Controlling Iron Volatilization and Graphitization Through Pyrolysis in Benzoxazine Carbon Precursors

In this work, two benzoxazine networks, BisA-An and BisA-Fu, were synthesized with and without 15 wt % ferrocene to investigate the influence of polymer network structure on iron volatilization and subsequent graphitization behavior. It is hypothesized that increased network rigidity, associated with higher cross-link density, would suppress iron volatilization during pyrolysis to 1000 °C, thereby increasing the availability of catalytically active iron at graphitization temperatures (>700 °C). Iron evolution during pyrolysis was monitored using simultaneous thermal analysis-mass spectrometry (STA-MS), which revealed that the network with the least cross-linking functionality exhibited approximately an order of magnitude greater iron volatilization compared to networks with higher cross-linking functionality (from 1.27 × 10^-10 amps to 1.31 × 10^-11 amps). X-ray diffraction (XRD) analysis showed corresponding differences in graphitic crystallite development, with a calculated crystallite thickness (Lc) of 3.44 nm in the sample with less cross-linking functionality and 4.31 nm observed in samples with higher cross-linking functionality. These results demonstrate that polymer network structure governs iron retention during pyrolysis and, consequently, influences the extent of catalytic graphitization.