Transient heating and evaporation of metallic particles under plasma conditions

Abstract

The synthesis of metallic nanopowders through the vaporization and condensation of metallic precursors under plasma condition is increasingly accepted for a wide range of applications in the electronic and electrical industry. The present study aims at the computer simulation of the basic processes involved. Specific attention is given to the particle evaporation rate and the associated energy balance. Computation carried out for the vaporization of 50 µm iron and copper particles in an atmospheric pressure argon plasma at 9000 K provide means of quantifying the different energy requirements of the process including;• energy needed for the initial heating of the particle to its vaporization temperature,• energy required for particle vaporization,• energy lost by surface radiation from the particle during the evaporation process, and• energy radiated from the plasma/metal vapor cloud.The results show that energy lost by volume radiation for the plasma/metal vapor cloud is by far the most important energy requirement of the process that deserves special attention in terms of reactor engineering design in order to reduce its value and consequently increase process productivity. As expected, the results are to a large extent material dependent, varying widely with the radiative properties of the metal involved.