Technological Institute for Superhard and Novel Carbon Materials TISNCM

Troitsk, Russia

Technological Institute for Superhard and Novel Carbon Materials TISNCM

Troitsk, Russia
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Kartavykh A.V.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Ginkin V.P.,RAS Institute of Physics and Power Engineering | Ganina S.M.,RAS Institute of Physics and Power Engineering
Advances in Applied Mechanics Research, Conference Proceedings - 7th Australasian Congress on Applied Mechanics, ACAM 2012 | Year: 2012

The work is aimed at the study of the formation and refinement of primary microstructure appearing in the refractory lightweight structural TiAl-based intermetallics during their solidification from the melt. The alloy with Ti-46Al-8Nb (at.%) nominal composition is selected for applied study in microstructure engineering. For tailored microstructure development, the Directional Solidification (DS) of pre-synthesized alloy was performed in the vertical multizone electro-furnace by Vertical Gradient Freezing (VGF) power-down technique in pure argon environment. Both columnar-dendrite, and equiaxed-granular reproducible as-cast microstructures have been produced in DS ingots, basing onto Columnar-to-Equiaxed Transition (CET) diagram exploration. Particular attention was paid further to equiaxed microstructure improvement by combination of modifying doping of alloy with boron grain refiner and VGF processing. As a result the perfect inoculated microstructure of Ti-44Al-7Nb-2B (at.%) ingots was produced with 120 μm mean grain diameter, low scattering of dimensional characteristics and high tolerance to DS process parameters variation. DS samples were examined by SEM microanalysis along with EBSD and Auger spectrometry of boride particles in the alloy matrix. The nature, state and exact composition of precipitated borides are discussed along with the nucleation mechanism in relation to the literature data.


Kartavykh A.V.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Tcherdyntcev V.V.,National University of Science and Technology "MISIS" | Stepashkin A.A.,National University of Science and Technology "MISIS" | Gorshenkov M.V.,National University of Science and Technology "MISIS"
Russian Metallurgy (Metally) | Year: 2013

The temperature dependence of the linear thermal expansion coefficient K L of the intermetallic Ti-46Al-8Nb (at %) alloy is experimentally determined for the first time within the temperature range from 373 to 1773 K (solidus point). The determined boundaries of phase fields are compared with the results of differential thermal analysis and the calculated phase diagram of the alloy. The high-temperature limit (1384 K) of the alloy structure thermostability is detected from signs of the α2 + γ ⇆ α + γ phase transition in dilatometric curves. The restructuring mechanism in the α + γ field is studied by scanning electron microscopy. It is shown that the α2 + γ → α + γ phase transition is accompanied by selective structural degradation of single-crystalline α2 lamellae and the related destruction of a fine lamellar α2-Ti3Al(Nb) + γ-TiAl(Nb) texture. The average values of K L of the alloy are calculated within 100-K ranges in the low-temperature α2 + γ phase field, which is of interest from a practical viewpoint, according to the State Standard GOST 8.018-2007. © 2013 Pleiades Publishing, Ltd.


Moya J.S.,CSIC - Institute of Materials Science | Torrecillas R.,University of Oviedo | Diaz L.A.,University of Oviedo | Rodriguez-Suarez T.,University of Oviedo | And 3 more authors.
Journal of the European Ceramic Society | Year: 2013

A small fraction (5vol.%) of detonation nanodiamonds, or DND, acts as a remarkably effective boundary pinning agent in alumina throughout a wide sintering temperature range (from 1200 up to 1700°C). This is the first time that such a strong grain growth inhibitory effect is observed for any of the alumina based composites of similar characteristics reported in the literature. These nanocomposites were consolidated by pulsed electric current sintering (PECS) and present bending strength (550MPa) and toughness (5.2MPam1/2) values significantly higher than the ones corresponding to alumina compacts obtained under the same sintering conditions. © 2013 Elsevier Ltd.


Kulnitskiy B.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Perezhogin I.,Moscow State University | Dubitsky G.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Blank V.,Technological Institute for Superhard and Novel Carbon Materials TISNCM
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials | Year: 2013

As a result of the high-temperature and high-pressure treatment of graphite we obtained a powder containing diamond and lonsdaleite. The structure and properties of the powder were studied by transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). It was found that the synthesized material contains not only diamond nanoparticles, but also some relatively large (up to several nanometers) fragments of lonsdaleite. 4H and 6H polytypes were found in some of the diamond particles. Incoherent twin boundaries were observed in the diamond particle containing fragments of lonsdaleite. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved.


Ginkin V.P.,RAS Institute of Physics and Power Engineering | Ganina S.M.,RAS Institute of Physics and Power Engineering | Kartavykh A.V.,Technological Institute for Superhard and Novel Carbon Materials TISNCM
Advances in Applied Mechanics Research, Conference Proceedings - 7th Australasian Congress on Applied Mechanics, ACAM 2012 | Year: 2012

A non-equilibrium model of multicomponent melt solidification has been developed in which a Stefan problem with two boundaries is solved numerically, the boundaries being between the solid phase and the two-phase transition zone and between the two-phase transition zone and the liquid phase. The two-phase zone is represented as a porous medium with variable porosity. Account is taken of the additional force resisting the melt flow due to porosity and introduced by analogy with Darcys law. Computer simulation has been performed of the experiment on Sn-20 wt.%Pb binary alloy solidification by the method of downward-directed crystallization along the gravity vector. Shown in the paper are the results of a quasi two-dimensional benchmark experiment on horizontal (i.e., at the right angle to the gravity vector) directional solidification of a binary Sn-3 wt.%Pb alloy. The calculations were done using two crystallization models: the equilibrium model and the non-equilibrium one. It is shown that the non-equilibrium model gives a better description of the thermal field evolution and solute distribution caused by natural convection.


Maslenikov I.I.,Moscow State University | Reshetov V.N.,National Research Nuclear University MEPhI | Loginov B.A.,National Research University of Electronic Technology | Useinov A.S.,Technological Institute for Superhard and Novel Carbon Materials TISNCM
Instruments and Experimental Techniques | Year: 2015

Based on the functional dependences that are used in the tool nanoindentation method, a method for obtaining a hardness map in the process of scanning the surface of a sample by a piezoresonance probe is proposed. A procedure for measuring the dependence of the material hardness on the penetration depth of the probe point into the surface is designed. The experimental check of the technique was performed on samples of fiber glass in a polymeric matrix, polymethyl methacrylate, and fused quartz using a NanoScan 3D scanning nanohardometer. The method assumes that a priori information on the elastic modulus of the material is available. © 2015, Pleiades Publishing, Inc.


Al Rifai S.A.,Voronezh State University | Kulnitskiy B.A.,Technological Institute for Superhard and Novel Carbon Materials TISNCM
Journal of Physics and Chemistry of Solids | Year: 2013

Single-crystal Eu3+-doped wurtzite ZnO micro- and nanowires were synthesized by chemical vapor deposition. The nanostructures grew via a self-catalytic mechanism on the walls of an alumina boat. The structure and properties of the doped ZnO were characterized using X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning and transmission electron microscopy, and photoluminescence (PL) methods. A 10-min synthesis yielded vertically grown nanowires of 50-400 nm in diameter and several micrometers long. The nanowires grew along the ±[0001] direction. The Eu3+ concentration in the nanowires was 0.8 at.%. The crystal structure and microstructure of were compared for Eu3+-doped and undoped ZnO. PL spectra showed a red shift in emission for Eu3+-doped (2.02 eV) compared to undoped ZnO nanowires (2.37 eV) due to Eu3+ intraionic transitions. Diffuse reflectance spectra revealed widening of the optical bandgap by 0.12 eV for Eu3+-doped compared to undoped ZnO to yield a value of 3.31 eV. Fourier-transform infrared spectra confirmed the presence of europium in the ZnO nanowires. © 2013 Elsevier Ltd.


Blank V.D.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Kulnitskiy B.A.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Perezhogin I.A.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Polyakov E.V.,Technological Institute for Superhard and Novel Carbon Materials TISNCM | Batov D.V.,Technological Institute for Superhard and Novel Carbon Materials TISNCM
Acta Materialia | Year: 2010

Cobalt-filled carbon nanotubes were synthesized at high temperature and high gas pressure. A high-resolution transmission electron microscopy study demonstrates that the product of the synthesis contains cylindrical carbon nanotubes whose cores are filled with cobalt nanoparticles or nanorods. It is shown that cobalt appears inside the nanotubes in three basic modifications: face-centered cubic (fcc) lattice, hexagonal close-packed (hcp) lattice and disordered polytypic structure. The fcc lattice is often twinned, with two or more non-parallel twinning planes being observed. The orientations of the fcc and hcp cobalt particles with respect to the nanotubes were investigated. The authors believe that the variety of cobalt modifications inside the nanotubes is due to the process of segregation of the closely packed structures from the melt. © 2009 Acta Materialia Inc.


PubMed | Technological Institute for Superhard and Novel Carbon Materials TISNCM
Type: Journal Article | Journal: Acta crystallographica Section B, Structural science, crystal engineering and materials | Year: 2013

As a result of the high-temperature and high-pressure treatment of graphite we obtained a powder containing diamond and lonsdaleite. The structure and properties of the powder were studied by transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS). It was found that the synthesized material contains not only diamond nanoparticles, but also some relatively large (up to several nanometers) fragments of lonsdaleite. 4H and 6H polytypes were found in some of the diamond particles. Incoherent twin boundaries were observed in the diamond particle containing fragments of lonsdaleite.


PubMed | Technological Institute for Superhard and Novel Carbon Materials TISNCM
Type: Journal Article | Journal: Acta crystallographica. Section B, Structural science | Year: 2012

BNC nanotubes and nanofibers have been synthesized in the high isostatic pressure apparatus in Ar at 1923 K and 1.5 MPa in the presence of yttrium aluminium garnet. Some of the nanotubes obtained were filled with Al(2)O(3). Transmission electron microscopy (TEM) studies have shown that the nanotubes and nanofibers have a polygonal cross-section (prismatic shape), and most often they are twisted, which is due to the transversal instability of the nanotubes originating under the growth conditions, including temperature treatment. Twisting also revealed itself in the appearance of the moir fringes during the TEM observation of some of the nanotubes and nanofibers. Analysis of these fringes has shown that the facets of these nanotubes represent the slightly misoriented hexagonal BN and/or C plates. An Al(2)O(3) filling of the nanotube makes it harder to twist when subjected to torque, which conforms to the tube deformation theory.

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