Synthesis of Si(N,C) nanostructured powders from an organometallic aerosol using a hot-wall reactor

Abstract

Current studies show that nanostructured Si(N,C) powders are readily synthesized by rapid condensation of a pyrolytically decomposed silazane precursor, namely [CH3SiHNH]n,n−3 or 4. Basically, the process involves ultrasonic conversion of the liquid-phase precursor to an aerosol, followed by thermal decomposition in a hot reactor. This was followed by the rapid condensation of the gaseous product exiting the reactor, to form ceramic particles of nanoscale dimension. Thermal decomposition was performed at a temperature of 1000 °C, near ambient pressure with a flow rate of ∼ 150 standard cm3 min−1 for NH3. One critical feature examined in this process was the rapidity of the powder synthesis, in a reaction which involves (i) elimination of ligand groups, (ii) formation of ceramic species, and (iii) condensation of ceramic species into ultrafine ceramic particles. These features have been studied using Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray photo-electron and nuclear magnetic resonance spectroscopies. Additionally, a model is formulated to determine the effect of process parameters on particle size.