In situ generation of graphene network in silicon carbide fibers: Role of iodine and carbon monoxide

By iodine curing of polycarbosilane fibers followed by sintering under a controlled atmosphere of carbon monoxide, a unique strategy is developed for the in situ growth of graphene networks inside silicon carbide fibers. In the resulting fibers, three-dimensionally interconnected few-layered graphene sheets are well-dispersed in the nanocrystalline SiC, allowing for fast electron transport through the graphene networks. The roles of iodine and carbon monoxide in fabricating the graphene-network embedded SiC fibers are elucidated. The distinct evolution of graphene structure was observed in the iodine-treated Si(O)C using transmission electron microscopy and Raman spectroscopy. The iodine incorporated in the fibers induces the sp²-hybridization of carbon, generating carbon–carbon double bonds and graphene seeds such as reduced graphene oxide, which are supposed to grow into graphene layers at elevated temperatures. Carbon monoxide is employed as a component of the atmospheric gas mixture during the decomposition of Si(O)C to suppress the evolution of SiO and CO gases, thereby restraining coarsening of SiC nanocrystallites and maintaining the integrity of the graphene network. These processes pave the way for designing graphene structures in polymer-derived ceramic materials for a broad range of applications.