New York NY (SPX) Dec 01, 2010
In 2008, experiments at The Fu Foundation School of Engineering and Applied Science at Columbia University established pure graphene, a single layer of graphite only one atom thick, as the strongest material known to mankind.
This raised a question for Chris Marianetti, Assistant Professor in Columbia Engineering's Department of Applied Physics and Applied Mathematics: how and why does graphene break?
Using quantum theory and supercomputers, Marianetti has revealed the mechanisms of mechanical failure of pure graphene under tensile stress.
In a paper recently accepted for publication in the journal Physical Review Letters, he shows that, when graphene is subject to strain equal in all directions, it morphs into a new structure which is mechanically unstable.
Marianetti says this failure mechanism is a novel soft-mode phonon instability. A phonon is a collective vibrational mode of atoms within a crystal, similar to a wave in a liquid. The fact that a phonon becomes "soft" under tensile strain means that the system can lower its energy by distorting the atoms along the vibrational mode and transitioning to a new crystalline arrangement.
Under sufficient strain, graphene develops a particular soft-mode that causes the honeycomb arrangement of carbon atoms to be driven towards isolated hexagonal rings. This new crystal is structurally weaker, resulting in the mechanical failure of the graphene sheet.
"This is exciting on many different levels," Marianetti notes. "Soft modes were first recognized in the 1960s in the context of ferroelectric phase transitions, but they have never been directly linked to fracture.
"Typically, defects in a material will always cause failure to happen prematurely, but the pristine nature of graphene allows one to test our prediction. We have already outlined some interesting new experiments to directly observe our theoretical prediction of the soft mode."
Marianetti added that this is the first time a soft optical phonon has ever been linked to mechanical failure and that therefore it is likely that this novel failure mechanism is not exclusive to graphene but may be prevalent in other very thin materials.
"With nanotechnology becoming increasingly ubiquitous, understanding the nature of mechanical behavior in low dimensional systems such as graphene is of great importance. We think strain may be a means to engineer the properties of graphene, and therefore understanding its limits is critical." The research was funded by the National Science Foundation.
Marianetti's research interests lie in the use of classical and quantum mechanics to model the behavior of materials at the atomic scale.
In particular, he is focused on applying these techniques to materials with potential for energy storage and conversion. Current applications in his research program range from nuclear materials such as plutonium to rechargeable battery materials such as cobalt oxides.
Share This Article With Planet Earth
Space Technology News - Applications and Research
New Technology Gives On-Site Assessments In Archaeology
Durham NC (SPX) Nov 18, 2010
The ability to tell the difference between crystals that formed naturally and those formed by human activity can be important to archaeologists in the field. This can be a crucial bit of information in determining the ancient activities that took place at a site, yet archaeologists often wait for months for the results of laboratory tests. Now, however, an international team of physicists, ... read more
German scientist eyes gold mine in rare earths recycling|
Apple's iPad has real Xmas rival in Samsung's Galaxy tablet
Columbia Engineering Team Discovers Graphene Weakness
Estonia's rare earth break China's market grip
Codan Receives JITC Certification For 2110 HF Manpack
Northrop Grumman Bids for Marine Corps Common Aviation CnC
DSP Satellite System Celebrates 40 Years
ManTech Awarded US Army Contract To Provide ECCS In Afghanistan
Hylas-1 In Orbit Brings Europe Broadband From Space
Ariane rocket puts telecom satellites into orbit
45th Space Wing Launches NRO Satellite
FAA issues private spacecraft permit
World-Leading Spatial Experts Meet In Sydney
Space Ministers Emphasise Priority To Deliver Galileo And GMES
New Simulator Offers Ability To Record And Replay GLONASS And GPS
Russia To Launch New Generation Satellite In 2013
Brazil eyes Boeing, Airbus aviation market
NASA awards contracts for 'green' airliner
Should Airplanes Look Like Birds
Simple Oscillating Flexible Wings Viable For MAVs
Manufacturing Made To Measure Atomic-Scale Electrodes
Short Light Pulses Will Enable Ultrafast Data Transfer Within Computer Chips
Chaogates Hold Promise For The Semiconductor Industry
Caltech Physicists Demonstrate A Four-Fold Quantum Memory
Two New Earth Observation Missions Chosen For Further Study
Express Map Delivery From Space
GOES-13 Looks At Thanksgiving Travel Conditions
Imaging Science Offers New Opportunities For Interdisciplinary Collaboration
Tiny blood vessels show pollution, heart disease link
Construction halts on India's newest hill station
Conference urged to step up anti landmine drive
Australian firm to ship toxic waste to Denmark
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2010 - SpaceDaily. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement|