Raman spectroscopic study of the microstructure of carbon films developed from cobalt chloride-modified polyacrylonitrile

Polyacrylonitrile (PAN) was modified with cobalt chloride at 90°C for 5 min. The carbon films prepared from original and modified PAN films were carbonized up to 1300°C. The structure of the resulting carbon film was studied using X-ray diffraction and Raman spectroscopy. The stacking size obtained from X-ray diffraction approaches the Lc value of the resulting carbon films as the heat treatment temperature increased. The mean average carbon basal planes in crystalline (Lc/d) also increased with increasing pyrolysis temperature. Raman spectra confirmed the progressive structural ordering as treatment temperature increased. During pyrolysis, a substantial decrease in the intensity of the band near the 1350 cm−1 region was observed, indicating a decrease in the disordered structure. The crystal size (La) of the resulting carbon films also showed a remarkable increase with increased heat treatment temperature. The resulting carbon films developed from the modified PAN films had higher Lc and La than those developed from the original PAN film. It was established that cobalt catalyzes graphitization of amorphous carbon during pyrolysis. This modification not only promoted the growth of crystal size but also increased the close packing of the carbon basal planes.