Preparation and characterization of carbon films prepared from poly(vinyl alcohol) containing metal oxide and nano fibers with iodine pretreatment

This research focused on the combination of catalyst effect of metal oxide, thermal conductive effect of carbon nano fibers and iodine pretreatment during carbonization of polymer precursor in order to prepare tough carbon films. Poly(vinyl alcohol) (PVA) composites containing metal oxide (Fe₃O₄) and vapor-grown carbon fibers (VGCFs) were prepared by gelation/crystallization method with the freezing/thawing technique. The dry gel films as precursor were pretreated in the atmosphere of vapor iodine, and then heat-treated at 600-1200 °C. The combined effect of iodine, Fe₃O₄ and VGCF on the carbonization of PVA was analyzed with thermo-gravimetric analysis, X-ray diffraction, and scanning electron microscope in details. Iodine pretreatment for 24 h significantly promoted the dehydration of PVA, and resulted the carbon film with a high crystallinity. Fe₃O₄ as catalyst facilitated the carbonization of PVA at a low temperature of 800-900 °C. The addition of VGCFs was found to play an important role to prepare tough films by mild carbonization due to its high thermal conductivity. The degree of graphitization in the carbon film depended on the filler contents, pretreatment conditions and carbonization conditions. The graphitization degrees for G- and T-components in the film were investigated on the basis of X-ray diffraction intensity distribution from the (0 0 2) plane.