Structural development and properties of Si3N4-SiC composites from amorphous Si-C-N powder precursors
Strukturelle Entwicklung und Eigenschaften von Si3N4-SiC-Verbundstoffen aus amorphen pulvrigen Si-C-N-Precursor
The aim of this work is to develop Si3N4-SiC nanocomposites with high mechanical properties using amorphous siliconcarbonitride powders pyrolyzed by gasphase pyrolysis of hexamethyldisilazane precursors. Mixtures of commercial alpha-Si3N4 with up to 43 weight-% 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 % theoretical density. Structural analysis performed by scanning electron microscopy shows that the siliconcarbide particles finer than 50 nm were distributed both inside the silicon nitride grains and on the grain boundaries. Mechanical properties of these materials correlate with their microstructure.