Production of ultrafine nickel particles using an insulated constrictor plasma torch

Ultrafine nickel particles (UFPs) were produced using an Ar-Hz plasma jet g enerated by an insulated constrictor plasma torch, and the effects of plasm a gas flow rate and hydrogen content on the proportion of UFPs produced wer e investigated. Since hydrogen supply from the cathode causes erosion of a copper anode, two different methods were proposed to prevent erosion of the anode: use of an anode with a tungsten pipe insert in the nozzle and suppl y of hydrogen from a feed ring installed under the anode. The proportion of UFPs produced decreased with increasing plasma gas flow r ate. This decrease is due to the reduction in residence time of powders pre sent in the plasma. The proportion of UFPs produced increased with increasi ng hydrogen content. This is because the recombination energy of dissociati on and ionization were added to the plasma. However for a relatively high h ydrogen content, the proportion of UFPs saturated or decreased because a me lt drop adhesion occurred in the nozzle. Further examination to find more e ffective powder heating methods and to prevent the melt drop adhesion is re quired in order to increase the proportion of UFPs.