Particulate Science and Technology, Vol.33, No.6, 587-592, 2015
Effect of Extended Milling of Scheelite Ore with Activated Charcoal on Direct Synthesis of Nanotungsten Carbide
Nanosized tungsten carbide is mostly synthesized from pure precursor(s) like W, WO3, W(CO)(6), WCl4, and WCl6 which makes its production costly. These pure precursor(s) are obtained after lengthy, multistage processing of the ores, mainly scheelite (CaWO4) and Wolframite (FeWO4). This paper investigates the effect of extended milling of 150h of scheelite ore with activated charcoal for direct synthesis of nanosized tungsten carbide. The reaction mechanism was studied with the help of thermodynamic analysis. The investigations revealed that reaction of CaWO4 with carbon at 1032 degrees C will lead to the formation of WC phase without creation of any undesired phases like WO2.72, WO2, W2C, or W. To remove impurities and unwanted reaction products, the calcined powders were leached by dilute acid (1:1 HCl) followed by base (0.25M NaOH) treatment. The final leached powders contained 5 to 30nm size WC particles and little amount of unreacted scheelite particles.
Keywords:ceramics;electron microscope;nanoparticles;particle size distribution;scheelite;Tungsten carbide