Research On Mechanism Of Vanadium And Chromium Carbide Nanocomposite Synthesized By Microwave And In Situ Methods

Vanadium and chromium carbide have been widely used in cemented carbide, ferrous metallurgy, electronics and other products due to their excellent performance. In this paper,vanadium and chromium carbide nanocomposite were synthesized by microwave and in situ methods. The nano vanadium oxide and nano chromium oxide were used as the vanadium source and chromium source, and nano carbon black, glucose, sucrose were used as the carbon source respectively. And the effects of carbon source content, reaction temperature and holding time on the phase, morphology and thermal properties of the reaction products were studied. It was also discussed that the formation mechanism and phase evolution in the whole reaction process of reaction production, and the influence on microstructure and mechanical properties of nanocomposite carbides of WC-8Co cemented carbide. The products were characterized by XRD, SEM, TEM, XPS and other means. The results show that: vanadium and chromium carbide nanocomposite can be synthesized at 1100℃ for 1h with 30 wt.%C. The as-prepared powders are composed of Cr3C2, V3Cr2C5 and Cr2VC2. The products show good dispersion and are mainly composed of spherical or nearly spherical particles with a mean diameter of about 30 nm. When the carbon source is glucose, the vanadium and chromium carbide nanocomposite can be obtained at 1000℃ for 1h and the glucose concentration was 54 wt.%. The products with nearly spherical or bar shape are composed of V3Cr2C5 and Cr2VC2 with a mean diameter of 100 nm and show the obvious agglomeration. When take the carbon source as sucrose, the vanadium and chromium carbide nanocomposite can be prepared at the condition of 50 wt.% sucrose content at 1000℃ for 1h.The products containing V3Cr2C5 and Cr2VC2 show good distribution and are consisted of nearly spherical or bar particles with the mean diameter of about 100 nm. Using V2O5 as vanadium source to prepare vanadium carbide, it is not directly carbonized into vanadium carbide or vanadium. The theory process of convention is V2O5â†'VO2â†'V2O3â†'VOâ†'VCxâ†'VC. When we use nano vanadium oxide, nano chromium oxide and nano carbon black as raw material to synthesize the vanadium and chromium carbide nanocomposite, the reaction process is more complex with the phase transition of V2O5â†'V2O3â†'VOâ†'VCxOzâ†'Cr2VC2â†'V3Cr2C5, Cr2O3â†'Cr2VC2â†'V3Cr2C5, Cr2O3â†'Cr3C2-xâ†'Cr3C2. The nano carbide compositeprepared by this study can effectively refine the grain size of cemented carbide, optimize the microstructure of cemented carbide, reduce the pore defects and improve the comprehensive properties of cemented carbide.