Buckypaper is a thin sheet made from an aggregate of carbon nanotubes or carbon
nanotube grid paper. The nanotubes are approximately 50,000 times thinner than
a human hair. Originally, it was fabricated as a way to handle carbon
nanotubes, but it is also being studied and developed into applications by
several research groups, showing promise as vehicle armor, personal armor, and
next-generation electronics and displays.
Background Buckypaper is a macroscopic aggregate of
carbon nanotubes, or "buckytubes". It owes its name to the
buckminsterfullerene, the 60 carbon fullerene.
Synthesis The generally accepted methods of making
CNT films involves the use of non-ionic surfactants, such as Triton X-100 and
sodium lauryl sulfate, which improves their dispersibility in aqueous
solution. These suspensions can then be membrane filtered under positive or
negative pressure to yield uniform films. The van der Waals force's
interaction between the nanotube surface and the surfactant can often be
mechanically strong and quite stable and therefore there are no assurances that
all the surfactant is removed from the CNT film after formation. Washing with
methanol, an effective solvent in the removal of Triton X, was found to cause
cracking and deformation of the film. It has also been found that Triton X can
lead to cell lysis and in turn tissue inflammatory responses even at low
concentrations. In order to avoid adverse side-effects
from the possible presence of surfactants, an alternative casting
process can be used involving a frit compression method that did not require
the use of surfactants or surface modification. The dimensions can be
controlled through the size of the syringe housing and through the mass of
carbon nanotubes added. Their thicknesses are typically much larger
than surfactant-cast buckypaper and have been synthesized from 120 μm up to 650
μm; whilst no nomenclature system exists to govern thicknesses for samples to be
classified as paper, samples with thicknesses greater than 500 μm are
referred to as buckydiscs. The frit compression method allows rapid casting
of buckypaper and buckydiscs with recovery of the casting solvent and
control over the 2D and 3D geometry. Aligned multi-walled carbon nanotube
growth has been used in CNT film synthesis through the domino effect. In
this process, "forests" of MWNTs are pushed flat in a single direction,
compressing their vertical orientation into the horizontal plane, which results
in the formation of high-purity buckypaper with no further purification
or treatment required. By comparison, when a buckypaper sample was formed from
the 1 ton compression of chemical vapor deposition generated MWNT powder, any
application of a solvent led to the immediate swelling of the film till it
reverted into particulate matter. It appears that for the CNT powder used,
compression alone was insufficient to generate robust buckypaper and
highlights that the aligned growth methodology generates in situ tube-tube
interactions not found in CVD CNT powder and are preserved through to the domino
pushing formation of buckypaper. Properties
Buckypaper is one tenth the weight yet potentially 500 times stronger than
steel when its sheets are stacked to form a composite. It could disperse heat
like brass or steel and it could conduct electricity like copper or silicon. Rice
University scientist Wade Adams says, "All those things are what a lot of
people in nanotechnology have been working toward as sort of Holy Grails."
Applications Among the possible uses for buckypaper
that are being researched: Fire protection: covering material with
a thin layer of buckypaper significantly improves its fire resistance due to the
efficient reflection of heat by the dense, compact layer of carbon nanotubes
or carbon fibers. If exposed to an electric charge,
buckypaper could be used to illuminate computer and television screens. It
could be more energy-efficient, lighter, and could allow for a more uniform level
of brightness than current cathode ray tube and liquid crystal display
technology. Since individual carbon nanotubes are
one of the most thermally conductive materials known, buckypaper lends itself
to the development of heat sinks that would allow computers and other
electronic equipment to disperse heat more efficiently than is currently
possible. This, in turn, could lead to even greater advances in electronic
miniaturization. Films also could protect electronic
circuits and devices within airplanes from electromagnetic interference, which
can damage equipment and alter settings. Similarly, such films could allow
military aircraft to shield their electromagnetic "signatures", which can
be detected via radar. Buckypaper could act as a filter
membrane to trap microparticles in air or fluid. Because the nanotubes in
buckypaper are insoluble and can be functionalized with a variety of
functional groups, they can selectively remove compounds or can act as a sensor.
Produced in high enough quantities and at an economically viable price,
buckypaper composites could serve as an effective armor plating.
Buckypaper can be used to grow biological tissue, such as nerve cells.
Buckypaper can be electrified or functionalized to encourage growth of
specific types of cells. The Poisson's ratio for carbon nanotube
buckypaper can be controlled and has exhibited auxetic behavior, capable of
use as artificial muscles. See also
Frit compression Carbon nanotube
Graphene oxide paper Potential applications of carbon
nanotubes Graphene
References External links
FSU researcher's "buckypaper" is stronger than steel at a fraction of the
weight Research in Reviews: buckypaper
Buckypaper – Nanotubes on Steroids; Pictures of buckypaper and an interview
with Frank Allen, Operations Director of the High-Performance Materials Institute
at Florida State University