Synthesis of homogeneous WC-Co nanoparticles using carbon-coated WO2.72 precursors

Waste cemented carbides were recovered via the oxidation reduction method to prepare a homogeneous WC-Co powder. The preparation process consists of oxidation, hydrogen reduction, and carbonization. The results show that the performance of the WC-Co composite powder mainly depends on the mild hydrogen reduction and carbon layer. When the milling time is 40 h, the oxide phase of WO3 transforms into WO2.72 in a mild reduction process. The as-synthesized WO2.72 exhibits one-dimensional rods with high aspect ratios and good dispersibility. Subsequently, the core-shell-structured carbon-coated WO2.72 precursors, which were prepared via chemical vapor deposition (CVD) from the decomposition of absolute alcohol, were subjected to reduction and carbonization. The phase transformation laws in the carbothermal reduction process are proposed based on thermodynamic calculations and an XRD analysis. Further, the effects of the reaction temperature and reaction time on the particle size were investigated. An approximately spherical WC-Co powder with a mean particle size of approximately 120 nm is obtained when the reaction temperature and reaction time are 1073 K and 3 h, respectively. The particles represent relative homogeneous and narrow particle size distributions.