
Published: August 2024

Strength characteristics of ceramic materials, obtained in a result of sintering under pressure, significantly depends on their density. The sintering regime parameters as well as grain growth affect the density of the sintered material. In order to achieve high density, it is necessary to minimize grain growth. Therefore, it is important to predict the evolution of the sample material density and grain growth at the final sintering stage. At the present time, a number of densification models of ceramic powders during sintering under pressure have been developed. For the application of these models, it is important to determine their parameters. One of the densification models is the Skorohod-Olevsky model. Since the densification process of powder samples by high-speed sintering under pressure (HSSP) is very fast, the creep of the crystal lattice and grain boundaries can be considered as the dominant densification mechanism. Hence, the densification model can be limited to only the component that describes the mechanism of generalized creep. Therefore, the number of model parameters that need to be identified for simulation of densification is reduced. The purpose of this work is to apply a linear regression approach to determine the parameters of Skorohod-Olevsky densification model of powder samples based on boron carbide during HSSP according to experimental data, and to model the powder materials compaction using these parameters. The parameters of material densification model were determined using the results of HSSP-experiments of powder samples with two compositions based on boron carbide. A computer model of the densification of viscous porous materials was developed, taking into account grain growth. Modeling of the densification of powder materials during HSSP-process was carried out. It is shown that at noticeable grain growth of the sample material during HSSP, in order to obtain a dense composition it is necessary to increase the holding time. It is also shown that in this case, one of the alternatives to increasing the exposure time is the increasing of the working pressure.
Preparation of composite powders based on titanium-chromium diboride by the method of plasma spheroidization for gas-thermal spraying and surfacing of protective coatings
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Konoval Volodymyr , Skulskyi Mykola , Liutik Mykola , Bondarenko Oleksiy , Gal'tsov Konstyantyn , Avetisian Arutiun , Poliarus Olena , Umanskyi Oleksandr
Published: August 2024

To obtain the coatings with various special properties, such as heat- and wear resistance under friction conditions at high speeds, loads and the absence of lubrication, refractory compounds and composite materials based on them in the form of powders are used. The properties of composite powders, as well as coatings obtained from them, depend on the method of their production [1]. The goal of the work is to obtain composite metal-ceramic powders with good technological and mechanical properties for gas-thermal spraying and surfacing of coatings. Powder mixtures (Ti,Cr)B2 –NiAlCr, (Ti,Cr)B2 –AlN(SiC)–NiAlCr were obtained by mixing in a planetary mill. The particle size was ~3÷12 µm. Subsequently, the powder mixtures were conglomerated using organic binding materials, after which the particle size was ~40÷90 µm. These powders were passed through a plasma jet, causing them to sinter and become spherical. For powders, fluidity, bulk density, microhardness, microstructure, phase and chemical composition were studied. Detonation method coatings were sprayed from the powders. Spheroidized powders have good technological properties: fluidity τ=33÷74 sec., bulk density ɣ=1,76÷3,05 g/cm 3 . A single particle of powder has a spherical shape with high strength and microhardness Н µ =870÷3300 MPa which are comparable to the values of sintered compact materials. Powder particles have a heterophase microstructure with a uniform distribution of metallic and refractory components. (Ti,Cr)B2 –NiAlCr powders have the best technological and mechanical properties. Powders with AlN and SiC additives have a more branched particle surface. With increasing AlN and SiC content the surface of the particles becomes rougher and the fluidity of the powders worsens. Detonation coatings from the resulting powders have a heterophase microstructure with a uniform distribution of structural components. The adhesion strength of the coatings to the base is σ=91÷115 MPa and the density is 98÷99%.
3D printing of auxetic structures by the FDM method
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Moroz Vladislav , Naumenko Vladislav , Zgalat-Lozynskyy Ostap
Published: August 2024

With the development of 3D printing techniques, metamaterials, such as auxetic structures, became a new area of research. 3D printing of auxetic structures from various materials has attracted considerable interest in the scientific community due to their unique properties, such as negative Poisson's ratio. Using various composite materials, it is possible to achieve high strength, lumpiness, biocompatibility and other properties that make them attractive for various technological and engineering applications. In many studies, emphasis is placed on the development of new methods of manufacturing auxetic materials, as well as on understanding their microstructure and deformation mechanisms. For example, the possibility of using various manufacturing techniques, including 3D printing, to create materials with desired auxetic properties is being explored. Some research is aimed at developing materials with unique combinations of properties, such as combined auxetic and piezoelectric behavior, which may have applications in sensor and actuator systems, as well as in aerospace and biomedical and medical fields. At current investigation the auxetics were printed on a Creality Ender-5 printer using 1.75 mm diameter PLA filaments reinforced with ceramic particles and fibers. 3D models are designed and edited in Blender, Autodesk Netfabb programs, prepared for printing in Simplify3D. The use of different materials and their combinations in 3D printing allows you to create materials with different properties in one part. This opens up new possibilities for creating auxetic materials with unique mechanical and physical characteristics.
3D printing of heaters based on MoSi2 by Robocasting method
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Naumenko Vladyslav , Zyatkevich Nina , Vedel Dmytro , Derev'yanko Oleksandr , Lytvyn Roman , Myslyvchenko Oleksandr , Zgalat-Lozynskyy Ostap
Published: August 2024

One of the main directions of 3D printing is obtaining products of complex shapes to replace worn or damaged analogues. Modern analytical equipment for heat treatment of materials is produced in small batches and contains heating elements of complex shapes. Replacing these heating elements is an expensive and complicated process. Using modern 3D printing technologies, such as the Robocasting method, it is possible to print products of complex shapes from a material similar to that used in the device, or even better, [1,2]. In our work, we investigated the process of manufacturing heaters of complex shapes based on MoSi2, from the preparation of pastes for 3D printing using the Robocasting method to their consolidation and determination of the characteristics of the obtained heating elements. The shapes of the heating elements were obtained using the Robocasting method. This involved employing layer-by-layer printing on the Ender 5 printer with the Stoneflower 2 ceramic module and using a paste based on MoSi2 powder. A study of the rheological properties of pastes based on molybdenum disilicide and synthetic rubber with gasoline as a binder was conducted. It was established that the print scale (nozzle/filament diameter) depends on the content of the plasticizer. The smaller the nozzle, the greater the content of plasticizer required to obtain a high-quality product shape closest to a digital twin. Several samples of different forms were printed using Robocasting technique. Printed forms were heat-treated in a vacuum drying chamber at a temperature of 400° for 2 hours. Sintering was carried out in the high temperature vacuum furnace at 1900°C, holding time - 1 hour. After sintering, the residual porosity of the samples is 15-17%. The Vickers hardness of the samples was 9.5±1.4 GPa. When determining the current-voltage characteristic, the heater was heated to a temperature of about 90°C at a power of 1 W.
Study of the tribological properties of MoN cathodic arc coatings applied to steel
Authors:   Karpenko Physico-Mechanical Institute of the NAS of Ukraine, Podhurska Viktoriya , Klimenko Illya , Belous Vitaliy , Ostash Orest , Ovcharenko Valeriy , Tolmachova Galyna , Kolodiy Igor , Ishchenko Mykhailo , Babayev Ivan , Kuprin Oleksandr
Published: August 2024

The molybdenum nitride coating deposited by the vacuum arc method was one of the first coatings to be used for the protection of machine tools and machine parts. The vacuum arc method allows the deposition of molybdenum nitride with different stoichiometry and crystalline phases of cubic γ-Mo₂N and hexagonal δ-MoN. The binary system of Mo–N offer a high potential to enhance the tribological properties of common hard coatings, owing to their ability to form lubricious oxides (Magnéli phases) at elevated temperatures. However, the application of Mo-N coatings at high temperatures is limited to 500°C [1]. The work aim is to investigate the effect of deposition process parameters (bias voltage), tribopair Al₂O₃, ShKh15 steel, ShKh15 steel with CrN, TiN and MoN coatings and test temperature on the tribological properties of MoN coatings deposited by cathodic arc evaporation method on 15Х12ВНМФ steel. In all coatings deposited on steel at a nitrogen pressure of 0.3 Pa and bias potentials (-30, -50 and -70 V), hexagonal molybdenum nitride δ-MoN was found. The nanohardness of the deposited coatings is at the level of 34.1...34.7 GPa, and the Young's modulus is 437...471 GPa. The MoN coating on the steel substrate is characterized by low wear at the level of 1.57-2.43·10⁻⁵ mm³/Nm at room temperature tests. An increase in the test temperature to 500 °С leads to a significant (by an order of magnitude) increase in the wear coefficient of 1.83-2.17·10⁻⁴ mm³/Nm. This is due to the low resistance of molybdenum nitride to oxidation at this temperature. Molybdenum nitride oxidizes to molybdenum oxide, which can lead to rapid degradation of the coating under load. The lowest coefficient of friction for the MoN coating was recorded in a pair with a TiN-coated steel ball (0.37), and the lowest wear (10⁻⁷ mm³/N·m) for the MoN – steel and MoN – TiN pairs.
Design of grain composition of conductive cluster of multicomponent composite and mechanism for monitoring morphology of its microstructure
Authors:   Frantsevich Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Omeliana Pritsaka street, 03142 Kyiv, Ukraine, Petrovskyi Vitaly , Semenyuk Natalia
Published: August 2024

The electric field strength, and the current density which that promotes the heating of the material, both are also a nonlinear function of the grain composition of the conductive cluster. If the square of current density through the sample is a structure-sensitive parameter for a fine-grained structure, the square of electric field strength shows greater sensitivity in the case of predominance of the coarse microstructure. An empirical formula is proposed that relates the concentration of the coarse fraction in percent with the electric current density (in A/mm2), or the electric field strength (in V/cm), at which the surface temperature of 800K is reached (the beginning of the visible dark red glow of incandescent bodies). It was established that the critical change in the concentration of the coarse fraction, at which the specified color temperature is observed, is 30% Thus, the empirical relations can be applied to calculate the content of the coarse fraction in the microstructure morphology of the conducting cluster on the basis of direct measurements of the electric current density through the resistive material or resistive region.