Effects of doping aluminum chloride on stabilization and properties of polyacrylonitrile‐based carbon fibers

Abstract

Polyacrylonitrile (PAN) gel fibers were immersed in 0–2.0 wt % aluminum chloride (AlCl3) aqueous solutions to fabricate Al‐doped PAN fibers and the resultant carbon fibers (CFs) on a continuous production line, and the effects of doping with AlCl3 on the stabilization and properties of PAN‐based CFs were investigated. The Al content in the PAN fibers and in the resultant CFs is 2800 and 5700 ppm, respectively, at 2.0 wt % doping solution concentration. Al compound particles were speculated to exist in the pores of PAN fibers, and they show strong inhibiting effects on both cyclization and oxidation reactions. However, the disadvantages can be overcome by a longer stabilization period or a higher stabilization temperature to produce CFs that have comparable mechanical properties with 2.98–3.20 GPa tensile strength and 210–220 GPa Young's modulus. Thermogravimetric analysis in air shows the weight of CFs increases remarkably from 19.0% to 59.3% at 850°C for Al content 0–1900 ppm, while it gradually decreases over 1900–5700 ppm.