NIST releases first certified reference material for single-wall carbon nanotubes
24 Dec 2011
The National Institute of Standards and Technology (NIST) has issued the world's first reference material for single-wall carbon nanotube soot. Distantly related to the soot in your fireplace or in a candle flame, nanotube-laden soot is the primary industrial source of single-wall carbon nanotubes, perhaps the archetype of all nanoscale materials.
 |
| Scanning electron microscope image of a typical sample of the NIST single-wall carbon nanotube soot standard reference material. The nanotubes tend to stick together and form smaller and larger bundles. Some of the impurities also are visible. The image shows an area just over a micrometer wide. (Color added for clarity.) Credit: Vladar, NIST |
The new NIST material offers companies and researchers a badly needed source of uniform and well-characterized carbon nanotube soot for material comparisons, as well as chemical and toxicity analysis.
With walls of carbon only one atom thick and looking like a sheet of chicken wire curled into a cylinder, single-wall carbon nanotubes are one of several families of pure carbon materials that, because of their nanoscale size, have special properties.
''Single-wall carbon nanotubes,'' says NIST chemical engineer c, ''have exquisite optical, mechanical, thermal and electronic properties, and because of their small width but long lengths - think of something like a long piece of hair but 10,000 times thinner - full development of these materials should enable lighter, stronger materials, as well as improve many technologies from sensors to electronics and batteries.''
Unfortunately, nanotubes are difficult to produce without significant impurities or in large quantities. Single-wall nanotubes, in particular, have been notorious for their relatively low quality and batch-to-batch variability.
They typically are produced in complex processes using small particles of metal catalysts that promote the growth of the nanotubes. The resulting material - often a powder not unlike the soot you would find in your fireplace - has frequently contained large amounts of impurities, such as other forms of carbon, and sometimes significant levels of catalysts.
