  The results of a study on the evolution of HiPco single-walled carbon
nanotubes during the oxidizing action of H2SO4 and HNO3 are presented. The
process conditions used have been chosen so as to avoid any significant damage
to the nanotube structure. The type and level of functionalization, the
location of the grafted functions on the surface of the nanotube and the
changes in morphological characteristics of the samples were examined by using
a wide and complementary range of analytical techniques. We propose an
explanation for the differences in the oxidizing action of sulfuric and nitric
acids. The combined results allow us to suggest possible reaction mechanisms
that occur on the surface of the nanotube.
