In this present work, the effect of additional heat-treatment (AHT) in the range from 1800 o C to 2400 o C on the chemical composition, morphology, microstructure, tensile properties, electrical resistivity, and thermal stability of commercial polyacrylonitrile (PAN)-based carbon fibers was explored by means of elemental analysis, electron microscopy, X-ray diffraction analysis, single fiber tensile testing, two-probe electrical resistivity testing, and thermogravimetric analysis (TGA). The characterization results were in agreement with each other. The results clearly demonstrated that AHTs up to 2400 o C played a significant role in further contributing not only to the enhancement of carbon content, fiber morphology, and tensile modulus, but also to the reduction of fiber diameter, inter-graphene layer distance, and electrical resistivity of "as-received" carbon fibers without AHT. The present study suggests that key properties of commercial PAN-based carbon fibers of an intermediate grade can be further improved by proprietarily adding heat-treatment without applying tension in a batch process.

In this study, commercially available pitch-based carbon fibers of general grade were post-heat-treated using a boxtype high temperature furnace at 1800°C, 2000°C, 2200°C, and 2400°C, respectively. The fundamental characteristics of each heat-treated carbon fibers were investigated in terms of chemical composition, morphology, thermal stability, X-ray diffraction, single filament tensile test, and electrical resistivity. The result showed that the fiber properties were significantly influenced by the post-heat-treatment, indicating the greater effect with increasing treatment temperature. The carbon contents, thermal stability, and tensile properties of the carbon fibers used here were further increased by the post-heat-treatment, whereas the d-spacing between graphene layers and the electrical resistivity were reduced with increasing post-heat-treatment temperature.