Stabilization and Carbonization of Electrospun Organosolv Lignin Fibers from Miscanthus x giganteus to Produce Biobased Carbon Fiber

This paper focuses on the stabilization and carbonization of fiber mats produced by electrospinning organosolv lignin derived from Miscanthus x giganteus, with no additives. Stabilization and carbonization were carried out to obtain electrospun lignin fiber mats. The stabilization step was carried out under air at a heating rate of 0.25 °C/min to maximum temperatures of between 200 and 300 °C. Then, the carbonization step was performed under nitrogen at a heating rate of 5 °C/min to maximum temperatures of 800 and 1000 °C and durations of 1 and 2 h. TGA, DSC, SEM–EDS, XPS, FTIR, Raman, and XRD analyses were carried out to determine the specific characteristics of the stabilized and carbonized material obtained. The DSC analysis showed that the fibers were well stabilized, which resulted in an increase in the glass transition temperature (Tg) compared to the starting material. SEM analysis showed an overall 35% decrease in the average fiber diameter during the stabilization and carbonization processes. The results of the Raman spectroscopy showed an ID/IG ratio of about 1 for all the carbon fibers, which indicates that the material tends to graphitize. X-ray diffraction analysis of the stabilized and carbonized fibers revealed a spectral peak around 23° for all samples and demonstrated a partially ordered (turbostratic) state of the material. Finally, ultra-thin carbon fibers with a carbon content of 97% were obtained after carbonization at 1000 °C.