New method of preparing SiC whiskers by in-situ growth of nanocomposite Si/C/N powder

SiC whiskers was prepared in-situ by annealing specially prepared Si/C/N nanocomposite powder at 1550-1750°C under N₂ for 1h without any catalysts. The TEM photo of the SiC whiskers formed at 1550°C was given; it shows that their diameters were in the range of 100-200nm, and their lengths were in the range of 0.5-5μm. It also shows that the whiskers contain many defaults and twins. Both the diameter and the length of each whisker increase with the increasing of temperature. At 1750°C, the diameters were in the range of 0.2-1μm and the lengths were in the range of 2-10μm. The tips of whiskers were plane rather than spherical; this means that the whiskers were formed according to the Vapor-Solid (VS) mechanism but not according to Vapor-Liquid-Solid (VLS) mechanism. X-ray diffraction (XRD) analysis indicated that the purity of SiC whiskers formed with the method was very high, very different from that of whiskers prepared with other methods. XRD also indicated that, in whiskers prepared with this method, β-SiC was about 95% and the rest was α-SiC.