Structural Development and Properties of Si_3N_4-SiC Composites From Amorphous Si-C-N Powder Precursors

摘要

The aim of this work is to develop Si_3N_4-SiC nanocomposites with high mechanical properties using amorphous siliconcarbonitride powders pyrolyzed by gasphase pyrolysis of hexamethyldisilazane precursors. Mixtures of commercial alpha-Si_3N_4 with up to 43 wt.- percent Si C-N-powder and small amount sintering additive were used as starting materials. Hot pressing of these mixtures at temperatures above 1800 deg C resulted in compacts with densities higher than 99 percent theoretical density. Structural analysis performed by scanning electron microscopy shows that the siliconcarbide particles finer than 50 nm were distributed both inside the silcon nitride grains and on the grain boundaries. Mechanical properties of these materials corelate with their microstructure.