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 & abouliess@gmail.com
Original orthorhombic tetrahedral-trigonal hybrid allotropes of Cn (n = 8, 10, 12, 14) with ethene- and propadiene-like blocks: crystallography and quantum mechanical calculations (pp. 3-14)
Based on crystallography and calculations within the framework of quantum density functional theory, original allotropes of carbon, orthorhombic C8, C10, C12 and C14, are proposed, which represent mixed sp2/sp3 hybridizations of carbon with C=C ethene-like and C=C=C propadiene-like embedded blocks. Carbon allotropes with topologies related to jeb, mog, and new topologies exhibit alternating tetrahedral and trigonal carbon stacking along the a-orthorhombic direction (vertical), close to but distinct from the “isoglitter”. Carbon allotropes C8, C10, C12, C14 are shown to be coherent and stable both mechanically (elastic properties) and dynamically (phonons), with calculated Vickers hardness (HV) values ranging from 25 to 52 GPa, the latter value being related to C12 having the highest number of tetrahedral and trigonal stacking. The high phonon frequencies w ~ 50 THz were assigned to the stretching regime of C=C (in C8 and C12) and C=C=C (in C10 and C14) blocks, which is in good agreement with the Raman molecular identification experiment. The observed values w ~ 40 THz were proposed as signatures of single C–C bonds in tetrahedra, as in diamond. The electronic band structure and density of states shown in the example of C8 indicate a metal-like behavior, which is explained mainly by the wandering role of the trigonal π-electrons of carbon.
Keywords: density functional theory, mixed hybridization, carbon, phonons, hardness.
UDC 666.3:539.5
T. B. Serbeniuk1, *, T. O. Prikhna1, V. V. Zagorodniy2, V. B. Sverdun1, V. V. Oliynyk2, M. V. Karpets1, 3, 4, V. E. Moshchyl1, S. S. Ponomarev5
1V. M. Bakuly Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Teaching and Scientific Institute of High Technologies, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
3I. M. Frantsevich Institute of Problems of Materials Science, NAS of Ukraine, Kyiv, Ukraine
4National Technical University of Ukraine
“Igor Sikorsky Kyiv Polytechnic Institute”, Kyiv, Ukraine
5V. E. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine, Kyiv, Ukraine
*serbenuk@ukr.net
Electrodynamic properties of AlN–С and AlN–С–Mo composites obtained by free sintering (pp. 15-23)
The electrodynamic characteristics in the frequency range 1–10 GHz of composite materials based on AlN–5% (by mass) С(carbon black) and AlN–5% (by mass) С(diamond powder)–5%Mo, obtained by free sintering at a temperature of 1850 °C, were investigated. It was shown that the real and imaginary parts of the relative permittivity of composites containing carbon black and diamond powder with molybdenum at a frequency of 10 GHz are εʹ ≈ 16.1, εʺ ≈ 4.3 and ɛʹ ≈ 9.3, εʺ ≈ 0.7, respectively.
Keywords: composite material, AlN, diamond powder, molybdenum, dielectric constant, electrodynamic properties.
UDC 622.24.051:536.2
V. A. Dutka*, A. L. Maistrenko, V. G. Kulych, O. I. Borymsky
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*vadutka@ukr.net
Modeling of densification of boron carbide-based ceramic materials by high-speed sintering under pressure (pp. 24-37)
The process of densification of boron carbide-based powder mixtures by high-speed sintering under pressure has been simulated. The computer model developed for this purpose is based on the theory of densification of porous materials by Skorokhod–Olevsky–Stern and takes into account the kinetics of grain growth during the sintering process. The results of laboratory and computational experiments were used to determine the model parameters. The adequacy of the model was confirmed by comparison with the available experimental data.
Keywords: boron carbide, high-speed sintering under pressure, densification, grain growth, modeling.
UDC 621.763
E. S. Gevorkyan1, *, V. P. Nerubatsky2, V. O. Chyshkala3, S. V. Lytovchenko3, M. M. Prokopiv4, W. Samociuk1, V. A. Mechnyk4
1University of Life Sciences in Lublin, Lublin, Poland
2Ukrainian State University of Railway Transport, Kharkiv, Ukraine
3Kharkiv National University named after V. N. Karazin, Kharkiv, Ukraine
4V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*edsgev@gmail.com
Technological and innovative differences of the electroconsolidation method as a variant of the plasma sintering method of refractory compounds (pp. 38-51)
Some physical and technological features of the electroconsolidation process are considered, its place among numerous methods of electric discharge sintering is determined. The main advantages compared to other methods of densification of nanopowders are noted. The influence of sintering modes on the formation of the microstructure, the features of grain growth inhibition are studied during heating, the effect of temperature and heating rate of graphite mold on the physical and mechanical properties of ceramic composites. The original data of the electroconsolidation process and the physical and mechanical properties of nanocomposites obtained by this method are presented. A probable scheme of electric discharge processes in the case of passing high-amperage currents through a graphite mold is provided.
Keywords: hot pressing, electroconsolidation, electric discharge, composite, nanopowder, sintering.
UDC 621.762.5:622.24.051.64:669.11
Zhiming Wang1, Xiecai Yan1, Yakun Tao1, Wucheng Sun1, Xiaohong Fang1, 2, Longchen Duan1, 2, Songcheng Tan1, 2, *1Faculty of Engineering, China University of Geosciences, Wuhan, P.R. China
2National Center for International Research on Deep Earth Drilling and Resource Development, Wuhan, P.R. China
*wstansongcheng@cug.edu.cn
Effect of sintering parameters and liquid phase content on the properties of iron-based matrix impregnated diamond bit (pp. 52-68)
The effect of sintering parameters and liquid phase content on the properties of iron-based pre-alloyed impregnated diamond bit (IAD) matrix was investigated using an orthogonal experimental design. Based on the analysis of the results, it was found that the sintering temperature and liquid phase content have significant effects on the flexural strength, hardness, relative density and wear rate of the matrix. For metal matrix composite (MMC), with the increase of sintering temperature from 900 to 1050 °C, the flexural strength, hardness (HRB) and relative density of MMC first decreased, then increased and finally decreased again, while the wear rate increased with temperature. With the increase of liquid phase content, the four properties of MMC showed a similar trend of first increasing and then decreasing. Comparatively, the effects of holding time and sintering pressure on the matrix properties were smaller than those of sintering temperature and liquid phase content, but they also had significant effects on some matrix properties. Holding time had a more significant effect on hardness and wear resistance, while sintering pressure had a significant effect only on hardness. After the addition of diamonds, the flexural strength of the diamond matrix composite first increased and then decreased with increasing temperature, while the flexural strength continued to decrease with increasing liquid phase content.
Keywords: orthogonal testing method, pre-doped powder with high iron content, hot pressing sintering, impregnated diamond bit.
UDC 621.923.7
Yu. D. Filatov1, *, A. Yu. Boyaryntsev2, V. I. Sidorko3, S. V. Kovalev1, O. V. Kolesnikov2, V. O. Novgorodtsev2, Ya. I. Polupan2
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Institute of Scintillation Materials, NAS of Ukraine, Kharkiv, Ukraine
3State Enterprise “Engineering and Production Center ALKON” NTAK (ALKON) NAS of Ukraine
*filatov2045@gmail.com
Polishing Mechanism of Polystyrene-Based Scintillators (pp. 69-83)
As a result of the study of the polishing mechanism of polystyrene scintillators using a dispersed system of micro- and nanopowders, it was found that the formation of sludge nanoparticles (SNP) and polishing powder wear nanoparticles (PP) is a consequence of Förster resonance energy transfer (FRET), which occurs in a 4-mode mode in an open microresonator formed by the surfaces of the processed material and polishing powder particles. It is shown that the wear of particles of the dispersed phase of the polishing dispersed system occurs twice as fast as the removal of the processed material. It is shown that during the scattering of quantum nanoparticles in an open resonator formed by the surfaces of the processed material and the lapping compound, the total cross section of the scattering of the HF on the PN (31.1 Mb) is much larger than the total cross section of the PN scattering on the PN (2.4 Mb), which determines the absence of a deposit of nanoparticles of wear of the polishing powder on the processed surface and the presence of a deposit of nanoparticles of sludge on the lapping compound surface. It is established that the results of the calculation of the material removal rate are consistent with the data of the experimental determination of the productivity of polystyrene polishing with a deviation of up to 4%, and the fragments of the deposit of nanoparticles of sludge on the lapping compound surface have sizes from 0.2 to 1.0 mm and are discretely located in an annular zone with a radius of 24.5 mm. It has been shown that polishing of polystyrene-based scintillation elements using a dispersed system of micro- and nanoparticles increases the ability of detectors to separately record fast neutrons and gamma quanta according to the pulse shape for long-range detectors by 14%.
Keywords: polishing, polystyrene, Förster resonance energy transfer (FRET), material removal rate, plaque fragments.
UDC 621.922:621.793
V. I. Lavrinenko
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
lavrinen52@gmail.com
Boron oxide on the surface of grains of superhard materials as a possible factor for increasing operational performance grinding tool (pp. 84-92)
The influence of the presence of boron oxide on the surface of superhard materials on the performance of the grinding tool was studied. The possibility of increasing the strength of cubic boron nitride (CBN) grains by heat treatment of the grains in air at low temperatures due to filling their defect space with a B2O3 film was shown. The test results showed that the wheels containing CBN powder after heat treatment had higher wear resistance and lower specific energy consumption of grinding. It was shown that the presence of boron oxide on the surface of the grains of superhard grinding powders is an important factor in increasing their performance in the grinding tool.
Keywords: boron oxide, aluminum oxide, cubic boron nitride grains, diamond grains, grinding tool, performance.
UDC 666.3:539.5
M. M. Prokopiv*, O. V. Kharchenko, I. P. Fesenko
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*mmprokopiv@gmail.com
Thermal conductivity of tool ceramics obtained from exothermic mixtures Cr2O3–AlN, ZrO2(M)–Al–C in the process of hot pressing (pp.93-95)
The results of the study of the thermal conductivity coefficient of ceramic tool materials obtained from exothermic mixtures Cr2O3 with AlN and ZrO2(M)–Al–C by hot pressing are presented. The characteristics of the obtained materials and commercial tool ceramics Al2O3–TiS of the CC650 brand (“Sandvik Coromant”, Sweden) are compared.
Keywords: chromium oxide, aluminum nitride, zirconium oxide, aluminum, exothermic mixtures, hot pressing, thermal conductivity.
UDC 661.657.5:536.421.1
V. L. Solozhenko
LSPM–CNRS, Université Sorbonne Paris Nord, Villetaneuse, France
vladimir.solozhenko@univ-paris13.fr
Melting points of (super)hard cubic boron pnictides (pp. 96-100)
Based on the analysis of the established empirical relationship between the elastic constants and melting points of cubic pnictides of group IIIa elements, the melting points of hypothetical cubic pnictides BSb and BBi were predicted. A critical analysis of the melting data of the (super)hard cubic boron pnictides BX (X = N, P, As, Sb, Bi) is performed and it is shown that their melting points at atmospheric pressure, as well as their Vickers hardness, are linear functions of the Mendeleev number of the pnictogen.
Keywords boron pnictides, melting points, elastic constants, hardness.