An Optical Emission Spectroscopy Study of Plasma–Precursor Interactions in Solution Precursor Plasma Spray

Abstract

In this work, optical emission spectroscopy is used to study plasma–liquid precursor interactions in a plasma spray process. A mapping of the plasma jet is performed with a bundle of seven optical fibers while injecting various liquid precursors. The decomposition of two suspensions containing a titania (TiO₂) powder in different solvents and that of one solution containing titanium butoxide is analyzed inside a radio frequency thermal plasma. For each precursor, the evolution of both temperature and titanium density along the plasma jet is observed. Two different plasma compositions were used to study their effects on the precursor decomposition. For each experiment, x-ray diffraction was performed on the collected powder to correlate OES observations with the structure and composition of the powder. Comparing these results brings a new understanding of the precursor decomposition inside the plasma, while the noted contrasts between water and ethanol as solvent, and between the use of a powder and that of an alkoxide as a source of titanium, help to assess the effect of these parameters on the plasma spray process.