UDC 621.921.343-492.2:541.128.13
AND. D. Shevchenko, G. D. Ilnytskaya*, V. N Tkach,
IN. IN. Tymoshenko (Kyiv)
AND. IN. Terekhov (Kharkov city; Wroclaw, Poland)
L. AND. Ishchenko (Kharkov)
AND. Zalesky, A. WITH. Moose (Wroclaw, Poland)
*admit@imp.kiev.ua
**gil-ism@ukr.net
Influence of impurities on electrical conductivity and magnetoresistance in carbon nanotubes (pp. 3–9)
The temperature and magnetic field dependences of the specific electrical resistance of carbon nanotubes of the original material and chemically purified from impurities are investigated. It is shown that the dependence of the specific electrical resistance on the temperature of the investigated carbon nanotube powders can be well described within the framework of 3D hopping conductivity with a variable jump length in a wide temperature range (5–250 K for the initial carbon nanotubes, 5–180 K for carbon nanotubes after chemical treatment).Magnetoresistivity of carbon nanotubes initially and after chemical treatment at temperatures of 5, 77 and 250 K decreases with increasing magnetic field strength.
Key words: carbon nanotubes, specific electrical resistance, magnetoresistance, content of impurities, chemical processing.
UDC 621.793:620.179.1/.186
C. Escobar, J. C. Caicedo* (Cali, Colombia)
H.H. Caicedo (PA, Chicago, USA)
M. Mozafari (Tehran, Iran)
*jcaicedoangulo1@gmail.com
Design of hard surfaces with metal (Hf/V) nitride multinanolayers (p. 10–28)
Physical properties as mechanical and tribological evolution on 4140 steel surfaces coated with hafnium nitride/vanadium nitride [HfN/VN]n multilayered systems deposited in various bilayer periods via magnetron sputtering has been exhaustively studied in this work. The coatings have been characterized in terms of structural, chemical, morphological, mechanical, and tribological properties by X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, scanning and transmission electron microscopy, nanoindentation, pin-on-disc and scratch tests. Moreover, the failure mode mechanisms were observed via scanning electron microscopy. The preferential growth in the face-centered cubic (111) crystal structure for [HfN/VN]n multilayer coatings have been shown by X-ray diffraction results. The best enhancement of the mechanical behavior has been obtained when the bilayer period was 15 nm (n = 80), yielding the highest hardness (37 GPa) and elastic modulus was (351 GPa). The values of the hardness and elastic modulus were 1.48 and 1.32 times higher than the coating with n = 1, respectively, as well as the lowest friction coefficient (~ 0.15) and the highest critical load (72 N). These results indicated significant enhancements in mechanical, tribological, and adhesion properties, compared to HfN/VN multilayered systems with bilayer period of 1200 nm (n = 1). The hardness and toughness enhancement in the multilayered coatings could be attributed to the different mechanisms that produce the layer formation with nanometric thickness due to the number of interfaces acting as obstacles for crack deflection and dissipation of crack energy. Due to the emergent characteristics of the synthesized multilayered material, the developed adaptive coating could be considered as higher ordered tool machining systems, capable of sustaining extreme operating conditions for industrial applications.
Keywords: hard coatings, isostructural systems, multinanolayers, tool wear.
UDC 621.793.1:621.9.02:620.18
V. I. Ivashchenko*, P. L. Scrynskyy, O. S. Lytvyn,
O. O. Butenko, O. K. Sinelnichenko (Kiev, Ukraine)
L. Gorb (Jackson, Vicksburg, USA)
F. Hill (Vicksburg, USA)
J. Leszczynski (Jackson, USA)
A. O. Kozak (Kyev, Ukraine)
*ivash@ipms.kiev.ua
Comparative investigation of NbN and Nb–Si–N films: experiment and theory (p. 29–43)
NbN and Nb–Si–N films have been deposited by magnetron sputtering of the Nb and Si targets on silicon wafers at various powers supplied to the Nb target. The films have been investigated by an atomic force microscope, X-ray diffraction, X-ray photoelectron spectroscopy, nanoindentation and microindentation. The NbN films were nanostructured, and the Nb–Si–N films represented an aggregation of δ-NbNx nanocrystallites embedded into the amorphous Si3N4 matrix (nc-δ-NbNx/a-Si3N4).The annealing of the films in vacuum showed that their intensive oxidation occurred at an annealing temperature higher than 600 °C. To explain the experimental results on the Nb–Si–N films, first-principles molecular dynamics simulations of the NbN(001)/Si3N4 heterostructures have been carried out.
Keywords: NbN and Nb–Si–N films, magnetron sputtering, film structure, bonding picture, nanoindentation, first-principles calculations, stress-strain curves.
UDC 621.922.079
R. S. Shmegera, V. I. Kushch*, A. L. Maystrenko (Kyiv)
*vkushch@ism.kiev.ua
Nickel-based metallic bond for intensive electrosintering of diamond-containing composites (pp. 44–53)
A multicomponent alloy optimized for intensive electrosintering has been developed The structure and mechanical properties of the nickel-based diamond-containing composite were investigated. When using tin as a sintering activator, a heterogeneous structure with reinforcing intermetallic inclusions is formed due to the formation of a limited portion of the liquid phase. The mechanical properties of the Ni–Sn–Cu alloy system vary widely depending on the choice of the initial composition of the powder mixture. The established correlations between the composition of the initial mixture and the properties of the electrosintered material ensure the targeted formation of the properties of the bond for a specific application.
Keywords: composite diamond-containing material, nickel, intensive electrosintering, intermetallic, structure, properties.
UDC 548
AND. IN. Lysenko (Kyiv)
gart.ua@i.ua
Structural and mechanochemical features of high-pressure phases formed during p-, T-, and p-processed graphite (pp. 54–65)
Based on the high-molecular model of the graphite → diamond transition, a mechanism for the synthesis of non-equilibrium high-pressure tense phases is proposed, which are formed as a result of the deviation of the process of 3d polymerization of 2d networks of graphite from the graphite → diamond reaction route and block the synthesis of diamond. The baric criteria for the synthesis of the main high-pressure carbon phases are considered. Structural models of the new superhard carbon formed during cold p-processing of graphite, proposed by American, Chinese, and Russian scientists, are discussed.
Keywords: high-molecular structure, new superhard carbon, high-pressure phases, phase transition.
UDC 621.921.34-419:620.187
R. J. Liu*, Y. B. Cao, C. L. Yan, C. R. Zhang,
P. B. He (Changsha, China)
*rongjunliu@nudt.edu.cn
Preparation and characterization of diamond–silicon carbide–silicon composites by gaseous silicon vacuum infiltration process (p. 66–72)
Diamond–SiC–Si composites have been prepared using gaseous silicon vacuum infiltration.The evolution of the phases and microstructures of the composites have been analyzed using X-ray diffraction technique and scanning electron microscopy. It has been found that the diamond–SiC–Si composite is composed of β-SiC, diamond, and residual Si. The diamond particles were distributed homogeneously in the dense matrix of the composites. Besides, the effects of particle size and content of diamond on the properties of diamond–SiC–Si composites have been analyzed. The thermal conductivity of the composites increases with particle size and content of diamond. When the particle size and content of diamond are 300 µm and 80 wt %, respectively, the thermal conductivity of the composites approaches the value of 280 W·m–1·K–1.
Keywords:diamond–SiC–Si composites, microstructure, evolution of phases, vacuum infiltration, thermal conductivity, XRD, scanning electron microscopy.
UDC 621.922.025
IN. K. Starkov, E. G. Polkanov (Moscow, Russia)
v.starkov@stankin.ru
Investigation of the performance of a tool with a reduced concentration of cubic boron nitride when grinding hardened steel (p. 73-80)
Grinding wheels made of cubic boron nitride on ceramic bonds were developed and tested, in which the grain content varied from 25 to 12.5% of the volume of the working layer of the tool (concentration 100 and 50%, respectively). It was established that during internal grinding of hardened steel bushings, wheels with a reduced concentration of cubic boron nitride provide higher processing productivity and specific abrasive consumption is up to 2.5 times lower than a tool with 100% concentration.
Keywords: cBN grinding wheels, internal grinding, concentration of cubic boron nitride.
UDC 621.923
C. V. Ryabchenko (Kyiv)
s.riabchenko@yandex.ru
Grinding of gears with disc wheels from STM (p. 81–89)
Issues of increasing the efficiency of grinding high-precision gears of 3-4 degrees of accuracy when using a tool made of superhard materials are considered. The performance of disc grinding wheels on various ligaments is studied and recommendations for their use in tooth grinding are given.
Keywords:tooth grinding, superhard materials, gear wheels, disk wheel, wheel wear.
UDC 621.014
AND. AND. Vynogradov (Kyiv)
almavin@meta.ua
On the mechanism of chip formation during oblique cutting of metals (pp. 90-99)
An analysis of the ratios for calculating the cutting angle during oblique free cutting of metals, proposed earlier by a number of researchers, is given. It is shown to be expedient from the point of view of chip formation to represent this cutting process as an orthogonal free cutting tool with a front angle that is a function of the front sharpening angle and the angle of inclination of the cutting edge. The corresponding chip formation scheme allows you to calculate the forces acting along the cutting edge and normal to it. The results of comparing the calculated values of the cutting forces with the experimental ones are presented, and their good convergence is shown.
Keywords: tool, chip forming, diagonal free cutting, orthogonal free cutting.
UDC 621.762:921.34
G. WITH.Oleynyk*, V. M. Volkogon, A. IN. Cat,
N. I. Danylenko, S. K. Avramchuk (Kyiv)
*oleynik@ipms.kiev.ua
On the formation of a solid solution with a diamond-like lattice in the wurtzite boron nitride–cubic diamond system (pp. 100–102)
The results of electron microscopic studies confirming the contact interaction at p = 7.7 GPa, T = 1700–1900°С of cubic diamond particles and wurtzite boron nitride with the formation of an interlayer (transition zone) of diamond-like VN are presented. It was established that the transition zone contains carbon, the quantitative fraction of which decreases as the transition from the area in contact with diamond to the matrix component based on dense VN phases occurs.
Key words: diamond, boron nitride, solid solution, interaction, diamond-like lattice.
UDC 666.792.34:539.89
IN.WITH. Turkevich*, D.AND. Stratychuk, M.AND. thin skin,
N.P. Bezhenar (Kyiv)
*vturk@ism.kiev.ua
Thermodynamic calculation of the state diagram of the Al–B system at pressures up to 8 GPa (pages 103–105)
Using models of phenomenological thermodynamics with interaction parameters obtained on the basis of experimental data on phase equilibria at high pressures and temperatures, the topological evolution of the state diagram of the aluminum–boron system at pressures up to 8 GPa was studied.
Key words: aluminum borides, high pressures, state diagrams.