Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Gold surfaces repair themselves at room temperature

19.10.2011
Micromechanical systems and electric switches are based on smallest sliding contacts. They only work without loss of energy or material, if the surfaces are very smooth and without any defects.

So far, little has been understood about the underlying atomic-scale principles. In cooperation with researchers at the universities of Münster and Gießen as well as the Fraunhofer Institute for Mechanics of Materials IWM in Freiburg, scientists at the INM – Leibniz Institute for New Materials were able to show that on atomic scale gold surfaces smoothen out by themselves at room temperature. In their publication in Physical Review Letters, they reveal that this effect disappears at low temperatures.

So far, it has been assumed that perfect sliding works the better the more rigid the surface is. On the atomic scale this could mean freezing lattice vibrations in the crystal at low temperatures below -100°C; where the atoms hardly move. Against expectation, smooth sliding on gold surfaces is not quite possible at these temperatures, but, however, at room temperature. The scientists explain this phenomenon with the diffusion of the gold atoms: If they are able to move freely on the surface, the gold atoms migrate into defects on the surfaces and remove holes and bumps. The diffusion effectively stops below -100°C.

"Imagine a record player whose needle made from rubber moves over a wax plate. If the wax is hard, wax pieces will be scratched out and, after a while, the needle pushes a pile of wax, which can only be surmounted by the needle after it bends strongly", explains Roland Bennewitz, Head of the Program Division "Nanotribology". If the temperature rises, the wax melts and the needle leaves no more traces in the wax. In fact, the liquid wax removes holes and bumps at once, and the needle slides uniformly through the wax.

A similar process occurs on the gold surfaces. Although they do not melt at room temperature, the diffusion of the gold atoms is so strong that smallest asperities on the nanoscale are removed at once. The regular structure of the surface is preserved.

Experiments were performed by atomic force microscopy (AFM). A thin needle slides forth and back on the gold surface. The measured signal shows how strong the needle bends in contact. On a crystalline surface, the needle "jumps" regularly from atom group to atom group – the scientists measure a stable so-called stick-slip pattern. In the event of defects, such as the accumulated gold atoms, the needle bends stronger and the stick-slip pattern will be broken.

In their research, the scientists also employed atomistic modelling on the computer. Here, they were able to reproduce the stick-slip pattern for the scanning of the gold surface with gold and nickel needles. With a 3D simulation, they were also able to show how gold atoms accumulate at low temperatures. The accumulated gold atoms are attracted by the needle like a liquid into a capillary.

Original publication:
Nitya Nand Gosvami, Michael Feldmann, Joël Peguiron, Michael Moseler, André Schirmeisen, and Roland Bennewitz:
„Ageing of a Microscopic Sliding Gold Contact at Low Temperatures“
Physical Review Letters 107, 144303 (2011)
DOI: 10.1103/PhysRevLett.107.144303
Contact:
Prof. Dr. Roland Bennewitz
INM - Leibniz-Institut für Neue Materialien gGmbH
Phone: (+49) 681 9300 213
Email: Roland.bennewitz@inm-gmbh.de
INM is focused on the research and development of materials – for today, tomorrow and the future. Chemists, physicists, biologists, materials and engineering scientists shape the work at INM. From molecule to pilot production, they follow the recurring questions: Which material properties are new, how can they be investigated and how can they be used in the future?

INM – Leibniz Institute for New Materials, situated in Saarbrücken/Germany, is an internationally leading centre for materials research. It is a scientific partner to national and international institutes and a provider of research and development for companies throughout the world. INM is an institute of the Scientific Association Gottfried Wilhelm Leibniz and employs around 190 collaborators. Its main research fields are Chemical Nanotechnology, Interface Materials, and Materials in Biology.

Dr. Carola Jung | idw
Further information:
http://www.inm-gmbh.de/
http://www.wgl.de/

More articles from Materials Sciences:

nachricht Machine learning methods provide new insights into organic-inorganic interfaces
04.08.2020 | Technische Universität Graz

nachricht Unusual electron sharing found in cool crystal
31.07.2020 | Nagoya University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New Strategy Against Osteoporosis

An international research team has found a new approach that may be able to reduce bone loss in osteoporosis and maintain bone health.

Osteoporosis is the most common age-related bone disease which affects hundreds of millions of individuals worldwide. It is estimated that one in three women...

Im Focus: AI & single-cell genomics

New software predicts cell fate

Traditional single-cell sequencing methods help to reveal insights about cellular differences and functions - but they do this with static snapshots only...

Im Focus: TU Graz Researchers synthesize nanoparticles tailored for special applications

“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.

Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...

Im Focus: Tailored light inspired by nature

An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.

Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...

Im Focus: NYUAD astrophysicist investigates the possibility of life below the surface of Mars

  • A rover expected to explore below the surface of Mars in 2022 has the potential to provide more insights
  • The findings published in Scientific Reports, Springer Nature suggests the presence of traces of water on Mars, raising the question of the possibility of a life-supporting environment

Although no life has been detected on the Martian surface, a new study from astrophysicist and research scientist at the Center for Space Science at NYU Abu...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“Conference on Laser Polishing – LaP 2020”: The final touches for surfaces

23.07.2020 | Event News

Conference radar for cybersecurity

21.07.2020 | Event News

Contact Tracing Apps against COVID-19: German National Academy Leopoldina hosts international virtual panel discussion

07.07.2020 | Event News

 
Latest News

Manifestation of quantum distance in flat band materials

05.08.2020 | Physics and Astronomy

Discovery shows promise for treating Huntington's Disease

05.08.2020 | Health and Medicine

Rock debris protects glaciers from climate change more than previously known

05.08.2020 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>