Mechanism of Polyacrylonitrile-Based Carbon Fiber Carbonization Optimization by Fullerene for High-Performance Carbon Fibers

Enhancement arising for polyacrylonitrile (PAN)-based carbon fibers from C60 fullerene, which possesses a unique zero-dimensional structure and similar nano-scale dimensions, remains rarely reported and merits investigation. In this study, C60@PAN precursor fibers were fabricated via wet spinning and subsequently subjected to stabilization and carbonization, yielding composite carbon fibers with superior properties that were compared against neat PAN-based carbon fibers by means of X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), and other characterization techniques. Through multi-scale structural characterization, combined with molecular dynamics (MD) simulations and first-principles density functional theory (DFT) calculations, mechanisms underlying C60-induced reinforcement in PAN-based carbon fibers were systematically explored. Experimental and characterization results revealed that incorporation of C60 did not impair spinnability of PAN; composite precursor fibers exhibited a uniform and continuous morphology without significant defects. During stabilization, C60 reduced activation energy of cyclization reactions, moderated exothermic behavior, and provided structural support via an induced crystallization effect. After carbonization, composite fibers exhibit a markedly improved carbon layer stacking order, graphitization degree, and a concurrent increase in char yield. MD and DFT further disclosed that C60 dispersed homogeneously in PAN at room temperature, facilitating uniform orientation of PAN chains; at elevated temperatures, gradual fragmentation and fusion of conjugated cage structures of C60 served as critical templates for enhancing carbon structural ordering. This study elucidates the promoting mechanism of C60 in a favorable microstructural arrangement of PAN precursor fibers and subsequent stabilization−carbonization processes, offering experimental evidence and theoretical guidance for structural optimization and performance enhancement of high-performance PAN-based carbon fibers. The high-performance carbon fibers fabricated via this strategy find applications in commercial aerospace and low-altitude aircraft sectors. Moreover, the variations in electrical properties induced by C60 incorporation also warrant further investigation in the fields of capacitors and batteries.