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High-Entropy Borides under Extremes of Pressures and Temperatures

ORAL

Abstract

High entropy borides (HEBs) demonstrate high hardness, thermal stability in oxidizing environment, and phase stability under high pressures. This talk will cover synthesis and characterization studies on several members of this group (Hf0.2, Mo0.2, Nb0.2, Ta0.2, Zr0.2)B2 , (Hf0.2, Mo0.2, Nb0.2, Ta0.2, Ti0.2)B2, and (Hf0.2, Ti0.2, Zr0.2, Ta0.2, Mo0.2)B2. HEBs synthesized under high pressure and high temperature conditions using either boro-thermal or carbo-thermal reduction starting with a mixture of transition metal oxide, boron, carbon and B4C. The AlB2 type hexagonal crystal structure of these HEBs has been studied at HPCAT, APS under high pressure and high temperature conditions utilizing, symmetric DACs, radial DACs, and a large volume Paris-Edinburgh press. Synchrotron XRD data is used to establish EOS, up to 220GPa, and thermal EOS up to 9.5 GPa and 2000°C. The thermal oxidization resistance is measured in a dual thermogravimetric and differential scanning calorimetry analysis (TGA/DSC) stage up to 1300°C. The thermal oxidation resistance of HEBs will be compared with other high temperature ceramics for applications in extreme high-pressure high temperature environments.

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Publication: Iwan, S., Perreault, C., & Vohra, Y. (2022). Synthesis and Ultrahigh Pressure Compression of High-Entropy Boride (Hf0.2, Mo0.2, Nb0.2, Ta0.2, Zr0.2)B2 to 220 GPa. Materials, 16, 158. https://doi.org/10.3390/ma16010158<br>Iwan, S., Burrage, K. C., Storr, B. C., Catledge, S. A., Vohra, Y. K., Hrubiak, R., & Velisavljevic, N. (2021). High-pressure high-temperature synthesis and thermal equation of state of high-entropy transition metal boride. AIP Advances, 11(3), 035107. https://doi.org/10.1063/5.0045592<br>Iwan, S., Lin, C.-M., Perreault, C., Chakrabarty, K., Chen, C.-C., Vohra, Y., Hrubiak, R., Shen, G., & Velisavljevic, N. (2022). High-Entropy Borides under Extreme Environment of Pressures and Temperatures. Materials, 15(9), Article 9. https://doi.org/10.3390/ma15093239<br>Storr, B., Amezaga, C., Moore, L., Iwan, S., Vohra, Y. K., Chen, C.-C., & Catledge, S. A. (2023). High Entropy Borides Synthesized by the Thermal Reduction of Metal Oxides in a Microwave Plasma. Materials, 16(12), Article 12. https://doi.org/10.3390/ma16124475

Presenters

  • Seth Iwan

    University of Alabama at Birmingham

Authors

  • Seth Iwan

    University of Alabama at Birmingham

  • Yogesh K Vohra

    University of Alabama at Birmingham, Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35233, United States, Department of Physics, University of Alabama, Birmingham, AL 35233, United States