Carbon fiber synthesis from pitch: Insights from ReaxFF based molecular dynamics simulations

Despite the potential to lowering fabrication costs of pitch-based carbon fiber (CF) compared to polyacrylonitrile-based CF, large scale utilization is currently limited by the complexity in manufacturing. This is mainly due to the lack of consistency between the pitch structure/chemistry and CF properties under different processing conditions. Here, we employed full atomistic simulations based on reactive force fields to investigate the conversion of pitch precursors to CFs. It was found that at the carbonization stage, the consumption rates of precursors, gas formations, and solid yields (carbonized CFs) are all dependent on the composition and arrangement of molecular moieties in the precursor. Specifically, precursors with sp(3) carbons in the cata-condensed core area have limited decomposition pathways (i.e., limited reaction sites), which leads to the formation of carbonized CFs with similar compositions. Furthermore, carbonized CFs possess distinct structural characteristics, and finally lead to the formation of CFs with different moduli. By analyzing CF crystallinity and elemental composition, general rationales are proposed for the selection of optimal precursors and processing conditions, and thus shed lights on parameter screening during industrial CF synthesis. For instance, inclusion of sp(3) carbons in cata-condensed rings can be preferred over the presence of sp(3) carbons on side chains. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Despite the potential cost advantages of pitch-based carbon fiber compared to polyacrylonitrile-based carbon fiber, large scale utilization is currently hindered by the complex manufacturing process. Through atomistic simulations, it was found that the molecular composition and arrangement of pitch precursors have significant impacts on the properties of carbonized CFs. By analyzing CF crystallinity and elemental composition, guidelines for selecting optimal precursors and processing conditions were proposed to improve industrial CF synthesis efficiency.