Abstract
Pitch- and PAN-based semiconductive carbon fibers were prepared by final heat treatments at 400 to 900°C in pure N2 (O2 concentration<10-10%) and in O2-mixed N2 (O2 concentration=0.2%). Electrical resistivity at 20°C, thermistor constant and resistivity changes by applying high-voltage pulses were measured and compared with two kinds of carbon fibers. Below the heat treatment temperature of 700°C, the pitch-based fibers showed higher resistivities than the PAN-based fibers. The difference in resistivity of these fibers increased by heat treatments at lower temperatures and in pure N2. The pitch-based fibers showed smaller thermistor constants than the PAN-based fibers with the same resistivity, but those values became closer wthen heattreated in pure N2. Results of XPS showed that oxygen concentration on fiber surfaces was higher in fibers heat-treated in O2- containing N2 and that the effect of heat treatment atmosphere was evident in deeper region from the surface in the pitch-based fibers. It was assumed that the O2 concentration in atmosphere influences the electrical properties mainly at the surface for PAN-based fibers and in the core for pitchbased fibers.
