Electrical resistivity measurements of carbon fibers at very high temperatures (300-2500 K)
Christophe Pradere, Jean-Christophe Batsale, Jean-Marc Goyheneche and Rene Pailler
An experimental four probes contact method is presented for the measurement of the electrical resistivity of single metallic and carbon fibers at very high temperature. The difficulty of such measurements is due to the micro scale of the fiber (≈10μm), the important range of temperature (300-2500 K) and the fundamental chemical interaction between the heated fiber and the measurement probes. The main idea to avoid chemical interaction is to use carbon fibers as electrical probes for the measurements. The characterization of a standard tungsten filament allows the validation of the device, the electrical estimation method and the uncertainties calculation. Then, measurements on four carbon fibers (rayonbased, PAN-based and pitch-based) are reported at very high temperature. Typical values for the resistivity of those fibers are between 2 to 40 μΩ.m. Finally, we show relationships between measured electrical resistivity ρE and carbon fibers heat treatment temperature (HTT), structural and mechanical properties. The results show that the resistivity: increases with temperature for high conductive fiber, decreases with temperature for insulated carbon fibers, decreases with growing HTT, increases as the interlayer spacing d002 increases, decreases as the crystalline size Lc increases, resistivity decreases with Young’s modulus increases.
Keywords: Four probes technique, electrical resistivity, high temperature, carbon fibers.