Scanning transmission electron microscopy (STEM) coupled with energy dispersive x-ray analysis (EDX) and electron energy-loss spectroscopy (EELS) has been used to characterize the elemental composition and oxidation conditions of various soot samples. The STEM employed in this investigation was the Vacuum Generators HB603-MIT, with a microanalyical resolution approaching 1 nm, that allowed the analysis of individual soot particles and aggregates.
The aim of this research is quantification of the EDX spectra which is possible after background and absorption corrections. This information can then be used for comparative studies of different fuels and combustion processes.
EELS has been employed to determine the amount of graphitic carbon in a soot particulate, and the detection of trace elements of low atomic number. It has been shown in soot that for Carbon the energy-loss of the p shell electrons increases with the amount of oxidation at high temperatures.
Analysis and characterization of gas turbine soot, collected from an engine exhaust duct of a 737-300 aircraft showed an abundance of different elements.