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July 20, 2006

Better mixing of nanotubes in polymers will make better nanomaterials

The amount of force applied while mixing carbon nanotube suspensions influences the way the tiny cylinders ultimately disperse and orient themselves. In turn, the final arrangement of the nanotubes largely dictates the properties of the resultant materials.

In an elegantly simple result, NIST researchers Erik Hobbie and Dan Fry found that networks of carbon nanotubes respond predictably to externally applied force. The networks also showed behavior reminiscent of more conventional materials that align spontaneously under the forces of Brownian motion--the random motion of particles in a fluid famously described mathematically by Einstein.

The response was so predictable that the scientists mapped out the relationship in the form of a phase diagram, the materials science equivalent of a recipe. Using their "phase diagram of sticky nanotube suspensions," other researchers can estimate the order that will result when applying a certain amount of force when mixing a polymer fluid with a particular concentration of nanotubes. The recipe can be used to prevent entanglement and to help achieve the nanotube arrangement and orientation associated with a desired set of properties.

This is a recipe for better nanotube/polymer composites.

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