Transmission electron microscopy of pyrolytic carbon coatings deposited in a hot-wall reactor: Preferred orientation and stacking character of graphitic crystallites

摘要

Pyrolytic carbon coatings onto graphite foils have been deposited using methane- or propane-hydrogen mixtures as precursors. The effect of the molecular structure of hydrocarbon precursor and deposition temperature on the microstructure of the coatings has been examined by transmission electron microscopy coupled with electron diffraction. The correlation between preferred orientation of graphitic domains at the μm-scale and their stacking character at the nm-scale is studied. With increasing deposition temperature, the preferred orientation observed on the μm scale is increased. High-textured coatings are formed from propane-hydrogen mixtures while low- and medium-textured coatings are obtained from methane-hydrogen mixtures. The degree of the preferred orientation is found to be inversely proportional to the diameter of the nm -sized graphitic domains, L_a, and values of the interplanar distance in domain, d_(002).