Researchers help sort out the carbon nanotube problem
National 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.
Small- angle neutron scattering pattern provides an inverted representation of how carbon nanotubes flowing in a polymer melt sort themselves by length. Longer nanotubes, which scatter neutrons at lower angles, gather in purple regions, while medium-sized and short nanotubes are indicated by red and yellow, respectively. The dark blue circle in the center of the image is the beam stop, which protects the sensitive detector from the transmitted beam of unscattered neutrons.
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 NISTs 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.
Mark Bello | EurekAlert!
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Mapping the interaction of a single atom with a single photon may inform design of quantum devices
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...