Iodine-mediated high-pressure high-temperature carbonization of hydrocarbons and synthesis of nanodiamonds

Abstract Carbonization behavior of iodinated adamantane, adamantane and naphthalene in mixtures with germanium iodide or iodine was studied at pressures of 3.5 and 8 GPa to elucidate diamond-forming catalytic activity of iodine. Using XRD, Raman spectroscopy and TEM as characterization methods, we have found that pyrolysis of iodinated adamantane at 8 GPa is accompanied with formation of nanodiamonds at temperatures exceeding 800 °C. Post-pyrolysis growth of nanodiamonds points out the diamond-forming catalytic activity of iodine. In the samples obtained from precursor mixtures, only graphite was detected as a pyrolysis product, which means that hydrocarbon iodination is a prerequisite for iodine-mediated synthesis of nanodiamonds.