Bulk Re₂C: Crystal Structure, Hardness, and Ultra-incompressibility

Abstract

A hard ultra-incompressible bulk Re2C material is first synthesized under moderate pressure (2−6 GPa) and high temperature (873−1873 K). The phase composition of Re2C was determined by a chemical analysis method, and its structure is finally determined to be a ReB2-type structure by means of X-ray diffraction, Raman technology, and ab initio calculations. The hardness measurements show that it is a hard material which can rival ReB2. More impressively, its volume incompressibility is comparable with that of diamond, and its c axis incompressibility even exceeds that of diamond. In the end, the P−T phase diagram of the Re−C system has also been determined in the regions of P = 1−6 GPa and T = 873−1873 K. The moderate synthesis conditions show that this hard ultra-incompressible bulk material will obtain the further applications.