Spark plasma sintering: A powerful tool to develop new silicon nitride-based materials

Several key topics on the current assisted sintering of Si3N4-based materials are reviewed. First, different proposed mechanisms for spark plasma sintered (SPSed) ceramics are presented, discussing the electric field effect on the liquid phase behaviour and how it may influence the liquid phase sintering of Si3N4 ceramics. Next, we show that the SPS is a powerful tool to develop new Si3N4-based materials with tailored microstructures, such as functionally graded materials (FGMs) and carbon nanotubes (CNTs) containing Si3N4 matrix composites. Si3N4 FGMs are fabricated from a sole homogenous Si3N4 mixture just modifying the SPS system punches set-up, thus creating a temperature gradient through the specimen. Finally, the capability of SPS to get dense Si3N4/CNTs composites overcoming both constraint densification and nanotubes degradation is proved.