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Researchers help sort out the carbon nanotube problem
July 27, 2005National Institute of Standards and Technology (NIST) and university researchers report a significant step toward sorting out the nanotube "problem"-the challenge of overcoming processing obstacles so that the remarkable properties of the tiny cylindrical structures can be exploited in new polymer composite materials of exceptional strength.
As described in the current issue of Physical Review Letters,* their analysis reveals that, during mixing, carbon nanotubes suspended in viscous fluids can be encouraged to sort themselves by length. Achieving uniform sizes of nanotubes is one of several keys to producing affordable, high-quality polymer nanocomposites.
The team found that, under common processing conditions, shorter carbon nanotubes will flow toward the walls of mixing equipment, while the longer tubes tend to congregate in the interior.
Better understanding of factors that promote this self-sorting will point the way to process adjustments and devices that achieve desired arrangements of nanotubes during bulk manufacturing of polymer nanocomposites, says NIST's Erik Hobbie, leader of the collaboration, which included scientists from the University of Kentucky and Michigan Technical University.
Many times stronger than steel and possessing superlative thermal, optical and electronic properties, nanotubes have been called small-scale wonders, measuring a few nanometers in diameter and ranging greatly in length. Anticipated nanotube-based technologies range from hydrogen storage to transistors to space elevators. Nearest on the horizon are light-weight, high-strength carbon nanotube polymer structural composites.
With lasers, video microscopes and other optical monitoring equipment, the team tracked how nanotubes-both the single-wall and multiwall varieties-behave when suspended, at several different concentrations, in a polymer melt. They analyzed suspensions ranging in viscosity from syrup-like to watery under different mixing conditions.
The results did not suggest a "magic bullet" for getting nanotubes to align uniformly in the same direction-also critical to reliable processing of high-quality nanocomposites. But the finding that, under "modest flow conditions," carbon nanotubes will sort by length could point the way to practical methods for bulk separation of nanotubes according to size.
National Institute of Standards and Technology (NI
Better understanding of factors that promote this self-sorting will point the way to process adjustments and devices that achieve desired arrangements of nanotubes during bulk manufacturing of polymer nanocomposites, says NIST's Erik Hobbie, leader of the collaboration, which included scientists from the University of Kentucky and Michigan Technical University.
Many times stronger than steel and possessing superlative thermal, optical and electronic properties, nanotubes have been called small-scale wonders, measuring a few nanometers in diameter and ranging greatly in length. Anticipated nanotube-based technologies range from hydrogen storage to transistors to space elevators. Nearest on the horizon are light-weight, high-strength carbon nanotube polymer structural composites.
With lasers, video microscopes and other optical monitoring equipment, the team tracked how nanotubes-both the single-wall and multiwall varieties-behave when suspended, at several different concentrations, in a polymer melt. They analyzed suspensions ranging in viscosity from syrup-like to watery under different mixing conditions.
The results did not suggest a "magic bullet" for getting nanotubes to align uniformly in the same direction-also critical to reliable processing of high-quality nanocomposites. But the finding that, under "modest flow conditions," carbon nanotubes will sort by length could point the way to practical methods for bulk separation of nanotubes according to size.
National Institute of Standards and Technology (NI
Carbon Nanotubes Current Events and Carbon Nanotubes News RSSCaltech scientists develop DNA origami nanoscale breadboards for carbon nanotube circuits
In work that someday may lead to the development of novel types of nanoscale electronic devices, an interdisciplinary team of researchers at the California Institute of Technology (Caltech) has combined DNA's talent for self-assembly with the remarkable electronic properties of carbon nanotubes, thereby suggesting a solution to the long-standing problem of organizing carbon nanotubes into nanoscale electronic circuits.
Breakthrough in industrial-scale nanotube processing
Rice University scientists today unveiled a method for the industrial-scale processing of pure carbon-nanotube fibers that could lead to revolutionary advances in materials science, power distribution and nanoelectronics.
Next-generation microcapsules deliver 'chemicals on demand'
Scientists in California are reporting development of a new generation of the microcapsules used in carbon-free copy paper, in which capsules burst and release ink with pressure from a pen.
Study shows how carbon nanotubes can affect lining of the lungs
Carbon nanotubes are being considered for use in everything from sports equipment to medical applications, but a great deal remains unknown about whether these materials cause respiratory or other health problems.
Advance in 'nano-agriculture': Tiny stuff has huge effect on plant growth
With potential adverse health and environmental effects often in the news about nanotechnology, scientists in Arkansas are reporting that carbon nanotubes (CNTs) could have beneficial effects in agriculture.
A recipe for controlling carbon nanotubes
Nanoscopic tubes made of a lattice of carbon just a single atom deep hold promise for delivering medicines directly to a tumor, sensors so keen they detect the arrival or departure of a single electron, a replacement for costly platinum in fuel cells or as energy‐saving transistors and wires.
Friction force differences could offer a new means for sorting and assembling nanotubes
Nanotubes and nanowires are promising building blocks for future integrated nanoelectronic and photonic circuits, nanosensors, interconnects and electro-mechanical nanodevices. But some fundamental issues remain to be resolved - among them, how to position and manipulate the tiny tubes.
New biosensor can detect bacteria instantaneously
A research group from the Rovira i Virgili University (URV) in Tarragona has developed a biosensor that can immediately detect very low levels of Salmonella typhi, the bacteria that causes typhoid fever.
Researchers design new graphene-based, nano-material with magnetic properties
An international team of researchers has designed a new graphite-based, magnetic nano-material that acts as a semiconductor and could help material scientists create the next generation of electronic devices like microchips.
Researchers Pinpoint Neural Nanoblockers in Carbon Nanotubes
A team of Brown University scientists has pinpointed why carbon nanotubes tend to block a critical signaling pathway in neurons.
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