Enhanced tensile modulus in polyacrylonitrile-based carbon fibers via ex situ boron doping in continuous catalytic graphitization

High tensile modulus carbon fibers (CFs) are essential for advanced applications in aerospace, automotive, and automation device arm for display due to their exceptional mechanical properties. However, achieving a highly ordered graphitic structure in polyacrylonitrile (PAN)-based CFs remains challenging due to their inherent disordered carbon structure, even under high-temperature treatments. This study introduces an innovative approach to overcoming these limitations by combining ex situ boron doping with a continuous catalytic graphitization process. PAN-based CFs were prepared using a wet-spinning process, followed by catalytic graphitization under precisely controlled conditions. Boron catalysis significantly enhanced the graphitic domain structure growth and crystallinity, leading to a remarkable tensile modulus exceeding 500 GPa. Optimal stretching conditions during graphitization further contributed to the alignment of graphitic layers which induced high tensile modulus. The results revealed a strong correlation between crystallinity and tensile modulus, with boron-catalyzed CFs (509.2 GPa) exhibiting a 1.27-fold improvement in tensile modulus compared to non-catalyzed CFs (400.4 GPa). These findings provide valuable insights into the role of boron catalysis and controlled processing in achieving advanced mechanical properties, offering a foundation for further development of high-performance carbon fibers.