Converting PBO fibers into carbon fibers by ultrafast carbonization
Scope
Ultrafast-heating carbonization of poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers to carbon fibers, paired with ReaxFF reactive molecular dynamics to interpret heating-rate effects on gas evolution and carbon-ring organization.
Summary¶
The study demonstrates direct carbonization of PBO precursor fibers into carbon fibers using rapid heating and cooling, targeting cost reduction relative to conventional polyacrylonitrile routes that require separate stabilization. Experimental campaigns vary carbonization temperature, heating rate, cooling rate, and dwell time, reporting mechanical property trends including high tensile strength and Young’s modulus at a relatively low peak temperature when ultrafast thermal profiles are used. Reactive molecular dynamics with the ReaxFF formalism examines how heating rate alters early-stage pyrolysis chemistry, emphasizing relationships between oxygen-bearing gas release and the development of aligned six-membered carbon rings as precursors to graphitic order.
Methods¶
Experiments carbonized PBO fibers under controlled thermal programs; gas evolution during conversion was analyzed to connect volatile release to microstructure and mechanical performance. Complementary ReaxFF reactive molecular dynamics in LAMMPS study PBO-segment oligomer/fiber-style supercells (atom counts and periodic PBC cell in Carbon Method) under ramped temperature programs for pyrolysis/carbonization with explicit variation of heating rate to probe differential gas release (for example CO, H₂O, H₂, with lesser CO₂ and N₂) and clustering of all-carbon six-membered rings, building on the group’s prior PBO ReaxFF line (cited in the Carbon text). The manuscript links simulation trends to ultrafast experimental heating that suppresses O-containing gas release relative to slower ramps (as stated in the abstract thread).
MD protocol (ReaxFF). Engine is LAMMPS (as in the 2019 PBO ReaxFF reference in the Carbon text); simulation cell is 3D PBC with PBO strands at roughly 0.1–0.3 g/cm³ initial density (see main text); timestep/thermostat and ramp durations (ps–ns) are N/A on this one-page summary—Section 2 and SI. Barostat / NPT production: N/A unless the carbonization MD uses constant pressure; default assumption is constant-volume heating of the polymer cell (confirm in PDF). Electric field: N/A. Umbrella / metadynamics / replica: N/A—the ReaxFF work is direct ramped MD on PBO models, not a rare-event enhanced sampling study in the sense of metadynamics.
Findings¶
Ultrafast heating and cooling produced PBO-derived carbon fibers with reported breakthrough tensile strength and Young’s modulus at a peak carbonization temperature near 1000 °C, highlighting heating rate—and cooling rate—as decisive processing levers alongside temperature and dwell time. Reactive simulations indicate that faster heating can suppress oxygen-containing gas release during early carbonization, promoting alignment of all-carbon rings and more favorable microstructural development consistent with improved mechanical response. The combined results frame heating-rate control as a practical knob for PBO-derived carbon fiber quality beyond traditional emphasis on peak temperature alone.
The paper thereby links process window (ramp shape) to atomistic fragmentation pathways, which is the sense in which ReaxFF adds interpretive value beyond post-mortem microstructure alone.
Limitations¶
Atomistic models capture finite segments and time windows of pyrolysis; quantitative agreement with continuum fiber experiments requires careful interpretation of temperature definitions, sample sizes, and ReaxFF limitations for condensed-phase pyrolysis chemistry.
Relevance to group¶
Direct van Duin-group ReaxFF application to polymer carbonization and carbon-fiber manufacturing, aligned with other precursor pyrolysis studies in the knowledge base.
Citations and evidence anchors¶
- https://doi.org/10.1016/j.carbon.2019.12.067