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The demand for new UHTC is rising, particularly for those that are multipurpose, deformation-resistant, and offer specialized protection for engines and vehicles.
Zr-Ta multiboride with artificially created repetitive hierarchical superstructure was formed 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 28GPa at 98N and 22GPa at 196N and the flexural strength of 400MPa up to 2000 °C. A multiphase high-entropy (Ti, Ta, Hf, Zr)B2 at the microscale was defined as a composite where grains of a Ta-rich/Ti-poor complex diboride phase act as reinforcement and grains of Ta-poor/Ti-rich complex diboride are the matrix. At the nanoscale, the grains were heterogeneous, composed of regions with a multitude of complex diboride compositions. A strengthening process is active, increasing the room temperature bending strength (326 MPa) by 50 % at 1800 °C (488 MPa). A ductile behavior with a deformation strain of 7.5 % is observed at 2000 °C, while bending strength (407 MPa) is 25 % above the value at room temperature. The peculiar heterogeneity of this material at nano and micro scales was considered the reason for the remarkable mechanical response to bending load at different temperatures.

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Keyword: DRC, UHTC, Transition-metal carbides, Transition-metal borides

Conference: The 38th Fall Meeting The Ceramic Society of Japan (2025-09-17 - 2025-09-19)

Funding:

• NIMS AB3080
• JSPS KCB101 (JSPS KAKENHI Grants-in-Aid for Scientific Research 24K08035)

Manuscript type: Not a journal article

MDR DOI: https://doi.org/10.48505/nims.6227

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Updated at: 2026-03-21 08:30:22 +0900

Published on MDR: 2026-03-20 21:43:09 +0900