Room-temperature synthesis of tungsten silicide powders using various initial systems

The present study investigated the synthesis of tungsten silicide powders using ternary (WO ₃ -Si-Mg and W-SiO ₂ -Mg) and binary (W-Si) initial systems at room temperature via mechanochemical synthesis (MCS) and mechanical alloying (MA) processes. Milling time was used as a process parameter. Subsequently, undesired Mg-based phases were leached out using aqueous HCl solution. Compositional analyses of powders were conducted by using an X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FTIR). Microstructural observations of powders were performed by utilizing particle size analyzer (PSA), scanning (SEM) and transmission electron microscopes (TEM). Also, differential scanning calorimetry (DSC) analyses were carried out for the synthesized powders. While the reaction for tungsten silicide formation took place by MCS in WO ₃ -Si-Mg system after 1 min and by MA in W-Si system after 15 h, it did not occur in W-SiO ₂ -Mg system even after 15 h milling. WSi ₂ , W ₅ Si ₃ and W phases were found in WO ₃ -Si-Mg system whereas only WSi ₂ formed in W-Si system. The ternary WO ₃ -Si-Mg system resulted in SiO ₂ coated nanoparticles owning a mean size of 203 nm. WSi ₂ submicron particles with an average size of 688 nm were obtained in binary W-Si system. The experimental results showed a good consistency with the reaction mechanisms predicted by FactSage™ thermodynamic calculations.