Buckypaper

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Buckypaper is a thin sheet made from an aggregate of carbon nanotubes. Originally, it was fabricated as a way to handle carbon nanotubes, but it is currently being studied and developed into applications by several research groups, showing promise as a building material for aerospace vehicles, body armor and next-generation electronics and displays.

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[edit] Background

Buckypaper is a macroscopic aggregate of carbon nanotubes, or "buckytubes". It owes its name to buckminsterfullerene, the 60 carbon fullerene (an allotrope of carbon with similar bonding that is sometimes referred to as a "Buckyball" in honor of R. Buckminster Fuller). Richard Smalley, Sir Harold Kroto and Robert Curl shared the 1996 Nobel Prize in Chemistry for their discovery of buckminsterfullerene. Their discoveries and subsequent work with carbon nanotubes led to a revolution in the fields of chemistry and materials science.

[edit] Synthesis

The generally accepted method for forming such CNT films involves the use of non-ionic surfactants, such as Triton X-100 [1] and Sodium lauryl sulfate [2], which improves their dispersibility in aqueous solution. These suspensions can then be membrane filtered under negative or positive pressure to yield uniform films [3]. The Van der Waals forces 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 [4].

In order to avoid adverse side-effects from the possible presence of surfactants, an alternative casting process was developed involving a frit-compression method that did not require the use of surfactants or surface modification[5]. The dimensions can be controlled through the size of the syringe housing and the through the mass of carbon nanotubes added. Their thicknesses are typically much larger than surfactant-cast buckypaper and have been synthesised 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. Beyond 5mm thickness, the samples are termed buckycolumns. The frit compression method allows rapid casting of buckypaper, buckydiscs and buckycolumns with recovery of the casting solvent.

Aligned growth of MWCNTs has been used in CNT film synthesis through the domino effect[6]. Forests of MWCNTS are pushed flat in a single direction, compressing the vertical orientation into the horizontal plane, leading to high-purity buckypaper with no further purification or treatment required. By comparison, when a buckypaper sample was formed from the 1 tonne compression of chemical vapour deposition (CVD) generated MWCNT powder, any application of a solvent led to the immediate swelling of the film till it reverted into particulate matter[7]. 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.

[edit] Applications

Among the possible uses for buckypaper that are being researched:

  • 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 (CRT) and liquid crystal display (LCD) technology.
  • Since 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.
  • Because carbon nanotubes have an unusually high current-carrying capacity, a buckypaper film could be applied to the exteriors of airplanes. Lightning strikes then could flow around the plane and dissipate without causing damage.
  • 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.

[edit] References

  1. ^ Panhuis MIH, Salvador-Morales C, Franklin E, Chambers G, Fonseca A and Nagy JB, et al. "Characterization of an interaction between functionalized carbon nanotubes and an enzyme". J Nanosci Nanotechno 2003;3(3):209-13
  2. ^ Sun J and Gao L. "Development of a dispersion process for carbon nanotubes in ceramic matrix by heterocoagulation". Carbon 2003;41(5):1063-68
  3. ^ Vohrer U, Kolaric I, Haque MH, Roth S and Detlaff-Weglikowska U. "Carbon nanotube sheets for the use as artificial muscles". Carbon 2004;42(5-6):1159-64
  4. ^ Cornett JB and Shockman GD. "Cellular lysis of Streptococcus faecalis induced with Triton X-100". J Bacteriol 1978;135(1):153–60
  5. ^ Whitby RLD, Fukuda T, Maekawa T, James SL, Mikhalovsky SV, "Geometric control and tuneable pore size distribution of buckypaper and buckydiscs". Carbon 2008;46(6):949-956
  6. ^ Wang D, Song PC, Liu CH, Wu W, Fan SS, "Highly oriented carbon nanotube papers made of aligned carbon nanotubes". Nanotechnology 2008;19:7.
  7. ^ Whitby RLD, From carbon nanotubes to buckycolumns, 5th International Symposium on Bioscience and Nanotechnology, Kawagoe, Japan, November 2007

[edit] See also

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