Effects of additives on synthesis of vanadium carbide (V8C7) nanopowders by thermal processing of the precursor

Vanadium carbide (V8C7) nanopowders; can be synthesized by thermal processing of the precursor of ammonium vanadate (NH4VO3) and nanometer carbon black. Effects of additives (CaF2, CeCl3 center dot 7H(2)O and LaCl3 center dot 7H(2)O) on the phase composition and microstructure of the synthesized powders were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that additives (CaF2, CeCl3 center dot 7H(2)O and LaCl3 center dot 7H(2)O) can accelerate the solid state reaction during synthesis of V8C7, and these additives play a vital role in determining the phase composition and microstructure. V8C7 powders with basically single phase can be synthesized at 1100 degrees C for 0.5 h with the addition of additives (CaF2, CeCl3 center dot 7H(2)O and LaCl3 center dot 7H(2)O), and the powders show good dispersion and are mainly composed of uniformly-sized spherical particles with a mean diameter of similar to 50 nm. Further experiment shows that V8C7 powders can be prepared at 950 degrees C for 1 h with 1.0 wt% CaF2 as additive. (C) 2009 Elsevier Ltd. All rights reserved.