Synthesis of [beta]-SiC/SiO2 core-shell nanowires by simple thermal evaporation

Beta-SiC/SiO2 core-shell nanowires were obtained in a mullite boat after the reaction between silicon nanopowder and CH4 gas at 1623 K (1350°C), without adding metal catalysts from outside. The as-grown nanowires were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, scanning TEM, and infrared-ray spectroscopy. The results showed that the typical nanowires consisted of single crystalline β-phase SiC core of 50-70 nm in diameter and a uniform wrapping layer of low crystallinity SiO2 of ∼15 nm in thickness, and their lengths were up to several tens of micrometers. The nanowires axes lay along the [111] direction of β-SiC. Oxygen from the experimental setup or the raw powder should be a key factor to synthesize the core/shell nanowires.