Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Heavier hydrogen on the atomic scale reduces friction

06.11.2007
Scientists may be one step closer to understanding the atomic forces that cause friction, thanks to a recently published study by researchers from the University of Pennsylvania, the University of Houston and the U.S. Department of Energy's Argonne National Laboratory.

The research, led by Robert Carpick of the University of Pennsylvania, found a significant difference in friction exhibited by diamond surfaces that had been coated with different isotopes of hydrogen and then rubbed against a small carbon-coated tip.

Scientists lack a comprehensive model of friction on the nanoscale and only generally grasp its atomic-level causes, which range from local chemical reactions to electronic interactions to phononic, or vibrational, resonances.

To investigate the latter, Argonne scientist Anirudha Sumant and his colleagues used single-crystal diamond surfaces coated with layers of either atomic hydrogen or deuterium, a hydrogen atom with an extra neutron. The deuterium-terminated diamonds had lower friction forces because of their lower vibrational frequencies, an observation that Sumant attributed to that isotope's larger mass. They have also observed same trend on a silicon substrate, which is structurally similar to that of diamond.

Previous attempts to make hydrogen-terminated diamond surfaces relied on the use of plasmas, which tended to etch the material.

"When you're looking at such a small isotopic effect, an objectively tiny change in the mass, you have to be absolutely sure that there are no other complicating effects caused by chemical or electronic interferences or by small topographic variations," Sumant said. "The nanoscale roughening of the diamond surface from the ion bombardment during the hydrogen or deuterium termination process, even though it was at very low level, remained one of our principal concerns."

Sumant and his collaborators had looked at a number of other ways to try to avoid etching, even going to such lengths as to soak the films in olive oil before applying the hydrogen layers. However, no method had provided a smooth, defect-free hydrogen layer with good coverage that would avoid generating background noise, he said.

However, while performing work at the University of Wisconsin-Madison, Sumant developed a system for depositing diamond thin films. The technique, called hot filament chemical vapor deposition, involves the heating of a tungsten filament (like those found in incandescent light bulbs) to over 2000 degrees Celsius.

If the diamond film is exposed to a flow of molecular hydrogen while sitting within a centimeter of the hot filament, the heat will cause the molecular hydrogen to break down into atomic hydrogen, which will react with the film's surface to create a perfectly smooth layer. Since this method does not require the use of plasma, there is no danger of ion-induced etching.

"We've proved that this is a gentler method of terminating a diamond surface," Sumant said.

Sumant said that he hopes to use the knowledge gained from the experiment to eventually discover a way to manipulate the friction of surfaces on the atomic level. Such a result would prove immensely valuable to the development of nanoelectromechanical systems, or NEMS, based on diamonds, one of Sumant's primary research interests at Argonne's Center for Nanoscale Materials.

The paper, "Nanoscale Friction Varied by Isotopic Shifting of Surface Vibrational Frequencies," appears in the November 2 issue of Science.

The research was supported by the National Science Foundation, an NSF Graduate Research Fellowship, the Air Force Office of Scientific Research and the Department of Energy's Office of Science, Office of Basic Energy Sciences.

About The Center for Nanoscale Materials

The Center for Nanoscale Materials at Argonne National Laboratory is a joint partnership between the U.S. Department of Energy (DOE) and the State of Illinois, as part of DOE'S Nanoscale Science Research Center program. The CNM serves as a user-based center, providing tools and infrastructure for nanoscience and nanotechnology research. The CNM's mission includes supporting basic research and the development of advanced instrumentation that will help generate new scientific insights and create new materials with novel properties. The existence of the CNM, with its centralized facilities, controlled environments, technical support, and scientific staff, enabled researchers to excel and significantly extend their reach.

Argonne National Laboratory, a renowned R&D center, brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America 's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

Steve McGregor | EurekAlert!
Further information:
http://www.anl.gov

More articles from Studies and Analyses:

nachricht Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

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

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Global study of world's beaches shows threat to protected areas

19.07.2018 | Earth Sciences

New creepy, crawly search and rescue robot developed at Ben-Gurion U

19.07.2018 | Power and Electrical Engineering

Metal too 'gummy' to cut? Draw on it with a Sharpie or glue stick, science says

19.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>