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

A simple thermal evaporation technique without catalysts has been developed to synthesise SiC-SiO2 composite nanowires. Silicon powder of micron size or coarser silicon powder was heated in a horizontal tube furnace up to 1350 C under CH4 gas flow. A large quantity of as-grown wool-like product was obtained on the silicon powder oxidised at 800 C in air for 1 h. Characterisation using XRD, FESEM, TEM and IR spectroscopy indicated that these products were SiC core/SiO2 shell composite nanowires. The SiC core diameter was approximately 20-80 nm with a SiO2 shell of about 10-20 nm in thickness and length up to 1-2 mm. Both heating processes, i.e., heating for the oxidation of raw Si powder and nanowire synthesis reaction separately, and a continuous heating process, i.e., multi-step continuous heating for oxidation and reaction, produced SiC-SiO2 core/shell nanowires. Based on TGA, it was suggested that the synthesised nanowires had better oxidation resistance than SiC nano-sized powder.