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322 results on '"Ralchenko, V. G."'

5. Uniform diamond coatings on WC-Co hard alloy cutting inserts deposited by a microwave plasma CVD

Author

Ashkihazi, E. E., Sedov, V. S., Sovyk, D. N., Khomich, A. A., Bolshakov, A. P., Ryzhkov, S. G., Khomich, A. V., Vinogradov, D. V., Ralchenko, V. G., and Konov, V. I.

Subjects
Condensed Matter - Materials Science
Abstract

Polycrystalline diamond coatings have been grown on cemented carbide substrates with different aspect ratios by a microwave plasma CVD in methane-hydrogen gas mixtures. To protect the edges of the substrates from non-uniform heating due to the plasma edge effect, a special plateholder with pockets for group growth has been used. The difference in heights of the substrates and plateholder, and its influence on the diamond film mean grain size, growth rate, phase composition and stress was investigated. The substrate temperature range, within which uniform diamond films are produced with good adhesion, is determined. The diamond-coated cutting inserts produced at optimized process exhibited a reduction of cutting force and wear resistance by a factor of two, and cutting efficiency increase by 4.3 times upon turning A390 Al-Si alloy as compared to performance of uncoated tools., Comment: 17 pages, 3 tables, 5 figures

Published
2017

7. Comparison оf Secondary Nucleation Processes during Diamond Synthesis in Microwave Plasma in H2–CH4–N2 and H2–CH4–NH3 Gas Mixtures.

Author

Martyanov, A. K., Tyazhelov, I. A., Popovich, A. F., Ralchenko, V. G., Savin, S. S., and Sedov, V. S.

Abstract

For the first time, the secondary diamond nucleation processes are compared during the growth of polycrystalline diamond films by the MPCVD method with addition of nitrogen and ammonia. An ammonia molecule (NH3) has a lower ionization energy than a nitrogen molecule (N2) in microwave plasma. It has been established that when using ammonia, the transition to the nanocrystalline structure of diamond occurs at significantly lower concentrations than when using nitrogen. [ABSTRACT FROM AUTHOR]

Published
2024
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8. Channeling Effect in Polycrystalline Deuterium-Saturated CVD Diamond Target Bombarded by Deuterium Ion Beam

Author

Bagulya, A. V., Dalkarov, O. D., Negodaev, M. A., Rusetskii, A. S., Chubenko, A. P., Ralchenko, V. G., and Bolshakov, A. P.

Subjects
Physics - Instrumentation and Detectors, Nuclear Experiment
Abstract

At the ion accelerator HELIS at the LPI, the neutron yield is investigated in DD reactions within a polycrystalline deuterium-saturated CVD diamond, during an irradiation of its surface by a deuterium ion beam with the energy less than 30 keV. The measurements of the neutron flux in the beam direction are performed in dependence on the target angle, \b{eta}, with respect to the beam axis. These measurements are performed using a multichannel detector based on He3 counters. A significant anisotropy in neutron yield is observed, it was higher by a factor of 3 at \b{eta}=0 compared to that at \b{eta} = +-45{\deg}. The possible reasons for the anisotropy, including ion channeling, are discussed., Comment: 8 pages, 3 figures, preprint LPI

Published
2014
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9. Thermal conductivity of pink CVD diamond: Influence of nitrogen-related centers.

Author

Inyushkin, A. V., Taldenkov, A. N., Ralchenko, V. G., Shu, Guoyang, Dai, Bing, Bolshakov, A. P., Khomich, A. A., Ashkinazi, E. E., Boldyrev, K. N., Khomich, A. V., Han, Jiecai, Konov, V. I., and Zhu, Jiaqi

Subjects
THERMAL conductivity, IMPURITY centers, PHONON scattering, DIAMONDS, CHARGE carriers, ELASTIC scattering, PINK
Abstract

Thermal conductivity κ (T) of single-crystal CVD diamond lightly doped (about 3 ppm) with nitrogen has been measured at temperatures from 5.7 to 410 K. The sample was carefully characterized by optical absorption and photoluminescence spectroscopy for the presence of impurities. Nine different optically active defects related with nitrogen, hydrogen, and silicon impurities have been identified and quantified. This pink-tint crystal showed a high thermal conductivity of 24.0 ± 0.5 W cm − 1 K − 1 at room temperature, which is very close to the highest value ever measured at about 25 W cm − 1 K − 1 for diamonds of natural isotopic composition. At the same time, the κ (T) of the crystal showed strong suppression > --> 10 % at temperatures 6 < T < 120 K with a maximum decrease of 2.7 times at ≈ 40 K compared to high purity diamonds. This behavior of the conductivity is attributed to a phonon scattering by charge carriers bound to nitrogen-related impurity centers, which is ineffective, however, at room and higher temperatures. The κ (T) has been calculated within the model based on the Callaway theory taking into account the elastic phonon scattering off charge carriers (holes and electrons) in the ground states of doping centers, and a very good agreement between the measured and theoretical data has been achieved. The model also gives a good approximation to the experimental data for κ (T) given in the literature for synthetic and natural single-crystal diamonds. [ABSTRACT FROM AUTHOR]

Published
2023
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12. Behaviour of a muonic atom as an acceptor centre in diamond

Author

Mamedov, T. N., Baturin, A. S., Gritsaj, K. I., Maisuradze, A., Ralchenko, V. G., Scheuermann, R., Sedlak, K., and Stoykov, A. V.

Subjects
Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

Polarized negative muons were used to study the behaviour of the boron acceptor centre in synthetic diamond produced by the chemical vapour deposition (CVD) method. The negative muon substitutes one of the electrons in a carbon atom, and this muonic atom imitates the boron acceptor impurity in diamond. The temperature dependence of the muon spin relaxation rate and spin precession frequency were measured in the range of 20 - 330 K in a transverse magnetic field of 14 kOe. For the first time a negative shift of the muon spin precession was observed in diamond. It is tentatively attributed to an anisotropic hyperfine interaction in the boron acceptor. The magnetic measurements showed that the magnetic susceptibility of the CVD sample was close to that of the purest natural diamond., Comment: 8 pages, 3 figures

Published
2013
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14. Behaviour of muonium in synthetic diamond

Author

Mamedov, T. N., Blank, V. D., Gorelkin, V. N., Gritsaj, K. I., Kuznetsov, M. S., Nosukhin, S. A., Ralchenko, V. G., Stoykov, A. V., Scheuermann, R., and Terentiev, S. A.

Subjects
Condensed Matter - Other Condensed Matter, Physics - Instrumentation and Detectors
Abstract

The probabilities of finding the muon in various states in synthetic single crystal and polycrystalline diamond were studied. In the IIa-type single-crystal sample at 150 K the contributions of the diamagnetic muon, `normal', and `anomalous' muonium were observed to be 1.5 %, 57 % and 8.1 %, respectively. The missing fraction of muon polarization was 33.4 %, which is approximately two times smaller than in the Ia-type natural diamond, and two or three times greater than in the IIa- and IIb-type natural diamonds. The muon spin relaxation rates at the `normal' and `anomalous' muonium states in the synthetic and natural samples of IIa- and IIb-type are similar., Comment: 9 pages, 4(7) figure

Published
2010

20. Synthesis of the Diamond‒SiO2Composites with the Properties of Photonic Crystals in the Visible Spectral Range.

Author

Sovyk, D. N., Odintsov, K. A., Bolshakov, A. P., Dyakov, S. A., Savin, S. S., Fedorova, I. A., Yurov, V. Yu., Masalov, V. M., Ralchenko, V. G., and Konov, V. I.

Subjects
PHOTONIC crystals, CHEMICAL vapor deposition
Abstract

The chemical vapor deposition synthesis of periodic structures in the form of single-crystal diamond–SiO2 nanosphere composites, which exhibit the properties of photonic crystals in the visible spectral range, are reported. [ABSTRACT FROM AUTHOR]

Published
2023
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24. On the thermal conductivity of single crystal AlN.

Author

Inyushkin, A. V., Taldenkov, A. N., Chernodubov, D. A., Mokhov, E. N., Nagalyuk, S. S., Ralchenko, V. G., and Khomich, A. A.

Subjects
SINGLE crystals, PHONON scattering, ALUMINUM nitride, ALUMINUM crystals, THERMAL conductivity, POINT defects, ELECTRON donors
Abstract

Thermal conductivity κ (T) of single crystal aluminum nitride grown by physical vapor transport has been measured at temperatures T from 5 to 410 K. The samples exhibit high thermal conductivity with a value of up to 316 W m − 1 K − 1 at room temperature and about 2800 W m − 1 K − 1 at a peak of 66 K. At lowest temperatures, κ (T) approaches the conductivity limited by the diffuse phonon scattering from sample surfaces. The peculiarities in measured κ (T) suggest that the phonon scattering from point defects contributes essentially to the total phonon scattering in samples under investigation at low temperatures. The phonon interaction with electrons and holes bound to neutral donor and acceptor centers is suggested, adding substantially to thermal resistivity near and below the peak in κ (T). [ABSTRACT FROM AUTHOR]

Published
2020
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36. Chemical Vapor Deposition of Diamond Films on Diamond Compacts

Author

Ralchenko, V. G., Pimenov, S. M., Pereverzev, V. G., Vlasov, I. I., Lavrischev, S. V., Obraztsova, E. D., Konov, V. I., Shorokhov, E. V., Lebedev, D. M., Lebedev, M. A., Vodolaga, B. K., Loubnin, E. N., Spivak, V. A., Prelas, Mark A., editor, Benedictus, Andrew, editor, Lin, Li-Te Steven, editor, Popovici, Galina, editor, and Gielisse, Peter, editor

Published
1997
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43. Study of color centers in radiation-modified diamonds

Author

Kozlova, M V, primary, Khomich, A A, additional, Khmelnitsky, R A, additional, Averin, A A, additional, Kovalev, A I, additional, Poklonskaya, O N, additional, Vlasov, I I, additional, Khomich, A V, additional, and Ralchenko, V G, additional

Published
2021
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45. Near-infrared refractive index of synthetic single crystal and polycrystalline diamonds at high temperatures.

Author

Yurov, V. Yu., Bushuev, E. V., Popovich, A. F., Bolshakov, A. P., Ashkinazi, E. E., and Ralchenko, V. G.

Subjects
DIAMONDS spectra, REFRACTIVE index, HIGH temperatures, SINGLE crystals spectra, POLYCRYSTALS, NEAR infrared radiation
Abstract

We measured the refractive index n(T) and thermo-optical coefficient β(T)=(1/n)(dn/dT) of high quality synthetic diamonds from room temperature to high temperatures, up to 1520K, in near-infrared spectral range at wavelength 1.56 μm, using a low-coherence interferometry. A type IIa single crystal diamond produced by high pressure-high temperature technique and a transparent polycrystalline diamond grown by chemical vapor deposition were tested and revealed a very close n(T) behavior, with n=2.38460.001 ± T=300 K, monotonically increasing to 2.428 at 1520K. The n(T) data corrected to thermal expansion of diamond are well fitted with 3rd order polynomials, and alternatively, with the Bose-Einstein model with an effective oscillator frequency of 970 cm-1. Almost linear n(T) dependence is observed above 800 K. The thermo-optical coefficient is found to increase monotonically from (0.6±0.1) × 10-5K-1 (300K) to (2.0±0.1) × 10-5K-1 (1300 K) with a tendency to saturation at >1200 K. These β(T) values are an order of magnitude lower than those known for Si, GaAs, and InP. The obtained results significantly extend the temperature range, where the refractive index of diamond was previously measured. [ABSTRACT FROM AUTHOR]

Published
2017
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