UDC 621.762.5:661.657.5
V. I. Kushch*, I. A. Petrusha, V. Z. Turkevich
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*vkushch56@gmail.com
The Influence of Grain Boundaries on the Elasticity and Thermal Conductivity of Polycrystalline Cubic Boron Nitride (pp. 3-14)
Theoretical models of thermal conductivity and elasticity of a polycrystal with imperfect grain boundaries and residual porosity have been developed. Based on the analysis of research data using these models, several estimates of the thermal conductivity and elasticity of grain boundaries in polycrystalline cubic boron nitride have been obtained and the influence of foaming temperatures on them has been studied. The significant dependence of the macroscopic thermoelastic properties of a polycrystal on the state and properties of grain boundaries allows using the latter as a criterion of the structural perfection of a polycrystal.
UDC 541.16
S. F. Matar
Lebanese German University (LGU), Computational Materials and Molecular Science (CMMS), Sahel-Alma, Keserwan, Lebanon
s.matar@lgu.edu.lb
High-density ultrahard new orthorhombic carbon allotropes C12 and C16 with diamond-like physical properties: structural and density functional theory studies (pp. 15-24)
New orthorhombic carbon allotropes with original topology 44T39 C12, mog-C12 and cbs-C16 were developed based on crystallographic substantiation of the C4 tetrahedral packing structure and compounds, confirmed by density functional theory calculations of ground state structures and physical properties. Their structures were identified using distorted C4 tetrahedra, in contrast to the ideal ones that characterize diamond and have small average atomic volumes, which leads to high density and subsequent superhard mechanical properties. The allotropes were found to be dynamically stable with positive frequencies detected by their phonons contained in the band structures. The corresponding thermodynamic properties showed that the calculated specific heat curves CV = f(T) are close to their experimental values for diamond given in the literature. The closest agreement with the experimental data was found for the most coherent allotrope in the series – cbs-C16, which simultaneously has the largest electronic indirect band gap, similar to diamond. Based on the study, a holistic relationship was derived for carbon materials: crystal structure ↔ mechanical ↔ dynamic ↔ electronic properties.
UDC 621.921.34-492.2:539.89 :621.762.5
В. О. Вєніков*, О. О. Бочечка**, О. І. Чернієнко, О. С. Осіпов, В. В. Білорусець, А. О. Лямцева, Ю. О. Мельнійчук
Інститут надтвердих матеріалів ім. В. М. Бакуля НАН України, м. Київ, Україна
*vladislav.venikovv@gmail.com
**bochechka@ism.kiev.ua
Вплив модифікації зерен алмазного порошку титановим покриттям на формування з нього полікристалічного композита за високого тиску і високої температури (стор. 25-30)
Порошок алмазу синтезовано в системі Mg–Zn–C за тиску 8 ГПа та температури 1800 °C. Після хімічного очищення продукту синтезу на поверхню зерен отриманого алмазного порошку нанесено титан методом хімічного осадження з газової фази. Досліджено вплив покриття на кінетику ущільнення та структуру спеченого алмазного полікристалічного композита. Показано, що спікання за високого тиску алмазного порошку з титановим покриттям зменшує температуру спікання, за якої відбувається максимальне його ущільнення, на 300 градусів у порівнянні з алмазним порошком, на який не було нанесене титанове покриття.
Ключові слова: синтез алмазу, титанове покриття, спікання, алмазний полікристал, апарат високого тиску.
UDC 621.315
V. I. Omelyanenko1, I. P. Fesenko1, *, O. M. Kaydash1, Yu. M. Tuz2, A. V. Dovgal2, S. A. Kukharenko1, V. I. Chasnyk3, G. S. Oleinyk4, G. P. Zakharchuk1
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine
3State Enterprise Research Institute “Orion”, Kyiv, Ukraine
4I. M. Frantsevich Institute for Problems of Materials Science, NAS of Ukraine, Kyiv, Ukraine Kyiv, Ukraine
*igorfesenko@ukr.net
Structure and specific surface area of aluminum nitride particles during grinding (pp. 31-42)
To improve the process of obtaining parts from highly thermally conductive aluminum nitride ceramics by free sintering, two types of grinding of the initial powder system were compared in terms of specific surface area, impurity composition and defect structure of the powder particles. A calculated estimate of the amount of adsorbed gases on the surface of the initial and ground powders is given, which was taken into account for obtaining dense ceramic parts of various sizes during high-temperature sintering.
Keywords: powder, aluminum nitride, grinding, specific surface area, adsorption, electron microscopy, X-ray structural analysis.
UDC 666.7
V. G. Grechanyuk1, 2, O. V. Matsenko1, A. V. Kozyrev1, *, I. M. Grechanyuk1, V. O. Shapovalov2
1Kyiv National University of Civil Engineering and Architecture, Kyiv, Ukraine
2E. O. Paton Institute of Electric Welding, NAS of Ukraine, Kyiv, Ukraine
*artem.v.kozyrev@gmail.com
Structure and mechanical properties of thick vacuum TiS condensates obtained by electron beam evaporation method (pp. 43-48)
The possibility of obtaining thick condensed TiS materials by the method of high-speed electron beam evaporation-condensation of graphite and titanium in vacuum was investigated. The dependences of the density, porosity, and microhardness of the initial and annealed at 1000 °C condensates on the substrate temperature were obtained. Analysis of mechanical properties depending on the carbon content in TiS condensates showed that the bending strength reaches a maximum at a carbon content of 12–14% (by mass), and microhardness at 18–20% (by mass).
Keywords: condensation, condensed materials, electron beam evaporation, evaporation-condensation, titanium carbide.
UDC 621.923
V. G. Grechanyuk1, 2, O. V. Matsenko1, A. V. Kozyrev1, *, I. M. Grechanyuk1, V. O. Shapovalov2
1Kyiv National University of Civil Engineering and Architecture, Kyiv, Ukraine
2E. O. Paton Institute of Electric Welding, NAS of Ukraine, Kyiv, Ukraine
*artem.v.kozyrev@gmail.com
Structure and mechanical properties of thick vacuum TiS condensates obtained by electron beam evaporation method (pp. 43-48)
The possibility of obtaining thick condensed TiS materials by the method of high-speed electron beam evaporation-condensation of graphite and titanium in vacuum was investigated. The dependences of the density, porosity, and microhardness of the initial and annealed at 1000 °C condensates on the substrate temperature were obtained. Analysis of mechanical properties depending on the carbon content in TiS condensates showed that the bending strength reaches a maximum at a carbon content of 12–14% (by mass), and microhardness at 18–20% (by mass).
Keywords: condensation, condensed materials, electron beam evaporation, evaporation-condensation, titanium carbide.
UDC 621.922.34
Jinyu Shang1, Ruien Yu1, 2, *, Boheng Zhu1, Wenjie Gong1, Zhicong Tian1, Kenan Li3, Qingchun Ma1, Xijing Zhu1
1Shanxi Key Laboratory of Advanced Manufacturing Technology, North University of China, Taiyuan, P.R. China
2Xinjiang Key Laboratory of High Value Green Utilization of Low-rank Coal, Changji University, P.R. China
3State Key Laboratory for High Performance Tools, Zhengzhou Research Institute for Abrasives & Grinding Co., Ltd, Zhengzhou, P.R. China
*yuruien@nuc.edu.cn
The effect of nanomontmorillonite on the properties of diamond wheels on glass-ceramic bond (pp. 64-78)
The addition of nanomontmorillonite to glass-ceramic bond material and the creation of diamond grinding wheels on composite glass-ceramic bond with different dosages of nanomontmorillonite using the sol-gel method were investigated. It was shown that the introduction of an appropriate amount of nanomontmorillonite can effectively improve the comprehensive performance of diamond grinding wheels on glass-ceramic bond by utilizing its size and surface effects.
Keywords: glass-ceramic bond, nanomontmorillonite, sol-gel method, grinding wheel, grinding performance.
UDC 621.921.34-492.2:004.89
G. A. Petasyuk, O. O. Bochechka*
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*petasyuk@ukr.net
**bochechka@ism.kiev.ua
Automated 3D Grain Shape Identification of High-Strength Synthetic Diamond Grinding Powders (pp. 79-93)
The special significance of the spatial shape of grains in the tasks of indirect-analytical determination of technological properties of synthetic diamond grinding powders is substantiated. With reference to literary sources, it is noted that direct use of the actual 3D grain shape of such grinding powders instead of its 3D model allows obtaining more reliable information on the indicators of technological properties. The applied importance of creating methodological tools for automated identification of the 3D shape of a large-volume (up to 2000 pcs.) sample of grains of such grinding powders is emphasized. An original method for solving this problem for high-strength synthetic diamond abrasive powders is proposed. The method is based on the known fact that the grains of such abrasive powders are crystals with a 3D shape close to octahedra, cuboctahedrons and truncated octahedra. Analytical and graphical information is provided on the shape of the orthographic parallel projection of the specified spatial bodies depending on the 2D shape of the face on which they are located. An analytical representation of the relationship between the geometric parameters of the projection, necessary for automated identification of both the 2D shape of the projection and the 3D shape of the grains, and the generating parameters of the octahedron, cuboctahedron and truncated octahedron is obtained. Analogues of the morphometric characteristics of abrasive powders, which are diagnosed by modern computer-technical means and whose grains have the 3D shape of the considered spatial bodies, are updated. The practical application of the developed methodological tools is illustrated on the example of high-strength synthetic diamond grinding powders AC250–AC500. It was established that the relative proportion of grains of 3D shapes other than octahedra, cuboctahedrons and truncated octahedra does not exceed 31%.
Keywords: identification, high-strength grinding powder, grain, shape, projection, morphometric characteristics, technological properties.
UDC 669.018.25:621.762.5
O. O. Matviichuk*, V. Z. Turkevich, E. F. Kuzmenko, I. O. Gnatenko
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*o.o.matviichuk@gmail.com
Thermal conductivity of WC–20% Co and WC–20% Ni alloys with mesostructure (pp. 94-97)
The results of the study of the thermal conductivity of WC–20% (by mass) Co and WC–20% (by mass) Ni alloys with mesostructure, produced by free liquid-phase sintering, are reported. A comparison with the literature data for alloys with a binder content of 20% (by mass) is made.
Keywords: thermal conductivity, mesostructure, hard alloy.