Molten salt synthesis of silicon carbide nanorods using carbon nanotubes as templates

Abstract

Silicon carbide (SiC) nanorods were synthesised by reacting multi-walled carbon nanotubes (CNTs) with Si particles in a NaCl–NaF binary salt for 4 h at 1100–1200 °C in Ar. Reaction products were analysed by a combination of X-ray diffraction (XRD) and transmission electron microscopy (TEM), including aberration corrected lattice imaging and electron energy loss spectroscopy (EELS). At 1100 °C, 3C–SiC became detectable by XRD but unreacted Si and CNTs were still dominant, while, at 1150 °C, SiC increased at the expense of Si and CNTs. Finally, at 1200 °C, only SiC peaks were seen, indicating the complete conversion from CNTs to SiC nanorods. This synthesis temperature is 200–250 °C lower than that required by the conventional vapour–solid reaction process. The resultant SiC nanorods mostly followed the morphologies of the as-received CNTs, indicating that CNTs had not only served as carbon source but also acted as the templates for the nanorod growth. Most of the resultant SiC nanorods had complex stacking sequences containing various forms of stacking faults, and only some exhibited regular fault-free stacking sequences.