Room-Temperature Synthesis Of Tungsten Silicide Powders Using Various Initial Systems

Abstract

The present study investigated the synthesis of tungsten silicide powders using ternary (WO3-Si-Mg and W-SiO2 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 WO3-Si-Mg system after 1 min and by MA in W-Si system after 15 h, it did not occur in W-SiO2-Mg system even after 15 h milling. WSi2, W5Si3 and W phases were found in WO3-Si-Mg system whereas only WSi2 formed in W-Si system. The ternary WO3-Si-Mg system resulted in SiO2 coated nanoparticles owning a mean size of 203 nm. WSi2 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.