ELECTRICAL-PROPERTIES OF PITCH-BASED AND PAN-BASED SEMICONDUCTIVE CARBON-FIBERS

Pitch- and PAN-based semiconductive carbon fibers were prepared by final heat treatments at 400 to 900 degrees C in pure N-2 (O-2 concentration<10(-10)%) and in O-2-mixed N-2 (O-2 concentration=0.2%), Electrical resistivity at 20 degrees 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 degrees 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 N-2. The pitch-based fibers showed smaller thermistor constants than the PAN-based fibers with the same resistivity, but those values became closer wthen heat-treated in pure N-2, Results of XPS showed that oxygen concentration on fiber surfaces was higher in fibers heat-treated in O-2- containing N-2 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 O-2 concentration in atmosphere influences the electrical properties mainly at the surface for PAN-based fibers and in the core for pitch-based fibers.