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


  • N. Padture—contributing editor

  • Based in part on the dissertation submitted by E. L. Corral for a Ph.D. in Materials Science, at Rice University, Houston, TX, 2005.
    This work has been financially supported by The Robert Welch Foundation of Texas Grant number C1494, the NSF-AGEP at Rice University grant number HRD-9817555, Carbon Nanotechnologies Inc., NASA-URETI grant number NC-01-0203 and NASA Ames Research Center grant number NNA04CK63A. The research at the High Temperature Materials Laboratory (HTML) was sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, as part of the HTML User Program, Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract number DE-AC05-00OR22725.

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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.