Particle morphology of various SiC-based nanocomposite powders made by the aerosol-assisted synthesis method

Herein, we present a part of a study on the preparation of SiC-based composite nanopowders by the two-stage Aerosol-Assisted Vapor Phase Synthesis (AAVS) method from organosilicon precursors (neat hexamethyldisiloxane, neat tetramethoxysilane, ethanol solutions of polydimethylsiloxane). Upon generation, liquid aerosol droplets were transported in a stream of argon through a ceramic reactor tube maintained at 1200 degrees C. The resulting solid by-products were collected on a nylon filter as bulk powders. Each raw powder was, subsequently, pyrolyzed in a furnace reactor heated to 1650 degrees C under a flow of argon. After the final pyrolysis at 1650 degrees C, mostly nanocrystalline silicon carbide powder with small quantities of free excess carbon was obtained from the neat hexamethyldisiloxane system, composite powder of not fully converted silica and SiC was prepared from the neat tetramethoxysilane system, and C-rich/SiC composite was made from the ethanol/polydimethylsiloxane solution system. The prevailing phase of the SiC component was the regular beta-SiC polytype. Most of the powders were composed of spheroidal particles--morphology imprinted during aerosol generation at 1200 degrees C and not much affected by the second-stage bulk pyrolysis at 1650 degrees C. The specifics of spheroidal morphology were characteristic of the applied precursor system.