A Study On The Synthesis Of Nano-sized Porous Carbon Materials

Among all the elements known, carbon is unique because of the ability to bond with itself and with other atoms in endlessly varied combinations of chains and rings. By exploiting this property, researchers have made fruitful achievements in the study of synthesis, characterization and application of carbon materials.In this study, hexachlorobenzene (C6d6) was chosen as the assembling unit and reacted with sodium (Na) to synthesize novel carbon materials through a Wurtz reaction. When the two reactants were simply mixed by crush, they reacted violently and produced carbon spheres with a diameter of 50-l00nm and sodium chloride (NaCl) was encapsulated within the outer amorphous carbon shells, which could be confirmed by SEM and TEM. By annealing at 1400 癈 to drive the encapsulated NaCl away, hollow carbon spheres were left with a novel mesoporous structure, as presented in HRTEM. Correspondingly, XRD patterns revealed that carbon shells became graphitic somehow.The effects of organic solvents and catalysts/catalysts precursors on the structure and morphology of products were also investigated in this study. Cyclohexane, instead of benzene, was proven to be a suitable solvent, as it would not pyrolyze in the reaction system. Different catalysts/catalyst precursors led to tubes with different morphologies, as could be shown by SEM.A proper reduction of NiCl2 was found vital for the production of carbon tubes with a yield of over 70%. HRTEM images showed that the tubes had an outer diameter of about 25 nm and a wall thickness of 7-10 nm. SAXS, XRD and BET results revealed that the tubes were amorphous and aggregated by a compact hexagonal arrangement with a highly ordered mesoporous structure. These amorphous carbon tubes are totally different from those graphitized carbon nanotubes obtained through traditional methods. The simple and direct synthesis method is superior to the usual casting method by mesoporous silica materials.