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 Cement as a climate killer: Using industrial residues to produce carbon neutral alternatives
20.05.2019 | Martin-Luther-Universität Halle-Wittenberg

nachricht Discovering unusual structures from exception using big data and machine learning techniques
17.05.2019 | Science China Press

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Self-repairing batteries

UTokyo engineers develop a way to create high-capacity long-life batteries

Engineers at the University of Tokyo continually pioneer new ways to improve battery technology. Professor Atsuo Yamada and his team recently developed a...

Im Focus: Quantum Cloud Computing with Self-Check

With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. The research groups led by Rainer Blatt and Peter Zoller report in the journal Nature how they simulated particle physics phenomena on 20 quantum bits and how the quantum simulator self-verified the result for the first time.

Many scientists are currently working on investigating how quantum advantage can be exploited on hardware already available today. Three years ago, physicists...

Im Focus: Accelerating quantum technologies with materials processing at the atomic scale

'Quantum technologies' utilise the unique phenomena of quantum superposition and entanglement to encode and process information, with potentially profound benefits to a wide range of information technologies from communications to sensing and computing.

However a major challenge in developing these technologies is that the quantum phenomena are very fragile, and only a handful of physical systems have been...

Im Focus: A step towards probabilistic computing

Working group led by physicist Professor Ulrich Nowak at the University of Konstanz, in collaboration with a team of physicists from Johannes Gutenberg University Mainz, demonstrates how skyrmions can be used for the computer concepts of the future

When it comes to performing a calculation destined to arrive at an exact result, humans are hopelessly inferior to the computer. In other areas, humans are...

Im Focus: Recording embryonic development

Scientists develop a molecular recording tool that enables in vivo lineage tracing of embryonic cells

The beginning of new life starts with a fascinating process: A single cell gives rise to progenitor cells that eventually differentiate into the three germ...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Cement as a climate killer: Using industrial residues to produce carbon neutral alternatives

20.05.2019 | Materials Sciences

When bees are freezing

20.05.2019 | Life Sciences

Machine learning speeds modeling of experiments aimed at capturing fusion energy on Earth

20.05.2019 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>