LASER SYNTHESIS AND CRYSTALLIZATION OF NANOCOMPOSITE SI C/N POWDER/

Ultrafine preceramic Si/C/N composite powders have been prepared from hexamethyldisilazane (HMDS) by laser-induced gas phase reaction, using a new kind of two-reaction-zone reactor which could efficiently incre ase laser efficiency and production yield compared with a one-reaction -zone reactor. The as-formed products were nanosized (50-80 nm), amorp hous powders containing Si-C and Si-N bonds homogeneously mixed with s ome excess carbon. The production yield was in the range of 88-120 g/h . Changes of chemical composition and crystallization of the powders d uring heat treatment at 1350 and 1550 degrees C under nitrogen for 1 h were studied.