Researchers at MISIS University have introduced new materials called hafnium-zirconium carbonitrides. These materials can be used as components of matrix nuclear fuel or thermal protection for spacecraft. The chief advantage of these materials over their carbide predecessors lies in their increased resistance to high-temperature oxidation. The service life of the product and the upper limit of working temperatures hinge on this property.
Zirconium and hafnium carbides are considered promising candidates for various high-temperature applications. Their melting point exceeds 3500°C, and they possess high thermal conductivity, impact toughness, and strength. However, these compounds have relatively low oxidation stability at high temperatures.
To address this issue, researchers at MISIS University proposed adding nitrogen to the structure of carbides. Under conditions of high temperatures (above 1200°C), the oxidative resistance of the materials significantly increased because dense oxide layers formed, acting as a barrier to prevent oxygen diffusion.
“There is an opinion that adding nitrogen, for example, to carbide will inevitably worsen its oxidation resistance due to the formation of many gaseous reaction products. However, in our work, we refute this and show that nitrogen alloying can significantly increase oxidative resistance. In transition metal carbonitrides, the formation of stronger covalent bonds increases thermal stability, reduces the number of stable oxygen adsorption sites, and slows down oxygen diffusion due to the compound’s chemical complexity Thanks to all these factors, carbonitrides have higher oxidation resistance compared to ’competitors’, carbides,” Veronika Suvorova, Ph.D. (Engin.), a researcher at the Research Center Ceramic Constructional Materials at NUST MISIS.
In-depth analysis revealed that adding zirconium (Zr) to hafnium carbonitride slows down the oxidation process by two times. It described the detailed results of the study in the journal Ceramics International (Q1).
The increased resistance of these materials to oxidation suggests their potential application for thermal protection of critical components and structures of spacecraft. In further research, scientists will analyze the impact of nitrogen on the radiation resistance of hafnium-zirconium carbides. If the results are positive, these materials could become promising candidates for use as nuclear fuel components, providing an alternative to silicon carbide.
The study aligns with the goals of NUST MISIS’s Materials of the Future strategic project under the Russian Ministry of Science and Higher Education’s Priority 2030 program.