Impact of ferrocene on the structure of diesel exhaust soot as probed with wide-angle X-ray scattering and C(ls) NEXAFS spectroscopy

摘要

We report on the structure of a set of diesel exhaust samples that were obtained from reference diesel fuel and diesel fuel mixed with ferrocene. Characterization was carried out with X-ray absorption spectroscopy (C(ls) NEXAFS) and wide-angle X-ray scattering (WAXS). The reference diesel soot shows a pronounced graphite-like microstructure and molecular structure, with a strong (002) graphite Bragg reflex and a strong aromatic C=C resonance at 285 eV. The mineral matter in the reference soot could be identified as Fe_2O_3 hematite. The soot specimen from the diesel mixed with ferrocene has an entirely different structure and lacks significantly in graphite-like characteristics. NEXAFS spectra of such soot barely show aromatics but pronounced contributions from aliphatic structures. WAXS patterns show almost no intensity at the Bragg (002) reflection of graphite, but a strong aliphatic gamma -side band. The iron from the ferrocene transforms to Fe_2O_3 maghemite.