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Keywords

materials science, ceramic engineering, nano-engineering, nano-composites, electric current assisted sintering techniques (ECAST: SPS, reaction-driven spark plasma sintering (RD-SPS), 'flash sintering, 'flash'-SPS), nano-powders, nano-ceramic & composites, hard ceramic, tough ceramic, flexural strength behavior, ultra-high temperature ceramic (UHTC), ultra-high elevated temperature strength, superplasticity of brittle hard ceramics, dynamic toughness, highly ordered nano-scale structures, self-assembled magnetite-chitosan nanostructures, boron carbide, boron suboxide, titanium diboride, tantalum boride, tantalum carbide, niobium boride, niobium carbide, zirconium boride, hafnium boride, silicon carbide,vanadium diboride, zirconium oxide, energetic materials, nano-explosive synthesis, multication nanopowders, etc.

Improving application performance and developing new ones requires sourcing, designing, and acquiring novel materials. The demand for ultra-high temperature ceramics (UHTCs) is increasing, especially those that are multipurpose, deformation-resistant, and offer specialized protection for engines and vehicles. These ceramics are vital for segmented leading-edge components in aerospace, plasma-facing components, and ceramic parts in solar towers and gas turbines in combined cycle power plants, along with essential infrastructure like grids and steam turbines. Consequently, there is a global need for a new class of ceramic composites with exceptional strength and a balanced mix of toughness, hardness, and modulus. Over the past decade, I have investigated the chemical and structural engineering of deformation-resistant carbides, borides, and nitrides in Me (IV-V) ceramic composites, recognized for their superior hardness, toughness, and flexural strength under extreme temperatures. Additionally, I'm researching mechanisms behind high-temperature flexural strengthening and ductility, focusing on the transition in deformation mechanisms from brittle fracture to plastic deformation in transition metal carbides, borides, and nitrides. Key studies include: (1) High-temperature flexure in bulk polycrystalline boron carbide, where at temperatures above 2000 °C, it demonstrates flexural strength over 1.8 GPa and transitions from brittle to plastic behavior, with amorphization in highly deformed grains. (2) Transforming the performance of silicon carbide by revealing a self-strengthening mechanism that improves durability under extreme temperatures. Additive-free alpha-SiC exhibits a flexural strength that increases with temperature. Under rapid loading conditions at 2000°C, it achieves a peak strength of 2.1 GPa, indicating unprecedented mechanical stability. An increase in twin density and stacking fault formation confirms a self-reinforcing process that activates under stress, ensuring the long-term integrity of the material. (3) Ultrahard Zr-Ta multiboride with an artificially created repetitive hierarchical superstructure via RD-SPS. Ta3B4 forms a chain-like mesh that entraps the ZrB2, ZrB, TaB, and (Zr, Ta)B2 solid solution multiboride ceramic, exhibiting ultra-hardness of 28 GPa at 98 N and 22 GPa at 196 N and the flexural strength of 400 MPa up to 2000 °C. (4) Study of Ta0.2Hf0.8C solid-solution ceramics that retain toughness and strength at 2000 °C, synthesized via SPS at over 2200 °C, whose stress-strain behavior remains linear at high temperatures. (5) Research into monolithic lanthanum hexaboride, an excellent thermionic emitter with low electron work function and high chemical resistance. (6) Synthesis of a high-entropy ternary carbide (Ta, Zr, Nb) with peak flexural strength at 1600 °C and multiphase high-entropy (Ti, Ta, Hf, Zr)B2 self-reinforced deformation-resistant ceramic. (7) Flash-SPS of yttria-stabilized zirconia and silicon carbide. (8) Nanoexplosion synthesis of ceramic nanopowders and nano-engineering of zirconia-noble metals composites. (9) Synthesis of iron oxide nanoparticles with varying morphologies and the magnetic properties of magnetite-chitosan nanostructures. (10) Creation of tough yttria-stabilized zirconia nanoceramics through low-temperature SPS, achieving impressive toughness in tetragonal zirconia and zirconia/alumina nanoceramics.

出版物2004年以降のNIMS所属における研究成果や出版物を表示しています。

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    所属学会

    日本セラミックス協会

    電子・光機能材料研究センター
    タイトル

    Deformation-resistant multipurpose ultra-hight temperature ceramics

    キーワード

    Ceramic engineering, Deformation-resistance, Ultra-high elevated temperature strength, UHTC, High-entropy boride and carbide ceramics

    概要

    We are currently conducting research in the chemical structural engineering of deformation-resistant UHTC carbides, borides, nitrides, and composites with ultra-hardness and ultra-high strength. We have combined the merits of powder synthesis and electric current activated sintering technique for the design of techniques applied on powder body with establishing morpho-structural and compositional features, which lead to the fabrication of bulk ceramics with superior characteristics.

    新規性・独創性

    multipurpose deformation-resistant UHTC carbides, borides, nitrides and composites
    sufficient balance between ultra-high hardness, ultra-strength, toughness and modulus
    morpho-structural and compositional features with superior characteristics.
    gas turbine operation in a combined cycle power plants

    内容

    image

    Deformation-resistant UHTC high-entropy ceramics and composites becoming extremely attractive. Light, ultra-hard bulk B4C-based composites with hierarchical superstructure with deformation resistivity from RT to 2000°C (Fig. 1(a)) exhibit change in the deformation mechanism from brittle fracture to plastic deformation, and flexural strength far exceeding 1000MPa at 1800 - 2000°C (Fig. 1(b, c)). Depending on the loading rate, B4C-based ceramic showed 1000 - 8400MPa strength at 2000°C (Fig. 1(b)). Bulk ultrastrong TiB2-B4C ceramic exhibits a mean flexural strength of 1000MPa up to 1800°C, and further increasing to 1760MPa at 2000°C. Recently produced bulk, ultrahard, tough, deformation-resistant Ta diboride, Ta monoboride, Zr-Ta multiboride, and high-entropy TaB2-ZrB2-TiB2-HfB2.

    まとめ

    The request for new multipurpose deformation-resistant ultra-high temperature ceramics (UHTC), able to act as special engine and vehicle protection, ceramic segmented leading edge components for aerospace, plasma-facing, ceramic parts for solar towers used for gas turbine operation in a combined cycle power plants (grids, superheaters, reheaters, evaporators, steam turbines, condensers, and chimneys) cause the worldwide demand in a new class of ceramic composites of incredible high strength, the sufficient balance between high toughness, hardness, and high-modulus.

    この機能は所内限定です。
    この機能は所内限定です。

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