CARS DIAGNOSTICS OF A CO2-LASER PYROLYTIC EXPERIMENT FOR THE PRODUCTION OF NANOSIZED CERAMIC POWDERS

Spatial distributions of rotational temperatures and molecular number densities of C2H2 and H-2 were measured with CARS during the productio n of ultrafine SiC powders in a laser pyrolytic process flame. By mean s of a CO2 laser, the reaction gases SiH4 and C2H2 (or alternatively C 2H4) are converted into SiC and H-2. From the CARS measurements temper ature gradients are determined between 8.8 x 10(5) K/m and 1.6 x 10(6) K/m with corresponding heating rates of 1.8 x 10(6) K/s and 1.3 x 10( 6) K/s. The CARS data also allow an estimation of the gas expansion be haviour in the reaction zone. Moreover, they show that diffusive veloc ity components of the hydrogen in the hot reaction zone do not exceed 0.4 m/s.