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, CeCl₃·7H₂O and LaCl₃·7H₂O) 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, CeCl₃·7H₂O and LaCl₃·7H₂O) 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 °C for 0.5 h with the addition of additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O), and the powders show good dispersion and are mainly composed of uniformly-sized spherical particles with a mean diameter of 50 nm. Further experiment shows that V₈C₇ powders can be prepared at 950 °C for 1 h with 1.0 wt% CaF₂ as additive.