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


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

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.

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 On the Road to Artificial Photosynthesis
26.09.2014 | DOE/Lawrence Berkeley National Laboratory

nachricht NanoMaster Project Optimises Processes and Up-Scaling for Graphene Delivery
26.09.2014 | NetComposites Ltd

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Anzeige

Anzeige

Event News

BrainScaleS Conference: From Neurobiology to New Computer Architectures

25.09.2014 | Event News

17th European Health Forum Gastein: “Electing Health – The Europe We Want”

23.09.2014 | Event News

Future questions regarding data processing

22.09.2014 | Event News

 
Latest News

High-speed drug screen

01.10.2014 | Medical Engineering

Got Power?

01.10.2014 | Power and Electrical Engineering

The cultural side of science communication

01.10.2014 | Science Education

VideoLinks
B2B-VideoLinks
More VideoLinks >>>