Analysis and characterization of orientation structure of pre-oxidized PAN fibers in high magnetic fields

PAN fibers pre-oxidized at 240 °C, 260 °C, 280 °C, 300 °C were treated in 8 T, 12 T, 16 T high magnetic fields, respectively. The experimental result implied that there were two kinds of magnetic units cyan and carbon-nitrogen heterocycle in pre-oxidized PAN fibers, and the movement of magnetic units resulted in changes of orientation structure of pre-oxidized PAN fibers in high magnetic fields. Overall orientation increased with increase of magnetic field intensity and extension of processing time, whereas change of crystalline orientation depended on magnetic field intensity and content of carbon-nitrogen heterocycle due to the competition of two magnetic units. Furthermore, magnetic fields induced the conversion from amorphous region to crystal region and improved crystalline properties of pre-oxidized PAN fibers.