National Research Tomsk State University, Tomsk, Russia:

I. V. Amelichkin, Junior Researcher
P. S. Shcherbakov, Junior Researcher, e-mail: xcrbgc@gmail.com
O. V. Nefedova, Postgraduate Student
V. S. Soloviev, Engineer

Zirconium and hafnium diborides were synthesized. The process of obtaining zirconium and hafnium diborides was carried out by reduction of zirconium and hafnium dioxides with amorphous boron at high temperature in a vacuum furnace with a residual pressure of 10 Pa. The synthesis of metal diborides included the following stages: preparation of charge, pressing, annealing of tablets, milling, and classification. The initial components were mixed in a drum-type apparatus; an aqueous solution of polyvinyl alcohol was used as a plasticizer. Tableting was performed on an OYSTAR Manesty FlexiTab tablet press with a punch diameter of 13 mm at a pressure of 218.7 MPa. The thickness of the obtained tablets was 3 mm. The obtained tablets were annealed in a Nabertherm VHT/GR vacuum furnace. A graphite crucible with zirconium oxide or hafnium oxide backfill, respectively, was used for annealing. The furnace was vacuumized with a forevacuum pump to a residual pressure of 10 Pa. The morphology of ZrB2 and HfB₂ particles was investigated using the QUANTA 200 3D electron and focused-beam system. The phase composition and structural parameters of the samples were investigated on a Shimadzu XRD-6000 diffractometer with Cu K_α radiation. We determined the optimal parameters for the synthesis of zirconia and hafnium diborides: the optimal temperature for the synthesis of zirconia diboride was 1800 ^оС, for the synthesis of hafnium diboride — 1850 ^оС, the heating rate was 8.5 ^оС/min. The highest yield of zirconium and hafnium diborides was achieved in samples with a molar ratio of MeO₂:B = = 1:6 at a synthesis time of 60 minutes. The yield of metal diborides was 99%.
The authors who contributed to this paper include V. I. Sachkov, R. A. Nefedov, R. O. Medvedev, A. S. Sachkova, D. A. Biryukov.
The authors would like to thank the Tomsk Regional Centre of Shared Knowledge for their support of this research work. This research was funded by the Ministry of Education and Science of the Russian Federation under the Governmental Assignment no. FSWM-2020-0028.

1. Samsonov G. V., Markovskiy L. Ya., Zhigach A. F. et al. Boron, boron compounds and alloys. Kiev : AN USSR, 1960. 299 p.
2. Samsonov G. V., Kislyi P. S. Protection tubes for thermocouples designed for continuous temperature monitoring of molten metals and alloys. Ogneupory. 1965. No. 4. pp. 28–32.
3.Kocho V. S., Samsonov G. V., Strelchenko A. G. et al. Continuous temperature monitoring of molten steel in an open-hearth furnace during the refining period. Kiev : Tekhnika, 1965. 227 p.
4. Glaser F. W. Cemented Zirconium Boride Material having a protective Chromium Containing Coating. Journal of the American Ceramic Society. 1960. Vol. 43, No. 9. p. 212.
5. Properties of metallic powders, high-melting compounds and sintered materials. Ed. by Zh. E. Kvyatkovskaya. Kiev : Naukova dumka, 1978. 184 p.
6. Alekseev A. G. et al. High-melting compounds: Properties, production and application. Ed. by T. Ya. Kosolapov. Moscow : Metallurgiya, 1986. 927 p.
7. Khrapov D. A. Burnable poison in a thorium reactor. Important Problems of Today’s Science: Conference proceedings. 10 March 2017, Novosibirsk. Novosibirsk : OOO “Tsentr razvitiya nauchnogo sotrudnichestva”, 2017. pp. 106–114.
8. Ploetz G. L. Ceramic materials for nuclear reactor controls and poison. American Ceramic Society Bulletin. 1960. Vol. 39, No. 7. pp. 362–365.
9. Farhadizadeh A., Vlcek J., Houška J., Haviar S., Cerstvý R. et al. Hard and electrically conductive multicomponent diboride-based films with high thermal stability. Ceramics International. 2022. Vol. 48, Iss. 1. pp. 540–547.
10. Azzali N., Meucci M., di Rosa D., Mercatelli L., Silvestroni L. et al. Spectral emittance of ceramics for high temperature solar receivers. Solar Energy. 2021. Vol. 222. pp. 74–83.
11. Nisar A., Balani K. Phase and microstructural correlation of spark plasma sintered HfB₂ – ZrB₂ based ultra-high temperature ceramic composites. Coatings. 2017. Vol. 7, Iss. 8. DOI: 10.3390/coatings 7080110.
12. Zhang M., Yang G., Zhang L., Zhang Y., Yin, J. et al. Application of ZrB2 thin film as a low emissivity film at high temperature. Applied Surface Science. 2020. Vol. 527. 146763.