Microstructural characterization and densification of W-1 wt% La2O3 composite powders synthesized by ultrasonic spray pyrolysis

An optimum route to fabricate the dense W-base composite with homogenous dispersion of nano-sized La2O3 particles and increased mechanical property is investigated. Two methods for developing a uniform dispersion of 1 wt% La2O3 particle in W were compared on the basis of the resulting microstructures and Vickers hardness. The composite powder prepared by direct ultrasonic spray pyrolysis showed a finer particle size than that by ultrasonic spray pyrolysis combined with a La-nitrate polymeric additive route. TEM and XPS analysis revealed that the size and location of dispersed particles in the composite powder and the residual oxide depend on the synthesis process. The densified specimen by spark plasma sintering using the synthesized powder by ultrasonic spray pyrolysis combined with a polymeric additive route showed increased relative density and fine particle size. This sintered specimen at 1700 °C exhibited a relative density of 98.0%, a grain size of 5.32 μm, and the highest Vickers hardness value of 4.5 GPa. These results indicate that the wet chemical method combined with spray pyrolysis and polymer solution is a promising way to synthesize the W-based composites with homogeneous dispersion of fine oxide particles and enhanced mechanical properties.