Abstract
In relation to the synthesis of the reinforced ceramic matrix composites, the pyrolysis mechanism of Si-C-O fiber (Nicalon NL200) in Si3N4 powder was studied by TG, XRD and tensile test. At lower temperatures, the pyrolytic rates were unaffected by the presence of Si3N4 powder. The pyrolysis proceeded much more slowly in N2 than in Ar. The pyrolysis was controlled by either the growth of $-SiC crystallites (in Ar) or the diffusion of the pyrolytic gases (SiO and CO) through the nitrided case of Nicalon (in N2). At higher temperatures, the packing of Si3N4 powder retarded the pyrolysis in both Ar and N2. The rate-determining step is considered to be the gaseous diffusion through the interparticle pores within the powder.
