Preparation of Ultrafine Powders of Metals and Ceramics by Chemically Reactive Gaseous Plasmas

Abstract

A new process for the preparation of ultrafine powders of metals and ceramics was developed by the authors from a technique of arc melting of metals in an atmosphere of hydrogen, nitrogen, or oxygen at 0.1M Pa pressure.
An arc, in gases such as hydrogen, nitrogen, oxygen, is a kind of reactive thermal plasma, which plays an important role for the formation of ultrafine particles from massive molten materials. That is, an enhanced evaporation phenomenon is induced by the dissolution-evolution reaction of plasma gas on materials, and ultrafine powders are formed.
This paper describes the formation mechanism, formation rate, size, crystal structure and some properties of ultrafine powders obtained by this new process, such as the metals Ag, Al, Sc, Cr, Si, Pd, Fe, Cu, Ti, Ni, V, Mo, Ta, W and the ceramics CaO, MgO, Al₂O₃, TiO₂, ZrO₂, WO₃, MoO₃, Nb₂O₅, TiN, ZrN, Al+AIN, SiC, TiC, WC,