A group of researchers from Skoltech, Tomsk Polytechnic University, and other academic organizations in Russia and China used the method of plasma dynamic synthesis to obtain a high-entropy carbide — a compound of titanium, zirconium, niobium, hafnium, tantalum with carbon — and carbonitride — a solid solution formed by carbides and nitrides of the transition metals — in the form of nanopowders. The new technology provides a simple and universal way to produce high-entropy materials that are used in protective coatings, nuclear power, lithium-ion batteries, catalysts, and microelectronics. The results are published in the Journal of Alloys and Compounds.

The composition of high-entropy compounds includes four or more different elements — in this case, metals and carbon. In the paper, scientists used a new technology and synthesized carbide from titanium, zirconium, niobium, hafnium, and tantalum (TiZrNbHfTaС5), as well as carbonitride from these components. The authors point out that the substance is one of the most suitable materials for manufacturing ultra-high-temperature ceramic elements due to its high mechanical properties and temperature stability. However, the synthesis of carbide is difficult: It requires careful preparation of the feedstock, and it is carried out at ultrahigh temperatures — about 2200-2300°C — for a long time.

“Multicomponent and high-entropy materials have been studied since recent times. We modeled various structures of carbonitrides with different concentrations of nitrogen and carbon and studied thermodynamic stability at different temperatures. We found out that a large amount of nitrogen can lead to strong mechanical stresses of the lattice, which will negatively affect the stability of the material,” said the study supervisor, Professor Alexander Kvashnin from the Skoltech Energy Transition Center.

To synthesize carbide and carbonitride, the research group used the method of plasma dynamic synthesis. It uses a high-speed plasma jet of an arc discharge as a medium for high-energy plasma chemical synthesis reactions. The arc discharge and the subsequent plasma flow are generated using a coaxial magnetoplasma accelerator.

“In this paper, we focus on using a unique scientific installation — a coaxial magnetoplasma accelerator. In less than a millisecond, a high-speed plasma jet is created, which allows for the increased temperature, pressure, and crystallization rate necessary to create unique nanomaterials. Together with colleagues from Skoltech, based on the methods of computer-aided material design, we managed to experimentally combine Ti, Zr, Nb, Hf, Ta, C and N into a single structure. The method does not require special preparations of raw materials. Characterized by low energy consumption, it is universal, providing synthesis of a wide variety of classes of materials: carbides, nitrides, oxides, carbon nanostructures and composites based on them,” commented the lead author of the study, Associate Professor at TPU Dmitry Nikitin.

The use of the plasma dynamic method for the synthesis of high-entropy carbides and carbonitrides leads to the production of high-quality monophase powders. This method not only enables efficient production of pure high-entropy carbide TiZrNbHfTaС5 in a dispersed monocrystalline form, but also ensures the introduction of nitrogen into the crystal lattice, thereby synthesizing structures close to carbonitride. By using a carbon-free mixture of precursors in a nitrogen-containing gas atmosphere, it is possible to obtain materials containing up to 8 wt% nitrogen.