Dr. Vasylkiv is currently researching the engineering of ultra-high-temperature carbides, borides, nitrides, oxides, and composites. Oleg has combined the merits of powder synthesis and the electric current activated sintering technique for the design of technologies applied on powder bodies with establishing morpho-structural and compositional features, which led to the fabrication of bulk deformation-resistant ultra-high-temperature ceramics with superior hardness and flexural strength.
Journal of the American Ceramic Society, Dec 20, 2004
To obtain powder with a composition of 3 mol% Y2O3–97 mol% ZrO2, a process of Y-Zr oxalate powder... more To obtain powder with a composition of 3 mol% Y2O3–97 mol% ZrO2, a process of Y-Zr oxalate powder production has been optimized, to produce an oxalate with minimal particle size. The methodology of the nonisothermal decomposition of Y-Zr oxalate has been explained. Characteristics of the nonisothermal decomposition of different oxalates have been studied. Nanocrystalline Y2O3-stabilized ZrO2 (YSZ) powder with a narrow size distribution of primary particles and aggregates was produced. The zirconia powder that was obtained from the smallest oxalate powder via nonisothermal decomposition had a particle size of 8–10 nm. The YSZ powder was weakly aggregated, with a narrow aggregate-size distribution of 70–90 nm.
Preprints of Annual Meeting of The Ceramic Society of Japan Preprints of Fall Meeting of The Ceramic Society of Japan 18th Fall Meeting of The Ceramic Society of Japan & 1st Asia-Oceania Ceramic Federation (AOCF) Conference, 2005
Journal of the American Ceramic Society, Sep 24, 2015
In this study, we introduce a simple and effective seed-mediated growth method (SMGM) for the con... more In this study, we introduce a simple and effective seed-mediated growth method (SMGM) for the controlled synthesis of boron suboxide powder. By employing starting powders with different concentrations and adding boron suboxide seeds with a star-like morphology, we demonstrate that B6O ceramics that exhibit high-level crystallinity can be synthesized using SMGM at ambient pressure conditions. The formation of multilayered star-shaped B6O particles via SMGM is reported for the first time.
The 0.75 to 3 mol% Y2O3-stabilized tetragonal ZrO2 and Al2O3/Y-TZP nano-composite ceramics with 0... more The 0.75 to 3 mol% Y2O3-stabilized tetragonal ZrO2 and Al2O3/Y-TZP nano-composite ceramics with 0.2 to 0.7 wt% of alumina were produced by a colloidal technique and low-temperature sintering. The influence of the resulting density, microstructure, the yttria-stabilizer and the alumina content on toughness was determined. The bulk 2.7Y-TZP ceramic with an average grain size of 110 nm reached fracture toughness of 11.2 MPa·m1/2. A nano-grained alumina/zirconia composite with an average grain size of 92 nm was obtained. Y-TZP ceramics with a reduced yttria-stabilizer content were shown to reach fracture toughness of 13.8 MPa·m1/2 (2Y-TZP), and 14.5 MPa·m1/2 (1.5Y-TZP). Y-TZP/alumina composites with 0.35 wt% of Al2O3 were shown to reach fracture toughness of 15.7 MPa·m1/2 (2Y), 15.3 MPa·m1/2 (1.5Y).
Journal of the American Ceramic Society, Mar 1, 2005
A uniformly aggregated 3 mol% yttria‐stabilized tetragonal zirconia nano‐powder (3Y‐TZP) was prep... more A uniformly aggregated 3 mol% yttria‐stabilized tetragonal zirconia nano‐powder (3Y‐TZP) was prepared using thermal hydrolysis and the ultrasonic deagglomeration technique. The possibility of nano‐engineering of Pt–3Y‐TZP composite aggregates was studied. The as‐synthesized Pt nano‐particles (∼2 nm) were impregnated into zirconia nano‐aggregates (20–45 nm). The morphology manipulation technique allowed production of the composite zirconia‐based aggregates in which a significant fraction of the Pt particles was embedded into the densified zirconia aggregates. Using the colloidal technique and low‐temperature (1150°C) sintering, we prepared the Pt‐zirconia (0.5–1.5 wt% of platinum) nano‐composites with average 3Y‐TZP grain sizes of 120 nm, and with the platinum grains size in the range of 20–60 nm. The catalytic properties of composite Pt–3Y‐TZP nano‐composites were studied and described.
We demonstrate the methodology of engineering the multi-component ceramic nanopowder with precise... more We demonstrate the methodology of engineering the multi-component ceramic nanopowder with precise morphology by ‘nano-blast’ calcinations decomposition of preliminary engineered nanoreactors. Multiple explosions of just melted C3H6N6O6 embedded into preliminary engineered nanoreactors break apart the agglomerates due to the highly energetic impacts of the blast waves. Also, the solid-solubility of one component into the other is enhanced by the extremely high local temperature generated during each nano-explosion in surrounding area. This methodology was applied for production of agglomerate-free nanoaggregates of Gd20Ce80O1.95 with an average size of 42 nm and LaSrGaMgO3-x nanopowder with an average aggregate size of 83 nm.
ABSTRACT Sintered bulks require new approaches for the control and improvement of their functiona... more ABSTRACT Sintered bulks require new approaches for the control and improvement of their functional characteristics. Nanostructuring, synergy effects at interfaces in a composite, and technology specific features are essential in this regard. In this work, for a better understanding of challenges, complex relationships between materials and technology and different practical concepts such as "transferability", "composite within a composite", and "multilevel design", and "multifunctionality", a comparative analysis is proposed for very different nano structured materials such as La0.9Sr0.1Ga0.8Mg0.2O3-x x solid electrolyte, hard B4C-based materials, and doped MgB2 superconductors. Samples were obtained by reactive spark plasma sintering (SPS). SPS is reconfirmed as a powerful processing technique that generates high-density unique bulk materials impossible to fabricate by other methods. However, it is shown that SPS is not universal and its suitability should be carefully considered depending on materials and targeted applications. (C) 2014 The Japan Society of Applied Physics
The possibility of preparation of Pt–3Y-TZP and Pd–3Y-TZP nano-composites was studied. The sonoch... more The possibility of preparation of Pt–3Y-TZP and Pd–3Y-TZP nano-composites was studied. The sonochemically synthesized Pt (Pd) nano-particles (~2 nm) were impregnated into the zirconia nano-aggregates (20 – 45nm). The complex morphology manipulation technique allowed production of the composite zirconia-based aggregates in which a significant fraction of the Pt or Pd crystallites was embedded into the zirconia dense aggregates. The catalytic properties of composite Pt–3Y-TZP nano-composites were studied and described.
Abstract This study demonstrates that reactive consolidation achieved via spark plasma sintering ... more Abstract This study demonstrates that reactive consolidation achieved via spark plasma sintering (SPS) is an effective strategy to enhance the high-temperature flexural strength of TiB 2 -based ceramics. Monolithic ceramics of TaC and TiB 2 were consolidated by non-reactive SPS and were used as reference samples. The microstructural development during room- and high-temperature strength tests was analyzed. The room-temperature strength of TiB 2 ceramics was analyzed as a function of the grain size. The high-temperature strength and associated microstructural development of monolithic TaC ceramics are reported for the first time. The TiB 2 –TaC ceramic system was then consolidated by reactive SPS at 2000 °C. The flexural strength of the 10 wt% TaC–TiB 2 ceramic composites reached 533 MPa at room temperature and 480 MPa at 1600 °С. The development of the (Ti,Ta)(C,B) phase was considered the main reason for the preservation of the high strength up to 1600 °С. Both bulk TaC and TiB 2 exhibited drastic decreases in their bending strengths at 1600 °С because of the activation of plastic deformation associated with high-temperature creep, and their strength did not exceed 210 MPa.
Journal of the American Ceramic Society, Dec 20, 2004
To obtain powder with a composition of 3 mol% Y2O3–97 mol% ZrO2, a process of Y-Zr oxalate powder... more To obtain powder with a composition of 3 mol% Y2O3–97 mol% ZrO2, a process of Y-Zr oxalate powder production has been optimized, to produce an oxalate with minimal particle size. The methodology of the nonisothermal decomposition of Y-Zr oxalate has been explained. Characteristics of the nonisothermal decomposition of different oxalates have been studied. Nanocrystalline Y2O3-stabilized ZrO2 (YSZ) powder with a narrow size distribution of primary particles and aggregates was produced. The zirconia powder that was obtained from the smallest oxalate powder via nonisothermal decomposition had a particle size of 8–10 nm. The YSZ powder was weakly aggregated, with a narrow aggregate-size distribution of 70–90 nm.
Preprints of Annual Meeting of The Ceramic Society of Japan Preprints of Fall Meeting of The Ceramic Society of Japan 18th Fall Meeting of The Ceramic Society of Japan & 1st Asia-Oceania Ceramic Federation (AOCF) Conference, 2005
Journal of the American Ceramic Society, Sep 24, 2015
In this study, we introduce a simple and effective seed-mediated growth method (SMGM) for the con... more In this study, we introduce a simple and effective seed-mediated growth method (SMGM) for the controlled synthesis of boron suboxide powder. By employing starting powders with different concentrations and adding boron suboxide seeds with a star-like morphology, we demonstrate that B6O ceramics that exhibit high-level crystallinity can be synthesized using SMGM at ambient pressure conditions. The formation of multilayered star-shaped B6O particles via SMGM is reported for the first time.
The 0.75 to 3 mol% Y2O3-stabilized tetragonal ZrO2 and Al2O3/Y-TZP nano-composite ceramics with 0... more The 0.75 to 3 mol% Y2O3-stabilized tetragonal ZrO2 and Al2O3/Y-TZP nano-composite ceramics with 0.2 to 0.7 wt% of alumina were produced by a colloidal technique and low-temperature sintering. The influence of the resulting density, microstructure, the yttria-stabilizer and the alumina content on toughness was determined. The bulk 2.7Y-TZP ceramic with an average grain size of 110 nm reached fracture toughness of 11.2 MPa·m1/2. A nano-grained alumina/zirconia composite with an average grain size of 92 nm was obtained. Y-TZP ceramics with a reduced yttria-stabilizer content were shown to reach fracture toughness of 13.8 MPa·m1/2 (2Y-TZP), and 14.5 MPa·m1/2 (1.5Y-TZP). Y-TZP/alumina composites with 0.35 wt% of Al2O3 were shown to reach fracture toughness of 15.7 MPa·m1/2 (2Y), 15.3 MPa·m1/2 (1.5Y).
Journal of the American Ceramic Society, Mar 1, 2005
A uniformly aggregated 3 mol% yttria‐stabilized tetragonal zirconia nano‐powder (3Y‐TZP) was prep... more A uniformly aggregated 3 mol% yttria‐stabilized tetragonal zirconia nano‐powder (3Y‐TZP) was prepared using thermal hydrolysis and the ultrasonic deagglomeration technique. The possibility of nano‐engineering of Pt–3Y‐TZP composite aggregates was studied. The as‐synthesized Pt nano‐particles (∼2 nm) were impregnated into zirconia nano‐aggregates (20–45 nm). The morphology manipulation technique allowed production of the composite zirconia‐based aggregates in which a significant fraction of the Pt particles was embedded into the densified zirconia aggregates. Using the colloidal technique and low‐temperature (1150°C) sintering, we prepared the Pt‐zirconia (0.5–1.5 wt% of platinum) nano‐composites with average 3Y‐TZP grain sizes of 120 nm, and with the platinum grains size in the range of 20–60 nm. The catalytic properties of composite Pt–3Y‐TZP nano‐composites were studied and described.
We demonstrate the methodology of engineering the multi-component ceramic nanopowder with precise... more We demonstrate the methodology of engineering the multi-component ceramic nanopowder with precise morphology by ‘nano-blast’ calcinations decomposition of preliminary engineered nanoreactors. Multiple explosions of just melted C3H6N6O6 embedded into preliminary engineered nanoreactors break apart the agglomerates due to the highly energetic impacts of the blast waves. Also, the solid-solubility of one component into the other is enhanced by the extremely high local temperature generated during each nano-explosion in surrounding area. This methodology was applied for production of agglomerate-free nanoaggregates of Gd20Ce80O1.95 with an average size of 42 nm and LaSrGaMgO3-x nanopowder with an average aggregate size of 83 nm.
ABSTRACT Sintered bulks require new approaches for the control and improvement of their functiona... more ABSTRACT Sintered bulks require new approaches for the control and improvement of their functional characteristics. Nanostructuring, synergy effects at interfaces in a composite, and technology specific features are essential in this regard. In this work, for a better understanding of challenges, complex relationships between materials and technology and different practical concepts such as "transferability", "composite within a composite", and "multilevel design", and "multifunctionality", a comparative analysis is proposed for very different nano structured materials such as La0.9Sr0.1Ga0.8Mg0.2O3-x x solid electrolyte, hard B4C-based materials, and doped MgB2 superconductors. Samples were obtained by reactive spark plasma sintering (SPS). SPS is reconfirmed as a powerful processing technique that generates high-density unique bulk materials impossible to fabricate by other methods. However, it is shown that SPS is not universal and its suitability should be carefully considered depending on materials and targeted applications. (C) 2014 The Japan Society of Applied Physics
The possibility of preparation of Pt–3Y-TZP and Pd–3Y-TZP nano-composites was studied. The sonoch... more The possibility of preparation of Pt–3Y-TZP and Pd–3Y-TZP nano-composites was studied. The sonochemically synthesized Pt (Pd) nano-particles (~2 nm) were impregnated into the zirconia nano-aggregates (20 – 45nm). The complex morphology manipulation technique allowed production of the composite zirconia-based aggregates in which a significant fraction of the Pt or Pd crystallites was embedded into the zirconia dense aggregates. The catalytic properties of composite Pt–3Y-TZP nano-composites were studied and described.
Abstract This study demonstrates that reactive consolidation achieved via spark plasma sintering ... more Abstract This study demonstrates that reactive consolidation achieved via spark plasma sintering (SPS) is an effective strategy to enhance the high-temperature flexural strength of TiB 2 -based ceramics. Monolithic ceramics of TaC and TiB 2 were consolidated by non-reactive SPS and were used as reference samples. The microstructural development during room- and high-temperature strength tests was analyzed. The room-temperature strength of TiB 2 ceramics was analyzed as a function of the grain size. The high-temperature strength and associated microstructural development of monolithic TaC ceramics are reported for the first time. The TiB 2 –TaC ceramic system was then consolidated by reactive SPS at 2000 °C. The flexural strength of the 10 wt% TaC–TiB 2 ceramic composites reached 533 MPa at room temperature and 480 MPa at 1600 °С. The development of the (Ti,Ta)(C,B) phase was considered the main reason for the preservation of the high strength up to 1600 °С. Both bulk TaC and TiB 2 exhibited drastic decreases in their bending strengths at 1600 °С because of the activation of plastic deformation associated with high-temperature creep, and their strength did not exceed 210 MPa.
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Papers by Oleg O . Vasylkiv