Engineered Nanostructures for Multifunctional Single‐Walled Carbon Nanotube Reinforced Silicon Nitride Nanocomposites

Colloidal processing was used to make highly dispersed aqueous composite suspensions containing single-wall carbon nanotubes (SWNTs) and Si3N4 particles. The SWNTs and Si3N4 particles were stabilized into composite suspensions using a cationic surfactant at low pH values. Bulk nanocomposites containing 1.0, 2.0, and 6.0 vol% SWNTs were successfully fabricated using rapid prototyping. The survival of SWNTs was detected, using Raman spectroscopy, after high-temperature sintering, up to 1800°C. The nanocomposites have densities up to 97% of the composite theoretical density. The engineered nanostructures reveal an increase in grindability and damage tolerance behavior over the monolithic ceramic. We also observed toughening mechanisms such as SWNT crack bridging and pull-out, indicating that SWNTs have the potential to serve as toughening agents in ceramics. Increased fracture toughness values over the monolithic Si3N4 were observed for the 2.0-vol% SWNT–Si3N4 nanocomposite when a given sintered microstructure was present. We report here the effects of colloidal processing on mechanical behavior of SWNT reinforced nonoxide ceramic nanocomposites.