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  • 1
    Online Resource
    Online Resource
    Structure and Properties of NbMoCrTiAl High-Entropy Alloy Coatings Formed by Plasma-Assisted Vacuum Arc Deposition
    MDPI AG ; 2023
    In:  Coatings Vol. 13, No. 7 ( 2023-07-02), p. 1191-
    Details
    In: Coatings, MDPI AG, Vol. 13, No. 7 ( 2023-07-02), p. 1191-
    Abstract: The paper analyzes the structure and properties of metal, cermet, and ceramic NbMoCrTiAl high-entropy alloy (HEA) coatings formed on solid substrates by plasma-assisted vacuum arc deposition (from multicomponent gas-metal plasma through Nb, Mo, Cr, and TiAl cathode evaporation in argon and/or a mixture of argon and nitrogen). The analysis shows that all coatings represent a nanocrystalline (3–5 nm) multilayer film. The metal coating has a bcc lattice (a = 0.3146 nm). The ceramic coating has an fcc lattice (an uncertain lattice parameter due to highly smeared diffraction peaks). The coating hardness increases in the order of metal, cermet, and then ceramic, reaching 43 GPa at Young’s modulus equal to 326 GPa. When heated in air, the metal and cermet coatings start to oxidize at 630–640 °C, and the ceramic coating at 770–780 °C.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    URL: Article
    DOI: 10.3390/coatings13071191
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662314-6
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  • 2
    Online Resource
    Online Resource
    Study of The Gas-Swelling Mechanisms in Silicon Carbide Ceramics under High-Temperature Irradiation with Helium Ions
    MDPI AG ; 2023
    In:  Materials Vol. 16, No. 17 ( 2023-08-22), p. 5750-
    Details
    In: Materials, MDPI AG, Vol. 16, No. 17 ( 2023-08-22), p. 5750-
    Abstract: The purpose of this work is to simulate the processes of gaseous swelling in SiC ceramics as well as the associated changes in strength and thermophysical properties under high-temperature irradiation with helium ions. The choices of irradiation conditions (irradiation temperatures of 700 and 1000 K) and irradiation fluences (1015–1018 ion/cm2) are based on the possibilities of modeling the processes of destructive changes in the near-surface layer as a result of the accumulation of gas-filled inclusions during high-dose irradiation. During this study, it was found that an increase in the irradiation temperature of the samples from 700 to 1000 K leads to a decrease in the resistance to gas swelling, since with the temperature increase, the mobility of implanted helium in the near-surface layer grows, which results in an increase in the size of gas-filled bubbles and, as a result, accelerated destruction of the damaged layer. It has been established that in the case of irradiation at 700 K, the critical fluence for swelling associated with the formation of visible gas-filled bubbles on the surface is 5 × 1017 ion/cm2, while for samples irradiated at a temperature of 1000 K, the formation of gas-filled bubbles is observed at a fluence of 1017 ion/cm2. Measurements of the thermal conductivity coefficient showed that the formation of gas-filled bubbles leads to a sharp deterioration in heat transfer processes, which indicates that the created defective inclusions prevent phonon heat transfer. Changes in the strength characteristics showed that a decrease in hardness occurs throughout the entire depth of the damaged ceramic layer. However, with a rise in the irradiation fluence above 1017 ion/cm2, a slight damaged layer thickness growth associated with diffusion processes of helium implantation into the near-surface layer is observed. The relevance of this study consists in obtaining new data on the stability of the strength and thermophysical parameters of SiC ceramics in the case of helium accumulation and its subsequent radiation-induced evolution in the case of irradiation at temperatures of 700 and 1000 K. The data obtained during the experimental work on changes in the properties of ceramics will make it possible to determine the potential limits of their applicability in the case of operation under extreme conditions at elevated temperatures in the future.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma16175750
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2487261-1
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  • 3
    Online Resource
    Online Resource
    Study of the Radiation Damage Kinetics in NbTiVZr High-Entropy Alloys Irradiated by Heavy Ions
    MDPI AG ; 2023
    In:  Metals Vol. 13, No. 4 ( 2023-04-07), p. 727-
    Details
    In: Metals, MDPI AG, Vol. 13, No. 4 ( 2023-04-07), p. 727-
    Abstract: The purpose of this paper was to study the kinetics of accumulation of radiation damage in the near-surface layer of a high-entropy NbTiVZr alloy upon irradiation with heavy Kr15+ ions and fluences of 1010–1015 ion/cm2. According to the data of X-ray diffraction analysis, it was found that irradiation with heavy ions lead to structural changes associated with the accumulation of deformation distortions and stresses. In this case, the nature of deformation distortions was associated with tensile distortions of the crystal lattice and swelling of the near-surface layer. An analysis of the strength properties of the irradiated samples showed that the accumulation of deformation distortions in the near-surface layer lead to a decrease in the resistance to cracking and destruction of the near-surface layer. In this case, the main changes occurred at fluences above 1013 ion/cm2, which are characterized by an excess of the threshold for overlapping defective regions that appear along the trajectory of incident ions. Tribological tests showed that an increase in defective inclusions in the structure of the near-surface layer lead to an increase in friction and a decrease in crack resistance.
    Type of Medium: Online Resource
    ISSN: 2075-4701
    URL: Article
    DOI: 10.3390/met13040727
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662252-X
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  • 4
    Online Resource
    Online Resource
    Study of Changes in Optical and Heat-Conducting Properties of AlN Ceramics under Irradiation with Kr15+ and Xe22+ Heavy Ions
    MDPI AG ; 2020
    In:  Nanomaterials Vol. 10, No. 12 ( 2020-11-28), p. 2375-
    Details
    In: Nanomaterials, MDPI AG, Vol. 10, No. 12 ( 2020-11-28), p. 2375-
    Abstract: AlN-based ceramics have great prospects for use in the field of structural materials for reactors of the new generation of GenIV, as well as dosimetric and optical devices. Interest in them is due to their unique physical and chemical properties, high resistance to degradation and excellent insulating properties. This work is devoted to the study of changes in the optical and heat-conducting properties of AlN ceramics as a result of irradiation with Kr15+ and Xe22+ heavy ions with energies close to those of fission fragments of uranium nuclei, and fluences 1014–1015 ion/cm2. During the study, dose relationships of changes in the optical properties of ceramics were established, as well as the effect of the type of ions on the degree of radiation damage and deterioration of optical characteristics. It has been found that an increase in the irradiation dose for Kr15+ ions leads to a slight increase in the depth of electron traps, while for samples irradiated with Xe22+ ions there is a sharp increase in the depth of occurrence from 5 to 20%, depending on the irradiation dose. For samples irradiated with Xe22+ ions, the greatest decrease in thermal conductivity was 19%, while for ceramics irradiated with Kr15+ ions, the maximum decrease was not more than 10%. The results show a significant resistance of ceramics to radiation damage by Kr15+ ions and negative effects, leading to a decrease in the resistance of optical and conductive properties of ceramics when irradiated with Xe22+ ions with doses higher than 5 × 1014 ion/cm2. Using the X-ray diffraction method, the dependences of structural distortions and changes in dislocation density in the structure of ceramics on the radiation dose were established. It has been determined that the main structural changes are associated with the fragmentation of grains, which result in an increase in the dislocation density, as well as deformation and distortion of the crystal lattice as a result of the formation of complex defects in the structure.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano10122375
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2662255-5
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  • 5
    Online Resource
    Online Resource
    Study of the Mechanisms of Radiation Softening and Swelling upon Irradiation of TiTaNbV Alloys with He2+ Ions with an Energy of 40 keV
    MDPI AG ; 2023
    In:  Materials Vol. 16, No. 11 ( 2023-05-28), p. 4031-
    Details
    In: Materials, MDPI AG, Vol. 16, No. 11 ( 2023-05-28), p. 4031-
    Abstract: This paper presents simulation results of the ionization losses of incident He2+ ions with an energy of 40 keV during the passage of incident ions in the near-surface layer of alloys based on TiTaNbV with a variation of alloy components. For comparison, data on the ionization losses of incident He2+ ions in pure niobium, followed by the addition of vanadium, tantalum, and titanium to the alloy in equal stoichiometric proportions, are presented. With the use of indentation methods, the dependences of the change in the strength properties of the near-surface layer of alloys were determined. It was established that the addition of Ti to the composition of the alloy leads to an increase in resistance to crack resistance under high-dose irradiation, as well as a decrease in the degree of swelling of the near-surface layer. During tests on the thermal stability of irradiated samples, it was found that swelling and degradation of the near-surface layer of pure niobium affects the rate of oxidation and subsequent degradation, while for high-entropy alloys, an increase in the number of alloy components leads to an increase in resistance to destruction.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma16114031
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2487261-1
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  • 6
    Online Resource
    Online Resource
    Study of the Reinforcement Effect in (0.5–x)TeO2–0.2WO3–0.1Bi2O3–0.1MoO3–0.1SiO2–xCNDs Glasses Doped with Carbon Nanodiamonds
    MDPI AG ; 2022
    In:  Nanomaterials Vol. 12, No. 19 ( 2022-09-23), p. 3310-
    Details
    In: Nanomaterials, MDPI AG, Vol. 12, No. 19 ( 2022-09-23), p. 3310-
    Abstract: The purpose of this study is to examine the influence of carbon nanodiamonds on the reinforcement and hardening of telluride glasses, as well as to establish the dependence of the strengthening properties and optical characteristics of glasses on CND concentration. According to X-ray diffraction data, the synthesized glasses have an amorphous structure despite the addition of CNDs, and at high concentrations of CNDs, reflections characteristic of small crystalline particles of carbon nanodiamonds are observed. An analysis of the strength properties of glasses depending on the concentration of the CND dopant showed that an increase in the CND concentration to 0.10–0.15 mol. leads to an increase in hardness by 33–50% in comparison with undoped samples. The studies carried out to determine the resistance to external influences found that doping leads to an increase in the resistance of strength characteristics against destruction and embrittlement, and in the case of high concentrations, the change in strength properties is minimal, which indicates a high ceramic stability degree. The study of the radiation resistance of synthesized glasses found that the addition of CNDs leads to an increase in resistance to radiation damage when irradiated with gamma rays, while also maintaining resistance to high radiation doses. The study of the shielding characteristics found that the addition of CNDs is most effective in shielding gamma rays with energies of 130–660 MeV.
    Type of Medium: Online Resource
    ISSN: 2079-4991
    URL: Article
    DOI: 10.3390/nano12193310
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2662255-5
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