SYNTHESIS OF SI(C, N) NANOPARTICLES BY RAPID LASER POLYCONDENSATION CROSS-LINKING REACTIONS OF AN ORGANOSILAZANE PRECURSOR

A study has been made of basic mechanisms involved in the rapid synthesis of pre-ceramic and ceramic nanoparticle powders. In this process an aerosol, formed from an ultrasonically atomized liquid organosilazane monomer, [CH3SiHNH]n, is injected into the beam of an industrial CW CO2 laser. One critical feature examined was the rapid condensation of molecular species from the laser plume, in a process involving three-dimensional crosslinking polycondensation reactions. In accompanying studies, a model has been formulated to determine the laser plume temperature, the cooling rate of condensing species and the particle diameter. These are obtained by analyical solution of heat conduction, momentum and mass conservation equations that consider heat loss by gas conduction, radiation, evaporation and convection.