Synthesis and characterization of silicon carbide, silicon oxynitride and silicon nitride nanowires

Several methods have been employed to synthesize SiC nanowires. The methods include heating silica gel or fumed silica with activated carbon in a reducing atmosphere, the carbon particles being produced in situ in one of the methods. The simplest method to obtain beta-SiC nanowires involves heating silica gel with activated carbon at 1360 degreesC in H-2 or NH3. The same reaction, if carried out in the presence of catalytic iron particles, at 1200 degreesC gives alpha-Si3N4 nanowires and Si2N2O nanowires at 1100 degreesC. Another method to obtain Si3N4 nanowires is to heat multi-walled carbon nanotubes with silica gel at 1360 degreesC in an atmosphere of NH3. In the presence of catalytic Fe particles, this method yields alpha-Si3N4 nanowires in pure form.