Reaction synthesis and characterization of a new class high entropy carbide (NbTaMoW)C.

A new class of high entropy carbide (NbTaMoW)C was fabricated by reaction synthesis at temperatures as low as 1800 °C using metal powders and graphite as raw materials. Phase formation, compositional uniformity, and microstructure of the (NbTaMoW)C were investigated. The experimental results showed that partial solid solution phase was formed when sample sintered at 1600 °C, according to XRD peak fitting and deconvolution. The as-prepared (NbTaMoW)C with relative density of 97.3% possessed a single-phase rock-salt crystal structure, in which the four metal elements are randomly distributed on the cation sublattice while C occupies the anion sublattice. It was further revealed that (NbTaMoW)C had a high compositional uniformity and the average grain size is 9 ± 0.5 μm. By taking the advantage of these characteristics, the microhardness of (NbTaMoW)C was significantly improved as compared with the base monocarbides. The increase in hardness was attributed to the solid solution strength mechanism. Meanwhile, (NbTaMoW)C exhibited high flexural strength and a relatively low thermal conductivity of 3.19 ± 0.04 mm2/s at room temperature. With temperature increasing, the thermal conductivity of (NbTaMoW)C increases over the entire temperature range from 25 to 1000 °C. [ABSTRACT FROM AUTHOR]