用户论文(2006):《Chinese Science Bulletin》Microstructure characterization of PAN preoxidation fibers prepared with radio frequency plasma
简介:The microstructures of preoxidation fibers
prepared with radio frequency plasma were characterized
in terms of micron, nano and atomic scales
through scanning electron microscopy (SEM), high
resolving transmission el简介:The microstructures of preoxidation fibers
prepared with radio frequency plasma were characterized
in terms of micron, nano and atomic scales
through scanning electron microscopy (SEM), high
resolving transmission electron microscopy (HRTEM),
scanning tunneling microscopy (STM), X-ray diffraction
(XRD), etc. The polyacrylonitrile (PAN) precursors
were first soaked in the oxygen-enriched solvent
and polarized in radio frequency electric field, and
then were oxidized in the atmosphere of oxygen
plasma. The morphology of SEM at micron scales
shows that the wrinkles on the surface of preoxidation
fibers prepared with plasma are shallower, and
the surfaces are more tidy and smoother than the
unsoaked samples prepared with usual electric furnace,
and the uneven radial structure is improved.
The results of XRD calculation show that the graphitization
degree and microcrystalline size get larger
and the interlayer spacing gets smaller. Also, the
lattice stripe and edge of bedding plane (002) can be
observed from HRTEM at nano scales. From STM
images at nano and atom scales, the microfibrils
were found to be composed of ultrafibrils that closely
twined and arranged, forming the left spiral structures
spreading to fiber axis, and the carbon atoms on the
surface of microcrystalline were found to have the
trend of directional arrangement. All the above
characterization results indicate that the plasma
method effectively makes the internal and external
oxidation of PAN precursors at the same level, so
that the radial structure difference of preoxidation
fibers is reduced.详细>