A Novel Approach to the Rapid in situ Synthesis of Tungsten Carbide Nanopowder by Plasma Milling and Carbothermal Reduction

This work prepares nanocrystalline tungsten carbide (WC) powder using conventional ball milling or plasma milling (P-milling) to process tungsten trioxide (WO 3 )–carbon (C) mixtures, with subsequent carbothermal reduction. The aim is to assess the effects of a discharge plasma on the microstructure of these materials. The results indicates that WC powders with particle sizes of less than 100 nm could be fabricated through heating at a relatively low temperature of 1150 °C for 1 h under vacuum after P-milling. This process is found to allow a lower processing temperature and provided more complete carburization in comparison with conventional ball milling. P-milling is determined to produce more loosely adhering WO 3 nanoparticles and a higher surface area, resulting in more reactive sites and a larger contact area between WO 3 nanoparticles and C atoms. This technique simultaneously generates more oxygen vacancies and defects on the surfaces of the WO 3 and C, respectively, based on the use of a plasma discharge. It is evident that this new technology permits nanocrystalline WC to be readily obtained from WO 3 and C in a reduced time span and at a lower cost and greater efficiency. This technique could also be used to fabricate WC nanopowders on an industrial scale.