No abstract

In situ synthesis method was used to prepare V 8 C 7 -Cr 3 C 2 nanocomposite. Ammonium vanadate, ammonium dichromate and nanometer carbon black were used as raw materials. The products were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric and differential scanning calorimetry (TG-DSC) and X-ray photoelectron spectroscopy (XPS) techniques. The results show that V 8 C 7 -Cr 3 C 2 nanocomposite with an average crystallite size of 25.4 nm can be synthesized at 1200°C for 1 h. The synthesis temperature required by the method is at least 200°C lower than that required by the conventional approaches for preparing vanadium and chromium carbides. The powders show good dispersion and are mainly composed of spherical or nearly spherical particles with a mean diameter of about 30 nm. The weight loss ratio of the precursor throughout the reaction process reaches 58 wt%. Three exothermic peaks and four endothermic peaks occur during the reaction. The surface of the specimen is mainly composed of V, Cr, C and O elements.