Synthesis of novel hybrid carbon nanomaterials inside silicon carbide nanotubes by ion irradiation

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A novel hybrid carbon nanomaterial was synthesized by ion irradiation of a C–SiC coaxial nanotube. The hybrid consisted of one-dimensionally stacked graphene nanodisks with diameters less than 50 nm and cylindrical multiwalled carbon nanotubes inside an amorphous SiC tubular layer. A sudden emergence of new continuous graphitic layers in the microstructure were observed by in situ transmission electron microscopy following ion irradiation, where these layers were perpendicular to the nanotube's length direction. The SiC crystals in the C–SiC coaxial nanotube became amorphous, also due to the ion irradiation, although the critical amorphization dose was higher than that for bulk SiC. Most remarkably, the carbon layer remained crystalline, even after an irradiation dose higher than 20 dpa (displacement per atom). Such results show that these carbon layers possess better resistance against amorphization when subjected to ion irradiation than the SiC layers in the C–SiC coaxial nanotube. The lattice plane spacing of the carbon layer increases up to the point when irradiation damage lead to the complete amorphization of SiC crystals, after which it starts to decrease. This demonstrates that the carbon layer experiences high compression stress during ion irradiation. Thus, the ion irradiation of C–SiC coaxial nanotubes gives rise to a novel development of the microstructure and can be considered as one of the new synthetic processes for making novel carbon nanomaterials.