Deposition of SiC/Si coatings in a microwave plasma-assisted spouted bed reactor

Silicon carbide (SiC) layers were deposited onto alumina particles in a microwave plasma-assisted spouted bed reactor using methyltrichlorosilane (MTS) and hydrogen mixtures, in argon, as precursor gas feed. The operating parameters studied were enthalpy, gas composition, and pressure. Microwaves were guided from a generator, operating at 2.45 GHz, along a rectangular waveguide intersecting a quartz tube, acting as the reaction zone. A graphite nozzle at the bottom of the tube facilitated the spouting action. Growth rates varied from 50 to 140 mu m/h. Overall results indicate that the optimal region for SiC deposition requires relatively high enthalpy (similar to 5 MJ/kg) and pressure ( > -60 kPa) conditions, with hydrogen-to-MTS ratios similar to 5:1. The quality (i.e. crystallinity, particle size, Si/C ratios) of the layers improve at these conditions, at the cost of decreased deposition rates. Characterisation was done by XRD, FTIR, XPS, SEM, TEM and EDX, which assisted in developing colour and morphological charts to indicate the changes as a function of changing operating parameters. A microwave plasma spouted bed reactor is demonstrated to be a viable alternative technique for SiC layer deposition onto microspheres.