Phase evolution during synthesis of vanadium carbide (V8C7) nanopowders by thermal processing of the precursor

The phase and structure evolution during synthesis of vanadium carbide (V8C7) nanopowders by thermal processing of the precursor were investigated using X-ray diffraction (XRD). The morphology of the reactant was characterized by transmission electron microscopy (TEM). Simultaneous thermogravimetric and differential thermal analysis (TG-DTA) were made on the precursor. The results indicate phase evolution sequences are NH4VO3 -> V2O5 -> VO2 -> V5O9 -> V4O7 -> V2O3 -> VC1-X -> V8C7. The single phase V8C7 powders can be prepared at similar to 1100 degrees C for 1h, and the powders show good dispersion and are mainly composed of uniformly sized spherical particles with the majority diameters of 20-50 nm. (C) 2007 Elsevier Ltd. All rights reserved.