Navigation Links
University of Pennsylvania engineers reveal what makes diamonds slippery at the nanoscale
Date:6/23/2008

PHILADELPHIA - They call diamonds "ice," and not just because they sparkle. Engineers and physicists have long studied diamond because even though the material is as hard as an ice ball to the head, diamond slips and slides with remarkably low friction, making it an ideal material or coating for seals, high performance tools and high-tech moving parts.

Robert Carpick, associate professor in the Department of Mechanical Engineering and Applied Mechanics at the University of Pennsylvania, and his group led a collaboration with researchers from Argonne National Laboratories, the University of Wisconsin-Madison and the University of Florida to determine what makes diamond films such slippery customers, settling a debate on the scientific origin of its properties and providing new knowledge that will help create the next generation of super low friction materials.

The Penn experiments, the first study of diamond friction convincingly supported by spectroscopy, looked at two of the main hypotheses posited for years as to why diamonds demonstrate such low friction and wear properties. Using a highly specialized technique know as photoelectron emission microscopy, or PEEM, the study reveals that this slippery behavior comes from passivation of atomic bonds at the diamond surface that were broken during sliding and not from the diamond turning into its more stable form, graphite. The bonds are passivated by dissociative adsorption of water molecules from the surrounding environment. The researchers also found that friction increases dramatically if there is not enough water vapor in the environment.

Some previous explanations for the source of diamond's super low friction and wear assumed that the friction between sliding diamond surfaces imparted energy to the material, converting diamond into graphite, itself a lubricating material. However, until this study no detailed spectroscopic tests had ever been performed to determine the legitimacy of this hypothesis. The PEEM instrument, part of the Advanced Light Source at Lawrence Berkeley National Laboratory, allowed the group to image and identify the chemical changes on the diamond surface that occurred during the sliding experiment.

The team tested a thin film form of diamond known as ultrananocrystalline diamond and found super low friction (a friction coefficient ~0.01, which is more slippery than typical ice) and low wear, even in extremely dry conditions, (relative humidity ~1.0%). Using a microtribometer, a precise friction tester, and Xray photoelectron emission microscopy, a spatially resolved X-ray spectroscopy technique, they examined wear tracks produced by sliding ultrananocrystalline diamond surfaces together at different relative humidities and loads. They found no detectable formation of graphite and just a small amount of carbon re-bonded from diamond to amorphous carbon. However, oxygen was present on the worn part of the surface, indicating that bonds broken during sliding were eventually passivated by the water molecules in the environment.

Already used in industry as a mechanical seal coating to reduce wear and improve performance and also as a super-hard coating for high-performance cutting tools, this work could help lead to increased use of diamond films in machines and devices to increase service life, prevent wear of parts and save energy wasted by friction.


'/>"/>

Contact: Jordan Reese
jreese@upenn.edu
215-573-6604
University of Pennsylvania
Source:Eurekalert

Related biology technology :

1. GlaxoSmithKline Recognizes University of Michigans Dr. Daniel F. Hayes as the First Recipient of the Gianni Bonadonna Breast Cancer Award
2. BioMarin Licenses Technology From Leading Cystic Fibrosis Research Laboratory at the University of California, San Francisco
3. Microchip Biotechnologies, Inc. Secures Exclusive License to Use New University of Alberta Technology for Developing Microfluidic Devices
4. Alliance for Medical Devices, Instrumentation and Diagnostics formed between Fraunhofer Center for Manufacturing Innovation and Boston University
5. The University of Nottingham in the British Midlands Announces Development of Possible Hepatitis C Vaccine
6. University of Leicester scientists discover technique to help friendly bacteria
7. MichBio Announces Student Career Day at Michigan State University
8. Dr. Thomas Van Dyke Renowned Boston University Professor Joins Imagenetixs Medical Advisory Board
9. University HealthSystem Consortium Chooses SciQuest to Optimize Medical Research Procurement
10. Helix Biopharma announces addition of University of Arizona professor Kenneth Hatch as new medical advisor
11. McGill University Purchases GenVaults Personal Archive System to Manage Rare Cancer Samples
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:9/20/2017)... (PRWEB) , ... September 20, ... ... (IPS), a leading global provider of engineering, architecture, project controls, construction management, ... prefabricated cleanrooms, today announced the unveiling of the iCON™ brand which represents ...
(Date:9/20/2017)... , ... September 20, 2017 ... ... published findings of a study examining the effects of exoskeleton-assisted walking on ... cord injury (SCI). The article, "Neuromechanical adaptations during a robotic powered exoskeleton ...
(Date:9/20/2017)... ... September 20, 2017 , ... ... molecular manufacturing and other transformative technologies, announced the winners for the 2017 Foresight ... other for Theory in nanotechnology/molecular manufacturing. , Established in 1993 and named in ...
(Date:9/19/2017)... ... 19, 2017 , ... The latest generation of the AutoBlock, ... prep for metals digestion—the addition of acids and reagents. The accessory fits any ... is ideal for any laboratory performing their own unique metals digestion method. ...
Breaking Biology Technology:
(Date:4/4/2017)... NEW YORK , April 4, 2017   ... solutions, today announced that the United States Patent and ... The patent broadly covers the linking of an iris ... the same transaction) and represents the company,s 45 th ... our latest patent is very timely given the multi-modal ...
(Date:3/30/2017)... LOS ANGELES , March 30, 2017  On ... Hack the Genome hackathon at ... This exciting two-day competition will focus on developing health ... experience. Hack the Genome is ... has been tremendous. The world,s largest companies in the ...
(Date:3/30/2017)... 30, 2017 Trends, opportunities and forecast in ... by technology (fingerprint, AFIS, iris recognition, facial recognition, hand ... by end use industry (government and law enforcement, commercial ... banking, and others), and by region ( North ... Asia Pacific , and the Rest of ...
Breaking Biology News(10 mins):