Graphitization of highly porous carbons derived from poly(p-phenylene benzobisoxazole)

We studied the development of graphitization in carbonaceous materials derived from poly(p-phenylene benzobisoxazole) (PBO) pre-activated with carbon dioxide to burn-off degrees of 15 and 51 wt.%. The activated materials were subsequently heat-treated at various temperatures comprised between 1600 and 2700 °C. The changes in porous texture, structure and nanostructure were characterized by gas adsorption analysis, X-ray diffraction, Raman spectroscopy and high-resolution transmission electron microscopy. The two sets of materials pre-activated to different degrees of burn-off exhibited similar changes as a function of the heat treatment temperature. Quite unexpectedly, the presence of porosity generated by physical activation of PBO chars does not affect their graphitizability. The materials seem to retain a sufficiently large degree of the order acquired during the spinning of the PBO fibres to allow the remaining bi-periodic structural units to re-arrange, allowing subsequent graphitization.