In order to make clear the generation mechanism of ultrafine metal particles by “hydrogen plasma-metal” reaction (new method to produce ultrafine metal particles), a study has been made of the measurement of generation rate of particles from 16 metals such as Ag, Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pd, Sc, Si, Ta, Ti, V and W by arc melting of these metals in the 50%H₂-50%Ar atmosphere at 0.1 MPa pressure.
It was found that the generation rate of above metals decreases in the following order: Mn, Ag, Al, Sc, Cr, Si, Pd, Fe, Cu, Ti, Ni, V, Mo, Ta and W. The driving force for the generation of particles from metals is much concerned with factors of the heat of vaporization of metals, the heat of formation for recombination from atom (dissolved in metal) to molecule (evolved into gas phase) of hydrogen and the melting point of metals.