Silicon Carbonitride Ceramics Produced by Pyrolysis of Polymer Ceramic Precursor

Two processing routes were explored to produce crack-free amorphous Si–N–C ceramics by pyrolysis of polyureasilazane ceramic precursor. Using a warm-pressing/ pyrolysis route, a ceramic body with certain amount of open porosity was produced; densification behavior during pyrolysis was examined. A prepyrolysis/binding/pyrolysis route was also developed. Ceramics formed using this route were characterized by higher density, lower volume shrinkage during consolidation, and larger viable material size. Open porosity was essentially absent in consolidated amorphous materials produced by this second route. Recrystallization of the consolidated amorphous ceramics resulted in a Si₃N₄/SiC nanocomposite with both silicon nitride and silicon carbide grains in the nanometric size range.