Synthesis of (V,Cr)(C,N) nanopowders via carbothermal reduction nitridation method: Influence factors and morphology evolution

Abstract

(V,Cr)(C,N) nanopowders, in the form of globular-like with an average grain diameter of about 60nm, were successfully synthesized via carbothermal reduction nitridation (CRN) of the precursor of ammonium vanadate (NH4VO3), ammonium dichromate ((NH4)2CrO4) and nano carbon black. The influence factors, including synthesis temperature, isothermal holding time and nitrogen pressure, were studied through X-ray diffraction (XRD), and the morphology evolution was investigated by a scanning electron microscope (SEM). The results show that the phase evolution follows: amorphous→VO2→V3O5+V2O3+Cr2O3→V2O3+Cr2O3+(V,Cr)(C,N)→(V,Cr)(C,N) with temperature increases. Long isothermal holding time is beneficial to the dissolution of Cr atom into (V,Cr)(C,N), but it leads to grain growth and nitrogen content reduction of the product. On the contrary, high nitrogen pressure contributes to grain refinement and nitrogen increment of (V,Cr)(C,N). In addition, synthesis temperature has a significant effect on the morphology evolution of (V,Cr)(C,N) nanopowders. The microstructure and chemical composition of the product were also studied.