NIR FT Raman spectroscopic study of flame soot

Abstract

During combustion soot goes through different molecular structures. The Raman spectra of flame soot, collected in premixed flames at different flame heights and flame temperatures, were analysed in regard to their structural properties and in comparison with those of disordered graphite. Besides the G- and D-band of disordered graphite, a third Raman band at approximately 1188 cm^-1 was observed which was tentatively assigned to mixed s–s bondings or to the C–C and C2C stretching vibration modes of polyene-like structures. The G-band position, the D-band width, and I_D/I_G intensity ratio describe the graphitic order in the particles. According to this result the graphitic order of the untreated soot particles decreases with decreasing flame temperature and flame height, whereas the size L_a of the graphitic sheets is nearly constant.