Si3n4 Synthesis

A novel synthesis method to prepare Si3N4 nanowires from the amorphous silicon nitride (a-Si3N4) powder synthesized by low-temperature vapor-phase reaction method was investigated. Highly crystallized α-Si3N4 nanowires were synthesized from the heat-treatment of a-Si3N4 powder under ammonia atmosphere. The surface of the nanowires was smooth and clean without any attached particles. The thickness of the nanowires was in the range ~200–300 nm with the lengths of tens of micrometers. The nucleation of nanowires from the reaction between SiO and N2 occurs on the surface of a-Si3N4 powder, which is covered by a thin layer of SiO2, and the nanowires grow from the re-arrangement of Si and N atoms of the a-Si3N4 powder. The reduction of SiO2 to SiO …show more content…
As a result, a variety of synthesis methods have been attempted to prepare Si3N4 1D nanostructures with various morphologies.10–16 Yang et al. synthesized Si3N4 nanobelts by the catalyst-assisted (e. g., FeCl2, NiCl2, and Al powder) pyrolysis of polysilazane.12,15,17 Huo et al. reported the direct nitridation of Fe–Si alloy particles.14 Shuyue et al.18 and Juntong et al.19 used catalytic thermal-CVD method. Yin et al. reported the vapor–solid reaction of NH3 with SiO.20 Zhang et al.21 and Wang et al.13 prepared Si3N4 nanowires through the reaction of silica gel and carbon nanoparticles. Zhang et al. synthesized Si3N4 nanowires by heating Si powders or Si/SiO2 powder mixture in N2 or NH3 atmosphere with or without Fe or Ni powders.22 Kim et al.23 and Xie et al.24 synthesized Si3N4 nanowires by the reaction of silicon substrate and NH3 with Fe nanoparticles as the catalyst. Zhang et al. synthesized Si3N4 nanowires via the direct crystallization of amorphous Si3N4 (a-Si3N4) powder under high temperature in N2 flow25, but is not consistent with …show more content…
The catalytic growth of Si3N4 nanowires has been explained by the vapor–liquid–solid (VLS) mechanism proposed by Wagner et al.31 There still exist different descriptions in details on the formation of Si3N4 nanowires prepared from different routes. Chen et al. explained the growth mechanism of rod-like β-Si3N4 crystals from the combustion synthesis by a synergy of VLS and Vapor–Solid (VS).32 Kim et al. found that the Si3N4 nanowires grown directly from silicon substrate resulted from a combination of solid–liquid–solid (SLS) and VLS.23 Yang et al. reported that the growth of plate-like and branched Si3N4 whiskers, obtained from the catalyst-assisted pyrolysis of polymeric precursors followed a solid–liquid–sas–solid (SLGS) mechanism.12,15,17 Lin et al. reported that the Si3N4 nanotubes prepared from a thermal heating CVD method were formed via the VLS mechanism.33 Zhang et al. prepared Si3N4 nanowires by heating Si or Si/SiO2 powder in N2 or NH3 atmosphere with or without catalysts and suggested that the growth followed the VS process.22 It is obvious that SiO vapor as the Si source of nanowire plays an important role in the growth of Si3N4 nanowires no matter what the growth mechanism