Application of carbon nanotubes to silicon nitride matrix reinforcements

A conventional (hot isostatic pressing) and a novel sintering method (spark plasma sintering) have been applied to perform multiwall carbon nanotube (MWNT) reinforced silicon nitride composites. Morphological, structural, compositional investigations, as well as mechanical characterization have been performed. The first results show that carbon nanotubes have been preserved in composite structure during these two high-temperature processes. Carbon nanotubes have been found to have good adherence to the silicon nitride grains as observed for both processing methods. Moreover, carbon nanotubes may serve as crystallization sites and seeds for silicon nitride grain growth. Significant differences have been found between composites prepared by these two sintering techniques. Well-densified composites with nanocrystalline structure and with improved mechanical characteristics have been obtained by spark plasma sintering. The conventional sintering resulted in partially densified composites with coarser grain structure.