Sol–gel synthesis of Si3N4 nanowires and nanotubes

Silicon nitride nanowires and nanotudes were synthesized from a binary sol–gel route, in which tetraethoxysilane (TEOS) and phenolic resin were used to prepare a carbonaceous silica xerogel and ferric nitrate was employed as additive. Raw Si3N4 product was obtained by heating the xerogel at 1300 °C for 10 h in nitrogen flow (200 ml/min). The Si3N4 sample after purification was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersion X-ray (EDX) spectrum and selected area electron diffraction (SEAD). The results showed that the sample mainly consisted of α-Si3N4 nanowires with a few of nanotubes. Both the nanowires and nanotubes have a diameter of 30–100 nm and a length of hundreds microns. Liquid droplets were also found at the tip of the nanowires, and this indicated that the growth of the nanowires and nanotubes followed the vapor–liquid–solid (VLS) mechanism.