Efficient single-step mechanosynthesis route of nanostructured Hf0.2Nb0.2Ta0.2V0.2Zr0.2C0.5N0.5 High Entropy Carbonitride Powder

Abstract

Nowadays high entropy carbides (HECs) are an important group of advanced ceramics. They are composed by at least by five transition metals (TMs) in nearly equiatomic proportion and disordered distributed in the cationic sublattice of face centered cubic structures, with carbon atoms in the octahedral interstitial voids, with general formula (TM1,TM2,TM3,TM4,TM5)C. These HECs belong to the recent novel group of ultra-high temperature ceramics (UHTCs), with superior properties in comparison with the constituent binary carbides. However, the synthesis of those HECs can be modified to develop high entropy carbonitrides, HECNs, where the C are partially substituted by N, to form a solid solution in the anionic sublattice, with expected improved properties as UHTCs, but they are in an incipient state of development. Here, we report the synthesis and deep characterization of a non-previously obtained Hf0.2Nb0.2Ta0.2V0.2Zr0.2C0.5N0.5 HECN, via a facile, single step and reproducible solid- gas reaction mechanosynthesis route. The synthesis was successfully completed in a planetary ball mill device, after 2h of milling time, at 400 rpm and using a ball-to- powder ratio of 60:1 in a pure N2 atmosphere at room temperature. The as-synthesized HECNs powdered showed nanostructured morphology and outstanding high- temperature oxidation resistance up to 1500ºC.