Spark plasma sintering of Si₃N₄/C composites

Si₃N₄/C composites were prepared with carbon black and α-Si₃N₄ powder by a novel sintering method, i. e. spark plasma sintering. SiC particles formed through reactions between the carbon particles and the SiO₂ on the Si₃N₄ surface. The samples were sintered at 1650 °C for 5 minutes in a nitrogen atmosphere. The microstructure, phase composition, mechanical properties, and dielectric properties of the composites were investigated. The relative densities of the C/Si₃N₄ composites decreased from 99 to 85% when the carbon black content increased from 0 to 20 wt.-%. Bending strength, hardness and dielectric properties were found to be influenced by the amount of carbon black introduced into the silicon nitride matrix.