Authors: A Burkert D Müller W Paa
Publish Date: 2015/02/07
Volume: 24, Issue: 4, Pages: 683-689
Abstract
Acoustic emission AE measurements as well as laser light scattering experiments were performed during SiO2 layer deposition SiO2 was generated in lowtemperature atmospheric plasma torches ≤500 W which were seeded with hexamethyldisiloxane These AE measurements can be used to detect the necessity for nozzle cleaning online The plasma torches were used to obtain highquality SiO2 coatings For electrical power of less than 350 W we observed parasitic SiO2 deposition in the burner nozzle which decreases the nozzle aperture within several hours of operation time No parasitic SiO2 deposition inside the burner nozzle was observed when the plasma source was operated at more than 350 W The reduced nozzle aperture causes increased plasma velocities and acoustic noise Especially burstlike increases of this acoustic emission were assumed to be correlated to the ejection of particles This hypothesis could be confirmed by measurements of scattered light from a sheet of laser light at 248 nm The obtained correlations suggest using a microphone as a lowcost monitor for the degree of parasitic deposition inside the plasma burner nozzle The threshold for acoustic noise detection has to be chosen low enough to avoid burstlike emission of particles
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