Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Diamonds in the crush

14.08.2014

Theoretical simulations reveal how nanoscale lubricating systems can ease friction between surfaces cMain Contentoated with diamond-like carbon

Diamond-like-carbon (DLC) coatings are an innovative technology, exhibiting the twin properties of mechanical toughness and ultralow friction. These features, which are desirable in abrasive environments, have led to the widespread adoption of DLC films in microelectromechanical systems, such as hard disk drives.


Device longevity can be improved through use of computer models that optimize the friction properties of diamond-like coatings used in hard disk drives.

© Janka Dharmasena/iStock/Thinkstock

But because these coatings contain amorphous carbon atoms that produce rough, nanoscale textures, it is difficult to optimize their friction properties using classical theories designed for macroscopic objects.

By performing atom-level simulations of nanoscale friction, Ling Dai and co-workers from the A*STAR Institute of High Performance Computing in Singapore have now uncovered critical clues for designing better systems to lubricate and protect DLC coatings (1).

Perfluoropolyether (PFPE) is a Teflon-like polymer that is commonly sandwiched between DLC-coated substrates to reduce friction and protect against damage. Understanding the friction mechanisms between these ultrathin films is tricky; these materials have contrasting hard and soft mechanical properties, and the sandwich arrangement obscures any direct observation of atomic structure and activity.

To better understand how nanoscale lubrication works in microdevices, the researchers constructed an atomic DLC–PFPE–DLC triple layer using a three-dimensional computer modeling program. They set one DLC slab as a substrate and the other as a ‘slider’.

They then used molecular dynamics techniques to simulate how the lube film responds when the slider moves. However, it was challenging to describe the atomic interactions in this complex material, and so Dai’s team developed hybrid computations that combined several potential energy expressions to replicate the many-body forces in this system.

Simulating frictional motions at different speeds and PFPE film thicknesses revealed that the lubricating film behaves as a solid — the polymer retained its shape without deforming from internal shearing. However, the lubricating film displayed two distinct and competitive modes of motion at an interface: a ‘stick–slide’ action that produced jerky, stepwise displacements, and a continuous motion that caused the film to slide with fluctuating velocities.

The team’s analysis showed that these two types of motions switched on or off depending on adhesion factors, such as thermal vibrations and the interfacial roughness.

After mapping the local friction forces along the sliding interfaces, the researchers discovered a way to link the law describing macroscopic friction to the nanoscale using a simple mathematical modification — a finding with practical importance for the surface engineering of DLC coatings.

“Because our model closely resembles the materials used in industrial applications, this work can serve as a guide for future experimental developments,” says Dai.

The A*STAR-affiliated researchers contributing to this research are from the Institute of High Performance Computing

Reference

(1) Dai, L., Sorkin, V., Sha, Z. D., Pei, Q. X., Branico, P. S. & Zhang, Y. W. Molecular dynamics simulations on the frictional behavior of a perfluoropolyether film sandwiched between diamond-like-carbon coatings. Langmuir 30, 1573–1579 (2014).

A*STAR Research | Research SEA News
Further information:
http://www.research.a-star.edu.sg/research/7016
http://www.researchsea.com

More articles from Materials Sciences:

nachricht An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

nachricht Treated carbon pulls radioactive elements from water
20.01.2017 | Rice 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: 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 >>>