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

Polyacrylonitrile (PAN) was modified with cobalt chloride at 90 degrees C f or 5 min. The carbon films prepared from original and modified PAN films we re carbonized up to 1300 degrees C. The structure of the resulting carbon f ilm was studied using X-ray diffraction and Raman spectroscopy. The stackin g size obtained from X-ray diffraction approaches the L-c value of the resu lting carbon films as the heat treatment temperature increased. The mean av erage carbon basal planes in crystalline (Lc/d) also increased with increas ing pyrolysis temperature. Raman spectra confirmed the progressive structur al ordering as treatment temperature increased. During pyrolysis, a substan tial decrease in the intensity of the band near the 1350 cm(-1) region was observed, indicating a decrease in the disordered structure. The crystal si ze (L-a) of the resulting carbon films also showed a remarkable increase wi th increased heat treatment temperature. The resulting carbon films develop ed from the modified PAN films had higher L-c and L-a than those developed from the original PAN film. It was established that cobalt catalyzes graphi tization of amorphous carbon during pyrolysis. This modification not only p romoted the growth of crystal size but also increased the close packing of the carbon basal planes. (C) 1999 John Wiley & Sons, Inc.