An insulated constrictor plasma torch with an improved anode

Improvements to the anode of an insulated constrictor plasma torch were car ried out in order to increase the proportion of ultrafine particles (UFPs) produced by means of the plasma jet method. Nickel UFPs were produced using the improved anode to examine its effects. The improved anode is a unified type consisting of the electrode and feeding ports for powders and hydroge n. Two types of improved anode with different feeding port positions were m ade, and the effect of the relative position of feeding port to nozzle leng th on the proportion of UFPs produced was examined. In addition, the geomet ry of the nozzle exit was modified in order to prevent melt drop adhesion. The proportion of UFPs produced using the improved anode was greater than t he fraction produced using an unimproved anode. The position of feeding por ts did not greatly affect the proportion of UFPs produced although an appro priate feeding port position relative to the nozzle length may exist which improves the proportion of UFPs produced. The cause of the melt drop adhesi on was found to be the cold hydrogen which was added to the argon plasma. T he melt drop adhesion was formed by cold hydrogen flowing along the inner-w all of the nozzle.