The effect of thermal pretreatment temperature on the diameters and mechanical properties of asphaltene-derived carbon fibers

Preparation of high-performance carbon fibers from low-cost precursors, such as asphaltenes, is of great importance to the mass production of carbon fibers. In this investigation, asphaltenes from a solvent de-asphalting process were thermally pretreated at various temperatures to obtain asphaltene-based precursors. Thermal pretreatments, especially at higher temperatures up to 350 degrees C, produced much higher fiber winding speeds (750 m/min) and smaller as-spun fiber diameters (7-8 mu m). A bimodal Weibull distribution of failure stress was found for carbon fibers derived from pretreated asphaltenes precursors. A higher Weibull modulus (m(3) = 3.47) was observed at lower failure stresses, which is attributed to the presence of some uniformly distributed defects. A lower Weibull modulus (m(4) = 0.67) was found at higher failure stresses, indicating the presence of clustered defects. Elemental analyzer, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to understand chemical and microstructure evolution of the pretreated asphaltenes and the derived fibers during various stages of fiber treatments.