Abstract:
The work demonstrates fabrication of vertically aligned carbon nanotubes (CNT) composite
using thermal chemical vapor deposition (CVD). A forest of vertically aligned CNTs was
grown using catalytic CVD. Fluorocarbon polymer films were deposited in the spaces
between vertically aligned MWCNTs using thermal CVD apparatus developed in-house. The
excessive polymer top layer was etched by exposing the sample to water plasma. Uniform
distribution of monomodel vertically aligned CNTs embedded in the deposited polymer
matrix was observed in the micrograph, otherwise not possible using conventional techniques
such as spin coating.
The work also includes a simple technique for large scale horizontal and vertical alignment of
single wall carbon nanotubes (SWCNTs). These horizontal patterns are key arrangements
sought for fabrication of nanostructured materials. SWCNTs are purified and oxidized by
treating them with nitric acid at 120-122oC. The oxidized SWCNTs are further reacted with
octadecyl amine at the same temperature to attach the hydrophilic groups. These modified
SWCNTs are dissolved and sonicated in tetrahydrofuran solution. The resulting uniform
black color solution is filtered through 0.2 micro porous polytetraflouroethylene (PTFE)
using Buckner filter. Horizontal and vertical alignment was achieved when filtration was
performed under different conditions described in thesis. The contemporary alignment
techniques are tedious and need special facilities. The current method is relatively simple and
advantageously large quantities of CNTs can be aligned.
Infrared spectroscopy confirmed the attachment of functional groups to CNTs. Alignment of
CNTs, deposition of polymer and post etched specimens were analyzed by field emission
scanning electron microscope (FE-SEM). Preliminary diffusion experiments are revealing
and confirm the efficient deposition of polymer between the intertube gaps, as inferred from
the permeable pore density and associated diffusion parameters.
