High-entropy alloys and compounds are becoming an important class of new materials due to their outstanding refractory and high-temperature properties. However, preparation in bulk quantities and in powder form via classical metallurgical methods is challenging. Here, we report the first synthesis of an ultra-high-temperature high-entropy carbide, (TiNbTaZrHf)C, via a facile electrochemical process. In this, a mixture of the individual metal oxides and graphite is deoxidised in a melt of CaCl 2 at a temperature of only 1173 K. The (TiNbTaZrHf)C prepared is single-phase fcc and has a powdery morphology with a particle-size range of 15-80 nm. Such materials are in demand for modern additive manufacturing techniques, while preliminary tests have also indicated a possible application in supercapacitors. The successful synthesis of (TiNbTaZrHf)C powder may now guide the way towards establishing the electrochemical route for the preparation of many other entropy-stabilised materials. Entropy-stabilised materials are presently gaining considerable attention. Yeh et al. [1] and Cantor et al. [2] incepted the fundamental concept of entropy stabilisation in 2004 by preparing equiatomic multi-component alloys with a singlephase crystal structure. It was soon realised that the combination of complex chemistry and simple crystallography, together with the large compositional design space, would provide fundamentally new alloys with exceptional mechanical and thermal as well as oxidation-and corrosion-resistant properties. [3-5] In the last five years, the concept of entropy stabilisation has been extended further towards high-entropy oxides, borides, nitrides, and carbides. [6-13] The borides, nitrides, and carbides of Group-IV and-V transition metals, known as ultra-high-temperature ceramics (UHTCs), have long been of interest because their properties often exceed those of the corresponding metals. [14, 15] Bulk quantities of UHTCs are conventionally prepared by hightemperature reactions, posing problems in achieving high purity, homogeneous chemical and phase compositions, and controlled particle size, especially at the nanoscale. Likewise, high-entropy carbides (HECs) are prepared by mechanical milling and subsequent spark-plasma sintering or by carbothermal reduction, both at temperatures around 2273 K, yielding either almost dense bodies or coarse micron-sized powders. [9-13] Consequently, major research efforts are underway worldwide with the aim of making high-entropy materials in bulk quantities and in nanopowder form. The present study introduces a novel, facile, and singlestep method for the synthesis of HECs by harnessing the FFC-Cambridge electro-deoxidation process. [16] This process was originally developed for the preparation of metals directly from their oxides. It relies on making the metal oxide the cathode in a melt of CaCl 2 electrolyte and polarising it vs. a carbon anode such that the oxide ions from the cathode are expelled into the electrolyte. The versatility of the FFC process has been highlighted in...
