Preparation of ultrafine ceramics powders by hydrogen, nitrogen and oxygen plasmas

Abstract

Ultrafine powders (below 0.1μm) of nitrides (TiN, ZrN) oxides (MgO, Al₂O₃, WO₃, Nb₂O₅, MoO₃) and carbides (WC, SiC, TiC) were directely obtained from massive molten metals or ceramics by using an arc melting technique in an atmosphere of nitrogen or hydrogen or oxygen at 0.1MPa pressure.
The apparatus for producing ultrafine ceramics powders is basically an arc melting apparatus, which consists of an arc melting chamber with six electrodes, ultrafine powder collecting part (filter paper collection type), gas supply and circulation system, and power source of electric welding.
The sizes, figures and chemical composition and crystal structures obtained were determined by electron microscorpe, X-ray diffraction and chemical analysis.
It is estimated that ultrafine ceramics powders were formed by mutual reactions between plasma gas (hydrogen, nitrogen and oxygen atom) and evaporated materials where a kind of enhanced evaporation to be caused by evolution phenomenon of super-saturated gas from molten massive material takes place.