Jianming Ruan

Synthesis and characterization of WC-Co nanosized composite powders with in situ carbon and gas carbon sources

This study presented nanosized WC-Co composite powders synthesized using a one-step reduction-carbonization process with a combination of CH4/H2 as a gas carbon source and soluble starch as an in situ carbon source. The results of carbon analysis and X-ray diffraction revealed that WC-Co nanocomposite powders with a pure WC and Co phase could be obtained at 1100 °C after 0.5 h. A higher gas flow ratio of CH4/H2 during the reduction-carbonization process led to a higher total carbon content of the sample. A field emission scanning electron microscope confirmed that the particles in the WC-6 wt% Co composite powders had the lowest average size of 43 nm with equiaxed shapes. A sintering neck was observed in the WC-3 wt% Co composite powders whereas faceted particles were found in the WC-12 wt% Co composite powders. Moreover, this method has advantages of simple processing, rapid synthesis and good applicability in potential industry application.

Analysis on Calcination Process of WC–Co Precursor Powder

In this paper, calcination of WC–Co precursor powders with different Co contents prepared by solution technique was investigated. Thermal analysis was carried out. The precursor powders after calcination process were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). A mechanism of calcination of the precursor powder was proposed and substantiated by the experimental data. The mechanism was that carbon in Sample C (WC–3 wt.% Co) after calcination was provided only by the pyrolysis of soluble starch, while carbon in Sample A (WC–12 wt.% Co) was provided not only by the pyrolysis of soluble starch but also by the pyrolysis of methyl in acetate cobalt. The main phase after calcination was the mixture of WO3, CoO, and C. Moreover, ultrafine WC–Co composite powder was obtained after fast reduction–carbonization treatment. The morphology of WC–Co powder is hollow spherical granular structure where individual particles are cemented in the form of agglomerated ball and the mean particle size is 177 nm.