Scanning Electron Microscopy and Raman Spectroscopy Studies of ULSD and Biodiesel Soot Loading in a Diesel Particulate Filter

Diesel particulate filters (DPFs) were loaded and fractured to determine the time effect of loading, and loading differences between ULSD and a B20 biodiesel blend. DPFs were loaded in parallel for exposure times of 1, 2, 5 and 10 hours. Scanning electron microscopy and Raman spectroscopy were used to visualize loading and analyze the carbon structure of particulates on the filter substrate. Images of the soot cake were captured and the ‘pore-bridge’ was identified as an important feature in DPF functionality. Raman analysis revealed that the nature of the carbon soot structure did not become increasingly graphitic with loading time; the soot cake was observed to be a disordered, variable feature.