Evaporation of zirconia powders in a thermal radio-frequency plasma

Incomplete evaporation of high-melting solid precursors, such as zirconia (ZrO2), is a major problem in the application of plasma-flash evaporation processes to powder synthesis and production of high performance coatings. The evaporation of zirconia powders injected into a thermal radio-frequency (RF) plasma is investigated by using optical emission spectroscopy (OES) and laser Doppler anemometry (LDA) to study evaporation rates and particle velocities. Model calculations are compared with the results of the process diagnostics. Axial emission profiles confirm the influence of the particle size on the evaporation behavior. Line-integrated side-on emission profiles are used to assess the rate of evaporation.