Carbon nanoparticles occur in five different
basic forms: diamond, graphite, fullerenes, nanotubes and nanocones.
The research activity on nanocarbon within COMPLEX is focussed on the
last two, nanotubes and nanocones, which are of most interest for new
technological applications. In addition to these basic forms,
nanocarbon also occurs in less geometrically perfect forms such as
amorphous nanoparticles, nanohorns and helical structured particles.
Carbon nanotubes
The
properties of nanotubes are truly remarkable as a result of their
unusual structure. A carbon nanotube is composed of tubular graphitic
sheets having a diameter of molecular dimensions but lengths that can
be in the micrometer range. As such it belongs to a nanoworld where the
strange effects of quantum physics reign. Consequently carbon nanotubes
possess both unique electrical and mechanical properties.
Mechanical properties: The tensile as well as the compressive
strengths are enormous and the tube can be sharply bent without
breaking. However, to obtain the optimal mechanical properties, the
nanotubes must be made in an arc which yields nanotubes with nearly
perfect structure, akin to single crystals.
Molecular size electronic devices: Nanotubes conduct electricity, either like a
metal or like a semiconductor, depending on how the carbon rings are
aligned along the axis of the tube, and are as such suitable for making
extremely small electronic devices.
New tools in chemistry: Nanotubes with a defined diameter can be used
for separation and storage of biologically active materials, separation
and storage of gases etc.
COMPLEX collaborates with the company n-TEC AS
which is located at IFE, Kjeller and which has the objective to develop
and mass-produce arc-grown carbon nanotubes. Through this reseach effort, the nanotubes
propereties are characterized and new applications are developed.
Carbon cones
In 1997 it was found by T. Ebbesen and
coworkers that carbon cones could be produced in industrial quantities
in the so-called Kvaerner Carbon Black & Hydrogen Process.
Briefly, the material is composed of microstructures, which are flat
discs, or cones. Cones make up about 20% of the material; the rest is
mainly discs. The cones are typically 0.5 - 1.0 micrometer long, but
the sizes are dependent on parameters of the process and smaller or
larger sizes can presumably be produced by appropriate control of the
process. Besides disks, there are five
possible ideal cones.
The carbon cones have a perfect conical
structure with symmetry fundamentally different from other known carbon
materials, including nanotubes and Buckyballs. This will very likely result in unprecedented
electronic-, chemical- and mechanical properties and open up unique
applications in various areas
Preliminary experiments also indicate storage
capacity for hydrogen gas in carbon cones and this application has been
patented by IFE. The large hydrogen uptake in carbon cones is
certainly not due to physisorption or chemisorption, as is the case for
other carbon materials. Possible physical mechanisms behind this
relatively high hydrogen uptake is now being investigated in extensive
theoretical work and computer modelling.
