PURPOSE: To produce a conductive silver alloy powder with Ag concentrated on the grain surface by melting a raw powder having specified contents of Ag, Cu, Fe, Co, Ni, etc., in a high-temp. plasma gas, then quenching and solidifying the molten metal.
CONSTITUTION: A raw powder expressed by AgxM1-x (M is ≥ kind among Cu, Fe, Co and Ni, X is an atomic ratio, and 0.001 6 X g 0.4) is injected into a high-temp. and high-speed plasma gas. The average grain diameter of the raw powder is preferably controlled to about 1-300μm and the oxygen content to < about 10wt.%. A gas such as Ar is introduced between the electrodes of copper, etc., a DC arc discharge at ≥ about 20kW is generated to produce the plasma, and the temp. is adjusted to ≥about 1500°C and the flow velocity to ≥about 500m/sec. The raw powder is melted in the plasma, injected from the nozzles of both electrodes quenched and solidified by the ambient gas. In this case, the high-m.p. metal in the molten metal is firstly solidified at the center, and finally silver is solidified at the periphery.
KATSUMATA TSUTOMU
YAMASHITA KUNIHIKO
