Microstructure evolution and formation of needle-like WO3 nanowire during sintering of submicron tungsten particles

In this study, an interesting phenomenon was observed related to sintering of tungsten sub-micron powders in hydrogen atmosphere. Initial tungsten compacts containing 80 wt% micro powder and 20 wt% submicron particles (size of 100-600 nm) were sintered in hydrogen atmosphere. SEM, XRD and EDS analysis were used to studying the micro-structural details. The obtained results exhibited an interesting oxidation-condensation phenomenon in sintered specimens that resulted into formation of needle-like WO3 nanowires on the particle surfaces. Also, submicron particles accelerate the sintering of tungsten powders due to faceted-nonfaceted transformation mechanism. The obtained results proposed that oxygen content in initial powders can be considered as required oxygen source for nucleation and growth of WO3 nano-structure. In this condition, the nanowires extend via solid-phase growth from nanowire nuclei generated on the W particles surface.