Synthesis of chromium carbide nanopowders via a microwave heating method

Chromium carbide nanopowders were firstly synthesized via a simple microwave heating technique using nanometer chromic oxide (Cr₂O₃) and nanometer carbon black as raw materials in argon gas atmosphere. The samples were characterized by X-ray diffractometry (XRD), thermogravimetric and differential scanning calorimetry (TG–DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results show that chromium carbide nanopowders with an average crystallite size of 24 nm can be synthesized at 1000 °C for 1 h. The synthesis temperature required by the method is 400 °C lower than those required by the conventional approaches for preparing chromium carbide. SEM and TEM results show that the powders show good dispersion and are mainly composed of spherical or nearly spherical particles with a mean diameter of about 30 nm. The phase transformation sequence during the heat treatment is: Cr₂O₃ → CrO → Cr₇C₃ → Cr₂C → Cr₃C₂.