Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Materials break, then remake, bonds to build strength

05.08.2013
Microscopic tears in a new kind of man-made material may actually help the substance bulk up like a bodybuilder at the gym.

"We've shown how normally destructive mechanical forces can be channeled to bring about stronger materials," said Duke chemist Steve Craig, who led the research. "The material responses are like Silly Putty transforming into a solid as stiff as the cap of a pen or a runny liquid transforming into soft Jell-O."

Scientists could one day use the stress-induced strength from these new materials to make better fluids such as engine oil, or soft-structure substances such as artificial heart valves. Materials like this wear out over time because of the repeated mechanical forces they experience during use. But Craig said if a material had properties to slow down its destruction, it would greatly improve quality of life.

It is the first time scientists have used force-induced chemistry within a material to make it stronger in response to stress. The results appear Monday, Aug. 5, 2013, in Nature Chemistry.

In past experiments, Craig's team has gripped and tugged on individual molecules of a material to see how it reacted at the atomic level. Now, the scientists have scaled up the material to contort it macroscopically and see how it responds.

Craig said the response is similar to what happens when a person lifts weights. Those individual stresses trigger biological processes in the muscles that ultimately increase the person's strength.

"It's the same idea chemists would like to use for synthetic materials," he said. "Everyday materials can wear out with repeated stress. Think of your favorite t-shirt or even the oil in your car engine. Wear after wear, fire after fire, these materials break down."

The new man-made materials Craig's team is making have characteristics already in place so that when a stress triggers a bond to break, it breaks in a way that triggers a subsequent reaction forcing the busted atomic bonds to reform new ones.

"It's like snapping a string. But before the string snaps, sites along it form so that when it breaks it can become tied to another string," Craig said.

The scientists first stressed one of the test materials by pulsing high-intensity sound waves through them. The sound waves create bubbles, which typically collapse and break the bonds of the molecules in the material. The forces breaking atoms in the new materials, however, triggered the formation of new bonds, which strengthened the liquid by transforming it into a soft Jell-O consistency.

To test the strength-building ability of a Silly-Putty-like material, the team used a twin-screw extruder, which is as damaging as it sounds. The machine bores two screws into a material and pulls the material through it, destroying some of the material's molecular bonds. Here too, the synthetic material formed more new bonds than those destroyed, becoming much more solid in structure and stronger.

Craig said one drawback to the new materials is that forces deform the material's initial structure. It is stronger at the end, but is not the same shape. The team now plans to create synthetic materials that can repair themselves after stress and retain their original shape, he said.

The team would also like to engineer the material to respond faster. "At this point it takes minutes for the strengthening reactions to start changing the material," Craig said. "We could see it happening as quickly as milliseconds."

The research received funding from the Army Research Office, with additional support from the National Science Foundation.

"Mechanochemical Strengthening of a Synthetic Polymer in Response to Typically Destructive Shear Forces," Black Ramirez, A. et. al. Nature Chemistry, August 2013.

DOI: 10.1038/nchem.1720. Once the paper is published electronically, the DOI can be used to retrieve the abstract and full text (abstracts are available to everyone, full text only to subscribers) by adding it to the following url: http://dx.doi.org/.

Keith Lawrence | EurekAlert!
Further information:
http://www.duke.edu

More articles from Materials Sciences:

nachricht Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously
17.01.2017 | Sonderforschungsbereich 668

nachricht Manchester scientists tie the tightest knot ever achieved
13.01.2017 | University of Manchester

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

How gut bacteria can make us ill

18.01.2017 | Life Sciences

On track to heal leukaemia

18.01.2017 | Health and Medicine

Water - as the underlying driver of the Earth’s carbon cycle

17.01.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>