Generation and behavior of fine particles in thermal plasmas: a review

The generation and processing of fine powders in thermal plasma has attracted increasing interest over the past years, precipitated by a growing awareness that conservation of materials is no longer an option but rather a necessity. Plasmaspheroidization, densification, fuming, metallurgical reduction, and the production of refractory oxides, carbides, nitrides, and borides in thermal plasmas are fast developing technologies which, in some cases, have already reached industrial production scale. In this survey, pertinent literature (198 references) will be reviewed with emphasis on basic studies in this field, reported over the past 20 years. The first part of this review covers powder handling, quenching characteristics, nucleation and growth, and modeling of plasma-particle interactions. The second part is concerned with plasma furnaces for the production of fine particles, including RF induction plasmas, DC anode furnaces, DC plasma jets, DC transferred arcs, cathode pump fed arcs, hybrid induction-DC plasmas, and three-phase AC furnaces.