Cellulose nanofibers as rheology modifiers and enhancers of carbonization efficiency in polyacrylonitrile

The energy requirements for the production of high quality carbon fiber and other carbon-based materials made by carbonization is a key factor limiting the commercial application of these materials. With the aim of enhancing the carbonization efficiency, we have prepared polyacrylonitrile (PAN) based precursor materials doped with high aspect-ratio cellulose nanofibers (CNF) derived from Australian spinifex grass (T. pungens). This was achieved by systematically investigating the rheology and electrospinning properties of composite fibers of PAN and CNF prepared at various CNF concentration levels and subsequently stabilized and carbonized. The carbon properties were characterized by X-ray diffraction and Raman spectroscopy. Upon carbonization, the incorporation of CNF into the PAN precursor led to changes in the crystallite and graphitic structure of the carbon materials, and these changes found to be closely related to the CNF concentration. CNF loadings of 0.5-2 wt % resulted in spinnable solutions with well-ordered carbon structures exhibiting a reduced Raman D/G ratio and an increased [002] band intensity by XRD. These spinifex CNF additives highlight a new approach for enhancing the energy efficiency of the carbonization process for PAN-based precursors.