Si and SiO detection in a HMDSO/propane/air flame using spatially resolved optical emission spectroscopy (OES)

Optical emission spectra of rich HMDSO/propane/air and propane/air flames (equivalence ratio Φ=1.33) were recorded using an imaging spectrometer in combination with an intensified CCD camera. The probe area was about 1×0.2 mm2. This is small for the OES signal and allows scans of high spectral and spatial resolution across the flame.Emission lines of Si⁎ (∼252 nm) and SiO⁎ (220-265 nm) were registered at different heights above the slit burner. Si⁎ and SiO⁎ were found up to 10 and 40 mm above the burner, respectively. Up to a HMDSO concentration of 0.015% in the total gas flow a linear dependence between Si⁎ and HMDSO concentration could be proved. Gas temperatures were determined using Raman scattering by N2 molecules and compared with temperatures derived from simulations of CH⁎ (A-X) and OH⁎ (A-X) spectra. N2 and CH⁎ temperatures are within (1950±50) K and (2400±500) K in a good agreement, respectively. At a height of 12 mm above the burner the OH⁎ (A-X) molecules have a temperature of (6700±500) K. We suggest to position substrates for coating applications in a distance of 8 to 10 mm from the burner to use the high OH⁎ concentration for SiO2 layer deposition.

► We analyzed a SiO2 nanoparticle forming propane/air flame using OES spectroscopy. ► The experimental set-up was optimized to get a spatial resolution of 1 mm2. ► We present horizontal scans of Si⁎, SiO⁎, OH⁎, and CH⁎ at different heights through the flame. ► We measured gas temperatures based on N2 Raman scattering as well as OES spectra. ► OH⁎ temperatures of up to 7000 K were found (N2 Raman scattering: 1950 K).