(151e) In-Situ Saxs Measurement of Sio2 Nanoparticle Growth in Diffusion Flames

Small angle X-ray scattering (SAXS) is applied to analyze HMDSO laden diffusion flames (production rate 5 g/h SiO₂) of varying conditions for the production of agglomerated and non-agglomerated SiO₂ particles. The in-situ analysis allowed tracking the evolution of primary-particle diameter, mass-fractal dimension, geometric standard deviation, silica volume fraction, particle number density, radius of gyration of the aggregate, and number of primary particles per aggregate in the flame centerline as well as sidelines. Different growth mechanisms were observed when changing the O₂ flow rates (2-10 l/min) which affected the temperature profile within the flame measured by in-situ Fourier transformed infrared (FTIR) spectroscopy, subsequently flame height and residence time. Thermophoretic sampling (TS) taken at several heights above the nozzle provided transmission electron microscopy (TEM) images for direct comparison with SAXS data. The focus of this study was kept on the evolution of particles off-line the centerline to understand the particle growth mechanisms at these sites for better understanding of final products. However, a distinct discussion of particle growth in the centerline compared to literature is provided.