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

Abstract

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.

Understanding the mechanical reinforcement of uniformly dispersed multiwalled carbon nanotubes in alumino-borosilicate glass ceramic

“…The slightly lower sintered densities of the MWCNT-containing ABS glass ceramics may be partly responsible for this lowering of hardness. Such reductions in hardness on the incorporation of CNTs in inorganic matrices have also been observed by others [11,15,28,29]. Fig.…”

Multifunctional Composites of Ceramics and Single‐Walled Carbon Nanotubes

“…The evidence presented thus far ( Fig. 3C and D) [24,30] points to this hypothesis. With further crack propagation, eventually the SWNTs bridges far behind the crack tip will pullout or detach from the grain boundaries and/or fail.…”

“…This debate is further compounded by the fact that most researchers use the simple indentation test [2] to measure the toughness, which may not be a valid test in the case of these composites. [21,31,32] Independent, more difficult toughness tests (not based on indentation) show either no toughening, [21] significant toughening (two-fold increase over unreinforced ceramic), [24] or inconclusive results, [30] albeit in different composites. In light of the conflicting toughening results in ceramic/SWNTs composites, it is argued that the time has come to rethink the role of SWNTs in reinforcing ceramics.…”

“…More recently, bundles of single-walled carbon nanotubes (SWNTs), which are of higher quality and are purer compared to MWNTs, have been used to reinforce ceramics. [20][21][22][23][24][25][26][27][28][29][30] Although there is some debate regarding the toughening in these composites, [21,31,32] new insights into the toughening mechanisms are starting to emerge. It is argued that exploiting these mechanisms may lead to ceramic/SWNTs composites that are both tough and strong.…”

Biocompatibility and Bone Tissue Compatibility of Alumina Ceramics Reinforced with Carbon Nanotubes

“…We have studied the use of CNTs as reinforcements in alumina ceramic products that have been clinically applied in various fields as biomaterials. Reported improvements in the mechanical properties of CNT/alumina composites can be found in the literature [18,[29][30][31][32][33][34][35]. These studies showed only small improvement of strength, however, owing to the formation of microstructures that occurs when CNTs are dispersed homogeneously in the ceramic matrix.…”