Quantification of Alumina Evaporation by Thermal Plasma

When using powder particles in thermal plasma processes, partial evaporation of the particles may occur during the plasma-particle interaction. This research proposed the study of the parameters that cause evaporation with the aid of an experimental setup for the validation of an analytical model. To quantify evaporation, two experiments were carried out: the first one involved deposition of a coating on a substrate, and the second one without deposition. The model showed differences in evaporation when the interaction of the particles with the photons emitted by the plasma is considered. The particle radius size can influence the photon absorption efficiency and the electron emission current from the particle surface during the process. This can cause an increase in the final evaporation rate. In this research, evaporation was obtained as a function of the injected plasma mass considering the different particle size distributions. The experiments showed significant evaporation during thermal plasma processing of alumina powder, but evaporation reduced for higher feed rates.