Sulfur-assisted approach for the low-temperature synthesis of β-SiC nanowires

Silicon carbide (SiC) nanowires coexisting with amorphous graphite particles were initially produced by using silicon powder, tetrachlorethylene, metallic Na, and sulfur powder as reactants in an autoclave at 130 degrees C. Pure beta-SiC could be finally obtained after heating the sample in concentrated H2SO4 by refluxing at 180 degrees C, which was proved by the X-ray powder diffraction patterns. Transmission electron microscopy (TEM) images and scanning electron microscope (SEM) images show that the product is mainly composed of SiC nanowires (over 75 %) with an average diameter of about of 30 run and lengths up to tens of micrometers. High-resolution TEM shows that the nanowires have preferential growth along the [111] direction. It was found that when sulfur was absent, crystalline beta-SiC powders could not be obtained unless the target temperature was raised higher than 270 degrees C. In the mean time, the ratio of the nanowires also dropped dramatically (approximate to 20 %). The effects of sulfur, reaction time, and temperature on the morphologies of the final products, together with the properties of the final products, were also discussed. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).