3. Results and discussion
The low-resolution transmission electron micrographs of the
graphene-carbon nanotube hybrid material are illustrated in Figure 1 for
the production of fiber-reinforced polymer composites. From a mechanical
point of view, carbon nanotubes exhibit excellent rigidity, comparable
to steel, while being extremely light. In addition, they exhibit
excellent electrical and thermal conductivity properties which make it
possible to envisage using them as additives to confer these properties
on various, particularly macromolecular, materials such as polyamides,
polycarbonate, polyesters, polystyrene, and polyethyleneimine, as well
as other thermoplastic and thermoset polymers. Carbon-based materials
are widely used due to their mechanical and chemical stability,
excellent intrinsic electrical conductivity, and large surface area.
Graphene-carbon nanotube multi-stack three-dimensional architectures can
overcome the limitations and restricted performance typically
encountered with carbon-based materials by using the combined strategies
of three-dimensional architecture and low-dimensional carbon
nanomaterial characteristics. Such graphene-carbon nanotube stacks have
one or more of the following characteristics: graphene and carbon
nanotubes are active materials that have unique electrical properties,
particularly high surface area and high electrical conductivity, the
carbon nanotube array of the graphene- carbon nanotube stack acts as a
spacer to prevent graphene self-aggregation, maintaining a large active
surface area, and stable electrical and mechanical contact is generated
between carbon nanotube and graphene due to the direct growth of carbon
nanotube between the graphene layers. A graphene-carbon nanotube stack
may be fabricated by sequentially developing a stack of alternating
graphene and catalytic metal layers, breaking down the metal layers into
catalytic nanoparticles, and causing the simultaneous growth of the
carbon nanotube between the graphene layers at the sites of the
catalytic nanoparticles and the expansion of the graphene-carbon
nanotube stack. The growth tube furnace chemical vapor deposition method
is adapted to grow graphene. Graphene synthesis begins when the carbon
feedstock is introduced into the furnace tube, where it thermally
decomposes into carbon and hydrogen radicals in the presence of the
catalyst. In the case of copper, growth is limited to the surface of the
metal. The dissociated carbon species diffuse across the surface of the
metal, where they nucleate as seeds which grow and coalesce to form a
continuous graphene film.