Computer model predicts nanotube breaks

Mar 28, 2006

In theory, carbon nanotubes are 100 times stronger than steel, but in practice, scientists have struggled make nanotubes that live up to those predictions, in part, because there are still many unanswered questions about how nanotubes break and under what conditions.

Because nanotubes are single molecules - about 80,000 times smaller than a human hair - finding out what makes them break involves the study of molecular bonds, atomic dynamics and complex quantum phenomena. The fact that there are hundreds of different kinds of nanotubes, sometimes with radically different properties, adds to the complexity.

A new computer modeling approach developed by materials scientists at Rice University and the University of Minnesota is allowing researchers to create a "strength map" that plots the likelihood or probability that a nanotube will break - and how it's likely to break - based on four key variables.

"Nanotubes break in one of two ways: the bonds either snap in a brittle fashion or they stretch and deform," said Boris Yakobson, professor of mechanical engineering and materials science and of chemistry. "We found that the underlying mechanisms that cause both types of breaks are each present at the same time. Even in a particular test, either type of break can occur, but we were able to map out a pattern - based on statistical probabilities - of what was likely to occur in a range of conditions for the whole catalog of nanotube species."

Yakobson's results appear in this week's online edition of the Proceedings of the National Adacemy of Sciences.

Carbon nanotubes are single molecules of pure carbon. They are long, narrow, hollow cylinders with walls just one atom thick. Scientists estimate SWNTs are about 100 times stronger than steel at one-sixth the weight. By comparison, Kevlar® -- the fiber used in most bulletproof body armor -- is about five times stronger than an equal weight of steel.

The precise diameter of a nanotube can vary from less than half of a nanometer - a billionth of a meter - to more than three nanometers. Nanotubes can also vary by the angle at which they are twisted. This is known as the chiral angle, and a useful analogy is a roll of gift-wrap paper. If the roll is rewound carefully, there is no overhang on either end. However, if the roll wound at an odd angle, excess paper hangs off at one end.

The chiral angle of nanotubes can vary from 0 degrees (no paper hanging off the roll) to 30 degrees, and tubes with different chiralities and diameters can have very different physical properties. Some are metals for instance and others are not.

In developing his computational model of nanotube breaking patterns, Yakobson consider four critical values: load level, load duration, temperature and chirality.

"The breaking mechanism for a particular nanotube depends to a great extent on its intrinsic twist called chirality," said co-author Traian Dumitrica, a former Rice postdoctoral researcher who is now assistant professor of mechanical engineering at the University of Minnesota. "Yet, temperature still influences the outcome. We were able to summarize the intricate dependence on parameters in a map , which stands as a striking example for the predictive power of simulations in materials science research."

Source: Rice University

Explore further: A stretchy mesh heater for sore muscles

Related Stories

Graphene oxide biodegrades with help of human enzymes

Jun 02, 2015

Graphene Flagship researchers show how graphene oxide suspended in water biodegrades in a reaction catalysed by a human enzyme, with the effectiveness of the breakdown dependent on the colloidal stability ...

Kateeva coating could finally give us bendable displays

Aug 15, 2014

A new startup based in Menlo Park, California called Kateeva might have solved one of the problems that is keeping manufacturers from selling us portable devices with bendable displays. They've developed ...

Recommended for you

A stretchy mesh heater for sore muscles

Jul 03, 2015

If you suffer from chronic muscle pain a doctor will likely recommend for you to apply heat to the injury. But how do you effectively wrap that heat around a joint? Korean Scientists at the Center for Nanoparticle ...

Polymer mold makes perfect silicon nanostructures

Jul 03, 2015

Using molds to shape things is as old as humanity. In the Bronze Age, the copper-tin alloy was melted and cast into weapons in ceramic molds. Today, injection and extrusion molding shape hot liquids into ...

Better memory with faster lasers

Jul 02, 2015

DVDs and Blu-ray disks contain so-called phase-change materials that morph from one atomic state to another after being struck with pulses of laser light, with data "recorded" in those two atomic states. ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.