Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Why Nanolayers Buckle when Microbeams Bend

19.12.2005


German-Austrian-French research team uses a hundred-nanometre wide x-ray beam to observe how nanolayers buckle in bent high-tech carbon fibres


An x-ray beam just 100 nanometres in width functions as a "nano-magnifier" to explore, in detail, defects and changes in carbon fibres. Image: Max Planck Institute of Colloids and Interfaces



Scientists from the Max Planck Institute of Colloids and Interfaces, working together with colleagues from the University of Vienna and the European Synchrotron Radiation Facility in Grenoble, France have made the first-ever observations of nanocrystallite buckling in carbon fibres. The results indicate that missing cross-links between the individual carbon layers are responsible for the buckling. (Physical Review Letters, November 25, 2005). Such a finding has implications for the way high-tech carbon materials are produced.

High-strength, ultra-light and elastic carbon materials are commonly used in high-performance sports goods and modern aerospace technology - for example in tennis rackets, racing tyres, heat shields and even guitars. Carbon fibres are only a few micrometres thick and mainly used to mechanically reinforce other materials, like polymers, metals, and ceramics. In tension, these kinds of fibres are stronger than most other known materials. However, compression applied parallel to the fibre axis can cause the buckling of nanoscale carbon layers - comparable to the buckling of a long, thin rod under compressive load.


In a novel physical experiment at the European Synchrotron Radiation Facility in Grenoble, researchers from Potsdam, Germany and Vienna have threaded both ends of micrometre thick carbon fibres through thin hollow needles in order to form fibre loops. The fibres are stretched on the outside of the loop and compressed on the inside. In-between there is a neutral zone, as we might find in a bent beam. By tugging on the ends of the fibres, the scientists were able to adjust the loop’s radius, and thus also the mechanical load in the tensile and the compression region. Oskar Paris from the Max Planck Institute of Colloids and Interfaces explains that "what is unique about the experiment is that we can make observations at many length-scales and thus gather evidence about the secret of ‘nano-buckling’. Using a 100-nanometre wide x-ray beam, we can scan the differently distorted regions along the cross-section of the fibre. Our nano-magnifier - the diffraction of the x-ray beam -allows us to measure the local strains of the only some nanometres thick carbon layers, as well as their orientation with respect to the fibre axis."

High-tech carbon fibres are made of graphite-like carbon sheets with strong covalent atomic bonding within the sheets, and weak Van der Waals bonding between them. Almost all the physical properties - and particularly mechanical behaviour - of these materials depend on their orientation. Their tensile stiffness is as much as five times higher than that of steel, and their specific tensile strength can overcome that of steel by a factor of ten. Under compression, however, the fibres can fail. Here, the mechanical behaviour is determined by mechanical instability - carbon layers buckling at the nanoscale - in addition to the shearing of single carbon layers.

In spite of this, some carbon fibres exhibit astoundingly good shear properties. In these cases, "nano-buckling" is rarely observed - which suggests the existence of a substantial number of strong cross-links between the carbon layers. Herwig Peterlik from the University of Vienna explains that "if we could reinforce the usually very weak connections between the carbon layers in a controlled way using this kind of covalent cross-links, then in addition to carbon fibres, the highly-vaunted new carbon nanotubes would be almost ready to make the strongest ropes in the world."

This has been possible very recently with electron irradiation, which requires however a high expenditure of money and energy. The high price is also the major reason why carbon fibres, which are relatively cheap to produce, are not easily replaced by modern nanotubes. The question why these valuable cross-links occur only in some carbon fibres, while others buckle, still remains unclear.
[EC]

Original work:

Dieter Loidl, Oskar Paris, Manfred Burghammer, Christian Riekel and Herwig Peterlik
Direct observation of nanocrystallite buckling in carbon fibers under bending load
Physical Review Letters 95, 225501 (2005), November 2005

Dr. Andreas Trepte | EurekAlert!
Further information:
http://www.mpg.de

More articles from Physics and Astronomy:

nachricht SF State astronomer searches for signs of life on Wolf 1061 exoplanet
20.01.2017 | San Francisco State University

nachricht Molecule flash mob
19.01.2017 | Technische Universität Wien

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

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...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | 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

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>