Catalyst-free growth of SiC nanowires in a porous graphite substrate by low pressure chemical vapor infiltration

SiC nanowires were synthesized from CH₃SiCl₃ (MTS)-H₂-Ar precursor system by low pressure chemical vapor infiltration (LPCVI) in a porous graphite substrate without using a catalyst. TEM showed SiC nanowires were β-SiC, and no bulk structure at the top end of the nanowires was observed, which indicated SiC nanowires growth via the vapor/solid (VS) mechanism. SEM results revealed SiC nanowires grew in clusters and curved. The average diameter of SiC nanowires changed from 190 to 185 nm when varying the temperature from 900 to 1100 °C with a fixed gas ratio α (α=(H₂+Ar)/MTS). Additionally, a minimum average diameter of 100 nm was obtained at the temperature of 1000 °C. At a constant temperature of 1000 °C, changing α from 35 to 75 increased the nanowires' average diameter from 100 to 470 nm. The growth mechanism could be construed by the model that the gas phase nucleated first and grew continuously along both axial and radial directions subsequently.