Diagnostics and Modelling of a Thermal RF Plasma Process Used for the Flash Evaporation of Zirconia Powders

The evaporation process of zirconia powders injected in a thermal RF plasma is investigated. Both model calculations and experimental techniques such as Optical Emission Spectroscopy (OES) and Laser Doppler Anemometry (LDA) are used to study the evaporation behaviour. Gas temperatures and velocity distributions are determined numerically from conservation laws and Maxwell equations. The influence of plasma and particle parameters on the thermal interaction of injected particles is discussed. Asymmetric Abel inversion is applied to detect asymmetric emission profiles in the plasma source. Spectroscopic measurements reveal that evaporated zirconia is concentrated near the axis of the plasma. Numerical calculations show that line-integrated emission profiles can be used to distinguish the cases of complete and incomplete evaporation. LDA measurements of the particle velocity distribution show good agreement with the results achieved with modelling.