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Cost-effective carbon fiber precursor selections of polyacrylonitrile-derived blend polymers: carbonization chemistry and structural characterizations

Scope

ReaxFF reactive MD of PAN-based blend precursors during carbonization, with Raman and TEM validation, identifies PAN/cellulose as a strong candidate for high-yield, graphitic carbon fiber precursors.

Summary

Polyacrylonitrile (PAN) is the dominant carbon fiber precursor but costly; blending PAN with commodity or bio-based polymers can lower cost if carbonization chemistry remains favorable. The study combines ReaxFF reactive molecular dynamics with experimental Raman and TEM on selected blends, tracking all-carbon ring formation, O- and N-bearing species, and migration toward turbostratic graphene-like structure.

Industrial carbon fibers require high char yield and graphitic microstructure; the paper uses atomistic trajectories to rationalize why some blends outperform others despite similar initial polymer cost.

Methods

A — ReaxFF (PAN-blend carbonization)

  • Lineage: ReaxFF description for C/H/O/N chemistry in polyacrylonitrile-derived blends (parameter references in Nanoscale Methods).

B — Reactive MD

  • Systems: Neat PAN, oxidized PAN, PAN/nylon 6,6, PAN/cellulose stacks representing precursor films before full carbonization.
  • Protocol: Thermal ramps / holds for carbonization chemistry; RDFs, C–C bond-length distributions, sp\(^2\) fractions, and ring/heteroatom evolution as diagnostics.
  • Software / ensemble: LAMMPS ReaxFF as stated in the article; timestep and thermostat in Methods.

C — Quantum chemistry

  • Supplementary QM benchmarks if cited for validation of key bond energies (see article).

D — Experiments

  • Raman spectroscopy and TEM on carbonized fibers from the same blend families; compare crystallinity and graphitic character to simulation trends.

Simulation heating programs should be compared qualitatively to lab pyrolysis schedules when interpreting timing of ring growth; full temperature programs are in the Nanoscale Methods.

ReaxFF pyrolysis MD: Engine: LAMMPS; C/H/O/N polymer blend supercells ( PAN / nylon / cellulose ) with 3D PBC; NVT with ramped temperature (K) schedules and sub-fs timestep; Nose–Hoover-class thermostat during heating; ps–ns stages; barostat N/A for fixed-volume pyrolysis boxes; hydrostatic pressure N/A unless NPT; E-field N/A; replica exchange N/A; atom counts in Nanoscale.

Findings

Among the four precursors examined, PAN/cellulose shows the highest simulated carbon yield and the most extensive all-carbon ring clustering and graphitic growth; Raman and TEM on PAN/CL-derived carbon fibers indicate high crystallinity, consistent with the ReaxFF picture. The authors trace gasification and carbonization pathways for PAN/CL and argue that cellulose acetal moieties can catalyze cyclization of the blend, suggesting bio-based additives with similar functionality as tunable blend partners. PAN/CL is argued as a cost-effective route because cellulose is abundant, the blend can avoid a separate oxidation step, yield and ring formation are strong, and mechanical enhancement of the resulting fibers is plausible.

The convergence of simulation and microscopy supports using ReaxFF as a screening tool for precursor blends before lengthy fiber-spinning trials.

Nanoscale documents full simulation cell compositions, heating ramps, Raman peak assignments, and TEM statistics for each blend so carbon-fiber benchmarking can trace metrics to the peer-reviewed figures.

Limitations

Atomistic models capture finite segments and heating protocols that should be cross-checked against the full Methods section for system sizes, ramp rates, and equilibration windows.

Relevance to group

Group-authored ReaxFF study of polymer pyrolysis and carbonization with direct experimental validation.

Citations and evidence anchors