Polymer-based composites with added nano-scale fillers have been widely investigated in recent years since they can be tailored by tuning the functionality of each component to exhibit novel or improved properties compared to conventional composites. Nanocomposites are being considered for applications in many areas that range from very hard protective coatings and super-strong fibers to thin film transistors, light-emitting diodes and solar cells. In this project, we will focus on a novel nanocomposite material based on the combination of carbon nanotubes and silica nanoparticles. Nanocomposites with improved electrical and mechanical properties are finding increasing number of commercial applications in many fields (structural composites, electronics, automotive, space and aeronautics, coatings, etc.). However, to become adopted commercially, any new filler must exhibit significant performance-cost benefits compared to existing fillers. This project aims at the development of a novel carbon nanotube-silica hybrid in which nanoparticles of silica are connected to very thin bundles of single-walled carbon nanotubes (SWNT). SWNT have extraordinary electrical and mechanical properties. However, these properties cannot be easily transferred to the matrix of a composite due to the impossibility of dispersing them homogeneously and chemically anchoring them. By tuning the surface chemistry of the silica as well as the nanotube length and diameter, we anticipate that this hybrid will exhibit great advantages in dispersion, conductivity, affinity to polymeric matrices, and cost compared to any other composite filler.
The role of water in carbon feed on the surface-guided growth of horizontally aligned single-walled carbon
nanotubes (HA-SWCNTs) was investigated. It is shown that the amount of water can be optimized to favor HA-SWCNT growth, which is proposed to be due to selective etching of carbon deposits at carbon–metal interface. Without water, nanotube–nanotube interaction and carbon accumulation at the interface are disproportionately large compared to the rate of nanotube growth, leading to catalyst deactivation. With excess water, suppression of nanotube growth occurs, resulting in reduced carbon yield on the surface.
Intermediate carbon/water feed ratios achieve cleaner growth with high efficiency.