High-entropy compounds are compounds that contain at least five different elements. Among these compounds are carbide and carbonitride synthesized from titanium, zirconium, niobium, hafnium and tantalum by the scientists from Skoltech and Tomsk Polytechnic University. The scientists believe that the mechanical properties and temperature stability of carbide make it one of the most suitable materials for the manufacturing of ultra-high-temperature ceramic elements. However, carbide synthesis is very labor-intensive: it usually requires the raw materials to undergo careful preparation and takes a long time under ultra-high temperatures (about 2,200–2,300 °C).
At the first stage of the study, the scientists modeled various structures of carbonitrides with different concentrations of nitrogen and carbon, also studying their thermodynamic stability at different temperatures. The authors concluded that a large amount of nitrogen can cause mechanical damage to the lattice structure of the material, negatively impacting its stability. The scientists proceeded to obtain carbide and carbonitride using the plasmadynamic synthesis method, in which a high-speed jet of arc discharge plasma is used as a medium for plasma-chemical synthesis reactions.
“Our paper describes the use of a unique research device: a coaxial magnetoplasma accelerator. During a pulse time of less than 1 millisecond, a high-speed plasma jet is formed, reaching the temperature, pressure and crystallization rate required for obtaining unique nanomaterials. Jointly with our colleagues from Skoltech, we used computer design methods in order to combine Ti, Zr, Nb, Hf, Ta, C and N into a single structure in the course of an experiment,” Dmitry Nikitin, candidate of technical sciences, is quoted as saying by Skoltech.
The study showed that the plasmadynamic synthesis method does not require raw materials to undergo special preparation and is versatile, enabling the synthesis of a wide variety of material classes: carbides, nitrides, oxides, carbon nanostructures and derivative composites. This method makes it possible not only to obtain high-entropy carbide, but also to dose nitrogen into its crystal lattice, synthesizing structures close to carbonitride.
