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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 RSSPaperwork: Buckypapers clarify electrical, optical behavior of nanotubes
Using highly uniform samples of carbon nanotubes-sorted by centrifuge for length-materials scientists at the National Institute of Standards and Technology (NIST) have made some of the most precise measurements yet of the concentrations at which delicate mats of nanotubes become transparent, conducting sheets.
As Sticky as a Gecko ... but Ten Times Stronger!
The gecko's amazing ability to stick to surfaces and walk up walls has inspired many researchers to manufacture materials that mimic the special surface of a gecko's foot.
Simulations help explain fast water transport in nanotubes
By discovering the physical mechanism behind the rapid transport of water in carbon nanotubes, scientists at the University of Illinois have moved a step closer to ultra-efficient, next-generation nanofluidic devices for drug delivery, water purification and nano-manufacturing.
Coating improves electrical stimulation therapy used for Parkinson's, depression, chronic pain
Researchers at UT Southwestern Medical Center have designed a way to improve electrical stimulation of nerves by outfitting electrodes with the latest in chemically engineered fashion: a coating of basic black, formed from carbon nanotubes.
True properties of carbon nanotubes measured
For more than 15 years, carbon nanotubes (CNTs) have been the flagship material of nanotechnology. Researchers have conceived applications for nanotubes ranging from microelectronic devices to cancer therapy. Their atomic structure should, in theory, give them mechanical and electrical properties far superior to most common materials.
Slipping through cell walls, nanotubes deliver high-potency punch to cancer tumors in mice
The problem with using a shotgun to kill a housefly is that even if you get the pest, you'll likely do a lot of damage to your home in the process. Hence the value of the more surgical flyswatter.
Golden Scales: Nanoscale Mass Sensor from Berkeley Can Be Used to Weigh Individual Atoms and Molecules
There's a new "gold standard" in the sensitivity of weighing scales. Using the same technology with which they created the world's first fully functional nanotube radio, researchers with Berkeley Lab and the University of California (UC) at Berkeley have fashioned a nanoelectromechanical system (NEMS) that can function as a scale sensitive enough to measure the mass of a single atom of gold.
'Nanonet' circuits closer to making flexible electronics reality
Researchers have overcome a major obstacle in producing transistors from networks of carbon nanotubes, a technology that could make it possible to print circuits on plastic sheets for applications including flexible displays and an electronic skin to cover an entire aircraft to monitor crack formation.
LLNL researchers peer into water in carbon nanotubes
Researchers have identified a signature for water inside single-walled carbon nanotubes, helping them understand how water is structured and how it moves within these tiny channels.
The fight for the best quantum bit (qubit)
Our results give us, for the first time, the possibility to understand the interaction between just two electrons placed next to each other in a carbon nanotube.
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