Spherical submicron-size copper and copper-tungsten powders prepared in RF induction thermal plasma

Spherical submicron copper particles were synthesized through evaporation and subsequent condensation of copper powders in Ar-H₂ thermal plasma. Copper powders of ∼40μm in size injected into the plasma, evaporated instantly and fine particles were formed through homogeneous nucleation and subsequent heterogeneous condensation. Particle size and the distribution in the synthesized powders were changed depending on the powder feed rate. Formation of submicron size spherical powders attributed to a significantly high degree of supersaturation in a vapor phase. Particle sizes of the as-produced powders range from submicron to several tens of micrometers. A simple sedimentation treatment was successfully applied to separate the as-formed powders with alcohol solvent to give uniform spherical submicron-size particles with monomodal size distributions. Cu-W composite powders were synthesized through the Ar-H₂ plasma treatment of Cu-WO₃ composite powders. The starting temperature of shrinkage was made significantly higher than pure Cu powders by mixing with several wt% of W.