Abnormal dark conductivity of carbon fibers

Summary form only given, as follows. Dark conductivity of PAN- and pitch-based fibers heat treated at different temperatures (T_HT) was investigated in the temperature range 10-360 K. The measurements were performed lit individual fibers. Abnormal temperature dependence of the dark conductivity was found for PAN fibers with T_HT = 1400, 1600, 2000, 2200, 2400O C. Namely, at 230-320 K, the conductivity decreased by 1.5-20% with increasing temperature. This effect is absent in the case of well-structured fibers: PAN with Tm = 1800, 2600°C and pitch with T_HT = 3000 C.