Simple approach to fabricate SiC–SiO2 composite nanowires and their oxidation resistance

A simple thermal evaporation technique without catalysts from an exterior has been developed to synthesize SiC–SiO2 composite nanowires. Silicon powder of micrometer size or coarser silicon powder was heated in a horizontal tube furnace up to 1350 °C under CH4 gas flow. Large quantity of as-grown wool-like products was obtained on the silicon powder oxidized at 800 °C in air for 1 h. Characterization by an X-ray diffractometer, a field-emission scanning electron microscope, a transmission electron microscope and an infrared spectroscope indicated that these products were SiC core/SiO2 shell composite nanowires. SiC core diameter was approximately 20–80 nm with SiO2 shell of about 10–20 nm in thickness and length up to 1–2 mm. Both of separate heating process, i.e., heating for oxidation of raw Si powder and nanowires synthesis reaction separately, and continuous heating process, i.e., multi-step continuous heating for oxidation and reaction, could produce SiC–SiO2 core/shell nanowires. Based on thermogravimetric analysis, it was suggested that the synthesized nanowires had better oxidation resistance than that of SiC nano-sized powder.