In-situ growth of silicon carbide nanowire (SCNW) matrices from solid precursors

In an effort to develop highly porous silicon carbide for high temperature air filtration, an alternative approach to forming silicon carbide nanowires (SCNW) was developed by blending carbon containing materials with silicon powder and heating these precursors to 1400 °C. The mixing ratio of precursor materials and processing temperature were investigated with respect to the formation of SCNWs. Results indicate that anthracite and starchy materials can yield high purity SiC ceramics, yet these combinations did not produce SiC nanowires. SCNWs were successfully grown from a combination of guar gum and silicon powder precursors at 1400 °C, when held for 4 h with an argon flow rate of 1 L/min. The produced SiC is a high purity product with nanowire diameters of approximately 40 nm and ranging in length from about 100 nm to several micrometers in length. Iron was used to catalyze the nanowire growth through vapor-liquid-solid (VLS) mechanisms by adsorbing the silicon and carbon vapor at the iron rich tip, which then led the nanowire growth. TEM analysis revealed the growth of SCNWs followed the [1,1,2] direction. A wafer comprised of the synthesized SiC nanowire matrix has much higher hardness compared with a wafer of the porous commercially available cordierite.