The structural evolution of SF-soot (derived from the rapid pyrolysis of ShenFu bituminous
coal) and a carbon black (Printex) was performed for air oxidation at 1273 and 1473
K. The morphology and nanostructure transformations were examined at conversion fractions
similar to 0.2, 0.4, 0.6, and 0.8. Three modes of behavior were evident. The behavior
of SF-soot followed an internal oxidation model (IOM) at 1273 K. The oxygen was able
to fully permeate into the particle core, producing a sphere with variable removal
of the interior structure with conversion. However, at the higher temperature, the
SF-soot formed a concentric spherical structure with gradual consumption of the inner
sphere due to restricted oxygen penetration. The fragmentation of hollow interior
particles, on which the available literature is not extensive, was observed from HRTEM
and SEM micrographs for the first time. During the oxidation of SF-soot, micropores
were mainly generated during the 0-0.2 conversion, while the mesopore surface rapidly
increased during the 0.6-0.8 conversion. The X-ray diffraction (XRD) patterns and
Raman spectra both show that the oxidation of SF-soot is mainly a disordering process.
The graphitic microcrystals were mainly consumed along the longitudinal orientation
during the 0-0.2 conversion but were mainly consumed along the horizontal during the
0.4-0.8 conversion. The true densities of SF-soot and carbon black initially increase
and then decrease monotonically during oxidation. (C) 2019 Published by Elsevier Inc.
on behalf of The Combustion Institute.