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.